Octahydro[1,4:5,8]dimethanoanthraquinone as a cheap and readily available electron-transfer oxidant for biaryl synthesis from organocuprates

Article abstract of DOI:10.1055/s-0028-1083232

The preparation of biaryls via oxidation of organocuprates with easily synthesized octahydro[1,4:5,8]dimethanoanthraquinone (DAQ) is described. The oxidative coupling of organocuprates using DAQ was successfully employed for the preparation of highly hind

Full text of DOI:10.1055/s-0028-1083232

PAPER
3769
Octahydro[1,4:5,8]dimethanoanthraquinone as a Cheap and Readily Avail-
able Electron-Transfer Oxidant for Biaryl Synthesis from Organocuprates
DAQas Oxidant
u
for
B
iaryl Sy
c
nthesis hi Shukla, Rajendra Rathore*
Department of Chemistry, Marquette University, P.O. Box 1881, Milwaukee, WI 53201, USA
Fax +1(414)2887066; E-mail: Rajendra.Rathore@marquette.edu
Received 18 July 2008; revised 11 September 2008
O
O
Abstract: The preparation of biaryls via oxidation of organocu-
prates with easily synthesized octahydro[1,4:5,8]dimethano-
EtOH
anthraquinone (DAQ) is described. The oxidative coupling of
organocuprates using DAQ was successfully employed for the
preparation of highly hindered biaryls and 9- and 10-membered
macrocycles containing biaryl linkages. The oxidative reactivity of
DAQ towards organocuprates is found to be similar to the common-
ly utilized quinones such as duroquinone (DQ) and tetra-tert-butyl-
biphenoquinone (BQ) and is in accord with their similar reduction
potentials (measured by an electrochemical method). The structures
of the quinones are also established with the aid of X-ray crystallog-
raphy. The usage of DAQ for biaryl synthesis is advocated owing to
the ready separation of reduced DAQ-H2 from biaryls as well as its
ready-availability in multi-gram quantities.
+
2
1
O
O
O
H2, Pd/C
EtOH
OH
OH
Br2
CHCl3
3
O
2
cat. [NOx]
O2
Key words: quinones, one-electron transfer, organocuprates, bi-
aryls, macrocycles
O
Aryl–aryl bond-forming reactions1 are of significant im-
portance not only as tools in modern organic syntheses of
natural products, but also for the preparation of novel
materials2 used in the emerging areas of molecular elec-
tronics and nanotechnology.3 Generally, the construction
of biaryl linkages is carried out from various aryl halides
using palladium, nickel, copper, and iron-catalyzed chem-
istry.1 Recently, a number of reports have shown that the
formation of biaryl linkages can also be accomplished via
electron-transfer oxidation of organomagnesium and lith-
ium reagents,4 or organocuprates using mild oxidants such
as tetramethyl-p-benzoquinone5 (or duroquinone, DQ),
tetra-tert-butylbiphenoquinone6 (BQ), substituted ni-
trobenzenes,7 etc. These synthetic transformations for the
formation of biaryl linkages are important owing to the
fact that they allow the construction of macrocycles con-
taining biaryl linkages.4,5
DAQ
O
Scheme 1 Synthetic route for the preparation of multi-gram quanti-
ties of DAQ
sor to DAQ (hydroquinone 3) can be easily obtained in
multi-gram quantities (25–100 g) using readily available
and cheap starting materials from a recently published
procedure in Organic Syntheses10 (Scheme 1).
