Strain-Ring Construction Enabled by Boronate Complex/1,2-Metalate Rearrangement

Abstract

Strain-ring construction represents a longstanding challenge in synthetic organic chemistry due to the substantial energetic penalties associated with forming small and highly constrained ring systems. Over the past decade, 1,2-metalate rearrangement of boronate complexes has emerged as a powerful and unifying strategy to overcome these boundaries. By leveraging the exceptional migratory aptitude of carbon substituents from boron, these rearrangements can actively drive ring contraction via skeletal reorganization even in a condition with increased strain. This review compiles key developments in strain-ring construction triggered by boronate complex/1,2-metalate rearrangement, spanning mono-boronic esters to multi-boron frameworks. The collected studies illustrate how electrophilic, radical, and metal-mediated activation modes can be strategically combined with boron migration to access strained carbocycles and heterocycles with high stereocontrol.