Ruthenium-Catalyzed Reaction of α,β-Unsaturated Imines with Carbon Monoxide and Alkenes Leading to β,γ-Unsaturated γ-Butyrolactams: Involvement of Direct Carbonylation at Olefinic C−H Bonds as a Key Step
journal contributionposted on 05.09.2002, 00:00 by Naoto Chatani, Akihito Kamitani, Shinji Murai
The reaction of α,β-unsaturated imines with CO and alkenes in the presence of Ru3(CO)12 as a catalyst results in a three-component coupling reaction that gives α,α-disubstituted β,γ-unsaturated γ-butyrolactams. The reaction proceeds via a two-step sequence involving the initial formation of ketone derivatives by catalytic carbonylation at the β-olefinic C−H bonds of α,β-unsaturated imines, followed by the (uncatalyzed) intramolecular nucleophilic attack of the imine nitrogen on the ketonic carbon to generate a tetrahedral intermediate, which then undergoes a 1,2-ethyl migration. The reaction of a cyclic unsaturated imine, derived from the reaction of (1R)-(−)-myrtenal with tert-butylamine, gives a β-aminocyclopentene derivative, which is formed by an aldol-type condensation of the initially formed ketone, indicating the initial formation of ethyl ketone.