Regioselective annulation of unsymmetrical 1,2-phenylenebis(diaryl/diheteroarylmethanol): A facile synthesis of anthracene, tetracene, and naphtho[b]thiophene analogues

FULL PAPER

DOI: 10.1002/ejoc.201501087

Regioselective Annulation of Unsymmetrical 1,2-Phenylenebis(diaryl/

diheteroarylmethanol): A Facile Synthesis of Anthracene, Tetracene, and

Naphtho[b]thiophene Analogues

Ramakrishnan Sivasakthikumaran,^[a]Settu Muhammad Rafiq,^[a]Elumalai Sankar,^[a]

J. Arul Clement,^[a]and Arasambattu K. Mohanakrishnan*^[a]

Keywords: Synthetic methods / Polycycles / Annulation / Aromaticity

A systematic study on the regioselective cyclization of benz-

ene- and naphthalene-based unsymmetrical diols with HBr

(33%) in acetic acid at room temperature led to the formation

of annulation products. By using this method, synthesis of a

wide variety of anthracene, tetracene and naphtho[b]thio-

phene analogues was achieved in good to excellent yields.

By employing HBr (33%) in acetic acid as a catalyst for re-

gioselective cyclization of unsymmetrical diols was very fac-

ile and devoid of commonly encountered dihydroisobenzo-

furan formation.

intramolecular cyclization reaction. Yu and Lu reported^[18]

the synthesis of anthracenes and tosylamino fluorene deriv-

atives that involved BF₃·OEt₂-catalyzed intramolecular aza-

Friedel–Crafts reaction of respective benzylic and biphen-

ylcarbaldehydes. An easy route to anthracenes was achieved

by In(OTf)₃-catalyzed cyclodehydration reaction of 2-

benzbenzaldehydes.^[19]The Brønsted acid catalyzed synthe-

sis of substituted anthracenes was realized by Bodzioch et

al.^[20]In 2007, Liu and co-workers reported the synthesis

of 9-arylanthracenes and heteroacenes through triflic acid

mediated annulation reaction of symmetrical diacetates.^[21]

We recently reported^[22]the regiospecific synthesis of annu-

lated arenes and heteroarenes by ZnBr₂-mediated domino

reaction of unsymmetrical dipivalates. It has been observed

that 1,2-phenylenebis(diphenylmethanol) upon reaction

with Brønsted acids leads to the formation of 9-phenyl-

anthracene as well as 1,3-diphenyldihydroisobenzofuran.^[21]

This observation, coupled with our recent failure of ZnBr₂-

mediated annulation reaction of carbazole and tri-

Introduction

π-Conjugated organic compounds with fused ring sys-

tems have received significant interest over recent decades

as versatile and high-performance active components in a

variety of optical devices.^[1]Organic π-conjugated molecules

show promising applications in the area of optoelectronic

devices that include organic light-emitting diodes (OLEDs),

photovoltaic cells, and organic field-effect transistors

(OFETs).^[2]In particular, anthracene analogues are utilized

as functional materials in optoelectronic devices.^[3]Anthra-

cene and its derivatives have wide applications in OLEDs,^[4]

dye-sensitized solar cells,^[5]OFETs,^[6]sensors,^[7]biology,^[8]

and so on. In this regard, scope for the synthesis of anthra-

cene analogues is enormous. Anthracene analogues have

been prepared by Friedel–Crafts reaction,^[9]Elbs reac-

tion,^[10]aromatic cyclodehydration,^[11]flash vacuum pyroly-

sis,^[12]Lewis acid induced cyclization of diarylmethanes,^[13]

and transition metal mediated homologation.^[14]

In recent years, the Lewis acid/Brønsted acid mediated

domino reaction has been successfully applied for the syn-

thesis of a wide variety of π-conjugated heterocycles.^[15]Shu

et al. reported^[16]the synthesis of substituted anthracenes

by gold-catalyzed intramolecular cyclization of orthoalk-

ynyl-diarylmethanes. Matsuo and co-workers achieved^[17]

the synthesis of anthracenes from diarylmethanes through

a Bradsher-type reaction that involved formylation of the

aryl unit followed by Lewis acid catalyzed Friedel–Crafts

[a] Department of Organic Chemistry, University of Madras,

Guindy Campus, Chennai 600025, Tamil Nadu, India

E-mail: mohan_67@hotmail.com

mohanakrishnan@unom.ac.in

www.unom.ac.in

Supporting information for this article is available on the

WWW under http://dx.doi.org/10.1002/ejoc.201501087.

Scheme 1. Synthesis of annulated arenes and heteroarenes.

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Anthracene, Tetracene, and Naphtho[b]thiophene Analogues

phenylamine tethered dipivalate systems,^[22]prompted us to

Having prepared the required diols, the subsequent intra-

undertake a systematic study on the cyclization of 1,2-phen- molecular cyclization reaction was planned with a suitable

ylenebis(diarylmethanols). In continuation of our studies Brønsted/Lewis acid, which will overcome the commonly

on the synthesis of π-conjugated heterocycles,^[23]we de- encountered phthalan formation.^[25]Moreover, successful

scribe herein our results on the synthesis of anthracene and annulation reaction of unsymmetrical and symmetrical di-

naptho[b]thiophene derivatives 2 that involve Lewis acid/ arylmethanols will eliminate the unnecessary acetoylation/

Brønsted acid mediated regioselective cyclization reactions pivaloylation step.^[21,22]As expected, unsymmetrical 1,2-

of unsymmetrical 1,2-phenylenebis(diaryl/diheteroaryl- phenylenebis(diarylmethanols) 7a–7c upon reaction with

methanols) 1 (Scheme 1).

BF₃·OEt₂(20 mol-%)/HBr (33%, 5 equiv.) in acetic acid at

room temperature led to the formation of naphtho[b]thio-

phenes 13a–13c as the exclusive products (Scheme 3).

Results and Discussion

The preparation of required diarylmethine diols 7a–7c

were initiated from 2-thiophenylisobenzofuranone (3).^[24]

Reaction of 2-thiophenyl-substituted lactone 3 with aryl

Grignard reagents followed by an aqueous NH₄Cl workup

furnished keto alcohols 4a–4c. Surprisingly, our attempt to

reduce keto alcohols 4a–4c by using NaBH₄in tetra-

hydrofuran (THF)/EtOH at reflux temperatures led to the

formation of benzo[c]furans 5a–5c^[24]through a facile

borohydride-induced cyclodehydration reaction. However, a

slightly longer route that involved oxidation of keto

alcohols 4a–4c with pyridinium chlorochromate (PCC) fol-

lowed by NaBH₄reduction afforded required benzylic diols

7a–7e as thick liquids (Scheme 2). By using a similar proto-

col, 2,2Ј-bithiophenyl lactone 8 upon reaction with aryl

Grignard reagents followed by PCC oxidation furnished re-

quired diketones 9a–9e. As expected, diketones 9a–9e upon

NaBH₄reduction led to respective benzylic diols 10a–10e.

By systematic study of annulation reactions of diols, repre-

sentative symmetrical diols 12a–12c were prepared through

heteroaryl/aryl Grignard addition of phthaldehyde 11

(Scheme 2).

Scheme 3. Annulation reaction of unsymmetrical 1,2-phenylene-

bis(diarylmethanols) 7a–7c and 10a–10e.

Under identical conditions, unsymmetrical diols 10a–10c

furnished respective naphtho[b]thiophenes 14a–14c in 78–

87% yields. Surprisingly, cyclization of diol 10d with either

HBr (33%) in acetic acid or BF₃·OEt₂in CH₂Cl₂furnished

benzoanthracene 14d as the exclusive product. HBr (33%)

in acetic acid/BF₃·OEt₂-mediated cyclization reaction of di-

heteroaryl diol 10e led to the isolation of isomeric naphtho-

[b]thiophenes 14e and 14eЈ. The yields of the annulation

products obtained with BF₃·OEt₂and HBr (33%) in acetic

acid were comparable with only a slightly favoring of the

latter. Having achieved the facile annulation of diols 7a–7c

and 10a–10e, a similar type of cyclization reaction was

planned with symmetrical diols 12a–12c. Heteroaryl sym-

metrical diol 12a upon reaction with BF₃·OEt₂/ZnBr₂/HBr

(33%) in acetic acid furnished the naphtho[b]thiophene 15a

as the sole product in 75–83% yields (Scheme 4). The sim-

ilar reaction of diphenyl symmetric diol 12b with BF₃·OEt₂/

ZnBr₂in CH₂Cl₂at room temperature led to the formation

of 1,3-diphenyl-1,3-dihydroisobenzofuran 16b.^[21]Dihydro-

isobenzofuran 16b upon further reaction with triflic acid

Scheme 2. Preparation of unsymmetrical and symmetrical 1,2-

phenylenebis(diarylmethanols) 7a–7c, 10a–10e, and 12a–12c.

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(1 equiv.) in CH₂Cl₂at room temperature led to the forma-

The regioselective formation of naphtho[b]thiophenes

tion of 9-phenylanthracene 15b. To our surprise, diol 12b 13a–13c and 14a–14c can be visualized through the inter-

upon reaction with HBr (33%) in acetic acid furnished 9- mediacy of diarylmethyl carbocations followed by intra-

bromo-10-phenylanthracene 17 as the exclusive product in molecular cyclization at the thiophene 3-position and sub-

84% yield. However, under identical conditions, symmetri- sequent aromatization through dehydration. In the case of

cal diol 12c led to anthracene 15c. Reaction of symmetrical 10d, exclusive intramolecular cyclization at the naphthalene

diol 12a/12b with triflic acid (30 mol-%) afforded mixture 2-position led to anthracene 14d. The formation of isomeric

of 1,3-disubstituted-1,3-dihydroisobenzofuran 16a/16b and naphtho[b]thiophenes 14e and 14eЈ clearly confirms the

1

annulation product 15a/15b (confirmed by H NMR spec- competing intermolecular cyclization of the resulting carbo-

troscopy). Further reaction of the mixture of dihydroiso- cations at the 3-positions of thiophene as well as 2,2Ј-bi-

benzofuran 16a/16b and annulation product 15a/15b with thiophene. As mentioned above, the formation of annu-

an additional equivalent of triflic acid ensured the smooth lation product 15a can be proposed from respective diol

1

transformation (confirmed by H NMR spectroscopy) of 12a through a cyclization-dehydration protocol. Obviously,

dihydroisobenzofuran 16a/16b into respective annulation when diol 12b was treated with BF₃·OEt₂/ZnBr₂, the re-

product 15a/15b (Scheme 4).

sulting diarylmethine carbocation reacted with the OH

group instead of the less-nucleophilic phenyl unit to pro-

duce dihydroisobenzofuran 16b. However, formation of 9-

bromo-10-phenylanthracene 17 can be conceived only

through the formation of benzylic bromide 18^[26]followed

by intramolecular cyclization and subsequent oxidative aro-

matization of dihydroanthracene 19 (Scheme 5).

Scheme 5. Mechanistic rational for 9-bromoanthracene 17.

After achieving the facile annulation of benzylic diols

7a–7c, 10a–10d, and 12a–12c in the presence of HBr (33%)

in acetic acid, the preparation of various types of unsym-

metrical bis(diaryl/diheteroarylmethanols) was envisaged to

Scheme 4. Annulation of symmetrical 1,2-phenylenebis(diaryl-

methanols) 12a/12b.

Even though Liu and co-workers observed that reaction

of diol 12b with triflic acid (10 mol-%) in CH₂Cl₂at room

temperature for 1 min led to dihydroisobenzofuran 16b as

the exclusive product,^[21]it has now been confirmed that

either an increase in the equivalent of triflic acid or reaction

time drastically enhanced the yield of 9-phenylanthracene

15b at the expense of dihydroisobenzofuran 16b.

Scheme 6. Preparation of 1,2-phenylenebis(diaryl/heteroaryl)meth-

anols 22a–22j, 26a–26e, and 30a–30m.

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Anthracene, Tetracene, and Naphtho[b]thiophene Analogues

study their efficacy towards the synthesis of annulated ar- 30m as shown in Scheme 6. Crude diols 22a–22j, 26a–26e,

enes. Accordingly, known 1,3-diarylbenzo[c]furans 20a–20j, and 30a–30m used in the annulation reaction without fur-

24a–24e, and 28a–28m^[24]could be oxidatively cleaved with ther characterization.

[27]

active MnO₂to furnish diketones 21a–21j, 25a–25e, and

As expected, unsymmetrical aryl/heteroarylmethine diols

29a–29m, respectively. These diketones upon NaBH₄re- 22a–22j, 26a–26e, and 30a–30m upon interaction with HBr

duction afforded required diols 22a–22j, 26a–26e, and 30a– (33%, 5 equiv.) in acetic acid at room temperature for

Table 1. Synthesis of anthracenes and naphtho[b]thiophenes.

[a] Unsymmetrical diol (1 equiv.) and HBr (33%) in AcOH (5 equiv.) at room temperature for 10 min. [b] Yield after column chromatog-

1

raphy. [c] Yield based on H NMR spectroscopy.

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10 min followed by workup and purification by column earlier attempts to prepare heterocycles of type 31i–31m,

chromatography furnished various anthracene and which involves Lewis/Brønsted acid mediated cyclization re-

naphtho[b]thiophene analogues. The structures of annu- action of N-hexylcarbazole/triphenylamine-tethered di-

lated arenes and heteroarenes obtained along with their pivalate, was found to be unsuccessful.^[22]Thus, the regio-

yields are shown in Table 1.

selective formation of annulated products 23a–23j, 27a–27e,

The reaction of diol 22a with HBr (33%) in acetic acid and 31a–31m clearly established that the diols can be used

at room temperature afforded 4-arylnaphtho[b]thiophene as suitable starting materials for annulation reactions in-

23a in 84% yield (Table 1, Entry 1). Similarly, the reaction stead of the corresponding acetates/pivalates.^[21,22]

of diols 22b–22d with HBr (33%) in acetic acid furnished

Towards further generalizing the above-mentioned annu-

5-aryl-cyclopenta[b]anthracenes 23b–23d in 81–94% yields lation reaction, the preparation of naphthalene-2,3-diols

(Table 1, Entry 2). Unsymmetrical diol 22e treated with was initiated. The condensation of 1,4-diarylbutane-1,4-di-

HBr (33%) in acetic acid gave naphtho[b]thiophene 23e in one 32a–32e^[28]with phthalaldehyde followed by NaBH₄re-

84% yield (Table 1, Entry 3). Similar set of diols 22f–22h duction of resulting 2,3-diaroylnaphthalenes 33a–33e fur-

underwent facile annulation in the presence of HBr (33%) nished naphthalene diols 34a–34e. Next, known N-hexyl-

in acetic acid to afford respective annulated arenes 23f–23h carbazole naphthalide 36^[29]upon reaction with aryl Grig-

in 83–90% yields (Table 1, Entry 4). Unsymmetrical diol 22i nard reagent followed by an aqueous NH₄Cl workup fur-

1

furnished an inseparable 1:1 mixture (based on H NMR nished keto alcohol 37a/37b. Oxidation of these keto

spectroscopy) of anthracenes 23i and 23iЈ (Table 1, En- alcohols with PCC followed by NaBH₄reduction led to

try 5). However, biphenyl- and naphthalene-based diol 22j naphthalene diol 39a/39b (Scheme 7).

was regioselectively annulated to give 7-(biphenyl-4-yl)-

tetraphene 23j in 87% yield (Table 1, Entry 6). Reaction of

pyrene-tethered unsymmetrical diol 26a with HBr (33%) in

acetic acid underwent facile cyclization at the thiophene

portion to afford 4-pyrenylnaphtho[b]thiophene 27a in 81%

yield (Table 1, Entry 7). Nevertheless, similar annulation of

diols 26b/26c that contain pyrene and phenyl/p-tolyl units

led to the formation of separable mixture of respective an-

nulated arenes 27b/27c and 27bЈ/27cЈ as major and minor

products, respectively (Table 1, Entry 8). In the case of un-

symmetrical diol 26d, the electron-releasing nature of the 4-

methoxyphenyl group has effectively facilitated the cycliza-

tion at the pyrene portion to give annulated arene 27d as

the exclusive product in 91% yield (Table 1, Entry 8). To

our delight, reaction of unsymmetrical diol 26e with HBr

(33%) in acetic acid also produced tetracene 27e as the sole

product (Table 1, Entry 9).

Next, reaction of 9,9Ј-dihexylfluorenediol 30a, which

bears a thiophenyl unit, with HBr (33%) in acetic acid fur-

nished the fluorenyl-naphtho[b]thiophene 31a in 89% yield

(Table 1, Entry 10). In the case of 9,9Ј-dihexylfluorenediols

30b–30d, which bear aryl units, the HBr(33%)-mediated cy-

clization reaction led to the formation of respective fluor-

enyl-anthracenes 31b–31d in good yields (Table 1, En-

try 11). The annulation reactions of dibenzofurandiols 30e–

30h, which bear aryl/heteroaryl units, underwent regioselec-

tive cyclization reaction at the dibenzofuranyl portion to

furnish pentacene derivatives 31e–31h in 81–91% yields

(Table 1, Entry 12). N-Hexylcarbazole-tethered diol 30i,

which bears a thiophene unit, underwent facile annulation

to afford naphth-annelated carbazole 31i and naphtho[b]-

thiophene 31iЈ in 45 and 36% yields, respectively (Table 1,

Entry 13). To our delight, N-hexylcarbazolediol 30j/30k, Scheme 7. Preparation of naphthalene-2,3-diylbis(arylmethanols).

which bears an aryl unit, led to the formation of naphtho-

[b]carbazole 31j and 31k as the exclusive products. Simi-

As expected, cyclization reaction of naphthalene diols

larly, interaction of triphenylamine tethered diol 30l/30m 34a–34e with HBr (33%) in acetic acid furnished annulated

with HBr (33%) in acetic acid led to the isolation of 2- compounds 35a–35e in 68–87% yields, Table 2. In the case

[(diphenylamino)phenyl]-9-arylanthracene 31l/31m in 73 of symmetrical diol 34a, cyclization led to the formation

and 68% yields, respectively. It should be noted that our of 5-phenyltetracene 35a in 71% yield (Table 2, Entry 1).

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Anthracene, Tetracene, and Naphtho[b]thiophene Analogues

Reaction of aryl- and thiophene-based unsymmetrical chromatography failed to give the expected product poss-

naphthalene diol 34b/34c with HBr (33%) in acetic acid ibly as a result of the unstable nature of hexacene 40a/40b.

underwent regioselective annulation at the thiophene unit

In summary, we have accomplished a facile synthesis of

to furnish anthra[b]thiophene 35b/35c. However, under anthracene and naptho[b]thiophene analogues that involves

identical conditions, the cyclization of 1-naphthyl-based di- HBr in acetic acid mediated regioselective cyclization reac-

ols 34d and 34e gave benzotetracene 35d and 35e, respec- tion of unsymmetrical diols. The regioselective cyclization

tively, as exclusive products in 85 and 87% yields, respec- methodology was also found to be applicable for naphthal-

tively. Reaction of N-hexylcarbazole-based naphthalene di- ene diols. Even though, dihydroisobenzofuran was isolated

ols 39a/39b with HBr (33%) in acetic acid failed to produce during the Brønsted acid-mediated cyclization of 1,2-di-

expected hexacene 40a/40b. It should be noted that addition phenylbenzenediol,^[21,25]we did not observed any such di-

of HBr (33%) in acetic acid to a solution of diols 39a/39b hydroisobenzofuran formation during HBr in acetic acid

in acetic acid gave an intense red color. However, even cau- mediated cyclization of a wide variety of the benzene- and

tious workup followed by purification with column naphthalene-based diols. Our present study clearly demon-

strated that an inexpensive HBr in acetic acid system can be

used as an effective Brønsted acid catalyst for regioselective

Table 2. Synthesis of anthracenes and naphtho[b]thiophenes 35a–

cyclization of a wide variety of unsymmetrical diols. More-

35e.

over, the regioselective formation of annulated arenes and

heteroarenes from the diols successfully eliminates the un-

necessary preparation of corresponding acetates/pival-

ates.^[21,22]The wide variety of anthracenes, tetracenes, pent-

acenes, and annulated thiophene derivatives reported herein

may find application in OLEDs.^[30]

Experimental Section

General Methods: Solvents were dried by means of standard pro-

cedures. All the experiments were carried out under a nitrogen at-

mosphere unless otherwise stated. The progress of all reactions was

monitored by TLC with a hexanes/ethyl acetate mixture as eluent.

Column chromatography was carried out with silica gel (230–

400 mesh, Merck) and by eluting with solvents of increasing po-

1

larity. H NMR, ¹³C NMR, and DEPT-135 spectra were recorded

in CDCl₃with tetramethylsilane as an internal standard with a

300 MHz spectrometer at room temperature. HRMS spectra were

recorded with a MAT 95 XL model instrument under EI mode.

2-Benzoylphenyl(thiophen-2-yl)methanone (6a): Ring opening of 3-

(thiophen-2-yl)isobenzofuran-1(3H)-one 3^[24](2.0 g, 9.25 mmol)

with freshly prepared phenylmagnesium bromide followed by an

aqueous NH₄Cl (10 mL) quench and workup gave the keto alcohol.

