Preparation of optically active bicyclodihydrosiloles by a radical cascade reaction

Bicyclodihydrosiloles were readily prepared from optically active enyne compounds by a radical cascade reaction triggered by tris(trimethylsilyl)silane ((Me(3)Si)(3)SiH). The reaction was initiated by the addition of a silyl radical to an α,β-unsaturated ester, forming an α-carbonyl radical that underwent radical cyclization to a terminal alkyne unit. The resulting vinyl radical attacked the silicon atom in an S(H)i manner to give dihydrosilole. The reaction preferentially formed trans isomers of bicyclosiloles with an approximately 7:3 to 9:1 selectivity.