amounts of authentic materials (or close analogues) and n-
hexadecane, n-heptane or 3,3-dimethylbutan-2-one were added
as a standard. Chromatographic purifications were carried out
using either Sorbsil C60 40/60A or BDH 40–63 µm silica gel
eluting with the given solvent mixture. Ammonia was obtained
from BOC and used directly from the cylinder; drying and dis-
tillation had no perceptible effect on the yields. Experimental
procedures for the preparation of 1,4-dihydrobiphenyl,9 1-
deuterio-1,4-dihydrobiphenyl, 1-phenylcyclohexa-2,5-diene-1-
carboxylic acid with 3,4-dihydrobiphenyl-3-carboxylic acid
(6 ϩ 7), 2-(cyclohex-2-enyloxy)ethyl 1-phenylcyclohexa-2,5-
diene-1-carboxylate (11) from (6 ϩ 7) and non-1-en-6-ol are
given in the supplementary information.† Experimental details
of the reactions of cyclopentyl 1-phenylcyclohexa-2,5-diene-1-
carboxylate with cyclohexenone, methyl acrylate, methylmeth-
acrylate, acrylonitrile and cyclohexene are also given in the
supplementary information.†
The organic layer was dried (MgSO4) and the solvent evapor-
ated to yield a yellow oil (1.4 g). The title compound was
obtained as a slightly yellow oil by column chromatography,
eluting with 2.5% ethyl acetate in light petroleum (1.20 g, 84%).
δH 1.52–1.95 (8 H, m, 4 × CH2), 2.70–2.77 (2 H, m, allylic-H),
5.21–5.28 (1 H, m, t-H), 5.91–6.15 (4 H, m, CH᎐), 7.20–7.40
᎐
(5 H, m, ArH); δC 23.6, 25.8, 32.4, 52.4, 78.0, 124.8, 126.4,
126.8, 127.9, 128.7, 144.2, 173.4; m/z (rel. intensity) 201 (2), 156
(100), 155 (25), 128 (6), 115 (8), 77 (44), 69 (42), 51 (19), 41 (68),
39 (19). The ester was obtained in 38% yield using pyridine as
base. MS and microanalysis indicated minor contamination by
biphenyl.
2-(Cyclohex-2-enyloxy)ethyl 1-phenylcyclohexa-2,5-diene-1-
carboxylate (11)
Thionyl chloride (7.14 g, 60 mmol) was added to 1-phenyl-
cyclohexa-2,5-diene-1-carboxylic acid 6 (3 g, 15 mmol) in dry
dichloromethane (30 cm3). This was refluxed for 6 h and the
solvent was evaporated to yield acid chloride 8 (3.3 g); δH 2.74–
2.80 (2 H, m), 6.07–6.14 (4 H, s), 7.24–7.47 (5 H, m). The acid
chloride was dissolved in dichloromethane (15 cm3) and added
dropwise to a mixture of 3-(2-hydroxyethoxy)cyclohexene
(1.92 g, 13.5 mmol), pyridine (1.2 g, 15 mmol) and a catalytic
amount of DMAP, in dry dichloromethane (30 cm3) and the
mixture was refluxed for 2.5 h. The contents were washed with
NaOH (2 × 20 cm3) followed by HCl (2 × 20 cm3). The organic
layer was dried (MgSO4) and the solvent was evaporated to
yield an orange oil (4.8 g). The title compound was obtained as
a pale yellow liquid by column chromatography eluting with
20% ethyl acetate in light petroleum (3.48 g, 75%); δH 1.51–2.05
(6 H, m, 3 × CH2), 2.65–2.75 (2 H, m, allylic-H), 3.55–3.95 (3 H,
m, CH2, t-H), 4.28–4.32 (2 H, t, J 4.9, CH2), 5.61–6.15 (6 H, m,
1-Phenylcyclohexa-2,5-diene-1-carboxylic acid (6)
1,4-Dihydrobiphenyl (13.3 g, 83.3 mmol) was dissolved in dry
THF (350 cm3) containing TMEDA (10.7 g, 83.3 mmol) under
an atmosphere of N2. To this was added BuLi (5.9 g, 92.2
mmol) at Ϫ40 ЊC and the resulting deep red solution was stirred
for 80 min as the temperature was allowed to rise to 0 ЊC.
The mixture was cooled to Ϫ70 ЊC and poured into a conical
flask containing crushed dry ice causing immediate decoloris-
ation. The THF was evaporated to yield a solid, to which ether
(100 cm3) and NaOH (70 cm3) were added. The layers were
separated and the ether layer was extracted with NaOH (2 ×
70 cm3). The alkaline fractions were combined and neutralised
with excess HCl. The product was extracted with ether (3 ×
150 cm3). The ethereal extracts were combined, dried (MgSO4)
and the solvent was evaporated to yield a white solid (12 g)
consisting of the title compound (7.8 g, 45%) and carboxylic
acid 7 (4.2 g, 24%); δH 2.50–2.62 (2 H, m, allylic-H, 7), 2.68–
2.78 (2 H, m, allylic-H, 6), 3.43–3.59 (1 H, m, t-H, 7), 5.95–6.17
CH᎐), 7.18–7.25 (5 H, m, ArH); δ 19.1, 25.2, 25.8, 28.1, 52.4,
᎐
C
64.7, 65.7, 73.1, 124.8, 125.5, 126.3, 126.8, 127.6, 128.6, 131.0,
143.8, 173.5; m/z (rel. intensity) 324 (Mϩ, 1 %), 242 (6), 228 (6),
225 (7), 181 (5), 155 (100), 128 (10), 115 (10), 81 (36), 77 (27)
(Found: Mϩ, 324.1737. C21H24O3 requires 324.1725).
