Regiocontrolled opening of 2-methyltetrahydrofuran with various boron reagents

Regiocontrolled halogenative cleavage of 2-methyltetrahydrofuran with various B-bromoboranes, by a predominantly S(N)2-type mechanism favouring the formation of primary bromide, is described. A comparative study of the relative reactivities of BH(2)Br center dot SMe(2), BHBr(2) center dot SMe(2), BBr(3), (MeO)(2)BBr, and MeOBBr(2) revealed that the newly synthesized (MeO)(2)BBr is a highly promising regioselective reagent, especially at lower temperatures.