REACTIONS OF A DISILENE AND A SILYLENE WITH CYCLOPENTADIENE, FURAN, AND THIOPHENE - [2+4]-CYCLOADDITIONS VERSUS CHALCOGEN ABSTRACTION

Tetra-tert-butyldisilene (2) and di-tert-butylsilylene (3), generated by photolysis of hexa-tert-butylcyclotrisilane (1), react with the double bonds of cyclopentadiene (4) to provide the [2 + 4]- and [1 + 2]-cycloaddition products 2,2,3,3-tetra-tert-butyl-2,3-disilabicyclo[2.2.1]-cyclohept-5-ene (5) and 6,6-di-tert-butyl-6-silabicyclol[3.1.0]hex-2-ene (6), which are isolated together with two rearranged ene reaction products of 4 with 2. Photolysis of 1 in the presence of furan yields exo-3,3,6,6,7,7-hexa-tert-butyl-3,6,7-trisila-8-oxatricyclo[3.2.1.0(2,4)]- octane (9) in addition to 1,1-di-tert-butyl-2,2-dimethyl-1-silacyclopropane (10) and trans-1,1,2,3,3,4-hexa-tert-butylcyclotetrasilane. Reaction of 2 and 3 with thiophene gives the sulfur abstraction product 1,1,2,2-tetra-tert-butyl-1,2-disilathiirane (13) together with 2,2,6,6-tetratert-butyl-2,6-disilabicyclo[3.1.0]hex-3-ene, 1,1,2,2-tetra-tert-butyl-1,2-disilacyclohexa-3,5-diene, and 10. The structures of 5, 9, and 13 were determined by X-ray crystallography.