ルテナシクロペンテン中間体を経由するエンインの新規環化反応の開発

概要

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Three novel ruthenium–catalyzed cyclizations of enynes were developed. In each cyclization, a ruthenacyclopentene derived from enyne and Cp*RuCl(cod) is a common intermediate. When an enyne having an alkyl, an ester or a formyl group on an alkyne was reacted with Cp*RuCl(cod) under ethylene gas, ethylene was inserted into ruthenium–sp2 carbon bond of the ruthenacyclopentene to afford ruthenacycloheptene, and β–hydrogen elimination followed by reductive elimination occurred to give a cyclic compound having a diene moiety. When an acyl group was placed on the alkyne, the carbonyl oxygen would coordinate to the ruthenium metal of ruthenacyclopentene to produce ruthenium carbene, which would react with ethylene to give a cyclic compound having a cyclopropane ring on the substituent. On the other hand, when the substituent on the alkene was ω–pentene, insertion of an alkene part into ruthenacyclopentene followed by reductive elimination gave a tricyclic compound via a ruthenium–catalyzed [2+2+2]cocyclization of diene and an alkyne.