Cyanoacetylazoles and salicylic aldehydes promoting the synthesis of new trifluoromethyl-substituted azolecarbonyl-2H-chromen-2-ones through the Knoevenagel condensation reaction

The results of the chemical behavior of three substituted cyanoacetylazoles and some salicylic aldehydes used to obtain new trifluoromethylated azolecarbonyl-2H-chromen-2-ones through Knoevenagel condensation reactions, are reported. First, a new series of four 3-(5-hydroxy-3-methyl-5-trifluoromethyl-4,5-dihydro-1H-pyrazole-1-carbonyl)-2-imino-2H-chromenes were efficiently synthesized, in yields of 50-78%, using 0.4 M NaOH/EtOH as the catalyst. They were then subjected to an acid hydrolysis reaction, which produced the respective trifluoromethyl-substituted pyrazolinecarbonyl coumarins in good yields (80-91%). In order to study the influence of the CF3 substituent, reactions involving 1-cyanoacety1-3,5-dimethyl-5-hydroxy-4,5-dihydro-1H-pyrazole were also performed, but they did not provide the desired coumarins. On the other hand, attempts to synthesize some pyrrolecarbonyl coumarins not containing trifluoromethylgroups, but using the same methodology, directly resulted in a new series of five 3-(1-methyl-1H-pyrrol-2-carbonyl)-2H-chromen-2-ones in good yields (40-60%). (C) 2015 Elsevier B.V. All rights reserved.