Study of CuSCN Catalyzed Conjugate Addition Reactions of Grignard Reagents to Substituted Chalcones with Dilithium Tetrachloromanganate and their Biological Activities

Abstract

The regioselective 1,4-addition reactions of copper thiocyanate catalyzed Grignard reagents to the substituted chalcones are reported. The homogeneous solution of dilithium tetrachloromanganate is used to transmetallate magnesium by using manganese. It adds regio-selectively to substituted chalcone derivatives and forms 1,4-addition products with higher yield under nitrogen atmosphere and at a lower temperature. It have been observed that manganese from dilithium tetrachloromanganate reagent replaces magnesium from Grignard reagent and adds regioselectively by 1,4-addition manner utilizing copper thiocyanate as a catalyst. The course of the reaction in the absence of dilithium tetrachloromanganate reagent was also studied and obtained a mixture of 1,2-addition and 1,4-addition products. In presence of dilithium tetrachloromanganate reagent, a good regio-selectivity and higher yield of desired 1,4-addition product were obtained. All the synthesized compounds were also evaluated for their antibacterial activity against Staphylococcus aureus (Gram-positive), Escherichia coli (Gramnegative) and antifungal activity against Aspergillus niger.