Facile Telluration of Prochiral Ketones with Aryltellurium Trichlorides and Bromides

The direct interaction of aryltellurium trihalides, ArTeX3 (Ar = 1-naphthyl, A; mesityl, B; anisyl, C; X = Cl, a; Br, b) with prochiral ketones, RCH2COR' (R = Me, R' = Ph, 1; Me, 2; Et, 3; R = Et, R' = Ph, 4), at room temperature gives mixed (acylmethyl/aryl) diorganotellurium dihalides where the acylmethyl ligand bears an asymmetric carbon centre. The isomerically pure racemic mixture of aryldihalotellurated chiral ketones, RCOC*HMe(TeArX2) have been isolated in good yields except in the reaction between 1-naphthyltellurium trihalides and ethylmethyl ketone that affords a mixture of alpha-tellurated ketones with and without an asymmetric carbon. Aryltellurium triiodides do not react. The isolated products have been characterized by C, H analyses, infrared, H-1, C-13, Te-125 NMR, and mass spectral techniques. Structures of the recemates, 1Aa, 1Ba, and 3Aa and the achiral compound 2Ba determined by single crystal X-ray diffraction indicate that the carbonyl functionalized ligands invariably behave as 1,4-(C,O) chelating agent toward Te(IV) atom, at least in the solid state. The central tellurium atom among the lattices of chiral compounds achieves six coordination via intermolecular Te center dot center dot center dot X/Te center dot center dot center dot O secondary bonding interaction while it remains five coordinate in the achiral 2Ba.