Synthesis of annulated arenes and heteroarenes involving lewis acid-mediated regioselective annulation of unsymmetrical 1,2-(Diaryl/ diheteroarylmethine)dipivalates

Article abstract of DOI:10.1021/jo301410w

A ZnBr₂-mediated regioselective annulation of unsymmetrical 1,2-diarylmethinedipivalates in DCM at room temperature led to the formation of annulated arenes and heteroarenes. The annulation of the dipivalate proceeds through the intermediacy of

Full text of DOI:10.1021/jo301410w

Article
pubs.acs.org/joc
Synthesis of Annulated Arenes and Heteroarenes Involving Lewis
Acid-Mediated Regioselective Annulation of Unsymmetrical 1,2-
(Diaryl/diheteroarylmethine)dipivalates
Ramakrishnan Sivasakthikumaran, Meganathan Nandakumar, and Arasambattu K. Mohanakrishnan*
Department of Organic Chemistry, School of Chemistry, University of Madras, Guindy Campus, Chennai 600 025, Tamil Nadu, India
S
* Supporting Information
ABSTRACT: A ZnBr2-mediated regioselective annulation of
unsymmetrical 1,2-diarylmethinedipivalates in DCM at room
temperature led to the formation of annulated arenes and
heteroarenes. The annulation of the dipivalate proceeds
through the intermediacy of benzylic carbocations followed
by intramolecular cyclization and subsequent aromatization to
give the annulated products. The annulation methodology is
highly efficient for the syntheses of anthracene as well as naphtho[b]thiophene analogues.
arenes under super electrophilic conditions.19 Kuninobu and
co-workers achieved the synthesis of anthracenes and naphtho-
INTRODUCTION
■
Traditionally, the Friedel−Crafts alkylation has been labeled as
[b]thiophenes through indium triflate-mediated cycloaromati-
synthetically problematic, since controlling the reaction to the
zation reaction.20 In further continuation of our interest on
monoalkylation stage was thought to be difficult.1 However, the
synthesis of π-conjugated heterocycles involving Lewis-acids,21
Friedel−Crafts alkylation/cyclization using mild Lewis acid has
been gaining momentum.2 Apart from the first report of Beller
we report herein our detailed study on synthesis of anthracene
and co-workers3 on Lewis acid-mediated arylation of benzylic
and naptho[b]thiophene analogues involving regioselective
annulation of unsymmetrical diarylmethine dipivalates 1
acetates, a plethora of controlled Friedel−Crafts alkylation
employing mild Lewis acids have been achieved.4 Recently, the
(Scheme 1).
Lewis acid-mediated domino reaction has been successfully
Scheme 1. Synthesis of Annulated Arenes and Heteroarenes
applied for the synthesis of wide variety of π-conjugated
heterocycles.5
Anthracene and its derivatives, the most important class of
polycyclic aromatic compounds,6 have been prepared via
Friedel−Crafts reaction,1 flash vacuum pyrolysis,7 cyclodehy-
dration,8 Lewis acid-induced cyclization of diarylmethanes,9
transition metal-mediated homologation10 and so on. Among
the polyaromatic compounds, anthracene and its derivatives are
regarded as an important class of functional material for
optoelectronic device fabrication.11 In recent times, the
anthracene derivatives have been widely explored in
OLEDs,12 molecular switches13 and other optical applica-
tions.14 Because of its low electronic band gap and strong blue
fluorescence, they have been extensively used as fluorescent
chromophores in the construction of chemosensors for many
applications.15 It has been confirmed that the incorporation of
anthracene units as pendant groups led to the formation of
films with excellent optical quality.16 Hence, there is plenty of
demand for the synthesis of anthracene analogues with good
solubility to further explore their optoelectronic device
applications.
RESULTS AND DISCUSSION
■
The required diarylmethine dipivalates 5a−d were conveniently
prepared from 1,3-disubstituted isobenzofuran (IBF) deriva-
tives 3a−d.22 Lead tetraacetate (LTA)-mediated oxidative
cleavage23 of 3a−d led to the diketones 4a−d, which upon
NaBH4 reduction followed by subsequent pivaloylation
furnished benzylic dipivalates 5a−d as thick liquids (Scheme
2). The interaction of pivalate ester 5a with triflic acid/ZnBr2 as
Recently, Liu and co-workers achieved the synthesis of 9-
arylanthracenes17 and indenes18 involving either Bronsted acid
or Lewis acid-catalyzed cyclization of symmetrical aryldiace-
tates. Very recently, an efficient synthesis of anthracene
derivatives is realized via interaction of phthalaldehyde with
Received: July 26, 2012
Published: September 13, 2012
© 2012 American Chemical Society
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during the interaction of unsymmetrical dipivalates 5b−d with
Lewis acids as well as Bronsted acids.
Scheme 2. Annulation of Benzylic Dipivalates 5a−d
To rationalize the regioselective formation of annulated
heterocycles 6b−d, stabilization energies of benzylic carboca-
tions 8a−e and 9a−e were calculated using Gaussian 09
program (package: B3LYP/6-31G* basis set). From the
calculated values (Scheme 3), it is clear that the carbocation
Scheme 3. Mechanistic Rational for Benzo[b]thiophenes
6a−d
catalyst in DCM at room temperature for 30 min led to the
formation of naphtho[b]thiophene 6a and anthracene 7a as an
inseparable mixture (1:1, confirmed by 1H NMR). Under
identical conditions, to our delight, the reaction of pivalate
esters 5b−d with triflic acid/ZnBr2 as catalyst led to the
formation of naphtho[b]thiophenes 6b−d as exclusive
products.
Next, as a representative case, the annulation of 5b was
performed using 20 mol % of different Lewis acids/Bronsted
acids, and the results obtained are presented in Table 1. The
formation is more favored at 2-thienylmethyl position
compared to the benzyl, p-tolylmethyl, p-anisylmethyl and p-
chlorophenylmethyl positions. In the case of dipivalate 5b−d,
the highly stabilized thiophenylmethyl carbocations 8b−d upon
isomerization led to the formation of respective arylmethyl
carbocations 9b−d. The comparatively less stable benzylic
carbocations 9b−d underwent Friedel−Crafts type intra-
molecular cyclization at 3-position of thiophene followed by
elimination of pivalic acid to produce naphtho[b]thiophenes
6b−d. The formation of a mixture of naphtho[b]thiophene 6a
and anthracene 7a upon reaction of dipivalate 5a with Lewis
acid can be visualized through the Friedel−Crafts type
intramolecular cyclization of carbocations of 9a and 8a,
respectively. Among the carbocations 8a−d, the thiophenyl-
methyl carbocation 8a being highly reactive (−1438.7065 au)
underwent intramolecular cyclization to afford the anthracene
7a. However, the similar kind of cylization was not observed
with relatively more stable thiophenylmethyl carbocations 8b−
d.
Table 1. Effect of Catalyst (20 mol %) on Annulation of 5b
a
entry
catalyst
ZnBr2
condition (min)
yield
1
2
3
4
6
7
30
60
30
30
45
45
93
78
81
80
78
79
FeCl3
BF3.OEt2
CF3SO3H
Me3SO3H
CF3CO2H
Having achieved a facile regioselective annulation of benzylic
dipivalate 5b−d in the presence of ZnBr2, the preparation of
various types of unsymmetrical dipivalates was planned to study
their efficacy toward the synthesis of annulated arenes. Known
1,3-diarylbenzo[c]furans 3e−z, 10a−q and 14a−g22 could be
smoothly converted into the respective dipivalates 5e−z, 12a−
q and 16a−g using the similar sequence of reactions mentioned
in Scheme 2. The additional dipivalate 16h/16i was prepared
through m-CPBA-mediated oxidative cleavage of 1,3-
a
Isolated yields of 6b.
reaction was found to be successful with Lewis acids as well as
Bronsted acids. The maximum yield for naphtho[b]thiophene
6b could be obtained using 20 mol % of ZnBr2. It is noteworthy
to mention that as reported in the case of symmetrical benzylic
diacetates,17 we have not observed any dihydrofuran formation
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Scheme 4. Preparation of Unsymmetrical Benzylic Dipivalates
diarylbenzo[c]furan 14h/14i followed by reduction and
subsequent pivaloylation (Scheme 4).
annulated heterocycles 13l−q in 70−78% yields (entries 14−
17). The annulation of 3-benzo[b]thiophenyl dipivalates 12l−o
afforded benz-annelated dibenzothiophene analogues 13l−o.
However, in the case of 2-methyl-3-benzo[b]thiophenyl
dipivalate 12p/12q, a similar type of annulation is not possible
at the benzo[b]thiophene framework and hence led to the
formation of benzo[b]thiophenyl anthracene 13p/naphtho[b]-
thiophene 13q (entries 16, 17). Always, the yields of
heterocycles obtained with the benzo[b]thiophenyl dipivalates
12l−q were relatively less compared to either thiophene/arene
tethered dipivalates 5a−z/12a−k.
The unsymmetrical dibenzo[b]thiophenyl dipivalates 16a−f
upon reaction with 20 mol % ZnBr2 furnished naphth-
annelated dibenzothiophenes 17a−f in 51−87% yields (entries
18−20). The low yield of dibenzothiophene 17e isolated is due
to the competing annulation at naphthalene portion. The
annulation reaction with dibenzo[b]furanyl dipivalate 16g led
to the isolation of naphth-annelated dibenzofuran 17g and
naphtho[b]thiophene 17g′ in 48 and 23% yields, respectively.
Finally, the ZnBr2-mediated annulation of carbazole/triphenyl-
amine tethered dipivalate 16h/16i was found to be
unsuccessful. The usual work up followed by column
chromatographic separation did not afford any characterizable
product.
As expected the unsymmetrical aryl/heteroarylmethine
dipivalates 5e−z, 12a−q and 16a−g upon interaction with 20
mol % of ZnBr2 in DCM at room temperature for 30 min
furnished annulated products. The various types of annulated
arenes and heteroarenes obtained along with their yields are
described in Table 2. The reaction of dipivalates 5e−h with 20
mol % of ZnBr2 furnished respective 4-arylnaphtho[b]-
thiophenes 6e−h in 65−92% yields (entry 1). The moderate
yield of naphtho[b]thiophene 6e obtained from o-tolyl tethered
dipivalate 5e may be due to the steric crowding encountered
during intramolecular cyclization. The annulation of dipivalate
5i containing a 2-methoxy-1-naphthyl unit gave naphtho[b]-
thiophene 6i in 90% yield (entry 2). In the case of dipivalate
5j/5k tethered with 1-napthyl/2-methyl-1-naphthyl group, the
ZnBr2-mediated annulation led to the formation of benz-
annelated anthracene 6j, 6k (entry 3). However, the similar
reaction of dipivalate 5l/5m afforded the corresponding
naphtho[b]thiophene 6l/6m (entries 4, 5). As expected, the
unsymmetrical dipivalates 5n−w upon interaction with ZnBr2
led to the isolation of arylanthracenes 6n−w in excellent yields
(entries 6, 7). The nature of arylanthracenes 6n−w produced is
determined by the preferential formation of benzylic
carbocations followed by subsequent intramolecular cyclization
and aromatization. Obviously, the regioselective formation of
the benzylic carbocations is governed by the inductive effect of
the substituents present in the aryl unit.
The 2-methoxy-1-naphthyl and aryl based unsymmetrical
dipivalates 5x−z afforded 2-methoxy-1-napthylanthracenes 6x−
z in 88−95% yields as colorless solid (entry 8). In the case of 1-
naphthyl and aryl based unsymmetrical dipivalates 12a−g, the
reaction led to the formation of benz-annelated anthracenes
13a−g (entries 9, 10). The dipivalate 12h containing 2-
methoxy-1-naphthyl and 1-naphthyl rings furnished the
respective benz-annelated anthracene 13h in 86% yield (entry
11). However, the ZnBr2-mediated annulation of unsym-
metrical dipivalate 12i lacking a methoxy group at naphthalene
portion led to the formation of an inseparable mixture of benz-
annelated anthracenes 13i and 13i′ (entry 12). The 9,9-
dihexylfluorenyl unsymmetrical dipivalate 12j/12k underwent
smooth annulation at benzene portion to furnish the respective
fluorenyl anthracene 13j/13k (entry 13).
As representative case, the structures of annulated hetero-
cycles 6m, 13o and 17a were confirmed by single crystal X-ray
analyses.24
In summary, we have developed a simple and versatile
annulation protocol for the synthesis of anthracene and
naptho[b]thiophene analogues involving ZnBr2-mediated re-
gioselective annulation of unsymmetrical dipivalates. The
annulation methodology could be successfully performed with
variety of unsymmetrical dipivalates under very mild conditions.
On the basis of theoretical calculation of stabilization values of
the benzylic carbocations, a reasonable mechanism for the
formation of annulated heterocycles was proposed. The
attractive feature of this methodology is that a large number
of π-conjugated arenes as well as heteroarenes are easily
accessible. The anthracene as well as annulated thiophene
derivatives reported herein may find application in OLEDs.25
EXPERIMENTAL SECTION
General Methods. All melting points were uncorrected. Dry THF
was prepared by refluxing with sodium. Dry DCM was prepared by
refluxing with P2O5. The progression of reaction was monitored by
■
The interaction of 3-benzo[b]thiophenyl dipivalates 12l−q
with 20 mol % of ZnBr2 led to the formation of corresponding
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Table 2. ZnBr2-Mediated Intramolecular Cyclization of Unsymmetrical Dipivalates
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Table 2. continued
a
b
Isolated yield after column chromatographic purification. No characterizable product could be isolated.
TLC using a mixture of hexane/ethyl acetate as an eluent. Column
chromatography was carried out on silica gel (230−400 mesh, Merck)
by using increasing polarity. 1H, 13C and DEPT 135 spectra were
recorded in CDCl3 using TMS as an internal standard on a 300 MHz
spectrometer at room temperature. Chemical shift values were quoted
in parts per million (ppm), and coupling constants (J) were quoted in
hertz (Hz). High-resolution mass spectra (HRMS) were recorded
using EI and ES-TOF mass spectrometers.
Preparation of 2-Benzoylphenyl(thiophene-2-yl)methanone
(4a). To a stirred solution of benzo[c]furan 3a22 (1.0 g, 3.62 mmol) in
dry THF (20 mL), lead tetraacetate (LTA) (1.60 g, 3.62 mmol) was
added and then stirred at 50 °C for half an hour. The reaction mixture
was then poured into water (200 mL) and extracted with ethyl acetate
(2 × 20 mL), washed with brine solution and dried (Na2SO4).
Removal of solvent in vacuo followed by crystallization from methanol
furnished 4a as a brown solid (0.88 g, 84%): mp 134−135 °C (132.5−
133.3 °C);26 1H NMR (300 MHz, CDCl3) δ 7.68−7.61 (m, 3H),
7.57−7.54 (m, 4H), 7.46−7.40 (m, 2H), 7.29 (t, J = 7.6 Hz, 2H),
7.00−6.97 (m, 3H); 13C NMR (75 MHz, CDCl3) δ 196.6, 188.3,
144.2, 139.8, 139.6, 137.2, 135.0, 134.9, 133.1, 130.5 (2C), 129.9,
129.8, 129.1, 128.3, 128.2.
following the procedure similar to that of 4a furnished 4b as a colorless
solid (0.94 g, 89%): mp 126−128 °C; 1H NMR (300 MHz, CDCl3) δ
7.74−7.70 (m, 1H), 7.64−7.59 (m, 6H), 7.45−7.46 (m, 1H), 7.17 (d, J
= 8.1 Hz, 2H), 7.06−7.03 (m, 1H), 2.37 (s, 3H); 13C NMR (75 MHz,
CDCl3) δ 196.2, 188.4, 144.1, 144.0, 139.8, 139.7, 135.0, 134.8, 134.7,
130.5, 130.3, 130.0, 129.6, 129.1, 128.0, 21.7; DEPT 135 (75 MHz,
CDCl3) δ 135.0, 134.8, 130.5, 130.3, 130.0, 129.6, 128.0, 21.7. Anal.
Calcd for C19H14O2S: C, 74.48; H, 4.61; S, 10.47. Found: C, 74.22; H,
4.41; S, 10.35.
Preparation of (2-(4-Methoxylbenzoyl)phenyl(thiophene-2-
yl)methanone (4c). Ring-opening of 3-(thiophen-2-yl)-
isobenzofuran-1(3H)-one27 with freshly prepared p-anisyl magnesium
bromide followed by acidic workup gave benzo[c]furan 3c as a
fluorescent bright yellow solid. Oxidation of the benzo[c]furan 3c (0.5
g, 1.63 mmol) with LTA (0.72 g, 1.62 mmol) using the procedure
similar to that of 4a furnished 4c as a colorless solid (0.48 g, 91%): mp
1
131−132 °C; H NMR (300 MHz, CDCl3) δ 7.65−7.61 (m, 3H),
7.56−7.52 (m, 4H), 7.40−7.39 (m, 1H), 6.99−6.97 (m, 1H), 6.77 (d, J
= 8.7 Hz, 2H), 3.76 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 195.3,
188.4, 163.6, 144.2, 140.0, 139.5, 135.1, 134.8, 132.3, 130.5, 130.2,
130.1, 129.4, 129.0, 128.0, 113.6, 55.5; DEPT 135 (75 MHz, CDCl3) δ
135.1, 134.8, 132.2, 130.5, 129.4, 129.0, 128.0, 113.6, 55.5. Anal. Calcd
for C19H14O3S: C, 70.79; H, 4.38; S, 9.95. Found: C, 70.58; H, 4.23; S,
9.71.
Preparation of (2-(4-Methylbenzoyl)phenyl(thiophene-2-yl)-
methanone (4b). Ring-opening of 3-(thiophen-2-yl)isobenzofuran-
1(3H)-one27 with freshly prepared p-tolylmagnesium bromide
followed by acidic workup gave benzo[c]furan 3b as a fluorescent
bright yellow solid. Oxidative cleavage of the benzo[c]furan 3b22 (1 g,
3.44 mmol) using LTA (1.52 g, 3.42 mmol) in dry THF (20 mL)
Preparation of Annulated Compounds (6a) and (7a). To a
solution of diketone 4a (0.8 g, 2.73 mmol) in THF−ethanol (20 mL;
1:3), sodium borohydride (0.52 g, 13.69 mmol) was added in portions
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and refluxed for 4 h. The reaction mixture was then poured into water
(200 mL), extracted with ethyl acetate (2 × 20 mL) and dried
(Na2SO4). The removal of solvent gave crude diol (0.81 g, 2.73
mmol), which was dissolved in dry DCM (20 mL). To this, pivaloyl
chloride (1.62 g, 13.51 mmol), triethylamine (5.46 g, 54.05 mmol),
and a catalytic amount of DMAP (10 mg) were added. The reaction
mixture was refluxed under nitrogen atmosphere for half an hour, and
then hexane (20 mL) was added to the reaction mixture. The
triethylamine hydrochloride salt formed was filtered off. The filtrate
was concentrated, and the crude product was purified using column
chromatography (silica gel; hexane−ethyl acetate 98:2). Pivaloyl ester
5a (0.99 g, 2.13 mmol) was then dissolved in dry DCM (20 mL), a
catalytic amount of ZnBr2 (0.02 g, 0.13 mmol) was added, and stirred
for 20 min under nitrogen atmosphere. Removal of solvent followed
by column chromatographic purification (silica gel; hexane−ethyl
acetate, 99:1) led to the isolation of an inseparable 1:1 mixture (based
on 1H NMR integration of singlet proton at δ 8.50 and 8.39) of 6a and
NMR (300 MHz, CDCl3) δ 7.69−7.67 (m, 1H), 7.60−7.51 (m, 6H),
7.42 (d, J = 3.6 Hz 1H), 7.27 (d, J = 3.6 Hz, 2H), 7.02−7.0 (m, 1H);
13C NMR (75 MHz, CDCl3) δ 194.2, 186.8, 142.7, 138.4, 138.2, 134.4,
133.9, 133.8, 129.9, 129.5, 128.3, 128.1, 127.5, 126.9; HRMS (ES-
TOF) Calcd for C18H1135ClO2S [MNa+] 349.0060, found 349.0099;
HRMS (ES-TOF) Calcd for C18H1137ClO2S [MNa+] 351.0030, found
351.0029.
Preparation of 4-(4-Chlorophenyl)naptho[2,3-b]thiophene
(6d). Reduction of diketone 4d (0.60 g, 1.84 mmol) in THF−ethanol
(20 mL; 1:3) using sodium borohydride (0.35 g, 9.19 mmol) following
the procedure similar to that of 6a gave diol. The crude diol (0.50 g,
1.53 mmol) upon pivaloylation using pivaloyl chloride (0.92 g, 7.62
mmol) and triethylamine (3.09 g, 30.53 mmol) in the presence of a
catalytic amount of DMAP (10 mg) in dry DCM (20 mL) furnished
dipivalate 5d (0.65 g, 1.37 mmol). Dipivalate 5d upon interaction with
ZnBr2 (0.02 g, 0.13 mmol) followed by removal of solvent and column
chromatographic purification (silica gel; hexane−ethyl acetate, 99:2)
gave compound 6d as a colorless solid (0.28 g, 70%): mp 120−122
°C; 1H NMR (300 MHz, CDCl3) δ 8.35 (s, 1H), 7.89 (d, J = 8.4 Hz,
1H), 7.67 (d, J = 8.7 Hz, 1H), 7.48−7.41 (m, 2H), 7.37−7.31 (m,
5H), 7.02−7.0 (m, 1H); 13C NMR (75 MHz, CDCl3) δ 137.9, 137.8,
137.3, 133.6, 132.9, 132.5, 131.1, 129.0, 128.7, 128.1, 127.6, 126.0,
125.2, 123.2, 120.8; DEPT 135 (75 MHz, CDCl3) δ 132.1, 128.7,
128.1, 127.6, 126.0, 125.2, 123.2, 120.8; HRMS (EI) Calcd for
C18H11ClS [M+] 294.0270, found 294.0284.
1
7a as a colorless solid (0.7 g, 80%): mp 100−102 °C; H NMR (300
MHz, CDCl3) δ 8.50 (s, 1H), 8.39 (s, 1H), 8.03−8.00 (d, J = 8.3 Hz,
2H), 8.01−7.96 (m, 1H), 7.93−7.78 (m, 2H), 7.60−7.36 (m, 13H),
7.18−7.16 (m, 1H), 7.00−7.09 (m, 1H); 13C NMR (75 MHz, CDCl3)
δ 138.9, 138.8, 138.0, 137.7, 134.4, 131.8, 131.2, 131.1, 130.7, 129.4,
129.1, 128.7, 128.4, 128.3, 127.9, 127.6, 127.5 (2C), 127.1, 126.7,
126.6, 126.4, 125.9, 125.2, 125.1, 124.9, 123.6, 120.4; HRMS (EI)
Calcd for C18H12S [M+] 260.0660, found 260.0658.
