Synthesis of functionalized cyclopropanes from alkyl pinacol boronates by a radical polar cyclization cascade

Abstract

Herein, we report a novel strategy for the synthesis of functionalized cyclopropanes via a photoredox-catalyzed radical addition-polar cyclization cascade. This reaction enables efficient cyclopropane assembly via a radical-polar crossover-mediated reductive termination between alkyl pinacol boronates and electron-deficient alkenes, generating carbanion intermediates that undergo intramolecular alkylation to complete the strained ring formation. This work, achieving the synthesis of 28 cyclopropane derivatives with up to 85 % yield, not only provides a versatile toolbox for strained ring synthesis but also advances the fundamental understanding of boron radical chemistry in photoredox systems.