Magnesium promoted cyclopropanation reactions of allylic alcohols
作者:Carsten Bolm、Doris Pupowicz
DOI:10.1016/s0040-4039(97)10009-0
日期:1997.10
Treatment of allylicalcohols 1 with various magnesium reagents in the presence of alkyl dihalides affords the corresponding cyclopropyl alcohols 2. Reactions occur under mild conditions, and excellent diastereoselectivities have been achieved.
Chemo- and diastereoselective cyclopropanation of allylic amines and carbamates
作者:Kristína Csatayová、Stephen G. Davies、James A. Lee、Kenneth B. Ling、Paul M. Roberts、Angela J. Russell、James E. Thomson
DOI:10.1016/j.tet.2010.08.055
日期:2010.10
allylic carbamates has been developed, which provides access to both diastereoisomers of the corresponding cyclopropanes with very high levels of diastereoselectivity: cyclopropanation with the Wittig–Furukawareagent [Zn(CH2I)2] proceeds under chelation control to give the corresponding syn-product, whilst reaction with Shi’s carbenoid proceeds under steric control to give the corresponding anti-cyclopropane
描述了一种高度化学和非对映选择性的方案,用于使用Shi的类胡萝卜素[CF 3 CO 2 ZnCH 2 I]对叔烯丙基胺进行环丙烷化。高水平在这些反应中观察到的非对映选择性的可以归因于该氮原子与锌试剂,然后一个亚甲基单元传送到的螯合顺式烯烃的面取向。此外,已开发出用于一系列烯丙基氨基甲酸酯的环丙烷化的立体发散方案,该方案提供了具有非常高非对映选择性的相应环丙烷的两种非对映异构体的途径:使用Wittig-Furukawa试剂[Zn(CH 2 I)2进行环丙烷化]螯合控制下进行,得到相应的顺式-产物,同时用施的立体控制,得到相应的下卡宾反应进行反-环丙烷,在> 95:在这两种情况下5博士。
Diastereoselective Simmons–Smith cyclopropanations of allylic amines and carbamates
作者:Stephen G. Davies、Kenneth B. Ling、Paul M. Roberts、Angela J. Russell、James E. Thomson
DOI:10.1039/b711358g
日期:——
Cyclopropanation of 3-(N,N-dibenzylamino)cyclohexene with either Zn(CH(2)I)(2)(Wittig-Furukawareagent) or CF(3)CO(2)ZnCH(2)I (Shi's reagent) gives the corresponding syn-cyclopropane as a single diastereoisomer, whilst cyclopropanation of 3-(N-tert-butoxycarbonylamino)cyclohexene with CF(3)CO(2)ZnCH(2)I gives the corresponding anti-cyclopropane exclusively; facile N-deprotection gives access to either
An appropriate solvent to perform the original Simmons–Smith reaction was reinvestigated. Among available solvents, cyclopentyl methyl ether (CPME), a recently commercialized ethereal solvent, was found to be the best so far. Compared with Et2O under reflux – the commonest conditions – reaction completion in CPME at 50 °C was about 10 times faster. The product yields and selectivities were mostly identical