Preparation of 4-p-Tolylnaphtho[2,3-b]thiophene (6b). Re-
duction of diketone 4b (0.94 g, 3.07 mmol) in THF−ethanol (20 mL;
1:3) using sodium borohydride (0.58 g, 15.35 mmol) following the
procedure similar to that of 6a gave diol. The crude diol (0.92 g, 2.96
mmol) upon pivaloylation using pivaloyl chloride (1.78 g, 14.83
mmol) and triethylamine (6.0 g, 59.35 mmol) in the presence of a
catalytic amount of DMAP (10 mg) in dry DCM (20 mL) furnished
dipivalate 5b. Dipivalate 5b (1.30 g, 2.71 mmol) upon interaction with
ZnBr2 (0.02 g, 0.13 mmol) followed by removal of solvent and column
chromatographic purification (silica gel; hexane−ethyl acetate, 99:1)
gave compound 6b as a pale yellow solid (0.75 g, 93%): mp 107−109
°C; 1H NMR (300 MHz, CDCl3) δ 8.36 (s, 1H), 7.90 (d, J = 8.1 Hz,
1H), 8.11 (d, J = 10.2 Hz, 1H), 7.46−7.31 (m, 7H), 7.11 (d, J = 7.8
Hz, 1H), 2.47 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 138.1, 137.8,
137.2, 135.8, 135.4, 131.2, 130.6, 129.2, 129.1, 127.6, 127.5, 126.5,
125.1, 124.9, 123.7, 120.3, 21.4; DEPT 135 (75 MHz, CDCl3) δ 130.6,
129.1, 127.6, 127.5, 126.5, 125.1, 124.9, 123.7, 120.3, 21.4. Anal. Calcd
for C19H14S: C, 83.17; H, 5.14; S, 11.69. Found: C, 82.81; H, 5.21; S,
11.52.
Preparation of 4-(4-Methoxyphenyl)naptho[2,3-b]-
thiophene (6c). Reduction of diketone 4c (0.55 g, 1.70 mmol) in
THF−ethanol (20 mL; 1:3) using sodium borohydride (0.32 g, 8.42
mmol) following the procedure similar to that of 6a gave diol. The
crude diol (0.53 g, 1.62 mmol) upon pivaloylation using pivaloyl
chloride (0.98 g, 8.12 mmol) and triethylamine (3.29 g, 32.51 mmol)
in the presence of a catalytic amount of DMAP (10 mg) in dry DCM
(20 mL) furnished dipivalate 5c (0.72 g, 1.45 mmol). Dipivalate 5c
upon interaction with ZnBr2 (0.02 g, 0.13 mmol) followed by removal
of solvent and column chromatographic purification (silica gel;
hexane−ethyl acetate, 99:1) gave compound 6c as a pale yellow
solid (0.43 g, 92%): mp 152−153 °C; 1H NMR (300 MHz, CDCl3) δ
8.37 (s, 1H), 7.92 (d, J = 8.1 Hz, 1H), 7.82 (d, J = 8.4 Hz, 1H), 7.50−
7.33 (m, 5H), 7.14−1.06 (m, 3H), 3.91 (s, 3H); 13C NMR (75 MHz,
CDCl3) δ 159.1, 138.2, 137.7, 134.2, 131.8, 131.2, 131.0, 129.4, 127.5,
127.4, 126.5, 125.1, 124.9, 123.7, 120.2, 113.9, 55.4; DEPT 135 (75
MHz, CDCl3) δ 131.8, 127.6, 127.5, 126.5, 125.1, 124.9, 123.7, 120.2,
113.8, 55.4. Anal. Calcd for C19H14OS: C, 78.59; H, 4.86; S, 11.04.
Found: C, 78.27; H, 4.71; S, 11.16.
2-(2-Methylbenzoyl)phenyl(thiophene-2-yl)methanone (4e).
Ring-opening of 3-(thiophen-2-yl)isobenzofuran-1(3H)-one27 with
freshly prepared o-tolylmagnesium bromide followed by acidic workup
gave benzo[c]furan 3e as a fluorescent bright yellow solid. Oxidation
of the benzo[c]furan 3e (1.0 g, 3.44 mmol) using LTA (1.52 g, 3.44
mmol) adopting the procedure similar to that of 4a furnished diketone
1
4e as a brown solid (0.92 g, 88%): mp 98−100 °C; H NMR (300
MHz, CDCl3) δ 7.63−7.58 (m, 5H), 7.41−7.39 (m, 1H), 7.32−7.27
(m, 2H), 7.17 (d, J = 7.5 Hz, 1H), 7.11−7.03 (m, 2H), 2.33 (s, 3H);
13C NMR (75 MHz, CDCl3) δ 198.0, 188.8, 144.4, 140.3, 140.0, 139.0,
137.3, 134.8, 134.7, 131.5, 131.3, 131.2, 130.7, 130.5, 130.3, 128.5,
128.0, 125.1, 20.5. Anal. Calcd for C19H14O2S: C, 74.48; H, 4.61; S,
10.47. Found: C, 74.72; H, 4.25; S, 10.24.
4-o-Tolylnaptho[2,3-b]thiophene (6e). Reduction of diketone
4e (0.92 g, 3.0 mmol) using sodium borohydride (0.57 g, 15.03 mmol)
followed by workup led to diol. Dipivaloylation of the diol (0.90 g,
2.90 mmol) using pivaloyl chloride (1.75 g, 14.51 mmol) and
triethylamine (5.87 g, 58.06 mmol) in the presence of a catalytic
amount of DMAP (10 mg) in dry DCM (20 mL) led to the isolation
of dipivalate 5e. Dipivalate 5e (1.20 g, 2.51 mmol) upon interaction
with ZnBr2 (0.02 g, 0.13 mmol) followed by removal of solvent and
column chromatographic purification (silica gel; hexane−ethyl acetate,
99:1) gave compound 6e as a brown solid (0.47 g, 65%): mp 98−100
°C; 1H NMR (300 MHz, CDCl3) δ 8.40 (s, 1H), 7.96 (d, J = 8.4 Hz,
1H), 7.6−7.2 (m, 4H), 6.92−6.90 (m, 1H), 1.92 (s, 3H); 13C NMR
(75 MHz, CDCl3) δ 138.2, 137.9, 137.7, 137.3, 133.8, 131.1, 130.7,
130.1, 129.1, 129.7, 127.7, 127.6, 126.6, 125.8, 125.1, 125.0, 123.4,
120.3; DEPT 90 (75 MHz, CDCl3) δ 130.7, 130.1, 127.9, 127.7, 127.6,
126.2, 125.8, 125.1, 125.0, 123.4, 120.3. Anal. Calcd for C19H14S: C,
83.17; H, 5.14; S, 11.69. Found: C, 82.93; H, 5.21; S, 11.76.
(2-(3,4-Dimethylbenzoyl)phenyl)(thiophene-2-yl)-
methanone (4f). Ring-opening of 3-(3,4-dimethylphenyl)-
isobenzofuran-1(3H)-one with freshly prepared 2-thienylmagnesium
bromide followed by acidic workup gave benzo[c]furan 3f as a
fluorescent bright yellow solid. Oxidation of the benzo[c]furan 3f
(0.78 g, 2.56 mmol) using LTA (1.13 g, 2.56 mmol) following the
procedure similar to that of 4a furnished diketone 4f as a pale yellow
solid (0.69 g, 85%): mp 126−128 °C; 1H NMR (300 MHz, CDCl3) δ
7.74−7.71 (m, 1H), 7.64−7.60 (m, 4H), 7.49−7.42 (m, 3H), 7.12 (d, J
= 7.8 Hz, 1H), 7.08−7.05 (m, 1H), 2.28 (s, 3H), 2.22 (s, 3H); 13C
NMR (75 MHz, CDCl3) δ 196.4, 188.4, 144.2, 142.7, 140.0, 136.8,
135.0, 134.9, 134.6, 130.9, 130.4, 130.2, 129.7, 129.6, 129.0, 127.9,
127.8, 20.0, 19.6. Anal. Calcd for C20H16O2S: C, 74.97; H, 5.03; S,
10.01. Found: C, 74.76; H, 5.40; S, 10.21.
Preparation of (2-(4-Chlorobenzoyl)phenyl(thiophene-2-yl)-
methanone (4d). Ring-opening of 3-(4-chlorophenyl)isobenzofuran-
1(3H)-one with freshly prepared 2-thienyl magnesium bromide
followed by acidic workup gave benzo[c]furan 3d as a fluorescent
yellow solid. Oxidation of the benzo[c]furan 3d (0.7 g, 2.25 mmol)
with LTA (0.99 g, 2.23 mmol) using the procedure similar to that of
4a furnished 4d as a brown solid (0.53 g, 72%): mp 124−126 °C; 1H
9058
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Article
4-(3,4-Dimethylphenyl)naptho[2,3-b]thiophene (6f). Reduc-
tion of diketone 4f (0.74 g, 2.43 mmol) using sodium borohydride
(0.46 g, 12.17 mmol) followed by workup led to diol. Dipivaloylation
of the diol (0.74 g, 2.40 mmol) using pivaloyl chloride (1.44 g, 11.94
mmol) and triethylamine (4.86 g, 48.02 mmol) in the presence of
catalytic amount of DMAP (10 mg) in dry DCM (20 mL) led to the
isolation of dipivalate 5f. Dipivalate 5f (0.99 g, 2.07 mmol) upon
interaction with ZnBr2 (0.02 g, 0.13 mmol) followed by removal of
solvent and column chromatographic purification (silica gel; hexane−
ethyl acetate, 99:1) led to the isolation of 6f as a pale yellow solid
(0.80 g, 93%): mp 118−120 °C; 1H NMR (300 MHz, CDCl3) δ 8.36
(s, 1H), 7.96 (d, J = 8.1 Hz, 1H), 7.80−7.75 (m, 2H), 7.59−7.56 (m,
2H), 7.42−7.23 (m, 2H), 7.15−7.14 (m, 1H), 2.44 (s, 3H), 2.36 (s,
3H); 13C NMR (75 MHz, CDCl3) δ 139.4, 136.3, 135.5, 131.5, 130.9,
130.7, 129.2, 128.2, 127.3, 127.1, 126.6, 126.5, 125.3, 124.7, 20.8, 20.2;
DEPT 135 (75 MHz, CDCl3) δ 129.2, 128.2, 127.1, 126.6, 126.5,
125.4, 125.3, 124.7, 20.8, 20.2; HRMS (EI) Calcd for C20H16S [M+]
288.0973, found 288.0978.
(2-(2,4-Dimethylbenzoyl)phenyl)(thiophene-2-yl)-
methanone (4g). Ring-opening of 3-(2,4-dimethylphenyl)-
isobenzofuran-1(3H)-one with freshly prepared 2-thienylmagnesium
bromide followed by acidic workup gave benzo[c]furan 3g as a
fluorescent bright yellow solid. Oxidation of the benzo[c]furan 3g
(1.76 g, 5.78 mmol) using LTA (2.56 g, 5.78 mmol) adopting the
procedure similar to that of 4a furnished diketone 4g as a brown solid
(1.69 g, 91%): mp 98−100 °C; 1H NMR (300 MHz, CDCl3) δ 7.63−
7.54 (m, 5H), 7.40−7.39 (m, 1H), 7.21−7.18 (m, 1H), 7.05−7.02 (m,
1H), 6.99 (s, 1H), 6.90 (d, J = 8.1 Hz, 1H), 2.29 (s, 6H); 13C NMR
(75 MHz, CDCl3) δ 197.9, 188.8, 144.4, 142.2, 140.4, 140.1, 139.4,
134.9, 134.6, 134.5, 132.2, 131.4, 130.9, 130.3, 130.2, 128.5, 128.0,
125.8, 21.4, 20.5; DEPT 135 (75 MHz, CDCl3) δ 134.9, 134.7, 132.2,
131.4, 130.9, 130.3, 130.2, 128.5, 128.0, 125.8, 21.4, 20.5. Anal. Calcd
for C20H16O2S: C, 74.97; H, 5.03; S, 10.01. Found: C, 74.84; H, 5.03;
S, 10.17.
4-(3,4-Dimethoxyphenyl)naptho[2,3-b]thiophene (6h). Re-
duction of diketone 4h (0.46 g, 1.30 mmol) using sodium borohydride
(0.24 g, 6.31 mmol) followed by workup led to diol. Dipivaloylation of
the diol (0.43 g, 1.20 mmol) using pivaloyl chloride (0.72 g, 34.98
mmol) and triethylamine (2.44 g, 24.11 mmol) in the presence of a
catalytic amount of DMAP (10 mg) in dry DCM (20 mL) led to the
isolation of dipivalate 5h. Dipivalate 5h (0.65 g,1.24 mmol) upon
interaction with ZnBr2 (0.02 g, 0.13 mmol) followed by removal of
solvent and column chromatographic purification (silica gel; hexane−
ethyl acetate 99:1) led to the isolation of product 6h as a thick liquid
1
(0.35 g, 92%): H NMR (300 MHz, CDCl3) δ 8.38 (s, 1H), 7.95−
7.7.81 (m, 2H), 7.48−7.39 (m, 3H), 7.16−7.00 (m, 4H), 3.99 (s, 3H),
3.86 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 148.8, 148.5, 138.2,
137.7, 134.3, 131.4, 131.1, 129.4, 127.6, 126.4, 125.1, 125.0, 123.7,
123.0, 120.3, 113.9, 111.1, 56.0; DEPT 135 (75 MHz, CDCl3) δ 127.5,
126.5, 125.1, 125.0, 123.7, 123.0, 113.9, 111.1, 56.0. Anal. Calcd for
C20H16O2S: C, 74.97; H, 5.03; S, 10.01. Found: C, 75.23; H, 5.18; S,
9.89.
(2-(2-Methoxy-1-naphthoyl)phenyl)(thiophen-2-yl)-
methanone (4i). Ring-opening of 3-(2-methoxy-1-naphthyl)-
isobenzofuran-1(3H)-one28 with freshly prepared 2-thienylmagnesium
bromide followed by acidic workup gave benzo[c]furan 3i as a
fluorescent yellow solid. Oxidation of the benzo[c]furan 3i (1.25 g,
3.51 mmol) using LTA (1.55 g, 3.51 mmol) adopting the procedure
similar to that of 4a furnished diketone 4i as a pale yellow solid (1.21
g, 93%): mp 162−164 °C; 1H NMR (300 MHz, CDCl3) δ 7.89 (d, J =
9 Hz, 1H), 7.74 (d, J = 6.9 Hz, 1H), 7.65−7.58 (m, 3H), 7.54−7.43
(m, 3H), 7.35−7.29 (m, 3H), 7.20 (d, J = 9 Hz, 1H), 6.99−6.96 (m,
1H), 3.74 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 196.3, 190.0, 155.4,
144.9, 140.5, 138.3, 134.4, 134.2, 132.6, 132.3, 132.0, 131.1, 129.9,
128.7, 128.0, 127.9, 127.8, 127.7, 124.2, 124.1, 121.8, 56.4. Anal. Calcd
for C23H16O3S: C, 74.17; H, 4.33; S, 8.61. Found: C, 74.01; H, 4.35; S,
8.91.
4-(2-Methoxynapthalen-1-yl)naptho[2,3-b]thiophene (6i).
Reduction of diketone 4i (1.09 g, 2.93 mmol) using sodium
borohydride (0.55 g, 14.47 mmol) followed by workup led to diol.
Dipivaloylation of the diol (1.0 g, 2.65 mmol) using pivaloyl chloride
(1.60 g, 13.29 mmol) and triethylamine (5.38 g, 53.19 mmol) in the
presence of a catalytic amount of DMAP (10 mg) in dry DCM (20
mL) led to the isolation of dipivalate 5i. Dipivalate 5i (1.30 g, 2.38
mmol) upon interaction with ZnBr2 (0.02 g, 0.13 mmol) followed by
removal of solvent and column chromatographic purification (silica
gel; hexane−ethyl acetate, 99:1) led to the isolation of product 6i as a
4-(2,4-Dimethylphenyl)naptho[2,3-b]thiophene (6g). Reduc-
tion of diketone 4g (1.50 g, 4.68 mmol) using sodium borohydride
(0.94 g, 24.73 mmol) followed by workup led to diol. Dipivaloylation
of the diol (1.41 g, 4.57 mmol) using pivaloyl chloride (2.79 g, 22.39
mmol) and triethylamine (9.26 g, 91.51 mmol) in the presence of a
catalytic amount of DMAP (10 mg) in dry DCM (20 mL) led to the
isolation of dipivalate 5g. Dipivalate 5g (1.70 g, 3.57 mmol) upon
interaction with ZnBr2 (0.02 g, 0.13 mmol) followed by removal of
solvent and column chromatographic purification (silica gel; hexane−
ethyl acetate, 99:1) led to the isolation of product 6g as a thick light
1
colorless solid (1.06 g, 90%): mp 208−210 °C; H NMR (300 MHz,
CDCl3) δ 8.46 (s, 1H), 8.03−7.96 (m, 2H), 7.88 (d, J = 8.4 Hz, 1H),
7.48−7.40 (m, 3H), 7.32−7.21 (m, 3H), 7.13 (t, J = 7.5 Hz, 1H), 6.92
(d, J = 8.7 Hz, 1H), 6.73−6.71 (m, 1H), 3.67 (s, 3H); 13C NMR (75
MHz, CDCl3) δ 155.1, 139.1, 137.8, 134.0, 131.3, 130.1, 130.0, 129.1,
128.8, 128.1, 127.9, 127.7, 126.7, 126.4, 125.5, 125.1, 125.0, 123.7,
121.2, 120.7, 113.9, 56.8; DEPT 135 (75 MHz, CDCl3) δ 130.0, 127.9,
127.8, 127.7, 126.7, 126.4, 125.5, 125.1, 125.0, 123.7, 120.7, 113.9,
56.8; HRMS (EI) Calcd for C23H16OS 340.0922, found 340.0920.
2-(Tetraphene-7-yl)thiophene (6j). Oxidation of benzo[c]furan
3j (1.5 g, 4.6 mmol) with LTA (2.04 g, 4.6 mmol) using the procedure
similar to that of 4a furnished diketone 4j as a colorless solid.
Reduction of the crude diketone 4j (1.56 g, 4.56 mmol) using sodium
borohydride (0.87 g, 22.89 mmol) followed by workup gave diol (1.39
g, 3.75 mmol). The dipivaloylation of the diol using pivaloyl chloride
(2.42 g, 20.06 mmol) and triethylamine (8.13 g, 80.3 mmol) in the
presence of a catalytic amount of DMAP (10 mg) in dry DCM (20
mL) led to the isolation of dipivalate 5j. Dipivalate 5j (1.58 g, 3.07
mmol) upon interaction with ZnBr2 (0.02 g, 0.13 mmol) followed by
removal of solvent and column chromatographic purification (silica
gel; hexane−ethyl acetate, 99:1) led to the isolation of product 6j as a
1
brown liquid (1.35 g, 82%): H NMR (300 MHz, CDCl3) δ 8.32 (s,
1H), 7.87 (d, J = 8.4 Hz, 1H), 7.65 (d, J = 8.4 Hz, 1H), 7.39−7.32 (m,
1H), 7.31−7.27(m, 2H), 7.18−7.12 (m, 2H), 6.90−6.89 (m, 1H), 2.41
(s, 3H), 1.86 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 138.2, 137.8,
137.6, 137.1, 135.4, 134.0, 131.2, 131.0, 130.7, 129.4, 127.7, 126.7,
126.5, 125.2, 125.1, 123.7, 120.3, 21.4, 19.9; DEPT 90 (75 MHz,
CDCl3) δ 131.0, 130.7, 129.4, 128.8, 127.7, 127.2, 126.7, 126.5, 125.9,
125.2, 125.1, 124.4, 123.7, 120.3. Anal. Calcd for C20H16S: C, 83.29; H,
5.59; S, 11.12. Found: C, 82.97; H, 5.41; S, 11.24.
(2-(3,4-Dimethoxybenzoyl)phenyl)(thiophene-2-yl)-
methanone (4h). Ring-opening of 3-(3,4-dimethoyphenyl)-
isobenzofuran-1(3H)-one28 with freshly prepared 2-thienylmagnesium
bromide followed by acidic workup gave benzo[c]furan 3h as a
fluorescent yellow solid. Oxidation of the benzo[c]furan 3h (0.52 g,
1.54 mmol) using LTA (0.62 g, 1.54 mmol) following the procedure
similar to that of 4a furnished diketone 4h as a brown solid (0.48 g,
1
89%): mp 128−130 °C; H NMR (300 MHz, CDCl3) δ 7.75−7.72
(m, 1H), 7.65−7.60 (m, 4H), 7.47−7.46 (m, 1H), 7.33−7.32 (m, 1H),
7.24−7.21 (m, 1H), 7.08−7.05 (m, 1H), 6.77 (d, J = 8.1 Hz, 1H), 3.94
(s, 3H), 3.77 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 195.3, 188.4,
153.4, 149.0, 144.2, 139.9, 135.0, 134.8, 130.6, 130.4, 130.2, 129.5,
129.0, 128.0, 125.6, 111.1, 109.7, 56.0, 55.9; DEPT 135 (75 MHz,
CDCl3) δ 135.0, 134.8, 130.6, 130.2, 129.5, 129.0, 128.0, 125.6, 111.1,
109.7, 56.0, 55.9. Anal. Calcd for C20H16O4S: C, 68.16; H, 4.58; S,
9.10. Found: C, 67.84; H, 4.35; S, 8.94.
1
colorless solid (1.01 g, 81%): mp 150−152 °C; H NMR (300 MHz,
CDCl3) δ 9.30 (s, 1H), 8.88 (d, J = 8.1 Hz, 1H), 8.15 (d, J = 8.1 Hz,
1H), 7.83 (t, J = 6.9 Hz, 3H), 7.73−7.47 (m, 5H), 7.46−7.31 (m, 1H),
7.2−7.18 (m, 1H); 13C NMR (75 MHz, CDCl3) δ 139.2, 132.4, 131.6,
131.3, 130.6, 130.3, 129.4, 129.3, 128.6, 127.5, 127.3, 127.2, 127.1,
126.7, 126.5, 126.2, 125.7, 125.3, 123.1, 122.9. Anal. Calcd for
9059
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Article
C22H14S: C, 85.12; H, 4.55; S, 10.33. Found: C, 85.31; H, 4.40; S,
10.27.
isobenzofuran-1(3H)-one29 (1.0 g, 3.36 mmol) with freshly prepared
p-tolylmagnesium bromide [prepared from 4-bromotoluene (1.14 g,
6.66 mmol) and Mg (0.20 g, 8.20 mmol)] followed by acidic workup
gave benzo[c]furan 3m30 as a fluorescent thick orange liquid (0.64 g,
(2-(4-Methyl-1-naphthoyl)phenyl)(thiophen-2-yl)-
methanone (4k). Ring-opening of 3-(4-methyl-1-naphthyl)-
isobenzofuran-1(3H)-one with freshly prepared 2-thienylmagnesium
bromide followed by acidic workup gave benzo[c]furan 3k as a
fluorescent yellow solid. Oxidative cleavage of the benzo[c]furan 3k
(1.1 g, 3.23 mmol) using LTA (1.43 g, 3.23 mmol) following the
procedure similar to that of 4a furnished diketone 4k as a dark brown
solid (0.95 g, 83%): mp 154−156 °C; 1H NMR (300 MHz, CDCl3) δ
8.33 (d, J = 8.1 Hz, 1H), 7.89 (d, J = 8.4 Hz, 1H), 7.62−7.60 (m, 1H),
7.55−7.30 (m, 8H), 7.13−7.10 (m, 1H), 6.92−6.89 (m, 1H), 2.60 (s,
3H); 13C NMR (75 MHz, CDCl3) δ 197.4, 188.8, 144.5, 140.7, 140.6,
134.8, 134.6, 133.5, 132.7, 131.3, 131.2, 131.0, 130.7, 128.6, 128.0,
127.4, 126.4, 126.3, 124.9, 124.1, 20.1; DEPT 135 (75 MHz, CDCl3) δ
134.8, 134.7, 131.3, 131.1, 130.7, 128.6, 128.0, 127.4, 126.3, 124.9,
124.1, 20.1. Anal. Calcd for C23H16O2S: C, 77.50; H, 4.52; S, 9.0.
