420
M. Kidwai et al. / Chinese Chemical Letters 22 (2011) 417–420
Apart from imidazole derivatives, other N-heterocycles such as pyrrole, benzotriazole, and benzimidazole
exhibited high Markovnikov addition activity. In addition, the reaction was also tried with aliphatic amines and was
found to be unsuccessful under similar conditions, since the N–H of azoles is more acidic than that of aliphatic amines.
3. Conclusion
In summary, we have developed a novel and efficient protocol for the Markovnikov addition using t-BuOK as the
catalyst in acetonitrile under mild conditions with excellent yield. The advantages of this protocol are the simplicity of
operation, the high regioselectivity of products, and utilization of inexpensive and mild basic catalyst. We believe this
will present a better and more practical alternative to the existing methodologies and will find useful application in
organic synthesis. Further work is in progress in this laboratory with the aim of expanding this catalyst.
Acknowledgments
Neeraj Kumar Mishra and Anwar Jahan thank CSIR and UGC, New Delhi, India for grant of the Senior and Junior
Research Fellowships and M. Kidwai is grateful to the University of Delhi for providing financial assistance.
References
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[12] General procedure for the synthesis of N-heterocycles: A mixture of azoles (1 mmol), vinyl acetate (4 mmol) and t-BuOK (1 mmol) in
acetonitrile (3 mL) was stirred at r.t. for the time indicated in Table 2. After the completion of reaction as indicated by TLC, the reaction mixture
was diluted with diethyl ether (10 mL). The organic layer was washed with brine solution (20 mL) and dried over anhydrous sodium sulphate
(Na2SO4), filtered and evaporated under reduced pressure. The residue was purified by silica gel column chromatography using EtOAc: hexane
(20: 80) as an eluent.
Spectral data for the selected compounds: 1-[1-(4-Nitroimidazole)]ethyl acetate (3a): mp: 80–82 8C; IR (KBr): 3130, 1740, 1545, 1495 cmÀ1
.
1H NMR (CDCl3, 300 MHz): d 7.84 (s, 1H), 7.31 (s, 1H), 6.70 (q, 1H, J = 6.75 Hz), 2.08 (s, 3H), 1.87 (d, 3H, J = 6.36 Hz). 13C NMR (CDCl3,
75 MHz): d 168.48, 146.79, 136.17, 119.28, 77.10, 22.01, 20.62. 1-(1-2-Methyl-4-nitroimidazole)-ethyl acetate (3g): mp: 135-136 8C. IR
(KBr): 3094, 1732, 1574, 1507 cmÀ1. 1H NMR (CDCl3, 300 MHz): d 8.01 (s, 1H), 7.11 (q, 1H, J = 6.75 Hz), 2.51 (s, 3H), 2.02 (s, 3H,), 1.68 (d,
3H, J = 6.88 Hz). 13C NMR (CDCl3, 75 MHz): d 169.58, 148.61, 146.12, 120.33, 76.50, 21.18, 20.36, 13.68. 1-(1-Indole)ethyl acetate (3h):
Colourless oil. IR (film): 3095, 1743, 1591, 1507 cmÀ1. 1H NMR (CDCl3, 300 MHz): d 7.80 (m, 1H), 7.51 (m, 1H), 7.39 (m, 2H), 7.23 (d, 1H,
J = 6.65 Hz), 6.79 (d, 1H, J = 6.40 Hz), 6.68 (q, 1H, J = 6.71 Hz), 2.13 (s, 3H), 1.85 (d, 3H, J = 6.75 Hz). 13C NMR (CDCl3, 75 MHz): d
165.28, 132.19, 126.25, 125.06, 118.60, 106.20, 86.32, 18.70, 14.31. 1-(1-Benzotriazole)ethyl acetate (3i): Colourless oil. IR (film): 3067,
1750, 1593, 1491 cmÀ1. 1H NMR (CDCl3, 300 MHz): d 8.42 (d, 1H, J = 7.69 Hz), 7.81 (d, 1H, J = 8.0 Hz), 7.51 (m, 1H), 7.32 (m, 2H), 2.13 (d,
3H, J = 6.18 Hz), 2.01 (s, 3H). 13C NMR (CDCl3, 75 MHz): d 168.59, 132.10, 127.32, 89.68, 18.21, 15.89.