The crude keto alcohol (2.1 g, 7.14 mmol) was dissolved in dry

CH₂Cl₂(40 mL), PCC (2.3 g, 10.71 mmol) was added and stirred

for 4 h. The reaction mixture was then filtered through a Celite pad

and washed with CH₂Cl₂(2ϫ 10 mL). The combined filtrate was

concentrated under reduced pressure. Purification of the residue by

column chromatography (silica gel; hexane/ethyl acetate, 95:5) led

to the isolation of diketone 6a (0.88 g, 84%) as a brown solid, m.p.

133–135 °C (Lit.^[22]132.5–133.3 °C). ¹H NMR (300 MHz, CDCl₃):

δ = 7.68–7.61 (m, 3 H), 7.57–7.54 (m, 4 H), 7.46–7.40 (m, 2 H),

7.29 (t, J = 7.6 Hz, 2 H), 7.99 (t, J = 4.5 Hz, 1 H) ppm. ¹³C NMR

(75.4 MHz, CDCl₃): δ = 196.6, 188.3, 144.2, 139.8, 139.6, 137.2,

135.0, 134.9, 133.1, 130.5, 130.5, 129.9, 129.8, 129.1, 128.3,

128.2 ppm.

2-(4-Methylbenzoyl)phenyl(thiophen-2-yl)methanone (6b): Ring

opening of lactone 3^[24](2.0 g, 9.25 mmol) with freshly prepared p-

tolylmagnesium bromide followed by an aqueous NH₄Cl (10 mL)

quench gave the keto alcohol. Oxidation of the crude keto alcohol

(2.2 g, 7.14 mmol) with PCC (2.3 g, 10.71 mmol) by following a

procedure similar to that for 6a furnished diketone 6b (0.94 g, 89%)

as a colorless solid, m.p. 124–126 °C. (Lit.^[22]126–128 °C). ¹H

NMR (300 MHz, CDCl₃): δ = 7.74–7.70 (m, 1 H), 7.64–7.59 (m, 6

[a] Unsymmetrical diol (1 equiv.) and HBr (33%) in AcOH

(5 equiv.) at room temperature for 10 min. [b] Yield after column

chromatography.

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H), 7.46 (m, 1 H), 7.17 (d, J = 8.1 Hz, 2 H), 7.06–7.03 (m, 1 H),

2.36 (s, 3 H, CH₃) ppm. ¹³C NMR (75.4 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 ppm. DEPT-135 (75.4 MHz,

CDCl₃): δ = 135.0, 134.8, 130.5, 130.3, 130.0, 129.6, 128.0,

21.7 ppm (only eight signals appeared instead of ten).

132.3, 130.5, 130.2, 129.5, 128.9, 128.3, 126.7, 125.8, 124.1, 113.7,

55.5 ppm. C₂₃H₁₆O₃S₂(404.50): calcd. C 68.29, H 3.99, S 15.85;

found C 68.48, H 3.71, S 15.99.

2,2Ј-Bithiophen-5-yl[2-(1-naphthoyl)phenyl]methanone (9d): Ring

opening of lactone 8^[31](2.0 g, 6.71 mmol) with freshly prepared

1-naphthylmagnesium bromide followed aqueous NH₄Cl (10 mL)

quench gave the keto alcohol. Oxidation of the crude keto alcohol

(2.45 g, 5.75 mmol) with PCC (1.86 g, 8.63 mmol) by following a

procedure similar to that for 9a furnished diketone 9d (2.09 g, 90%)

as a pale yellow solid. The crude diketone was used directly in the

next step without any further characterization.

2-(4-Methoxylbenzoyl)phenyl(thiophen-2-yl)methanone (6c): Ring

opening of lactone 3^[24](2.0 g, 9.25 mmol) with freshly prepared p-

anisylmagnesium bromide followed by an aqueous NH₄Cl (10 mL)

quench gave the keto alcohol. Oxidation of the crude keto alcohol

(1.9, g 5.86 mmol) with PCC (1.89 g, 8.79 mmol) by following a

procedure similar to that for 6a furnished diketone 6c (0.48 g, 91%)

as a colorless solid, m.p. 130–132 °C (Lit.^[22]131–132 °C). ¹H NMR

(300 MHz, CDCl₃): δ = 7.65–7.61 (m, 3 H), 7.56–7.52 (m, 4 H),

7.40–7.39 (m, 1 H), 6.99–6.97 (m, 1 H), 6.77 (d, J = 8.7 Hz, 2 H),

3.76 (s, 3 H, OCH₃) ppm. ¹³C NMR (75.4 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 ppm.

2,2Ј-Bithiophen-5-yl[2-(thiophen-2-ylcarbonyl)phenyl]methanone

(9e): Ring opening of lactone 8^[31](2.0 g, 6.7 mmol) with freshly

prepared 2-thienylmagnesium bromide followed by an aqueous

NH₄Cl (10 mL) quench gave the keto alcohol. Oxidation of the

crude keto alcohol (2.0, 5.34 mmol) with PCC (1.72 g, 21.55 mmol)

by following a procedure similar to that for 9a furnished diketone

9e (1.77 g. 87 %) as a brown solid, m.p. 145–147 °C. ¹H NMR

(300 MHz, CDCl₃): δ = 7.68–7.66 (m, 2 H), 7.60–7.55 (m, 3 H),

7.40 (d, J = 3.9 Hz, 1 H), 7.28–7.22 (m, 3 H), 7.05–6.99 (m, 3

H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 188.3, 187.8, 147.0,

144.1, 142.0, 139.3, 139.1, 136.2, 136.1, 135.2, 135.0, 130.7, 130.6,

129.2, 129.1, 128.3, 128.0, 126.7, 125.9, 124.2 ppm. C₂₀H₁₂O₂S₃

(380.49): calcd. C 63.13, H 3.18, S 25.28; found C 63.26, H 3.13, S

25.35.

2,2Ј-Bithiophen-5-yl(2-benzoylphenyl)methanone (9a): Ring opening

of 3-(2,2Ј-bithiophen-5-yl)isobenzofuran-1(3H)-one 8^[31](2.0 g,

6.71 mmol) with freshly prepared phenylmagnesium bromide fol-

lowed by an aqueous NH₄Cl (10 mL) quench and workup gave the

keto alcohol. The crude keto alcohol (2.4 g, 6.38 mmol) was dis-

solved in dry CH₂Cl₂(40 mL) and PCC (2.07 g, 9.60 mmol) was

added and stirred for 4 h. The reaction mixture was then filtered

through a Celite pad and washed with CH₂Cl₂(2ϫ 10 mL). The

combined filtrate was concentrated under reduced pressure. Purifi-

cation of the residue by column chromatography (silica gel; hexane/

ethyl acetate, 95:5) gave diketone 9a (2.0 g, 91%) as a pale brown

solid, m.p. 156–158 °C. ¹H NMR (300 MHz, CDCl₃): δ = 7.76–

7.70 (m, 3 H), 7.64–7.63 (m, 2 H), 7.57–7.50 (m, 1 H), 7.41–7.35

(m, 3 H), 7.33–7.31 (m, 1 H), 7.29–7.26 (m, 1 H), 7.12–7.10 (m, 2

H), 7.06–7.03 (m, 1 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ =

196.6, 187.8, 146.9, 142.1, 139.6, 137.2, 136.2, 135.9, 133.1, 130.5,

129.8, 129.7, 129.0, 128.5, 128.3, 127.8, 126.8, 126.7, 125.9,

124.1 ppm. C₂₂H₁₄O₂S₂(374.47): calcd. C 70.56, H 3.77, S 17.13;

found C 70.42, H 3.61, S 17.32.

Annulation of {2-[Hydroxy(phenyl)methyl]phenyl}(thiophen-2-yl)-

methanol (7a) with BF₃·OEt₂: To a solution of diketone 6a (1 g,

3.4 mmol) in THF/ethanol (20 mL; 1:3) sodium borohydride

(0.64 g, 16.8 mmol) was added in portions and heated at reflux for

4 h. The reaction mixture was then poured into water (100 mL),

extracted with ethyl acetate (2ϫ 20 mL) and dried (Na₂SO₄). The

removal of solvent gave crude diol 7a. Crude diol 7a (0.30 g,

1 mmol) was dissolved in dry CH₂Cl₂(15 mL), a catalytic amount

of BF₃·OEt₂(0.025 g, 0.2 mmol) was added and stirred for 1.5 h

under a nitrogen atmosphere. The reaction mixture was then

poured into water (40 mL), extracted with CH₂Cl₂(2ϫ 10 mL) and

dried (Na₂SO₄). The removal of solvent in vacuo followed by col-

umn chromatographic purification (silica gel; hexane) afforded

compound 13a (0.21 g, 80%) as a pale yellow solid, m.p. 82–83 °C.

¹H NMR (300 MHz, CDCl₃): δ = 8.46 (s, 1 H), 8.02 (d, J = 8.4 Hz,

1 H), 7.90 (d, J = 8.1 Hz, 1 H), 7.60–7.44 (m, 9 H) ppm. ¹³C NMR

(75.4 MHz, CDCl₃): δ = 139.3, 139.1, 138.3, 133.3, 131.6, 130.1,

128.9, 128.9, 128.6, 128.2, 125.4, 125.3, 124.8, 123.9, 121.6 ppm

(only fifteen signals appeared instead of sixteen). DEPT-135

(75.4 MHz, CDCl₃): δ = 130.1, 128.9, 128.9, 128.6, 128.2, 125.4,

125.3, 124.8, 123.9, 121.6 ppm.

2,2Ј-Bithiophen-5-yl[2-(4-methylbenzoyl)phenyl]methanone

(9b):

Ring opening of lactone 8^[31]with freshly prepared p-tolylmagne-

sium bromide followed by an aqueous NH₄Cl (10 mL) quench gave

the keto alcohol. Oxidation of the crude keto alcohol (2.0,

4.22 mmol) with PCC (1.60 g, 3.62 mmol) by following a procedure

similar to that for 9a furnished diketone 9b (0.45 g, 90%) as a pale

yellow solid, m.p. 140–142 °C. ¹H NMR (300 MHz, CDCl₃): δ =

7.67–7.64 (m, 1 H), 7.56–7.50 (m, 5 H), 7.30–7.18 (m, 3 H), 7.1 (d,

J = 8.1 Hz, 2 H), 7.03 (d, J = 3.9 Hz, 1 H), 6.98–6.94 (m, 1 H),

2.31 (s, 3 H) ppm. ¹³C NMR (75.4 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, 128.2, 126.6, 125.8, 124.1, 21.7 ppm.

C₂₃H₁₆O₂S₂(388.50): calcd. C 71.11, H 4.15, S 16.51; found C

71.05, H 4.09, S 16.57.

Annulation of {2-[Hydroxyl(phenyl)methyl]phenyl}(thiophen-2-yl)-

methanol (7a) with 33% HBr in AcOH: To a solution of crude

diol 7a (0.3 g, 1 mmol) in acetic acid (15 mL), HBr (33%, 1.24 g,

15.2 mmol) in acetic acid was added and stirred for 10 min. The

reaction mixture was then poured into water (80 mL), extracted

with CH₂Cl₂(2ϫ 20 mL), and dried (Na₂SO₄). The removal of

solvent in vacuo followed by column chromatographic purification

(silica gel; hexane) afforded compound 13a (0.22 g, 81%).

2,2Ј-Bithiophen-5-yl[2-(4-methoxybenzoyl)phenyl]methanone

(9c):

Ring opening of lactone 8^[31](2.0 g, 6.71 mmol) with freshly pre-

pared p-anisylmagnesium bromide followed by an aqueous NH₄Cl

(10 mL) quench gave the keto alcohol. Oxidation of the crude keto

alcohol (2.5, g 6.16 mmol) with PCC (1.99 g, 9.23 mmol) by follow-

ing a procedure similar to that for 9a furnished diketone 9c (2.10 g,

Annulation of {2-[Hydroxy(p-tolyl)methyl]phenyl}(thiophen-2-yl)-

methanol (7b) with BF₃·OEt₂: Reduction of diketone 6b (1 g,

3.26 mmol) with sodium borohydride (0.6 g, 16.32 mmol) followed

by workup led to diol 7b. Crude diol 7b (0.34 g, 1.1 mmol) upon

annulation with BF₃·OEt₂(0.030 g, 0.22 mmol) by adopting a pro-

1

88%) as a pale green solid, m.p. 120–122 °C. H NMR (300 MHz,

CDCl₃): δ = 7.70 (d, J = 8.4 Hz, 3 H), 7.61–7.55 (m, 3 H), 7.35–

7.27 (m, 3 H), 7.10–7.09 (m, 1 H), 7.04–7.03 (m, 1 H), 6.85 (d, J cedure similar to that for 7a afforded compound 13b (0.24 g, 78%)

= 8.4 Hz, 2 H), 3.83 (s, 3 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): as a pale yellow solid, m.p. 110–111 °C (Lit.^[22]107–109 °C). ¹H

δ = 195.2, 188.0, 163.6, 146.8, 142.1, 140.0, 139.3, 136.3, 136.0,

NMR (300 MHz, CDCl₃): δ = 8.36 (s, 1 H, ArH), 7.90 (d, J =

7822

www.eurjoc.org

Eur. J. Org. Chem. 2015, 7816–7835

Anthracene, Tetracene, and Naphtho[b]thiophene Analogues

8.1 Hz, 1 H, ArH), 8.1 (d, J = 10.2 Hz, 1 H, ArH), 7.46–7.31 (m,

7 H, ArH), 7.11 (d, J = 7.8 Hz, 1 H, ArH), 2.47 (s, 3 H, CH₃) ppm.

¹³C NMR (75.4 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 ppm.

= 9 Hz, 1 H), 7.39–7.17 (m, 8 H), 7.09 (s, 1 H), 6.95 (t, J = 4.3 Hz,

1 H), 2.44 (s, 3 H) ppm. ¹³C NMR (75.4 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 ppm. C₂₃H₁₆S₂(356.50): calcd. C 77.49, H 4.52, S 17.99; found

C 77.61, H 4.38, S 17.81.

Annulation of {2-[Hydroxyl(p-tolyl)methyl]phenyl}(thiophen-2-yl)-

methanol (7b) with 33 % HBr in AcOH: Crude diol 7b (0.17 g,

0.55 mmol) upon annulation with HBr (33%, 0.67 g, 8.27 mmol) in

acetic acid by adopting a procedure similar to that for 7a afforded

13b (0.12 g, 82%).

Annulation of 2,2Ј-Bithiophen-5-yl{2-[hydroxy(p-tolyl)methyl]-

phenyl}methanol (10b) with BF₃·OEt₂: Crude diol 7c (0.62 g,

1.58 mmol) upon annulation with BF₃·OEt₂(0.04 g, 0.31 mmol) in

dry CH₂Cl₂by adopting a procedure similar to that for 7a afforded

14b (0.42 g, 76%).

Annulation of {2-[Hydroxy(4-methoxyphenyl)methyl]phenyl}(thio-

phen-2-yl)methanol (7c) with BF₃·OEt₂: Reduction of diketone 6c

(1.4 g, 4.34 mmol) with sodium borohydride (0.8 g, 21.72 mmol)

followed by workup led to diol 7c. Crude diol 7c (0.4 g, 1.22 mmol)

upon annulation with BF₃·OEt₂(0.04 g, 0.03 mmol) in dry CH₂Cl₂

by adopting a procedure similar to that for 7a afforded compound

13c (0.29 g, 82%) as a pale yellow solid, m.p. 151–153 °C (Lit.^[22]

152–153 °C). ¹H NMR (300 MHz, CDCl₃): δ = 8.37 (s, 1 H, ArH),

7.92 (d, J = 8.1 Hz, 1 H, ArH), 7.82 (d, J = 8.4 Hz, 1 H, ArH),

7.50–7.33 (m, 5 H, ArH), 7.14–1.06 (m, 3 H, ArH), 3.91 (s, 3 H,

OCH₃) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 159.09, 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 ppm. DEPT-135 (75.4 MHz,

CDCl₃): δ = 135.1, 134.8, 132.2, 130.5, 129.4, 129.0, 128.0, 113.6,

55.5 ppm (only nine signals appeared instead of ten).

4-(4-Methoxyphenyl)-2-(thiophen-2-yl)naphtho[2,3-b]thiophene

(14c): Reduction of diketone 9c (0.60 g, 1.49 mmol) with sodium

borohydride (0.25 g, 6.58 mmol) followed by workup led to diol

10c. Crude diol 10c (0.67 g, 1.64 mmol) upon annulation with HBr

(33%, 0.66 g, 8.15 mmol) in acetic acid by adopting a procedure

similar to that for 14a afforded compound 14c (0.53 g, 87%) as a

1

pale green solid, m.p. 188–190 °C. H NMR (300 MHz, CDCl₃): δ

= 8.21 (s, 1 H), 7.98 (d, J = 8.1 Hz, 1 H), 7.80–7.75 (m, 1 H), 7.53–

7.50 (m, 3 H), 7.43 (t, J = 7.8 Hz, 1 H), 7.32–7.28 (m, 3 H), 7.13

(d, J = 8.1 Hz, 1 H), 7.06–7.03 (m, 1 H), 3.94 (s, 3 H) ppm. ¹³C

NMR (75.4 MHz, CDCl₃): δ = 159.1, 139.1, 137.8, 137.3, 131.8,

131.5, 131.2, 130.9, 130.0, 127.9, 127.5, 126.4, 125.9, 125.7, 125.1,

125.0, 120.9, 119.7, 114.3, 114.0, 55.4 ppm. HRMS (EI): calcd for

C₂₃H₁₆OS₂[M⁺] 372.0643; found 372.0640.

Annulation of 2,2Ј-Bithiophen-5-yl{2-[hydroxy(4-methoxyphenyl)-

methyl]phenyl}methanol (10c) with BF₃·OEt₂: Crude diol 7c (0.64 g,

1.54 mmol) upon annulation with BF₃·OEt₂(0.04 g, 0.30 mmol) in

dry CH₂Cl₂by adopting a procedure similar to that for 7a afforded

14c (0.48 g, 87%).

Annulation of {2-[Hydroxyl(4-methoxyphenyl)methyl]phenyl} (thio-

phen-2-yl)methanol (7c) with 33% HBr in AcOH: Crude diol 7c

(0.2 g, 0.61 mmol) upon annulation with HBr (33 %, 0.74 g,

9.2 mmol) in acetic acid by adopting a procedure similar to that

for 7a afforded 13c (0.155 g, 87%).

5-(Tetraphen-7-yl)-2,2Ј-bithiophene (14d): Reduction of diketone 9d

(0.60 g, 1.42 mmol) with sodium borohydride (0.26 g, 6.84 mmol)

followed by workup led to diol 10d. Crude diol 10d (0.60 g,

1.40 mmol) upon annulation with HBr (33%, 0.50 g, 21.0 mmol) in

acetic acid by adopting a procedure similar to that for 14a afforded

compound 14d (0.47 g, 86 %) as a pale green solid, m.p. 150–

4-Phenyl-2-(thiophen-2-yl)naphtho[2,3-b]thiophene (14a): Reduction

of diketone 9a (0.92 g, 2.37 mmol) with sodium borohydride

(0.45 g, 11.8 mmol) followed by workup led to diol 10a. Crude diol

10a (0.63 g, 1.67 mmol) was dissolved in acetic acid (15 mL) and

HBr (33%, 0.67 g, 8.27 mmol) in acetic acid was added and stirred

for 10 min. The reaction mixture was then poured into water

(80 mL), extracted with CH₂Cl₂(2ϫ 20 mL), and dried (Na₂SO₄).

The removal of solvent in vacuo followed by column chromato-

graphic purification (silica gel; hexane/ethyl acetate, 99:1) afforded

compound 14a (0.46 g, 81 %) as a pale yellow solid, m.p. 166–

1

152 °C. H NMR (300 MHz, CDCl₃): δ = 9.27 (s, 1 H), 8.86 (d, J

= 8.1 Hz, 1 H), 8.14 (d, J = 7.8 Hz, 1 H), 7.98 (d, J = 8.4 Hz, 1

H), 7.83–7.79 (m, 2 H), 7.72–7.67 (m, 1 H), 7.63–7.48 (m, 4 H),

7.38–7.36 (m, 1 H), 7.26–7.24 (m, 2 H) ppm. ¹³C NMR (75.4 MHz,

CDCl₃): δ = 138.8, 138.2, 137.4, 132.3, 131.6, 131.4, 130.6, 130.4,

130.3, 128.7, 128.6, 128.5, 127.9, 127.7, 127.3, 127.1, 126.4, 126.3,

125.7, 125.2, 124.5, 123.8, 123.5, 123.4, 123.1 ppm. HRMS (EI):

calcd. for C₂₆H₁₆S₂[M⁺] 392.0693; found 392.0679.