Found: C, 77.31; H, 4.63; S, 8.79.
2-(5-Methyl-tetraphen-7-yl)thiophene (6k). Reduction of
diketone 4k (1.27 g, 3.56 mmol) using sodium borohydride (0.54 g,
14.21 mmol) followed by workup led to diol. Dipivaloylation of the
diol (1.13 g, 3.13 mmol) using pivaloyl chloride (1.89 g, 15.67 mmol)
and triethylamine (6.35 g, 62.75 mmol) in the presence of a catalytic
amount of DMAP (10 mg) in dry DCM (20 mL) led to the isolation
of dipivalate 5k. Dipivalate 5k (1.39 g, 2.63 mmol) upon interaction
with ZnBr2 (0.02 g, 0.13 mmol) followed by removal of solvent and
column chromatographic purification (silica gel; hexane−ethyl acetate,
99:1) led to the isolation of product 6k as a pale yellow solid (0.93 g,
92%): mp 190−192 °C; 1H NMR (300 MHz, CDCl3) δ 9.13 (s, 1H),
8.79 (d, J = 7.2 Hz, 1H), 8.02 (d, J = 7.5 Hz, 1H), 7.90 (d, J = 6.9 Hz,
1H), 7.71 (d, J = 8.1 Hz, 1H), 7.61−7.09 (m, 8H), 2.51 (s, 3H); 13C
NMR (75 MHz, CDCl3) δ 139.4, 133.1, 132.5, 132.0, 130.6, 129.4,
128.6, 128.2, 128.1, 127.3, 127.2, 126.8, 126.6, 126.3, 126.1, 125.3,
124.8, 124.6, 123.3, 122.7, 20.6; DEPT 135 (75 MHz, CDCl3) δ 129.3,
128.5, 127.3, 127.2, 126.7, 126.6, 126.3, 125.3, 124.7, 124.6, 123.3,
122.7, 20.6. Anal. Calcd for C23H16S: C, 85.15; H, 4.97; S, 9.88.
Found: C, 84.89; H, 5.14; S, 9.72.
1
52%): H NMR (300 MHz, CDCl3) δ 7.75−7.72 (m, 3H), 7.66.7.63
(m, 1H), 7.29 (d, J = 3.9 Hz, 1H), 7.22−7.11 (m, 5H), 6.98−6.94 (m,
3H), 2.33 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 143.9, 139.4, 137.3,
137.0, 135.6, 132.4, 129.7, 128.6, 128.0, 125.3, 125.3, 124.7, 124.5,
124.3, 123.5, 122.5, 121.9, 121.6, 120.3, 119.9, 21.4; DEPT 135 (75
MHz, CDCl3) δ 129.7, 128.0, 125.3, 124.7, 124.5, 124.3, 123.5, 122.5,
120.3, 119.9, 21.4.
(2,2′-Bithiophen-5-yl)(2-(4-methylbenzoyl)phenyl)-
methanone (4m). Oxidation of benzo[c]furan 3m (0.5 g, 1.34
mmol) using LTA (0.59 g, 1.34 mmol) following the procedure similar
to that of 4a furnished diketone 4m30 as a pale yellow solid (0.45 g,
1
88%): mp 140−142 °C; H NMR (300 MHz, CDCl3) δ 7.67−7.64
(m, 1H), 7.56−7.50 (m, 5H), 7.30−7.18 (m, 3H), 7.1 (d, J = 8.1 Hz,
2H), 7.03 (d, J = 3.9 Hz, 1H), 6.98−6.94 (m, 1H), 2.31 (s, 3H); 13C
NMR (75 MHz, CDCl3) δ 196.2, 187.9, 146.7, 144.0, 142.1, 139.8,
139.4, 136.2, 135.9, 134.7, 130.4, 130.3, 130.0, 129.6, 129.0, 128.9,
126.6, 125.8, 124.1, 21.7; DEPT 135 (75 MHz, CDCl3) δ 135.9, 130.4,
130.3, 130.0, 129.6, 129.0, 128.9, 128.2, 126.6, 125.8, 124.1, 21.7.
2-(Thiophene-2-yl)-4-p-tolylnatho[2,3-b]thiophene (6m). Re-
duction of diketone 4m (0.75 g, 1.94 mmol) using sodium
borohydride (0.29 g, 7.77 mmol) followed by workup led to diol.
Dipivaloylation of the diol (0.78 g, 2.0 mmol) using pivaloyl chloride
(1.59 g, 10.26 mmol) and triethylamine (1.23 g, 41.05 mmol) in the
presence of a catalytic amount of DMAP (10 mg) in dry DCM (20
mL) led to the isolation of dipivalate 5m. Dipivalate 5m (0.94 g, 1.68
mmol) upon interaction with ZnBr2 (0.02 g, 0.13 mmol) followed by
removal of solvent and column chromatographic purification (silica
gel; hexane−ethyl acetate, 99:1) led to the isolation of product 6m as a
1
pale yellow solid (0.57 g, 81%): mp 190−192 °C; H NMR (300
MHz, CDCl3) δ 8.18 (s, 1H), 7.82 (d, J = 8.4 Hz, 1H), 7.69 (d, J = 8.4
Hz, 1H), 7.43 (d, J = 9.0 Hz, 1H), 7.39−7.17 (m, 8H), 7.09 (s, 1H),
6.95 (t, J = 4.3 Hz, 1H), 2.44 (s, 3H); 13C NMR (75 MHz, CDCl3) δ
138.8, 137.7, 137.4, 137.3, 137.2, 135.6, 134.2, 131.4, 130.6, 129.7,
129.2, 127.9, 127.4, 126.4, 125.9, 125.6, 125.1, 125.0, 119.7, 119.1,
21.4; HRMS (EI) Calcd for C23H16S2 356.0693, found 356.0693.
(2-Benzoylphenyl)(p-tolyl)methanone (4n). Ring-opening of 3-
(4-methylphenyl)isobenzofuran-1(3H)-one31 with freshly prepared
phenylmagnesium bromide followed by acidic workup gave benzo[c]-
furan 3n as a fluorescent bright yellow solid. Oxidation of the
benzo[c]furan 3n (2.18 g, 7.67 mmol) using LTA (3.32 g, 7.66 mmol)
adopting the procedure similar to that of 4a furnished diketone 4n26 as
Biphenyl-4-yl(2-(thiophen-2-carbonyl)phenyl)methanone
(4l). Ring-opening of 3-(biphenyl-4-yl)isobenzofuran-1(3H)-one with
freshly prepared 2-thienylmagnesium bromide followed by acidic
workup gave benzo[c]furan 3l as a fluorescent yellow solid. Oxidative
cleavage of the benzo[c]furan 3l (1.51 g, 4.17 mmol) using LTA (1.84
g, 4.17 mmol) adopting the procedure similar to that of 4a furnished
1
diketone 4l as a colorless solid (1.35 g, 85%): mp 150−152 °C; H
NMR (300 MHz, CDCl3) δ 7.72−7.66 (m, 3H), 7.56−7.55 (m, 3H),
7.52−7.49 (m, 3H), 7.43−4.41 (m, 1H), 7.39−7.27 (m, 2H), 7.00−
6.97 (m, 1H); 13C NMR (75 MHz, CDCl3) δ 196.2, 188.3, 145.8,
144.1, 139.9, 139.8, 139.7, 135.9, 135.0, 134.9, 130.6, 130.4, 129.6,
129.2, 128.9, 128.2, 128.0, 127.3, 127.0. Anal. Calcd for C24H16O2S: C,
78.24; H, 4.38; S, 8.70. Found: C, 77.98; H, 4.52; S, 8.93.
1
a pale yellow solid (2.01 g, 87%): mp 146−147 °C; H NMR (300
MHz, CDCl3) δ 7.70 (d, J = 7.8 Hz, 2H), 7.61−7.60 (m, 6H), 7.53−
7.48 (m, 1H), 7.39−7.34 (m, 2H), 7.17 (d, J = 7.8 Hz, 2H), 2.37 (s,
3H); 13C NMR (75 MHz, CDCl3) δ 196.7, 196.3, 143.9, 140.3, 139.9,
137.2, 134.7, 133.0, 130.3, 130.1, 130.0, 129.8, 129.6, 129.5, 129.0,
128.3, 21.7; DEPT 135 (75 MHz, CDCl3) δ 133.0, 130.3, 130.2, 130.0,
129.6, 129.5, 129.1, 128.3, 21.7.
2-(2-Phenylanthracen-9-yl)thiophene (6l). Reduction of dike-
tone 4l (0.42 g, 1.11 mmol) using sodium borohydride (0.21 g, 5.58
mmol) followed by workup led to diol. Dipivaloylation of the diol
(0.40 g, 1.05 mmol) using pivaloyl chloride (0.63 g, 5.22 mmol) and
triethylamine (2.13 g, 21.04 mmol) in the presence of a catalytic
amount of DMAP (10 mg) in dry DCM (20 mL) led to the isolation
of dipivalate 5l. Dipivalate 5l (0.66 g, 1.20 mmol) upon interaction
with ZnBr2 (0.02 g, 0.13 mmol) followed by removal of solvent and
column chromatographic purification (silica gel; hexane−ethyl acetate,
99:1) led to the isolation of product 6l as a colorless solid (0.33 g,
93%): mp 206−208 °C; 1H NMR (300 MHz, CDCl3) δ 8.32 (s, 1H),
7.86 (d, J = 8.4 Hz, 1H), 7.99 (d, J = 8.7 Hz, 1H), 7.69−7.62 (m, 4H),
7.47−7.27 (m, 8H), 7.13−7.09 (m, 1H); 13C NMR (75 MHz, CDCl3)
δ 140.8, 140.3, 138.0, 137.8, 134.0, 131.2, 130.5, 129.1, 128.9, 127.7,
127.6, 127.5, 127.2, 127.1, 126.4, 125.2, 125.0, 123.6, 120.5; DEPT
135 (75 MHz, CDCl3) δ 131.2, 130.5, 128.9, 127.7, 127.6, 127.5,
127.2, 127.1, 126.4, 125.2, 125.0, 123.6, 120.5. Anal. Calcd for
C24H16S: C, 85.68; H, 4.79; S, 9.53; Found: C, 85.39; H, 4.61; S, 9.75.
Preparation of 1-(5-(Thiophen-2-yl)thiophen-2-yl)-3-p-toly-
lisobenzofuran (3m). Ring-opening of 3-(2,2′-bithiophen-5-yl)-
9-p-Tolylanthracene (6n). Reduction of diketone 4n (1.0 g, 3.33
mmol) using sodium borohydride (0.63 g, 16.57 mmol) followed by
workup led to diol. Dipivaloylation of the diol (1.0 g, 3.28 mmol)
using pivaloyl chloride (1.98 g, 16.44 mmol) and triethylamine (6.65 g,
65.78 mmol) in the presence of a catalytic amount of DMAP (10 mg)
in dry DCM (20 mL) led to the isolation of dipivalate 5n. Dipivalate
5n (1.30 g, 2.75 mmol) upon interaction with ZnBr2 (0.02 g, 0.13
mmol) followed by removal of solvent and column chromatographic
purification (silica gel; hexane−ethyl acetate, 99:1) led to the isolation
of product 6n as a pale yellow solid (0.86 g, 89%): mp 108−110 °C;
1H NMR (300 MHz, CDCl3) δ 8.47 (s, 1H), 8.03 (d, J = 8.4 Hz, 2H),
7.70 (d, J = 8.7 Hz, 2H), 7.45−7.30 (m, 8H), 2.52 (s, 3H); 13C NMR
(75 MHz, CDCl3) δ 137.2, 137.1, 135.7, 131.4, 131.1, 130.3, 129.1,
128.3, 127.0, 126.4, 125.2, 125.0, 21.4; DEPT 135 (75 MHz, CDCl3) δ
131.1, 129.0, 128.3, 127.0, 126.3, 125.2, 125.0. Anal. Calcd for C21H16:
C, 93.99; H, 6.01. Found: C, 93.58; H, 5.96.
(2-Benzoylphenyl)(4-methoxyphenyl)methanone (4o). Ring-
opening of 3-(phenyl)isobenzofuran-1(3H)-one with freshly prepared
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p-anisylmagnesium bromide followed by acidic workup gave benzo-
[c]furan 3o as a fluorescent bright yellow solid. Oxidation of the
benzo[c]furan 3o (2.41 g, 8.03 mmol) using LTA (3.56 g, 8.03 mmol)
following the procedure similar to that of 4a furnished diketone 4o as
a pale yellow solid (2.22 g, 87%): mp 120−121 °C (118.6−119.1
°C);26 1H NMR (300 MHz, CDCl3) δ 7.72−7.67 (m, 4H), 7.64−7.62
(m, 4H), 7.55−7.50 (m, 1H), 7.41−7.36 (m, 2H), 6.86−6.85 (m, 2H),
3.85 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 196.7, 195.3, 163.6,
140.4, 139.8, 137.3, 133.0, 132.2, 130.3, 130.2, 130.0, 129.8, 129.6,
129.3, 128.3, 113.6, 55.5.
mmol) followed by workup gave diol. Dipivaloylation of the diol (0.79
g, 2.48 mmol) using pivaloyl chloride (1.49 g, 12.35 mmol) and
triethylamine (5.02 g, 49.60 mmol) in the presence of a catalytic
amount of DMAP (10 mg) in dry DCM (20 mL) led to the isolation
of dipivalate 5q. Dipivalate 5q (0.98 g, 2.01 mmol) upon interaction
with ZnBr2 (0.02 g, 0.13 mmol) followed by removal of solvent and
column chromatographic purification (silica gel; hexane−ethyl acetate,
99:1) gave compound 6q as a colorless solid (0.62 g, 86%): mp 166−
168 °C; 1H NMR (300 MHz, CDCl3) δ 8.41 (s, 1H), 8.05 (d, J = 8.7
Hz, 1H), 7.80 (s, 1H), 7.70−7.59 (m, 4H), 7.51−7.44 (m, 4H), 7.38−
7.33 (m, 1H), 2.51 (s, 3H), 2.40 (s, 3H). 13C NMR (75 MHz, CDCl3)
δ 139.2, 135.7, 135.6, 135.3, 131.3, 131.1, 130.9, 129.9, 129.6, 128.4,
127.9, 127.3, 127.2, 126.8, 125.6, 125.3, 124.8, 124.6, 20.7, 20.3. DEPT
135 (75 MHz, CDCl3) δ 131.3, 128.4, 128.3, 127.3, 126.8, 125.3,
124.8, 124.6, 20.7, 20.3. Anal. Calcd for C22H18: C, 93.57; H, 6.43.
Found: C, 93.34; H, 6.31.
(2-(3,4-Dimethylbenzoyl)phenyl(p-tolyl)methanone (4r).
Ring-opening of 3-(3,4-dimethylphenyl)isobenzofuran-1(3H)-one
with freshly prepared p-tolylmagnesium bromide followed by acidic
workup afforded benzo[c]furan 3r as a fluorescent yellow solid.
Oxidation of the benzo[c]furan 3r (1.44 g, 4.60 mmol) using LTA
(2.04 g, 4.6 mmol) following the procedure similar to that of 4a gave
diketone 4r as a pale yellow solid (1.42 g, 94%): mp 168−170 °C; 1H
NMR (300 MHz, CDCl3) δ 7.60−7.58 (m, 6H), 7.48 (s, 1H), 7.42 (d,
J = 7.8 Hz, 1H), 7.17−7.10 (m, 3H), 2.68 (s, 3H), 2.37 (s, 3H), 2.21
(s, 3H); 13C NMR (75 MHz, CDCl3) δ 196.5, 196.3, 143.8, 142.6,
140.3, 140.2, 136.7, 135.1, 134.8, 130.9, 130.1, 130.0, 129.6, 129.6,
129.0, 127.8, 21.7, 20.0, 19.6. Anal. Calcd for C23H20O2: C, 84.12; H,
6.14. Found: C, 83.96; H, 6.31.
9-(4-Methoxyphenyl)anthracene (6o). Reduction of diketone
4o (1.62 g, 4.18 mmol) using sodium borohydride (0.97 g, 25.52
mmol) followed by workup led to diol. Dipivaloylation of the diol
(1.60 g, 5.0 mmol) using pivaloyl chloride (3.01 g, 25 mmol) and
triethylamine (10.11 g, 100.0 mmol) in the presence of a catalytic
amount of DMAP (10 mg) in dry DCM (20 mL) led to the isolation
of dipivalate 5o. Dipivalate 5o (1.91 g, 3.91 mmol) upon interaction
with ZnBr2 (0.02 g, 0.13 mmol) followed by removal of solvent and
column chromatographic purification (silica gel; hexane−ethyl acetate,
99:1) led to the isolation of product 6o as a pale yellow solid (1.33 g,
1
94%): mp 148−150 °C; H NMR (300 MHz, CDCl3) δ 8.4 (s, 1H),
8.00 (d, J = 8.4 Hz, 2H), 7.70 (d, J = 8.9 Hz, 2H), 7.45−7.30 (m, 6H),
7.09 (d, J = 8.4 Hz, 2H), 3.91 (s, 3H); 13C NMR (75 MHz, CDCl3) δ
159.06, 136.9, 132.2, 131.5, 130.9, 130.6, 128.4, 127.0, 126.4, 125.3,
125.1, 55.4; DEPT 135 (75 MHz, CDCl3) δ 132.3, 128.3, 126.9, 126.4,
125.2, 125.1, 113.8, 55.4. Anal. Calcd for C21H16O: C, 88.70; H, 5.67.
Found: C, 88.49; H, 5.75.
(2-(4-Methoxylbenzoyl)phenyl(p-tolyl)methanone (4p).
Ring-opening of 3-(4-methylphenyl)isobenzofuran-1(3H)-one31 with
freshly prepared p-anisylmagnesium bromide followed by acidic
workup gave benzo[c]furan 3p as a fluorescent bright yellow solid.
Oxidation of the benzo[c]furan 3p (3 g, 9.55 mmol) using LTA (4.23
g, 9.54 mmol) following the procedure similar to that of 4a gave
9-(3,4-Dimethylphenyl)-2-methylanthracene (6r). Reduction
of diketone 4r (1.46 g, 4.45 mmol) using sodium borohydride (0.84 g,
22.16 mmol) followed by workup gave diol. Dipivaloylation of the diol
(1.29 g, 3.88 mmol) using pivaloyl chloride (2.34 g, 19.40 mmol) and
triethylamine (7.86 g, 77.67 mmol) in the presence of a catalytic
amount of DMAP (10 mg) in dry DCM (20 mL) led to the isolation
of dipivalate 5r. Dipivalate 5r (1.48 g, 2.96 mmol) upon interaction
with ZnBr2 (0.02 g, 0.13 mmol) followed by removal of solvent and
column chromatographic purification (silica gel; hexane−ethyl acetate,
99:1) gave compound 6r as a colorless solid (1.06 g, 92%): mp 100−
diketone 4p26 as a colorless solid (2.8 g, 88%): mp 165−167 °C; H
1
NMR (300 MHz, CDCl3) δ 7.68 (d, J = 9 Hz, 2H), 7.61−7.58 (m,
6H), 7.16 (d, J = 8.1 Hz, 2H), 6.84 (d, J = 8.7 Hz, 2H), 3.83 (s, 3H),
2.37 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 196.4, 195.3, 163.5,
143.8, 140.3, 140.0, 134.8, 132.2, 130.3, 130.1, 130.0, 129.9, 129.5,
129.3, 129.0, 113.6, 55.5, 21.7; DEPT 135 (75 MHz, CDCl3) δ 132.3,
130.1, 130.0, 130.0, 129.5, 129.3, 129.0, 113.6, 55.3, 21.7.
1
102 °C; H NMR (300 MHz, CDCl3) δ 8.31(s, 1H), 7.95 (d, J = 8.1
9-(4-Methoxyphenyl)-2-methylanthracene (6p). Reduction of
diketone 4p (1.6 g, 4.84 mmol) using sodium borohydride (0.92 g,
24.21 mmol) followed by workup gave diol. Dipivaloylation of the diol
(1.44 g, 4.31 mmol) using pivaloyl chloride (1.59 g, 13.18 mmol) and
triethylamine (5.35 g, 52.8 mmol) in the presence of a catalytic
amount of DMAP (10 mg) in dry DCM (20 mL) led to the isolation
dipivalate 5p. Dipivalate 5p (1.78 g, 3.54 mmol) upon interaction with
ZnBr2 (0.02 g, 0.13 mmol) followed by removal of solvent and column
chromatographic purification (silica gel; hexane−ethyl acetate, 99:1)
led to the isolation of product 6p as a colorless solid (1.1 g, 86%): mp
136−138 °C; 1H NMR (300 MHz, CDCl3) δ 8.40 (s, 1H), 8.01−7.90
(m, 2H), 7.65 (d, J = 8.7 Hz, 2H), 7.42−7.26 (m, 7H), 7.12−7.09 (m,
2H), 3.96 (s, 3H), 2.40 (s, 1H); 13C NMR (75 MHz, CDCl3) δ 158.9,
135.8, 134.9, 132.3, 131.0, 130.9, 130.7, 130.1, 129.2, 128.3, 128.2,
127.9, 126.8, 126.3, 126.1, 125.1, 125.0, 124.6, 113.8, 55.3, 22.3;
HRMS (EI) Calcd for C22H18O [M+] 298.1358, found 298.1354.
(2-Benzoylphenyl)(3,4-dimethylphenyl)methanone (4q).
Ring-opening of 3-(3,4-dimethylphenyl)isobenzofuran-1(3H)-one
with freshly prepared phenylmagnesium bromide followed by acidic
workup gave benzo[c]furan 3q as a fluorescent yellow solid. Oxidation
of the benzo[c]furan 3q (1.04 g, 3.48 mmol) using LTA (1.54 g, 3.47
mmol) following the procedure similar to that of 4a furnished
diketone 4q32a as a colorless solid (0.98 g, 90%): mp 132−134 °C; 1H
NMR (300 MHz, CDCl3) δ 8.84 (d, J = 7.2 Hz, 2H), 7.62−7.58 (m,
4H), 7.53−7.48 (m, 2H), 7.44−7.34 (m, 3H), 7.12 (d, J = 7.8 Hz,
1H), 2.27 (s, 3H), 2.21 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 196.6,
196.5, 142.7, 140.4, 139.9, 137.3, 136.8, 135.0, 132.9, 130.9, 130.3,
130.1, 129.8, 129.6, 129.6, 128.3, 127.8, 20.0, 19.7.
