Hofmann消除反应
反应机理
季铵碱加热一般消除含氢较多的β碳上的氢,这个规则与Zaitsev规则相反,称为霍夫曼规则(Hofmann规则)。Hofmann规则的本质是体积效应。从空间位阻较小的位点消除。该反应是经由E1cB或E2机理进行的消除反应。当季铵碱中β氢有明显酸性时,产物为遵守Zaitsev规则的产物。
反应实例
【Heterocycles 1981, 16, 1673-1676】
【J. Am. Chem. Soc. 1989, 111, 7668-7670】
【Tetrahedron Lett. 1989, 30, 5989-5992】
【Tetrahedron 2002, 58, 75-82】
通过Hofmann消除从树脂上解离胺。
【Tetrahedron Lett. 2010, 51, 5003–5004】
【Synth. Commun. 2012, 42, 3545–3552】
相关文献
1. Hofmann, A. W. Ber. 1881, 14, 659–669.
2. Eubanks, J. R. I.; Sims, L. B.; Fry, A. J. Am. Chem. Soc. 1991, 113, 8821–8829.
3. Bach, R. D.; Braden, M. L. J. Org. Chem. 1991, 56, 7194–7195.
4. Lai, Y. H.; Eu, H. L. J. Chem. Soc., Perkin Trans. 1 1993, 233–237.
5. Sepulveda-Arques, J.; Rosende, E. G.; Marmol, D. P.; Garcia, E. Z.; Yruretagoyena,B.; Ezquerra, J. Monatsh. Chem. 1993, 124, 323–325.
6. Woolhouse, A. D.; Gainsford, G. J.; Crump, D. R. J. Heterocycl. Chem. 1993, 30,873–880.
7. Bhonsle, J. B. Synth. Commun. 1995, 25, 289–300.
8. Berkes, D.; Netchitailo, P.; Morel, J.; Decroix, B. Synth. Commun. 1998, 28, 949–956.
9. Morphy, J. R.; Rankovic, Z.; York, M. Tetrahedron Lett. 2002, 43, 6413–6415.
10. Liu, Z.; Medina-Franco, J. L.; Houghten, R. A.; Giulianotti, M. A. Tetrahedron Lett. 2010, 51, 5003–5004.
11. Arava, V. R.; Malreddy, S.; Thummala, S. R. Synth. Commun. 2012, 42, 3545–3552.
参考资料:
一、Name Reactions (A Collection of Detailed Reaction Mechanisms), Jie Jack Li, Hofmann elimination,page 318.
二、Strategic Applications of Named Reactions in OrganicSnthesis, László Kürti and Barbara Czakó, Hofmann elimination,page 206-207.