Theoretical investigation of the reaction of dialkylzincs with α-alkoxycarbonyl radicals. Evaluation of α-bromoacrylates as radical acceptors in radical-polar crossover processes

Vibert, François; Maury, Julien; Lingua, Hugo; Besson, Eric; Siri, Didier; Bertrand, Michèle P.; Feray, Laurence

Theoretical investigation of the reaction of dialkylzincs with α-alkoxycarbonyl radicals. Evaluation of α-bromoacrylates as radical acceptors in radical-polar crossover processes

2015

The evaluation of ethyl α-bromoacrylate as radical acceptor in dialkylzinc radical-polar cascades addresses the question of the parameters controlling homolytic substitution at zinc by α-alcoxycarbonyl radicals. Under non-degassed medium ethyl α-bromoacrylate reacts with diethylzinc to give a bromocyclopropane. The reaction involves successively radical addition, SH2 at zinc, conjugate addition of the resulting enolate to the electrophilic substrate and ring closure. Theoretical calculations were performed to get a better insight into the detailed mechanism. They highlight the impact of zinc(II) chelation on the formal SH2 step. Additional experiments performed in the presence of other electrophiles–aldehydes and acylsilanes–are discussed.

اظهر المزيد [+]