Thus, a reaction of cyclopentadiene with p-benzoquinone
affords a quantitative yield of the Diels–Alder adduct 1,
which is easily hydrogenated to the corresponding dike-
tone 2 in quantitative yield. The treatment of diketone 2
with one equivalent of bromine in chloroform or dichlo-
romethane gives a quantitative yield of the sparingly
soluble hydroquinone 3. Secondly, the resulting hydro-
quinone 3 (without isolation) can be efficiently oxidized
to the corresponding quinone (DAQ) using a catalytic
amount of nitrogen oxides9 (which can be easily generated
using sodium nitrite and sulfuric acid) and air or oxygen
as the oxidant. A detailed, one-pot procedure for a conve-
nient preparation of DAQ from 2 is described in the exper-
imental section. It is also noted that DAQ is readily
soluble in various organic solvents; however the corre-
sponding hydroquinone, DAQ-H2 (3), is almost insoluble
in various organic solvents, which allows the ready sepa-
ration of the biaryls from the reduced hydroquinone. It is
noteworthy that both tetra-tert-butylbiphenoquinone
(BQ) and reduced BQ-H2 are equally soluble in various
organic solvents owing to the presence of bulky tert-butyl
Our interest in the preparation of a homologous series of
macrocycles8 containing tetramethoxybiaryl moieties
prompted us to explore the usage of this transformation
using the readily-available and cheap octahy-
dro[1,4:5,8]dimethanoanthraquinone (hereafter referred
as dimethanoanthraquinone or DAQ), which has largely
escaped attention as an oxidant.9 Herein, we advance the
usage of DAQ as an oxidant for the formation of biaryl
linkages due to the following reasons. Firstly, the precur-
SYNTHESIS 2008, No. 23, pp 3769–3774
x
x.
x
x
.
2
0
0
8
Advanced online publication: 14.11.2008
DOI: 10.1055/s-0028-1083232; Art ID: M03908SS
© Georg Thieme Verlag Stuttgart · New York

3770
R. Shukla, R. Rathore
PAPER
groups (vide infra), which prevent hydrogen bonding in- cally hindered biaryls (Table 1, entries 4–6). It is noted
teractions amongst the phenolic OH groups and thereby that the highly hindered biaryl 8 was produced in a rela-
complicating a ready isolation of the biaryls from the re- tively low yield (25%), however, in this context, it is also
action mixtures. Finally, the unhindered duroquinone important to note that attempted preparation of 8 via
(DQ) is expected to undergo association with reduced DQ Kumada coupling12 did not afford the desired biaryl 8,
leading to the formation of a dimer anion radical and quin- even in trace quantity!
hydrone,11 and thus necessitates the usage of excess
The structures of various biaryls in Table 1 were estab-
quinone for the coupling reactions.5
lished by 1H/13C NMR spectroscopy and were further con-
Accordingly, herein we demonstrate using a variety of ex- firmed either by mass spectrometry (see experimental
amples, that all the three quinones (DQ, BQ, and DAQ) section) or by comparison with the authentic samples.13
serve as effective oxidants for the preparation of biaryls
The versatility of the procedure in Equation 1 was further
from arylcuprates. The usage of DAQ for biaryl synthesis
demonstrated by its application for the preparation of
is advocated because of its ready availability in multi-
macrocycles with 9- and 10-membered rings containing a
gram quantities as well as the advantages presented
tetramethoxybiaryl linkage.8 It has been reported that
above. Moreover, we show that the biaryl synthesis pre-
sented herein can be employed for the preparation of
compounds 11a–c containing smaller ring (i.e., 6, 7, and
8-membered rings) linkage between the tetramethoxybi-
hitherto unknown large macrocycles containing biaryl
aryls can be readily synthesized via oxidative coupling of
linkages as follows.
the a,w-bis(3,4-dimethoxyphenyl)alkanes 10a–c using
We initially compared the efficacy of DAQ with com- various chemical oxidants14 or via electrochemical
monly utilized DQ5 and BQ6 for the oxidative coupling of oxidation15 (Equation 3).
an arylcuprate derived from 2-bromoanisole. Thus, a lithi-
ation of 2-bromoanisole with n-BuLi in diethyl ether at
n
n
oxidant
– 2 H+
–78 °C (1 h) followed by transmetalation using 0.5 equiv-
alent of CuCN produces a diarylcuprate, which was sub-
jected to oxidative coupling using DAQ, DQ, and BQ in
three separate experiments to afford 2,2¢-dimethoxybi-
phenyl, which, in each case, was formed in excellent yield
(Equation 1).
