Synthesis of 3-Alkylcoumarins and 3-Alkyl-α,β-unsaturated δ-Lactones from 3-Diethylphosphonocoumarins, 3-Diethylphosphonolactones and Aldehydes

Abstract

The treatment of salicylaldehyde 1 and derivatives 2-4 with triethyl phosphonoacetate 5 in refluxing toluene using piperidine acetate and β-alanine affords 3-diethyl phosphonocoumarins 6-9. By hydrogenation of the compounds 6-9, 3-diethylphosphono-3,4-dihydrocoumarins 10-13 have been obtained. The compounds 10-13 react with the aromatic aldehydes 14-18, under Wittig-Horner conditions, to give 3-alkyl-coumarins 19-24 in satisfactory yields. The reaction of 3-diethyl-phosphonolactones 25, 26 with isatin 27 and 5-bromoisatin 28, under similar reaction conditions, leads to 3-alkyl-α,β-unsaturated δ-lactones 29-31