Addition of tellurium tetrachloride

This section will focus primarily on a comparison of these ring systems with their heavier chalcogen analogues. The first selenium derivative benzo-l,2,5-selenadiazole was prepared more than 115 years ago by the condensation reaction of selenium dioxide with 1,2-diaminobenzene (Eq. 11.12) and other benzo derivatives may be prepared in a similar manner. The parent 1,2,5-selenadiazole has also been reported. This reagent has been employed to make the tellurium analogue via treatment with ethylmagnesium bromide followed by the addition of tellurium tetrachloride (Eq. 11.13). ... 

The addition of tellurium tetrachloride to alkenes produces chloroalkyltellurium trichlorides. Butenes, 1-decene, cycloalkenes, and 3-substituted 1-propenes give mixtures of syn and anti additions. ... 

The addition of aryltellurium trichlorides to alkenes occurs with a high stereospecificity, giving exclusively anfi-2-chloroalkyltellurium dichlorides, " in contrast to the addition of tellurium tetrachloride which gives mixtures of syn and anti adducts... 

By treatment of (Z)-2-chlorovinyltellurium trichlorides, easily obtained by addition of tellurium tetrachloride to phenylacetylenes (see Section 3.16.2.1), with 1-2 mol equiv of iodine or Af-bromosuccinimide-aluminium trichloride, a halogenodetelluration occurs, generating the corresponding (Z)-iodo- or (Z)-bromochloroalkenes. °... 

The reduction of alkyl tellurium trihalides is a convenient method for the preparation of the corresponding dialkyl ditellurium when the trihalides can be obtained by reactions other than the halogenolysis of the dialkyl ditellurium. Addition of tellurium tetrachloride to olefins and condensation with ketones produces alkyl tellurium trichlorides. Sodium sulfide nonahydrate4 and sodium or potassium disulfite5 8 were used as reducing agents. 

The reaction of tellurium tetrachloride with 3-acyloxypropenes in chloroform takes a course different than the reaction with propene. The products obtained from 3-acyloxypropenes are l-chloro-2-acyloxy-3-propyl tellurium trichlorides. These reactions proceed via syn-addition of tellurium tetrachloride with concomitant migration of the acyloxy group to the middle carbon of the propene7. 

Chloroethyl tellurium trichlorides heated with sodium sulfide nonahydrate to 100° formed ethenes2,4. The detelluration step is a slereospecific /rani-elimination, which, together with the syn-addition of tellurium tetrachloride to the olefin, results in an inversion of the olefin4. 

Diorgano tellurium dihalides are often the primary products of reactions producing compounds with two tellurium-carbon bonds. Such reactions arc the condensation of tellurium tetrachloride with aromatic compounds (p. 527), the addition of tellurium tetrachloride or organo tellurium trichlorides to carbon-carbon multiple bonds (p. 530, 544), and the alkylation or arylation of organo tellurium trihalides (p. 549). The symmetrical and unsymmetrical diorgano tellurium dihalides are convenient starting materials for the preparation of diorgano tellurium derivatives. 

Olefins with a hydroxyl group in the y- or -position to the double bond cyclize after addition of tellurium tetrachloride with elimination of hydrogen chloride7. 

Addition of tellurium tetrachloride to 2,2-diphenylpent-4-en-1-oic acid followed by hydrogen chloride elimination produced bis[3,3-diphenyl-2-oxotetrahydrofuran-5-yl-methyl tellurium, dichloride2. 

Essentially all the reactions so far reported which result in the formation of a C—Tc bond at a stereogenic carbon center involve addition of tetravalent perhalotellurium compounds (see also Houben-Weyl Vol. E12b, p299ff) to alkenes. The earliest report which examined the stereochemical aspects of such additions found that addition of tellurium tetrachloride and aryltellurium trichloride to cyclohexene affords (1,S, 2,S )-2-chlorocyclohexyltellurium trichloride (1) and aryl(lS, 2S )-2-chlorocyclohexyl]tellurium dichloride 2, respectively85 86. 

The overwhelming preference for svn addition in all cases where the radical inhibitor is present (except for cyclohexene) suggests a mechanism in which syn addition of tellurium tetrachloride in a more or less concerted addition of the elements of chlorine and lellurium(lll) chloride is competing with a radical reaction. 

However, when acetonitrile is used as the solvent, high preference for. syn addition of tellurium tetrachloride is observed for (E)- and (Z)-2-butene, even without a radical inhibitor. This result shows that the radical pathway is strongly disfavored when this solvent is used. 

It must be pointed out, however, that the addition of tellurium tetrachloride to olefins lacks generality, and undefined results have been mentioned such as formation of tarry products, reduction to elementary tellurium, or no reaction at all. ... 

One of the most general methods for synthesis of RTeXs is addition of tellurium tetrachloride (TeCLi.) to a variety of carbon-carbon unsaturated compounds such as alkenes and alkynes [68]. TeCh also reacts with aromatic compounds to afford the corresponding substitution products, arenetellurium trichlorides (Ar li f. ,), in good yields (Scheme 15.24) [69]. 

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