Transition metal-free synthesis of alkyl pinacol boronates

Alkyl pinacol boronic esters have been routinely used for the synthesis of complex target molecules or high-value chemicals due to their non-toxicity, stability and commercial availability. The synthesis of C-B bonds in the absence of transition metals has gained significant attention due to its added advantages. Numerous methods have been developed for the synthesis of alkyl pinacol boronates without transition metals, which include reactions using organometallic reagents, Lewis acids and bases, photoredox catalysis, and 1,2-metallate rearrangement. Herein, we have analyzed the growing resource of literature related to the transition metal-free synthesis of alkyl pinacol boronic esters based on the differences in their reaction mechanisms.