(6 H, m, CH᎐, 6, 7), 6.31–6.40 (1 H, d, J 10, CH᎐, 7), 7.23–7.46
᎐
᎐
(10 H, m, ArH, 6, 7). This mixture was dissolved in dichloro-
methane (100 cm3) to which maleic anhydride (5.56 g, 56.7
mmol) was added, and refluxed for 5 h. The mixture was
extracted with NaOH (4 × 40 cm3), the alkaline fractions were
combined and neutralised with excess HCl. The product was
extracted with ether (3 × 100 cm3), the ethereal extracts were
combined, dried (MgSO4) and the solvent was evaporated to
yield an orange liquid (15.41 g). Dichloromethane (50 cm3)
and silica gel were added to the product and the solvent was
removed. The product adsorbed onto silica gel, was added to
a sinter funnel packed with silica gel and the column was eluted
with 30% ethyl acetate in light petroleum. The title compound
was obtained as a white solid (6.2 g, 35%), mp 122–124 ЊC
(Found: C, 78.27; H, 6.26. Calc. for C13H12O2: C, 77.98, H,
6.04%); δH 2.68–2.78 (2 H, m, allylic-H), 5.94–6.14 (4 H, m,
Ethyl 1-phenylcyclohexa-2,5-diene-1-carboxylate
To 1,4-dihydrobiphenyl (2 g, 12.8 mmol) in dry THF (75 cm3)
under an atmosphere of N2 was added BuLi (0.95 g, 14 mmol)
at Ϫ40 ЊC and the resulting dark red solution was left stirring
for 80 min as the temperature was allowed to rise to 0 ЊC.
The mixture was quenched with ethyl chloroformate (1.53 g,
14 mmol) in dry THF (5 cm3) causing the solution to turn
pale red. Another addition of ethyl chloroformate (1.53 g,
14 mmol) caused the solution to turn yellow and this mixture
decolorised overnight. The solvent was evaporated, ether
(150 cm3) was added to the residue and this was washed with
H2O (2 × 100 cm3). The ether layer was dried (MgSO4) and
the solvent was evaporated to give an orange oil (3.47 g). The
title compound was obtained as a slightly discolored liquid by
column chromatography eluting with 15% ethyl acetate in
light petroleum (0.78 g, 27%); δH 1.23–1.31 (3 H, t, J 7.2, CH3),
2.93–3.00 (2 H, m, allylic-H), 4.18–4.30 (2 H, q, J 7.2, CH2),
CH᎐) 7.21–7.40 (5 H, m, ArH); δ (50 MHz) 25.9 (allylic-C),
᎐
C
52.4 (C), 125.0, 126.6, 127.2, 129.0 (9 × CH), 143.3 (C), 180.0
(CO); m/z (rel. intensity) 200 (2), 156 (12), 155 (100), 154 (27),
153 (24), 152 (14), 128 (12), 115 (16), 77 (54), 76 (18), 51 (31).
5.98–6.38 (4 H, m, CH᎐), 7.29–7.50 (5 H, m, ArH).
᎐
Cyclopentyl 1-phenylcyclohexa-2,5-diene-1-carboxylate (10)
Attempted preparation of 1-phenylcyclohexa-2,5-diene-1-
carboxylates with phosgene
Thionyl chloride (2.38 g, 0.02 mol) was added to 1-phenyl-
cyclohexa-2,5-diene-1-carboxylic acid (1.0 g, 0.005 mol) dis-
solved in dry dichloromethane (20 cm3). This mixture was
refluxed under nitrogen for 6 h and the solvent evaporated to
give the acid chloride. The acid chloride was dissolved in dry
dichloromethane (10 cm3) and added dropwise to a mixture
of cyclopentanol (0.43 g, 0.005 mol), 2,6-lutidine (0.54 g,
0.005 mol) and a catalytic amount of DMAP, in dry dichloro-
methane (10 cm3) and the resultant mixture was refluxed under
nitrogen for 6 h. The contents were washed with NaOH (2 ×
50 cm3) followed by HCl (2 × 50 cm3) and water (2 × 50 cm3).
To 1,4-dihydrobiphenyl (1 g, 6.41 mmol) in dry THF (50 cm3)
under an atmosphere of N2 was added BuLi (0.45 g, 7.04 mmol)
at Ϫ78 ЊC and the resulting dark red solution was left stirring
for 80 min at Ϫ60 ЊC to Ϫ78 ЊC. Using a cannula, the mixture
was added to phosgene (0.76 g, 7.7 mmol) in toluene cooled to
Ϫ78 ЊC, and the resulting mixture was left stirring overnight.
The solvent was evaporated and ether (50 cm3) was added to
the residue and this was washed with H2O (50 cm3). The ether
layer was dried (MgSO4) and the solvent was evaporated to give
J. Chem. Soc., Perkin Trans. 1, 2002, 304–309
307