109105-83-1Relevant articles and documents
An Oxidative Mannich Cyclization Methodology for the Stereocontrolled Synthesis of Highly Functionalized Piperidines
Wu, Xiao-Dong,Khim, Seock-Kyu,Zhang, Xiaoming,Cederstrom, Ericka M.,Mariano, Patrick S.
, p. 841 - 859 (2007/10/03)
Studies focusing on the development and application of a new oxidative methodology for promoting Mannich cyclizations have been conducted. The general features of these processes were explored with selected α-silylamino and α-silylamido allyl- and vinylsilanes. Representative conditions for affecting conversion of the α-silylamine and -amide functionalities into intermediate N-alkyl and N-acyliminium cations involve either 9,10-dicyanoanthracene SET-sensitized photooxidation or ceric ammonium or tetra-n-butylammonium nitrate oxidations. The applicability of these procedures for promoting Mannich cyclizations was first demonstrated by the preparation of methylidenepi- peridines and -hydroazepines. Further studies have led to observations which show that Mannich cyclizations of stereochemically labeled α-silylamino vinylsilanes proceed to furnish tetrahydro- pyridines. Also, unlike their amine analogues, α-silylamido (E)-vinylsilanes undergo cyclization to produce tetrahydropyridines with retention of absolute and relative stereochemistry. The differences are due to the fact that N-acyliminium cations serve as intermediates in reactions of the α-silylamide systems. Moreover, the oxidation procedure is ideally suited for intermediate N-acyliminium cation generation in stereocontrolled reactions of α-silylamido allylsilanes. Finally, the preparative utility of the new cyclization method, when used in conjunction with an α-amino acid based strategy for substrate generation, was demonstrated by applications in concise routes for the synthesis of the aza-sugars, (-)-1-deoxymannojirimycin and (+)-l-deoxyallonojirimycin.
