Synthesis and antibacterial activity of benzo[4,5]isothiazolo[2,3-a]pyrazine-6,6-dioxide derivatives

We have developed a simple and efficient synthetic route, starting from easily available starting materials, to the ring system benzo[4,5]isothiazolo[2,3-a]pyrazine-6,6-dioxide. A series of chalcones were synthesized which were subsequently reacted with chlorosulfonic acid to generate the chalcone sulphonyl chlorides. The chalcone sulphonyl chlorides were then treated with bromine to generate the dibromo chalcone sulphonyl chlorides. These were subsequently reacted with 1,2-diaminopropane and 2-methyl-1,2-diaminopropane in boiling ethanol resulting in compounds 2-10 and 11-19 respectively, in 12-80% yields. The products were characterized by spectral analysis and the definitive structure of compound 11 was determined by X-ray crystallography. The synthesized compounds were screened for potential antimicrobial properties against Bacillus subtilis, Escherichia coli, Proteus vulgaris and Staphylococcus aureus.