An oxidative rearrangement of 6-phenylbicyclo[3.2.0]heptan-6-ol to 1,1′-biphenyl-carbaldehydes: A mechanistic study

Article abstract of DOI:10.1002/hlca.200890058

Acid-catalyzed rearrangement of 6-phenylbicyclo[3.2.0]heptan-6-ol gave 1,1′-biphenyl and 1,1′-biphenyl-carbaldehydes in small amounts as well as the expected rearrangement products. A detailed study of the reaction mechanism revealed that the conversion occurs via an oxidative process through the consecutive formation of cycloheptadienes, cycloheptatrienes, and 1,1′-biphenyls. The acid-catalyzed rearrangement of 6-phenylbicyclo[3.2.0] hept-2-en-6-ols gave 1- and 2-phenylcycloheptatrienes directly, from which 1,1′-biphenyl and 1,1′-biphenyl-carbaldehydes were obtained by oxidation.

Full text of DOI:10.1002/hlca.200890058

Helvetica Chimica Acta – Vol. 91 (2008)
559
An Oxidative Rearrangement of 6-Phenylbicyclo[3.2.0]heptan-6-ol to
1,1’-Biphenyl-Carbaldehydes: A Mechanistic Study
by Mustafa Ceylan*a), Esra Fındıka), and Hasan SeÅenb)
a) Department of Chemistry, Faculty of Arts and Sciences, Gaziosmanpas¸a University, TR-60110 Tokat
b) Department of Chemistry, Faculty of Arts and Sciences, Atatürk University, TR-25240 Erzurum
Acid-catalyzed rearrangement of 6-phenylbicyclo[3.2.0]heptan-6-ol gave 1,1’-biphenyl and 1,1’-
biphenyl-carbaldehydes in small amounts as well as the expected rearrangement products. A detailed
study of the reaction mechanism revealed that the conversion occurs via an oxidative process through the
consecutive formation of cycloheptadienes, cycloheptatrienes, and 1,1’-biphenyls. The acid-catalyzed
rearrangement of 6-phenylbicyclo[3.2.0]hept-2-en-6-ols gave 1- and 2-phenylcycloheptatrienes directly,
from which 1,1’-biphenyl and 1,1’-biphenyl-carbaldehydes were obtained by oxidation.
Introduction. – As known, a common way of generating alkenes is acid-catalyzed
dehydration of alcohols. In general, many of the dehydration reactions produce
alkenes. On the other hand, during dehydration reactions, further rearrangements may
occur to give more stabilized carbocations, and such cascade rearrangements are found
in the synthesis of biological molecules such as terpenes [1].
In our previous studies, we synthesized some strained cyclic allenes and used many
cyclic alkenes produced by the acid-catalyzed dehydration of alcohols [2]. Recently,
Algi and Balci [3] prepared 6-phenylbicyclo[3.2.0]hept-6-ene (2) by dehydration of 6-
phenylbicyclo[3.2.0]heptan-6-ol (1) (Scheme 1), from which they synthesized many
fluoro- or bromo-substituted indane derivatives by the addition of halocarbenes.
Scheme 1
In our ongoing project on strained allenes, we required alkene 2. For the acid-
catalyzed dehydration of 1, without using a Dean – Stark trap to remove the formed
H2O when we refluxed 1 in benzene in the presence of TsOH, we saw surprising results
and isolated many rearranged products. In this paper, we present the products and
discuss their formation mechanisms.
Results and Discussion. – We performed the dehydration of 1 in the presence of
TsOH in refluxing benzene (ca. 808). The carbocationic rearrangement of 1, followed
by chromatography, gave eight products together with unreacted 1: 6-phenybicy-
clo[3.2.0]hept-6-ene (2), 1-phenylbicyclo[4.1.0]hept-2-ene (3), 2-phenylcyclohepta-
ꢀ 2008 Verlag Helvetica Chimica Acta AG, Zürich

560
Helvetica Chimica Acta – Vol. 91 (2008)
1,3-diene (4), 2-phenylcyclohepta-1,4-diene (5), 3-phenylcyclohept-3-en-1-yl 4-meth-
ylbenzenesulfonate (6), 3-phenylcyclohept-3-en-1-ol (7), 1,1’-biphenyl (8), and 1,1’-
biphenyl-2-carbaldehyde (9) (Scheme 2).
Scheme 2
The structures of the products were determined on the basis of spectral data and
their comparison with published data. As compounds 2 [3], 3 [3], 4 [4], 5 [5], 6 [6], 7
[6], 8 [7], and 9 [8] are known in the literature, they were readily identified. In addition,
the structure of tosylate 6 was confirmed via its chemical transformation by treatment
t
with BuOK to afford the 1,3-diene 4.
The formation of compounds 2 – 7 may be explained as shown in Scheme 3.
Protonation of 1 gives (6-phenylbicyclo[3.2.0]hept-6-yl)onium (10), which converts to
carbocation 11 by loss of H2O. Deprotonation at C(7) in 11 gives alkene 2. Cations 13
and 14 are formed by the ring-opening of 11. Deprotonation of 15 affords alkene 3.
Deprotonation at C(3) or C(5) of cation 12 yields dienes 4 and 5, respectively. In
addition, carbocation 12 can undergo nucleophilic attack by TsOH to give tosylate 6 or
by H2O to yield alcohol 7.
