Sigmatropic rearrangements of B(MIDA)-propargylic alcohols towards the diverse synthesis of α-functionalized organoborons

α-Functionalized organoborons are useful building blocks and key structural elements in functional molecules. Their previous synthesis relied on the famous Matteson reaction or the late-stage borylative modification of alkynes or alkenes. Recently, the synthetic transformation of borylated building blocks offers another useful strategy and is currently actively explored. We report herein that B(MIDA)-propargylic alcohols (BPAs) are a useful type of borylated building blocks. Bearing two complementary functional group handles (alkyne and hydroxyl) in close proximity, the redox-neutral [3,3] and [2,3] sigmatropic rearrangements of BPAs allow the efficient synthesis of several types of α-functionalized boronates, including α,β-unsaturated acylborons, α- S / P -substituted allenylborons, boryl-substituted thiazoles and a borylated α,β-unsaturated hydrazine, some of which are otherwise challenging targets using other synthetic methods.