Hz, 1H), 7.49 (s, 1H),7.62 (d, J = 8.7 Hz, 1H), 7.41−7.24 (m, 7H),
2.51 (s, 3H), 2.42 (s, 3H), 2.31 (s, 3H); 13C NMR (75 MHz, CDCl3)
δ 136.9, 136.0, 135.8, 135.5, 135.3, 131.3, 131.2, 131.1, 130.9, 129.7,
129.1, 128.6, 128.2, 127.2, 126.9, 125.6, 125.0, 124.7, 124.5, 21.4, 20.7,
20.2; DEPT 135 (75 MHz, CDCl3) δ 131.1, 129.1, 128.3, 127.2, 126.9,
125.6, 125.0, 124.7, 124.5, 21.4, 20.7, 20.2; HRMS (EI) Calcd for
C23H20 [M+] 296.1565, found 296.1560.
(2-(3,4-Dimethoxybenzoyl)phenyl(p-tolyl)methanone (4s).
Ring-opening of 3-(3,4-dimethoxyphenyl)isobenzofuran-1(3H)-one28
with freshly prepared p-tolylmagnesium bromide followed by acidic
workup gave benzo[c]furan 3s as a fluorescent yellow solid. Oxidation
of the benzo[c]furan 3s (2.56 g, 7.44 mmol) using LTA (3.3 g, 7.44
mmol) following the procedure similar to that of 4a furnished
1
diketone 4s as a colorless solid (2.4 g, 90%): mp 162−164 °C; H
NMR (300 MHz, CDCl3) δ 7.60−7.55 (m, 6H), 7.28−7.27 (m, 1H),
7.22−7.15 (m, 3H), 6.81 (d, J = 8.4 Hz, 1H), 3.90 (s, 3H), 3.83 (s,
3H), 2.37 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 196.3, 195.4, 153.4,
149.0, 143.8, 140.2, 139.9, 134.8, 130.5, 130.3, 130.1, 129.5, 129.3,
129.0, 125.6, 111.1, 109.7, 56.1, 55.9, 21.7. Anal. Calcd for C23H20O4:
C, 76.65; H, 5.59. Found: C, 76.80; H, 5.45.
9-(3,4-Dimethoxyphenyl)-2-methylanthracene (6s). Reduc-
tion of diketone 4s (0.56 g, 1.55 mmol) using sodium borohydride
(0.29 g, 7.63 mmol) followed by workup gave diol. Dipivaloylation of
the diol (0.51 g, 1.40 mmol) using pivaloyl chloride (0.84 g, 6.96
mmol) and triethylamine (2.83 g, 27.96 mmol) in the presence of a
catalytic amount of DMAP (10 mg) in dry DCM (20 mL) led to the
isolation of dipivalate 5s. Dipivalate 5s (0.76 g, 1.42 mmol) upon
interaction with ZnBr2 (0.02 g, 0.13 mmol) followed by removal of
solvent and silica gel column chromatographic purification (hexane−
ethyl acetate, 99:1) gave compound 6s as a colorless solid (0.43 g,
9-(3,4-Dimethylphenyl)anthracene (6q). Reduction of diketone
4q (0.83 g, 2.64 mmol) using sodium borohydride (0.50 g, 13.15
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96%): mp 173−175 °C; 1H NMR (300 MHz, CDCl3) δ 8.24 (s, 1H),
7.93 (d, J = 8.4 Hz, 1H), 7.60 (d, J = 8.4 Hz, 1H), 7.39−7.35 (m, 3H),
7.31−7.24 (m, 3H), 7.20 (s, 1H), 6.87 (s, 1H), 4.02 (s, 3H), 3.75 (s,
3H), 2.50 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 149.8, 149.7, 137.0,
136.0, 135.0, 131.0, 130.7, 129.5, 129.2, 127.8, 127.1, 126.5, 124.5,
124.3, 124.0, 105.0, 104.0, 55.9, 55.6, 21.4; DEPT 135 (75 MHz,
CDCl3) δ 131.0, 129.2, 127.8, 126.5, 124.5, 124.3, 124.0, 105.0, 104.0,
56.0, 55.6, 21.4; HRMS (EI) Calcd for C23H20O2 [M+] 328.1463,
found 328.1462.
128.0, 127.4, 127.1, 127.0, 126.7, 126.4, 125.4, 124.9, 124.7, 22.3. Anal.
Calcd for C27H20: C, 94.15; H, 5.85. Found: C, 94.37; H, 5.78.
(2-Benzoylphenyl)(biphenyl-4-yl)methanone (4v). Ring-open-
ing of 3-(biphenyl-4-yl)isobenzofuran-1(3H)-one with freshly pre-
pared phenylmagnesium bromide followed by acidic workup gave
benzo[c]furan 3v as a fluorescent yellow solid. Oxidative cleavage of
the benzo[c]furan 3v (1.43 g, 4.12 mmol) using LTA (1.82 g, 4.12
mmol) adopting the procedure similar to that of 4a furnished diketone
1
4v as a pale yellow solid (1.27 g, 85%): mp 152−154 °C; H NMR
(2-(3,4-Dimethylbenzoyl)phenyl(4-methoxyphenyl)-
methanone (4t). Ring-opening of 3-(3,4-dimethylphenyl)-
isobenzofuran-1(3H)-one with freshly prepared p-anisylmagnesium
bromide followed by acidic workup gave benzo[c]furan 3t as a
fluorescent yellow solid. Oxidation of the benzo[c]furan 3t (1.44 g,
4.39 mmol) using LTA (1.94 g, 4.39 mmol) following the procedure
similar to that of 4a afforded diketone 4t30 as a colorless solid (1.44 g,
(300 MHz, CDCl3) δ 7.70 (d, J = 8.1 Hz, 2H), 7.64 (d, J = 7.2 Hz,
2H), 7.56−7.55 (m, 3H), 7.53−50 (m, 4H), 7.44−7.39 (m, 2H),7.36−
7.27 (m, 5H); 13C NMR (75 MHz, CDCl3) δ 196.6, 196.2, 145.7,
140.2, 139.9, 139.0, 137.2, 135.9, 133.0, 130.4, 130.3, 130.0, 129.8,
129.6, 128.9, 128.8, 128.4, 128.2, 127.3, 127.2, 127.0; DEPT 135 (75
MHz, CDCl3) δ 130.4, 130.3, 130.1, 129.7, 129.5, 129.1, 128.9, 128.2,
127.3, 127.0. Anal. Calcd for C26H18O2: C, 86.16; H, 5.01. Found: C,
85.87; H, 5.29.
1
96%): mp 132−134 °C; H NMR (300 MHz, CDCl3) δ 7.72−7.69
(m, 3H), 7.59−7.50 (m, 5H), 7.45−7.43 (m, 2H), 7.12 (d, J = 7.8 Hz,
1H), 6.86 (d, J = 8.7 Hz, 2H), 3.84 (s, 3H), 2.28 (s, 3H), 2.23 (s, 3H);
13C NMR (75 MHz, CDCl3) δ 196.6, 195.3, 163.5, 142.6, 140.3, 140.2,
136.7, 135.1, 132.2, 130.9, 130.3, 130.0, 129.9, 129.5, 129.3, 127.8,
113.6, 55.5, 20.0, 19.6; DEPT 135 (75 MHz, CDCl3) δ 132.2, 130.9,
130.0, 129.9, 129.5, 129.3, 127.8, 113.6, 55.5, 20.0, 19.7.
9-(Biphenyl-4-yl)anthracene (6v). Reduction of diketone 4v
(0.90 g, 2.47 mmol) using sodium borohydride (0.47 g, 12.39 mmol)
followed by workup gave diol. Dipivaloylation of the diol (0.86 g, 2.34
mmol) using pivaloyl chloride (1.41 g, 11.69 mmol) and triethylamine
(4.74 g, 46.86 mmol) in the presence of a catalytic amount of DMAP
(10 mg) in dry DCM (20 mL) led to the isolation of dipivalate 5v.
Dipivalate 5v (1.04 g, 1.94 mmol) upon interaction with ZnBr2 (0.02
g, 0.13 mmol) followed by removal of solvent and column
chromatographic purification (silica gel; hexane−ethyl acetate, 99:1)
gave compound 6v as a colorless solid (0.72 g, 94%): mp 212−213 °C;
1H NMR (300 MHz, CDCl3) δ 8.42 (s, 1H), 7.96 (d, J = 8.1 Hz, 2H),
7.74−7.66 (m, 6H), 7.45−7.26 (m, 9H); 13C NMR (75 MHz, CDCl3)
δ 140.8, 140.2, 137.7, 136.6, 131.7, 131.4, 130.2, 128.9, 127.4, 127.3,
127.0, 126.8, 126.6, 125.4, 125.1; DEPT 135 (75 MHz, CDCl3) δ
131.7, 128.9, 128.4, 127.4, 127.3, 127.0, 126.8, 126.6, 125.4, 125.1.
Anal. Calcd for C26H18: C, 94.51; H, 5.49. Found: C, 94.62; H, 5.26.
(2-(2-Methylbenzoyl)phenyl)(p-tolyl)methanone (4w). Ring-
opening of 3-(4-methylphenyl)isobenzofuran-1(3H)-one28 with
freshly prepared o-tolylmagnesium bromide followed by acidic workup
gave benzo[c]furan 3w as a fluorescent bright yellow solid. Oxidation
of the benzo[c]furan 3w (2.36 g, 7.91 mmol) using LTA (3.51 g, 7.91
mmol) following the procedure similar to that of 4a afforded diketone
4w26 as a colorless solid (2.12 g, 86%): mp 86−88 °C; 1H NMR (300
MHz, CDCl3) δ 7.45−7.43 (m, 2H), 7.36−7.25 (m, 6H), 7.14−7.13
(m, 2H), 7.06−7.03 (m, 2H), 2.39 (s, 6H); 13C NMR (75 MHz,
CDCl3) δ 190.1, 146.9, 142.7, 138.3, 136.5, 136.4, 136.3, 131.1, 130.3,
128.3, 128.0, 126.7, 125.9, 125.2, 124.2, 19.7.
9-(3,4-Dimethylphenyl)-2-methoxyanthracene (6t). Reduc-
tion of diketone 4s (0.41 g, 1.19 mmol) using sodium borohydride
(0.18 g, 4.76 mmol) followed by workup gave diol. Dipivaloylation of
the diol (0.41 g, 1.17 mmol) using pivaloyl chloride (0.71 g, 5.95
mmol) and triethylamine (2.41 g, 23.83 mmol) in the presence of a
catalytic amount of DMAP (10 mg) in dry DCM (20 mL) led to the
isolation of dipivalate 5t. Dipivalate 5t (0.69 g, 1.34 mmol) upon
interaction with ZnBr2 (0.02 g, 0.13 mmol) followed by removal of
solvent and silica gel column chromatographic purification (hexane−
ethyl acetate, 99:1) gave compound 6t as a colorless solid (0.33 g,
88%): mp 158−160 °C; 1H NMR (300 MHz, CDCl3) δ 8.18 (s, 1H),
7.86−7.81 (m, 1H), 7.62 (s, 1H), 7.86 (t, J = 8.7 Hz, 1H), 7.32−7.14
(m, 5H), 7.01−6.95 (m, 2H), 3.80 (s, 3H), 2.31 (s, 3H), 2.20 (s, 3H);
13C NMR (75 MHz, CDCl3) δ 158.9, 135.5, 135.2, 132.3, 131.2, 131.1,
130.9, 130.2, 129.9, 128.3, 127.2, 126.8, 125.6, 125.0, 124.7, 124.5,
113.8, 55.3, 20.7, 20.2; DEPT 135 (75 MHz, CDCl3) δ 132.3, 128.2,
127.2, 126.8, 125.6, 125.0, 124.7, 124.5, 113.8, 55.3, 20.7, 20.2. Anal.
Calcd for C23H20O: C, 88.43; H, 6.45. Found: C, 88.27; H, 6.41.
Biphenyl-4-yl(4-methoxybenzoyl)phenyl)methanone (4u).
Ring-opening of 3-(biphenyl-4-yl)isobenzofuran-1(3H)-one with
freshly prepared p-tolylmagnesium bromide followed by acidic workup
gave benzo[c]furan 3u as a fluorescent yellow solid. Oxidative ring
cleavage of the benzo[c]furan 3u (1.5 g, 4.15 mmol) using LTA (1.84
g, 4.15 mmol) adopting the procedure similar to that of 4a furnished
diketone 4u32b as a colorless solid (1.50 g, 96%): mp 163−165 °C; 1H
NMR (300 MHz, CDCl3) δ 7.70 (d, J = 8.4 Hz, 1H), 7.56−7.49 (m,
10H), 7.38−7.27 (m, 3H), 7.16−7.08 (m, 2H), 2.29 (s, 3H); 13C
NMR (75 MHz, CDCl3) δ 196.3, 145.7, 143.9, 140.2, 140.1, 139.9,
136.0, 135.0, 130.4, 130.3, 130.1, 129.7, 129.5, 129.1, 128.9, 128.2,
127.3, 127.0, 21.7; DEPT 135 (75 MHz, CDCl3) δ 130.4, 130.3, 130.1,
129.7, 129.5, 129.1, 128.9, 128.2, 127.3, 127.0, 21.7.
2-Phenyl-9-p-tolylanthracene (6u). Reduction of diketone 4u
(1.10 g, 2.91 mmol) using sodium borohydride (0.44 g, 11.67 mmol)
followed by workup gave diol. Dipivaloylation of the diol (1.0 g, 2.62
mmol) using pivaloyl chloride (1.58 g, 13.10 mmol) and triethylamine
(5.31 g, 52.47 mmol) in the presence of a catalytic amount of DMAP
(10 mg) in dry DCM (20 mL) led to the isolation of dipivalate 5u.
Dipivalate 5u (1.28 g, 2.33 mmol) upon interaction with ZnBr2 (0.02
g, 0.13 mmol) followed by removal of solvent and silica gel column
chromatographic purification (hexane−ethyl acetate, 99:1) gave
compound 6u as a pale yellow solid (0.86 g, 95%): mp 197−198
°C; 1H NMR (300 MHz, CDCl3) δ 8.50 (s, 1H), 8.07 (d, J = 8.1 Hz,
1H), 8.0 (d, J = 7.8 Hz, 1H), 7.87−7.81(m, 4H), 7.76 (d, J = 8.7 Hz,
1H), 7.59−7.28 (m, 8H), 2.47 (s, 3H); 13C NMR (75 MHz, CDCl3) δ
140.9, 140.0, 128.0, 135.6, 135.1, 131.7, 130.9, 130.4, 130.0, 128.9,
128.4, 128.2, 128.0, 127.4, 127.1, 127.0, 126.7, 126.4, 125.3, 124.9,
124.7, 22.2; DEPT 135 (75 MHz, CDCl3) δ 131.7, 128.9, 128.4, 128.2,
1-Methyl-10-p-tolylanthracene (6w). Reduction of diketone 4w
(1.0 g, 3.18 mmol) using sodium borohydride (0.60 g, 15.92 mmol)
followed by workup gave diol. Dipivaloylation of the diol (0.99 g, 3.11
mmol) using pivaloyl chloride (1.87 g, 15.58 mmol) and triethylamine
(6.30 g, 62.26 mmol) in the presence of a catalytic amount of DMAP
(10 mg) in dry DCM (20 mL) led to the isolation of dipivalate 5w.
Dipivalate 5w (1.22 g, 2.51 mmol) upon interaction with ZnBr2 (0.02
g, 0.13 mmol) followed by removal of solvent and column
chromatographic purification (silica gel; hexane−ethyl acetate, 99:1)
gave compound 6w as a colorless solid (0.80 g, 91%): mp 142−143
1
°C; H NMR (300 MHz, CDCl3) δ 8.6 (s, 1H), 8.05 (d, J = 8.4 Hz,
1H), 7.65 (d, J = 8.7 Hz, 1H), 7.55 (d, J = 8.7 Hz, 1H), 7.46−7.18 (m,
8H), 2.8 (s, 3H), 2.5 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 137.7,
137.0, 136.1, 134.1, 131.2, 131.0, 130.5, 130.1, 129.0, 128.7, 126.9,
125.6, 125.5, 125.3, 125.1, 125.0, 122.9, 21.4, 20.1; DEPT 135 (75
MHz, CDCl3) δ 131.2, 129.0, 128.8, 126.9, 125.6, 125.5, 125.3, 125.1,
125.0, 122.9, 21.4, 20.1; HRMS (EI) Calcd for C22H18 [M+] 282.1408,
found 282.1405.
(2-Benzoylphenyl)(2-methoxynaphthalen-1-yl)methanone
(4x). Ring-opening of 3-(2-methoxy-l-naphthyl)isobenzofuran-1(3H)-
one with freshly prepared phenylmagnesium bromide followed by
acidic workup gave benzo[c]furan 3x as a fluorescent yellow solid.
Oxidation of the benzo[c]furan 3x (1.54 g, 4.23 mmol) using LTA
(1.87 g, 3.23 mmol) adopting the procedure similar to that of 4a
furnished diketone 4x32c as a pale yellow solid (1.21 g, 88%): mp 164−
166 °C; 1H NMR (300 MHz, CDCl3) δ 7.87 (d, J = 9 Hz, 1H), 7.77−
9062
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7.75 (m, 2H), 7.64−7.59 (m, 1H), 7.55−7.52 (m, 2H), 7.47−7.42 (m,
3H), 7.37−7.28 (m, 5H), 7.19 (d, J = 9 Hz, 1H), 3.74 (s, 3H); 13C
NMR (75 MHz, CDCl3) δ 197.3, 195.7, 154.3, 140.7, 137.3, 136.6,
132.1, 131.9, 131.5, 131.2, 128.8, 128.5, 128.0, 127.4, 127.2, 126.9,
123.4, 123.3, 121.0, 112.1, 55.6.
7.17−7.11 (m, 1H), 7.32 (d, J = 8.1 Hz, 2H), 3.68 (s, 3H), 2.26 (s,
3H); 13C NMR (75 MHz, CDCl3) δ 197.7, 196.4, 155.1, 143.6, 141.5,
138.1, 134.9, 132.6, 132.3, 131.9, 131.1, 129.5, 129.4, 128.9, 128.7,
128.1, 127.9, 127.6, 124.1, 124.0, 121.8, 112.8, 56.4, 21.7. Anal. Calcd
for C26H20O3: C, 82.08; H, 5.30. Found: C, 82.35; H, 5.36.
9-(2-Methoxynapthalen-1-yl)anthracene (6x). Reduction of
diketone 4x (1.6 g, 4.87 mmol) using sodium borohydride (0.92 g,
24.39 mmol) followed by workup gave diol. Dipivaloylation of the diol
(1.67 g, 5.03 mmol) using pivaloyl chloride (3.03 g, 25.12 mmol) and
triethylamine (10.1 g, 99.8 mmol) in the presence of a catalytic
amount of DMAP (10 mg) in dry DCM (20 mL) led to the isolation
of dipivalate 5x. Dipivalate 5x (1.90 g, 3.80 mmol) upon interaction
with ZnBr2 (0.02 g, 0.13 mmol) followed by removal of solvent and
column chromatographic purification (silica gel; hexane−ethyl acetate,
99:1) gave compound 6x as a pale yellow solid (1.58 g, 95%): mp
222−224 °C; 1H NMR (300 MHz, CDCl3) δ 8.55 (s, 1H), 8.07 (d, J =
7.8 Hz, 3H), 7.90 (d, J = 8.1 Hz, 1H), 7.50 (d, J = 9 Hz, 1H), 7.44−
7.36 (m, 5H), 7.21 (t, J = 7.6 Hz, 2H), 7.09 (t, J = 7.6 Hz, 1H), 6.79
(d, J = 8.7 Hz, 1H), 3.67 (s, 3H); 13C NMR (75 MHz, CDCl3) δ
155.4, 134.6, 131.6, 131.5, 131.0, 129.9, 129.2, 128.6, 127.9, 126.8,
126.6, 125.5, 125.1, 123.7, 121.1, 114.0, 56.8; DEPT 135 (75 MHz,
CDCl3) δ 129.0, 128.6, 127.9, 126.8, 126.6, 125.6, 125.5, 125.1, 123.7,
114.0, 56.8; HRMS (EI) Calcd for C25H18O [M+] 334.1358, found
334.1354.
9-(2-Methoxynapthalen-1-yl)-2-methylanthracene (6z). Re-
duction of diketone 4z (0.85 g, 2.23 mmol) using sodium borohydride
(0.42 g, 11.05 mmol) followed by workup afforded diol.
Dipivaloylation of the diol (0.71 g, 1.84 mmol) using pivaloyl chloride
(1.12 g, 9.28 mmol) and triethylamine (3.74 g, 36.96 mmol) in the
presence of a catalytic amount of DMAP (10 mg) in dry DCM (20
mL) led to the isolation of dipivalate 5z as a thick liquid. Dipivalate 5z
(0.92 g, 1.66 mmol) upon interaction with ZnBr2 (0.02 g, 0.13 mmol)
followed by removal of solvent and column chromatographic
purification (silica gel; hexane−ethyl acetate, 99:1) gave compound
1
6z as a pale yellow solid (0.56 g, 88%): mp 184−186 °C; H NMR
(300 MHz, CDCl3) δ 8.49 (s, 1H), 8.06−8.01 (m, 2H), 7.69 (d, J =
8.9 Hz, 1H), 7.90 (d, J = 8.1 Hz, 1H), 7.51−7.47 (m, 1H), 7.40−7.34
(m, 1H), 7.32−7.23 (m, 3H), 7.20−7.15 (m, 1H), 7.11−7.06 (m, 2H),
6.82−6.80 (m, 1H), 3.63 (s, 3H), 2.27 (s, 3H); 13C NMR (75 MHz,
CDCl3) δ 155.4, 135.1, 134.6, 131.3, 131.2, 130.4, 130.3, 129.8, 129.2,
128.6, 128.5, 128.1, 127.9, 126.8, 126.6, 126.5, 125.7, 125.3, 125.0,
124.7, 124.6, 123.7, 56.8, 22.2; DEPT 135 (75 MHz, CDCl3) δ 129.8,
128.6, 128.4, 128.1, 127.9, 126.6, 126.5, 126.5, 125.7, 125.3, 125.0,
124.7, 123.7, 123.7, 56.8, 22.2. Anal. Calcd for C26H20O: C, 89.62; H,
5.79. Found: C, 89.39; H, 5.85.
(2-(2-Methoxy-1-naphthoyl)phenyl)(o-tolyl)methanone (4y).
