ELECTROCHEMICAL SILYLATION OF PHENYLACETYLENE

Electrochemical reduction of chlorotrimethylsilane and dichlorodimethy lsilane in the presence of phenylacetylene results in silylated ethyny l and ethenyl derivatives-phenyl(trimethylsilyl)acetyl and trimethylsi lylstyrene. Under similar conditions, phenyl(trimethylsilyl)acetylene gives a product which corresponds to the addition of Me(3)Si(-) anion to the triple bond. By varying the conditions of the electrolysis (the ratio of the reagents, quantity of electricity passed and on carrying out the electrolysis in ECE-mode), either mono- (up to 82% yield) ord isilylated (up to 61% yield) products were obtained. The use of the bi functional chlorosilane as a silylating reagent results in dimethyl bi s(phenylethynyl) silane (20% yield). The active silylating species of the process was shown to be the Me(3)Si(-) -anions, though some assist ance from secondary silyl-radicals cannot be ignored. A mechanism of s ilylation is discussed. Copyright (C) 1996 Elsevier Science Ltd.