Noncryogenic Preparation of Functionalized Arylboronic Esters through a Magnesium-Iodine Exchange with in Situ Quench

Various functionalized aryl boronic esters derived from hexylene glycol and pinacol were prepared in excellent yields according to a simple, safe procedure. The metal-halogen exchange reaction between (PrMgCl)-Pr-i center dot LiCl and aryl iodides is performed at 0 degrees C in the presence of a cyclic borate ester ((MPBOPr)-Pr-i or PinBO(i)Pr); the organomagnesium intermediate is immediately trapped in situ so that no accumulation of hazardous reactive species can occur. The reaction is very selective, and particularly clean crude products are obtained. The scope of the procedure and the tuning of reaction parameters are investigated.