1

168 °C. H NMR (300 MHz, CDCl₃): δ = 8.27 (s, 1 H), 7.90 (d, J

= 8.1 Hz, 1 H), 7.74 (d, J = 9.3 Hz, 1 H), 7.60–7.55 (m, 2 H), 7.50–

7.43 (m, 4 H), 7.37–7.33 (m, 1 H), 7.29–7.26 (m, 2 H), 7.14 (s, 1

H), 7.04–7.02 (m, 1 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ =

138.8, 138.7, 138.0, 137.4, 137.3, 134.2, 131.4, 130.0, 129.6, 128.5,

128.0, 127.7, 126.3, 126.0, 125.7, 125.2, 125.1, 123.8, 120.0,

119.0 ppm. HRMS (EI): calcd. for C₂₂H₁₄S₂[M⁺] 342.0537; found

342.0500.

Annulation of 2,2Ј-Bithiophen-5-yl{2-[hydroxy(naphthalen-1-yl)-

methyl]phenyl}methanol (10d) with BF₃·OEt₂: Crude diol 7d (0.6 g,

1.40 mmol) upon annulation with BF₃·OEt₂(0.04 g, 0.28 mmol) in

dry CH₂Cl₂by adopting a procedure similar to that for 7a afforded

14d (0.23 g, 85%).

Annulation of 2,2Ј-Bithiophen-5-yl{2-[hydroxy(phenyl)meth-

yl]phenyl}methanol (10a) with BF₃.OEt₂: Crude diol 10a (0.29 g,

0.77 mmol) upon annulation with BF₃·OEt₂(0.02 g, 0.15 mmol) in

dry CH₂Cl₂by adopting a procedure similar to that for 7a afforded

14a (0.20 g, 78%).

Preparation of Naphtho[b]thiophenes 14e and 14eЈ: Reduction of di-

ketone 9e (0.61 g, 1.60 mmol) with sodium borohydride (0.30 g,

7.89 mmol) followed by workup led to diol 10e. Crude diol 10e

(0.59 g, 1.54 mmol) upon annulation with HBr (33 %, 0.62 g,

22.99 mmol) in acetic acid by adopting a procedure similar to that

for 14a followed by column chromatographic purification (silica

gel; hexane/ethyl acetate, 99:1) led to the isolation of products 14e

and 14eЈ.

2-(Thiophen-2-yl)-4-p-tolylnaphtho[2,3-b]thiophene (14b): Reduction

of diketone 9b (0.75 g, 1.94 mmol) with sodium borohydride

(0.29 g, 7.77 mmol) followed by workup led to diol 10b. Crude diol

10b (0.63 g, 1.67 mmol) upon annulation with HBr (33%, 0.65 g,

8.03 mmol) in acetic acid by adopting a procedure similar to that

2,4-Di(thiophen-2-yl)naphtho[2,3-b]thiophene (14e): Pale green solid,

1

for 14a afforded compound 14b (0.57 g, 82%) as a pale yellow so-

0.28 g (52%), m.p. 140–142 °C. H NMR (300 MHz, CDCl₃): δ =

1

lid, m.p. 190–192 °C. H NMR (300 MHz, CDCl₃): δ = 8.18 (s, 1 8.42 (s, 1 H), 8.12 (d, J = 8.1 Hz, 1 H), 7.94 (d, J = 8.1 Hz, 1 H),

H), 7.82 (d, J = 8.4 Hz, 1 H), 7.69 (d, J = 8.4 Hz, 1 H), 7.43 (d, J 7.52–7.45 (m, 3 H), 7.42–7.40 (m, 1 H), 7.31 (d, J = 3.6 Hz, 1 H),

Eur. J. Org. Chem. 2015, 7816–7835

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7823

A. K. Mohanakrishnan et al.

FULL PAPER

7.26–7.24 (m, 2 H), 7.11 (d, J = 3.6 Hz, 1 H), 7.04 (m, 1 H) ppm.

¹³C NMR (75.4 MHz, CDCl₃): δ = 139.4, 138.5, 138.0, 137.7,

137.3, 131.0, 130.3, 129.6, 128.5, 127.9, 127.6, 126.1, 125.8, 125.6,

furan (16b; 0.49 g, 1.7 mmol) in dry CH₂Cl₂(15 mL), CF₃SO₃H

(0.26 g, 1.73 mmol) was added and allowed to stir for 12 h followed

by workup with a procedure similar to that for 7a afforded 9-phen-

125.4, 124.5, 123.8, 123.7, 121.8 ppm. HRMS (EI): calcd. for ylanthracene 15b (0.32 g, 74%) as a yellow solid, m.p. 153–155 °C

1

C₂₀H₁₂S₃[M⁺] 348.0101; found 348.0100.

(Lit.^[19]155–157 °C). H NMR (300 MHz, CDCl₃): δ = 8.49 (s, 1

H), 8.03 (d, J = 8.4 Hz, 2 H), 7.66 (d, J = 8.4 Hz, 2 H), 7.52–7.60

(m, 3 H), 7.41–7.47 (m, 4 H), 7.31–7.36 (m, 2 H) ppm. ¹³C NMR

(75.4 MHz, CDCl₃): δ = 138.7, 136.9, 131.3, 131.2, 130.1, 128.3,

128.3, 127.4, 126.5, 125.3, 125.1 ppm (only eleven signals observed

instead of twelve).

4-(2,2Ј-Bithiophen-5-yl)naphtho[2,3-b]thiophene (14eЈ): Pale green

solid, 0.24 g (43%), m.p. 140–142 °C. ¹H NMR (300 MHz, CDCl₃):

δ = 8.36 (s, 1 H), 8.21–8.13 (m, 1 H), 8.03–7.97 (m, 1 H), 7.52–7.45

(m, 4 H), 7.35 (d, J = 3.6 Hz, 1 H), 7.28–7.25 (m, 3 H), 7.08–7.05

(m, 1 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 141.1, 138.8,

138.3, 138.0, 137.2, 131.5, 130.0, 129.5, 128.9, 128.6, 127.9, 125.9,

125.0, 124.6, 124.0, 123.9, 123.8, 122.7, 122.1, 119.1 ppm. C₂₀H₁₂S₃

(348.49): calcd. C 68.93, H 3.47, S 27.60; found C 68.84, H 3.59, S

27.48.

Annulation of 1,2-Phenylenebis(phenylmethanol) (12b) with 33%

HBr in Acetic Acid: Diol 12b (0.2 g, 0.68 mmol) upon annulation

with HBr (33%, 2.03 g, 25.09 mmol) in acetic acid by adopting a

procedure similar to that for 7a afforded 17^[32](0.22 g, 84%) as a

yellow solid, m.p. 132–134 °C. ¹H NMR (300 MHz, CDCl₃): δ =

8.50 (d, J = 9 Hz, 2 H), 7.55 (d, J = 9 Hz, 2 H), 7.56–7.43 (m, 4

H), 7.30–7.23 (m, 5 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ =

138.4, 137.8, 131.2, 131.1, 130.2, 128.5, 127.9, 127.8, 127.4, 127.0,

125.6, 122.8 ppm.

Annulation of 2,2Ј-Bithiophen-5-yl{2-[hydroxy(thiophen-2-yl)-

methyl]phenyl}methanol (10e) with BF₃·OEt₂: Crude diol 7e (0.6 g,

1.56 mmol) upon annulation with BF₃·OEt₂(0.04 g, 0.3 mmol) in

dry CH₂Cl₂by adopting a procedure similar to that for 7a afforded

14e (0.30 g, 55%) and 14eЈ (0.14 g, 35%).

2-Methyl-9-p-tolylanthracene (15c): Diol 12b (0.5 g, 1.58 mmol)

upon annulation with HBr (33%, 1.92 g, 23.73 mmol) in acetic acid

by adopting a procedure similar to that for 14a afforded 15c^[21]

Annulation of 1,2-Phenylenebis(thiophen-2-ylmethanol) (12a) with

BF₃·OEt₂: To a solution of 1,2-phenylenebis(thiophen-2-yl-

methanol) (12a; 0.25 g, 0.84 mmol) in dry CH₂Cl₂(10 mL), a cata-

lytic amount of BF₃·OEt₂(0.021 g, 0.16 mmol) was added and al-

lowed to stir for 2 h followed by workup in a procedure similar to

that for 7a afforded 15a^[21]as a sticky liquid (0.17 g, 80%). ¹H

NMR (300 MHz, CDCl₃): δ = 8.34 (s, 1 H), 8.02–7.98 (m, 2 H),

7.56 (dd, J = 4.8, 1.2 Hz, 1 H), 7.48–7.40 (m, 3 H), 7.24–7.33 (m,

3 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 141.4, 139.3, 138.3,

131.6, 130.2, 129.0, 128.8, 128.7, 127.6, 126.9, 125.9, 125.8, 125.2,

125.1, 123.9, 122.7 ppm.

1

(0.36 g, 81%) as a sticky liquid, H NMR (300 MHz, CDCl₃): δ =

8.3 (s, 1 H), 7.88 (d, J = 8.1 Hz, 1 H), 7.82 (d, J = 8.4 Hz, 1 H),

7.54 (d, J = 8.4 Hz, 1 H), 7.34–7.16 (m, 8 H), 2.41 (s, 3 H), 2.29

(s, 3 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 136.9, 136.1,

135.9, 134.9, 131.2, 130.9, 130.6, 130.1, 129.5, 129.1, 128.4, 128.3,

128.0, 127.9, 126.2, 125.2, 125.0, 124.7, 22.3, 21.5 ppm.

Annulation of 1,2-Phenylenebis(thiophen-2-ylmethanol) (12a) with

Triflic Acid: A solution of 1,2-phenylenebis(thiophen-2-yl-

methanol) (12a; 0.25 g, 0.84 mmol) in dry CH₂Cl₂(10 mL),

CF₃SO₃H (0.056 g, 0.37 mmol) was added and allowed to stir at

room temperature for 30 min. Subsequent aqueous NaHCO₃

quench followed by usual workup afforded a 1:5 mixture (based on

¹H NMR spectroscopy) of 1,3-di(thiophen-2-yl)-1,3-dihydroisob-

enzofuran (16a) and 4-(thiophen-2-yl)naphtho[2,3-b]thiophene

(15a) as a thick liquid. The mixture of dihydroisobenzofuran 16a

and naphtho[2,3-b]thiophene 15a upon further reaction with

CF₃SO₃H (0.18 g, 1.2 mmol) in CH₂Cl₂(10 mL) for 1 h followed

by workup and column chromatographic purification afforded 4-

(thiophen-2-yl)naphtho[2,3-b]thiophene (15a; 0.16 g, 81%).

Annulation of 1,2-Phenylenebis(thiophen-2-ylmethanol) (12a) with

ZnBr₂: A solution of 1,2-phenylenebis(thiophen-2-ylmethanol)

(12a; 0.25 g, 0.84 mmol) in dry CH₂Cl₂(10 mL) a catalytic amount

of ZnBr₂(0.038 g, 0.16 mmol) was added and allowed to stir for

8 h followed by workup as mentioned above furnished 15a (0.16 g,

75%).

Annulation of 1,2-Phenylenebis(thiophen-2-ylmethanol) (12a) with

33% HBr in acetic acid: Diol 12a (0.5 g, 1.67 mmol) upon annu-

lation with HBr (33%, 2.16 g, 26.1 mmol) in acetic acid by adopt-

ing a procedure similar to that for 7a afforded 15a as a thick liquid

(0.37 g, 83%).

Annulation of 1,2-Phenylenebis(phenylmethanol) (12b) with Triflic

Acid: A solution of 1,2-phenylenebis(phenylmethanol) (12b; 0.49 g,

1.7 mmol) in dry CH₂Cl₂(10 mL), CF₃SO₃H (0.076 g, 0.50 mmol)

was added and allowed to stir at room temperature for 6 h. Subse-

quent aqueous NaHCO₃quench followed by usual workup af-

forded a 1:2.5 mixture (based on ¹H NMR spectroscopy) of 1,3-

diphenyl-1,3-dihydroisobenzofuran (16b) and 9-phenylanthracene

(15b) as a yellow liquid. The mixture of dihydroisobenzofuran 16b

and phenylanthracene 15b upon further reaction with CF₃SO₃H

(0.23 g, 1.52 mmol) in CH₂Cl₂(10 mL) for 2 h followed by workup

and column chromatographic purification afforded 9-phenylan-

thracene (15b; 0.26 g, 75%).

Annulation of 1,2-Phenylenebis(phenylmethanol) (12b) with BF₃·

OEt₂: To a solution of 1,2-phenylenebis(thiophen-2-ylmeth-

anol) (12a; 0.25 g, 0.85 mmol) in dry CH₂Cl₂(10 mL), BF₃·OEt₂

(0.1 g, 0.85 mmol) was added and allowed to stir for 12 h followed

by workup in a procedure similar to that for 7a afforded dihydrois-

obenzofuran 16b^[21](0.19 g, 82 %) as a thick liquid. ¹H NMR

(300 MHz, CDCl₃): δ = 7.22–7.44 (m), 7.10–7.13 (m), 7.00–7.03

(m), 6.44 (s), 6.20 (s) ppm (mixture of diastereomers). ¹³C NMR

(75.4 MHz, CDCl₃): δ = 142.5, 142.1, 141.7, 141.2, 128.6, 128.5,

128.2, 128.0, 127.9, 127.8, 126.9, 122.3, 122.1, 85.9, 85.5 ppm (mix-

ture of diastereomers).

(2,3-Dihydro-1H-inden-5-yl)[2-(thiophen-2-ylcarbonyl)phenyl]meth-

anone (21a): Ring opening of 3-(2,3-dihydro-1H-inden-5-yl)iso-

benzofuran-1(3H)-one (2.0 g, 8.0 mmol) with freshly prepared 2-

thienylmagnesium bromide followed by acidic workup gave

benzo[c]furan 20a as a fluorescent bright yellow solid. To a stirred

solution of benzo[c]furan 20a (0.74 g, 2.34 mmol) in CH₂Cl₂

(20 mL), MnO₂(0.61 g, 7.12 mmol) was added and stirred for 4 h.

The reaction mixture was then filtered through a Celite pad and

Annulation of 1,2-Phenylenebis(phenylmethanol) (12b) with ZnBr₂:

To a solution of 1,2-phenylenebis(thiophen-2-ylmethanol) (12a;

0.25 g, 0.85 mmol) in dry CH₂Cl₂(10 mL), ZnBr₂(0.19 g,

0.85 mmol) was added and allowed to stir for 12 h followed by

workup with the above mentioned procedure afforded dihydroisob-

enzofuran 16b^[21](0.195 g, 84%).

Annulation of 1,3-Diphenyl-1,3-dihydroisobenzofuran (16b) with

Triflic Acid: To a solution of 1,3-diphenyl-1,3-dihydroisobenzo- washed with CH₂Cl₂(2ϫ 10 mL). The combined filtrate was con-

7824 Eur. J. Org. Chem. 2015, 7816–7835

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Anthracene, Tetracene, and Naphtho[b]thiophene Analogues

centrated under reduced pressure and crystallization from meth-

196.3, 150.2, 144.5, 143.8, 140.5, 140.2, 135.8, 134.8, 130.1, 129.5,

129.4, 129.0, 128.6, 125.7, 124.1, 33.0, 32.5, 25.3, 21.7 ppm.

anol furnished 21a (0.67 g, 86 %) as a brown solid, m.p. 132–

134 °C. ¹H NMR (300 MHz, CDCl₃): δ = 7.74–7.71 (m, 1 H), 7.64– C₂₄H₂₀O₂(340.42): calcd. C 84.68, H 5.92; found C 84.51, H 6.04.

7.60 (m, 4 H), 7.57 (d, J = 6.3 Hz, 1 H), 7.51–7.48 (m, 2 H), 7.20

5-p-Tolyl-2,3-dihydro-1H-cyclopenta[b]anthracene (23c): Reduction

(d, J = 7.5 Hz, 1 H), 2.93–2.83 (m, 4 H), 2.11–2.01 (m, 2 H) ppm.

of diketone 21c (0.68 g, 2.0 mmol) with sodium borohydride

¹³C NMR (75.4 MHz, CDCl₃): δ = 196.6, 188.3, 150.4, 144.6,

(0.38 g, 10 mmol) followed by workup led to diol 22c. Crude diol

144.2, 140.2, 139.7, 135.6, 134.9, 134.6, 130.4, 130.2, 129.6, 129.0,

22c (0.79 g, 2.33 mmol) upon annulation with HBr (33%, 0.95 g,

128.6, 128.0, 125.8, 124.1, 33.0, 32.5, 25.3 ppm. C₂₁H₁₆O₂S

11.73 mmol) in acetic acid by adopting a procedure similar to that

(332.42): calcd. C 75.88, H 4.85, S 9.65; found C 75.67, H 4.90, S

9.81.

1

for 14a afforded compound 23c (0.66 g, 92%) as a thick liquid. H

NMR (300 MHz, CDCl₃): δ = 8.37 (s, 1 H), 7.99 (d, J = 8.4 Hz, 1

4-(2,3-Dihydro-1H-inden-4-yl)naphtho[2,3-b]thiophene (23a): Re-

duction of diketone 21a (0.60 g, 1.81 mmol) with sodium boro-

hydride (0.34 g, 8.95 mmol) followed by workup led to diol 22a.

Crude diol 22a (0.54 g, 1.62 mmol) upon annulation with HBr

(33%, 0.65 g, 8.22 mmol) in acetic acid by adopting a procedure

H), 7.83 (s, 1 H), 7.62 (d, J = 8.7 Hz, 1 H), 7.47 (s, 1 H), 7.41–7.37

(m, 3 H), 7.32–7.28 (m, 3 H), 2.95 (t, J = 7.1 Hz, 2 H), 2.53 (s, 3

H), 2.15–2.05 (m, 2 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ =

143.7, 143.2, 137.0, 136.5, 136.4, 131.6, 131.5, 131.4, 131.2, 130.5,

130.2, 129.3, 128.4, 127.0, 125.9, 124.8, 124.7, 120.6, 33.0, 32.7,

similar to that for 14a afforded 23a (0.39 g, 84%) as a pale yellow 26.5, 21.6 ppm. C₂₄H₂₀(308.42): calcd. C 93.46, H 6.54; found C

1

solid, m.p. 190–192 °C. H NMR (300 MHz, CDCl₃): δ = 8.40 (s, 93.32, H 6.62.

1 H), 7.97 (d, J = 8.1 Hz, 1 H), 7.80–7.76 (m, 2 H), 7.62–7.58 (m,

(2,3-Dihydro-1H-inden-5-yl)[2-(4-methoxybenzoyl)phenyl]methan-

2 H), 7.43–7.37 (m, 2 H), 7.34–7.28 (m, 1 H), 7.16–7.15 (m, 1 H),

one (21d): Ring opening of 3-(2,3-dihydro-1H-inden-5-yl)isobenzo-

3.09–2.96 (m, 4 H), 2.16–2.06 (m, 2 H) ppm. ¹³C NMR (75.4 MHz,

furan-1(3H)-one with freshly prepared p-anisylmagnesium bromide

CDCl₃): δ = 144.4, 143.3, 139.7, 131.9, 131.5, 131.2, 130.7, 129.2,

followed by acidic workup gave benzo[c]furan 20d as a fluorescent

128.2, 127.6, 127.2, 127.1, 126.4, 125.3, 124.7, 121.8, 120.1, 32.9,

bright yellow solid. Oxidation of benzo[c]furan 20d (0.67 g,

32.5, 29.2 ppm. HRMS (EI): calcd. for C₂₁H₁₆S [M⁺] 300.0973;

1.97 mmol) with MnO₂(0.51 g, 5.91 mmol) by following a pro-

found 300.0970.

cedure similar to that for 20a afforded diketone 21d (0.65 g, 94%)

(2-Benzoylphenyl)(2,3-dihydro-1H-inden-5-yl)methanone (21b): Ring

opening of 3-(2,3-dihydro-1H-inden-5-yl)isobenzofuran-1(3H)-one

(2.0 g, 8.0 mmol) with freshly prepared phenylmagnesium bromide

followed by acidic workup gave benzo[c]furan 20b as a fluorescent

bright yellow solid. Oxidation of benzo[c]furan 20b (1.5 g,

4.84 mmol) with MnO₂(1.2 g, 13.80 mmol) by following a pro-

cedure similar to that for 20a afforded diketone 21b (1.33 g, 84%)

as a yellow solid, m.p. 96–98 °C. ¹H NMR (300 MHz, CDCl₃): δ

= 7.72–7.69 (m, 2 H), 7.63–7.55 (m, 5 H), 7.53–7.48 (m, 2 H), 7.36

(t, J = 7.5 Hz, 2 H), 7.19 (d, J = 7.8 Hz, 1 H), 2.93–2.83 (m, 4 H),

2.11–2.01 (m, 2 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 196.6,

150.3, 144.6, 140.6, 139.9, 137.3, 135.7, 132.9, 130.0, 129.8, 129.6,

128.8, 128.6, 128.3, 127.2, 125.7, 124.1, 33.0, 32.5, 25.3 ppm.