The formation of compounds 8 and 9 may be explained as shown in Scheme 4. We
assume that the 1-phenylcyclohepta-1,3,5-triene (16) is formed by dehydrogenation of
1,3-dienes 4 and/or 5 in the reaction medium or during chromatography. In a previous
study, Manukov and Bazhina [9] reported the auto-oxidation of 1,4,4- and 1,5,5-
trimethylcyclohept-1-enes. We assume that cycloheptatriene systems may be auto-
oxidized as cycloheptene systems because of the presence of the more conjugated
double bonds and allylic CH2 unit. Thus, an insertion of O2 into an allylic HꢀC bond of
1-phenylcyclohepta-1,3,5-triene (16) may yield hydroperoxide 17. It is well known that
the cycloheptatriene unit is in equilibrium with its valence isomer norcaradiene [10].
The cyclopropane ring in the norcaradiene 18 may be cleaved in two different ways, a
and b. In the case of Path a, the intermediate 19 is formed, and removal of HCHO gives
1,1’-biphenyl (8). The intermediate 20 formed in the case of Path b converts to
intermediate 21 by deprotonation. Removal of H2O from 21 yields biphenyl-2-
carbaldehyde (9).

Helvetica Chimica Acta – Vol. 91 (2008)
561
Scheme 3
Scheme 4

562
Helvetica Chimica Acta – Vol. 91 (2008)
To reveal the role of air O2, 2-phenylcyclohepta-1,3-diene (4) was treated with silica
gel. While a solution of 4 in benzene and/or hexane in the presence of silica gel under
N2 did not show any change, the similar mixture of 4 under air O2 started to decompose
after one week. From these experiments, we concluded that auto-oxidation of the
cycloheptadiene systems is possible.
To gain more insight into the reaction mechanism and to explain the formation of
biaryl systems, we decided to synthesize and oxidize 1-phenylcyclohepta-1,3,5-triene
(16) itself. The addition of PhMgBr to 22 afforded 6-phenylbicyclo[3.2.0]hept-2-en-6-ol
(23) (Scheme 5). The acid-catalyzed dehydration of alcohol 23 with TsOH in benzene
at reflux temperature (ca. 808) resulted in the formation of 1-phenylcyclohepta-1,3,5-
triene (16) and 2-phenylcyclohepta-1,3,5-triene (24) in a ratio of 1:2, which was
1
determined from the H-NMRspectrum of the mixture ( Scheme 5).
Scheme 5
Without separation, the structures of 16 and 24 were determined on the basis of
spectral data and comparison with published data [11]. We determined that the mixture
converts to the carbaldehydes 9, 25, and 26 on being exposed to air O2 without solvent
for ca. 7 days. The 1H-NMR(400 MHz) spectrum of the product mixtures shows three
aldehyde signals: 10.09, 10.06, and 9.92 ppm. The mixture was submitted to silica gel
column chromatography and was separated into four known products: 1-phenyl-
cyclohepta-1,3,5-triene (16) [11], 1,1’-biphenyl-2-carbaldehyde (9) [8], 1,1’-biphenyl-3-
carbaldehyde (25) [12], and 1,1’-biphenyl-4-carbaldehyde (26) [13]. In addition,
oxidation of the mixture of 16 and 24 with CrO3/pyridine in CH2Cl2 at 08 gave four
products: 1,1’-biphenyl (8), 1,1’-biphenyl-2-carbaldehyde (9), 1,1’-biphenyl-3-carbal-
dehyde (25) and 1,1’-biphenyl-4-carbaldehyde (26) (Scheme 5). The mixture of
products was separated by silica gel column chromatography.
In a previous study, Nee et al. [14], investigated elimination reactions of 6-
bicyclo[3.2.0]hept-2-enyl tosylates, and reported their conversion to cycloheptatrienes
by hydrolysis. The formation of compounds 16 and 24 may be explained by a similar
mechanism as shown in Scheme 6. Protonation of 23 gives (6-phenylbicyclo[3.2.0]hept-
2-en-6-yl)oxonium (27), which converts to carbocation 28 by loss of H2O. Carbocation
28 is rearranged to cycloheptadienyl carbocation 29, which is an allylic carbocation.

Helvetica Chimica Acta – Vol. 91 (2008)
563
Scheme 6
While deprotonation at C(3) gives 2-phenylcyclohepta-1,3,5-triene (24), deprotonation
at C(7) leads to 1-phenylcyclohepta-1,3,5-triene (16) (Scheme 6).
ˇ
Müller and Rocek [15] previously investigated the mechanism of chromic acid
oxidation of cycloheptatriene. Recently, Celik et al. [16] synthesized diols using
phenyliodine(III) bis(trifluoroacetate) and reported the smooth formation of benzal-
dehyde from the oxidation of cycloheptatriene. The formation of compounds 9 and 25
can be explained by a similar mechanism as shown in Scheme 7. The chromate (or
hydroperoxide) 30 is in equilibrium with its valence isomer norcaradiene 31, which
converts to 25 via intermediate 32 (Scheme 7, Path a). In a similar way, Path b gives 1,1’-
biphenyl-2-carbaldehyde (9).
