3,5-Dibromo-1,2,4-trithia-3,5-diborolane reacts with alkynes to give ⊿4-2-bromo-1,3,2- dithiaborolenes. As a by-product in the reaction to form ⊿4-2-bromo-4-phenyl-1,3,2-dithiaborolene the ⊿2,5-4-bromo-2,6-diphenyl-l,4-thiaboracyclohexadiene is formed. Vinyltrimethylsilane reacts with 3,5-dimethyl-1,2,4-trithia-3,5-diborolane to yield the 2-methyl-4- trimethylsilyl-1,3,2-dithiaborolane. The bromine atom in these compounds can be substituted by lithium alkyls, by secondary as well as lithiated

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... imary amines or by lithiohexamethyldisilazane. Starting from ⊿4-2-<-butylamino-4-phenyl-1,3,2-dithiaborolene and heterocycles containing boron bromine functions, diborylamines are obtained. Isocyanates and di-i-propylcarbodiimide, respectively, react with 3,5-dimethyl-1,2,4-trithia-3,5-diborolane by formation of 5-methyl-1,4-dithia-2-azacyclopentanethiones(3) or of -pentanones(3). 3,5-Dimethyl-1,2,4-trithia-3,5-diborolane reacts with o-acetylaminophenole to give 3-acetyl-2-methyi-4,5-benzo-l-oxa-3-aza-2-boracyclopentane. 1H, 11B, 13C NMR, mass and IR spectra are reported.