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

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. Eine hocheffiziente synergistische Metall/Proton‐katalysierte Conia‐En‐Reaktion wurde für die Synthese von Bicyclo[3.n.1]alkanonen entwickelt und zur Modifizierung von Naturstoffen wie Methyldihydrojasmonat, α,β‐Thujon und 5α‐Cholestan‐3‐on verwendet. Auch ist eine Ringöffnung der Bicyclo[3.2.1]alkanone durch Nukleophile möglich, und die entsprechenden Produkte werden in sehr guten Ausbeuten erhalten.