786
H. SALIM, X. CHEN AND Z. RAPPOPORT
over silica gel using petroleum ether (40–60°C) as eluent
giving 95 mg (45%) of the vinyl bromide as a white solid,
m.p. 180–181°C, mixed m.p. 180°C, identified as the
isomer obtained in the other experiments.
(d) To a solution containing Z-4-OH (180 mg,
0.5 mmol) and sodium bicarbonate (1.5 g, 18 mmol) in
CCl4 (4 ml), POBr3 (1.32 g, 2.64 mmol) was added and
the mixture was refluxed for 5.5 h. Work-up as above
gave a solid (55 mg, 26%) with NMR spectra identical to
that described in above.
dried (Na2SO4), the solvent was evaporated and column
chromatography of the remaining solid over silica gel
using petroleum ether (40–60°C) eluent yielded 91 mg
(74%) of Z-4-Br, m.p. 180–181°C, having 1H NMR data
as reported above for the reaction with PBr3.
Z-1,2-Dimesityl-2-phenylvinyl iodide ꢀZ-4-I)
To a solution of 1,2-dimesityl-2-phenylvinyl tosylate (Z-
4-OTs, 30 mg, 0.177 mmol) in acetonitrile (10 ml), KI
(90 mg, 0.54 mmol) was added and the mixture was
refluxed for 26 h (when the reaction was complete
according to TLC). Water (5 ml) was added with stirring
and the mixture was extracted with CCl4 (5 Â 3 ml),
dried (Na2SO4) and the solvent was evaporated. The
residue was purified by chromatography on silica gel
using petroleum ether (40–60°C) as eluent, yielding pure
Z-4-I (62 mg, 76%), m.p. 186–187°C. 1H NMR (CDCl3)
ꢀ: 2.30 (3H, s, Me), 2.31 (6H, s, Me), 2.33 (6H, s, Me),
2.35 (3H, s, Me), 6.84–7.09 (9H, m, Ar).
(e) The single crystal obtained previously by the same
method, which gave by X-ray crystallography the E-4-Br
structure, was retrieved and analyzed. It has m.p. 174–
175°C (mixed m.p. of a 1:1 mixture with Z-4-Br, 151–
1
153°C). H NMR (CDCl3) ꢀ: 2.11 (6H, s, o-Me), 2.13
(3H, s, p-Me), 2.18 (3H, s, p-Me), 2.28 (6H, s, o-Me),
6.63 (2H, s, Mes-H), 6.70 (2H, s, Mes-H), 7.19–7.32 (5H,
m, Ph). Small signals at ꢀ 2.146, 2.196, 2.293, 2.327 and
2.335 were also observed.
Z-1,2-Dimesityl-2-phenylvinyl tosylate ꢀZ-4-OTs)
Anal. Found: C, 66.57; H, 6.01. Calc. for C26H27I: C,
66.97; H, 5.79%.
A mixture of Z-4-OH (0.14 g, 0.39 mmol) and NaH
(0.16 g, 6.7 mmol) in dry benzene (10 ml) was stirred at
room temperature for 2 h, and tosyl chloride (0.09 g,
0.47 mmol) was then added to the mixture. After stirring
for 2 h, TLC showed that 1-OH was still present. More
tosyl chloride (0.05 g, 0.27 mmol) was added and the
reaction was complete within 20 min. The solid was
filtered, washed with dry ether and the combined
solutions were dried (MgSO4). The solvent was removed
and the remaining crude product was recrystallized from
ether, giving the tosylate (0.18 g, 90%) as a white solid,
m.p. 140–141°C (dec.). 1H NMR (CDCl3) ꢀ: 2.20 (6H, s,
Me), 2.28, 2.35, 2.37 (3 Â 3H, 3s, Me), 2.39 (6H, s, Me),
6.70 (2H, s, Mes-H), 6.87–6.90 (2H, m, Ar), 6.95 (2H, s,
Mes-H), 7.02–7.07 (5H, m, Ph), 7.08–7.11 (2H, m, Ar).
13C NMR (CDCl3) ꢀ: 20.67, 20.84, 21.18, 21.23, 21.65 (5
Me), 127.26, 127.42, 127.97, 128.41, 128.61, 128.80,
129.47, 131.74, 134.79, 134.96, 136.07, 136.40, 136.76,
138.75, 139.31, 143.69, 143.88 (18 Ar-C).
Attempts to prepare the vinyl iodide by reacting Z-4-
OH with iodine/imidazole in tetrahydrofuran or aceto-
nitrile, or with Me3SiCl/NaI (or KI) in CH3CN or with
Ph3P/I2 in CH3CN failed.
The configuration was shown to be Z by X-ray
crystallography.
Attempted Z-4-BrE-4-Br isomerization
A solution of Z-4-Br (70 mg, 0.17 mmol) in acetonitrile
(10 ml) containing anhydrous LiBr (120 mg, 1.38 mmol)
was refluxed for 72 h. TLC of the mixture during and at
the end of the reaction showed only the starting material.
A similar reaction mixture was refluxed in dimethyl-
sulfoxide for 8 h with a similar conclusion. Only Z-4-Br
was detected by TLC or after work-up of the reaction
mixture.
Anal. Found: C, 77.24; H, 6.76; S, 6.17. Calc. for
C33H34O3S: C, 77.60; H, 6.71; S, 6.28%.
Crystallographic data
E-4-Br: C26H27Br; space group: P21/c; a = 14.177(3)
˚
˚
˚
Z-4-Br from the solvolysis of 1,2-dimesityl-2-
phenylvinyl tosylate
A, b = 14.308(3) A, c = 10.911(2) A, b = 98.18(1)°; V =
2191(1) A ; Z = 4; ꢁcalc = 1.27 g cmÀ3; m(Mo Ka) =
3
˚
18.63 cmÀ1; no. of unique reflections: 4024; number of
reflections with I >3ꢂI: 2121; R = 0.054, RW = 0.060.
Z-4-Cl: C28C27Cl; space group P21/c; a = 8.937(2)
A solution of 1,2-dimesityl-2-phenylvinyl tosylate (Z-4-
OTs), (150 mg, 0.29 mmol), LiBr (100 mg, 1.15 mmol),
and tetrabutylammonium bromide (120 ml, 0.37 mmol)
in acetonitrile (5 ml) was refluxed for 18 h, when TLC
showed the complete disappearance of the tosylate and
only one new spot for Z-4-Br. Water (3 ml) was added
with stirring and the mixture was extracted with CCl4
(2 Â 2 ml). The organic phase was washed with water,
˚
˚
˚
A, b = 61.45(1) A, c = 8.458(3) A, b = 113.87(2)°, V =
3
4248(2) A ; Z = 8; ꢁcalc = 1.17 g cmÀ3; m(Cu Ka) =
˚
16.26 cmÀ1; no. of unique reflections: 7106; no. of
reflections with I >3ꢂI: 5704; R = 0.049, RW = 0.075.
Z-4-Br: C26H27Br; space group: P21/n; a = 29.86(1)
˚
˚
˚
A, b = 8.560(6) A, c = 17.358(5) A, b = 104.59(3)°; V =
Copyright 2001 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2001; 14: 778–787