Use of the mannich reaction in the synthesis of bispidine

A three-step synthesis of bispidine ( 1 ) is described. Mannich condensation of N-benzyl-4-piperidone, formaldehyde, and benzylamine afforded N,N′-dibenzylbispidinone ( 5 ), which was reduced under modified Wolff-Kishner conditions to yield N,N′ -dibenzylbispidine ( 6 ). Catalytic debenzylation of this compound gave 1 .