Construction of 1,3-Diboryl Allenes from gem-Iododiboron Compounds via Intermolecular Boryl Group Transfer^†

Allenylboronates are valuable synthetic building blocks and have garnered significant interest. However, their 1,3-diboyl substituted analogs have not been reported. Herein, we disclosed a novel method for creating 1,3-diboyl allenes from gem-iododiboron compounds and alkynyl Grignard reagents. The starting materials are initially converted into the corresponding propargylic gem-bis(boronates), which then undergo an intermolecular boryl group transfer to afford 1,3-diboyl allenes, as confirmed by mechanistic studies. This method features good tolerance to steric hindrance and is compatible with a wide variety of functional groups.