Preparation using Other Sulphenylation, Selenenylation, and Tellurenylation Reagents

Preparation of Sulphides Selenides, and TeUurides using Other Sulphenylation, Selenenylation, and Tellurenylation Reagents.—Sulphenamides are effective reagents for cr-heteroarylsulphenylation of ff-keto-esters. Sulphenamide intermediates are thought to be involved in the asymmetric 2-phenylsulphenylation of 4-alkylcyclohexanones in moderate optical yields, using a benzenesulphenyl halide with a chiral secondary alkylamine.  

Thiolsulphonates are effective in sulphenylation reactions, having been used recently for the stereoselective synthesis of allyl vinyl sulphides from RCH=CH-AlBu jBu . Mild reaction conditions are called for in the sulphenylation of active-methylene compounds by (ArS02)2CHSS02Ph.  

Alkyl potassium xanthates R OCSSK react with organic halides R X to give sulphides R SR (R = Et, R = 4-trifluoromethyl-2,6-dinitrophenyP and R, R are various alkyP ). Under phase-transfer conditions, this is an efficient one-pot synthesis of unsymmetrical sulphides.  

Preparation of Sulphides, Selenides, and Tellurides using the Elements Themselves, or Other Inorganic Sulphur, Selenium, and Tellurium Compounds.—Symmetrical sulphides can be obtained in 12—66% yields from an alkyl chloride, sulphur, and NaOH in DMSO. The same system with a bePxZyl cyanide R PhCHCN produces the unsymmetrical sulphides R PhC(CN)SR with an alkyl halide some 

Selenides and tellurides are formed through the reaction sequences PhCH2MgCl + Seg PhCH2SeMgCl, which with RN2 Cl -+ PhCHjSeR, and thiophens + Tcg + Mel thienyl methyl tellurides. Unexpected selenide by-products have, paradoxically, become common in oxidations by Se02, and the selenides (9) and (10) accompany the expected 1,2-diketone in the oxidation of (8) with Se02 in dioxan.  

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