Scheme 7
It is well known that in many allylic oxidations with Cr(VI) reagents, an ꢁallylic
shiftꢂ occurs during the oxidation [17]. The formation of 1,1’-biphenyl-4-carbaldehyde
(26) may be explained by a similar process. The chromate (or hydroperoxide)
derivative 30 undergoes an allylic shift to form chromate 33, which is in equilibrium
with its valence isomer norcaradiene 34. The norcaradiene isomer 34 yields 1,1’-
biphenyl-4-carbaldehyde (26) via intermediate 35 (Path a). In a similar way,
intermediate 32 may convert to 1,1’-biphenyl-3-carbaldehyde (25; Path b, Scheme 8).

564
Helvetica Chimica Acta – Vol. 91 (2008)
Scheme 8
We wondered how the conversion proceeds in another phenyl-substituted cyclo-
heptatriene system. Therefore, we prepared 2-(4-methoxyphenyl)- [18] and 1-(4-
methoxyphenyl)cyclohepta-1,3,5-triene (37 and 38, resp.) [18] by acid-catalyzed
rearrangement of 36. Without separation, the structures of 37 and 38 were elucidated
on the basis of spectral data given in the literature [18]. We determined that compound
37 converts to the carbaldehydes 40 – 42 with the effect of air O2 within ca. 10 days. In a
similar way, oxidation of the mixture of 37 and 38 with CrO3/pyridine in CH2Cl2 gave 4-
methoxy-1,1’-biphenyl (39) [7], and the known carbaldehydes 4’-methoxy-1,1’-biphen-
yl-2-carbaldehyde (40) [8][19], 4’-methoxy-1,1’-biphenyl-3-carbaldehyde (41) [20], and
4’-methoxy-1,1’-biphenyl-4-carbaldehyde (42) [21] (Scheme 9).
Scheme 9

Helvetica Chimica Acta – Vol. 91 (2008)
565
Conclusions. – In this paper, we elucidated the formation mechanism of 1,1’-
biphenyls and 1,1’-biphenyl-carbaldehydes from the acid-catalyzed rearrangement of
6-phenylbicyclo[3.2.0]heptan-6-ol and 6-phenylbicyclo[3.2.0]hept-2-en-6-ol. More-
over, for the first time we described an alternative synthetic method for the preparation
of 1- and 2-phenylcyclohepta-1,3,5-triene by acid-catalyzed rearrangement of 6-
arylbicyclo[3.2.0]hept-2-en-6-ols.
Experimental Part
General. cis-Bicyclo[3.2.0]hept-2-en-6-one was purchased from Merck. Column chromatography
(CC): silica gel (60 – 230 mesh, Merck). M.p.: Electrothermal 9100 apparatus. IRSpectra: Jasco FT/IR-
430 spectrometer; n˜ in cmꢀ1 1H- and 13C-NMRspectra: Varian Mercury-400 and Bruker AC-400
.
instruments; as internal standards Me4Si (d 0.00) for 1H-NMRand CDCl (d 77.0) for 13C-NMR
3
spectroscopy; d in ppm, J in Hz. Elemental analyses: LECO CHNS 932 elemental analyzer.
6-Phenylbicyclo[3.2.0]heptan-6-ol (1). The alcohol 1 was prepared as described in [22]. Yield 77%.
Colorless liquid [6]. IR(film on KBr): 3421, 3058, 3027, 2948, 2852, 1646, 1635, 1446, 1132, 1068. 1H-NMR
(400 MHz, CDCl3): 7.52 – 7.50 (m, 2 arom. H); 7.35 – 7.32 (m, 2 arom. H); 7.24 – 7.20 (m, 1 arom. H); 2.94 –
2.90 (m, HꢀC(5)); 2.64 – 2.58 (m, 2 H); 2.08 – 2.05 (m, CH, OH); 1.96 – 1.76 (m, 3 H); 1.60 – 1.49 (m,
3 H). 13C-NMR(100 MHz, CDCl 3): 149.2; 128.4; 126.6; 124.4; 72.8; 51.0; 41.6; 32.8; 31.4; 26.8; 26.0. 1H-
and 13C-NMRspectra are in good agreement with the data given in [6].
Rearrangement of 6-Phenylbicyclo[3.2.0]heptan-6-ol (1) in the Presence of TsOH. To a stirred soln.
of 1 (4.30 g, 22.8 mmol) in 50 ml of benzene was added 4-methylbenzenesulfonic acid (TsOH) (0.30 g,
1.7 mmol), followed by refluxing for 3 h. The mixture was washed with H2O (3 ꢁ 30 ml) and dried
(Na2SO4). The solvent was evaporated, and the residue was chromatographed on silica gel, eluting with
hexane. The products are listed in the order of fractions from CC.
1,1’-Biphenyl (8). 0.10 g (3%). Needles. M.p. 69 – 718 ([7]: 68 – 718). IR(KBr): 3056, 3031, 2927,
1
1479, 1427. H-NMR(400 MHz, CDCl ): 7.55 – 7.52 (br. d, J ¼ 7.3, 4 H); 7.40 – 7.36 (br. t, J ¼ 7.3, 4 H);
3
7.31 – 7.27 (br. t, J ¼ 7.3, 2 H). 13C-NMR(100 MHz, CDCl 3): 141.2; 128.8; 127.2; 127.2. 1H- and 13C-NMR
spectra are in good agreement with the data given in [7].