O
O
O
O
O
O
O
O
10a: n = –1
10b: n = 0
10c: n = 1
11a: n = –1
11b: n = 0
11c: n = 1
O
a) n-BuLi, Et2O, –78 °C
b) CuCN (0.5 equiv)
Equation 3
O
c) oxidant
However, attempted preparation of the 9- and 10-mem-
bered macrocycles 11d and 11e via oxidative cyclization
of 10d16 and 10e,17 according to the procedure in
Equation 3, yielded only a complex mixture of products;
and the mass spectral analysis of the soluble components
of these mixtures did not show the presence of 11d and
11e (Scheme 2).
Br
O
Oxidant used Yield (%)
DAQ
BQ
DQ
79
75
87
Equation 1
n
10d: n = 2
The oxidative coupling using DAQ is not limited to the or-
ganocuprates derived from organolithiums, but can also
be carried out equally effectively when they are derived
from the corresponding Grignard reagents (Equation 2).
10e: n = 3
O
O
O
O
oxidant
O
Br2, CH2Cl2
X
O
a) Mg, THF
b) CuCN (0.5 equiv)
c) DAQ
a) n-BuLi
b) CuCN
Br
n
n
O
Br
Br
90%
b) DAQ
O
O
Equation 2
O
O
O
O
O
O
12d: n = 2
12e: n = 3
11d: n = 2
11e: n = 3
The efficacy of the usage of DAQ for the oxidation of or-
ganocuprates was further demonstrated using a variety of
examples (Table 1). The procedure in Equation 1 can be
employed equally effectively for the preparation of steri-
Scheme 2 Preparation of macrocycles 11d and 11e
Synthesis 2008, No. 23, 3769–3774 © Thieme Stuttgart · New York

PAPER
DAQ as Oxidant for Biaryl Synthesis
3771
Table 1 Various Biaryls Synthesized
Entry
Substrate
Product
Methoda
Yield (%)
O
Br
Method A
Method B
79
90
1
4
O
O
Br
Method A
Method B
77
80
2
3
5
6
Br
Method A
74
O
O
O
Br
4
7
Method A
55
O
O
O
5
6
8
9
Method A
Method A
25
70
O
O
Br
O
Br
a Method A: using organolithiums; Method B: using Grignard reagents.
However, bromination of 10d (or 10e) with bromine in reversible for both DAQ and DQ, and occurring at
dichloromethane easily afforded the corresponding dibro- relatively negative potentials (see gray curves in
mo derivative 12d (or 12e) in quantitative yield. A double Figure 1). On the other hand, BQ showed two reversible
lithiation of 12d (or 12e) with n-BuLi (2.2 equiv) in dieth- reduction waves corresponding to the formation of the an-
yl ether at –78 °C (1.5 h) followed by transmetalation us- ion radical (Ered1 = –0.66 V vs. SCE) and dianion
ing 1 equivalent of CuCN and the oxidative coupling (Ered2 = –1.18 V vs. SCE), respectively. The first reduc-
using DAQ afforded, after chromatographic purification, tion potentials of the three quinones differed only by ~0.3
macrocycle 11d (or 11e), albeit in somewhat low yield V however, the potentials of the quinones employed here-
(20–26%) (Scheme 2).
in were sufficiently high to promote the highly exergonic
one-electron transfer from the electron-rich diarylcuprates
(Eox ~ –2 V vs. SCE).18
In order to gain further insight into the oxidative reactivity
of various quinones towards organocuprates, their electro-
chemical reduction potentials were determined by cyclic The structures of DAQ as well as BQ and DQ were also
voltammetry as follows. Each quinone was subjected to determined at –173 °C by X-ray crystallography19 and are
an electrochemical reduction at a platinum electrode as a compared in Figure 2. The C=O bond lengths in the vari-
2 mM solution in anhydrous tetrahydrofuran containing ous quinones were, expectedly, found to be rather invari-
0.1 M Bu4NPF6 as the supporting electrolyte. The cyclic ant (1.227, 1.226, and 1.228 Å for DAQ, DQ, and BQ,
voltammograms are compiled in Figure 1. The p-benzo- respectively), and the limited changes in C=O bond
quinone derivatives, DAQ and DQ, showed only one re- lengths were in line with the observed C=O stretching fre-
versible reduction wave (see blue curves in Figure 1) quencies (1644, 1636, 1605 cm–1 for DAQ, DQ, and BQ,
corresponding to the formation of monoanion radicals at respectively) in their infrared spectra, recorded as KBr
reduction potentials of –0.81 and –0.98 V versus SCE, re- pellets.
