Publication Details

We report an environmentally benign, sustainable protocol for the synthesis of tetrahydro-4H-chromenes via a one-pot, three-component reaction of aldehydes, cyclic 1,3-dicarbonyls, and malononitrile as well as its surrogates. Calcium lactate was employed as a readily accessible, less-toxic, inexpensive catalyst, and aqueous ethanol was taken as a green solvent to prepare the chromenes in an eco-friendly manner. Our developed protocol shows good functional group tolerance at mild reaction conditions giving good to excellent yield of the chromenes and is also capable of large-scale synthesis (at a 10 mmol scale) of chromene 4a. The control experiments support a plausible tandem Knoevenagel condensation–Michael addition pathway to form the tetrahydro-4H-chromene derivatives. The recyclability test shows a steady decrease in catalytic efficacy up to five consecutive cycles.