6-Phenylbicyclo[3.2.0]hept-6-ene (2) [3]. 0.35 g (9%). Colorless liquid. IR(KBr): 3062, 2956, 2871,
1683, 1637, 1448. 1H-NMR(400 MHz, CDCl 3): 7.19 – 7.09 (m, 5 arom. H); 5.96 (m, 1 olefinic H); 3.35 –
3.33 (m, HꢀC(5)); 3.00 – 2.98 (m, HꢀC(1)); 1.65 – 1.12 (m, 6 H). 13C-NMR(100 MHz, CDCl ): 146.3;
3
134.2; 128.6; 128.1; 127.5; 124.9; 46.3; 44.1; 26.9; 26.4; 23.9. 1H- and 13C-NMRspectra are in good
agreement with the data given in [3].
3-Phenylcyclohept-3-en-1-yl 4-Methylbenzenesulfonate (6) [6]. 0.30 g (4%). Colorless crystals.
M.p. 42 – 438. IR(KBr): 3077, 3023, 2940, 2856, 1594, 1353, 1189, 1174, 1095, 902, 763, 665, 557. 1H-NMR
(400 MHz, CDCl3): 7.76 – 7.74 (br. d, J ¼ 7.3, AA’ part of AA’BB’ system, 2 arom. H); 7.26 – 7.24 (br. d, J ¼
7.3, BB’ part of AA’BB’ system, 2 arom. H); 7.18 – 7.16 (m, 3 arom. H); 7.04 – 7.02 (m, 2 arom. H); 6.13 (br.
t, J ¼ 6.9, 1 olefinic H); 4.49 – 4.42 (ddt, J ¼ 10.3, 3.7, 1.9, HꢀC(1)); 2.93 – 2.87 (dd, J ¼ 14.2, 11.2, A part of
AB system, 1 H of CH2(2)); 2.73 – 2.70 (br. d, J ¼ 14.2, B part of AB system, 1 H of CH2(2)); 2.32 (s, Me);
2.29 – 2.08 (m, 3 H); 1.98 – 1.85 (m, 1 H); 1.75 – 1.68 (m, 1 H); 1.44 – 1.32 (m, 1 H). 13C-NMR(100 MHz,
CDCl3): 144.6; 143.2; 137.4; 134.2; 132.6; 129.8; 128.2; 127.8; 126.8; 125.6; 80.2; 38.8; 38.6; 27.6; 24.0; 21.8.
1H- and 13C-NMRspectra are in good agreement with the data given in [6].
2-Phenylcyclohepta-1,3-diene (4) [4]. 0.16 g (4%). Colorless liquid. IR(film on KBr): 3052, 2920,
1
2849, 1655, 1628, 1540, 1479, 1455, 720, 676. H-NMR(400 MHz, CDCl 3): 7.42 – 7.25 (m, 4 arom. H);
7.24 – 7.18 (m, 1 H); 6.15 (t, J ¼ 6.3, 1 H); 6.10 – 6.01 (m, 2 H); 2.32 – 2.27 (m, 2 H); 2.27 – 2.16 (m, 2 H);
1.64 – 1.54 (m, 2 H). 13C-NMR(100 MHz, CDCl 3): 141.2; 137.8; 133.8; 128.8; 128.4; 128.2; 126.8; 126.6;
30.2; 30.0; 29.6. 1H- and 13C-NMRspectra are in good agreement with the data given in [4].
2-Phenylcyclohepta-1,4-diene (5) [5]. 0.12 g (3%). Colorless liquid. IR(film on KBr): 3054, 2923,
2852, 1652, 1635, 1558, 1488, 1457, 750, 696. 1H-NMR(400 MHz, CDCl 3): 7.37 – 7.24 (m, 5 arom. H); 6.09
(t, J ¼ 6.8, HꢀC(1)); 5.73 – 5.69 (m, HꢀC(4), HꢀC(5)); 3.29 – 3.23 (br. d, J ¼ 4.0, 2 H); 2.48 (dd, J ¼ 12.6,

566
Helvetica Chimica Acta – Vol. 91 (2008)
6.8, 2 H); 2.28 – 2.23 (m, 2 H). 13C-NMR(100 MHz, CDCl 3): 138.9; 131.2; 128.9; 128.6; 127.4; 127.0;
126.6; 126.0; 30.9; 29.9; 26.4.
1-Phenylbicyclo[4.1.0]hept-2-ene (3) [3]. 80 mg (2%). Colorless liquid. IR(film on KBr): 3060, 2928,
2860, 1657, 1639, 1560, 1488, 1457, 755, 698. 1H-NMR(400 MHz, CDCl 3): 7.24 – 7.18 (m, 4 arom. H); 7.15 –
7.05 (m, 1 arom. H); 6.06 (dd, J ¼ 10.0, 2.1, HꢀC(2)); 5.48 (ddd, J ¼ 10.0, 6.7, 2.1, HꢀC(3)); 2.10 – 1.99 (m,
2 H); 1.82 – 1.70 (m, 2 H); 1.50 – 1.44 (m, 1 H); 1.27 (dd, J ¼ 8.7, 4.9, HꢀC(7)); 1.10 – 1.06 (br. t, J ¼ 4.9,
1 H). 13C-NMR(100 MHz, CDCl 3): 146.8; 133.6; 128.8; 127.4; 126.1; 123.3; 25.7; 24.4; 20.8; 19.5; 18.6. 1H-
and 13C-NMRspectra are in good agreement with the data given in the literature [3].