spectively. The second reduction wave was found to be ir-
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3772
R. Shukla, R. Rathore
PAPER
Figure 2 Comparison of the X-ray crystal structures of BQ (top),
DQ (middle), and DAQ (bottom) represented as ORTEP diagrams
with the thermal ellipsoid at 50% probability.
l,2,3,4,5,6,7,8-Octahydro[1,4:5,8]dimethano-9,l0-anthra-
quinone (DAQ)
Figure 1 Comparison of the cyclic voltammograms of various qui-
nones (2 mM) in THF (0.1 M Bu4NPF6) at a scan rate of 200 mV s–1.
Note that the first reduction wave of both DAQ and DQ are comple-
tely reversible (blue curves) if scanning is terminated before the start
of the second reduction event.
A 500-mL Schlenk flask, equipped with a 125 mL pressure-equal-
izing addition funnel, was charged with diketone 2 (18.3 g, 75
mmol) and anhyd CHCl3 (75 mL). A solution of Br2 (12.0 g, 75
mmol) in CHCl3 (75 mL) was added dropwise over a period of 30
min at 22 °C while a slow stream of argon was bubbled through the
mixture to remove gaseous HBr, which was formed during the reac-
tion. The resulting suspension of DAQ-H2 (3) was stirred for an ad-
ditional 1 h and then was cooled to –20 °C. A prechilled (–20 °C)
solution of NOx in CH2Cl2 (25mL), prepared separately (Note 1),
was quickly added to the above Schlenk flask, containing the cooled
suspension of 3 and equipped with an oxygen filled balloon via a
flow-control adapter. The resulting mixture was stirred at –20 °C
until the white suspension turned into a clear dark-yellow solution
(~4 h). At which time, the dark yellow solution was washed with aq
NaHCO3 (2 × 75 mL), dried (MgSO4) and evaporated under re-
duced pressure. The resulting crude yellow solid was recrystallized
from a 1:1 mixture of CH2Cl2 and acetone to afford bright yellow
crystals of DAQ in a nearly quantitative yield; yield: 16.4 g (91%);
mp 250–252 °C.
In summary, we have demonstrated that the easily synthe-
sized octahydro[1,4:5,8]dimethanoanthraquinone (DAQ)
can be successfully utilized as an efficient oxidant for the
biaryl synthesis using organocuprates. The efficacy of the
procedure is further delineated by the preparation of a
number of highly hindered biaryls as well as 9- and 10-
membered macrocycles containing biaryl linkages. It is
believed that the ready availability of DAQ as well as the
ease of the separation of biaryls from the reaction mix-
tures will lead to its widespread application in biaryl syn-
theses.
Note 1: A flask containing CH2Cl2 (25 mL) was cooled to –20 °C
(using a dry ice-acetone bath) and NOx, generated in a separate
round bottom flask fitted via dropwise addition of 10% H2SO4 (10
mL) to NaNO2 (5.0 g), was bubbled through using a cannula.
Melting points are uncorrected. IR spectra were recorded using KBr
disks on a Nicolet 560 Magna infrared spectrometer. NMR spectra
were obtained on a Varian NMR spectrometer (300 MHz) as CDCl3
solutions using TMS as an internal standard reference. GC-MS
spectra were obtained on a Fisons 8000 Trio instrument at an ion-
ization potential of 70 eV. TLC experiments were carried out on
precoated silica gel plates (hexanes–EtOAc, 5:1). Solvents and re-
agents were purchased from commercial sources. 2-Bromoanisole,
4-bromoanisole, bromobenzene, and 2-bromo-m-xylene were com-
mercially available. 2-Bromo-4,4¢-di-tert-butylbiphenyl,13 2-tert-
IR (KBr): 2995, 2971, 2952, 2875, 1648 (w), 1638 (s), 1569, 1330,
1272, 1210, 1119, 875, 760, 741 cm–1.
lH NMR (CDCl3): d = 1.14 (dd, J = 7.7, 2.2 Hz, 4 H), 1.35 (d,
J = 8.8 Hz, 2 H), 1.58 (d, J = 8.8 Hz, 2 H), 1.87 (d, J = 7.7 Hz, 4 H),
3.40 (s, 4 H).
