Multicomponent assembly and diversification of novel heterocyclic scaffolds derived from 2-arylpiperidines.

A collection of structurally diverse, polyheterocyclic scaffolds comprising a 2-arylpiperidine subunit were synthesized using a Mannich-type multicomponent assembly process, followed by appropriately sequenced ring-forming reactions. An improved procedure for removal of N-4-pentenoyl groups was developed; one-pot sequences for tandem urea/thiourea formation and cyclization and tandem enolate arylation/alkylation were discovered. A novel entry to bridged tetrahydroquinoline scaffolds exploiting A(1,3) strain was also invented. Derivatization of several scaffolds was achieved by cross-coupling and N-functionalization.