The elution in CC was continued with hexane/CHCl3 7:3.
3-Phenylcyclohept-3-en-1-ol (7) [6]. 215 mg (5%). Colorless crystals. M.p. 63 – 648 ([6]: 798). IR
(KBr): 3380, 3073, 3027, 2921, 2836, 1596, 1457, 1440, 1307, 1029, 852, 755, 698. 1H-NMR(400 MHz,
CDCl3): 7.33 – 7.29 (m, 2 arom. H); 7.27 – 7.24 (m, 2 arom. H); 7.21 – 7.15 (m, 1 arom. H); 6.17 (t, J ¼ 6.9, 1
olefinic H); 3.81 (ddt, J ¼ 8.9, 3.3, 2.2, HꢀC(1)); 2.87 (dd, J ¼ 14.5, 9.2, A part of AB system, 1 H of
CH2(2)); 2.78 (dt, J ¼ 14.5, 1.8, B part of AB system, 1 H of CH2(2)); 2.25 – 2.19 (m, 2 H); 2.12 – 2.06 (m,
1 H); 1.84 – 1.77 (m, 1 H); 1.76 – 1.64 (m, 1 H); 1.60 (br. s, ꢀOH, 1 H); 1.48 – 1.43 (m, 1 H). 13C-NMR
(100 MHz, CDCl3): 144.4; 138.8; 132.0; 128.2; 126.6; 125.8; 68.4; 41.4; 41.2; 28.2; 23.4. 1H- and 13C-NMR
spectra are in good agreement with the data given in [6].
1,1’-Biphenyl-2-carbaldehyde (9) [8]. 80 mg (2%). Viscous oil. IR(film on KBr): 3060, 3027, 2923,
2850, 1473, 1454, 1691. 1H-NMR(400 MHz, CDCl 3): 9.92 (d, J ¼ 0.7, CHO); 7.96 (dd, J ¼ 7.8, 1.04, 1 H);
7.58 (dt, J ¼ 7.8, 1.4, 1 H); 7.45 – 7.30 (m, 7 H). 13C-NMR(100 MHz, CDCl ): 192.4; 146.0; 137.8; 133.8;
3
133.6; 130.8; 130.0; 128.4; 128.2; 127.8; 127.6. 1H- and 13C-NMRspectra are in good agreement with the
data given in [8].
The last fraction of CC contained unreacted starting material, alcohol 1 [3] (2.50 g).
6-Phenylbicyclo[3.2.0]hept-2-en-6-ol (23). To a stirred soln. of Mg (0.6 g, 25 mmol) in 25 ml of dry
THF at r.t. was added bromobenzene (a few drops) and a small amount of I2, and the mixture was stirred
at a bath temp. of 658. To this mixture, bromobenzene (3.14 g, 20 mmol) in 5 ml of THF was added
during 1 h, and stirring was continued for 1 h at the same temp. The mixture was cooled to r.t., and
bicyclo[3.2.0]hept-2-en-6-one (22) (1.5 g, 13 mmol) in 5 ml of THF was added, followed by stirring for
3 h. The mixture was extracted with Et2O (2 ꢁ 50 ml). The combined org. extracts were washed with H2O
(100 ml) and dried (MgSO4). Evaporation of the solvent (308/20 Torr) gave 23 as a yellowish liquid.
2.40 g (93%). IR(film on KBr): 3459, 3048, 2921, 2850, 1604, 1594, 1494, 1446, 1348, 1228, 1070, 730, 700.
1H-NMR(400 MHz, CDCl 3): 7.42 – 7.39 (m, 2 arom. H); 7.32 – 7.28 (m, 2 arom. H); 7.20 – 7.16 (m, 2 arom.
H); 5.92 – 5.88 (m, 2 olefinic H); 3.33 – 3.28 (br. t, J ¼ 7.6, HꢀC(5)); 3.16 – 3.12 (m, HꢀC(1)); 2.93 – 2.87
(ddd, J ¼ 12.3, 8.2, 0.9, HexoꢀC(4)); 2.81 – 2.75 (ddd, J ¼ 18.1, 3.5, 1.8, HendoꢀC(7)); 2.48 – 2.41 (ddd, J ¼
18.1, 8.7, 1.6, HexoꢀC(7)); 2.02 – 1.99 (ddd, J ¼ 12.3, 3.4, 0.9, HendoꢀC(4)); 1.60 (br. s, OH). 13C-NMR
(100 MHz, CDCl3): 147.4; 135.6; 132.9; 128.4; 126.8; 124.8; 76.8; 48.0; 44.6; 39.6; 32.9. Anal. calc. for
C13H14O: C 83.83, H 7.58; found: C 83.79, H 7.60.
Rearrangement of 6-Phenylbicyclo[3.2.0]hept-2-en-6-ol (23) in the Presence of TsOH. The
procedure described for 1 was applied to 23 to afford 1-phenylcyclohepta-1,3,5-triene (16) and 2-
phenylcyclohepta-1,3,5-triene (24) in a ratio of 1:2 (total yield 76%). At this stage, the mixture could not
be separated. After the mixture was exposed to air O2 for 7 d, CC (30 g) eluting with hexane gave 16,
along with the oxidized products 9, 25, and 26.
