Effect of the solvent and substituent in the nucleophile on the kinetics of noncatalytic and acetic or diphenylphosphinic acid-catalyzed reaction of 4-methyl-5-phenyl-2,3-dihydrofuran-2,3-dione with aromatic amines

The kinetics of reactions of 4-methyl-5-phenyl-2,3-dihydrofuran-2,3-dione w ith ethyl 4-aminobenzoate, p-bromoaniline, and aniline were studied in vari ous solvents in the absence of a catalyst and in the presence of acetic or diphenylphosphinic acid. The relation between the reaction rate and solvent properties suggests formation of a five-membered cyclic transition state i n the noncatalytic reaction and difunctional tautomeric catalysis by acids. The relation between the reaction rate and the nature of substituent in th e nucleophile indicates a greater contribution of intramolecular general ba se catalysis to the "noncatalytic" reaction, as compared with furandiones h aving no substituent in position 4. As a result, the relative activity of i ntermolecular catalysts decreases.