Catalytic Stereospecific Construction of Aminocyclopropanes from β-Boryl Amides

Iridium-catalyzed reduction of β-boryl amides with tetramethyldisiloxane affords iminium ions in situ. These reactive iminium ions are directly trapped by stereospecific (invertive) reaction with the boronate, delivering aminocyclopropanes (ACPs) in excellent yield, diastereoselectivity, and enantiospecificity. The reaction applies to both secondary and tertiary benzylic boronates, allylic boronates, and α-substituted boronates, giving access to many multiply substituted ACPs.