Telluration of Alkenylmethyl Ketones with Aryltellurium Trichlorides: Synthetic Route and Structural Studies

It has been our endeavor to prepare organotellurium compounds bearing functionalized groups. The electrophilic substitution reactions were performed with 1-acetyl-1-cyclohexene, an alkenylmethyl ketone (cyclo-C6H9COCH3), with NpTeCl3 and MesTeCl3. The reactions were found to proceed smoothly at room temperature. The unsymmetrical functionalized arylalkyltellurium dichloride Np(cyclo-C6H9COCH2)TeCl2, 1Aa or Mes(cyclo-C6H9COCH2)TeCl2, 1Ba was obtained in good to moderate yield when the reactants were stirred for 7-8 h in absence of any solvent. The reaction with MesTeCl3 is rather slow and requires over 24 h of stirring. Biphasic (H2O/CH2Cl2) reduction of the dichlorides 1Aa or 1Ba with aqueous Na2S2O5 did not gave the expected unsymmetrical telluroether (cyclo-C6H9COCH2)-Te-Ar, instead the usual work up of the organic phase afforded the respective ditellurides, Ar2Te2. The bromo analogues of 1Aa and 1Ba, namely Ar(cyclo-C6H9COCH2)TeBr2 (Ar= 1-Np, 1Ab and Mes, 1Bb), were prepared by the metathetical reaction of the chlorides with sodium bromide (Scheme 1). The newly synthesized dihaloaryltellurated alkenyl carbonyl compounds are colourless to pale yellow crystalline solids soluble in common organic solvents and have been characterized by 1H, 13C and 125Te NMR in solution. The structural studies in the solid state for the compounds 1Aa and 1Ba have been carried out by single-crystal X-ray diffraction technique