Sensitized photochemical reactions of some silyl-1,3-butadienes: Synthesis of 2,2,4-trimethyl-3-methylene-2-silabicyclo [2.1.1]Hexane

The photolysis of 2,4,4-trimethyl-4-sila-3-methylene-l,5-hexadiene

yielded 2,2,4-trimethyl-3-methylene-2-silabicyclo2.1.1]hexane as the only volatile photoproduct in high yield. However, 2,4,4-trimethyl-4-sila-3-methylene-1,6-heptadiene

was found to be photochemically non-reactive under identical reaction conditions, and the 1-substituted butadienes (VI) and (VIII)

underwent cis-trans isomerism on photolysis.