Synergistic Catalysis: Metal/Proton-Catalyzed Cyclization of Alkynones Toward Bicyclo[3.n.1]alkanones

• Published in: Angewandte Chemie International Edition 2015-08, Vol.54 (32), p.9414-9418
• Main Authors: Zhu, Shifa, Zhang, Qiaohui, Chen, Kai, Jiang, Huanfeng
• Format: Article
• Language: English
• Subjects: bicyclo[3.n.1]alkanones; Carbonyl groups; Catalysis; Conia-ene reaction; cycloheptanone; enolization; Nucleophiles; synergistic catalysis; Synthesis
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201504964

A highly efficient and practical synergistically metal/proton‐catalyzed Conia–ene reaction for the synthesis of bicyclo[3.n.1]alkanones has been developed. This synergistic catalysis was successfully utilized in modifying natural compounds such as methyl dihydrojasmonate, α,β‐thujone, and 5α‐cholestan‐3‐one. Furthermore, the bridged carbonyl group of bicyclo[3.2.1]alkanones could be easily attacked by nucleophiles to give the ring‐opened cycloheptenone products or bicyclo[4.2.1]amide in excellent yields. These reactions provide rapid access to a diverse range of cyclic structures from simple starting materials or naturally occurring compounds. A highly efficient and practical synergistically metal/proton‐catalyzed Conia–ene reaction for the synthesis of bicyclo[3.n.1]alkanones has been developed. The reaction was successfully utilized in modifying natural compounds such as methyl dihydrojasmonate, α,β‐thujone, and 5α‐cholestan‐3‐one. Furthermore, the bicyclo[3.2.1]alkanones can be ring‐opened by nucleophiles to give the corresponding products in excellent yields.