1,1-diethynylsilacycloalkanes and propellanes based thereon

Previously unknown 1,1-diethylnylsilacycloalkanes (CH2)(n)Si(C=CH)(2) (n = 3, 4) were prepared by the reaction of HC=CMgBr with 1,1-dichlorosilacycloa lkanes (CH2)(n)SiCl2 (n = 3, 4). The reaction of (CH2)(4)Si(C=CMgBr)(2) wit h (CH2)(4)SiCl2 in THF under conditions of high dilution gives cyclo(tetram ethylene)silethynes [(CH2)(4)SiC=C](4) with an admixture of cyclodi(tetrame thylene)silethyne [(CH2)(4)SiC=C](2), The reaction of Me2Si(C=CSiMe2C=CMgBr )(2) with (CH2)(4)SiCl2 was used to prepare 1,1,4,4,7,7-hexamethyl-10,10-te tramethylene-1,4,4,10-tetrasilacyclododeca-2,5,8,11-tetrayne.