AbstractThe photolyses and thermolyses of the α,β‐epoxy silyl ketones5and6are described. On n,π*‐excitation, the silyl ketones5and6were transformed to the ketone7and the ketene8in quantitative yield. The formation of8may be explained by initial cleavage of the C(α)O bond and subsequent C(1)→C(2) migration of the (t‐Bu)Me2Si group. In contrast to the acylsilanes5and6, the photolyses of the analogous methyl ketones11and12gave a very complex mixture of products. On thermolysis,5and6yielded the ketone7and the acetylenic compound9, which were probably formedviaa siloxycarbene intermediate. In addition, the 1,3‐dioxle10was formedviaan initial C(α)C(β) bond cleavage leading to the ylidegand subsequent intramolecular addition of the carbonyl group. The analogous 1,3‐dioxole13was obtained on pyrolysis of the