An unusual carbon–carbon bond scission reaction with molecular oxygen under mild conditions; formation of piperidines from 1-azabicyclo[2.2.2]octanes

Abstract

Molecular oxygen reacts with 2-(1-phenylethyl)- and 2-benzhydryl-3-alkylimino-1-azabicyclo[2.2.2]octanes 1–7 in neutral solution at room temperature to form 1-acylpiperidine-4-carboxylic acid N-alkylamides 8–14. During the transformation two new carbonyl bonds are formed and a carbon–carbon bond is cleaved. The transformation is quite general provided the 2-substituent of the imine is of sufficient steric bulk, such as the 2-(1-phenylethyl) or 2-benzhydryl groups. No reaction is observed in the absence of a 2-substituent, as in the case of imine 15.