Notes
J . Org. Chem., Vol. 66, No. 11, 2001 4103
through a column of basic alumina. All the products have been
characterized by their IR and 1H (300 MHz) and 13C (75 MHz)
NMR spectra.
significant improvements offered by this method over
existing procedures1,3,4,7 are as follows: (a) no undesired
side reaction including over-reduction, (b) mild conditions
to tolerate several sensitive functional groups, (c) good
stereoselectivity, (d) high yields, and (e) environment-
friendly reaction conditions. Thus, this procedure is
endowed with considerable synthetic potential and may
provide a practical alternative to the existing methodolo-
gies.
Spectral [IR, 1H (300 MHz) and 13C (75 MHz)] and analytical
data for new vinyl bromides, not reported in the literature, are
presented below designated by their entries in Table 1.
1
2: IR 1600, 1587, 935 cm-1; H NMR δ 6.75 (d, J ) 13.8 Hz,
1H), 7.38-7.55 (m, 5H), 7.79-7.87 (m, 3H); 13C NMR δ 108.9,
124.1, 124.7, 125.9, 126.7, 126.9, 128.9, 129.2, 131.0, 133.0, 134.0,
135.5. Anal. Calcd for C12H9Br: C, 61.83; H, 3.80. Found: C,
62.37; H, 3.82.
6: IR 1600, 1614, 1581, 1197, 939 cm-1 1H NMR δ 2.30 (s,
;
3H), 6.67 (d, J ) 14.1 Hz, 1H), 6.95-7.24 (m, 5H); 13C NMR δ
21.9, 106.8, 123.8, 127.3, 129.1, 129.5, 132.9, 135.3, 137.7. Anal.
Calcd for C9H9Br: C, 54.85; H, 4.57. Found: C, 54.48; H, 4.54.
Exp er im en ta l Section
Gen er a l Meth od s. 1H NMR (300 MHz) and 13C NMR (75
MHz) spectra were run in CDCl3 solutions. IR spectra were
taken as thin films. Analyses were done on a Perkin-Elmer 2400
autoanalyzer. Indium metal (Ingot) was purchased from SRL,
India, and was used without any treatment.
7: IR 1606, 1510, 1031, 948 cm-1 1H NMR δ 0.00 (s, 6H),
;
0.78 (s, 9H), 6.38 (d, J ) 13.95 Hz, 1H), 6.57-6.62 (m, 3H), 6.95
(d, J ) 8.10 Hz, 2H); 13C NMR δ -6.2 (2), 16.4, 23.8 (3), 102.3,
118.4 (2), 125.4 (2), 129.8, 134.7, 153.2. Anal. Calcd for C14H21
OSiBr: C, 53.67; H, 6.70. Found: C, 53.42; H, 6.77.
-
Gen er a l Exp er im en ta l P r oced u r e. Rep r esen ta tive P r o-
ced u r e for th e Red u ction of 1,1-Dibr om o-2-p h en yleth en e.
A mixture of 1,1-dibromo-2-phenylethene (1 mmol, 262 mg) and
indium metal (1 mmol, 115 mg, cut into small pieces) in ethanol
(2 mL) and saturated aqueous ammonium chloride solution (2
mL) was heated under reflux for 16 h (monitored by TLC) in an
oil bath (temperature 95-100 °C). The reaction mixture was
then allowed to cool and extracted with ether. The ether extract
was washed with brine, dried over Na2SO4, and evaporated to
leave the crude product, which was purified by column chroma-
tography over silica gel to furnish 1-bromo-2-phenylethene (174
mg, 95%) as an E/ Z mixture (95.5 as determined by 1H NMR
analysis and GC). The 1H and 13C NMR spectra of this compound
are identical with those reported.7c
8: IR 1639, 1600, 1540, 1040, 965 cm-1 1H NMR δ 4.50-
;
4.53 (m, 2H), 5.25-5.41 (m, 2H), 5.99-6.02 (m, 1H), 6.80-6.98
(m, 3H), 7.17-7.35 (m, 3H); 13C NMR δ 69.7, 108.3, 112.7, 118.3,
121.4, 128.4, 129.6, 130.0, 133.4, 134.3, 156.0. Anal. Calcd for
C11H11OBr: C, 55.25; H, 4.60. Found: C, 54.78; H, 4.53.
9: IR 1600, 1514, 1139, 1026 cm-1 1H NMR δ 3.80 (s, 3H),
;
3.82 (s, 3H), 6.55 (d, J ) 14.1 Hz, 1H), 6.70-6.90 (m, 3H), 6.97
(d, J ) 14.1 Hz, 1H); 13C NMR δ 56.1, 56.2, 104.6, 109.0, 111.6,
122.3, 132.1, 137.1, 148.9, 149.7. Anal. Calcd for C10 H11O2Br:
C, 49.39; H, 4.52. Found: C, 48.87; H, 4.29.
1
10: IR 1600, 1577, 1510, 1028, 939 cm-1; H NMR δ 3.80 (s,
3H), 5.07 (s, 2H), 6.56 (d, J ) 14.1 Hz, 1H), 6.69-6.83 (m, 3H),
6.96 (d, J ) 14.1 Hz, 1H), 7.25-7.40 (m, 5H); 13C NMR δ 56.4,
71.4, 104.9, 109.7, 114.2, 119.8, 127.7 (2), 128.4, 128.7, 129.0
(2), 132.3, 137.4, 148.9, 150.2. Anal. Calcd for C16H15O2Br: C,
60.20; H, 4.70. Found: C, 60.67; H, 4.88.
This procedure has been followed for the conversion of all gem-
dibromides listed in Table 1. However, for furan (entry 13) and
thiophene (entry 12) derivatives purification was carried out
(7) (a) Cristol, S. J .; Norris, W. P. J . Am. Chem. Soc. 1953, 75, 2645.
(b) Grovenstein, E., J r.; Lee, D. E. J . Am. Chem. Soc. 1953, 75, 2639.
(c) Graven, A.; J orgensen, K. A.; Dahl, S.; Stanczak, A. J . Org. Chem.
1994, 59, 3543. (d) Chowdhury, S.; Roy, S. J . Org. Chem. 1997, 62,
199. (e) Moughamir, K.; Mazgueldi, B.; Atmani, A.; Mestdagh, H.;
Rolando, C. Tetrahedron Lett. 1999, 40, 59 and references therein. (f)
Naskar, D.; Roy, S. Tetrahedron 2000, 56, 1369 and references therein.
Ack n ow led gm en t. We are pleased to acknowledge
the financial support from CSIR, New Delhi, India, for
this investigation. S.S. and S.K.G. are also thankful to
CSIR for their fellowships.
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