Abstract
A series of new N-(3-ethoxycarbonyl-4,5,6,7-tetrahydrobenzo[b]thien-2-yl)-2-aryl hydrazono-3-oxobutanamide derivatives 4a-i were synthesized and the acid dissociation constants (pK(a)s) for the series prepared were determined and correlated by the Hammett-type equation using the enhanced substituent constants sigma(-)(x). The results of such correlation together with the spectral data indicated that the studied compounds exist predominantly in the hydrazone tautomeric form. Some of these derivatives exhibit high antitumor activity.