Access to Chiral ß-Boryl δ-Lactones via NHC-Catalyzed [4 + 2] Annulation.

ABSTRACT

We report a carbene-catalyzed [4 + 2] annulation of activated esters and ß-borate enones, providing an efficient method to build enantioenriched organoborones with two consecutive stereogenic centers. It is worth noting that this protocol represents a new organocatalytic manner to generate chiral ß-C-B bonds. Moreover, it also greatly enriches the structural diversity of the chiral organoboron compounds.