A new method for the synthesis of α-bromoacyl silanes via ring-opening of 2-phenylsulphonyl-2-trimethylsilyloxiranes

Abstract

2-Phenylsulphonyl-2-trimethylsilyloxiranes 2 are efficiently prepared by treatment of 2-phenylsulphonyloxiranes 3 with butyllithium in the presence of chlorotrimethylsilane at low temperatures. Reaction of 3-alkyl-2-phenylsulphonyl-2-trimethylsilyloxiranes 2, in which the alkyl group is primary, with magnesium bromide at room temperature gives 2-bromoacyl silanes 1 in good yield. Reaction at higher temperatures leads to competing formation of bromovinyl sulphones 7. Reaction of 3,3dialkyloxiranes with magnesium bromide occurs much more readily, leading to 2-bromoacyll silanes 1 in moderate yields. Other products derived from a common carbocationic intermediate are also isolated.