(Trimethylsilyl)diazomethane (TMS-CHN2) reacts smoothly with cycloaliphatic thioketones as well as with fluorene-9-thione at low temperature to give the corresponding 1,3,4-thiadiazole derivatives as product of a regioselective [3+2]-cycloaddition. In the first case, the obtained cycloadducts are relatively stable and eliminate N2 upon heating at 40ºC. In the second case, N2-extrusion occurs already at –40ºC. The silylated thiocarbonyl S-methanides generated thereby can be trapped regioselectively with ferrocenyl hetaryl thioketones to give the sterically crowded 2-silylated 4,4,5,5-tetrasubstituted 1,3-dithiolanes. Without isolation, these products are desilylated with TBAF and tetrasubstituted ethenes or dibenzofulvenes are obtained as final products via cycloelimination (‘[3+2]-cycloreversion’) of the intermediate 1,3-dithiolane carbanion.