Dft Analysis Into The Calcium(Ii)-Catalyzed Coupling Of Alcohols With Vinylboronic Acids: Cooperativity Of Two Different Lewis Acids And Counterion Effects

The mechanism of the calcium-catalyzed coupling of alcohols with vinylboronic acids has been analyzed by means of density functional theory computations. This study reveals that the calcium and boron Lewis acids associate to form a superelectrophile able to promote a pericyclic group transfer reaction with allyl alcohols. With other alcohols, the two Lewis acids act synergistically to activate the OH functionality and trigger a S(N)i reaction pathway. These two mechanisms are affected by the nature of the counterions, which has been rationalized by electronic and steric factors.