Allylboration of Ketones Catalyzed by BINOL Derivatives: Which Species Are Involved Depending on Substrate Reactivity?

Allylboration reactions of ketones catalyzed by BINOL
derivatives
can exhibit highly variable stereochemical courses depending on the
nature and reactivity of the ketone substrate. In this Article, we
put into perspective the relationship between the nature of the starting
material and the active species involved in the asymmetric allyboration
catalyzed by BINOL derivatives. This work, aimed at comparing different
plausible mechanisms by density functional theory (DFT) at the M06-2X/6-311+G(d,p)
level involving different types of allylboronates in the presence
of the organocatalyst, leads to the confirmation of the hitherto accepted
hypothesis of a reaction promoted by the transient cyclic allyl-1,3,2-dioxaborolane
derived from BINOLs in the case of unactivated or weakly activated
ketones such as indanone. A hypothetical scenario involving dimeric
boronate species as chiral catalysts was also investigated.