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Kinetics of base-catalysed condensation of 5-methylfuran-2(3H)-one with 2-hydroxybenzaldehyde

1976; Royal Society of Chemistry; Issue: 15 Linguagem: Inglês

10.1039/p29760001773

2050-8239

Ignazio Renato Bellobono, Alma Dal Pozzo, Mario T. Cataldi,

Phosphorus compounds and reactions

Condensation of 5-methylfuran-2(3H)-one (1) with 2-hydroxybenzaldehyde (2), catalysed by triethylamine and yielding 3-acetonylcoumarin (3). was studied kinetically at 45–65°, without any solvent or with small amounts of CHCl3. Two reaction intermediates were clearly detected, as well as the formation of trans-3-(2-hydroxybenzylidene)-5-methylfuran-2(3H)-one. Concentration versus time profiles are interpreted by a scheme involving basecatalysed condensation of (1) and (2) to form an aldol, which subsequently dehydrates to give trans- and cis-3(2-hydroxybenzylidene)-5-methylfuran-2(3H)-one. The latter is finally converted into (3) by base-catalysed intramolecular acylation. The proposed kinetic scheme is also discussed on the basis of the activation parameters.