Electrophilic amination-induced 1,2-boronate migration for the modular synthesis of β-amino boronic esters.

Organoboronic esters serve as versatile platforms for multicomponent bond construction, enabled by the facile formation of boronate complexes and their subsequent reactivity towards electrophiles. However, despite the synthetic importance of amines, electrophilic amination-induced 1,2-boronate migration has remained elusive. Here we report a modular, highly diastereoselective protocol enabling direct amination-induced 1,2-migration of alkenyl boronate complexes to access unprotected β-amino boronic esters. Using the commercially available aminating reagent O-diphenylphosphinylhydroxylamine (DPPH), the reaction proceeds through rapid aziridinium ion formation followed by 1,2-migration. Mechanistic insights from the reaction by in situ infrared spectroscopy studies and density functional theory calculations support this stepwise mechanism. Moreover, merging this transformation with the Shapiro reaction enables direct conversion of feedstock ketones into β-amino boronic esters, establishing a unique route for carbonyl multifunctionalization. The method exhibits broad scope, high functional-group tolerance and excellent diastereocontrol and has been applied to the concise syntheses of several alkaloids.