Data of 16 [23]. Colorless liquid. IR(film on KBr): 3056, 3027, 2971, 2931, 2886, 1598, 1482, 1446,
1159, 1031, 1008, 759, 738, 698. 1H-NMR(400 MHz, CDCl 3): 7.54 – 7.52 (m, 2 arom. H); 7.45 – 7.36 (m, 3
arom. H); 6.67 (dd, J ¼ 11.1, 5.9, A part of AB system, HꢀC(3)); 6.58 (dd, J ¼ 11.1, 5.4, B part of AB
system, HꢀC(4)); 6.43 (d, J ¼ 5.9, HꢀC(2)); 6.20 (dd, J ¼ 9.2, 5.4, HꢀC(5)); 5.42 (dd, J ¼ 9.2, 7.1,
HꢀC(6)); 2.71 – 2.69 (d, J ¼ 7.1, CH2(7)). 13C-NMR(100 MHz, CDCl 3): 141.2; 133.2; 130.8; 130.2; 128.4;
127.4; 127.2; 127.0; 122.8; 121.0; 31.6. 1H- and 13C-NMRspectra are in good agreement with the data given
in [23].
Oxidation of 1-Phenylcyclohepta-1,3,5-triene (16) and 2-Phenylcyclohepta-1,3,5-triene (24) with
CrO3/Pyridine. To a magnetically stirred soln. of CrO3 (2.73 g, 27 mmol) in 20 ml of pyridine and 15 ml of
CH2Cl2 cooled to 08 was added dropwise a soln. of the mixture of 16 and 24 (0.70 g, 4.2 mmol; ratio 16/24
1:2, see above and Scheme 5) in 5 ml of CH2Cl2 over 5 min. This soln. was stirred for 2 h at the same

Helvetica Chimica Acta – Vol. 91 (2008)
567
temp. and for an additional 6 h at r.t. The solvent (pyridine and CH2Cl2) was removed under reduced
pressure. To the residue, 50 ml of CH2Cl2 was added and filtered to remove precipitated material. The
extract was washed with 1m HCl soln. (10 ml) and H2O (10 ml), and dried (MgSO4). The solvent was
evaporated, and the residue was submitted to CC (60 g) eluting with hexane/CHCl3 8 :2. The reaction
products are described in the order of the CC fractions.
1,1’-Biphenyl (8) [7]. 0.20 g (31%).
1,1’-Biphenyl-2-carbaldehyde (9) [8]. 190 mg (25%). Viscous oil.
1,1’-Biphenyl-3-carbaldehyde (25) [12]. 110 mg (15%). M.p. 44 – 468 ([12]: Viscous oil). IR(film on
KBr): 3060, 2848, 2751, 1473, 1454, 1691. 1H-NMR(400 MHz, CDCl 3): 10.09 (s, CHO); 8.37 (s, HꢀC(2));
8.11 – 8.10 (m, HꢀC(5)); 7.65 – 7.39 (m, 6 H). 13C-NMR(100 MHz, CDCl ): 192.6; 142.4; 141.8; 140.2;
3
133.4; 129.8; 129.1; 128.8; 128.2; 128.1; 127.4. 1H- and 13C-NMRspectra are in good agreement with the
data given in the literature [12].
1,1’-Biphenyl-4-carbaldehyde (26) [13]. 90 mg (12%). Colorless crystals. M.p. 57 – 598 ([24]: 58 –
598). IR(KBr): 3031, 2825, 2732, 1486, 1450, 1698. 1H-NMR(400 MHz, CDCl ): 10.06 (s, CHO); 8.06
3
(d, J ¼ 8.1, 2 H); 7.96 (d, J ¼ 8.1, 2 H); 7.76 (d, J ¼ 7.4, 2 H); 7.55 (t, J ¼ 7.4, 2 H); 7.50 – 7.45 (t, J ¼ 7.4, 1 H).
13C-NMR(100 MHz, CDCl 3): 193.5; 146.7; 139.6; 135.9; 131.0; 129.9; 129.4; 128.2; 127.9. 1H- and
13C-NMRspectra are in good agreement with the data given in the literature [13].
6-(4-Methoxyphenyl)bicyclo[3.2.0]hept-2-en-6-ol (36). The procedure described for the preparation
of 23 was applied by using 4-methoxyphenyl bromide to afford 36 in a yield of 86% (yellowish liquid).
IR(film on KBr): 3480, 3046, 2958, 2931, 2836, 1610, 1511, 1488, 1247, 1178, 1031, 827, 727, 601. 1H-NMR
(400 MHz, CDCl3): 7.41, 6.92 (AA’BB’ system, J ¼ 8.7, 4 arom. H); 5.98 (m, 2 olefinic H); 3.84 (s, MeO);
3.38 – 3.36 (br. t, J ¼ 7.6, HꢀC(5)); 3.26 – 3.17 (m, HꢀC(1)); 2.93 – 2.96 (ddd, J ¼ 11.9, 8.2, 0.8,
HexoꢀC(4)); 2.94 – 2.84 (ddd, J ¼ 18.1, 1.8, HendoꢀC(7)); 2.57 – 2.54 (ddd, J ¼ 18.1, 8.7, 1.8, HexoꢀC(7));
2.12 – 2.07 (ddd, J ¼ 11.9, 3.4, 0.8, HendoꢀC(4)); 1.60 (br. s, OH). 13C-NMR(100 MHz, CDCl 3): 158.2;
139.8; 135.6; 132.9; 126.0; 113.6; 76.4; 55.4; 47.8; 44.4; 39.6; 32.9. Anal. calc. for C14H16O2: C 77.75, H 7.46;
found: C 77.78, H 7.43.
