Highly Efficient Synthesis of Alkylboronate Esters via Cu(II)-Catalyzed Borylation of Unactivated Alkyl Bromides and Chlorides in Air

A copper­(II)-catalyzed borylation
of alkyl halides with bis­(pinacolato)­diboron
(B2pin2) has been developed, which can be carried
out in air, providing a wide range of primary, secondary, and some
tertiary alkylboronates in high yields. A variety of functional groups
are tolerated and the protocol is also applicable to unactivated alkyl
chlorides (including 1,1- and 1,2-dichlorides). Preliminary mechanistic
investigations show that this borylation reaction involves one-electron
processes.