Free-Radical-Promoted Site-Selective C-H Silylation of Arenes by Using Hydrosilanes.

A free-radical-promoted aryl/heteroaryl C-H silylation using hydrosilane was developed. This cross-dehydrogenative silylation enables both electron-rich and electron-poor aromatics to afford the desired arylsilanes in unique selectivity. A "para-selectivity" was observed by examination of over 54 examples. This exceptional orientation is quite different from that in Friedel-Crafts C-H silylation or transition-metal-catalyzed dehydrogenative silylation.