C₂₃H₁₈O₂(326.39): calcd. C 84.64, H 5.56; found C 84.48, H 5.74.

as a colorless solid, m.p. 100–102 °C. ¹H NMR (300 MHz, CDCl₃):

δ = 7.63–7.60 (m, 2 H), 7.53–7.48 (m, 5 H), 7.41 (d, J = 7.8 Hz, 1

H), 7.12 (d, J = 7.2 Hz, 1 H), 6.79–6.76 (m, 2 H), 3.77 (s, 3 H),

2.86–2.76 (m, 4 H), 2.05–1.95 (m, 2 H) ppm. ¹³C NMR (75.4 MHz,

CDCl₃): δ = 196.7, 195.3, 163.5, 150.2, 144.5, 140.4, 140.3, 135.7,

132.2, 130.0, 130.3, 129.9, 129.5, 129.3, 128.6, 125.7, 124.1, 113.5,

55.5, 33.0, 32.5, 25.3 ppm. C₂₄H₂₀O₃(356.42): calcd. C 80.88, H

5.66; found C 80.62, H 5.79.

5-(4-Methoxyphenyl)-2,3-dihydro-1H-cyclopenta[b]anthracene (23d):

Reduction of diketone 21d (0.65 g, 1.82 mmol) with sodium

borohydride (0.34 g, 8.94 mmol) followed by workup led to diol

22d. Crude diol 22d (0.67 g, 1.86 mmol) upon annulation with HBr

(33%, 0.75 g, 9.26 mmol) in acetic acid by adopting a procedure

similar to that for 14a afforded compound 23d (0.70 g, 94%) as a

1

9-(2,3-Dihydro-1H-inden-4-yl)anthracene (23b): Reduction of diket-

one 21b (1.0 g, 3.07 mmol) with sodium borohydride (0.58 g,

15.26 mmol) followed by workup led to diol 22b. Crude diol 22b

(1.1 g, 3.33 mmol) upon annulation with HBr (33 %, 1.34 g,

16.55 mmol) in acetic acid by adopting a procedure similar to that

for 14a afforded 23b (0.79 g, 81 %) as a thick liquid. ¹H NMR

(300 MHz, CDCl₃): δ = 8.46 (s, 1 H), 8.02 (d, J = 8.4 Hz, 2 H),

7.72 (d, J = 8.7 Hz, 2 H), 7.46–7.42 (m, 3 H), 7.35–7.30 (m, 2 H),

7.27 (s, 1 H), 7.17 (d, J = 7.5 Hz, 2 H), 3.10–2.99 (m, 4 H), 2.25–

2.15 (m, 2 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 144.3,

143.4, 137.8, 136.4, 131.4, 129.1, 128.3, 127.2, 127.1, 126.2, 125.1,

125.0, 124.2, 33.0, 32.9, 25.6 ppm. HRMS (EI): calcd. for C₂₃H₁₈

[M⁺] 294.1409; found 294.1400.

pale yellow solid, m.p. 162–164 °C. H NMR (300 MHz, CDCl₃):

δ = 8.33 (s, 1 H), 7.96 (d, J = 8.4 Hz, 1 H), 7.79 (s, 1 H), 7.63 (d,

J = 8.7 Hz, 1 H), 7.48 (s, 1 H), 7.40–7.37 (m, 4 H), 7.09 (d, J =

8.7 Hz, 2 H), 3.91 (s, 3 H), 3.04 (t, J = 7.2 Hz, 2 H), 2.93 (t, J =

7.2 Hz, 2 H), 2.13–2.05 (m, 2 H) ppm. ¹³C NMR (75.4 MHz,

CDCl₃): δ = 158.9, 143.6, 143.1, 135.9, 132.4, 131.5, 131.4, 131.0,

130.5, 130.2, 128.2, 126.8, 125.7, 124.7, 124.5, 121.9, 120.4, 113.9,

55.4, 32.9, 32.5, 26.3 ppm. HRMS (EI): calcd. for C₂₄H₂₀O [M⁺]

324.1514; found 324.1510.

(5,6,7,8-Tetrahydronaphthalen-2-yl)[2-(thiophen-2-ylcarbonyl)phen-

yl]methanone (21e): Ring opening of 3-(5,6,7,8-tetrahydronaph-

thalen-2-yl)isobenzofuran-1(3H)-one with freshly prepared 2-thien-

ylmagnesium bromide followed by acidic workup gave benzo[c]-

(2,3-Dihydro-1H-inden-5-yl)[2-(4-methylbenzoyl)phenyl]methanone furan 20e as a fluorescent bright yellow solid. Oxidation of benzo[c]-

(21c): Ring opening of 3-(2,3-dihydro-1H-inden-5-yl)isobenzo-

furan-1(3H)-one (2.0 g, 8.0 mmol) with freshly prepared p-tolyl-

magnesium bromide followed by acidic workup gave benzo[c]furan

20c as a fluorescent bright yellow solid. Oxidation of benzo[c]furan

20c (0.75 g, 2.31 mmol) with MnO₂(0.60 g, 6.90 mmol) by follow-

ing a procedure similar to that for 20a afforded diketone 21c

(0.35 g, 94%) as a pale yellow solid, m.p. 108–110 °C. ¹H NMR

(300 MHz, CDCl₃): δ = 7.62–7.56 (m, 7 H), 7.49 (d, J = 7.5 Hz, 1

H), 7.18 (t, J = 7.4 Hz, 3 H), 2.93–2.83 (m, 4 H), 2.37 (s, 3 H),

furan 20e (1.14 g, 3.45 mmol) with MnO₂(0.90 g, 1.35 mmol) by

following a procedure similar to that for 20a afforded diketone 21e

(0.96 g, 81 %) as a brown solid, m.p. 90–92 °C. ¹H NMR

(300 MHz, CDCl₃): δ = 7.74–7.71 (m, 1 H), 7.65–7.59 (m, 4 H),

7.48–7.47 (m, 1 H), 7.42 (d, J = 8.1 Hz, 1 H), 7.08–7.04 (m, 2 H),

2.77–2.69 (m, 4 H), 1.78–1.76 (m, 4 H) ppm. ¹³C NMR (75.4 MHz,

CDCl₃): δ = 196.5, 188.4, 144.2, 143.3, 140.0, 139.7, 137.3, 134.9,

134.6, 130.8, 130.4, 130.2, 129.7, 129.1, 129.0, 128.0, 127.0, 29.7,

29.2, 22.9, 22.8 ppm. C₂₂H₁₈O₂S (346.44): calcd. C 76.27, H 5.24,

2.11–2.04 (m, 2 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 196.7, S 9.26; found C 76.46, H 5.06, S 9.43.

Eur. J. Org. Chem. 2015, 7816–7835

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7825

A. K. Mohanakrishnan et al.

FULL PAPER

4-(5,6,7,8-Tetrahydronaphthalen-1-yl)naphtho[2,3-b]thiophene (23e):

Reduction of diketone 21e (1.0 g, 2.98 mmol) with sodium boro-

hydride (0.55 g, 14.47 mmol) followed by workup led to diol 22e.

Crude diol 22e (0.92 g) upon annulation with HBr (33%, 1.07 g,

39.5 mmol) in acetic acid by adopting a procedure similar to that

for 14a afforded 23e (0.82 g, 84%) as a pale yellow solid, m.p. 174–

176 °C. ¹H NMR (300 MHz, CDCl₃): δ = 8.52 (d, J = 9.0 Hz, 1

H), 8.28 (s, 1 H), 7.76 (d, J = 8.1 Hz, 1 H), 7.61–7.59 (m, 1 H),

7.52–7.50 (m, 2 H), 7.39–7.36 (m, 1 H), 7.34–7.28 (m, 2 H), 7.16–

7.14 (m, 1 H), 3.09–3.06 (m, 2 H), 2.92–2.89 (m, 2 H), 1.89–1.84

(0.70 g, 1.97 mmol) upon annulation with HBr (33 %, 0.79 g,

9.76 mmol) in acetic acid by adopting a procedure similar to that

for 14a afforded compound 23g (0.56 g, 89%) as a thick liquid. H

1

NMR (300 MHz, CDCl₃): δ = 8.36 (s, 1 H), 7.95 (d, J = 8.1 Hz, 1

H), 7.77 (d, J = 7.8 Hz, 1 H), 7.46 (d, J = 9.0 Hz, 1 H), 7.38–7.36

(m, 2 H), 7.29–7.26 (m, 3 H), 7.23–7.22 (m, 1 H), 7.12 (d, J =

8.7 Hz, 1 H), 2.92–2.87 (m, 2 H), 2.50 (s, 3 H), 2.33 (t, J = 6 Hz,

2 H), 1.70–1.65 (m, 2 H), 1.53–1.48 (m, 2 H) ppm. ¹³C NMR

(75.4 MHz, CDCl₃): δ = 140.1, 136.5, 136.1, 135.1, 133.5, 132.4,

131.7, 131.3, 131.2, 130.4, 129.1, 128.4, 128.3, 127.8, 127.1, 125.1,

(m, 4 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 138.9, 138.5, 124.6, 31.8, 31.3, 24.1, 22.3, 21.5 ppm. HRMS (EI): calcd. for

137.4, 132.1, 129.7, 129.5, 129.3, 128.1, 127.7, 127.1, 127.0, 126.8,

126.4, 126.0, 125.4, 125.1, 123.1, 30.1, 29.9, 23.2, 23.1 ppm. HRMS

(EI): calcd. for C₂₂H₁₈S [M⁺] 314.1129; found 314.1120.

C₂₅H₂₂[M⁺] 322.1722; found 322.1720.

[2-(4-Methoxybenzoyl)phenyl](5,6,7,8-tetrahydronaphthalen-2-yl)-

methanone (21h): Ring opening of 3-(5,6,7,8-tetrahydronaphthalen-

(2-Benzoylphenyl)(5,6,7,8-tetrahydronaphthalen-2-yl)methanone 2-yl)isobenzofuran-1(3H)-one (2.0 g, 7.58 mmol) with freshly pre-

(21f): Ring opening of 3-(5,6,7,8-tetrahydronaphthalen-2-yl)iso-

benzofuran-1(3H)-one with freshly prepared phenylmagnesium

bromide followed by acidic workup gave benzo[c]furan 20f as a

fluorescent bright yellow solid. Oxidation of benzo[c]furan 20f

(0.92 g, 2.84 mmol) with MnO₂(0.74 g, 8.51 mmol) by following a

procedure similar to that for 20a afforded diketone 21f (0.83 g,

86 %) as a yellow solid, m.p. 70–72 °C. ¹H NMR (300 MHz,

pared p-anisylmagnesium bromide followed by acidic workup gave

benzo[c]furan 20h as a fluorescent bright yellow solid. Oxidation

of benzo[c]furan 20h (1.0 g, 2.70 mmol) with MnO₂(0.71 g,

8.17 mmol) by following a procedure similar to that for 20a af-

forded diketone 21h (0.92 g, 88 %) as a thick liquid. ¹H NMR

(300 MHz, CDCl₃): δ = 7.70–7.69 (m, 1 H), 7.68–7.67 (m, 1 H),

7.60–7.57 (m, 4 H), 7.41 (d, J = 6.3 Hz, 2 H), 7.04 (d, J = 8.4 Hz,

CDCl₃): δ = 7.71–7.68 (m, 2 H), 7.59–7.55 (m, 4 H), 7.47–7.40 (m, 1 H), 6.85 (d, J = 8.7 Hz, 2 H), 3.84 (s, 3 H), 2.77–2.70 (m, 4 H),

3 H), 7.34 (t, J = 7.7 Hz, 2 H), 7.02 (d, J = 8.4 Hz, 1 H), 2.73–2.67

(m, 4 H), 1.74–1.72 (m, 4 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃):

δ = 196.6, 196.5, 143.2, 140.5, 139.9, 137.3, 134.7, 132.9, 130.7,

130.4, 130.1, 129.8, 129.6, 129.5, 129.1, 128.3, 127.0, 29.7, 29.3,

22.9, 22.8 ppm. C₂₄H₂₀O₂(340.42): calcd. C 84.68, H 5.92; found

C 84.57, H 6.11.

1.78–1.76 (m, 4 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 196.6,

195.3, 163.5, 143.2, 140.4, 140.2, 137.2, 134.7, 132.2, 130.7, 130.4,

130.0, 129.9, 129.5, 129.3, 129.1, 127.1, 113.6, 55.5, 29.7, 29.3, 22.9,

22.8 ppm. C₂₅H₂₂O₃(370.45): calcd. C 81.06, H 5.99; found C

81.35, H 5.78.

6-(4-Methoxyphenyl)-1,2,3,4-tetrahydrotetracene (23h): Reduction

of diketone 21h (0.85 g, 2.30 mmol) with sodium borohydride

(0.45 g, 11.84 mmol) followed by workup led to diol 22h. Crude

diol 22h (0.80 g, 2.15 mmol) upon annulation with HBr (33 %,

0.87 g, 10.75 mmol) in acetic acid by adopting a procedure similar

to that for 14a afforded compound 23h (0.65 g, 90%) as a pale

yellow solid, m.p. 186–188 °C. ¹H NMR (300 MHz, CDCl₃): δ =

8.31 (s, 1 H), 7.95 (d, J = 8.4 Hz, 1 H), 7.71 (s, 1 H), 7.63 (d, J =

8.7 Hz, 1 H), 7.38–7.23 (m, 5 H), 7.10 (d, J = 8.7 Hz, 2 H), 3.93

(s, 3 H), 3.01–2.97 (m, 2 H), 2.87–2.83 (m, 2 H), 1.84–1.82 (m, 4

H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 140.1, 136.5, 136.1,

9-(5,6,7,8-Tetrahydronaphthalen-1-yl)anthracene (23f): Reduction of

diketone 21f (0.35 g, 1.03 mmol) with sodium borohydride (0.19 g,

5.0 mmol) followed by workup led to diol 22f. Crude diol 22f

(0.36 g, 1.05 mmol) upon annulation with HBr (33 %, 0.42 g,

5.19 mmol) in acetic acid by adopting a procedure similar to that

for 14a afforded compound 23f (0.27 g, 83%) as a pale yellow solid,

m.p. 82–84 °C. ¹H NMR (300 MHz, CDCl₃): δ = 8.46 (s, 1 H), 8.03

(d, J = 8.4 Hz, 2 H), 7.75 (d, J = 8.7 Hz, 2 H), 7.48–7.45 (m, 1 H),

7.42 (s, 1 H), 7.39–7.37 (m, 1 H), 7.35–7.32 (m, 1 H), 7.31–7.26 (m,

1 H), 7.13 (s, 2 H), 2.94–2.90 (m, 2 H), 2.90–2.85 (m, 2 H), 1.92–

1.90 (m, 4 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 137.5, 135.1, 133.5, 132.4, 131.3, 131.1, 130.7, 130.2, 128.3, 126.8, 126.4,

137.1, 136.2, 135.7, 133.3, 131.8, 131.4, 130.3, 129.0, 128.4, 128.3,

128.2, 127.8, 127.6, 127.1, 126.2, 125.1, 124.6, 29.5, 29.3, 23.4,

23.3 ppm. HRMS (EI): calcd. for C₂₄H₂₀[M⁺] 308.1565; found

308.1560.

125.2, 124.9, 124.7, 124.5, 113.8, 55.4, 30.3, 29.9, 23.4 ppm. HRMS

(EI): calcd. for C₂₅H₂₂O [M⁺] 338.1671; found 338.1650.

[2-(1-Naphthoyl)phenyl](5,6,7,8-tetrahydronaphthalen-2-yl)meth-

anone (21i): Ring opening of 3-(5,6,7,8-tetrahydronaphthalen-2-

[2-(4-Methylbenzoyl)phenyl](5,6,7,8-tetrahydronaphthalen-2-yl)meth- yl)isobenzofuran-1(3H)-one (2.0 g, 7.58 mmol) with freshly pre-

anone (21g): Ring opening of 3-(5,6,7,8-tetrahydronaphthalen-2-

yl)isobenzofuran-1(3H)-one with freshly prepared p-tolylmagne-

sium bromide followed by acidic workup gave benzo[c]furan 20g as

a fluorescent bright yellow solid. Oxidation of benzo[c]furan 20g

(1.13 g, 2.70 mmol) with MnO₂(0.86 g, 9.89 mmol) by following a

procedure similar to that for 20a afforded diketone 21g (1.05 g,

89 %) as a yellow solid, m.p. 68–70 °C. ¹H NMR (300 MHz,

pared 1-naphthylmagnesium bromide followed by acidic workup

gave benzo[c]furan 20i as a fluorescent bright yellow solid. Oxid-

ation of benzo[c]furan 20i (1.95 g, 5.21 mmol) with MnO₂(1.35 g,

15.53 mmol) by following a procedure similar to that for 20a af-

forded diketone 21i (0.65 g, 90%) as a pale yellow solid, m.p. 186–

188 °C. ¹H NMR (300 MHz, CDCl₃): δ = 8.23 (d, J = 8.4 Hz, 1

H), 7.93 (d, J = 8.1 Hz, 1 H), 7.80 (d, J = 8.1 Hz, 1 H), 7.73 (d, J

CDCl₃): δ = 7.62–7.59 (m, 6 H), 7.41 (d, J = 6.3 Hz, 2 H), 7.17 (d, = 6.9 Hz, 1 H), 7.69–7.57 (m, 4 H), 7.50 (d, J = 7.2 Hz, 1 H), 7.46–

J = 8.1 Hz, 2 H), 7.04 (d, J = 8.1 Hz, 1 H), 2.77–2.70 (m, 4 H), 2.38

(s, 3 H), 1.78–1.76 (m, 4 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ

= 196.6, 196.3, 165.2, 143.8, 143.2, 140.4, 140.2, 137.3, 134.8, 134.7,

130.7, 130.1, 130.0, 129.6, 129.6, 129.5, 129.1, 129.0, 127.0, 29.7,

29.3, 22.9, 22.8, 21.7 ppm. C₂₅H₂₂O₂(354.45): calcd. C 84.72, H

6.26; found C 84.91, H 6.07.

7.43 (m, 1 H), 7.40–7.36 (m, 1 H), 7.19 (t, J = 8.1 Hz, 1 H), 6.88

(d, J = 8.1 Hz, 1 H), 2.66–2.55 (m, 4 H), 1.72–1.59 (m, 4 H) ppm.

¹³C NMR (75.4 MHz, CDCl₃): δ = 197.4, 196.9, 143.2, 141.2,

140.4, 137.3, 135.3, 135.1, 133.6, 132.9, 131.5, 130.8, 130.7, 130.6,

130.1, 130.0, 129.1, 129.0, 128.0, 127.3, 126.6, 126.4, 125.8, 124.0,

29.6, 29.1, 22.8, 22.7 ppm. C₂₈H₂₂O₂(390.48): calcd. C 86.13, H

5.68; found C 86.41, H 5.51.

6-p-Tolyl-1,2,3,4-tetrahydrotetracene (23g): Reduction of diketone

21g (0.74 g, 2.09 mmol) with sodium borohydride (0.40 g, Preparation of Compounds 23i and 23iЈ: Reduction of diketone 21i

10.58 mmol) followed by workup led to diol 22g. Crude diol 22g (0.75 g, 1.92 mmol) with sodium borohydride (0.36 g, 9.47 mmol)

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Eur. J. Org. Chem. 2015, 7816–7835

Anthracene, Tetracene, and Naphtho[b]thiophene Analogues

followed by workup led to diol 22i. Crude diol 22i (0.67 g,

1.71 mmol) upon annulation with HBr (33%, 0.69 g, 8.52 mmol) in

acetic acid by adopting a procedure similar to that for 14a fur-

nished an inseparable mixture of compounds 23i and 23iЈ (0.57 g,

94 %) as a colorless solid, m.p. 96–98 °C. ¹H NMR (300 MHz,

CDCl₃): δ = 9.22 (s, 1 H), 8.87 (d, J = 8.1 Hz, 1 H), 8.42 (s, 1 H),

8.14 (d, J = 8.4 Hz, 1 H), 8.04–7.97 (m, 3 H), 7.80–7.73 (m, 3 H),

7.69–7.64 (m, 2 H), 7.61–7.56 (m, 2 H), 7.52–7.41 (m, 4 H), 7.38–

7.33 (m, 1 H), 7.29–7.24 (m, 2 H), 7.17–7.09 (m, 6 H), 2.99–2.96

(m, 2 H), 2.94–2.93 (m, 2 H), 2.86–2.84 (m, 2 H), 2.70–2.67 (m, 2

H), 1.92–1.91 (m, 4 H), 1.82–1.75 (m, 4 H) ppm. ¹³C NMR

(75.4 MHz, CDCl₃): δ = 137.2, 136.3, 136.2, 133.6, 131.8, 131.1,

130.6, 129.1, 129.0, 128.6, 128.5, 128.4, 128.3, 128.2, 127.9, 127.1,

127.0, 126.9, 126.8, 126.7, 126.6, 126.4, 126.2, 126.0, 125.9, 125.7,

125.6, 125.5, 124.9, 124.8, 124.6, 123.1, 121.3, 30.1, 29.9, 29.5, 29.4,

23.4, 23.4, 23.3, 23.2 ppm. C₂₈H₂₂(358.48): calcd. C 93.81, H 6.19;

found C 93.96, H 6.04.

