Photolysis of Diazo(pentamethyldisilanyl)methyl Ketones in the Presence of Carbonyl Compounds: Trapping of the Acylsilene Intermediates

UV photolysis of diazo(pentamethyldisilanyl)methyl ketones 1b – d generates acylsilenes (3‐oxo‐1‐sila‐1‐propenes) 3 as reactive intermediates, which can be trapped by enolizable carbonyl compounds in an ene‐type reaction. With non‐enolizable carbonyl compounds or ethyl acetate, they undergo a [4 + 2] cycloaddition. In contrast to the photolysis in the absence of these carbonyl compounds, a Wolff rearrangement of 1b – d (or the derived carbenes) to silyl ketenes 5b – d is observed as a competitive reaction.