Ring Expansion – Formation of Optically Active 3-Hydroxypiperidines from Pyrrolidinemethanol Derivatives

Abstract

Treatment of pyrrolidinemethanol derivatives (–)-1, (–)-6, (–)-7, 8, (–)-9, (+)-10, (–)-11, and (–)-21 with trifluoroacetic anhydride and then with Et3N afforded, after hydrolysis of the trifluoroacetyl group with NaOH, the optically active 3-hydroxypiperidines (–)-14, (+)-15, (–)-16, 17, (+)-18, (–)-19, (–)-20, and (+)-22, respectively. The yields are good and the enantiomeric excess excellent (up to 95 %).