4-(Pyren-2-yl)naphtho[2,3-b]thiophene (27a): Reduction of crude di-

ketone 25a (0.32 g, 0.77 mmol) with sodium borohydride (0.15 g,

3.95 mmol) followed by workup gave diol 26a. Crude diol 26a

(0.31 g, 0.73 mmol) upon annulation with HBr (33 %, 0.30 g,

3.69 mmol) in acetic acid by adopting a procedure similar to that

for 14a afforded compound 27a (0.23 g, 83%) as a yellow solid,

1

m.p. 220–222 °C. H NMR (300 MHz, CDCl₃): δ = 8.58 (s, 1 H),

8.36 (d, J = 7.8 Hz, 1 H), 8.26 (d, J = 7.8 Hz, 1 H), 8.25 (s, 2 H),

8.18–8.13 (m, 1 H), 8.09–8.01 (m, 3 H), 7.81 (d, J = 9.3 Hz, 1 H),

7.54–7.49 (m, 3 H), 7.35 (d, J = 6.0 Hz, 1 H), 7.30–7.7.25 (m, 1

H), 6.78 (d, J = 6 Hz, 1 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ

= 139.3, 137.8, 133.9, 132.8, 131.5, 131.2, 131.1, 130.3, 130.2, 128.9,

128.1, 127.8, 127.7, 127.5, 126.8, 126.2, 125.7, 125.4, 125.3, 125.2,

125.0, 124.9, 124.7, 123.7, 121.0 ppm. HRMS (EI): calcd. for

C₂₈H₁₆S [M⁺] 384.0973; found 384.0970.

(2-Benzoylphenyl)(pyren-2-yl)methanone (25b): Ring opening of 3-

(pyren-2-yl)isobenzofuran-1(3H)-one (1.5 g, 4.49 mmol) with

freshly prepared phenylmagnesium bromide followed by acidic

workup gave benzo[c]furan 24b as a fluorescent bright yellow solid.

Oxidation of benzo[c]furan 24b (0.45 g, 1.15 mmol) with MnO₂

(0.30 g, 3.45 mmol) by following a procedure similar to that for 20a

afforded diketone 25b (0.42 g, 91%) as a yellow solid, m.p. 148–

150 °C. ¹H NMR (300 MHz, CDCl₃): δ = 8.56 (d, J = 9.3 Hz, 1

H), 8.23 (t, J = 6.0 Hz, 2 H), 8.06 (d, J = 9 Hz, 1 H), 8.09–8.02

(m, 5 H), 7.70–7.56 (m, 6 H), 7.48 (t, J = 7.42 Hz, 1 H), 7.27 (t, J

= 6.1 Hz, 2 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 198.0,

197.0, 141.2, 141.1, 137.3, 133.9, 133.0, 131.7, 131.3, 131.0, 130.6,

130.5, 130.0, 129.7, 129.5, 129.4, 129.1, 128.7, 128.3, 127.1, 126.4,

126.3, 126.2, 124.8, 124.7, 124.1, 123.5 ppm. C₃₀H₁₈O₂(410.47):

calcd. C 87.78, H 4.42; found C 87.59, H 4.61.

[2-(1-Naphthoyl)phenyl](biphenyl-4-yl)methanone (21j): Ring open-

ing of 3-(biphenyl-4-yl)isobenzofuran-1(3H)-one with freshly pre-

pared 1-naphthylmagnesium bromide followed by acidic workup

gave benzo[c]furan 20j as a fluorescent bright yellow solid. Oxid-

ation of benzo[c]furan 20j (07 g, 1.77 mmol) with MnO₂(0.46 g,

5.28 mmol) by following a procedure similar to that for 20a af-

forded diketone 21j (0.60 g, 82%) as a pale yellow solid, m.p. 70–

72 °C. ¹H NMR (300 MHz, CDCl₃): δ = 8.25 (d, J = 8.4 Hz, 1 H),

7.96–7.92 (m, 1 H), 7.81 (d, J = 8.1 Hz, 1 H), 7.74 (d, J = 7.8 Hz,

1 H), 7.68–7.66 (m, 1 H), 7.62 (d, J = 8.1 Hz, 3 H), 7.58–7.50

(m, 4 H), 7.47–7.42 (m, 5 H), 7.40–7.34 (m, 3 H) ppm. ¹³C NMR

(75.4 MHz, CDCl₃): δ = 197.5, 196.6, 145.8, 141.0, 140.5, 139.9,

136.2, 133.6, 131.6, 130.9, 130.7, 130.2, 130.0, 129.0, 128.9, 128.2,

128.1, 127.7, 127.6, 127.5, 127.3, 127.2, 127.0, 126.5, 125.6,

124.0 ppm. C₃₀H₂₀O₂(412.49): calcd. C 87.36, H 4.89; found C

87.58, H 5.08.

Annulation of Diol 26b: Reduction of diketone 25b (0.30 g,

0.71 mmol) with sodium borohydride (0.13 g, 3.42 mmol) followed

by workup gave diol 26b. The annulation of crude diol 26b (0.30 g,

0.72 mmol) with HBr (33%, 0.29 g, 3.63 mmol) in acetic acid by

adopting a procedure similar to that for 14a followed by column

chromatographic purification (silica gel; hexane/ethyl acetate, 99:1)

furnished products 27b and 27bЈ.

7-(Biphenyl-4-yl)tetraphene (23j): Reduction of diketone 21j (0.42 g,

1.02 mmol) with sodium borohydride (0.20 g, 5.26 mmol) followed

by workup led to diol 22j. Crude diol 22j (0.36 g, 0.87 mmol) upon

annulation with HBr (33%, 0.35 g, 4.32 mmol) in acetic acid by

adopting a procedure similar to that for 14a afforded compound

23j (0.29 g, 87%) as a pale yellow solid, m.p. 218–220 °C. ¹H NMR

(300 MHz, CDCl₃): δ = 9.28 (s, 1 H), 8.91 (d, J = 8.4 Hz, 1 H),

8.19 (d, J = 8.1 Hz, 1 H), 7.83 (m, 3 H), 7.79–7.74 (m, 1 H), 7.71–

7.60 (m, 3 H), 7.57–7.51 (m, 6 H), 7.48–7.42 (m, 2 H) ppm. ¹³C

NMR (75.4 MHz, CDCl₃): δ = 140.9, 140.3, 138.0, 137.2, 131.7,

131.6, 131.5, 131.0, 130.5, 128.9, 128.7, 128.6, 128.5, 127.5, 127.2,

127.1, 127.0, 126.7, 125.8, 125.6, 125.5, 123.1, 121.7 ppm. C₃₀H₂₀

(380.49): calcd. C 94.70, H 5.30; found C 94.86, H 5.17.

7-Phenylnaphtho[2,1,8-qra]tetracene (27b): Orange solid, 0.16 g

(61%), m.p. 244–246 °C. ¹H NMR (300 MHz, CDCl₃): δ = 9.64 (s,

1 H), 9.25 (d, J = 9.3 Hz, 1 H), 8.32 (t, J = 9.6 Hz, 2 H), 8.17 (s,

2 H), 7.93–7.85 (m, 2 H), 7.79 (d, J = 8.7 Hz, 1 H), 7.64–7.63

(m, 5 H), 7.61–7.56 (m, 3 H), 7.54–7.47 (m, 1 H) ppm. ¹³C NMR

(75.4 MHz, CDCl₃): δ = 139.0, 137.4, 131.7, 131.6, 128.9,

128.8,127.8, 127.6, 127.5, 126.6, 126.3, 125.8, 125.6, 125.2, 124.7,

123.8, 122.5, 121.9 ppm. DEPT-135 (75.4 MHz, CDCl₃): δ = 131.6,

128.9, 128.8, 127.8, 127.6, 127.5, 126.6, 126.3, 125.8, 125.6, 125.2,

124.7, 123.8, 122.5, 121.9 ppm (only fifteen signals appeared in-

stead of sixteen). HRMS (EI): calcd. for C₃₀H₁₈[M⁺] 378.1409;

found 378.1400.

Pyren-2-yl[2-(thiophen-2-ylcarbonyl)phenyl]methanone (25a): Ring

opening of 3-(pyren-2-yl)isobenzofuran-1(3H)-one (2.0 g,

5.99 mmol) with freshly prepared 2-thienylmagnesium bromide fol-

lowed by acidic workup gave benzo[c]furan 24a as a fluorescent

bright yellow solid. Oxidation of benzo[c]furan 24a (0.51 g,

1.28 mmol) with MnO₂(0.33 g, 3.79 mmol) by following a pro-

cedure similar to that for 20a afforded diketone 25a (0.46 g, 88%)

2-(Anthracen-9-yl)pyrene (27bЈ): Pale yellow solid, 0.08 g (30%),

1

m.p. 228–230 °C. H NMR (300 MHz, CDCl₃): δ = 8.63 (s, 1 H),

8.36 (d, J = 7.5 Hz, 1 H), 8.25–8.19 (m, 3 H), 8.11 (t, J = 7.7 Hz,

3 H), 8.03–7.97 (m, 2 H), 7.77 (d, J = 9.3 Hz, 1 H), 7.45 (t, J =

7.4 Hz, 2 H), 7.36–7.30 (m, 3 H), 7.26–7.17 (m, 2 H) ppm. ¹³C

NMR (75.4 MHz, CDCl₃): δ = 135.6, 133.9, 131.5, 131.3, 131.1,

130.8, 129.4, 128.5, 127.8, 127.7, 127, 127.0, 126.1, 125.7, 125.6,

125.3, 125.2, 124.7 ppm. DEPT-135 (75.4 MHz, CDCl₃): δ = 129.4,

128.5, 127.8, 127.7, 127.5, 127.0, 126.1, 125.6, 125.3, 124.7 ppm.

HRMS (EI): calcd. for C₃₀H₁₈[M⁺] 378.1409; found 378.1404.

1

as a yellow solid, m.p. 138–140 °C. H NMR (300 MHz, CDCl₃):

δ = 8.54 (d, J = 9.3 Hz, 1 H), 8.14–8.12 (m, 2 H), 8.04 (t, J =

9.2 Hz, 2 H), 7.97–7.91 (m, 4 H), 7.64–7.58 (m, 3 H), 7.53–7.50

(m, 1 H), 7.38–7.35 (m, 2 H), 6.92–6.89 (m,1 H) ppm. ¹³C NMR

(75.4 MHz, CDCl₃): δ = 198.0, 188.7, 144.4, 140.9, 140.7, 134.8,

134.6, 134.0, 131.7, 131.3, 131.1, 130.9, 130.6, 130.5, 130.3, 129.7,

129.4, 128.9, 128.6, 127.9, 127.2, 126.4, 126.3, 126.2, 124.7, 124.6,

124.1, 123.5 ppm. C₂₈H₁₆O₂S (416.49): calcd. C 80.75, H 3.87, S

7.70; found C 80.69, H 3.73, S 7.95.

[2-(4-Methylbenzoyl)phenyl](pyren-2-yl)methanone (25c): Ring

opening of 3-(pyren-2-yl)isobenzofuran-1(3H)-one (1.0 g,

2.99 mmol) with freshly prepared p-tolylmagnesium bromide fol-

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A. K. Mohanakrishnan et al.

FULL PAPER

lowed by acidic workup gave benzo[c]furan 24c as a fluorescent

bright yellow solid. Oxidation of benzo[c]furan 24c (0.74 g,

1.81 mmol) with MnO₂(0.57 g, 5.41 mmol) by following a pro-

cedure similar to that for 20a afforded diketone 25c (0.72 g, 94%)

for 14a furnished 27d 0.67 g (92%) as an orange solid, m.p. 120–

122 °C. H NMR (300 MHz, CDCl₃): δ = 9.54 (s, 1 H), 9.16 (d, J

= 9.0 Hz, 1 H), 8.23 (t, J = 10.2 Hz, 2 H), 8.14 (s, 1 H), 8.08 (d, J

= 7.2 Hz, 1 H), 7.85–7.75 (m, 3 H), 7.59 (s, 2 H), 7.50 (t, J =

6.9 Hz, 1 H), 7.39 (t, J = 8.1 Hz, 3 H), 7.13 (t, J = 9.9 Hz, 2 H),

1

as a yellow solid, m.p. 136–138 °C. H NMR (300 MHz, CDCl₃):

δ = 8.54 (d, J = 9.3 Hz, 1 H), 8.22–8.11 (m, 3 H), 8.06–8.0 (m, 5 3.92 (s, 3 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 158.1, 136.3,

H), 7.68 (t, J = 7.1 Hz, 2 H), 7.64–7.57 (m, 2 H), 7.48 (d, J =

131.6, 130.8, 130.7, 130.2, 129.9, 129.3, 128.8, 127.8, 127.7, 126.6,

126.4, 125.8, 125.6, 125.2, 124.7, 124.4, 124.1, 123.6, 122.9, 122.6,

8.1 Hz, 2 H), 6.99 (d, J = 8.1 Hz, 2 H), 2.26 (s, 3 H) ppm. ¹³C

NMR (75.4 MHz, CDCl₃): δ = 198.0, 196.7, 143.9, 141.4, 141.0, 121.4, 120.7, 112.9, 54.4 ppm. HRMS (EI): calcd. for C₃₁H₂₀

O

134.9, 133.9, 131.9, 131.3, 131.0, 130.9, 130.6, 130.4, 130.0, 129.6,

129.5, 129.1, 129.0, 128.7, 127.2, 126.4, 126.2, 126.1, 124.8, 124.7,

124.1, 123.5, 21.6 ppm. C₃₁H₂₀O₂(424.50): calcd. C 87.71, H 4.75;

found C 87.82, H 4.69.

[M⁺] 408.1514; found 408.1510.

[2-(1-Naphthoyl)phenyl](pyren-2-yl)methanone (25e): Ring opening

of 3-(pyren-2-yl)isobenzofuran-1(3H)-one (1.5 g, 5.99 mmol) with

freshly prepared 1-naphthylmagnesium bromide followed by acidic

workup gave benzo[c]furan 24e as a fluorescent bright yellow solid.

Oxidation of benzo[c]furan 24e (0.45 g, 1.01 mmol) with MnO₂

(0.26 g, 2.99 mmol) by following a procedure similar to that for 20a

afforded diketone 25e (0.41 g, 90%) as a pale yellow solid, m.p.

163–165 °C. ¹H NMR (300 MHz, CDCl₃): δ = 8.30 (d, J = 9.3 Hz,

1 H), 8.16 (d, J = 7.5 Hz, 1 H), 8.11–8.06 (m, 2 H), 8.03–7.94 (m,

3 H), 7.88 (d, J = 7.8 Hz, 1 H), 7.83–7.64 (m, 7 H), 7.47 (d, J =

6.9 Hz, 1 H), 7.33 (t, J = 8.6 Hz, 2 H), 6.72 (t, J = 7.4 Hz, 1 H),

6.63 (t, J = 7.5 Hz, 1 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ =

197.8, 197.7, 141.8, 141.7, 135.4, 134.2, 133.6, 133.3, 131.7, 131.2,

131.1, 130.8, 130.5, 130.4, 130.3, 130.2, 129.8, 129.6, 129.2, 127.5,

127.0, 126.8, 126.2, 126.1, 126.0, 125.7, 125.0, 124.8, 124.2, 123.9,

123.7, 123.4 ppm. C₃₄H₂₀O₂(460.53): calcd. C 88.67, H 4.38; found

C 88.56, H 4.52.

Annulation of Diol 26c: Reduction of diketone 25c (0.65 g,

1.51 mmol) with sodium borohydride (0.29 g, 7.66 mmol) followed

by workup led to diol 26c. The annulation of crude diol 26c (0.69 g,

1.60 mmol) with HBr (33%, 0.65 g, 24.22 mmol) in acetic acid by

adopting a procedure similar to that for 14a followed by column

chromatographic purification (silica gel; hexane/ethyl acetate, 99:1)

afforded annulated compounds 27c and 27cЈ.

7-p-Tolylnaphtho[2,1,8-qra]tetracene (27c): Orange solid, 0.51 g

(80%), m.p. 180–190 °C. ¹H NMR (300 MHz, CDCl₃): δ = 9.61 (s,

1 H), 9.21 (d, J = 9.3 Hz, 1 H), 8.29 (t, J = 9.0 Hz, 2 H), 8.20 (s,

1 H), 8.16–8.13 (m, 1 H), 7.91–7.81 (m, 3 H), 7.65 (s, 1 H), 7.57 (t,

J = 7.3 Hz, 1 H), 7.48–7.41 (m, 5 H), 2.59 (s, 3 H) ppm. ¹³C NMR

(75.4 MHz, CDCl₃): δ = 137.7, 137.2, 136.1, 131.9, 131.8, 131.5,

131.0, 130.2, 129.9, 129.2, 128.9, 128.8, 128.7, 127.7, 127.6, 127.5,

126.9, 126.8, 126.3, 125.8, 125.5, 125.2, 124.6, 124.0, 123.8, 122.5,

121.8, 21.5 ppm. HRMS (EI): calcd. for C₃₁H₂₀[M⁺] 392.1565;

found 392.1560.

7-(Naphthalen-1-yl)naphtho[2,1,8-qra]tetracene (27e): Reduction of

diketone 25e (0.34 g, 0.76 mmol) with sodium borohydride (0.14 g,

3.68 mmol) followed by workup gave diol 26e. Crude diol 26e

(0.31 g, 0.73 mmol) upon annulation with HBr (33 %, 0.29 g,

3.58 mmol) by adopting a procedure similar to that for 14a af-

forded compound 27e (0.28 g, 92%) as a yellow solid, m.p. 202–

2-(2-Methylanthracen-9-yl)pyrene (27cЈ): Yellow solid, 0.07 g

(11%), m.p. 178–180 °C. ¹H NMR (300 MHz, CDCl₃): δ = 8.50 (s,

1 H), 8.29 (d, J = 7.8 Hz, 1 H), 8.17–8.11 (m, 3 H), 8.02 (d, J =

6.0 Hz, 2 H), 7.96–7.89 (m, 3 H), 7.69 (d, J = 9.3 Hz, 1 H), 7.37–

7.33 (m, 1 H), 7.31–7.21 (m, 3 H), 7.09 (d, J = 6.9 Hz, 1 H), 7.06

(s, 1 H), 2.13 (s, 3 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ =

135.4, 134.3, 134.2, 131.6, 131.5, 131.2, 131.1, 131.0, 130.8, 130.2,

129.5, 128.5, 128.4, 128.2, 127.7, 127.6, 127.5, 126.9, 126.8, 126.1,

125.9, 125.5, 125.2, 125.1, 125.1, 125.0, 124.9, 124.8, 124.7,

22.1 ppm. HRMS (EI): calcd. for C₃₁H₂₀[M⁺] 392.1565; found

392.1560.

1

204 °C. H NMR (300 MHz, CDCl₃): δ = 9.40 (s, 1 H), 8.97 (d, J

= 8.1 Hz, 1 H), 8.38 (d, J = 7.8 Hz, 1 H), 8.26–8.17 (m, 4 H), 8.10

(d, J = 7.5 Hz, 1 H), 8.06–7.98 (m, 2 H), 7.80–7.70 (m, 3 H), 7.62

(d, J = 7.2 Hz, 1 H), 7.56–7.52 (m, 1 H), 7.35 (d, J = 9.3 Hz, 3

H), 7.30–7.23 (m, 1 H), 7.17 (d, J = 9.3 Hz, 1 H) ppm. ¹³C NMR

(75.4 MHz, CDCl₃): δ = 135.8, 134.1, 131.9, 131.7, 131.5, 131.1,

130.8, 130.6, 129.9, 129.4, 128.7, 128.6, 128.3, 127.8, 127.7, 127.5,

127.3, 127.1, 126.9, 126.2, 126.0, 125.7, 125.6, 125.3, 125.2, 125.0,

124.8, 124.7, 123.2, 122.1 ppm. HRMS (EI): calcd. for C₃₄H₂₀O

[M⁺] 428.1565; found 428.1560.

