Synthesis of sibutramine, a novel cyclobutylalkylamine useful in the treatment of obesity, and its major human metabolites

Abstract

Synthetic routes to N-{1-[1-(4-chlorophenyl)cyclobutyl]-3-methylbutyl}-N,N-dimethylamine (sibutramine) 1 and its demethylated and hydroxylated human metabolites N-{1-[1-(4-chlorophenyl)cyclobutyl]-3-methylbutyl}-N-methylamine 2, 1-[1-(4-chlorophenyl)cyclobutyl]-3-methylbutylamine 3, 4-amino-4-[1-(4-chlorophenyl)cyclobutyl]-2-methylbutan-1-ol 4 and c-3-(1-amino-3-methylbutyl)-3-(4-chlorophenyl)cyclobutan-r-1-ol 5a are described. Key steps are tandem Grignard–reduction reactions on 1-(4-chlorophenyl)cyclobutanecarbonitrile 7 and its 3-(tetrahydropyran-2-yloxy)-substituted analogue 14 and a convenient one-pot conversion of 4-chlorophenylacetonitrile 6 into the 3-hydroxycyclobutanecarbonitrile 13.