Synthesis of spiro-fused heterocycles under aerobic conditions by using polymer gel-entrapped catalyst

An expedient synthesis of spiro-fused heterocycles from multi-component reaction of urea, aryl aldehydes and Meldrum’s or barbituric acid by using polymer gel-entrapped catalyst under aerobic conditions at ambient temperature is reported. The developed protocol is simple, green, atom-economical and includes mild reaction conditions, does not involve tedious workup or purification procedure, avoids hazardous reagents/by-products and results in near-quantitative yields. The polymer gel-entrapped catalyst could be reused seven times without significant change in the catalytic activity.