[2-(4-Methoxybenzoyl)phenyl](pyren-2-yl)methanone (25d): Ring

opening of 3-(pyren-2-yl)isobenzofuran-1(3H)-one (2.0 g,

5.99 mmol) with freshly prepared p-anisylmagnesium bromide fol-

lowed by acidic workup gave benzo[c]furan 24d as a fluorescent

bright yellow solid. Oxidation of benzo[c]furan 24d (0.7 g,

1.65 mmol) with MnO₂(0.43 g, 4.95 mmol) by following a pro-

cedure similar to that for 20a afforded diketone 25d (0.67 g, 92%)

9,9-Dihexyl-9H-fluoren-3-yl[2-(2-thienyl)phenyl]methanone (29a):

Ring opening of 3-(9,9-dihexyl-9H-fluoren-2-yl)isobenzofuran-

1(3H)-one^[33]with freshly prepared 2-thienylmagnesium bromide

followed by acidic workup gave benzo[c]furan 28a as a fluorescent

bright yellow solid. Oxidation of benzo[c]furan 28a (0.6 g,

1.15 mmol) with MnO₂(0.3 g, 3.46 mmol) by following a procedure

similar to that for 20a afforded diketone 29a (0.53 g, 86%) as a

thick yellow liquid. ¹H NMR (300 MHz, CDCl₃): δ = 7.66–7.51

(m, 9 H, ArH), 7.38 (dd, J₁= 1.2, J₂= 3.9 Hz, 1 H, ArH), 7.28–

7.26 (broad s, 3 H, ArH), 6.98–6.95 (m, 1 H, ArH), 1.88–1.83 (m,

4 H, CH₂), 1.05–0.95 (m, 12 H, CH₂), 0.71–0.47 (m, 10 H,

CH₂CH₃) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 196.5, 188.4,

152.1, 150.8, 146.1, 144.3, 139.7, 139.81, 139.6, 135.8, 135.1, 134.7,

130.5, 130.4, 130.0, 129.9, 129.0, 128.5, 127.9, 127.0, 123.9, 123.1,

1

as a yellow solid, m.p. 120–122 °C. H NMR (300 MHz, CDCl₃):

δ = 8.54 (d, J = 9.3 Hz, 1 H), 8.20–8.16 (m, 2 H), 8.12 (d, J =

9.0 Hz, 1 H), 8.04–7.98 (m, 5 H), 7.71 (d, J = 7.5 Hz, 1 H), 7.63

(d, J = 6.3 Hz, 1 H), 7.51 (d, J = 8.7 Hz, 2 H), 6.63 (d, J = 8.7 Hz,

2 H), 3.68 (s, 3 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 198.1,

195.6, 163.4, 141.4, 140.9, 133.9, 131.9, 131.8, 131.3, 131.0, 130.8,

129.9, 129.6, 129.3, 129.2, 128.9, 128.8, 127.2, 126.4, 126.3, 126.1,

124.8, 124.6, 124.1, 123.6, 114.5, 113.6, 109.8, 55.4 ppm. C₃₁H₂₀O₃

(440.50): calcd. C 84.53, H 4.58; found C 84.71, H 4.39.

7-(4-Methoxyphenyl)naphtho[2,1,8-qra]tetracene (27d): Reduction 120.8, 119.2, 55.2, 40.1, 31.5, 29.6, 23.7, 22.6, 14.0 ppm. DEPT-135

of diketone 25d (0.37 g, 0.84 mmol) with sodium borohydride

(0.16 g, 4.21 mmol) followed by workup led to diol 26d. Crude diol

26d (0.42 g, 0.95 mmol) upon annulation with HBr (33%, 0.38 g,

14.34 mmol) in acetic acid by following a procedure similar to that

(75.4 MHz, CDCl₃): δ = 135.1, 134.7, 130.6, 130.5, 130.0, 129.9,

129.0, 128.5, 127.9, 127.0, 123.9, 123.1, 120.8, 119.2, 40.1, 31.5,

29.6, 23.7, 22.6, 14.0 ppm. C₃₇H₄₀O₂S (548.78): calcd. C 80.98, H

7.35, S 5.84; found C 81.26, H 7.48, S 5.71.

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Eur. J. Org. Chem. 2015, 7816–7835

Anthracene, Tetracene, and Naphtho[b]thiophene Analogues

4-(9,9-Dihexyl-9H-fluoren-2-yl)naphtho[2,3-b]thiophene (31a): Re-

duction of diketone 29a (0.42 g, 0.76 mmol) with sodium boro-

hydride (0.12 g, 3.1 mmol) followed by workup led to diol 30a.

Crude diol 30a (0.43 g, 0.77 mmol) upon annulation with HBr

(33%, 0.38 g, 14.34 mmol) in acetic acid by following a procedure

similar to that for 14a afforded compound 31a (0.35 g, 89%) as a

green solid, m.p. 154–156 °C. ¹H NMR (300 MHz, CDCl₃): δ =

8.42 (s, 1 H), 7.97 (d, J = 8.4 Hz, 1 H), 7.87 (d, J = 8.1 Hz, 2 H),

7.79 (d, J = 7.5 Hz, 1 H), 7.51–7.44 (m, 3 H), 7.42–7.34 (m, 5 H),

7.16 (d, J = 5.4 Hz, 1 H), 1.99 (t, J = 7.8 Hz, 4 H, CH₂), 1.14–1.08

(m, 12 H, CH₂), 0.79–0.74 (m, 10 H, CH₂CH₃) ppm. ¹³C NMR

(75.4 MHz, CDCl₃): δ = 151.0, 150.9, 140.9, 140.6, 138.1, 137.8,

137.4, 135.1, 131.3, 129.3, 127.6, 127.5, 127.2, 126.9, 126.5, 125.5,

125.1, 124.9, 123.7, 122.9, 120.4, 119.8, 119.6, 55.3, 40.4, 31.5, 29.7,

23.9, 22.5, 14.1 ppm. DEPT-135 (75.4 MHz, CDCl₃): δ = 129.3,

127.6 127.5, 127.2, 126.9, 126.5, 125.5, 125.1, 124.9, 123.7, 122.9,

120.4, 119.8, 119.6, 40.4, 31.5, 29.7, 23.9, 22.5, 14.1 ppm. C₃₇H₄₀S

(516.78): calcd. C 85.99, H 7.80, S 6.20; found C 85.86, H 7.71, S

6.31.

1.82 (m, 4 H), 1.04–0.95 (m, 12 H), 0.70–0.44 (m, 10 H) ppm. ¹³C

NMR (75.4 MHz, CDCl₃): δ = 196.5, 196.3, 152.1, 150.8, 146.0,

143.8, 140.4, 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 ppm. DEPT-135 (75.4 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 ppm. C₄₀H₄₄O₂

(556.79): calcd. C 86.29, H 7.97; found C 86.35, H 7.88.

9-(9,9-Dihexyl-9H-fluoren-2-yl)-2-methylanthracene (31c): Re-

duction of diketone 29c (0.75 g, 1.94 mmol) with sodium boro-

hydride (0.29 g, 7.77 mmol) followed by workup led to diol 30c.

Crude diol 30c (0.63 g, 1.12) upon annulation with HBr (33 %,

0.45 g, 5.62 mmol) in acetic acid by adopting a procedure similar

to that for 14a afforded anthracene 31c (0.46 g, 73%) as a thick

1

liquid. H NMR (300 MHz, CDCl₃): δ = 8.53 (s, 1 H), 8.10 (d, J

= 8.4 Hz, 1 H), 8.05–7.98 (m, 2 H), 7.90 (d, J = 6.6 Hz, 1 H), 7.82

(d, J = 8.7 Hz, 1 H), 7.58 (s, 1 H), 7.54–7.43 (m, 6 H), 7.48–7.38

(m, 2 H), 2.47 (s, 3 H), 2.12–2.04 (m, 3 H), 1.25–1.17 (m, 11 H),

0.88–0.82 (m, 10 H) ppm. ¹³C NMR (75.4 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 ppm. HRMS

(EI): calcd. for C₄₀H₄₄[M⁺] 524.3443; found 524.3439.

(9,9-Dihexyl-9H-fluoren-3-yl)[2-(benzoyl)phenyl]methanone (29b):

Ring opening of 3-(9,9-dihexyl-9H-fluoren-2-yl)isobenzofuran-

1(3H)-one^[33]with freshly prepared phenylmagnesium bromide fol-

lowed by acidic workup gave benzo[c]furan 28b as a thick orange

liquid. Oxidation of benzo[c]furan 28b (0.9 g, 1.71 mmol) with

MnO₂(0.44 g, 5.13 mmol) by following a procedure similar to that

for 20a afforded diketone 29b (0.79 g, 85%) as a thick orange li-

(9,9-Dihexyl-9H-fluoren-3-yl)[2-(4-benzoyl)4-methoxyphenyl]meth-

anone (29d): Ring opening of 3-(9,9-dihexyl-9H-fluoren-2-yl)iso-

benzofuran-1(3H)-one^[33](2.0 g, 4.29 mmol) with freshly prepared

p-anisylmagnesium bromide followed by acidic workup gave

benzo[c]furan 28d as a fluorescent yellow solid. Oxidative cleavage

of benzo[c]furan 28d (1 g, 1.78 mmol) with MnO₂(0.46 g,

5.35 mmol) by adopting a procedure similar to that for 20a fur-

nished diketone 29d as a thick liquid (0.85 g, 83%). The crude di-

ketone was used in the next step without further characterization.

1

quid. H NMR (300 MHz, CDCl₃): δ = 7.65–7.62 (m, 3 H), 7.58–

7.55 (m, 3 H), 7.39–7.32 (m, 2 H), 7.26–7.10 (m, 6 H), 1.87–1.82

(m, 4 H, CH₂), 1.04–0.99 (m, 12 H, CH₂), 0.70–0.44 (m, 10 H,

CH₂CH₃) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 196.8, 196.5,

152.1, 150.9, 146.1, 140.3, 140.2, 139.7, 137.3, 135.7, 132.9, 130.4,

130.2, 130.1, 129.9, 129.8, 129.5, 128.8, 128.5, 128.3, 127.2, 127.0,

124.0, 123.1, 120.8, 119.2, 55.3, 40.1, 31.5, 29.7, 23.8, 22.6,

14.0 ppm. DEPT-135 (75.4 MHz, CDCl₃): δ = 133.0, 130.4, 130.2,

130.1, 129.9, 129.8, 129.5, 128.5, 128.3, 127.0, 124.0, 123.1, 120.8,

119.2, 40.1, 31.5, 29.7, 23.8, 22.6, 14.0 ppm. C₄₀H₄₄O₂(556.79):

calcd. C 86.29, H 7.97; found C 86.35, H 7.88.

9-(9,9-Dihexyl-9H-fluoren-2-yl)-2-methoxyanthracene (31d): Re-

duction of crude diketone 29d (0.62 g, 1.08 mmol) with sodium

borohydride (0.20 g, 5.41 mmol) followed by workup gave diol 30d.

Crude diol 30d (0.59 g, 1.02 mmol) upon annulation with HBr

(33%, 0.41 g, 5.12 mmol) in acetic acid by adopting a procedure

similar to that for 14a furnished compound 31d (0.39 g, 71%) as a

9-(9,9-Dihexyl-9H-fluoren-2-yl)anthracene (31b): Reduction of di-

ketone 29b (0.6 g, 1.1 mmol) with sodium borohydride (0.17 g,

4.45 mmol) followed by workup led to diol 30b. Crude diol 30b

(0.61 g, 1.1 mmol) upon annulation with HBr (33 %, 0.45 g,

5.55 mmol) in acetic acid by following a procedure similar to that

for 14a afforded compound 31b (0.47 g, 83%) as a green solid, m.p.

1

thick liquid. H NMR (300 MHz, CDCl₃): δ = 8.44 (s, 1 H), 7.98

(d, J = 8.1 Hz, 1 H), 7.91–7.86 (m, 2 H), 7.65 (d, J = 7.5 Hz, 2 H),

7.39 (d, J = 7.8 Hz, 2 H), 7.30–7.28 (m, 4 H), 7.12 (d, J = 7.5 Hz,

2 H), 3.97 (s, 3 H), 2.07–1.89 (m, 4 H), 1.26–1.22 (m, 4 H), 1.04–

1.00 (m, 12 H), 0.72–0.67 (m, 6 H) ppm. ¹³C NMR (75.4 MHz,

CDCl₃): δ = 159.0, 151.1, 148.4, 140.3, 140.2, 139.8, 132.5, 131.7,

131.3, 131.2, 128.2, 128.1, 127.0, 126.9, 126.8, 126.7, 126.2, 125.0,

124.8, 123.1, 122.9, 121.1, 120.7, 119.6, 113.9, 55.4, 54.4, 41.7, 31.5,

29.8, 24.0, 22.6, 14.0 ppm. HRMS (EI): calcd. for C₄₀H₄₄O [M⁺]

540.3392; found 540.3390.

1

150–152 °C. H NMR (300 MHz, CDCl₃): δ = 8.53 (s, 1 H), 8.08

(d, J = 8.4 Hz, 2 H), 7.93 (d, J = 7.5 Hz, 1 H), 7.83 (d, J = 7.2 Hz,

1 H), 7.78 (d, J = 8.7 Hz, 2 H), 7.51–7.33 (m, 9 H), 1.99 (t, J =

7.8 Hz, 4 H, CH₂), 1.14–1.08 (m, 12 H, CH₂), 0.79–0.74 (m, 10 H,

CH₂& CH₃) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 151.0, 150.9,

141.0, 140.5, 137.7, 137.4, 131.5, 130.4, 129.8, 128.4, 127.2, 126.9,

126.9, 126.5, 126.0, 125.3, 125.1, 122.9, 119.8, 119.6, 55.3, 40.5,

31.6, 29.7, 23.9, 22.5, 14.1 ppm. DEPT-135 (75.4 MHz, CDCl₃): δ

= 129.8, 128.4, 127.2, 126.9, 126.5, 126.0, 125.3, 125.1, 122.9, 119.8,

119.6, 40.5, 31.6, 29.7, 23.9, 22.5, 14.1 ppm.

[2-(Dibenzo[b,d]furan-2-carbonyl)phenyl](thiophen-2-yl)methanone

(29e): Ring opening of 3-(dibenzo[b,d]furan-2-yl)isobenzofuran-

1(3H)-one^[34]with freshly prepared 2-thienylmagnesium bromide

followed by acidic workup gave benzo[c]furan 28e as an orange

solid. Oxidation of the benzo[c]furan 28e (0.72 g, 1.96 mmol) with

MnO₂(0.51 g, 5.9 mmol) by following a procedure similar to that

for 20a afforded diketone 29e (0.66 g, 89%) as a thick red liquid.

The crude diketone was used in the next step without further char-

acterization.

(9,9-Dihexyl-9H-fluoren-3-yl)[2-(4-methylbenzoyl)phenyl]methanone

(29c): Ring opening of 3-(9,9-dihexyl-9H-fluoren-2-yl)isobenzo-

furan-1(3H)-one^[33]with freshly prepared p-tolylmagnesium brom-

ide followed by acidic workup gave benzo[c]furan 28c as a thick

orange liquid. Oxidation of benzo[c]furan 28c (1.1 g, 2.03 mmol)

with MnO₂(3.51 g, 7.91 mmol) by following a procedure similar to

that for 20a afforded diketone 29c (0.92 g, 82%) as a thick orange

liquid. ¹H NMR (300 MHz, CDCl₃): δ = 7.64–7.53 (m, 10 H),

7.28–7.25 (m, 3 H), 7.06 (d, J = 7.5 Hz, 2 H), 2.27 (s, 3 H), 1.87–

7-(Thiophen-2-yl)anthra[2,3-d]benzo[b]furan (31e): Reduction of di-

ketone 29e (0.55 g, 1.44 mmol) with sodium borohydride (0.27 g,

7.2 mmol) followed by workup led to diol 30e. Crude diol 30e

(0.54 g, 1.41) upon annulation with HBr (33%, 0.54 g, 6.62 mmol)

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A. K. Mohanakrishnan et al.

FULL PAPER

1

in acetic acid by adopting a procedure similar to that for 14a af-

forded compound 31e (0.42 g, 83%) as a yellow solid, m.p. 222–

202 °C. H NMR (300 MHz, CDCl₃): δ = 8.64 (s, 1 H), 8.54 (s, 1

H), 8.05 (d, J = 7.5 Hz, 2 H), 7.72 (d, J = 8.1 Hz, 2 H), 7.52–7.46

(m, 3 H), 7.40–7.31 (m, 4 H), 7.14 (d, J = 8.7 Hz, 2 H), 3.95 (s, 3

1

224 °C. H NMR (300 MHz, CDCl₃): δ = 8.69 (s, 1 H), 8.54 (s, 1

H), 8.05 (t, J = 6.9 Hz, 2 H), 7.85 (s, 2 H), 7.63 (d, J = 5.1 Hz, 1 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 159.1, 158.2, 154.8,

H), 7.49–7.48 (m, 2 H), 7.47–7.40 (m, 2 H), 7.37–7.32 (m, 2 H) 136.2, 132.4, 131.1, 130.6, 130.4, 128.9, 128.3, 126.9, 126.6, 126.1,

7.23–7.22 (m, 1 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 150.8, 125.4, 124.6, 123.7, 122.8, 121.6, 119.2, 114.1, 111.4, 104.8,

155.2, 139.2, 131.9, 131.8, 130.2, 129.4, 129.0, 128.7, 128.5, 128.3,

128.0, 127.3, 126.8, 126.3, 126.0, 124.7, 123.6, 122.8, 121.6, 119.2,

111.5, 104.7 ppm. DEPT-135 (75.4 MHz, CDCl₃): δ = 129.4, 129.0,

128.5, 128.3, 127.3, 126.8, 126.3, 126.0, 124.7, 122.8, 121.6, 119.2,

111.5, 104.7 ppm. HRMS (EI): m/z. calcd. for C₂₄H₁₄OS [M⁺]

350.0765; found 350.0760.

55.4 ppm. C₂₇H₁₈O₂(374.44): calcd. C 86.61, H 4.85; found C

86.77, H 4.64.

[2-(1-Naphthoyl)phenyl](dibenzo[b,d]furan-2-yl)methanone (29h):

Ring opening of 3-(dibenzo[b,d]furan-2-yl)isobenzofuran-1(3H)-

one^[34](2 g, 6.67 mmol) with freshly prepared 1-naphthylmagne-

sium bromide followed by acidic workup gave benzo[c]furan 28h as

a fluorescent bright yellow solid. Oxidation of benzo[c]furan 28h

(1.0 g, 2.33 mmol) with MnO₂(0.6 g, 6.9 mmol) by following a pro-

[2-(Dibenzo[b,d]furan-2-carbonyl)phenyl](p-tolyl)methanone (29f):

Ring opening of 3-(dibenzo[b,d]furan-2-yl)isobenzofuran-1(3H)-

one^[34](2 g, 6.67 mmol) with freshly prepared p-tolylmagnesium cedure similar to that for 20a afforded diketone 29h (0.90 g, 88%)

1

bromide followed by acidic workup gave benzo[c]furan 28f as a

fluorescent bright yellow solid. Oxidation of benzo[c]furan 28f

(1.84 g, 4.92 mmol) with MnO₂(1.28 g, 14.75 mmol) by following

a procedure similar to that for 20a afforded diketone 29f (1.72 g,

89%) as a colorless solid, m.p. 156–158 °C. ¹H NMR (300 MHz,

CDCl₃): δ = 8.34 (s, 1 H), 7.92–7.84 (m, 2 H), 7.65–7.59 (m, 6 H),

as a thick yellow liquid. H NMR (300 MHz, CDCl₃): δ = 8.30 (d,

J = 9.3 Hz, 1 H), 8.16 (d, J = 7.5 Hz, 1 H), 8.11–8.06 (m, 2 H),

8.03–7.94 (m, 3 H), 7.88 (d, J = 7.8 Hz, 1 H), 7.83–7.64 (m, 7 H),

7.47 (d, J = 6.9 Hz, 1 H), 7.33 (t, J = 8.6 Hz, 2 H), 6.72 (t, J =

7.4 Hz, 1 H), 6.63 (t, J = 7.5 Hz, 1 H) ppm. ¹³C NMR (75.4 MHz,

CDCl₃): δ = 197.8, 197.7, 141.8, 135.4, 134.2, 133.6, 133.3, 131.2,

7.56–7.46 (m, 3 H), 7.38–7.33 (m, 1 H), 7.16 (d, J = 7.8 Hz, 2 H), 131.1, 130.8, 130.5, 130.4, 130.3, 130.2, 129.8, 129.6, 129.2, 127.5,

2.35 (s, 3 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 196.3, 196.1,

158.9, 156.9, 144.0, 140.4, 140.2, 134.7, 132.6, 130.3, 130.2, 130.1,

129.7, 129.6, 129.1, 127.9, 124.5, 123.7, 123.3, 123.2, 121.1, 111.9,

111.5, 21.7 ppm. C₂₇H₁₈O₃(390.44): calcd. C 83.06, H 4.65; found

C 83.21, H 4.49.

127.0, 126.8, 126.2, 126.1, 126.0, 125.7, 125.0, 124.8, 124.2, 123.9,

123.7, 123.4 ppm. C₃₀H₁₈O₃(426.47): calcd. C 84.49, H 4.25; found

C 84.38, H 4.16.

7-(Naphthalen-1-yl)anthra[2,3-d]benzo[b]furan (31h): Reduction of

diketone 29h (0.9 g, 2.11 mmol) with sodium borohydride (0.40 g,

10.56 mmol) followed by workup led to diol 30h. Crude diol 30h

(0.6 g, 1.39 mmol) upon annulation with HBr (33 %, 0.11 g,

1.35 mmol) in acetic acid by adopting a procedure similar to that

for 14a afforded compound 31h (0.44 g, 81%) as a yellow solid,

7-p-Tolylanthra[2,3-b]benzo[d]furan (31f): Reduction of diketone 29f

(0.77 g, 1.97 mmol) with sodium borohydride (0.38 g, 7.77 mmol)

followed by workup led to diol 30f. Crude diol 30f (0.51 g,

1.29 mmol) upon annulation with HBr (33%, 0.52 g, 6.43 mmol) in

acetic acid by adopting a procedure similar to that for 14a afforded

compound 31f (0.38 g, 82%) as a yellow solid, m.p. 212–214 °C.

