Stereoselective Multicomponent Assembly of Enantiopure Oxazolopiperidines and -azepines
作者:Nicolas Zill、Angèle Schoenfelder、Nicolas Girard、Maurizio Taddei、André Mann
DOI:10.1021/jo202455c
日期:2012.3.2
efficient diastereoselective preparation of oxazolopiperidines (4a–e) and -azepines (7a–d). The bicyclic oxazolidines were obtained from chiral N-alkenylamino alcohols via transient cyclic iminium intermediates that underwent an intramolecular cyclization from the appendant oxygen. On the basis of a series of different experimental conditions, the diastereocontrol observed during the formation of the
Methods for the preparation of substituted homoallylic amines and their conversion to pyrrolidines or pyrrolizidines are described. N-Alkylation of a variety of homoallylic secondary amines with (tributylstannyl)methyl methanesulfonate and subsequent tin-lithium exchange, generates organolithium species that undergo intramolecular carbolithiation (anionic cyclization). High stereoselectivities in the cyclization, particularly for the formation of 2,4-disubstituted pyrrolidines, are obtained.