136294-50-3Relevant academic research and scientific papers
TIN TETRACHLORIDE-INDUCED ?-CYCLIZATIONS OF GLYCINE CATION EQUIVALENTS TO SUBSTITUTED PIPECOLIC ACID DERIVATIVES
Esch, Peter M.,Boska, Ilona M.,Hiemstra, Henk,Boer, Richard F. de,Speckamp, W. Nico
, p. 4039 - 4062 (2007/10/02)
Cationic ?-cyclization reactions of N-(3-alkenyl)-N-(methoxycarbonyl)acetoxyglycine esters induced by tin tetrachloride in dichloromethane are described.Reactions started and quenched with water at -78 deg C mainly yield cis-4-hydroxypipecolic esters, whereas reactions quenched after warm-up to room temperature provide trans-4-chloropipecolic esters as major products.A mechanistic scheme is advanced which adequately explains these results.The essentials are a rapid cationic aza-Cope equilibrium of the incipient iminium cation, and participation of the ester moiety through formation of a relatively stable bicyclic dioxycarbenium cation as pivotal intermediate.
