Palladium‐Catalyzed Decarboxylative Benzylation and Allylation of Six‐Membered Endocyclic Enecarbamates

Abstract

Six‐membered endocyclic benzyl/allyl enecarbamates undergo a Pd‐catalyzed decarboxylation process to generate endocyclic 1‐azaallyl anions and Pd–benzyl/allyl cations. The ion pair then react with each other followed by reduction to ultimately give unprotected ‐2‐(hetero)aryl‐3‐benzylpiperidines and 2‐(hetero)aryl‐3‐allylpiperidines in 31−91% yields as single cis‐diastereomers. These reactions represent a strategy to form unprotected β‐substituted piperidines, which generates elusive endocyclic 1‐azaallyl anion intermediates by introducing the negative charge from the N‐terminal.