13C NMR (CDCl3): d = 25.05, 40.46, 48.33, 151.25, 182.06.
MS (70 eV): m/z = 240 [M+], 212, 184, 92.
butyl-4,5-dimethoxybromobenzene,20
a,w-bis(dimethoxyphe-
nyl)alkanes 10d16 and 10e17 were prepared according to the litera-
ture procedures.
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DAQ as Oxidant for Biaryl Synthesis
3773
Biaryls 4–9; General and Typical Procedures
Bromination of a,w-Bis(3,4-dimethoxyphenyl)alkanes 10d and
10e; 1,5-Bis(6-bromo-3,4-dimethoxyphenyl)pentane (12d);
Typical Procedure
Method A, General Procedure: An argon-flushed Schlenk flask
(100 mL), equipped with a magnetic stirrer and a rubber septum was
charged with the respective aryl bromide (2.5 mmol) in anhyd Et2O
(50 mL). The mixture was cooled to –78 °C and n-BuLi (1.1 mL,
2.75 mmol, 2.5 M in hexane) was added dropwise. After stirring for
1.5 h at –78 °C, CuCN (112 mg, 1.25 mmol) was added to the mix-
ture and it was vigorously stirred at r.t. until the CuCN had dis-
solved (~30 min). Solid DAQ (0.7 g, 3 mmol) was added to this
stirred solution and the resulting mixture was stirred for an addition-
al 4 h. At which time, the reaction was quenched by the addition of
2 N aq HCl (20 mL). The organic layer was separated and the aque-
ous layer was further extracted with CH2Cl2 (3 × 20 mL). The com-
bined organic extracts were dried (MgSO4) and concentrated under
reduced pressure. Any unreacted DAQ was converted into DAQ-H2
by heating a CH2Cl2 solution (~25 mL) of the crude mixture with Zn
dust (1 g) in the presence of AcOH (1 mL) until the yellow color of
DAQ had completely disappeared (~5 min). The resulting mixture
was filtered to separate Zn dust and DAQ-H2 (Note 2), and the fil-
trate was washed with 10% aq NaHCO3 (2 × 25 mL), dried
(MgSO4), evaporated, and purified by column chromatography on
silica gel using a 9:1 mixture of hexanes–EtOAc as eluent.
To a solution of 1,5-bis(3,4-dimethoxyphenyl)pentane (10d; 2.0 g,
5.8 mmol) in CH2Cl2 (50 mL) was added dropwise a solution of Br2
(2.1 g, 12.8 mmol) in CH2Cl2 (20 mL). The resulting mixture was
stirred for 30 min and the reaction was quenched by the addition of
10% aq NaHSO3 (50 mL). The organic layer was separated and
washed further with aq NaHSO3 (2 × 25 mL) and dried (MgSO4).
Evaporation of the solvent afforded 12d as a white solid; yield: 2.8
g (95%); colorless crystals; mp 77–79 °C.
1H NMR (CDCl3): d = 1.62 (m, 4 H), 1.64 (m, 2 H), 2.67 (t, J = 7.2
Hz, 4 H), 3.85 (s, 6 H), 3.86 (s, 6 H), 6.71 (s, 2 H), 6.99 (s, 2 H).
13C NMR (CDCl3): d = 28.58, 29.47, 33.24, 56.15, 56.17, 111.81,
112.32, 133.98, 134.51, 146.75, 148.40.
MS (70 eV): m/z = 502 [M+], 229, 191, 151, 107.
1,6-Bis(6-bromo-3,4-dimethoxyphenyl)pentane (12e)
Yield: 2.7 g (92%); colorless crystals; mp 83–85 °C.
