PHOTOCHEMISTRY OF ACYLDISILANES

The new acyldisilanes Me3SiSiR'2COAd (R' = Ph, Mes) were prepared by coupling of the appropriate disilyl lithium or potassium reagent with adamantylcarbonyl chloride. Photolyses of the compounds in deuteriobenzene and in the presence of methanol were studied. In the presence of methanol the phenyl compound gave products from the trapping of the anticipated silene and disiloxycarbene, as well as products of radical recombination. Photolysis in C6D6 gave three dimers, two of which were a cis-trans pair of alkenes resulting from the initially formed silene undergoing cycloaddition with its parent unphotolyzed acyldisilane, followed by rearrangement. The third dimer was relatively unstable, being the head-to-head dimer of the silene. At room temperature, the dimesitylacyldisilane gave only a silaindane, even in the presence of methanol, while at -78-degrees-C in addition to the silaindane, products of radical recombination and from trapping of a disiloxycarbene were obtained. Under no circumstances was the expected silene or its methanol-trapping product observed. These results are interpreted.