Synthesis of new 3<i>H</i>-chromeno[2,3-<i>d</i>]pyrimidine-4,6(5<i>H</i>,7<i>H</i>)-diones <i>via</i> the tandem intramolecular Pinner/Dimroth rearrangement
8-tetrahydro-4H-chromene-3-carbonitriles with excess aliphatic carboxylic acids in the presence of phosphoryl chloride (POCl3) afforded new 2-alkyl-5-aryl-8,8-dimethyl-8,9-dihydro-3H-chromeno[2,3-d]pyrimidine-4,6(5H,7H)-diones in high yields. The suggested mechanism involves a tandem intramolecular Pinner/Dimroth rearrangement. The synthesized compounds were characterized by infrared (IR), proton nuclear