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

The reaction of alpha, beta-unsaturated imines with CO and alkenes in the presence of Ru-3(CO)(12) as a catalyst results in a three-component coupling reaction that gives alpha, alpha-disubstituted beta, gamma-unsaturated gamma-butyrolactams. The reaction proceeds via a two-step sequence involving the initial formation of ketone derivatives by catalytic carbonylation at the beta-olefinic C-H bonds of alpha, beta-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 beta-aminocyclopentene derivative, which is formed by an aldol-type condensation of the initially formed ketone, indicating the initial formation of ethyl ketone.