A Simple and Efficient Process for the Synthesis of Novel Heterocycles Containing Benzofuran Moiety Using Thiocarbohydrazide as a Precursor

A simple and efficient process for the synthesis of novel heterocycles starting from thiocarbohydrazide was reported. Reaction of 2‐acetylbenzofuran ( 1 ) and thiocarbohydrazide ( 2 ) in ethanol containing acetic acid produced the corresponding thiocarbohydrazone 3 in 86% yield. Reaction of 3 and isatin ( 4 ) gave N ,2‐bis(2‐oxoindolin‐3‐ylidene)hydrazine‐1‐carbothiohydrazine ( 6 ) in 65% yield, rather than the expected product, 3‐[(1‐methyl‐1‐benzofur‐2‐ylmethylidene)amino]‐1‐{[(3 Z )‐2‐oxo‐2,3‐dihydro‐1 H ‐indol‐3‐ylidene]amino}thiourea ( 5 ). Reaction of 2‐((3‐(benzofuran‐2‐yl)‐1‐phenyl‐1 H ‐pyrazol‐4‐yl)methylene)hydrazine carbothioamide ( 9 ) and chloroacetic acid or hydrazonoyl chloride 11 in basic medium gave ( Z )‐2‐(( E )‐((3‐(benzofuran‐2‐yl)‐1‐phenyl‐1 H ‐pyrazol‐4‐yl)methylene)hydrazono)thiazolidin‐4‐one ( 10 ) or 2‐(( E )‐2‐((3‐(benzofuran‐2‐yl)‐1‐ phenyl‐1 H ‐pyrazol‐4‐yl)methylene)hydrazinyl)‐4‐(( E )‐(4‐fluorophenyl)diazenyl)‐5‐methylthiazole ( 12 ) in 62% or 74%, respectively.