1H NMR (CDCl3): d = 1.42 (m, 4 H), 1.59 (m, 4 H), 2.64 (t, J = 7.85
Hz, 4 H), 3.84 (s, 6 H), 3.85 (s, 6 H), 6.70 (s, 2 H), 6.98 (s, 2 H).
13C NMR (CDCl3): d = 29.30, 30.42, 36.04, 56.22, 56.32, 113.08,
114.11, 115.65, 134.22, 147.81, 148.43.
Note 2: The hydroquinone DAQ-H2 (0.57 g, 80%) can be recovered
by stirring the above solid residue in aq 2 N HCl.
Method B, 2,2-Dimethoxybiphenyl (4); Typical Procedure: A solu-
tion of 1-bromo-2-methoxybenzene (0.47 g, 2.5 mmol) in THF (25
mL) was added dropwise via a pressure-equalizing funnel to a 100-
mL Schlenk flask containing Mg turnings (0.1 g, 4.0 mmol) and a
small crystal of I2 in THF (10 mL). The resulting mixture was re-
fluxed for 1 h and then cooled to r.t. Solid CuCN (112 mg, 1.25
mmol) was added to the resulting Grignard reagent and the mixture
was vigorously stirred at r.t. for 10 min. Solid DAQ (0.7 g, 3 mmol)
was added to this solution and the mixture was stirred for an addi-
tional 4 h. The workup was done as described in Method A to give
4; yield: 0.42 g (90%); mp 154–156 °C (Lit.21 mp 154–155 °C).
MS (70 eV): m/z = 516 [M+], 229, 191, 151.
6,7,8,9-Tetrahydro-2,3,11,12-tetramethoxydibenzo[a,c]cyclo-
nonene (11d)
Yield: 20%; colorless, low-melting solid.
1H NMR (CDCl3): d = 1.72 (m, 4 H), 2.06 (m, 2 H), 2.52 (m, 4H),
3.84 (s, 6 H), 3.91 (s, 6 H), 6.66 (s, 2 H), 6.72 (s, 2 H).
13C NMR (CDCl3): d = 28.58, 29.47, 33.24, 56.15, 56.17, 111.81,
112.32, 133.98, 134.51, 146.75, 148.40.
MS (70 eV): m/z = 342 [M+], 327, 270, 242, 214.
Tetra-tert-butyl-o-quaterphenyl (7)
Yield: 55%; colorless crystals; mp 252–254 °C (Lit.13a mp 254–
255 °C).
1H NMR (CDCl3): d = 1.00 (s, 18 H), 1.21 (s, 18 H), 6.91 (d, J = 8.5
Hz, 6 H), 7.10 (d, J = 8.2 Hz, 4 H), 7.19 (dd, J = 8.5, 2.0 Hz, 2 H),
7.25 (d, J = 8.2, 2.0 Hz, 2 H).
13C NMR (CDCl3): d = 31.30, 31.62, 34.42, 34.58, 123.81, 124.92,
129.40, 130.03, 130.40, 138.26, 138.82, 139.37, 148.87, 149.25.
MS (70 eV): m/z = 530 [M+], 516, 250, 57.
5,6,7,8,9,10-Hexahydro-2,3,12,13 tetramethoxydibenzo[a,c]cy-
clodecene (11e)
Yield: 26%; colorless, low-melting solid.
1H NMR (CDCl3): d = 0.72 (m, 2 H), 1.16 (m, 2 H), 1.38 (m, 2 H),
1.60 (m, 2 H), 2.46 (m, 2 H), 3.80 (s, 6 H), 3.90 (s, 6 H), 6.54 (s, 2
H), 6.73 (s, 2 H)
13C NMR (CDCl3): d = 220.97, 28.36, 29.16, 56.06, 56.11, 111.13,
113.13, 132.87, 134.85, 146.37, 148.53.
MS (70 eV): m/z = 356 [M+], 341, 325, 313, 299.
