科里-富克斯反应
科里-富克斯反应,又称拉米雷斯-科里-富克斯反应,指醛与四溴化碳和三苯基膦反应,发生一碳同系化生成二溴烯烃,然后再用正丁基锂处理而得到末端炔烃。[1][2][3]
![科里-富克斯反应](http://images.weserv.nl/?url=//upload.wikimedia.org/wikipedia/commons/thumb/5/56/Corey-Fuchs_Reaction_Scheme.png/450px-Corey-Fuchs_Reaction_Scheme.png)
反应由美国化学家艾里亚斯·詹姆斯·科里和菲利普·L·富克斯的名字命名。与早期Desai等[4]制取二溴烯烃的方法相比,锌粉的加入促进了叶立德中间体的生成,从而减少了三苯基膦的用量,分离更易,产率更高。对于敏感的底物,需用三乙胺代替锌才能取得较好的效果。[5]
反应机理
目前普遍接受的机理为,首先三苯基膦亲核进攻四溴化碳夺取一个溴离子,生成鏻离子,它受到同时生成的溴仿负离子的亲核取代,形成二溴亚甲基磷叶立德。之后与维蒂希反应类似,二溴亚甲基碳与醛羰基进行亲核加成,形成的两性中间体环化为氧磷杂环丁烷,进一步消除为三苯基氧膦和二溴烯烃。
二溴烯烃与正丁基锂交换为锂代二溴烯烃,它发生β-消除生成溴代末炔。溴代末炔与正丁基锂再交换为末炔锂,末炔锂最后经水或卤代烃等亲电试剂处理,得末端炔或内炔。
参见
参考资料
- ^ Corey, E. J.; Fuchs, P. L. A synthetic method for formyl → ethynyl conversion (RCHO → RCCH or RCCR′). Tetrahedron Lett. 1972, 13 (36): 3769–3772. doi:10.1016/S0040-4039(01)94157-7.
- ^ Mori, M.; Tonogaki, K.; Kinoshita, A. "Synthesis of 1,3-Dienes from Alkynes and Ethylene: Acetic Acid 2-Methylene-3-phenethylbut-3-enyl Ester (页面存档备份,存于互联网档案馆)". Organic Syntheses, Vol. 81, p.1 (2005).
- ^ Marshall, J. A.; Yanik, M. M.; Adams, N. D.; Ellis, K. C.; Chobanian, H. R. "Generation of Nonracemic 2-(t-Butyldimethylsilyloxy)-3-butynyllithium from (S)-Ethyl Lactate (页面存档备份,存于互联网档案馆)". Organic Syntheses, Vol. 81, p.157 (2005).
- ^ N. B. Desai, N. McKelvie. A New Synthesis of 1,1-Dibromoölefins via Phosphine-Dibromomethylenes. the Reaction of Triphenylphosphine with Carbon Tetrabromide. J. Am. Chem. Soc. 1962, 84 (9): 1745–1747. doi:10.1021/ja00868a057.
- ^ D. Grandjean, P. Pale and J. Chuche. An improved procedure for aldehyde-to-alkyne homologation via 1,1-dibromoalkenes; synthesis of 1-bromoalkynes. Tetrahedron Letters. 1994, 35 (21): 3529–3530. doi:10.1016/S0040-4039(00)73227-8.
- ^ Craig M. Williams and Lewis N. Mander. Bridgehead Arylation: A Direct Route to Advanced Intermediates for the Synthesis of C-20 Diterpene Alkaloids. Org. Lett. 2003, 5 (19): 3499–3502. doi:10.1021/ol0353060.
- ^ Zhe Wang, Silvio Campagna, Kaihong Yang, Guoyou Xu, Michael E. Pierce, Joseph. M. Fortunak, and Pat. N. Confalone. A Practical Preparation of Terminal Alkynes from Aldehydes. J. Org. Chem. 2000, 65 (6): 1889–1891. doi:10.1021/jo9916582.