The addition of .gamma.-(trimethylsilyl)allylboronates to imines
作者:Peter G. M. Wuts、Yong Woon Jung
DOI:10.1021/jo00001a067
日期:1991.1
The addition of gamma-(trimethylsilyl)allylboronates to imines is described and compared with the addition of simple allylboronates to imines. The addition of gamma-(trimethylsilyl)allylboronates to imines is found to be more efficient than the addition of simple allylboronates to imines. The stereoselectivity is dependant upon the nature of the imine; imines derived from aromatic aldehydes give anti products and imines derived from aliphatic aldehydes give syn products. Proof of stereochemistry was established by conversion of the anti and syn derivatives to their respective Z- and E-dienes by a methylation/E-2 elimination process. With alpha-alkoxy aldehydes the reaction proceeds with excellent selectivity giving the product of Felkin-Ahn addition.
Stereoselective Anionic Cyclizations to Pyrrolidines
作者:Iain Coldham、Richard Hufton、Richard E Rathmell
DOI:10.1016/s0040-4039(97)01808-x
日期:1997.10
Cyclization of alpha-amino-organolithiums onto unactivated alkenes results in the formation of 2,4-disubstituted pyrrolidines with high selectivities in favour of the cis isomers. The use of the alpha-methylbenzyl chiral auxiliary on the nitrogen atom gives rise to 3-substituted pyrrolidines with up to 58% d.e. Without the chiral auxiliary, enantioselectivities in the presence of (-)-sparteine are poor. (C) 1997 Elsevier Science Ltd.