Condensation Reaction of 5, 6-Dihydro-6-methyl-6-piperonyl-2H-pyran-2,4-dione, Ethyl Orthoformate and Substituted Anilines

Piperonyl methyl ketone was obtained by oxidizing isosafrole with hydrogen peroxide and formic acid. Dianion of ethyl acetoacetate reacted with piperonyl methyl ketone and 5, 6-dihydro-6-methyl-6-piperonyl-2H-pyran-2, 4-dione was prepared, which reacted with substituted anilines in the presence of ethyl orthoformate to obtain 3-anilinomethylene-5, 6-dihydro-6-methyl-6-piperonyl-2H-pyran-2, 4-diones. Their structures were confirmed by ¹HNMR and elemental analysis.