[3,3] Ring Rearrangement of Oxo- or Aza-Bridged Bicyclo[3.2.1]octene-Based 1,5-Dienes

Hydrogen bonding-promoted tunable approach for access to aza-bicyclo-[3.3.0]octanes and cyclopenta[b] pyrroles

A unified strategy is disclosed that builds on successfully engaging the aniline nitrogen of 1,3-amphoteric γ-aminocyclopentenone for a tandem annulation with electron-poor alkynes, solely assisted by the H-bonding network of HFIP. This metal-free mild strategy provides access to medicinally relevant aza-bicyclo-octanes en route to another important scaffold: cyclopenta[b]pyrrole.

Vicinal stereocenters via asymmetric allylic alkylation and Cope rearrangement: a straightforward route to functionally and stereochemically rich heterocycles

An asymmetric allylic alkylation/Cope rearrangement (AAA/[3,3]) capable of stereoselectively constructing vicinal stereocenters has been developed. Strategically integrated 4-methylation on the 3,3-dicyano-1,5-diene controls stereoselectivity and drives Cope rearrangement equilibrium in the forward direction. The AAA/[3,3] sequence rapidly converts abundant achiral and racemic starting materials into valuable (hetero)cycloalkane building blocks bearing significant functional and stereochemical complexity, highlighting the value of (hetero)cyclohexylidenemalononitriles as launching points for complex heterocycle synthesis. On this line, the resulting alkylidenemalononitrile moiety can be readily converted into amides via Hayashi-Lear amidation to ultimately yield amido-piperidines, tropanes, and related scaffolds with 3-5 stereocenters and drug-like functionality.

Synthesis of 2-aminobenzofurans via base-mediated [3 + 2] annulation of N-phenoxy amides with gem-difluoroalkenes

Efficient metal-free [3 + 2] annulation of N-phenoxy amides with gem-difluoroalkenes has been realized for the assembly of 2-aminobenzofuran derivatives with potent cytotoxicity against cancer cell lines and application potential for DELs.