¹H NMR (300 MHz, CDCl₃): δ = 8.64 (s, 1 H), 8.54 (s, 1 H), 8.05

1

m.p. 198–200 °C. H NMR (300 MHz, CDCl₃): δ = 9.28 (s, 1 H),

8.90 (d, J = 7.8 Hz, 1 H), 8.18 (d, J = 8.1 Hz, 1 H), 8.01 (s, 1 H),

7.90 (d, J = 7.5 Hz, 1 H), 7.78 (t, J = 6.3 Hz, 2 H), 7.69 (d, J =

(d, J = 7.5 Hz, 2 H), 7.72–7.69 (m, 2 H), 7.46–7.40 (m, 5 H), 7.36– 7.8 Hz, 3 H), 7.67–7.63 (m, 6 H), 7.60–7.45 (m, 1 H), 7.43–7.31 (m,

7.31 (m, 4 H), 2.54 (s, 3 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ

= 158.2, 154.8, 137.2, 136.5, 136.0, 131.2, 130.4, 130.2, 129.3, 128.9,

128.3, 126.9, 126.6, 126.1, 125.3, 124.6, 123.7, 122.8, 121.6, 119.2,

111.4, 104.9, 21.4 ppm. C₂₇H₁₈O (358.44): calcd. C 90.47, H 5.06;

found C 90.61, H 4.97.

1 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 156.8, 155.7, 137.3,

133.5, 132.5, 131.6, 131.4, 130.5, 130.3, 129.4, 129.2, 128.7, 128.6,

127.5, 127.2, 127.0, 126.8, 126.6, 125.9, 125.7, 125.6, 124.6, 124.1,

123.4, 123.1, 122.9, 121.8, 120.9, 111.9, 111.6 ppm. HRMS (EI):

calcd. for C₃₀H₁₈O [M⁺] 394.1358; found 394.1356.

[2-(Dibenzo[b,d]furan-2-carbonyl)phenyl](4-methoxyphenyl) meth-

anone (29g): Ring opening of 3-(dibenzo[b,d]furan-2-yl)isobenzo-

furan-1(3H)-one^[34](2 g, 6.67 mmol) with freshly prepared p-anisyl-

magnesium bromide followed by acidic workup gave benzo[c]furan

28g as a fluorescent bright yellow solid. Oxidation of benzo[c]furan

28g (2.0 g, 5.12 mmol) with MnO₂(1.33 g, 15.38 mmol) by follow-

ing a procedure similar to that for 20a afforded diketone 29g

(1.90 g, 91 %) as a colorless solid, m.p. 156–158 °C. ¹H NMR

(9-Hexyl-9H-carbazol-3-yl)[2-(2-thienoyl)phenyl]methanone (29i):

Interaction of 3-(N-hexylcarbazol-3-yl)isobenzofuran-1(3H)-one^[34]

with freshly prepared 2-thienylmagnesium bromide followed by

acidic workup gave benzo[c]furan 28i as a thick orange liquid.

Oxidation of benzo[c]furan 28i (0.83 g, 1.85 mmol) with MnO₂

(0.48 g, 5.54 mmol) by following a procedure similar to that for 20a

afforded diketone 29i (0.75 g, 85%) as a thick yellow liquid. ¹H

NMR (300 MHz, CDCl₃): δ = 8.37 (s, 1 H), 7.87–7.84 (m, 1 H),

(300 MHz, CDCl₃): δ = 8.34 (s, 1 H), 7.92–7.90 (m, 1 H), 7.87– 7.77 (d, J = 8.7 Hz, 1 H), 7.62–7.60 (m, 1 H), 7.58–7.53 (m, 1 H),

7.83 (m, 1 H), 7.71–7.65 (m, 6 H), 7.58 (d, J = 8.4 Hz, 1 H), 7.53– 7.48–7.43 (m, 2 H), 7.38 (t, J = 6.6 Hz, 2 H), 7.33–7.27 (m, 1 H),

7.49 (m, 2 H), 7.38–7.33 (m, 1 H), 6.83 (d, J = 9.0 Hz, 2 H), 3.82 7.25–7.21 (m, 1 H), 7.18–7.14 (m, 1 H), 7.1–7.05 (m, 1 H) 4.08 (t,

(s, 3 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 196.3, 195.4, J = 6.9 Hz, 2 H, NCH₂), 1.67–1.66 (m, 2 H, CH₂), 1.13 (s, 6 H,

163.6, 128.9, 156.9, 140.4, 140.3, 133.3, 132.6, 132.3, 130.2, 129.6,

129.5, 129.4, 127.9, 124.4, 123.7, 123.3, 123.2, 121.1, 120.3, 113.6,

111.9, 111.5, 55.5 ppm. C₂₇H₁₈O₄(406.44): calcd. C 79.79, H 4.46;

found C 79.58, H 4.63.

CH₂), 0.71 (t, J = 3.3 Hz, 3 H, CH₃) ppm. ¹³C NMR (75.4 MHz,

CDCl₃): δ = 196.1, 188.6, 144.2, 143.3, 141.1, 140.7, 139.8, 135.0,

134.6, 130.5, 130.0, 129.8, 129.1, 128.5, 128.1, 128.0, 126.5, 123.8,

123.1, 122.5, 120.8, 120.0, 109.3, 108.4, 43.3, 31.6, 28.9, 27.0, 22.6,

14.1 ppm. C₃₀H₂₇NO₂S (465.61): calcd. C 77.39, H 5.84, N 3.01, S

6.89; found C 77.43, H 5.72, N 2.93, S 6.78.

7-(4-Methoxyphenyl)anthra[2,3-b]benzo[d]furan (31g): Reduction of

diketone 29g (1.0 g, 2.46 mmol) with sodium borohydride (0.47 g,

12.37 mmol) followed by workup led to diol 30g. Crude diol 30g

(1.0 g, 2.45 mmol) upon annulation with HBr (33 %, 0.97 g,

12.2 mmol) in acetic acid by adopting a procedure similar to that

for 14a afforded 31g (0.81 g, 89%) as a yellow solid, m.p. 200–

Annulation of Diol 30i: Reduction of diketone 29i (0.7 g,

1.49 mmol) with sodium borohydride (0.28 g, 7.46 mmol) followed

by workup led to diol 30i. Crude diol 30i (0.71 g, 1.51 mmol) upon

annulation with HBr (33%, 0.61 g, 7.56 mmol) in acetic acid fol-

7830

www.eurjoc.org

Eur. J. Org. Chem. 2015, 7816–7835

Anthracene, Tetracene, and Naphtho[b]thiophene Analogues

lowed by workup and purification by column chromatography (sil-

ica gel; hexane) led to the isolation of naphtho[b]carbazole 31i

(0.29 g, 45%). Further elution of the column (silica gel; hexane/

(9-Hexyl-9H-carbazol-3-yl)[2-(4-methoxybenzoyl)phenyl]methanone

(29k): Interaction of 3-(N-hexylcarbazol-3-yl)isobenzofuran-1(3H)-

one^[34](2.0 g, 5.18 mmol) with p-anisylmagnesium bromide fol-

ethyl acetate, 99:1) afforded naphtho[b]thiophene 31iЈ (0.23 g, 36%) lowed by acidic workup gave benzo[c]furan 28k as a thick orange

as a yellow solid.

liquid. Oxidation of benzo[c]furan 28k (1.80 g, 11.11 mmol) with

MnO₂(1.02 g, 7.91 mmol) by following a procedure similar to that

for 20a afforded diketone 29k (1.50 g, 81%) as a thick yellow li-

5-Hexyl-7-(thiophen-2-yl)-5H-naphtho[2,3-b]carbazole (31i): M.p.

128–130 °C. ¹H NMR (300 MHz, CDCl₃): δ = 8.41 (s, 1 H), 8.2 (s,

1 H), 8.05 (d, J = 7.8 Hz, 1 H), 7.97 (d, J = 8.4 Hz, 1 H), 7.90 (d,

J = 8.7 Hz, 1 H), 7.55 (s, 2 H), 7.52–7.44 (m, 3 H), 7.38–7.34 (m,

2 H), 7.24–7.16 (m, 2 H), 4.38 (t, J = 7.2 Hz, 2 H, -CH₂), 2.0–1.92

(m, 2 H, -CH₂), 1.68–1.64 (m, 2 H, -CH₂), 1.5–1.36 (m, 4 H, -CH₂),

0.90 (t, J = 6.6 Hz, 3 H, -CH₃) ppm. ¹³C NMR (75.4 MHz,

CDCl₃): δ = 140.9, 140.2, 140.1, 138.2, 134.2, 131.7, 129.6, 129.5,

129.0, 128.4, 127.6, 125.9, 125.6, 125.1, 124.7, 123.9, 123.2, 122.9,

122.0, 121.1, 120.5, 119.0, 108.9, 108.5, 43.4, 31.6, 29.0, 27.0, 22.6,

14.0 ppm. DEPT-135 (75.4 MHz, CDCl₃): δ = 128.4, 127.5, 127.3,

126.9, 125.9, 125.1, 124.8, 124.1, 122.5, 120.5, 120.1, 119.0, 108.9,

108.5, 43.4, 31.7, 29.1, 27.1, 22.6, 14.1 ppm.

1

quid. H NMR (300 MHz, CDCl₃): δ = 8.46 (s, 1 H), 8.02 (d, J =

7.8 Hz, 1 H), 7.90–7.86 (m, 1 H), 7.70–7.67 (m, 3 H), 7.62–7.58 (m,

3 H), 7.47–7.44 (m, 1 H), 7.40 (d, J = 8.4 Hz, 1 H), 7.31 (d, J =

8.7 Hz, 1 H), 7.26–7.21 (m, 1 H), 6.81–6.80 (m, 2 H), 4.26 (t, J =

7.2 Hz, 2 H, -NCH₂), 3.77 (s, 3 H), 1.84–1.82 (m, 2 H), 1.31–1.26

(m, 6 H), 0.85 (t, J = 7.2 Hz, 3 H) ppm. ¹³C NMR (75.4 MHz,

CDCl₃): δ = 196.3, 195.6, 163.5, 143.3, 141.1, 140.9, 132.3, 130.4,

129.9, 129.8, 129.6, 129.3, 128.6, 128.2, 128.1, 126.4, 123.8, 123.2,

122.5, 120.8, 119.9, 113.5, 109.2, 108.3, 55.4, 43.3, 31.5, 28.9, 26.9,

22.5, 14.0 ppm. C₃₃H₃₁NO₃(489.61): calcd. C 80.95, H 6.38, N

2.86; found C 80.87, H 6.31, N 2.72.

5-Hexyl-7-(4-methoxyphenyl)-5H-naphtho[2,3-b]carbazole (31k):

Reduction of diketone 29k (0.90 g, 1.89 mmol) with sodium

borohydride (0.36 g, 9.47 mmol) followed by workup led to diol

30k. Crude diol 30k (0.72 g, 1.46 mmol) upon annulation with HBr

(33%, 0.59 g, 22.12 mmol) in acetic acid by adopting a procedure

similar to that for 14a afforded compound 31k (0.53 g, 78%) as a

yellow solid, m.p. 163–165 °C. ¹H NMR (300 MHz, CDCl₃): δ =

8.75 (s, 1 H), 8.71 (s, 1 H), 8.23 (d, J = 7.5 Hz, 1 H), 8.06 (d, J =

8.4 Hz, 1 H), 7.70 (d, J = 8.4 Hz, 1 H), 7.52 (t, J = 7.5 Hz, 1 H),

7.45–7.39 (m, 4 H), 7.36–7.26 (m, 4 H), 7.20–7.15 (m, 2 H), 4.14–

4.09 (m, 2 H), 3.99 (s, 3 H), 1.80–1.75 (m, 2 H), 1.30–1.25 (m, 6

H), 0.90–0.82 (m, 3 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ =

158.9, 144.2, 141.0, 134.4, 132.5, 131.9, 130.5, 130.0, 129.3, 128.4,

127.8, 127.4, 126.9, 126.5, 126.4, 124.8, 123.5, 122.6, 121.3, 118.7,

114.0, 108.0, 100.6, 55.4, 42.9, 31.4, 28.1, 26.9, 22.5, 14.0 ppm.

HRMS (EI): calcd. for C₃₃H₃₁NO [M⁺] 457.2406; found 457.2400.

9-Hexyl-3-(naphtho[2,3-b]thiophen-4-yl)-9H-carbazole (31iЈ): M.p.

124–128 °C. H NMR (300 MHz, CDCl₃): δ = 8.35 (s, 1 H), 8.30

1

(s, 1 H), 8.05 (t, J = 8.7 Hz, 2 H), 7.87 (d, J = 8.4 Hz, 1 H), 7.66–

7.56 (m, 2 H),7.52–7.45 (m, 5 H), 7.37 (t, J = 7.5 Hz, 1 H), 7.23–

7.20 (m, 1 H), 4.38 (m, J = 7.5 Hz, 2 H, CH₂), 2.02–1.92 (m, 2 H,

CH₂), 1.52–1.44 (m, 2 H, CH₂), 1.37–1.36 (m, 4 H, CH₂), 0.90 (t,

J = 6.6 Hz, 3 H, CH₃) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ =

140.9, 140.2, 138.2, 134.2, 131.7, 129.6, 129.5, 129.0, 128.4, 127.6,

125.9, 125.6, 125.1, 123.9, 123.2, 122.0, 121.1, 120.5, 119.0, 108.9,

108.8, 43.4, 31.6, 29.1, 27.1, 22.6, 14.0 ppm.

(9-Hexyl-9H-carbazol-3-yl)[2-(4-methylbenzoyl)phenyl]methanone

(29j): Interaction of 3-(N-hexylcarbazol-3-yl)isobenzofuran-1(3H)-

one^[34](1 g, 2.61 mmol) with p-tolylmagnesium bromide followed

by acidic workup gave benzo[c]furan 28j as a thick orange liquid

(0.69 g, 58%). Oxidation of benzo[c]furan 28j (0.5 g, 1.02 mmol)

with MnO₂(0.26 g, 3.08 mmol) by following a procedure similar to

that for 20a afforded diketone 29j (0.42 g, 80%) as a thick yellow

{2-[4-(Diphenylamino)benzoyl]phenyl}(p-tolyl)methanone (29l): Ring

opening of 3-[4-(diphenylamino)phenyl]isobenzofuran-1(3H)-

one^[34](2 g, 5.30 mmol) with freshly prepared p-tolylmagnesium

bromide followed by acidic workup gave benzo[c]furan 28l as a

fluorescent bright yellow solid. Oxidation of benzo[c]furan 28l

(1.5 g, 3.32 mmol) with MnO₂(0.87 g, 10.0 mmol) by following a

procedure similar to that for 20a afforded diketone 29l (1.38 g,

92%) as a colorless solid, m.p. 128–130 °C. ¹H NMR (300 MHz,

CDCl₃): δ = 7.64–7.60 (m, 3 H), 7.55–7.52 (m, 5 H), 7.32–7.25 (m,

4 H), 7.18 (d, J = 7.8 Hz, 2 H), 7.13–7.11 (m, 6 H), 6.88 (d, J =

8.7 Hz), 2.39 (s, 3 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ =

196.5, 195.0, 152.1, 146.4, 143.8, 140.6, 140.1, 134.8, 131.6, 130.1,

130.0, 129.8, 129.7, 129.6, 129.4, 129.3, 129.2, 129.0, 126.0, 124.7,

119.4, 21.7 ppm. C₃₃H₂₅NO₂(467.57): calcd. C 84.77, H 5.39, N

3.00; found C 84.98, H 5.22, N 3.19.

1

liquid. H NMR (300 MHz, CDCl₃): δ = 8.38 (s, 1 H), 7.94 (d, J

= 7.8 Hz, 1 H), 7.79 (d, J = 8.7 Hz, 1 H), 7.63–7.52 (m, 6 H), 7.37

(d, J = 7.5 Hz, 1 H), 7.31 (d, J = 8.1 Hz, 1 H), 7.23 (d, J = 8.7 Hz,

1 H), 7.15 (t, J = 7.4 Hz, 1 H), 7.03 (d, J = 8.1 Hz, 2 H), 4.18 (t,

J = 7.2 Hz, 2 H), 2.24 (s, 3 H), 1.78–1.71 (m, 2 H), 1.22–1.20 (m,

6 H), 0.77 (t, J = 6.8 Hz, 3 H) ppm. ¹³C NMR (75.4 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, 22.5, 21.7,

14.0 ppm. C₃₃H₃₁NO₂(473.61): calcd. C 83.69, H 6.60, N 2.96;

found C 83.58, H 6.51, N 2.85.

5-Hexyl-7-p-tolyl-5H-naphtho[2,3-b]carbazole (31j): Reduction of

diketone 29j (0.82 g, 1.68 mmol) with sodium borohydride (0.39 g,

10.26 mmol) followed by workup led to diol 30j. Crude diol 30j

(0.70 g, 1.45 mmol) upon annulation with HBr (33 %, 0.59 g,

7.29 mmol) in acetic acid by adopting a procedure similar to that

for 14a afforded carbazole 31j (0.50 g, 78%) as a yellow solid, m.p.

N,N-Diphenyl-9-p-tolylanthracen-2-amine (31l): Reduction of diket-

one 29l (1.0 g, 2.14 mmol) with sodium borohydride (0.40 g,

10.52 mmol) followed by workup gave diol 29l. Crude diol 29l

(1.1 g, 2.33 mmol) upon annulation with HBr (33 %, 0.94 g,

11.61 mmol) in acetic acid by adopting a procedure similar to that

for 14a afforded compound 31l (0.74 g, 73%) as a pale green solid,

1

162–164 °C. H NMR (300 MHz, CDCl₃): δ = 8.68 (s, 1 H), 8.64

1

(s, 1 H), 8.16 (d, J = 7.5 Hz, 1 H), 7.99 (d, J = 8.4 Hz, 1 H), 7.62

m.p. 142–144 °C. H NMR (300 MHz, CDCl₃): δ = 8.41 (s, 1 H),

(d, J = 8.7 Hz, 1 H), 7.35–7.33 (m, 6 H), 7.25–7.15 (m, 4 H), 4.05– 7.99 (d, J = 8.1 Hz, 1 H), 7.93 (d, J = 8.7 Hz, 1 H), 7.75 (d, J =

4.01 (m, 2 H), 2.45 (s, 3 H), 1.72–1.68 (m, 2 H), 1.20–1.17 (m, 6

H), 0.79–0.77 (m, 3 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ =

144.2, 141.0, 136.8, 136.7, 134.7, 131.4, 130.2, 129.8, 129.3, 129.2,

128.4, 127.8, 127.4, 126.9, 126.5, 126.4, 124.8, 123.5, 122.6, 121.3,

118.7, 108.0, 100.7, 42.8, 31.4, 28.0, 26.9, 22.5, 21.5, 14.0 ppm.

HRMS (EI): calcd. for C₃₃H₃₁N [M⁺] 441.2457; found 441.2450.

8.4 Hz, 1 H), 7.53 (s, 1 H), 7.44–7.35 (m, 3 H), 7.32–7.22 (m, 6 H),

7.06 (t, J = 7.2 Hz, 2 H), 2.46 (s, 3 H) ppm. ¹³C NMR (75.4 MHz,

CDCl₃): δ = 147.9, 147.0, 135.8, 134.9, 132.6, 132.1, 131.0, 130.6,

130.1, 129.0, 128.4, 128.3, 128.0, 126.8, 126.2, 125.2, 125.0, 124.7,

123.1, 123.0, 22.4 ppm. HRMS (EI): calcd. for C₃₃H₂₅N [M⁺]

435.1987; found 435.1987.

Eur. J. Org. Chem. 2015, 7816–7835

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7831

A. K. Mohanakrishnan et al.

{2-[4-(Diphenylamino)benzoyl]phenyl}(4-methoxyphenyl)methanone 134.5, 133.1, 130.9, 130.2, 130.1, 129.9, 128.8, 128.7, 128.4,

FULL PAPER

(29m): Ring opening of 3-[4-(diphenylamino)phenyl]isobenzofuran-

1(3H)-one^[34](2 g, 5.83 mmol) with freshly prepared p-anisylmag-

nesium bromide followed by acidic workup gave benzo[c]furan 28m

as a fluorescent bright yellow solid. Oxidation of benzo[c]furan

28m (0.2 g, 0.42 mmol) with MnO₂(0.11 g, 1.26 mmol) by follow-

ing a procedure similar to that for 20a afforded diketone 29m

(0.19 g, 93 %) as a colorless solid, m.p. 144–146 °C. ¹H NMR

(300 MHz, CDCl₃): δ = 7.64 (d, J = 8.7 Hz, 2 H), 7.53–7.44 (m, 6

H), 7.25–7.18 (m, 4 H), 7.05–7.03 (m, 6 H), 6.82–6.78 (m, 4 H),

3.77 (s, 3 H) ppm. ¹³C NMR (75.4 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 ppm.

128.1 ppm.

