Synthesis and Antibacterial Activity of Isochromene and Isoquinoline Derivative

Synthesis of 4-thioureidobenzoic acid (2), which on cyclization with ethyl chloroacetate gave 4-(2-imino-5-oxothiazolidin-3-yl)-benzoic acid (3), which on further reacting with benzoin (4) in the presence of polyphosphoric acid afforded the synthesis of 2-imino-3-(-1-oxo-3,4-diphenyl-1H-isochromen-6-yl) thiazolidin-5-one (5). Compound 5 was then reacted with substituted anilines to give 6-(2-imino-5-oxothiazolidin-3-yl)-3,4-diphenyl-2-(substituted)-isoquinolin-1(2H)-one (6). The structures of the compounds have been elucidated on the basis of IR 1HNMR, 13C NMR, and elemental analysis. Representative samples were screened for their antimicrobial activity against gram-negative bacteria, E. coli and P. aeruginosa and gram-positive bacteria, S. aureus, and C. diphtheriae using disc diffusion method.