Carboxylation and Mitsunobu reaction of amines to give carbamates: retention vs inversion of configuration is substituent-dependent.

A mild method for the synthesis of carbamates from amino alcohols involves sequential carboxylation with carbon dioxide, followed by a Mitsunobu reaction. Unexpectedly, the stereochemical course of the Mitsunobu reaction is dependent on whether the carbamic acid intermediate is N-substituted with hydrogen (retention) or carbon (inversion). Copyright 2004 American Chemical Society