4-Phenylanthra[2,3-b]thiophene (35b): Reduction of diketone 33b

(0.5 g, 1.46 mmol) with sodium borohydride (0.21 g, 5.84 mmol)

followed by workup gave diol 34b. Crude diol 34b (0.4 g,

0.45 mmol) upon annulation with HBr (33%, 0.21 g, 1.43 mmol) in

acetic acid by adopting a procedure similar to that for 14a afforded

compound 35b (0.24 g, 68%) as a yellow solid, m.p. 177–178 °C.

¹H NMR (300 MHz, CDCl₃): δ = 8.54 (s, 1 H), 8.52 (s, 1 H), 8.42

(s, 1 H), 7.99 (d, J = 8.4 Hz, 1 H), 7.86 (d, J = 8.1 Hz, 1 H), 7.65–

7.56 (m, 5 H), 7.43–7.35 (m, 3 H), 7.11 (d, J = 5.7 Hz, 1 H) ppm.

¹³C NMR (75.4 MHz, CDCl₃): δ = 139.0, 137.9, 137.5, 134.1,

131.1, 130.9, 130.2, 129.8, 128.6, 128.5, 128.3, 128.2, 127.9, 127.7,

125.4, 125.3, 125.2, 124.9, 123.5, 120.4 ppm. C₂₂H₁₄S (310.41):

calcd. C 85.12, H 4.55, S 10.33; found C 84.93, H 4.68.

C

₃₃H₂₅NO₃(483.57): calcd. C 81.97, H 5.21, N 2.90; found C

81.84, H 5.09, N 2.99.

9-(4-Methoxyphenyl)-N,N-diphenylanthracen-2-amine (31m): Re-

duction of diketone 29m (0.20 g, 0.41 mmol) with sodium boro-

hydride (0.07 g, 18.42 mmol) followed by workup gave diol 30m.

Crude diol 30m (0.22 g, 0.45 mmol) upon annulation with HBr

(33%, 0.18 g, 2.22 mmol) in acetic acid by adopting a procedure

similar to that for 14a afforded compound 31m (0.14 g, 68%) as a

[3-(4-Methylbenzoyl)naphthalen-2-yl](thiophen-2-yl)methanone

(33c): Condensation of 1-(thiophen-2-yl)-4-p-tolylbutane-1,4-dione

32c (1.1 g, 4.26 mmol) with phthalaldehyde (0.57 g, 4.25 mmol) and

tBuOK (1.19 g, 10.60 mmol) by adopting a procedure similar to

that for 32a furnished diketone 33c (1.25 g, 83%) as a colorless

1

solid, m.p. 142–144 °C. H NMR (300 MHz, CDCl₃): δ = 8.23 (s,

1

pale green solid, m.p. 158–160 °C. H NMR (300 MHz, CDCl₃): δ

1 H), 8.08 (s, 1 H), 7.97–7.95 (m, 2 H), 7.73–7.60 (m, 6 H), 7.25–

7.20 (m, 2 H), 7.12–7.10 (m, 1 H), 2.4 (s, 3 H) ppm. ¹³C NMR

(75.4 MHz, CDCl₃): δ = 196.0, 188.1, 144.2, 143.9, 136.9, 136.8,

134.9, 134.6, 133.1,133.0, 130.7, 130.2, 130.1, 129.1, 128.8, 128.6,

128.0, 21.7 ppm. C₂₃H₁₆O₂S (356.44): calcd. C 77.50, H 4.52, S

9.00; found C 77.37, H 4.61, S 8.87.

= 8.26 (s, 1 H), 7.88 (d, J = 8.7 Hz, 1 H), 7.80 (d, J = 9.0 Hz, 1

H), 7.60 (d, J = 8.4 Hz, 1 H), 7.38 (d, J = 9.0 Hz, 1 H), 7.25–7.24

(m, 1 H), 7.16–7.09 (m, 8 H), 7.01–6.99 (m, 3 H), 6.99–6.81 (m, 2

H), 2.91 (s, 3 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 157.7,

146.3, 133.8, 131.2, 131.0, 130.3, 129.8, 129.7, 129.4, 128.3, 128.2,

128.1, 127.7, 127.4, 126.7, 125.5, 125.4, 125.0, 124.3, 123.5, 123.4,

122.4, 121.9, 116.7, 113.1, 112.6, 54.3 ppm. C₃₃H₂₅NO (451.57):

calcd. C 87.77, H 5.58, N 3.10; found C 87.65, H 5.69, N 3.01.

4-p-Tolylanthra[2,3-b]thiophene (35c): Reduction of diketone 33c

(0.8 g, 2.24 mmol) with sodium borohydride (0.42 g, 11.05 mmol)

followed by workup gave diol 34c. Crude diol 34c (0.8 g,

2.22 mmol) upon annulation with HBr (33%, 0.89 g, 10.99 mmol)

in acetic acid by adopting a procedure similar to that for 14a af-

forded compound 35c (0.51 g, 74%) as a yellow solid, m.p. 132–

Naphthalene-2,3-bis(phenylmethanone) (33a): 1,4-Diphenylbutane-

1,4-dione 32a (1.0 g, 4.20 mmol) and phthalaldehyde (0.56 g,

4.18 mmol) were dissolved in hot ethanol (25 mL). To this, tBuOK

(1.13 g, 10 mmol) was slowly added and the reaction mixture was

stirred for 3 h at room temperature. The solid obtained was filtered

and washed with methanol (10 mL) to afford diketone 33a (1.01 g,

72 %) as a colorless solid, m.p. 156 °C. ¹H NMR (300 MHz,

CDCl₃): δ = 8.09 (s, 2 H), 7.94–7.90 (m, 2 H), 7.80 (d, J = 7.5 Hz,

4 H), 7.65–7.62 (m, 2 H), 7.53 (t, J = 7.2 Hz, 2 H), 7.40 (t, J =

7.5 Hz, 4 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 196.3, 137.4,

137.0, 133.0, 132.9, 130.8, 129.9, 128.8, 128.7, 128.4 ppm.

1

134 °C. H NMR (300 MHz, CDCl₃): δ = 8.55–854 (m, 2 H), 8.42

(s, 1 H), 8.0 (d, J = 8.4 Hz, 1 H), 7.85 (d, J = 8.4 Hz, 1 H), 7.47–

7.38 (m, 5 H), 7.36–7.35 (m, 2 H), 7.11 (d, J = 5.7 Hz, 1 H), 2.54

(s, 3 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 138.0, 137.6,

135.9, 134.2, 131.1, 131.0, 130.7, 129.9, 129.2, 128.6, 128.5, 128.0,

127.8, 125.4, 125.3, 124.9, 124.8, 123.7, 120.1, 21.4 ppm. DEPT-

135 (75.4 MHz, CDCl₃): δ = 130.7, 129.2, 128.6, 128.0, 127.8,

125.4, 125.3, 124.8, 123.7, 120.1, 21.4 ppm. HRMS (EI): calcd. for

C₂₃H₁₆S [M⁺] 324.0973; found 324.0970.

5-Phenyltetracene (35a): Reduction of crude diketone 33a (0.5 g,

1.49 mmol) with sodium borohydride (0.22 g, 5.95 mmol) followed

by workup gave diol 34a. Crude diol 34a (0.4 g, 0.45 mmol) upon

annulation with HBr (33%, 0.21 g, 1.43 mmol) in acetic acid by

adopting a procedure similar to that for 14a afforded compound

35a^[35](0.25 g, 71%) as a pale green solid, m.p. 177–178 °C. ¹H

NMR (300 MHz, CDCl₃): δ = 8.71 (s, 1 H), 8.68 (s, 1 H), 8.29 (s,

1 H), 8.03–7.96 (m, 2 H), 7.80 (d, J = 8.4 Hz, 1 H), 7.67–7.59 (m,

4 H), 7.51 (d, J = 6.3 Hz, 2 H), 7.41–7.36 (m, 4 H) ppm. ¹³C NMR

(75.4 MHz, CDCl₃): δ = 139.0, 136.9, 131.5, 131.4, 131.2, 131.1,

130.0, 129.7, 129.4, 128.8, 128.5, 127.9, 127.6, 126.9, 126.7, 126.4,

125.6, 125.3, 125.1, 125.0, 124.8 ppm.

[3-(1-Naphthoyl)naphthalen-2-yl](thiophen-2-yl)methanone (33d):

Condensation of 1-(naphthalen-1-yl)-4-(thiophen-2-yl)butane-1,4-

dione (32d) (1.1 g, 3.74 mmol) with phthalaldehyde (0.50 g,

3.73 mmol) and tBuOK (1.04 g, 9.26 mmol) by adopting a pro-

cedure similar to that for 32a furnished compound 33d (1.23 g,

84%) as a colorless solid, m.p. 186–188 °C. ¹H NMR (300 MHz,

CDCl₃): δ = 8.27 (s, 1 H), 8.16 (d, J = 8.1 Hz, 2 H), 7.99–7.93 (m,

3 H), 7.88–7.80 (m, 3 H), 7.68–7.54 (m, 5 H), 7.51–7.46 (m, 1 H),

7.10–7.09 (m, 1 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 196.2,

188.0, 144.2, 137.0, 136.9, 135.6, 134.9, 134.8, 134.6, 133.1, 133.0,

132.3, 130.9, 129.6, 128.9, 128.8, 128.7, 128.5, 128.4, 128.0, 127.8,

126.7, 125.3 ppm. DEPT-135 (75.4 MHz, CDCl₃): δ = 134.9, 134.7,

132.3, 130.9, 130.2, 129.6, 128.9, 128.8, 128.7, 128.5, 128.4, 128.0,

127.8, 126.7, 125.2 ppm (only fifteen signals appeared instead of

sixteen). C₂₆H₁₆O₂S (392.47): calcd. C 79.57, H 4.11, S 8.17; found

C 79.43, H 3.93, S 8.31.

3-Benzoylnaphthalen-2-yl(thiophen-2-yl)methanone (33b): Conden-

sation of 1-phenyl-4-(thiophen-2-yl)butane-1,4-dione 32b (1.0 g,

4.10 mmol) with phthalaldehyde (0.55 g, 4.10 mmol) and tBuOK

(1.14 g, 10.24 mmol) by adopting a procedure similar to that for

32a furnished diketone 33b (1.01 g, 72%) as a colorless solid, m.p.

1

154–155 °C. H NMR (300 MHz, CDCl₃): δ = (s, 1 H), 7.97–7.92

2-(Benzo[a]tetracen-7-yl)thiophene (35d): Reduction of crude diket-

one 33d (0.96 g, 2.44 mmol) with sodium borohydride (0.46 g,

12.10 mmol) followed by workup gave diol 34d. Crude diol 34d

(1.0 g, 3.12 mmol) upon annulation with HBr (33 %, 1.22 g,

(m, 2 H), 7.86–7.83 (m, 2 H), 7.68–7.56 (m, 5 H), 7.44–7.41 (m, 2

H), 7.12–7.10 (m, 1 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ =

196.3, 188.1, 144.1, 137.4, 136.8, 136.5, 136.3, 135.3, 134.9, 134.7,

7832

www.eurjoc.org

Eur. J. Org. Chem. 2015, 7816–7835

Anthracene, Tetracene, and Naphtho[b]thiophene Analogues

15.07 mmol) in acetic acid by adopting a procedure similar to that

followed by workup gave diol 39a. To a solution of crude diol 39a

for 14a afforded compound 35d (0.47 g, 87%) as a yellow solid,

(0.40 g, 0.89 mmol) in acetic acid (15 mL), HBr (33 %, 0.36 g,

1

m.p. 196–198 °C. H NMR (300 MHz, CDCl₃): δ = 8.63 (s, 1 H), 4.44 mmol) in acetic acid was added and stirred for 10 min (an

8.56 (s, 1 H), 8.46 (s, 1 H), 8.02 (d, J = 8.1 Hz, 1 H), 7.92 (d, J = intense red coloration was observed). The usual workup followed

8.4 Hz, 1 H), 7.71–7.64 (m, 4 H), 7.49–7.39 (m, 5 H), 7.27–7.21 (m, by column chromatography did not afford any detectable product.

2 H) ppm. ¹³C NMR (75.4 MHz, CDCl₃): δ = 143.3, 134.0, 132.3,

131.8, 131.5, 131.4, 130.9, 129.7, 129.1, 129.0, 128.9, 128.7, 128.6,

128.5, 128.2, 128.1, 127.8, 127.7, 127.6, 127.4, 127.0, 126.0, 125.8,

125.7, 125.2 ppm. DEPT-135 (75.4 MHz, CDCl₃): δ = 129.1, 129.0,

9-Hexyl-9H-carbazol-3-yl[3-(4-methoxybenzoyl)naphthalen-2-yl]-

methanone (38b): Ring opening of 3-(9-hexyl-9H-carbazol-3-yl)-

3,3a-dihydronaphtho[2,3-c]furan-1(9aH)-one^[29]36 (2.0 g,

4.61 mmol) with freshly prepared p-anisylmagnesium bromide fol-

lowed by basic workup gave keto alcohol 37b. Oxidation of crude

keto alcohol 37b (1.0 g, 1.84 mmol) with PCC (0.59 g, 8.35 mmol)

128.7, 128.5, 128.2, 128.1, 127.7, 127.6, 127.4, 127.0, 126.0, 125.8,

125.7, 125.2 (only fourteen signals appeared instead of six-

teen) ppm. HRMS (EI): calcd. for C₂₆H₁₆S [M⁺] 360.0973; found

by following a procedure similar to that for 6a furnished the diket-

360.0970.

one 38b (0.73 g, 74%) as a thick brown liquid, ¹H NMR (300 MHz,

CDCl₃): δ = 8.58 (s, 1 H), 8.13 (s, 1 H), 8.06 (s, 1 H), 8.0–7.96 (m,

2 H), 7.87–7.86 (m, 2 H), 7.81–7.78 (m, 2 H), 7.57–7.54 (m, 2 H),

7.57–7.32 (m, 3 H), 7.17 (t, J = 6.9 Hz, 1 H), 6.80 (d, J = 8.7 Hz,

2 H), 4.21–4.17 (m, 2 H), 3.70 (s, 3 H), 1.81–1.77 (m, 2 H), 1.27–

1.26 (m, 6 H), 0.85–0.83 (m, 3 H) ppm. ¹³C NMR (75.4 MHz,

CDCl₃): δ = 196.1, 195.3, 163.5, 143.3, 141.2, 138.2, 137.8, 133.0,

132.9, 132.8, 132.4, 130.6, 130.4, 130.1, 129.5, 129.0, 128.8, 128.4,

128.3, 126.4, 123.9, 123.2, 122.6, 120.8, 119.9, 113.6, 113.5, 108.4,

55.4, 43.3, 31.6, 28.9, 26.9, 22.6, 14.1 ppm. C₃₇H₃₃NO₃(539.67):

calcd. C 82.35, H 6.16, N 2.60; found C 82.41, H 6.02, N 2.48.

[3-(1-Naphthoyl)naphthalen-2-yl](phenyl)methanone (33e): Conden-

sation of 1-(naphthalen-1-yl)-4-phenylbutane-1,4-dione (32e)

(0.59 g, 2.0 mmol) with phthalaldehyde (0.27 g, 2.01 mmol) and

tBuOK (0.57 g, 5.07 mmol) by adopting a procedure similar to that

for 32a furnished compound 33e as a colorless solid (0.48 g, 81%)

1

as a yellow solid, m.p. 166–168 °C. H NMR (300 MHz, CDCl₃):

δ = 8.26 (s, 1 H), 8.15 (d, J = 8.1 Hz, 2 H), 7.97–7.91 (m, 3 H),

7.87–7.79 (m, 5 H), 7.68–7.65 (m, 2 H), 7.60–7.47 (m, 3 H), 7.38

(t, J = 7.8 Hz, 2 H) 2.54 (s, 3 H) ppm. ¹³C NMR (75.4 MHz,

CDCl₃): δ = 196.3, 137.5, 137.3, 137.1, 136.2, 135.5, 134.9, 133.1,

132.9, 132.3, 132.2, 130.9, 130.8, 130.0, 129.6, 128.9, 128.8, 128.7,

128.6, 128.5, 128.4, 128.3, 127.8, 126.7, 125.3 ppm. C₂₈H₁₈O₂

(386.45): calcd. C 87.02, H 4.69; found C 86.88, H 4.92.

Attempted Annulation of Diol 39b: Reduction of diketone 38b

(0.65 g, 1.23 mmol) with sodium borohydride (0.23 g, 6.05 mmol)

followed by workup gave diol 39b. To a solution of crude diol 39a

(0.40 g, 0.75 mmol) in acetic acid (15 mL), HBr (33 %, 0.31 g,

3.71 mmol) in acetic acid was added and stirred for 10 min (an

intense red coloration was observed). The usual workup followed

by column chromatography did not afford any detectable product.

7-Phenylbenzo[a]tetracene (35e): Reduction of crude diketone 33e

(0.42 g, 1.16 mmol) with sodium borohydride (0.22 g, 5.78 mmol)

followed by workup gave diol 34e. Crude diol 34e (1.0 g,

3.12 mmol) upon annulation with HBr (33%, 0.5 g, 1.36 mmol) in

acetic acid by adopting a procedure similar to that for 14a afforded

compound 35e (0.43 g, 89%) as a yellow solid, m.p. 200–202 °C.

¹H NMR (300 MHz, CDCl₃): δ = 8.56 (s, 1 H), 8.46 (s, 1 H), 8.12

(s, 1 H), 7.54 (d, J = 8.4 Hz, 1 H), 7.75 (d, J = 8.1 Hz, 1 H), 7.65–

7.53 (m, 5 H), 7.40–7.28 (m, 7 H), 6.97 (t, d, J = 8.1 Hz, 1 H) ppm.

¹³C NMR (75.4 MHz, CDCl₃): δ = 142.5, 137.3, 133.9, 131.5,

131.4, 131.3, 130.8, 130.0, 129.7, 129.1, 129.0, 128.5, 128.3, 127.8,

127.6, 127.5, 126.7, 126.6, 126.4, 125.6, 125.0 ppm. DEPT-135

(75.4 MHz, CDCl₃): δ = 130.8, 129.7, 129.1, 129.0, 128.5, 128.3,

127.8, 127.6, 127.5, 126.6, 126.4, 125.7, 125.6, 125.0 ppm (only

fourteen signals appeared instead of sixteen). HRMS (EI): calcd.

for C₂₈H₁₈[M⁺] 354.1409; found 354.1400.

Supporting Information (see footnote on the first page of this arti-

1

cle): Copies of H NMR, ¹³C NMR, and DEPT-135 spectra (only

selected cases) of final compounds.

Acknowledgments

R. S. thanks the University Grants Commission (UGC), New

Delhi for a fellowship. S. M. R. thanks Department of Science and

Technology (DST), New Delhi for a DST-INSPIRE fellowship.

E. S. thanks the Council of Scientific and Industrial Research

(CSIR) for a fellowship. The authors thank DST-FIST for the use

of the high-resolution NMR facility.

9-Hexyl-9H-carbazol-3-yl[3-(4-methylbenzoyl)naphthalen-2-yl]meth-

anone (38a): Ring opening of 3-(9-hexyl-9H-carbazol-3-yl)-3,3a-di-

hydronaphtho[2,3-c]furan-1(9aH)-one^[29](36) (2.0 g, 4.61 mmol)

with freshly prepared p-tolylmagnesium bromide followed by an

aqueous NH₄Cl quench gave keto alcohol 37a. Keto alcohol 37a

(1.0 g, 1.90 mmol) upon oxidation with PCC (0.9 g, 2.85 mmol) by

following a procedure similar to that for 6a furnished diketone 38a

(0.78 g, 79 %) as a colorless solid, m.p. 82–84 °C. ¹H NMR

(300 MHz, CDCl₃): δ = 8.57 (s, 1 H), 8.15 (s, 1 H), 8.10 (s, 1 H),

8.01–7.98 (m, 2 H), 7.92–7.90 (m, 1 H), 7.72 (d, J = 7.8 Hz, 2 H),

7.62–7.59 (m, 2 H), 7.45–7.32 (m, 4 H), 7.23–7.21 (m, 1 H), 7.18–

7.14 (m, 2 H), 4.27–4.22 (m, 2 H), 2.33 (s, 3 H), 1.83–1.81 (m, 2 H),

1.30–1.26 (m, 6 H), 0.87–0.84 (m, 3 H) ppm. ¹³C NMR (75.4 MHz,

CDCl₃): δ = 196.2, 196.0, 143.6, 143.3, 141.2, 138.2, 137.6, 135.1,

133.1, 132.9, 130.5, 130.2, 129.7, 129.0, 128.9, 128.8, 128.6, 128.4,

128.3, 128.2, 126.6, 126.4, 123.9, 123.2, 122.6, 120.8, 119.9, 108.4,

43.3, 31.6, 28.9, 26.9, 22.5, 21.7, 14.0 ppm. C₃₇H₃₃NO₂(523.67):

calcd. C 84.86, H 6.35, N 2.67; found C 84.71, H 6.17, N 2.81.

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Received: August 21, 2015

Published Online: November 6, 2015

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7835

Article Doi

Regioselective annulation of unsymmetrical 1,2-phenylenebis(diaryl/diheteroarylmethanol): A facile synthesis of anthracene, tetracene, and naphtho[b]thiophene analogues

DOI: 10.1002/ejoc.201501087

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