Highly regio- and stereoselective synthesis of alpha-(N-alkyl-N-p-toluenesulfonyl)-beta-bromo-ketones via Ni(OAc)2-catalyzed aminobromination of chalcones.

The combinations of N-methyl-p-toluenesulfonamide/NBS and N-ethyl-p-toluenesulfonamide/NBS were found to be good nitrogen/halogen resources for the aminohalogenation of alpha,beta-unsaturated ketones in the presence of Ni(OAc)(2) as the catalyst for the synthesis of vicinal haloamino ketone derivatives. The introduction of N-alkyl groups to the nitrogen resources resulted in excellent regio- and stereoselectivity for both electron-donating and electron-withdrawing group-attached unsaturated ketone substrates. The structure of the resulting products has been unambiguously confirmed by X-ray crystal structure analysis.

New catalytic system for aminohalogenation of beta-methyl-beta-nitrostyrenes to give opposite regiochemistry.

A new combination of catalyst and co-additive has been found for aminohalogenation reaction of beta-methyl-beta-nitrostyrenes with N,N-dichloro-p-tolunesulfonamide (4-TsNCl(2)). The reaction was achieved by using MnSO(4) as the catalyst together with tolunesulfonamide to give vicinal haloamino nitroalkanes with opposite regiochemistry to that generated from other electron-deficient olefins observed previously. The reaction proceeded smoothly at room temperature under nitrogen atmosphere to give useful to good yields and excellent regio and stereoselectivity. A mechanism involving the formation of chloronium intermediate was proposed to explain the resulting regio and stereochemistry.

Novel synthesis of 1-aroyl-3-aryl-4-substituted imidazole-2-thiones.

[reaction: see text] An efficient route to 1-aroyl-3-aryl-4-substituted imidazole-2-thiones (2, 4-6) has been developed. The methodology involves the cyclization of 1-aroyl-3-arylthioureas with a variety of carbonyl compounds bearing alpha-H in the presence of bromine and triethylamine.