Unsaturated five-membered selenium-silicon containing heterocycles based on the reactions of selenium di- and tetrahalides with diorganyl diethynyl silanes

Reactions of SeBr2 and SeCl2 with diorganyl diethynyl silanes (RRSi)-Si-1(C CH)(2) in CHCl3 at room temperature result in regio- and stereoselective formation of a new class of unsaturated five-membered heterocycles, 4,4-R,R-1-3,6-dichloro(dibromo)-1,4-selenasilafulvenes (Z-isomers predominately), in preparative yields. Under similar conditions the reaction of SeBr4 and SeCl4 with diorganyl diethynyl silanes (RRSi)-Si-1(C CH)(2) proceeds regioselectively to afford another new class of unsaturated five-membered heterocycles, 2-dichloro(dibromo)-methyl-2,4-dichloro(dibromo)-3,3-diorganyl-1-selena-3-silacyclopentenes-4. The structures of the heterocycles were proved by multinuclear (H-1, C-13, Si-29, Se-77) NMR spectroscopy, 2D NOESY NMR spectroscopy and mass-spectrometry. A long-range spin-spin interaction of protons through five bonds lacking in E-isomers was revealed in Z-isomers of fulvene-type heterocycles. In the MS spectra heterocycles of cyclopentene structure were shown to manifest themselves as fragmentary ions [M-HX](+) or [M-X](+). (c) 2006 Elsevier B.V. All rights reserved.