The photolysis of 1-methyl-1-(trimethylsilyl)dibenzosilole (I) and 1-phenyl-1-(trimethylsilyl)dibenzosilole (II) has been investigated. Irradiation of I in the presence of acetone afforded 1-isopropoxy-1-methyl-2-(trimethylsilyl)dibenzosilole(III), while in the presence of isobutene, I afforded 1-isobutyl-1-methyl-2-(trimethylsilyl)dibenzosilole (V). The photolysis of II in the presence of acetone