SILICON-COMPOUNDS WITH STRONG INTRAMOLECULAR STERIC INTERACTIONS .52.UNEXPECTED REARRANGEMENT OF SILYLENE INSERTION INTO CYCLOADDITION PRODUCTS

Photolysis of hexamethyl-2,2-dimesityltrisilane in the presence of N-m esitylpyridine-2-aldimine (3) gives the silylene C-H insertion product 4a together with the [4 + 1] cycloaddition product 5a. Heating of nea t 4a as well as of the sterically more encumbered N-2,6-diisopropylphe nyl derivative 4b leads to an unexpected rearrangement of the C-H inse rtion products into the 1,3-diaza-2-silacyclo-4-pentene derivatives 5a ,b. The X-ray structure analysis of 5a shows that the heteroaromatic r ing of 3 has been converted into a system of conjugated double bonds.