2,2¢-Di-tert-butyl-4,4¢,5,5¢-tetramethoxybiphenyl (8)
X-ray Crystal Structure Analyses of DAQ, BQ, and DQ22
All diffraction intensity data were collected with a Bruker Smart
Apex CCD diffractometer at 173(2) K using Cu-radiation (1.54178
Å). All structures were solved using direct methods, completed by
difference Fourier syntheses, and refined by full matrix least-
squares procedures. Crystallographic data, details for data collec-
tions, and refinement methods for each structure are summarized
below.
Yield: 25%; colorless crystals; mp 118–120 °C.
1H NMR (CDCl3): d = 1.16 (s, 18 H), 3.78 (s, 6 H), 3.91 (s, 6 H),
6.50 (s, 2 H), 6.98 (s, 2 H).
13C NMR (CDCl3): d = 33.39, 36.99, 55.96, 56.03, 111.65, 115.99,
134.68, 139.35, 145.03, 147.50.
MS (70 eV): m/z = 386 [M+], 306, 281, 258, 230.
2,2¢,6,6¢-Tetramethylbiphenyl (9)
DAQ
Yield: 70%; colorless crystals; mp 79–80 °C (Lit13a mp 79–80 °C).
Yellow crystals of DAQ were grown from a 1:9 mixture of EtOAc–
1H NMR (CDCl3): d = 2.32 (s, 12 H), 6.90 (s, 2 H), 6.98 (s, 4 H).
13C NMR (CDCl3): d = 24.07, 126.79, 128.22, 128.35, 138.46.
MS (70 eV): m/z = 210 [M+], 195, 180, 165, 89.
hexanes.
A
yellow-colored
crystal
with
dimensions
(0.12 × 0.12 × 0.08 mm3) was selected for data collection. Empiri-
cal formula C16H16O2; Formula weight 240.29; Crystal
system = triclinic; Space group P1; Z = 4; Unit cell dimensions
a = 6.08580(10) Å, b = 12.1696(3) Å, c = 16.5007(4) Å;
a = 106.9130(10)°, b = 94.3630(10)°, g = 90.2330(10)°; V =
1165.38(4) Å3; D (calculated) = 1.370 g cm–3; m = 0.706 mm–1. The
total number of reflections measured was 14333, of which 3856 re-
Synthesis 2008, No. 23, 3769–3774 © Thieme Stuttgart · New York

3774
R. Shukla, R. Rathore
PAPER
flections were symmetrically nonequivalent. Final residuals were
R1 = 0.0424 and wR2 = 0.0604 for 3856 reflections with I > 2s(I0).
(5) Miyake, Y.; Wu, M.; Rahman, M. J.; Kuwatani, Y.; Iyoda,
M. J. Org. Chem. 2006, 71, 6110.
(6) Krasovskiy, A.; Tishkov, A.; del Amo, V.; Mary, H.;
Knochel, P. Angew. Chem. Int. Ed. 2006, 45, 5010.
(7) (a) Surry, D. S.; Su, X.; Fox, D. J.; Franckevicius, V.;
Macdonald, S. J. F.; Spring, D. R. Angew. Chem. Int. Ed.
2005, 44, 1870. (b) Surry, D. S.; Fox, D. J.; Macdonald, S. J.
F.; Spring, D. R. Chem. Commun. 2005, 2589.
(8) Note that the only known method for the preparation of large
macrocycles containing tetramethoxybiaryl linkage requires
the usage of stoichiometric quantity of the high-molecular-
weight tetrakis(triphenylphosphine)nickel(0), see:
Semmelhack, M. F.; Helquist, P.; Lones, L. D.; Keller, L.;
Mendelson, L.; Ryono, L. S.; Smith, J. G.; Stauffer, R. D.
J. Am. Chem. Soc. 1981, 103, 6460.
BQ
Yellow crystals of BQ were grown from a mixture of CH2Cl2–ace-
tone. A yellow-colored crystal with dimensions (0.60 × 0.25 × 0.15
mm3) was selected for data collection. Empirical formula C28H40O2;
Formula weight 408.60; Crystal system = triclinic; Space group
P1; Z = 1; Unit cell dimensions a = 6.02230(10) Å, b = 10.2933(2)
Å, c = 10.3749(2) Å; a = 81.3820(10)°, b = 76.7550(10)°,
g = 80.7830(10)°; V = 613.64(2) Å3; D (calculated) = 1.106 g cm–3;
m = 0.514 mm–1. The total number of reflections measured was
5087, of which 2046 reflections were symmetrically nonequivalent.
