Reactions of Photoexcited Carbonyl Compounds with Silanes: Mechanism and Regioselectivity
Silyl radicals, produced by hydrogen abstraction from silicon hydrides by photoexcited ketone triplets, add to the carbonyl group when the ketone do not contains other unsaturated reactive centers. If an olefinic double bond is also present, regiospecific or regiose1ective addition to the latter takes place to give the thermodynamically less stable adduct. Thermal rearrangement to the more stable adduct to oxygen, occurs only when the silyl group is attacked to a carbon atom α to the carbonyl group.
Carbonyl compounds, when photoreacted with silanes containing at least a silicon-silicon bond, are capable of bringing about displacement of a silyl radical in a fashion which is akin to the familiar homolytic substitution reaction, SH2. Strong evidence in favour of an electron transfer mechanism for this reaction is provided by the experimental results.
KeywordsCarbonyl Compound Maleic Anhydride Hydrogen Abstraction Aromatic Ketone Electron Transfer Mechanism
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