Rearrangement of 6-Phenylbicyclo[3.2.0]hept-2-en-6-ol (36) in the Presence of TsOH. The reaction
was performed as described for 1 to give 2-(4-methoxyphenyl)cyclohepta-1,3,5-triene (37) [18] and 1-(4-
methoxyphenyl)cyclohepta-1,3,5-triene (38) [18] in a ratio of 1:1.5 (total yield 54%). At this stage, the
mixture could not be separated. After the mixture was exposed to air O2 for 7 d, CC eluting with hexane
gave (38), along with the oxidized products 40 – 42.
Data of 38 [18]. Colorless solid. M.p. 588. IR(KBr): 3004, 2956, 2933, 2906, 2834, 1604, 1508, 1488,
1284, 1247, 1180, 1037, 829, 705. 1H-NMR(400 MHz, CDCl 3): 7.53, 6.95 (AA’BB’ system, J ¼ 8.8, 4 arom.
H); 6.78 (dd, J ¼ 11.0, 6.0, A part of AB system, HꢀC(3)); 6.68 (dd, J ¼ 11.0, 5.5, B part of AB system,
HꢀC(4)); 6.52 (d, J ¼ 6.0, HꢀC(2)); 6.36 (dd, J ¼ 9.2, 5.5, HꢀC(5)); 5.53 (dd, J ¼ 9.2, 7.2, HꢀC(6)); 3.87
(s, MeO); 2.84 (d, J ¼ 7.2, CH2(7)). 13C-NMR(100 MHz, CDCl 3): 159.1; 133.6; 132.4; 131.1; 129.6; 128.8;
127.1; 121.4; 120.67; 113.8; 55.4; 31.6. 1H- and 13C-NMRspectra are in good agreement with the data given
in [18].
Oxidation of 37 and 38 with CrO3/Pyridine. The procedure described for the oxidation of the mixture
16/24 was applied to the mixture 37/38. The mixture was submitted to CC eluting with hexane/CHCl3 8 :2.
The reaction products are listed in the order of the fractions of CC.
4-Methoxy-1,1’-biphenyl (39) [7]. 33%. Needles. M.p. 85 – 888 ([25]: 868). IR(KBr): 3031, 3000,
2960, 2935, 2834, 1288, 1270, 1249, 833, 688. 1H-NMR(400 MHz, CDCl 3): 7.58 – 7.53 (m, 4 H); 7.45 – 7.41
(br. t, J ¼ 7.3, 2 H); 7.34 – 7.32 (br. t, J ¼ 7.3, 1 H); 7.01 – 6.98 (dt, J ¼ 9.15, 2.2, 2 H); 3.86 (s, MeO).
13C-NMR(100 MHz, CDCl 3): 159.4; 141.1; 134.0; 128.9; 128.4; 127.0; 126.9; 114.4; 55.6. 1H- and
13C-NMRspectra are in good agreement with the data given in [7].
4’-Methoxy-1,1’-biphenyl-2-carbaldehyde (40) [8][19]. 21%. Needles. M.p. 39 – 428 ([19]: colorless
oil). IR(KBr): 3068, 3029, 2956, 2939, 2908, 2838, 1685, 1598, 1295, 1251, 1184, 1031, 819, 698. 1H-NMR
(400 MHz, CDCl3): 9.99 (s, CHO); 8.01 – 7.99 (br. d, J ¼ 7.7, H ꢀC(3)); 7.63 – 7.59 (dt, J ¼ 7.7, 1.1,
HꢀC(5)); 7.47 – 7.42 (m, HꢀC(6)); 7.31 – 7.29 (m, HꢀC(4)); 7.26 – 7.25 (br. d, J ¼ 8.6, AA’ part of AA’BB’
system, HꢀC(2’), HꢀC(6’)); 7.02 – 7.00 (br. d, J ¼ 8.6, BB’ part of AA’BB’ system, HꢀC(3’), HꢀC(5’));
3.86 (s, MeO). 13C-NMR(100 MHz, CDCl 3): 192.9; 159.9; 145.8; 133.9; 133.8; 131.6; 131.1; 130.2; 127.8;
127.6; 114.2; 55.6. 1H- and 13C-NMRspectra are in good agreement with the data given in [8].

568
Helvetica Chimica Acta – Vol. 91 (2008)
4’-Methoxy-1,1’-biphenyl-4-carbaldehyde (42) [21]. 130 mg (13%). Colorless crystals. M.p. 81 – 848
([21]: 104 – 1068). IR(KBr): 3002, 2956, 2927, 2852, 2834, 1606, 1508, 1488, 1245, 1180, 1033, 831, 759, 701.
