A Modular Access to 1,2‐ and 1,3‐Disubstituted Cyclobutylboronic Esters by Consecutive Radical Additions

A modular approach to substituted cyclobutylboronic esters is described. It proceeds by successive intermolecular radical additions of xanthates pinacolato 1-cyclobutenylboronate and bicyclo[1.1.0]but-1-ylboronate. Success hinges on tuning the stability α-boryl exploiting stabilizing influence trivalent boronic ester slightly destabilizing cyclobutane, which increases σ-character radical. Reductive removal xanthate group finally provides a range 1,2- 1,3-disubstituted esters. The contrast with cyclopropylboronic striking, since strong destabilization highly strained cyclopropane ring allows first addition take place but not second. Furthermore, adducts are geminal xanthyl that can be converted into cyclobutanones. This chemistry furnishes would quite difficult obtain otherwise thus complements existing methods.