1,3-Dipolar cycloaddition of in situ generated azomethine ylides to electron deficient olefins catalyzed tris(pentafluorophenyl)borane is described.
介绍了三(五氟苯基)硼烷催化的现场生成的腙鎓叶立德与缺电子烯烃的1,3-偶极环加成反应。
[3+2] Dipolar cycloadditions of an unstabilised azomethine ylide under continuous flow conditions
作者:Mark Grafton、Andrew C. Mansfield、M. Jonathan Fray
DOI:10.1016/j.tetlet.2009.12.071
日期:2010.2
The [3+2] dipolar cycloaddition reactions of the unstabilised azomethine ylide precursor benzyl(methoxymethyl)(trimethylsilylmethyl)amine with 12 electron-deficient alkenes in the presence of catalytic trifluoroacetic acid are examined under continuous flow conditions (20-100 degrees C, 10-60 min residence time). The more reactive and hazardous alkenes such as ethyl acrylate, N-methylmaleimide and (E)-2-nitrostyrene afford substituted N-benzylpyrrolidine products in 77-83% yields, whereas less reactive dipolarophiles such as (E)-crotononitrile and ethyl methacrylate give lower yields (59-63%). Under optimised conditions, the reaction with ethyl acrylate is scaled up to afford ethyl N-benzylpyrrol-idine-3-carboxylate (30 g, 87%) in 1 h. (C) 2009 Elsevier Ltd. All rights reserved.
Preparation of Pyrroles by Dehydrogenation of Pyrrolidines with Manganese Dioxide
作者:Bernard Bonnaud、Dennis C. H. Bigg
DOI:10.1055/s-1994-25500
日期:——
The dehydrogenation of pyrrolidines by activated manganese dioxide provides a fairly general and mild method for the preparation of substituted pyrroles.