Design, synthesis and antimicrobial activities of novel bis-Mannich bases derived from lawsone

A green and operationally simple approach for the library synthesis of novel bis-heteroarylaminomethylnaphthoquinone derivatives by a one-pot pseudo five-component domino condensation reaction of 5,5'-methylenebis(thiazol-2-amine), 2-hydroxy-1,4-naphthoquinone and various aromatic aldehydes in the presence of formic acid as the catalyst was developed. All reactions were performed in ethanol at room temperature and the products were isolated by simple filtration. The proto-col proves to be an efficient and an environmentally benign in terms of good to high yields, readily available starting materials, easy workup, clean reaction profile, mild reaction conditions, green solvent and easy purification of products without chroma-tography. Some of the newly synthesized compounds were explored for their antimi-crobial activities against two gram-positive and two gram-negative bacterial species.