Cycloadditions of allylsilanes, part 12.(1) Regio- and stereoselective transformations of silylbicyclo[n.3.0]alkanes

Lewis acid promoted [3+2] cycloaddition of 1-acetylcycloalkenes and allylsi lanes provides the silylbicyclo[n.3.0]-alkanes 4 and 5. The sequence of reg ioselective Baeyer-Villiger oxidation and elimination of acetic acid afford s the 3-silylbicyclo[3.3.0]oct-1(5)-enes 8a and 9a and the 8-(triphenylsily l)bicycle[4.3.0]non-1(6)-ene (8b). Epoxidation and catalytic hydrogenation of these olefins proceeds with complete stereoselectivity anti relative to the silyl substituent. Ozonolysis of 8b leads to 3-(triphenylsilyl)cyclonon ane-1,5-dione(15).