Ring-opening of 3-(2-methoxy-l-naphthyl)isobenzofuran-1(3H)-one
with freshly prepared o-tolylmagnesium bromide followed by acidic
workup gave benzo[c]furan 3y as a fluorescent yellow solid. Oxidation
of the benzo[c]furan 3y (2.69 g, 7.39 mmol) using LTA (3.27 g, 7.39
mmol) following the procedure similar to that of 4a furnished
(2-(1-Naphthoyl)lphenyl)(phenyl)methanone (11a). Ring-
opening of 3-(phenyl)isobenzofuran-1(3H)-one with freshly prepared
1-naphthylmagnesium bromide followed by acidic workup gave
benzo[c]furan 10a as a fluorescent bright yellow solid. Oxidative
cleavage of the benzo[c]furan 10a (1 g, 3.44 mmol) using LTA (1.52
g, 3.42 mmol) following the procedure similar to that of 4a furnished
diketone 11a26 as a pale yellow solid (0.86 g, 85%): mp 128−130 °C;
1H NMR (300 MHz, CDCl3) δ 8.33−8.30 (m, 1H), 7.96 (d, J = 8.1
Hz, 1H), 7.86−7.83 (m, 1H), 7.83−7.64 (m, 5H), 7.61−7.57 (m, 3H),
7.51−7.42 (m, 3H), 7.37−7.28 (m, 2H); 13C NMR (75 MHz, CDCl3)
δ 197.5, 197.0, 141.1, 140.5, 137.3, 135.2, 133.6, 133.1, 132.8, 131.4,
131.0, 130.8, 130.5, 129.5, 129.0, 128.3, 128.1, 127.8, 126.5, 125.8,
124.0.
7-Phenyltetraphene (13a). Reduction of diketone 11a (1.0 g,
2.93 mmol) using sodium borohydride (0.56 g, 14.88 mmol) followed
by workup gave diol. Dipivaloylation of the diol (1.02 g, 3.0 mmol)
using pivaloyl chloride (1.80 g, 15.0 mmol) and triethylamine (6.07 g,
60.0 mmol) in the presence of a catalytic amount of DMAP (10 mg)
in dry DCM (20 mL) led to the isolation of dipivalate 12a as a thick
liquid. Dipivalate 12a (1.26 g, 2.48 mmol) upon interaction with
ZnBr2 (0.02 g, 0.13 mmol) followed by removal of solvent and column
chromatographic purification (silica gel; hexane−ethyl acetate, 99:1)
gave compound 13a as a yellow solid (0.80 g, 88%): mp 184−186 °C;
1H NMR (300 MHz, CDCl3) δ 9.20 (s, 1H), 8.86 (d, J = 7.8 Hz, 1H),
8.14 (d, J = 8.1 Hz, 1H), 7.70−7.50 (m, 7H), 7.47−7.45 (m, 2H),
7.43−4.40 (m, 3H); 13C NMR (75 MHz, CDCl3) δ 139.0, 137.6,
131.6, 131.5, 131.2, 130.9, 130.5, 128.7, 128.6, 1128.5, 128.4, 127.5,
127.1, 127.0, 126.9, 126.7, 125.8, 125.6, 125.5, 123.1, 121.6; DEPT 90
(75 MHz, CDCl3) δ 128.6, 128.5, 128.4, 127.5, 127.2, 126.9, 126.8,
126.7, 125.8, 125.6, 125.5. Anal. Calcd for C24H16: C, 94.70; H, 5.30.
Found: C, 94.29; H, 5.26.
(2-(1-Naphthoyl)lphenyl)(p-tolyl)methanone (11b). Ring-
opening of 3-(4-methylphenyl)isobenzofuran-1(3H)-one28 with
freshly prepared 1-naphthylmagnesium bromide followed by acidic
workup gave benzo[c]furan 10b as a fluorescent bright yellow solid.
Oxidation of the benzo[c]furan 10b (0.75 g, 2.24 mmol) using LTA
(0.99 g, 2.23 mmol) adopting the procedure similar to that of 4a
furnished diketone 11b as a pale yellow solid (0.65 g, 85%): mp 139−
140 °C (139.7−140.4 °C);26 1H NMR (300 MHz, CDCl3) δ 8.34 (d, J
= 8.4 Hz, 1H), 7.99.7.94 (m, 2H), 7.84 (d, J = 8.7 Hz, 1H), 7.73−7.28
(m, 9H), 7.08 (d, J = 7.8 Hz, 2H), 2.33 (s, 3H); 13C NMR (75 MHz,
CDCl3) δ 197.5, 196.7, 143.9, 141.2, 140.5, 135.3, 134.9, 133.6, 132.9,
131.5, 130.9, 130.8, 130.5, 130.1, 129.6, 129.0, 128.1, 127.5, 126.4,
125.8, 125.8, 124.0, 21.6.
1
diketone 4y as a colorless solid (2.49 g, 89%): mp 136−138 °C; H
NMR (300 MHz, CDCl3) δ 7.80 (d, J = 9 Hz, 1H), 7.68−7.65 (m,
1H), 7.58−7.53 (m, 1H), 7.49−7.46 (m, 1H), 7.41−7.34 (m, 2H),
7.28−7.24 (m, 1H), 7.23−7.20 (m, 2H), 7.17−7.16 (m, 1H), 7.14−
7.11 (m, 3H), 7.05−7.01 (m, 1H), 3.62 (s, 3H), 2.61 (s, 3H); 13C
NMR (75 MHz, CDCl3) δ 199.5, 196.7, 155.1, 142.7, 138.6, 135.1,
133.9, 133.4, 132.3, 131.8, 131.2, 130.9, 129.1, 128.2, 128.0, 127.9,
127.6, 126.9, 126.4, 124.0, 123.9, 123.4, 112.9, 56.4, 21.3; DEPT 135
(75 MHz, CDCl3) δ 132.3, 131.2, 130.9, 129.1, 128.2, 128.0, 127.9,
127.6, 126.9, 126.4, 124.1, 123.9, 123.4, 112.8, 56.4, 21.3. Anal. Calcd
for C26H20O3: C, 82.08; H, 5.30. Found: C, 82.35; H, 5.24.
10-(2-Methoxynaphthalen-1-yl)-1-methylanthracene (6y).
Reduction of diketone 4y (1.7 g, 4.47 mmol) using sodium
borohydride (0.68 g, 17.89 mmol) followed by workup afforded
diol. Dipivaloylation of the diol (1.65 g, 4.29 mmol) using pivaloyl
chloride (2.59 g, 21.47 mmol) and triethylamine (8.69 g, 85.87 mmol)
in the presence of a catalytic amount of DMAP (10 mg) in dry DCM
(20 mL) led to the isolation of dipivalate 5y as a thick colorless liquid.
Dipivalate 5y (1.92 g, 3.47 mmol) upon interaction with ZnBr2 (0.02
g, 0.13 mmol) followed by removal of solvent and column
chromatographic purification (silica gel; hexane−ethyl acetate, 99:1)
gave compound 6y as a colorless solid (1.32 g, 89%): mp 236−238 °C;
1H NMR (300 MHz, CDCl3) δ 8.62 (s, 1H), 8.05−7.97 (m, 2H), 7.83
(d, J = 8.1 Hz, 1H), 7.43 (d, J = 9.0 Hz, 1H), 7.35 (t, J = 7.3 Hz, 1H),
7.29−6.99 (m, 8H), 6.71 (d, J = 8.4 Hz, 1H), 3.51 (s, 3H), 2.81 (s,
3H); 13C NMR (75 MHz, CDCl3) δ 155.3, 134.6, 134.4, 132.0, 131.4,
131.2, 131.1, 130.7, 129.8, 129.1, 128.9, 127.8, 126.6, 126.4, 125.6,
125.5, 125.4, 125.2, 125.2, 125.1, 123.6, 123.2, 121.5, 114.0, 20.0;
DEPT 90 (75 MHz, CDCl3) δ 129.8, 128.9, 127.8, 126.6, 126.4, 125.6,
125.5, 125.4, 125.2, 125.2, 125.1, 123.6, 123.2, 113.9. Anal. Calcd for
C26H20O: C, 89.62; H, 5.79. Found: C, 89.31; H, 5.63.
(2-(2-Methoxy-1-naphthoyl)phenyl)(p-tolyl)methanone (4z).
Ring-opening of 3-(2-methoxy-l-naphthyl)isobenzofuran-1(3H)-one
with freshly prepared p-tolylmagnesium bromide followed by acidic
workup gave benzo[c]furan 3z as a fluorescent yellow solid. Oxidation
of the benzo[c]furan 3z (1 g, 2.74 mmol) using LTA (1.2 g, 2.7 mmol)
adopting the procedure similar to that of 4a furnished diketone 4z as a
1
colorless solid (0.98 g, 96%): mp 138−140 °C; H NMR (300 MHz,
CDCl3) δ 7.80 (d, J = 9.0 Hz, 1H), 7.67−7.64 (m, 1H), 7.56−7.54 (m,
3H), 7.51−7.46 (m, 2H), 7.38−7.33 (m, 2H), 7.25−7.22 (m, 2H),
9063
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7-p-Tolyltetraphene (13b). Reduction of diketone 11b (0.95 g,
2.79 mmol) using sodium borohydride (0.53 g, 13.94 mmol) followed
by workup afforded diol. Dipivaloylation of the diol (0.78 g, 2.26
mmol) using pivaloyl chloride (1.36 g, 11.27 mmol) and triethylamine
(4.58 g, 45.20 mmol) in the presence of a catalytic amount of DMAP
(10 mg) in dry DCM (20 mL) led to the isolation of dipivalate 12b as
a thick liquid. Dipivalate 12b (1.03 g, 2.01 mmol) upon interaction
with ZnBr2 (0.02 g, 0.13 mmol) followed by removal of solvent and
column chromatographic purification (silica gel; hexane−ethyl acetate,
99:1) gave compound 13b as a colorless solid (0.63 g, 91%): mp 114−
116 °C; 1H NMR (300 MHz, CDCl3) δ 9.24 (s, 1H), 8.88 (d, J = 8.1
Hz, 1H), 8.15 (d, J = 8.1 Hz, 1H). 7.81−7.30 (m, 12H), 2.52 (s, 3H);
13C NMR (75 MHz, CDCl3) δ 137.7, 137.1, 135.9, 131.6, 131.5, 131.1,
7-(3,4-Dimethoxyphenyl)tetraphene (13d). Reduction of
diketone 11d (1 g, 2.52 mmol) using sodium borohydride (0.47 g,
12.62 mmol) followed by workup gave diol. Dipivaloylation of the diol
(1.01 g, 2.52 mmol) using pivaloyl chloride (1.52 g, 12.62 mmol) and
triethylamine (5.11 g, 50.5 mmol) in the presence of a catalytic
amount of DMAP (10 mg) in dry DCM (20 mL) led to the isolation
of dipivalate 12d as a thick liquid. Dipivalate 12d (1.22 g, 2.14 mmol)
upon interaction with ZnBr2 (0.02 g, 0.13 mmol) followed by removal
of solvent and column chromatographic purification (silica gel;
hexane−ethyl acetate, 99:1) gave compound 13d as a colorless solid
(0.78 g, 85%): mp 168−170 °C; 1H NMR (300 MHz, CDCl3) δ 9.25
(s, 1H), 8.89 (d, J = 8.1 Hz, 1H), 8.16 (d, J = 8.4 Hz, 1H), 7.83−7.47
(m, 8H), 7.11−6.96 (m, 3H), 4.03 (s, 3H), 3.86 (s, 3H); 13C NMR
(75 MHz, CDCl3) δ 148.9, 148.4, 137.4, 131.6, 131.5, 131.4, 131.2,
130.5, 129.0, 128.6, 128.5, 127.2, 126.9, 126.8, 126.7, 125.7, 125.6,
125.5, 123.5, 123.1, 121.5, 114.4, 111.1, 56; DEPT 135 (75 MHz,
CDCl3) δ 128.6, 128.5, 127.2, 126.9, 126.8, 125.8, 125.5, 123.5, 121.5,
114.3, 111.1, 56.0; HRMS (EI) Calcd for C26H20O2 [M+] 364.1463,
found 364.1466.
(2-Benzoylphenyl)(4-methylnaphthalen-1-yl)methanone
(11e). Ring-opening of 3-(4-methyl-l-naphthyl)isobenzofuran-1(3H)-
one with freshly prepared phenylmagnesium bromide followed by
acidic workup gave benzo[c]furan 10e as a fluorescent yellow solid.
Oxidative cleavage of the benzo[c]furan 10e (1.53 g, 4.58 mmol) using
LTA (2.03 g, 4.58 mmol) following the procedure similar to that of 4a
furnished diketone 11e as a thick pale yellow liquid (1.53 g, 87%): 1H
NMR (300 MHz, CDCl3) δ 8.27 (d, J = 8.1 Hz, 1H), 7.90 (d, J = 8.1
Hz, 1H), 7.60−7.45 (m, 7H), 7.40−7.31 (m, 3H), 7.22−7.12 (m, 3H),
2.61 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 197.4, 197.1, 141.0,
140.9, 140.1, 137.4, 133.6, 133.0, 132.7, 131.2, 131.0, 130.8, 130.0,
129.5, 129.0, 128.3, 127.4, 126.4, 124.9, 124.1, 20.1. Anal. Calcd for
C25H18O2: C, 85.69; H, 5.18. Found: C, 85.34; H, 5.41.
5-Methyl-7-phenyltetraphene (13e). Reduction of diketone 11e
(1.12 g, 3.2 mmol) using sodium borohydride (0.48 g, 12.63 mmol)
followed by workup afforded diol. Dipivaloylation of the diol (1.06 g,
2.99 mmol) using pivaloyl chloride (1.80 g, 14.92 mmol) and
triethylamine (6.05 g, 59.78 mmol) in the presence of a catalytic
amount of DMAP (10 mg) in dry DCM (20 mL) led to the isolation
of dipivalate 12e as a thick liquid. Dipivalate 12e (1.28 g, 2.45 mmol)
upon interaction with ZnBr2 (0.02 g, 0.13 mmol) followed by removal
of solvent and column chromatographic purification (silica gel;
hexane−ethyl acetate, 99:1) gave compound 13e as a colorless solid
(0.91 g, 96%): mp 169−171 °C; 1H NMR (300 MHz, CDCl3) δ 9.26
(s, 1H), 8.96 (d, J = 7.8 Hz, 1H), 8.17 (d, J = 8.4 Hz, 1H), 8.02 (d, J =
7.8 Hz, 1H), 7.77−7.25 (m, 11H), 2.6 (s, 3H); 13C NMR (75 MHz,
CDCl3) δ 139.1, 136.4, 132.3, 131.9, 131.2, 131.1, 131.0, 130.6, 128.6,
128.4, 128.3, 127.4, 127.1, 126.6, 126.5, 125.6, 125.1, 124.9, 124.7,
123.3, 121.4, 20.5; DEPT 135 (75 MHz, CDCl3) δ 131.2, 128.6, 128.4,
127.4, 126.6, 126.5, 125.6, 125.2, 125.1, 124.7, 123.3, 121.4, 20.5. Anal.
Calcd for C25H18: C, 94.30; H, 5.70. Found: C, 94.01; H, 5.64.
5-Methyl-7-p-tolyltetraphene (13f). Ring-opening of 3-(4-
methyl-l-naphthyl)isobenzofuran-1(3H)-one with freshly prepared p-
tolylmagnesium bromide followed by acidic workup gave benzo[c]-
furan 10f as a fluorescent yellow solid. Oxidation of the benzo[c]furan
10f (0.63 g, 1.82 mmol) with LTA (0.80 g, 1.82 mmol) using the
procedure similar to that of 4a furnished diketone 11f as a thick liquid
(0.56 g, 85%). Reduction of the diketone 11f (0.40 g, 1.10 mmol)
using sodium borohydride (0.17 g, 4.47 mmol) followed by workup
gave diol. Dipivaloylation of the diol (0.37 g, 1.01 mmol) using
pivaloyl chloride (0.69 g, 5.04 mmol) and triethylamine (2.04 g, 20.16
mmol) in the presence of a catalytic amount of DMAP (10 mg) in dry
DCM (20 mL) led to the isolation of dipivalate 12f as a thick liquid.
Dipivalate 12f (0.54 g, 1.01 mmol) upon interaction with ZnBr2 (0.02
g, 0.13 mmol) followed by removal of solvent and column
chromatographic purification (silica gel; hexane−ethyl acetate, 99:1)
gave compound 13f as a colorless solid (0.27 g, 82%): mp 178−180
°C; 1H NMR (300 MHz, CDCl3) δ 9.25 (s, 1H), 8.97 (d, J = 7.8 Hz,
1H), 8.18 (d, J = 8.1 Hz, 1H), 8.03 (d, J = 7.5 Hz, 1H), 7.78−7.68 (m,
3H), 7.56 (t, J = 7.5 Hz, 1H), 7.47−7.37 (m, 6H), 2.62 (s, 3H), 2.6 (s,
3H); 13C NMR (75 MHz, CDCl3) δ 137.0, 136.5, 136.0, 132.2, 132.0,
131, 130.5, 129.1, 128.8, 128.6, 128.5, 127.1, 126.9, 126.8, 126.7, 125.7,
125.6, 125.5, 123.1, 121.4, 21.4; DEPT 135 (75 MHz, CDCl3) δ 131.1,
129.1, 128.6, 128.5, 127.1, 126.9, 126.8, 126.7, 125.7, 125.6, 125.4,
123.1, 123.1, 21.4; HRMS (EI) Calcd for C25H18 [M+] 318.1409,
found 318.1409.
(2-(1-Naphthoyl)lphenyl)(2,4-dimethylphenyl)methanone
(11c). Ring-opening of 3-(2,4-dimethylphenyl)isobenzofuran-1(3H)-
one with freshly prepared 1-naphthylmagnesium bromide followed by
acidic workup gave benzo[c]furan 10c as a fluorescent yellow solid.
Oxidative cleavage of the benzo[c]furan 7c (2.43 g, 6.98 mmol) using
LTA (3.1 g, 6.99 mmol) adopting the procedure similar to that of 4a
furnished diketone 11c as a pale yellow solid (2.26 g, 89%): mp 88−90
1
°C; H NMR (300 MHz, CDCl3) δ 8.22 (d, J = 8.4 Hz, 1H), 7.91−
7.79 (m, 3H), 7.62−7.60 (m, 4H), 7.50−7.31 (m, 3H), 7.13 (d, J = 7.8
Hz, 1H), 6.89 (d, J = 7.5 Hz, 1H), 6.70 (s, 1H), 2.33 (s, 3H), 1.97 (s,
3H); 13C NMR (75 MHz, CDCl3) δ 198.0, 197.9, 142.2, 141.6, 141.1,
139.9, 135.4, 133.8, 133.0, 132.5, 131.6, 131.1, 130.9, 130.6, 130.2,
129.7, 128.0, 127.5, 126.5, 126.30, 125.7, 124.0, 21.3, 20.4; DEPT
135(75 MHz, CDCl3) δ 133.0, 132.5, 131.7, 131.1, 131.0, 130.2, 129.7,
128.0, 127.5, 126.5, 126.0, 125.7, 124.0, 21.3, 20.4. Anal. Calcd for
C26H20O2: C, 85.69; H, 5.53. Found: C, 85.38; H, 5.32.
7-(2,4-Dimethylphenyl)tetraphene (13c). Reduction of dike-
tone 11c (1.69 g, 4.18 mmol) using sodium borohydride (0.88 g, 21.0
mmol) followed by workup gave diol. Dipivaloylation of the diol (1.69
g, 4.59 mmol) using pivaloyl chloride (2.76 g, 22.88 mmol) and
triethylamine (9.29 g, 91.80 mmol) in the presence of a catalytic
amount of DMAP (10 mg) in dry DCM (20 mL) led to the isolation
of dipivalate 12c as a thick liquid. Dipivalate 12c (1.86 g, 3.47 mmol)
upon interaction with ZnBr2 (0.02 g, 0.13 mmol) followed by removal
of solvent and column chromatographic purification (silica gel;
hexane−ethyl acetate, 99:1) gave compound 13c as a colorless solid
(1.25 g, 81%): mp 97−98 °C; 1H NMR (300 MHz, CDCl3) δ 9.24 (s,
1H), 8.89 (d, J = 8.1 Hz, 1H), 8.16 (d, J = 8.4 Hz, 1H), 7.80 (d, J = 7.5
Hz, 1H), 7.68−7.59 (m, 2H), 7.55−7.47 (m, 3H), 7.42−7.35 (m, 2H),
7.26−7.14 (m, 3H), 2.49 (s, 3H), 1.84 (s, 3H); 13C NMR (75 MHz,
CDCl3) δ 137.6, 137.4, 137.0, 135.2, 131.7, 131.6, 131.0, 130.8, 128.7,
128.6, 128.5, 127.1, 126.9, 126.8, 126.6, 126.4, 125.89, 125.5, 125.4,
123.0, 121.3, 21.3, 19.7; DEPT 135 (75 MHz, CDCl3) δ 131.0, 130.8,
128.7, 128.5, 127.1, 127.0, 126.9, 126.6, 126.5, 125.8, 125.5, 125.4,
123.1, 121.3, 21.3, 19.7; HRMS (EI) Calcd for C26H20 [M+] 332.1565,
found 332.1568.
(2-(1-Naphthoyl)lphenyl)(3,4-dimethoxylphenyl)methanone
(11d). Ring-opening of 3-(3,4-dimethoxyphenyl)isobenzofuran-
1(3H)-one28 with freshly prepared 1-naphthylmagnesium bromide
followed by acidic workup afforded benzo[c]furan 10d as a fluorescent
yellow solid. Oxidation of the benzo[c]furan 10d (2.6 g, 6.84 mmol)
using LTA (3.03 g, 6.83 mmol) adopting the procedure similar to that
of 4a furnished diketone 11d as a brown solid (2.35, 87%): mp 122−
124 °C; 1H NMR (300 MHz, CDCl3) δ 8.19 (d, J = 8.4 Hz, 1H), 7.91
(d, J = 8.4 Hz, 1H), 7.81−7.73 (m, 2H), 7.66−7.57 (m, 3H), 7.48−
7.35 (m, 4H), 7.06−7.03 (m, 1H), 6.97 (s, 1H), 6.67 (d, J = 8.4 Hz,
1H), 3.86 (s, 3H), 3.65 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 197.6,
195.6, 153.2, 149.0, 141.0, 140.5, 135.3, 133.5, 132.9, 131.5, 131.0,
130.8, 130.4, 130.1, 128.9, 127.9, 127.5, 126.5, 125.8, 125.5, 125.3,
124.0, 110.0, 109.7, 56.0, 55.7; HRMS (EI) Calcd for C26H20O4 [M+]
396.1362, found 396.1355.
