3-Azetidinylpiperidine-4-alkylidenemalononitrile and Related Building Blocks

Cyclobutanes, azetidines, and oxetanes have become more prevalent as structural features on pharmaceutical leads and drugs due to their unique physicochemical and biological properties. Substitution of (hetero)cyclobutanes in a stereocontrolled fashion with pharmaceutically relevant functionality is still a modern challenge. Described herein is a method for constructing quaternary (hetero)cyclobutanes and linking them to other (hetero)cycles via an allylic alkylation/exocyclic strain-release Cope rearrangement. The one- or two-step sequence can yield uniquely linked heterocycles bearing an alkylidenemalononitrile functional group, which can be readily transformed into amides diastereoselectively. This study includes optimization and scope studies of the allylic alkylation/[3,3] sequence, enantioselective optimization using asymmetric allylic alkylation, and functional group interconversion studies to yield densely substituted drug-like scaffolds.