One-Pot Microwave-Assisted Synthesis of a Benzopyrano[2,3-c]pyrazol-3(2H)-one Library

A Simple Efficient Procedure for the Synthesis of Benzopyrano[2,3‐c]pyrazoles

“…Elemental microanalyses were performed on an EA1112 analyzer from CE Instruments (Thermo Scientific, Waltham, MA) at the “Service Commun de Microanalyse de l'ENCIACET.” Mass spectra were recorded on a DSQII ThermoFisher spectrometer (Thermo Fisher Scientific, Waltham, MA) using chemical ionization with ammonia (positive mode) and chloroform as solvent. 3‐Cyano iminocoumarins 1 , 2 , 3 , 4 , 5 , 6 were prepared according to the Knoevenagel procedure as previously described .…”

“…The main method reported for their synthesis was that condensed arylhydrazines with 4‐hydroxy coumarins acylated in the 3‐position, but it was limited by low overall yield and poor accessibility to required starting materials . More recently, Gorobets et al have reported that refluxing of 3‐amido hydrazonocoumarins in DMF in the presence of acetic anhydride allowed the synthesis of the corresponding benzopyrano[2,3‐ c ]pyrazoles, which can be also obtained in one pot under microwave conditions from 2‐iminocoumarin‐3‐carboxamides and hydrazines . Le Marechel et al have described that the condensation of hydroxylic 3‐cyano iminocoumarins and aromatic hydrazines in acetic acid in the presence of sodium acetate led not to benzopyranopyrazoles but to the corresponding N ‐arylamino 3‐cyano iminocoumarins.…”