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131.2, 130.6, 129.1, 128.7, 128.6, 128.3, 127.1, 126.7, 126.6, 125.5,
125.1, 125.0, 124.7, 123.4, 121.3, 21.4, 20.5; DEPT 135 (75 MHz,
CDCl3) δ 131.2, 129.1, 128.6, 127.1, 126.7, 126.6, 125.5, 125.1, 125.0,
124.7, 123.4, 121.3, 21.4, 20.5. Anal. Calcd for C26H20: C, 93.94; H,
6.06. Found: C, 93.62; H, 5.98.
= 8.4 Hz, 1H), 3.63 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 155.4,
134.6, 132.0, 131.8, 131.5, 130.9, 129.9, 129.8, 129.2, 128.8, 128.5,
127.9, 127.1, 127.0, 126.8, 126.7, 126.4, 125.9, 125.6, 123.8, 123.1,
121.8, 121.3, 114.0, 56.8; DEPT 135 (75 MHz, CDCl3) δ 130.0, 128.9,
128.5, 127.9, 127.1, 127.0, 126.9, 126.7, 126.4, 125.9, 125.6, 123.8,
123.0, 121.9, 114.0, 56.8; HRMS (EI) Calcd for C29H20O [M+]
384.1514, found 384.1520.
(2-(4-Methoxybenzoyl)phenyl)(4-methylnaphthalen-1-yl)-
methanone (11g). Ring-opening of 3-(4-methyl-l-naphthyl)-
isobenzofuran-1(3H)-one with freshly prepared p-anisylmagnesium
bromide followed by acidic workup gave benzo[c]furan 10g as a
fluorescent yellow solid. Oxidation of the benzo[c]furan 10g (1.99 g,
5.42 mmol) using LTA (2.40 g, 5.42 mmol) adopting the procedure
similar to that of 4a furnished diketone 11g as a thick liquid (1.82 g,
(2-(1-Naphthoyl)phenyl)(4-methylnaphthalen-1-yl)-
methanone (11i). Ring-opening of 3-(4-methyl-l-naphthyl)-
isobenzofuran-1(3H)-one with freshly prepared 1-naphthylmagnesium
bromide followed by acidic workup furnished benzo[c]furan 10i as a
fluorescent yellow solid. Oxidation of the benzo[c]furan 10i (1.99 g,
5.16 mmol) using LTA (2.29 g, 5.16 mmol) adopting the procedure
similar to that of 4a afforded diketone 11i as a thick liquid (1.76 g,
1
88%): H NMR (300 MHz, CDCl3) δ 8.25 (d, J = 8.4 Hz, 1H), 7.88
(d, J = 8.1 Hz, 1H), 7.59−7.51 (m, 1H), 7.48−7.42 (m, 5H), 7.35−
7.32 (m, 2H), 7.13−7.10 (m, 1H), 6.87−6.84 (m, 1H), 6.62 (d, J = 8.7
Hz, 2H), 3.68 (s, 3H), 2.60 (s, 3H); 13C NMR (75 MHz, CDCl3) δ
197.5, 195.7, 163.4, 141.2, 140.7, 140.1, 133.7, 132.7, 131.8, 131.2,
131.0, 130.9, 130.6, 129.9, 128.8, 127.7, 127.2, 126.4, 126.3, 124.9,
124.0, 114.2, 113.5, 55.4, 20.1. Anal. Calcd for C26H20O3: C, 82.08; H,
5.30. Found: C, 82.34; H, 5.11.
1
85%): H NMR (300 MHz, CDCl3) δ 8.42 (d, J = 8.4 Hz, 1H), 7.97
(d, J = 8.4 Hz, 1H), 7.73−7.49 (m, 7H), 7.39−7.32 (m, 1H), 7.29−
7.08 (m, 7H), 2.51 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 197.8,
197.7, 141.7, 141.5, 140.4, 135.4, 133.8, 133.7, 133.2, 132.8, 131.3,
131.1, 131.0, 130.9, 130.7, 130.2, 130.1, 127.9, 127.4, 127.4, 126.2,
126.0, 125.5, 124.7, 123.8, 123.7, 20.1. DEPT 135 (75 MHz, CDCl3) δ
133.2, 131.3, 131.1, 131.0, 130.9, 130.2, 127.9, 127.4, 127.4, 126.2,
126.1, 126.0, 125.5, 124.7, 123.8, 20.1; HRMS (EI) Calcd for
C29H20O2 [M+] 400.1463, found 400.1466.
7-(4-Methoxyphenyl)-5-methyltetraphene (13g). Reduction
of diketone 11g (1.68 g, 4.38 mmol) using sodium borohydride
(0.66 g, 17.36 mmol) followed by workup gave diol. Dipivaloylation of
the diol (1.58 g, 4.08 mmol) using pivaloyl chloride (2.46 g, 20.40
mmol) and triethylamine (8.56 g, 81.62 mmol) in the presence of a
catalytic amount of DMAP (10 mg) in dry DCM (20 mL) led to the
isolation of dipivalate 12g as a thick liquid. Dipivalate 12g (1.92 g, 3.45
mmol) upon interaction with ZnBr2 (0.02 g, 0.13 mmol) followed by
removal of solvent and column chromatographic purification (silica
gel; hexane−ethyl acetate, 99:1) gave compound 13g as a colorless
solid (1.30 g, 91%): mp 181−183 °C ; 1H NMR (300 MHz, CDCl3) δ
9.13 (s, 1H), 8.85 (d, J = 8.1 Hz, 1H), 8.06 (d, J = 8.4 Hz, 1H), 7.91
(d, J = 7.5 Hz, 1H), 7.65−7.55 (m, 3H), 7.45−7.25 (m, 5H), 7.17−
7.04 (m, 2H), 3.88 (s, 3H), 2.50 (s, 3H); 13C NMR (75 MHz, CDCl3)
δ 158.9, 136.2, 132.3, 132.2, 132.0, 131.4, 131.1, 130.6, 128.9, 128.6,
128.3, 127.1, 126.6, 125.5, 125.1, 125.0, 124.6, 123.3, 121.2, 113.8,
55.3, 20.5; HRMS (EI) Calcd for C26H20O [M+] 348.1514, found
348.1518.
(2-(1-Naphthoyl)phenyl)(2-methoxynaphthalen-1-yl)-
methanone (11h). Ring-opening of 3-(2-methoxy-l-naphthyl)-
isobenzofuran-1(3H)-one with freshly prepared 1-naphthylmagnesium
bromide followed by acidic workup afforded benzo[c]furan 10h as a
fluorescent bright yellow solid. Oxidative cleavage of the benzo[c]furan
10h (2.31 g, 5.76 mmol) using LTA (2.55 g, 5.75 mmol) following the
procedure similar to that of 4a gave diketone 11h32d as a colorless
solid (2.13 g, 89%): mp 226−228 °C; 1H NMR (300 MHz, CDCl3) δ
9.06 (d, J = 8.1 Hz, 1H), 7.90 (d, J = 8.1 Hz, 1H), 7.81−7.76 (m, 2H),
7.66−7.65 (m, 3H), 7.63−7.60 (m, 1H), 7.53−7.44 (m, 4H), 7.35−
7.32 (m, 2H), 7.22−7.19 (m, 2H), 7.17−7.13 (m, 1H), 3.67 (s, 3H);
13C NMR (75 MHz, CDCl3) δ 199.5, 196.7, 155.1, 142.7, 138.6, 135.1,
Preparation of Annulated Compounds (13i) and (13i′).
Reduction of diketone 11i (1.35 g, 3.36 mmol) using sodium
borohydride (0.51 g, 13.42 mmol) followed by workup gave diol.
Dipivaloylation of the diol (1.28 g, 3.16 mmol) using pivaloyl chloride
(1.90 g, 15.75 mmol) and triethylamine (6.39 g, 63.14 mmol) in the
presence of a catalytic amount of DMAP (10 mg) in dry DCM (20
mL) led to the isolation of dipivalate 12i as a thick liquid. Dipivalate
12i (1.41 g, 2.46 mmol) upon interaction with ZnBr2 (0.02 g, 0.13
mmol) followed by removal of solvent and column chromatographic
purification (silica gel; hexane−ethyl acetate, 99:1) gave an inseparable
1:1 mixture of compound 13i and 13i′ as colorless solid (0.99 g, 85%):
1
mp 148−150 °C; H NMR (300 MHz, CDCl3) δ 9.33 (s, 1H), 8.93
(d, J = 8.4 Hz, 1H), 8.20−8.13 (m, 2H), 8.06−7.94 (m, 1H), 7.77−
7.69 (m, 3H), 7.67−7.64 (m, 1H), 7.53−7.51 (m, 3H), 7.43−7.39 (m,
3H), 7.35−7.22 (m, 4H), 7.18−7.07 (m, 3H), 2.87 (s, 3H), 2.42 (s,
3H); 13C NMR (75 MHz, CDCl3) δ 133.6, 132.8, 132.7, 131.8, 131.7,
131.6, 130.6, 129.7, 129.6, 129.1, 128.8, 128.6, 128.5, 128.4, 128.2,
128.1, 127.2, 127.0, 126.9, 126.9, 126.7, 126.6, 126.4, 126.3, 125.9,
125.8, 125.6, 125.5, 125.2, 125.0, 124.8, 124.4, 123.4, 123.1, 121.8,
20.4, 19.7; HRMS (EI) Calcd for C29H20 [M+] 368.1565, found
368.1567.
9-(9,9-Dihexyl-9H-fluoren-2-yl)anthracene (13j). Ring-opening
of 3-(9,9-dihexyl-9H-fluoren-2-yl)isobenzofuran-1(3H)-one33a with
freshly prepared phenylmagnesium bromide followed by acidic workup
gave benzo[c]furan 10j as a fluorescent yellow solid. Oxidative
cleavage of the benzo[c]furan 10j (1 g, 1.84 mmol) using LTA (0.81 g,
1.84 mmol) adopting the procedure similar to that of 4a furnished
diketone 11j as a thick liquid (0.87 g, 85%). Reduction of the diketone
11j (0.62 g, 1.11 mmol) using sodium borohydride (0.21 g, 5.57
mmol) followed by workup gave diol. Dipivaloylation of the diol (0.65
g, 1.16 mmol) using pivaloyl chloride (0.69 g, 13.18 mmol) and
triethylamine (2.34 g, 23.21 mmol) in the presence of a catalytic
amount of DMAP (10 mg) in dry DCM (20 mL) led to the isolation
of dipivalate 12j as a thick liquid. Dipivalate 12j (0.79 g, 1.08 mmol)
upon interaction with ZnBr2 (0.02 g, 0.13 mmol) followed by removal
of solvent and column chromatographic purification (silica gel;
hexane−ethyl acetate, 99:1) gave compound 13j as a pale yellow
solid (0.43 g, 71%): mp 148−150 °C; 1H NMR (300 MHz, CDCl3) δ
8.43 (s, 1H), 7.98 (d, J = 8.4 Hz, 2H), 7.82 (d, J = 7.5 Hz, 1H), 7.75−
7.72 (m, 1H), 7.67 (d, J = 8.7 Hz, 2H), 7.41−7.36 (m, 2H), 7.33−7.28
(m, 5H), 7.23−7.17 (m, 1H), 1.94−1.87 (m, 4H), 1.06−1.01 (m,
12H), 0.71−0.66 (m, 10H); 13C NMR (75 MHz, CDCl3) δ 151.0,
150.8, 141.0, 140.5, 137.7, 137.4, 131.4, 130.4, 129.8, 128.4, 127.2,
126.9, 126.4, 126.0, 125.3, 125.1, 122.9, 119.8, 119.6, 55.2, 40.4, 31.5,
29.7, 23.9, 22.5, 14.0; DEPT 135 (75 MHz, CDCl3) δ 129.8, 128.4,
127.2, 126.9, 126.4, 126.0, 125.3, 125.1, 122.9, 119.8, 119.6, 40.4, 31.5,
133.9, 133.4, 132.3, 131.8, 131.4, 131.2, 130.9, 129.9, 129.1, 128.7,
128.2, 128.0, 127.9, 127.6, 126.9, 126.4, 124.0, 123.9, 123.4, 121.9,
112.9, 56.4; DEPT 135 (75 MHz, CDCl3) δ 133.3, 132.4, 132.3, 131.2,
130.9, 129.9, 129.1, 128.2, 128.0, 127.9, 127.6, 126.9, 126.4, 124.1,
123.9, 123.4, 112.8, 56.4.
7-(2-Methoxynapthalen-1-yl)tetraphene (13h). Reduction of
diketone 11h (1.0 g, 2.39 mmol) using sodium borohydride (0.45 g,
11.99 mmol) followed by workup afforded diol. Dipivaloylation of the
diol (1.0 g, 2.38 mmol) using pivaloyl chloride (1.43 g, 11.87 mmol)
and triethylamine (4.80 g, 47.50 mmol) in the presence of a catalytic
amount of DMAP (10 mg) in dry DCM (20 mL) led to the isolation
of dipivalate 12h as a thick liquid. Dipivalate 12h (1.29 g, 2.19 mmol)
upon interaction with ZnBr2 (0.02 g, 0.13 mmol) followed by removal
of solvent and column chromatographic purification (silica gel;
hexane−ethyl acetate, 99:1) gave compound 13h as a colorless solid
(0.78 g, 86%): mp 202−204 °C; 1H NMR (300 MHz, CDCl3) δ 9.33
(s, 1H), 8.93 (d, J = 8.4 Hz, 1H), 8.20 (d, J = 8.1 Hz, 1H), 8.08 (d, J =
9.0 Hz, 1H), 7.92 (d, J = 8.4 Hz, 1H), 7.77−7.16 (m, 1H), 7.69−7.66
(m, 1H), 7.58−7.55 (m, 1H), 7.54−7.49 (m, 2H), 7.40−7.33 (m, 2H),
7.32−7.27 (m, 2H), 7.23−7.20 (m, 1H), 7.13−7.08 (m, 1H), 6.85 (d, J
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29.7, 23.9, 22.5, 14.0; HRMS (EI) Calcd for C39H42 [M+] 510.3287,
found 510.3273.
DEPT 135 (75 MHz, CDCl3) δ 130.1, 128.9, 128.7, 128.2, 127.7,
126.0, 125.1, 125.0, 124.5, 122.6, 122.0, 119.6. Anal. Calcd for
C22H14S: C, 85.12; H, 4.55; S, 10.33. Found: C, 84.97; H, 4.63; S,
10.12.
(9,9-Dihexyl-9H-fluoren-3-yl)(2-(4-methylbenzoyl)phenyl)-
methanone (11k). Ring-opening of 3-(9,9-dihexyl-9H-fluoren-2-
yl)isobenzofuran-1(3H)-one33a with freshly prepared p-tolylmagnesi-
um bromide followed by acidic workup gave benzo[c]furan 10k as a
thick orange liquid. Oxidative cleavage of the benzo[c]furan 10k (1 g,
1.79 mmol) using LTA (0.79 g, 1.79 mmol) following the procedure
similar to that of 4a furnished diketone 11k30 as a thick orange liquid
Benzo[b]thiophen-3-yl(2-(4-methylbenzoyl)phenyl)-
methanone (11m). Ring-opening of 3-(benzo[b]thiophen-3-yl)-
isobenzofuran-1(3H)-one33b with freshly prepared p-tolylmagnesium
bromide followed by acidic workup gave benzo[c]furan 10m as a
fluorescent yellow solid. Oxidative ring-opening of the benzo[c]furan
10m (1.48 g, 4.35 mmol) using LTA (1.92 g, 4.33 mmol) adopting the
procedure similar to that of 4a furnished diketone 11m as a thick pale
yellow liquid (1.30 g, 85%): 1H NMR (300 MHz, CDCl3) δ 8.25−8.22
(m, 1H), 7.74 (s, 1H), 7.70−7.62 (m, 2H), 7.53 −7.50 (m, 3H), 7.40
(d, J = 8.4 Hz, 2H), 7.28−7.24 (m, 2H), 6.94 (d, J = 8.1 Hz, 2H), 2.18
(s, 3H); 13C NMR (75 MHz, CDCl3) δ 196.3, 190.6, 143.8, 140.8,
140.0, 139.7, 139.3, 136.5, 135.8, 134.7, 130.6, 130.4, 129.5 (2C),
129.3, 128.8, 125.4, 125.3, 125.0, 121.9, 21.5; HRMS (EI) Calcd for
C23H16O2S [M+] 356.0871, found 356.0870.
1
(0.90 g, 88%): H NMR (300 MHz, CDCl3) δ 7.64−7.53 (m, 10H),
7.28−7.25 (m, 3H), 7.06 (d, J = 7.5 Hz, 2H), 2.27 (s, 3H), 1.87−1.82
(m, 4H), 1.04−0.95 (m, 12H), 0.70−0.44 (m, 10H); 13C NMR (75
MHz, CDCl3) δ 196.5, 196.3, 152.1, 150.8, 146.0, 143.8, 140.43, 140.2,
139.8, 135.8, 134.8, 130.3, 130.1, 129.7, 129.4, 129.0, 128.4, 127.0,
124.0, 123.1, 120.7, 119.2, 55.2, 40.1, 31.5, 29.6, 23.7, 22.6, 21.6, 14.0;
DEPT 135 (75 MHz, CDCl3) δ 130.3, 130.1, 130.0, 129.7, 129.4,
129.0, 128.4, 127.0, 124.0, 123.1, 120.7, 119.2, 40.1, 31.5, 29.6, 23.7,
22.6, 21.6, 14.0.
9-(9,9-Dihexyl-9H-fluoren-2-yl)-2-methylanthracene (13k).
Reduction of diketone 11k (0.66 g, 1.15 mmol) using sodium
borohydride (0.21 g, 5.76 mmol) followed by workup gave diol.
Dipivaloylation of the diol (0.68 g, 1.07 mmol) using pivaloyl chloride
(0.71 g, 5.90 mmol) and triethylamine (2.38 g, 23.31 mmol) in the
presence of a catalytic amount of DMAP (10 mg) in dry DCM (20
mL) led to the isolation of dipivalate 12k as a thick liquid. Dipivalate
12k (0.84 g, 1.12 mmol) upon interaction with ZnBr2 (0.02 g, 0.13
mmol) followed by removal of solvent and column chromatographic
purification (silica gel; hexane−ethyl acetate, 99:1) gave compound
13k as a thick red liquid (0.46 g, 73%): 1H NMR (300 MHz, CDCl3)
δ 8.53 (s, 1H), 8.10 (d, J = 8.4 Hz, 1H), 8.05−7.98 (m, 2H), 7.90 (d, J
= 6.6 Hz, 1H), 7.82 (d, J = 8.7 Hz, 1H), 7.58 (s, 1H), 7.54−7.43 (m,
6H), 7.48−7.38 (m, 2H), 2.47 (s, 3H), 2.12−2.04 (m, 3H), 1.25−1.17
(m, 11H), 0.88−0.82 (m, 10H); 13C NMR (75 MHz, CDCl3) δ 151.0,
150.8, 141.1, 140.5, 137.7, 136.6, 135.0, 131.0, 130.7, 130.6, 130.1,
129.9, 128.5, 128.3, 128.0, 127.2, 127.0, 126.9, 126.3, 126.1, 125.3,
125.2, 124.8, 122.9, 119.8, 119.7, 55.29, 40.6, 31.78, 31.6, 29.9, 29.7,
27.0, 24.0, 23.9, 22.8, 22.7, 22.6, 22.3, 14.1; DEPT 135 (75 MHz,
CDCl3) δ 129.9, 128.5, 128.3, 128.0, 127.2, 127.0, 126.9, 126.3, 126.1,
125.3, 125.2, 124.8, 122.9, 119.8, 119.7, 40.6, 31.7, 31.6, 29.9, 29.7,
27.0, 24.1, 23.9, 22.7, 22.6, 22.3, 14.2; HRMS (EI) Calcd for C40H44
[M+] 524.3443, found 524.3439.
6-p-Tolylbenzo[b]naptho[2,3-d]thiophene (13m). Reduction
of diketone 11m (0.85 g, 2.38 mmol) using sodium borohydride (0.49
g, 12.89 mmol) followed by workup gave diol. Dipivaloylation of the
diol (0.77 g, 2.31 mmol) using pivaloyl chloride (1.39 g, 11.52 mmol)
and triethylamine (4.69 g, 45.20 mmol) in the presence of a catalytic
amount of DMAP (10 mg) in dry DCM (20 mL) led to the isolation
of dipivalate 12m as a thick liquid. Dipivalate 12m (0.98 g, 1.96 mmol)
upon interaction with ZnBr2 (0.02 g, 0.13 mmol) followed by removal
of solvent and column chromatographic purification (silica gel;
hexane−ethyl acetate, 99:1) gave compound 13m as a pale green
solid (0.53 g, 78%): mp 118−120 °C; 1H NMR (300 MHz, CDCl3) δ
8.65 (s, 1H), 8.32−8.29 (m, 1H), 8.11 (d, J = 8.1 Hz, 1H), 7.86 (d, J =
8.4 Hz, 1H), 7.80−7.77 (m, 1H), 7.58−7.44 (m, 8H), 2.56 (s, 3H);
13C NMR (75 MHz, CDCl3) δ 140.6, 138.7, 138.0, 136.0, 135.7, 134.6,
133.2, 131.6, 131.1, 129.9, 129.7, 128.7, 127.6, 125.9, 125.1, 125.0,
124.5, 122.7, 122.0, 119.5, 21.5; DEPT 135 (75 MHz, CDCl3) δ 129.9,
129.7, 128.7, 125.9, 125.1, 125.0, 124.5, 122.7, 122.0, 119.5, 21.5. Anal.
Calcd for C23H16S: C, 85.15; H, 4.97; S, 9.88. Found: C, 84.85; H,
4.88; S, 9.98.
Benzo[b]thiophen-3-yl(2-(4-methoxybenzoyl)phenyl)-
methanone (11n). Ring-opening of 3-(benzo[b]thiophen-3-yl)-
isobenzofuran-1(3H)-one33b with freshly prepared p-anisylmagnesium
bromide followed by acidic workup afforded benzo[c]furan 10n as a
fluorescent yellow solid. Oxidation of the benzo[c]furan 10n (1.32 g,
4.02 mmol) using LTA (1.78 g, 4.2 mmol) following the procedure
similar to that of 4a furnished diketone 11n as a colorless solid (1.08 g,
Benzo[b]thiophen-3-yl(2-benzoylphenyl)methanone (11l).
Ring-opening of 3-(benzo[b]thiophen-3-yl)isobenzofuran-1(3H)-
one33b with freshly prepared phenylmagnesium bromide followed by
acidic workup afforded benzo[c]furan 10l as a fluorescent yellow solid.
Oxidation of the benzo[c]furan 10l (1.31 g, 4.01 mmol) using LTA
(1.78 g, 4.01 mmol) adopting the procedure similar to that of 4a
furnished diketone 11l as a pale yellow solid (1.16 g, 85%): mp 139−
1
92%): mp 118−120 °C; H NMR (300 MHz, CDCl3) δ 8.28−8.25
(m, 1H), 7.77 (s, 1H), 7.74−7.71 (m, 1H), 7.69−7.66 (m, 1H), 7.56−
7.55 (m, 3H), 7.50 (d, J = 9.0 Hz, 2H), 7.30−7.27 (m, 2H), 6.66 (d, J
= 8.7 Hz, 2H), 3.70 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 195.4,
190.8, 163.5, 140.8, 140.3, 139.8, 139.5, 136.7, 135.9, 131.9, 130.7,
130.5, 130.3, 129.4, 129.3, 125.5, 125.4, 125.1, 122.0, 113.5, 55.4. Anal.
