Synthesis of novel 3-heterospiro[5.5]undecanes

Abstract

Synthetic strategies leading to novel 3-heterospiro[5.5]undecan-9-ones are described. Starting from aliphatic 4-substituted heterocyclic aldehydes (1-methyl-4-piperidine carboxaldehyde, 4- formyl-1-piperidinecarboxylic acid 1,1-dimethylethyl ester, 2H-tetrahydrothiopyran-4- carboxaldehyde, and 2H-tetrahydropyran-4-carboxaldehyde) 3-heterospiro[5.5]undec-7-en-9- ones were made by Robinson annelation and upon further hydrogenation gave the desired 3- heterospiro[5.5]undecan-9-ones.