Carbamoylstannation of terminal alkynes with carbamoylstannanes: Catalyst-dependent regiochemical reversal

Rh(acac)(CO)(2) catalyzes addition of (N,N-diisopropylcarbamoyl)trimethylstannane to terminal alkynes to give (Z)-beta-stannyl-alpha,beta-unsaturated amides with terminal attachment of the amide group, while the use of Ni(COd)(2) results in the reversal of the regioselectivity. A mechanism initiated by the oxidative addition of the carbamoylstannane was proposed on the basis of the isolation of (trimethylstannyl)(N,N-diisopropylcarbamoyl)[1,2-bis(dimethylphosphtno)ethane]pallidium.