Preparation of 2,3,4-Trisubstituted Piperidines by a Formal Hetero-Ene Reaction of Amino Acid Derivatives
作者:Sabine Laschat、Roland Fröhlich、Birgit Wibbeling
DOI:10.1021/jo951482d
日期:1996.1.1
from alanine, leucine, or phenylalanine methyl esters in five steps, can be cyclized diastereoselectively in the presence of Lewis acids to give 3-amino-2,4-dialkyl-substituted piperidines. The product distribution and diastereoselectivity depends on the type of Lewis acid and nitrogen-protecting group. Benzyl-protected imines give 2-alkyl-3-(benzylamino)-4-isopropenyl piperidines with FeCl(3) and 2
从丙氨酸,亮氨酸或苯丙氨酸甲酯分五个步骤获得的N-苄基或N-甲苯磺酰基-N-(4-甲基-3-戊烯基)氨基醛苄基亚胺可在路易斯酸存在下非对映选择性环化得到3-氨基-2,4-二烷基取代的哌啶。产物分布和非对映选择性取决于路易斯酸和氮保护基团的类型。苄基保护的亚胺可生成带有FeCl(3)的2-烷基-3-(苄氨基)-4-异丙烯基哌啶和带有TiCl(4)的2-烷基-3-(苄基亚氨基)-4-异丙基哌啶。甲苯磺酰基保护的亚胺显示出降低的选择性水平。通过NMR和X射线晶体结构分析确定哌啶的相对构型。亚胺离子环化之后是两个竞争性离子途径,即