1H-NMR(400 MHz, CDCl 3): 10.03 (s, CHO); 7.93 – 7.91 (br. d, J ¼ 8.2, AA’ part of AA’BB’ system,
HꢀC(3), HꢀC(5)); 7.72 – 7.70 (br. d, J ¼ 8.2, BB’ part of AA’BB’ system, HꢀC(2), HꢀC(6)); 7.60 – 7.58
(br. d, J ¼ 8.6, AA’ part of AA’BB’ system, HꢀC(2’), HꢀC(6’)); 7.02 – 6.99 (br. d, J ¼ 8.6, BB’ part of
AA’BB’ system, HꢀC(3’), HꢀC(5’)); 3.87 (s, MeO). 13C-NMR(100 MHz, CDCl 3): 192.2; 160.4; 147.0;
134.9; 132.4; 130.6; 128.8; 127.2; 114.8; 55.6. The 1H-NMRspectrum is in good agreement with the data
given in [21].
4’-Methoxy-1,1’-biphenyl-3-carbaldehyde (41) [20]. 70 mg (7%). Colorless crystals. M.p. 50 – 538
([20]: 528). IR(KBr): 3027, 2964, 2940, 2910, 2840, 1681, 1598, 1295, 1257, 1186, 819, 698. 1H-NMR
(400 MHz, CDCl3): 10.08 (s, CHO); 8.06 (s, HꢀC(2)); 7.83 – 7.80 (m, HꢀC(4), HꢀC(6)); 7.69 (t, J ¼ 8.4,
HꢀC(5)); 7.58 – 7.56 (br. d, J ¼ 8.6, AA’ part of AA’BB’ system, HꢀC(2’), HꢀC(6’)); 7.02 – 7.00 (br. d,
J ¼ 8.6, BB’ part of AA’BB’ system, HꢀC(3’), HꢀC(5’)); 3.87 (s, MeO). 13C-NMR(100 MHz, CDCl 3):
192.6; 160.6; 144.8; 132.8; 132.4; 129.6; 128.4; 128.4; 127.8; 114.6; 55.6. The 1H-NMRspectrum is in
agreement with the data given in the literature [20].
The authors are indebted to Gaziosmanpasa University (Grant BAP-2003-39) for its financial
support of this work.
REFERENCES
[1] L. M. Harwood, ꢁPolar Rearrangementsꢂ, Oxford Science Publications, New York, 1995, pp. 18.
[2] M. Ceylan, Y. Budak, M. Ulukaya, M. B. Gurdere, E. Findik, Turk. J. Chem. 2006, 30, 663, and refs.
cit. therein.
[3] F. Algi, M. Balci, Arkivoc 2006, Part 10, 173.
[4] A. A. Kulkarni, S. T. Diver, Org. Lett. 2003, 5, 3463.
[5] Q. Yao, Org. Lett. 2002, 4, 427.
[6] M. Christl, E. Gerstner, R. Kemmer, G. Llewellyn, W. Bentley, Chem. Ber. 1994, 127, 367.
[7] S. D. Cho, H. K. Kim, H. S. Yim, M. R. Kim, J. K. Lee, J. J. Kim, Y. J. Yoon, Tetrahedron 2007, 63, 1345.
[8] J. A. Varela, D. Pena, B. Goldfuss, D. Denisenko, J. Kulhanek, K. Polborn, P. Knochel, Chem.–Eur. J.
2004, 10, 4252.
[9] E. N. Manukov, G. N. Bazhina, Khim. Prir. Soedin. 1990, 4, 540; Chem. Abstr. 1991, 114, 102413.
[10] M. Balci, Turk. J. Chem. 1992, 16, 42.
[11] K. Takahashi, T. Suzuki, H. Toda, K. Takase, S. Koseki, T. Nakajima, J. Org. Chem. 1987, 52, 2666.
[12] B. Tao, D. W. Boykin, J. Org. Chem. 2004, 69, 4330.
[13] B. C. Hong, H. C. Tseng, S. H. Chen, Tetrahedron 2007, 63, 2840.
[14] M. Nee, W. F. Gorham, J. D. J. Roberts, Org. Chem. 1981, 46, 1021.
ˇ
[15] P. Müller, J. Rocek, J. Am. Chem. Soc. 1974, 96, 2836.
[16] M. Celik, C. Alp, B. Coskun, M. S. Gultekin, M. Balci, Tetrahedron Lett. 2006, 47, 3659.
[17] W. G. Dauben, M. E. Lorber, D. S. Fullerton, J. Org. Chem. 1969, 34, 3587.
[18] W. Abraham, K. Buck, C. Csongar, E. Henke, D. Kreysig, J. Prakt. Chem. 1979, 321, 117.
[19] I. Ozdemir, S. Demir, B. Cetinkaya, Tetrahedron 2005, 61, 9791.
[20] M. Lourak, R. Vanderesse, Y. Fort, P. Caubere, J. Org. Chem. 1989, 54, 4844.
[21] A. H. A. Tinnemans, W. H. Laarhoven, J. Am. Chem. Soc. 1974, 96, 4611.
[22] K. B. Wiberg, W. F. Chen, J. Am. Chem. Soc. 1974, 96, 3900.
[23] T. Tezuka, M. Kimura, A. Sato, T. Mukai, Bull. Chem. Soc. Jpn. 1970, 43, 1120.
[24] B. E. Huff, T. M. Koenig, D. Mitchell, A. Staszak, Org. Synth. 1998, 75, 53.
[25] G. W. Kabalka, L. Wang, R. M. Pagni, C. M. Hair, V. Namboodiri, Synthesis 2003, 217.
Received October 8, 2007