Stereoselective synthesis of (E)-(2-bromovinyl)tellurium tribromide

Abstract

There are a few published data on reactions of tellurium tetrabromide with acetylenes [1, 2]. The addition of TeBr4 to phenylacetylene and hept-1-yne was reported to give bis(2-bromo-2-phenylvinyl)tellurium dibromide and bis(2-bromohept-1-en-1-yl)tellurium dibromide in 89 and 70% yield, respectively, as mixtures of Z and E isomers, the former prevailing [1]. We have developed an efficient procedure for the synthesis of E,E-bis(2-bromovinyl)tellurium dibromide in 96% yield by reaction of tellurium tetrabromide with acetylene [2]. The reaction was carried out in chlorooform under an acetylene pressure of 12–14 atm at 40–70°C. The addition of tellurium tetrachloride to acetylene, depending on the conditions, led to the formation of both bisand monoadducts, E,E-bis(2-chlorovinyl) tellurium dichloride and E-(2-chlorovinyl)tellurium trichloride [3]. Unlike vinyltellurium trichlorides, vinyltellurium tribromides have not been reported previously. Z isomers [1, 4, 5]. We detected no possible Z-configured product in the reaction of tellurium tetrabromide with acetylene. The process was stereoselective anti-addition. Presumably, the reaction involves formation of three-membered cyclic tellurirenium intermediate, as in electrophilic anti-addition of sulfenyl and selenenyl halides to triple C≡C bond through thiirenium and selenirenium cations [6]. It is known that compounds containing a 2-bromovinyltellanyl group are used in stereoselective syntheses of alkenes via consecutive replacement of bromine and tellurium atoms by organic groups in cross-coupling reactions [4]. To conclude, we have developed an efficient procedure for the stereoselective synthesis of (E)-2-bromovinyltellurium tribromide (I) which is promising as intermediate product and building block for organic synthesis and is the first representative of previously unknown vinyltellurium tribromides. (E)-2-Bromovinyltellurium tribromide (I). Light grey powder which darkens on heating to 60–64°C and begins to decompose. H NMR spectrum, δ, ppm: 7.56 d and 7.92 d (1H each, J = 13.5 Hz). C NMR spectrum, δC, ppm: 120.04 (CHBr), 137.72 (TeCH). Found, %: C 4.88; H 0.38; Br 68.02; Te 27.45. C2H2Br4Te. Calculated, %: C 5.08; H 0.43; Br 67.54; Te 26.96. The H and C NMR spectra were recorded on a Bruker DPX-400 spectrometer at 400.13 and 100.61 MHz, respectively, using DMSO-d6 as solvent and hexamethyldisiloxane as internal reference. This study was performed in the framework of the Basic Research Program of the Russian Academy of ISSN 1070-4280, Russian Journal of Organic Chemistry, 2013, Vol. 49, No. 9, pp. 1397–1398. © Pleiades Publishing, Ltd., 2013. Original Russian Text © M.V. Musalova, V.A. Potapov, M.V. Musalov, S.V. Amosova, 2013, published in Zhurnal Organicheskoi Khimii, 2013, Vol. 49, No. 9, pp. 1413–1414.