Final residuals were R1 = 0.0348 and wR2 = 0.0361 for 2046 reflec-
tions with I > 2s(I0).
(9) Rathore, R.; Bosch, E.; Kochi, J. K. Tetrahedron Lett. 1994,
DQ
35, 1335.
Yellow crystals of DQ were grown from a mixture of CH2Cl2–
(10) Rathore, R.; Burns, C. L.; Deselnicu, M. I.; Denmark, S. E.;
Bui, T. Org. Synth. 2005, 82, 1.
MeOH.
A
yellow-colored
crystal
with
dimensions
(0.40 × 0.08 × 0.08 mm3) was selected for data collection. Empiri-
cal formula C10H12O2; Formula weight 164.20; Crystal
system = triclinic; Space group P1; Z = 2; Unit cell dimensions
a = 6.5151(6) Å, b = 8.6795(8) Å, c = 9.0471(8) Å;
a = 109.057(4)°, b = 109.368(4)°, g = 103.303(4)°; V = 422.07(7)
Å3; D (calculated) = 1.292 g cm–3; m = 0.718 mm–1. The total num-
ber of reflections measured was 6125, of which 1452 reflections
were symmetrically nonequivalent. Final residuals were
R1 = 0.0564 and wR2 = 0.0584 for 1452 reflections with I > 2s(I0).
(11) (a) Suga, K.; Maemura, K.; Fujihira, M.; Aoyagui, S. Bull.
Chem. Soc. Jpn. 1987, 60, 2221. (b) Bothner-By, A. A.
J. Am. Chem. Soc. 1951, 73, 4228.
(12) (a) Kumada, K. Pure Appl. Chem. 1980, 52, 669.
(b) Rathore, R.; Deselnicu, M. I.; Burns, C. L. J. Am. Chem.
Soc. 2002, 124, 14832.
(13) (a) Tashiro, M.; Yamato, T. J. Org. Chem. 1979, 44, 3037.
(b) Venkatraman, S.; Li, C.-J. Org. Lett. 1999, 1, 1133.
(c) Chen, C. Synlett 2000, 1491.
(14) (a) Hamamoto, H.; Anilkumar, G.; Tohma, H.; Kita, Y.
Chem. Eur. J. 2002, 8, 5377. (b) Kramer, B.; Averhoff, A.;
Waldvogel, S. R. Angew. Chem. Int. Ed. 2002, 41, 2981.
(15) Ronlan, A.; Parker, V. D. J. Org. Chem. 1974, 39, 1014.
(16) Haworth, R. D.; Lamberton, A. H. J. Chem. Soc. 1946, 1003.
(17) Fliedner, L. J. J. r.; Myers, M. J.; Schor, J. M.; Pachter, I. J.
J. Med. Chem. 1976, 19, 202.
Acknowledgment
We thank the National Science Foundation (CAREER Award) for
financial support and Dr. Sergey V. Lindeman (Marquette Univer-
sity) for X-ray crystallography.
(18) House, H. O. Acc. Chem. Res. 1976, 9, 59; and references
cited therein.
(19) The low-precision crystal structures of DQ and BQ at r.t. are
known, see CCDC database.
(20) Morgenstern A. P., Schuijt C., Nauta W. T.; J. Chem. Soc. C;
1971, 3706.
(21) Zweig, A.; Maurer, A. H.; Roberts, B. G. J. Org. Chem.
References
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(22) Crystallographic data (excluding structure factors) for the
structures reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre as supplementary
publication numbers CCDC-701965, 701966, and 701967.
Copies of the data can be obtained free of charge on appli-
cation to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK
[E-mail: deposit@ccdc.cam.ac.uk; Fax: +44(1223)336033
or via www.ccdc.cam.ac.uk/conts/retrieving.html].
Synthesis 2008, No. 23, 3769–3774 © Thieme Stuttgart · New York