Three-component, simple and one-pot reaction between 4-hydroxy coumarin with aromatic aldehydes and 1-ethyl-5-amino-pyrazole in the presence of iodine

We reported a three-component, simple, one-pot and efficient method for the synthesis of pyrazolopyridocoumarin derivatives from the condensation of 4-hydroxycoumarin, aryl aldehydes and 1-ethyl-5-amino-pyrazole in the presence of iodine (I2) as catalyst under reflux. The structure of compounds 4a-f is deduced from their IR, 1H, and 13C NMR spectra. This new protocol offers advantages such as simply available starting materials, easy and clean work-up, and use of an inexpensive and non-toxic catalyst, high yields of biological active products and does not involve any hazardous solvent. Therefore, this procedure could be classified as green chemistry. Fused polyheterocycles are an important class of organic molecule because of their wide spread applications as pharmaceutical candidates, optical materials, florescence dyes and sensors. In recent times, the use of molecular iodine has received considerable attention as an inexpensive, nontoxic, readily available catalyst for various organic transformations to afford the corresponding products in excellent yields with high selectivity.