Metal-free borylative ring-opening of vinyl epoxides and aziridines

A rational approach towards the borylative ring-opening of vinylepoxides and vinylaziridines, by the in situ formed MeO^–→bis(pinacolato)diboron adduct, has been developed. The enhanced nucleophilic character of the Bpin (sp²) moiety from the reagent favours the SN₂′ conjugated B addition with the concomitant opening of the epoxide and aziridine rings. The reaction proceeds with total chemoselectivity towards the polyfunctionalised (-OH or -NHTs) allyl boronate. Theoretical calculations have determined the transition states that come from the reaction of the vinylic substrates with the activated MeO^–→bis(pinacolato)diboron adduct, and a plausible mechanism for the organocatalytic borylative ring opening reaction has been suggested.