Calcd for C23H16O3S: C, 74.17; H, 4.33; S, 8.61. Found: C, 73.96; H,
4.62; S 8.60.
1
140 °C; H NMR (300 MHz, CDCl3) δ 8.29−8.26 (m, 1H), 7.79 (s,
1H), 7.73−7.70 (m, 1H), 7.68 −7.61 (m, 1H), 7.56−7.55 (m, 4H),
7.53 (s, 1H), 7.33−7.27 (m, 3H), 7.22−7.17 (m, 2H); 13C NMR (75
MHz, CDCl3) δ 196.6, 190.2, 141.0, 139.9, 139.8, 139.6, 137.3, 136.6,
133.1, 130.7, 130.6, 129.9, 129.7, 129.6, 129.4, 128.4, 128.3, 125.6,
125.2, 122.0. Anal. Calcd for C22H14O2S: C, 77.17; H, 4.12; S, 9.36.
Found: C, 76.98; H, 4.39; S, 9.27.
6-(4-Methoxyphenyl)benzo[b]naptho[2,3-d]thiophene
(13n). Reduction of diketone 11n (0.90 g, 2.61 mmol) using sodium
borohydride (0.61 g, 16.14 mmol) followed by workup gave diol.
Dipivaloylation of the diol (0.72 g, 2.31 mmol) using pivaloyl chloride
(1.24 g, 10.28 mmol) and triethylamine (4.18 g, 41.3 mmol) in the
presence of a catalytic amount of DMAP (10 mg) in dry DCM (20
mL) led to the isolation of dipivalate 12n as a thick liquid. Dipivalate
12n (0.95 g, 3.16 mmol) upon interaction with ZnBr2 (0.02 g, 0.13
mmol) followed by removal of solvent and column chromatographic
purification (silica gel; hexane−ethyl acetate, 99:1) gave compound
6-Phenylbenzo[b]naptho[2,3-d]thiophene (13l). Reduction of
diketone 11l (0.73 g, 2.13 mmol) using sodium borohydride (0.32 g,
8.42 mmol) followed by workup afforded diol. Dipivaloylation of the
diol (0.72 g, 2.08 mmol) using pivaloyl chloride (1.25 g, 10.36 mmol)
and triethylamine (4.21 g, 41.61 mmol) in the presence of a catalytic
amount of DMAP (10 mg) in dry DCM (20 mL) led to the isolation
of dipivalate 12l as a thick liquid. Dipivalate 12l (0.94 g, 1.82 mmol)
upon interaction with ZnBr2 (0.02 g, 0.13 mmol) followed by removal
of solvent and column chromatographic purification (silica gel;
hexane−ethyl acetate, 99:1) gave compound 13l as a colorless solid
(0.50 g, 78%): mp 162−164 °C; 1H NMR (300 MHz, CDCl3) δ 8.67
(s, 1H), 8.33−8.30 (m, 1H), 8.12 (d, J = 8.1 Hz, 1H), 7.82−7.75 (m,
2H), 7.66−7.55 (m, 5H), 7.51−7.45(m, 3H); 13C NMR (75 MHz,
CDCl3) δ 140.5, 139.0, 135.6, 134.6, 133.2, 131.5, 131.0, 128.9, 128.6,
128.2, 127.7, 126.0, 125.3, 125.1, 125.0, 124.5, 122.7, 122.0, 119.6;
1
13n as a pale green solid (0.45 g, 70%): mp 187−188 °C; H NMR
(300 MHz, CDCl3) δ 8.64 (s, 1H), 8.32−8.29 (m, 1H), 8.10 (d, J =
7.8 Hz, 1H), 7.85 (d, J = 8.4 Hz, 1H), 7.79−7.76 (m, 1H), 7.55−7.46
(m, 6H), 7.16 (d, J = 8.7 Hz, 2H), 3.97 (s, 3H); 13C NMR (75 MHz,
CDCl3) δ 159.5, 140.5, 138.9, 135.7, 134.5, 132.9, 131.6, 131.2, 131.2,
131.1, 128.7, 127.6, 125.9, 125.1, 125.0, 124.5, 122.7, 122.0, 119.4,
114.3, 55.4; DEPT 135 (75 MHz, CDCl3) δ 131.2, 128.7, 127.6, 125.9,
9066
dx.doi.org/10.1021/jo301410w | J. Org. Chem. 2012, 77, 9053−9071

The Journal of Organic Chemistry
Article
125.0, 124.5, 122.7, 122.0, 119.4, 114.3, 55.4; HRMS (EI) Calcd for
C23H16 OS [M+] 340.0922, found 340.0923.
2H), 7.01−6.98 (m, 1H), 2.34 (s, 3H); 13C NMR (75 MHz, CDCl3) δ
192.3, 188.1, 150.6, 144.2, 141.2, 139.8, 138.7, 137.4, 134.9, 134.7,
132.3, 131.3, 130.8, 129.2, 128.9, 128.0, 124.8, 124.3, 123.4, 121.3,
15.9. Anal. Calcd for C21H14O2S2: C, 69.59; H, 3.89; S, 17.69. Found:
C, 69.38; H, 4.02; S, 17.92.
6-(Thiophen-2-yl)benzo[b]naphtho[2,3-d]thiophene (13o).
Ring-opening of 3-(benzo[b]thiophen-3-yl)isobenzofuran-1(3H)-
one33b with freshly prepared 2-thienylmagnesium bromide followed
by acidic workup gave benzo[c]furan 10o as a fluorescent yellow solid.
Oxidative cleavage of the benzo[c]furan 10o (0.84 g, 2.51 mmol) using
LTA (1.11 g, 2.51 mmol) adopting the procedure similar to that of 4a
furnished diketone 11o as a colorless solid (0.77 g, 88%). Reduction of
the diketone 11o (0.38 g, 1.08 mmol) using sodium borohydride (0.16
g, 4.21 mmol) followed by workup gave diol. Dipivaloylation of the
diol (0.34 g, 0.96 mmol) using pivaloyl chloride (0.57 g, 4.72 mmol)
and triethylamine (1.94 g, 19.17 mmol) in the presence of a catalytic
amount of DMAP (10 mg) in dry DCM (20 mL) led to the isolation
of dipivalate 12o as a thick liquid. Dipivalate 12o (0.51 g, 0.97 mmol)
upon interaction with ZnBr2 (0.02 g, 0.13 mmol) followed by removal
of solvent and column chromatographic purification (silica gel;
hexane−ethyl acetate, 99:1) gave compound 13o as a pale green
solid (0.21 g, 72%): mp 158−160 °C; 1H NMR (300 MHz, CDCl3) δ
8.64 (s, 1H), 8.28−8.04 (m, 3H), 7.80−7.33 (m, 8H); 13C NMR (75
MHz, CDCl3) δ 140.8, 140.3, 138.9, 135.4, 134.5, 132.0, 131.3, 128.7,
127.7, 127.5, 126.9, 126.4, 125.6, 125.1, 124.9, 124.6, 122.6, 122.0,
120.5; DEPT 135 (75 MHz, CDCl3) δ 128.7, 128.6, 127.8, 127.5,
126.9, 126.4, 125.1, 124.9, 124.6, 122.7, 122.0, 120.6. Anal. Calcd for
C20H12S2: C, 75.91; H, 3.82; S, 20.27. Found: C, 75.72; H, 3.96; S,
20.38.
4-(2-Methylbenzo[b]thiophene-3-yl)naptho[2,3-b]thiophene
(13q). Reduction of diketone 11q (0.89 g, 2.45 mmol) using sodium
borohydride (0.47 g, 12.36 mmol) followed by workup afforded diol.
Dipivaloylation of the diol (0.84 g, 2.29 mmol) using pivaloyl chloride
(1.38 g, 11.44 mmol) and triethylamine (4.64 g, 45.85 mmol) in the
presence of a catalytic amount of DMAP (10 mg) in dry DCM (20
mL) led to the isolation of dipivalate 12q as a thick liquid. Dipivalate
12q (1.06 g, 1.98 mmol) upon interaction with ZnBr2 (0.02 g, 0.13
mmol) followed by removal of solvent and column chromatographic
purification (silica gel; hexane−ethyl acetate, 99:1) gave compound
1
13q as a pale yellow solid (0.58 g, 77%): mp 170−172 °C; H NMR
(300 MHz, CDCl3) δ 8.47 (s, 1H), 8.40 (d, J = 8.4 Hz, 1H), 7.87 (d, J
= 8.1 Hz, 1H), 7.58 (d, J = 8.7 Hz, 1H), 7.47 (t, J = 7.4 Hz, 1H),
7.39−7.37 (m, 1H), 7.35−7.26 (m, 2H), 7.13(t, J = 7.4 Hz, 1H),
6.94−6.90 (m, 2H) 2.25(s, 3H); 13C NMR (75 MHz, CDCl3) δ 140.9,
139.1, 138.4, 138.3, 137.9, 131.3, 130.5, 129.9, 128.3, 127.8, 127.0,
126.2, 125.3, 124.2, 123.9, 123.5, 122.9, 122.0, 121.1, 14.7; DEPT 90
(75 MHz, CDCl3) δ 128.3, 127.8, 126.2, 125.3, 124.2, 123.9, 123.5,
122.9, 122.0, 121.1; HRMS (EI) Calcd for C21H14S2 [M+] 330.0537,
found 330.0537.
(2-Benzoylphenyl)(dibenzo[b,d]thiophen-2-y)lmethanone
(15a). Ring-opening of 3-(dibenzo[b,d]thiophen-2-yl)isobenzofuran-
1(3H)-one33c with freshly prepared phenylmagnesium bromide
followed by acidic workup gave benzo[c]furan 14a as a thick yellow
liquid. Oxidation of the benzo[c]furan 14a (2.64 g, 7.02 mmol) using
LTA (3.11 g, 7.02 mmol) adopting the procedure similar to that of 4a
led to the isolation of diketone 15a as a pale yellow solid (1.4 g, 81%):
mp 138−140 °C; 1H NMR (300 MHz, CDCl3) δ 8.12−8.11 (m, 1H),
8.14−8.08 (m, 1H), 7.88−7.80 (m, 3H), 7.75−7.62 (m, 6H), 7.53−
7.46 (m, 3H), 7.40−7.31 (m, 2H); 13C NMR (75 MHz, CDCl3) δ
196.6, 196.3, 144.7, 140.3, 140.0, 139.7, 137.2, 135.5, 135.1, 133.8,
133.0, 130.5, 130.3, 129.9, 129.6, 128.3, 127.8, 127.4, 124.9, 123.3,
122.9, 122.6, 122.0; HRMS (EI) Calcd for C26H16O2S [M+] 392.0871,
found 392.0866.
7-Phenylanthra[2,3-d]benzo[b]thiophene (17a). Reduction of
diketone 15a (1.11 g, 2.83 mmol) using sodium borohydride (0.53 g,
13.94 mmol) followed by workup gave diol. Dipivaloylation of the diol
(1.12 g, 2.82 mmol) using pivaloyl chloride (1.70 g, 14.14 mmol) and
triethylamine (5.72 g, 56.56 mmol) in the presence of a catalytic
amount of DMAP (10 mg) in dry DCM (20 mL) led to the isolation
of dipivalate 16a as a thick liquid. Dipivalate 16a (1.28 g, 2.26 mmol)
upon interaction with ZnBr2 (0.02 g, 0.13 mmol) followed by removal
of solvent and column chromatographic purification (silica gel;
hexane−ethyl acetate, 99:1) gave compound 17a as a yellow solid
(0.83 g, 72%): mp 190−192 °C: 1H NMR (300 MHz, CDCl3) δ 8.70
(s, 1H,), 8.60 (s, 1H), 8.19−8.16 (m, 1H), 8.01−7.96 (m, 2H), 7.67−
7.65 (m, 1H), 7.60−7.52 (m, 5H), 7.40−7.28 (m, 6H); 13C NMR (75
MHz, CDCl3) δ 140.4, 138.8, 137.7, 135.6, 135.1, 134.9, 131.4, 130.9,
129.6, 129.1, 128.6, 128.3, 128.2, 127.6, 127.2, 126.8, 125.5, 124.9,
124.7, 122.8, 122.1, 120.1, 119.2; DEPT 135 (75 MHz, CDCl3) δ
131.4, 128.6, 128.3, 128.2, 127.6, 126.8, 125.5, 124.9, 124.7, 122.8,
122.1, 120.1, 119.2; HRMS (EI) Calcd for C26H16S [M+] 360.0973,
found 360.0974.
2-Methylbenzo[b]thiophen-3-yl)(2-(4-methylbenzoyl)-
phenyl)methanone (11p). Ring-opening of 3-(2-methylbenzo[b]-
thiophen-3-yl)isobenzofuran-1(3H)-one33b with freshly prepared p-
tolylmagnesium bromide followed by acidic workup gave benzo[c]-
furan 10p as a fluorescent orange solid. Oxidation of the benzo[c]furan
10p (1.8 g, 4.94 mmol) using LTA (2.19 g, 3.42 mmol) following the
procedure similar to that of 4a furnished the diketone 11p as a pale
1
yellow solid (1.71 g, 91%): mp 94−96 °C; H NMR (300 MHz,
CDCl3) δ 7.71−7.68 (m, 1H), 7.64−7.59 (m, 2H), 7.57−7.55 (m,
2H), 7.46−7.42 (m, 3H), 7.25−7.19 (m, 1H), 7.17−7.11 (m, 1H),
7.01 (d, J = 8.1 Hz, 2H), 2.30 (s, 3H); 13C NMR (75 MHz, CDCl3) δ
196.1, 192.2, 150.1, 144.0, 141.1, 140.5, 138.7, 137.3, 134.7, 132.4,
131.4, 130.5, 129.4, 129.2, 129.0, 124.6, 124.3, 123.5, 121.2, 21.6, 15.9;
HRMS (EI) Calcd for C24H18O2S [M+] 370.1028, found 370.1021.
2-Methyl-3-(2-methylanthracen-9-yl)benzo[b]thiophene
(13p). Reduction of diketone 11p (1.8 g, 4.73 mmol) using sodium
borohydride (0.9 g, 23.0 mmol) followed by workup gave diol.
Dipivaloylation of the diol (1.57 g, 4.08 mmol) using pivaloyl chloride
(2.46 g, 20.40 mmol) and triethylamine (8.27 g, 81.72 mmol) in the
presence of a catalytic amount of DMAP (10 mg) in dry DCM (20
mL) led to the isolation of dipivalate 12p as a thick liquid. Dipivalate
12p (1.89 g, 3.42 mmol) upon interaction with ZnBr2 (0.02 g, 0.13
mmol) followed by removal of solvent and column chromatographic
purification (silica gel; hexane−ethyl acetate, 99:1) gave compound
1
13p as a pale brown solid (1.14 g, 78%): mp 168−169 °C; H NMR
(300 MHz, CDCl3) δ 8.50 (s, 1H), 8.03 (d, J = 8.7 Hz, 2H), 7.97 (d, J
= 9 Hz, 1H), 7.90 (d, J = 8.1 Hz, 1H), 7.49−7.46 (m, 1H), 7.40 (t, J =
7.2 Hz, 1H), 7.30−7.24 (m, 4H), 7.09 (t, J = 7.5 Hz, 1H), 6.82 (d, J =
7.8 Hz, 1H), 2.34 (s, 3H), 2.18 (s, 3H); 13C NMR (75 MHz, CDCl3)
δ 141.6, 138.5, 138.4, 136.0, 131.4, 131.2, 131.1, 131.0, 130.3, 129.0,
128.6, 127.1, 126.3, 126.0, 125.0, 124.4, 124.3, 124.0, 123.1, 122.1,
22.3, 14.6; DEPT 135 (75 MHz, CDCl3) δ 129.0, 127.0, 128.3, 127.1,
126.3, 126.0, 125.0, 124.9, 124.4, 124.3, 124.0, 123.0, 122.1, 122.3,
22.3, 14.6. Anal. Calcd for C24H18S: C, 85.17; H, 5.36; S, 9.47. Found:
C, 85.34; H, 5.24; S, 9.61.
Dibenzo[b,d]thiophen-2-yl(2-(4-methylbenzoyl)phenyl)-
methanone (15b). Ring-opening of 3-(dibenzo[b,d]thiophen-2-
yl)isobenzofuran-1(3H)-one33 with freshly prepared p-tolylmagnesi-
c
um bromide followed by acidic workup gave benzo[c]furan 14b as a
thick yellow liquid. Oxidative cleavage of the benzo[c]furan 14b (0.65
g, 1.66 mmol) using LTA (0.73 g, 1.64 mmol) following the procedure
similar to that of 4a led to the isolation of diketone 15b as a pale
2-Methylbenzo[b]thiophen-3-yl)(2-(thiophen-2-carbonyl)-
phenyl)methanone (11q). Ring-opening of 3-(2-methylbenzo[b]-
thiophen-3-yl)isobenzofuran-1(3H)-one33b with freshly prepared 2-
thienylmagnesium bromide followed by acidic workup gave benzo[c]-
furan 10q as a fluorescent orange solid. Oxidative cleavage of the
benzo[c]furan 10q (1.1 g, 3.17 mmol) using LTA (1.38 g, 3.11 mmol)
adopting the procedure similar to that of 4a furnished diketone 11q as
1
yellow solid (0.60 g, 90%): mp 144−146 °C; H NMR (300 MHz,
CDCl3) δ 8.42 (s, 1H), 8.05−8.02 (m, 1H), 7.75−7.72 (m, 2H),
7.63−7.52 (m, 7H), 7.42−7.39 (m, 2H), 7.07 (d, J = 8.1 Hz, 2H), 2.27
(s, 3H); 13C NMR (75 MHz, CDCl3) δ 196.4, 196.3, 144.6, 144.0,
140.3, 140.2, 139.6, 135.5, 135.1, 134.7, 133.8, 130.3, 130.0, 129.7,
1
a thick liquid (1.06 g, 92%): H NMR (300 MHz, CDCl3) δ 7.70−
7.60 (m, 5H), 7.54−7.48 (m, 2H), 7.34−7.33 (m, 1H), 7.26−7.15 (m,
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129.6, 129.0, 127.8, 127.4, 124.8, 123.3, 122.9, 122.5, 122.0, 21.7;
HRMS (EI) Calcd for C27H18O2S [M+] 406.1028, found 406.1025.
7-p-Tolylanthra[2,3-d]benzo[b]thiophene (17b). Reduction of
diketone 15b (0.71 g, 1.74 mmol) using sodium borohydride (0.33 g,
8.68 mmol) followed by workup gave diol. Dipivaloylation of the diol
(0.62 g, 1.51 mmol) using pivaloyl chloride (0.91 g, 7.55 mmol) and
triethylamine (3.05 g, 30.14 mmol) in the presence of a catalytic
amount of DMAP (10 mg) in dry DCM (20 mL) led to the isolation
of dipivalate 16b as a thick liquid. Dipivalate 16b (0.89 g, 1.53 mmol)
upon interaction with ZnBr2 (0.02 g, 0.13 mmol) followed by removal
of solvent and column chromatographic purification (silica gel;
hexane−ethyl acetate, 98:2) gave compound 17b as a yellow solid
(0.44 g, 79%): mp 218−220 °C; 1H NMR (300 MHz, CDCl3) δ 8.70
(s, 1H), 8.60 (s, 1H), 8.16 (d, J = 7.8 Hz, 1H), 8.05 (s, 1H), 7.98 (d, J
= 8.4 Hz, 1H), 7.67 (d, J = 8.4 Hz, 2H), 7.40−7.38 (m, 5H), 7.32−
7.30 (m, 3H), 2.52 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 140.4,
137.6, 137.3, 135.0, 134.9, 131.3, 130.9, 130.3, 129.8, 129.3, 129.1,
128.4, 128.1, 127.0, 126.9, 125.4, 124.8, 124.6, 122.8, 122.1, 120.1,
119.2, 21.5; DEPT 135 (75 MHz, CDCl3) δ 131.3, 129.3, 128.4, 127.0,
126.9, 125.4, 124.8, 124.6, 122.8, 122.1, 120.1, 119.2, 21.5; HRMS
(EI) Calcd for C27H18S 374.1129, found 374.1128.
of dipivalate 16d as a thick liquid. Dipivalate 16d (0.97 g, 1.67 mmol)
upon interaction with ZnBr2 (0.02 g, 0.13 mmol) followed by removal
of solvent and column chromatographic purification (silica gel;
hexane−ethyl acetate, 98:2) gave compound 17d as a yellow solid
(0.57 g, 87%): mp 218−220 °C; 1H NMR (300 MHz, CDCl3) δ 8.81
(s, 1H), 8.70 (s, 1H), 8.29−8.26 (m, 1H), 8.10 (d, J = 8.4 Hz, 1H),
7.97 (s, 1H), 7.79 (d, J = 6.3 Hz, 1H), 7.60−7.28 (m, 9H), 3.31 (s,
3H); 13C NMR (75 MHz, CDCl3) δ 140.3, 138.1, 137.9, 137.7, 135.1,
134.9, 134.8, 131.3, 130.9, 130.1, 129.9, 129.2, 129.1, 128.4, 128.0,
127.9, 126.9, 126.4, 125.9, 125.5, 124.8, 124.5, 122.7, 122.0, 120.3,
118.7, 14.7; DEPT 135 (75 MHz, CDCl3) δ 131.4, 130.2, 128.5, 128.0,
127.0, 126.5, 126.0, 125.6, 124.9, 124.6, 122.8, 122.1, 120.3, 118.8,
19.8; HRMS (EI) Calcd for C27H18S [M+] 374.1129, found 374.1124.
(2-(1-Naphthoyl)phenyl)dibenzo[b,d]thiophen-2-yl)-
methanone (15e). Ring-opening of 3-(dibenzo[b,d]thiophen-2-
yl)isobenzofuran-1(3H)-one33c with freshly prepared 1-naphthylmag-
nesium bromide followed by acidic workup gave benzo[c]furan 14e as
a thick yellow liquid. Oxidative cleavage of the benzo[c]furan 14e
(2.13 g, 5.0 mmol) using LTA (2.21 g, 5.0 mmol) adopting the
procedure similar to that of 4a led to the isolation of diketone 15e30 as
1
a colorless solid (1.92 g, 87%): mp 88 °C; H NMR (300 MHz,
CDCl3) δ 8.21 (d, J = 1.2 Hz, 1H), 8.08−8.05 (m, 1H), 8.01−7.98 (m,
1H), 7.89−7.87 (d, J = 8.4 Hz, 1H), 7.85−7.78 (m, 3H), 7.70−7.61
(m, 5H), 7.58−7.53 (m, 2H), 7.47−7.43 (m, 2H), 7.37−7.32 (m, 1H),
7.22−7.17 (m, 1H); 13C NMR (CDCl3, 75 MHz) δ 197.3, 196.6,
144.7, 140.9, 140.5, 139.4, 135.4, 135.1, 134.9, 134.1, 133.3, 132.9,
131.6, 130.8, 130.6, 130.4, 129.1, 127.9, 127.3, 127.2, 127.1, 126.0,
125.1, 124.7, 123.9, 122.7, 122.5, 122.4, 121.8; DEPT 135 (75 MHz,
CDCl3) δ 133.0, 131.7, 130.9, 130.7, 130.5, 129.2, 128.0, 127.4, 127.3,
127.2, 126.3, 125.2, 124.8, 123.9, 122.8, 122.6, 122.5, 121.9.
7-(4-Methoxyphenyl)anthra[2,3-d]benzo[b]thiophene (17c).
Ring-opening of 3-(dibenzo[b,d]thiophen-2-yl)isobenzofuran-1(3H)-
one33c with freshly prepared p-anisylmagnesium bromide followed by
acidic workup gave benzo[c]furan 14c as a fluorescent yellow solid.
Oxidation of the benzo[c]furan 14c (1.50 g, 3.69 mmol) using LTA
(1.63 g, 3.69 mmol) adopting the procedure similar to that of 4a led to
the isolation of diketone 15c as a colorless solid (1.38 g, 89%).
Reduction of the diketone 15c (1.20 g, 2.84 mmol) using sodium
borohydride (0.54 g, 14.21 mmol) followed by workup gave diol.
Dipivaloylation of the diol (1.10 g, 2.58 mmol) using pivaloyl chloride
(1.55 g, 12.85 mmol) and triethylamine (5.20 g, 51.38 mmol) in the
presence of a catalytic amount of DMAP (10 mg) in dry DCM (20
mL) led to the isolation of dipivalate 16c as a thick liquid. Dipivalate
16c (1.28 g, 2.15 mmol) upon interaction with ZnBr2 (0.02 g, 0.13
mmol) followed by removal of solvent and column chromatographic
purification (silica gel; hexane−ethyl acetate, 97:3) gave compound
7-(Napthalen-1-yl)anthra[2,3-d]benzo[b]thiophene (17e).
Reduction of diketone 15e (1.11 g, 2.51 mmol) using sodium
borohydride (0.53 g, 12.63 mmol) followed by workup gave diol.
Dipivaloylation of the diol (1.15 g, 2.57 mmol) using pivaloyl chloride
(1.55 g, 12.85 mmol) and triethylamine (5.21 g, 51.57 mmol) in the
presence of a catalytic amount of DMAP (10 mg) in dry DCM (20
mL) led to the isolation of dipivalate 16e as a thick liquid. Dipivalate
16e (1.30 g, 2.11 mmol) upon interaction with ZnBr2 (0.02 g, 0.13
mmol) followed by removal of solvent and column chromatographic
purification (silica gel; hexane−ethyl acetate, 98:2) gave compound
1
17c as a yellow solid (0.7 g, 70%): mp 172−174 °C; H NMR (300
MHz, CDCl3) δ 8.80 (s, 1H), 8.70 (s, 1H), 8.31−8.28 (m, 1H), 8.12−
8.07 (m, 2H), 7.79−7.73 (m, 2H), 7.51−7.38 (m, 6H), 7.20−7.17 (m,
2H), 4.01 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 159.1, 140.4, 137.6,
135.4, 135.1, 134.9, 132.5, 131.0, 130.8, 130.6, 13.0, 129.2, 128.3,
128.1, 127.0, 126.9, 125.4, 124.8, 124.6, 122.8, 122.1, 120.1, 119.2,
114.0, 55.4; DEPT 135 (75 MHz, CDCl3) δ 132.5, 128.3, 128.1, 127.0,
126.9, 125.4, 124.8, 124.6, 122.8, 122.1, 120.1, 119.2, 114.0, 55.4;
HRMS (EI) Calcd for C27H18OS [M+] 390.1078, found 390.1081.
Dibenzo[b,d]thiophen-2-yl(2-(2-methylbenzoyl)phenyl)-
methanone (15d). Ring-opening of 3-(dibenzo[b,d]thiophen-2-
yl)isobenzofuran-1(3H)-one33c with freshly prepared o-tolylmagnesi-
um bromide followed by acidic workup gave benzo[c]furan 14d as a
thick yellow liquid. Oxidative cleavage of the benzo[c]furan 14d (1.13
g, 2.89 mmol) using LTA (1.28 g, 2.89 mmol) following the procedure
similar to that of 4a led to the isolation of diketone 15d as a pale
1
17e as a yellow solid (0.53 g, 51%): mp 184−186 °C; H NMR (300
MHz, CDCl3) δ 8.79 (s, 1H), 8.74 (s, 1H), 8.22 (s, 1H), 8.08−8.02
(m, 2H), 7.97 (d, J = 8.4 Hz, 1H), 7.73 (s, 1H), 7.65 (d, J = 6.9 Hz,
2H), 7.50 (d, J = 6.9 Hz, 1H), 7.44−7.35 (m, 4H), 7.18−7.09 (m,
3H), 7.02−6.99 (m, 1H); 13C NMR (75 MHz, CDCl3) δ 140.4, 137.9,
134.8, 133.8, 133.5, 131.0, 130.4, 129.3, 129.2, 128.4, 128.3, 128.2,
127.5, 127.0, 126.9, 126.7, 126.5, 126.4, 126.1, 125.7, 125.6, 125.0,
124.6, 124.5, 122.8, 122.1, 121.8, 120.2, 119.3; DEPT 135 (75 MHz,
CDCl3) δ 129.3, 128.4, 128.3, 128.2, 127.5, 127.0, 126.9, 126.5, 126.4,
126.1, 125.7, 125.0, 124.6, 122.8, 122.1, 121.8, 120.2, 119.3; HRMS
(EI) Calcd for C30H18S [M+] 410.1129, found 410.1123.
Dibenzo[b,d]thiophen-2-yl(2-(thiophen-2-carbonyl)phenyl)-
methanone (15f). Ring-opening of 3-(dibenzo[b,d]thiophen-2-yl)-
isobenzofuran-1(3H)-one33c with freshly prepared 2-thienylmagnesi-
um bromide followed by acidic workup gave benzo[c]furan 14f as a
thick yellow liquid. Oxidative cleavage of the benzo[c]furan 14f (2.10
g, 5.49 mmol) using LTA (2.43 g, 5.49 mmol) following the procedure
similar to that of 4a afforded diketone 15f30 as a pale yellow solid
(1.75 g, 92%): mp 110−112 °C; 1H NMR (300 MHz, CDCl3) δ 8.21
(s, 1H), 7.91−7.90 (m, 2H), 7.85−7.82 (m, 3H), 7.70−7.65 (m, 3H),
7.58−7.47(m, 3H), 7.39−7.34 (m, 1H), 7.23−7.18 (m, 1H); 13C
NMR (75 MHz, CDCl3) δ 196.2, 188.2, 144.7, 144.0, 139.9, 139.8,
139.6, 135.4, 135.1, 135.0, 134.8, 133.7, 130.6, 130.4, 129.7, 129.2,
128.0, 127.8, 127.7, 127.4, 125.8, 124.8, 122.6, 122.0; DEPT 135 (75
MHz, CDCl3) δ 135.0, 134.9, 130.6, 130.4, 129.7, 129.2, 128.0, 127.7,
127.4, 124.8, 123.3, 122.8, 122.6, 122.0.
1
yellow solid (0.96 g, 82%): mp 164−166 °C; H NMR (300 MHz,
CDCl3) δ 8.38 (s, 1H), 8.02−7.91 (m, 1H), 7.73−7.64 (m, 3H),
7.51−7.47 (m, 4H), 7.35−7.30 (m, 2H), 7.22−7.11 (m, 2H), 7.02−
6.98 (m, 2H), 2.14 (s, 3H); 13C NMR (75 MHz, CDCl3) δ 198.0,
196.8, 144.7, 141.0, 140.1, 139.7, 138.9, 137.3, 135.5, 135.1, 133.9,
131.5, 131.4, 131.3, 130.7, 130.5, 130.1, 129.0, 127.6, 127.4, 125.2,
124.9, 123.0, 122.9, 122.6, 121.9, 20.4; DEPT 135 (75 MHz, CDCl3) δ
131.4, 131.4, 131.3, 130.7, 130.5, 130.1, 129.0, 127.6, 127.4, 125.2,
124.9, 124.7, 123.0, 122.9, 122.6, 121.9, 20.4. Anal. Calcd for
C27H18O2S: C, 79.78; H, 4.46; S, 7.89. Found: C, 79.53; H, 4.61; S
7.84.
7-o-Tolylanthra[2,3-d]benzo[b]thiophene (17d). Reduction of
diketone 15d (0.74 g, 1.82 mmol) using sodium borohydride (0.28 g,
7.36 mmol) followed by workup afforded diol. Dipivaloylation of the
diol (0.72 g, 1.75 mmol) using pivaloyl chloride (1.05 g, 8.77 mmol)
and triethylamine (3.55 g, 35.09 mmol) in the presence of a catalytic
amount of DMAP (10 mg) in dry DCM (20 mL) led to the isolation
7-(Thiophen-2-yl)anthra[2,3-d]benzo[b]thiophene (17f). Re-
duction of diketone 15f (1.12 g, 2.81 mmol) using sodium
borohydride (0.53 g, 13.94 mmol) followed by workup afforded
diol. Dipivaloylation of the diol (1.12 g, 2.82 mmol) using pivaloyl
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chloride (1.67 g, 13.84 mmol) and triethylamine (5.63 g, 55.68 mmol)
in the presence of a catalytic amount of DMAP (10 mg) in dry DCM
(20 mL) led to the isolation of dipivalate 16f as a thick liquid.
Dipivalate 16f (1.32 g, 2.34 mmol) upon interaction with ZnBr2 (0.02
g, 0.13 mmol) followed by removal of solvent and column
chromatographic purification (silica gel; hexane−ethyl acetate, 98:2)
gave compound 17f as a yellow solid (0.83 g, 82%): mp 219−220 °C;
1H NMR (300 MHz, CDCl3) δ 8.79 (s, 1H), 8.74 (s, 1H), 8.29−8.26
(m, 1H), 8.24 (s, 1H), 8.06 (d, J = 7.8 Hz, 1H), 7.85 (d, J = 8.4 Hz,
1H), 7.78−7.75 (m, 1H), 7.66−7.65 (m, 1H), 7.49−7.41 (m, 4H),
7.37−7.34 (m, 1H); 13C NMR (75 MHz, CDCl3) δ 140.4, 139.0,
135.3, 134.8, 131.9, 131.1, 130.7, 129.6, 129.0, 128.6, 128.3, 127.3,
126.9, 126.5, 125.7, 125.0, 124.7, 122.8, 122.1, 120.0, 118.9; DEPT
135 (75 MHz, CDCl3) δ 129.6, 128.6, 128.2, 127.3, 126.6, 126.0,
125.0, 124.7, 122.9, 122.1, 120.0, 119; HRMS (EI) Calcd for C24H14S2
[M+] 366.0537, found 366.0533.
(9-Hexyl-9H-carbazol-3-yl)(2-(4-methylbenzyl)phenyl)-
methanone (15h). Interaction of 3-(N-hexylcarbazol-3-yl)-
isobenzofuran-1(3H)-one33c (1 g, 2.61 mmol) with p-tolylmagnesium
bromide [prepared from 4-bromotoluene (0.67 g, 4.11 mmol) and Mg
(0.15 g, 6.16 mmol)] followed by acidic workup gave benzo[c]furan
14h as a thick orange liquid (0.69 g, 58%). To a solution of crude
benzo[c]furan 14h (0.50 g, 1.09 mmol) in DCM (15 mL), m-CPBA
(0.37 g, 1.64 mmol) was added, and the reaction mixture was stirred at
room temperature for 5 min. It was then poured into saturated sodium
bicarbonate solution, extracted with DCM (3 × 30 mL). The
combined organic extract was washed with water (2 × 30 mL) and
dried (Na2SO4). Removal of solvent followed by column chromato-
graphic purification (silica gel, hexane−ethyl acetate, 95:5) afforded
diketone 15h30 as a thick yellow liquid (0.42 g, 80%): H NMR (300
1
MHz, CDCl3) δ 8.38 (s, 1H), 7.94 (d, J = 7.8 Hz, 1H), 7.79 (d, J = 8.7
Hz, 1H), 7.63−7.52 (m, 6H), 7.37 (d, J = 7.5 Hz, 1H), 7.31 (d, J = 8.1
Hz, 1H), 7.23 (d, J = 8.7 Hz, 1H), 7.15 (t, J = 7.4 Hz, 1H), 7.03 (d, J =
8.1 Hz, 2H), 4.18 (t, J = 7.2 Hz, 2H), 2.24 (s, 3H), 1.78−1.71 (m,
2H), 1.22−1.20 (m, 6H), 0.77 (t, J = 6.8 Hz, 3H); 13C NMR (75
MHz, CDCl3) δ 195.5, 195.2, 142.7, 142.2, 140.1, 139.9, 139.2, 133.8,
129.1, 128.9, 128.8, 128.6, 128.4, 127.9, 127.6, 127.1, 125.3, 122.7,
122.1, 121.5, 119.7, 118.9, 108.2, 107.2, 42.3, 30.5, 27.8, 25.9, 21.5,
20.6, 12.9; DEPT 135 (75 MHz, CDCl3) δ 130.1, 130.0, 129.9, 129.6,
129.5, 128.9, 128.1, 126.4, 123.7, 120.7, 119.9, 109.2, 108.3, 43.3, 31.5,
28.8, 26.9, 22.5, 21.7, 14.0.
Attempted Preparation of 5-Hexyl-7-p-tolyl-5H-naphtho-
[2,3-b]carbazole (17h). Reduction of diketone 15h (0.42 g, 0.94
mmol) using sodium borohydride (0.18 g, 4.74 mmol) followed by
workup gave diol. Dipivaloylation of the diol (0.40 g, 0.83 mmol)
using pivaloyl chloride (0.56, 13.27 mmol) and triethylamine (1.90 g,
18.82 mmol) in the presence of a catalytic amount of DMAP (10 mg)
in dry DCM (20 mL) led to the isolation of dipivalate 16h as a thick
liquid. Dipivalate 16h (0.61 g, 0.94 mmol) upon interaction with
ZnBr2 (0.02 g, 0.13 mmol) followed by removal of solvent and column
chromatographic purification did not afford any characterizable
product.
(2-(Dibenzo[b,d]furan-2-carbonyl)phenyl)(5-hexylthiophen-
2-yl)methanone (15g). Ring-opening of 3-(dibenzo[b,d]furan-2-
yl)isobenzofuran-1(3H)-one33c (1.8 g, 6.00 mmol) with freshly
prepared 5-hexyl-2-thienylmagnesium bromide [prepared from 5-
hexyl-2-bromo thiophene (2.22 g, 9 mmol) and Mg (0.328 g, 13. 48
mmol)] followed by acidic workup gave benzo[c]furan 14g as a thick
orange solid (1.52 g, 56%). The crude benzo[c]furan 14g (1.0 g, 2.14
mmol) upon reaction with LTA (0.95 g, 2.14 mmol) in DCM
adopting the procedure similar to that of 4a led to the isolation of
diketone 15g30 as a thick red liquid (0.92 g, 89%): H NMR (300
1
MHz, CDCl3) δ 8.33 (s, 1H) 7.91−7.89 (m, 1H), 7.87−7.84 (m, 1H),
7.79−7.76 (m, 1H), 7.68−7.63 (m, 3H), 7.59−7.56 (m, 1H), 7.53−
7.51 (m, 1H), 7.50−7.46 (m, 1H), 7.37−7.32 (m, 2H), 6.75−6.74 (m,
1H), 2.74 (t, J = 7.5 Hz, 2H), 1.63−1.55 (m, 2H), 1.27−1.25 (m, 6H),
0.86 (t, J = 6.4 Hz, 3H); 13C NMR (75 MHz, CDCl3) δ 196.1, 187.9,
158.9, 157.5, 156.8, 141.5, 140.0, 139.8, 135.7, 132.6, 130.5, 130.3,
129.5, 129.1, 127.9, 125.6, 124.4, 123.7, 123.3, 123.2, 121.1, 111.9,
111.5, 31.4, 31.2, 30.7, 28.7, 22.5, 14.1.
Annulation of Dipivaloyl Ester (16g). Reduction of diketone
15g (1.08 g, 2.22 mmol) using sodium borohydride (0.42 g, 11.11
mmol) followed by workup gave diol. Dipivaloylation of the diol (1.10
g, 2.26 mmol) using pivaloyl chloride (1.36 g, 11.31 mmol) and
triethylamine (4.58 g, 45.26 mmol) in the presence of a catalytic
amount of DMAP (10 mg) in dry DCM (20 mL) led to the isolation
of dipivalate 16g as a thick liquid. Dipivalate 16g (1.32 g, 2.01 mmol)
upon interaction with ZnBr2 (0.02 g, 0.13 mmol) followed by removal
of solvent and column chromatographic purification (silica gel;
hexane−ethyl acetate, 98:2) gave compounds 17g and 17g′.
7-(5-Hexylthiophen-2-yl)anthra[2,3-d]benzo[b]furan (17g).
Dark brown solid; 0.48 g (48%): mp 90−92 °C; 1H NMR (300
MHz, CDCl3) δ 8.67 (s, 1H), 8.53 (s, 1H), 8.09−7.97 (m, 4H), 7.53−
7.44 (m, 5H), 7.05−7.02 (m, 2H), 3.03−2.98 (m, 2H), 1.89−1.84 (m,
2H), 1.60−1.42 (m, 6H), 1.01−0.90 (m, 3H); 13C NMR (75 MHz,
CDCl3) δ 158.2, 155.1, 147.4, 136.3, 131.9, 131.7, 129.0, 128.9, 128.7,
128.2, 126.7, 126.4, 126.2, 125.8, 124.6, 124.0, 123.6, 122.8, 121.6,
119.1, 111.4, 104.8, 31.7, 31.6, 30.3, 29.0, 22.6; DEPT 135 (75 MHz,
CDCl3) δ 130.4, 129.0, 128.9, 128.2, 126.4, 125.8, 125.0, 124.6, 124.0,
122.8, 121.6, 119.1, 1, 111.4, 104.8, 31.8, 31.7, 30.4, 29.0, 22.7, 14.1.
Anal. Calcd for C30H26OS: C, 82.91; H, 6.03; S, 7.38. Found: C, 82.68;
H, 6.17; S, 7.45.
(2-(4-(Diphenylamino)benzoyl)phenyl)(4-methoxyphenyl)-
methanone (15i). Ring-opening of 3-(4-(diphenylamino)phenyl)-
isobenzofuran-1(3H)-one33c with freshly prepared p-anisylmagnesium
bromide followed by acidic workup gave benzo[c]furan 14i as an
orange solid. The benzo[c]furan 14i (0.50 g, 1.07 mmol) upon
oxidative ring-opening reaction with m-CPBA (0.36 g, 1.61 mmol)
using the above-mentioned procedure led to the isolation of diketone
15i30 as a pale yellow solid (0.43 g, 93%): mp 144−145 °C; 1H NMR
(300 MHz, CDCl3) δ 7.64 (d, J = 8.7 Hz, 2H), 7.53−7.44 (m, 6H),
7.25−7.18 (m, 4H), 7.05−7.03 (m, 6H), 6.82−6.78 (m, 4H), 3.77 (s,
3H); 13C NMR (75 MHz, CDCl3) δ 195.5, 195.0, 163.5, 152.1, 146.4,
140.4, 140.2, 132.3, 131.6, 130.3, 129.9, 129.8, 129.7, 129.6, 129.3,
129.2, 129.0, 124.7, 119.4, 113.6, 55.5.
Attempted Preparation of 10-(4-Methoxyphenyl)-N,N-di-
phenylanthracen-2-amine (17i). Reduction of diketone 15i (0.43
g, 0.89 mmol) using sodium borohydride (0.16 g, 4.45 mmol)
followed by workup gave diol. Dipivaloylation of the diol (0.41 g, 0.84
mmol) using pivaloyl chloride (0.51 g, 13.4 mmol) and triethylamine
(1.70 g, 35.09 mmol) in the presence of a catalytic amount of DMAP
(10 mg) in dry DCM (20 mL) led to the isolation of dipivalate 16i as a
thick liquid. Dipivalate 16i (0.62 g, 0.94 mmol) upon interaction with
ZnBr2 (0.02 g, 0.13 mmol) followed by removal of solvent and column
chromatographic purification did not afford any characterizable
product.
3-(2-Hexylnaptho[2,3-b]thiophen-4-yl)dibenzo[b,d]benzo-
1
[b]furan (17g′). Thick pale green liquid; 0.23 g (23%): H NMR
(300 MHz, CDCl3) δ 8.18 (s, 1H), 7.93 (s, 1H), 7.80 (d, J = 8.1 Hz,
2H), 7.64 (t, J = 8.7 Hz, 2H), 7.53 (d, J = 8.1 Hz, 1H), 7.45−7.19 (m,
5H), 6.65 (s, 1H), 2.73−2.68 (m, 2H), 1.63−1.56 (m, 2H), 1.26−1.16
(m, 6H), 0.76−0.72 (m, 3H); 13C NMR (75 MHz, CDCl3) δ 156.7,
155.6, 148.5, 139.2, 138.0, 133.8, 132.7, 130.7, 129.8, 127.5, 127.4,
126.2, 124.9, 124.7, 124.5, 124.2, 122.9, 122.8, 120.8, 120.1, 119.7,
111.8, 111.6, 31.5, 31.4, 31.0, 30.7, 28.9, 22.5, 14.0; DEPT 135 (75
MHz, CDCl3) δ 129.8, 127.5, 127.4, 126.2, 124.9, 124.7, 122.9, 122.7,
120.8, 120.1, 119.7, 111.8, 111.6, 31.5, 31.4, 30.7, 28.9, 22.5, 14.0. Anal.
Calcd for C30H26OS: C, 82.91; H, 6.03; S, 7.38. Found: C, 82.74; H,
6.18; S, 7.49.
ASSOCIATED CONTENT
■
S
* Supporting Information
1
Copies of H, 13C NMR, DEPT 135, HRMS spectra (most of
the cases) and X-ray data (6m, 13o and 17a) of annulated
1
heterocycles. Copies of H, 13C NMR and HRMS (4d, 11d,
11i, 11m, 11p, 15a and 15b) spectra of 1,2-diaroylbenzenes.
This material is available free of charge via the Internet at
http://pubs.acs.org.
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Article
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Ed. 2002, 41, 817−819.
AUTHOR INFORMATION
■
Corresponding Author
*Fax: 91-44-22300488. E-mail: mohanakrishnan@unom.ac.in.
Notes
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The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank the Department of Science and Technology (DST)
and University Grants Commission (UGC), New Delhi, for
financial support. R.S. thanks the UGC, New Delhi, for
fellowship. M.N. thanks DST, New Delhi, for fellowship. The
authors thank the Department of Science and Technology
Funds for the Improvement of Science and Technology (DST-
FIST) for NMR facility. We thank reviewers for critical
suggestions on the mechanism of annulation reaction.
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