Acylanthranils. 12. Reaction of Acetylanthranil with Alcohols To Give Products of Self-Condensation

Article abstract of DOI:10.1021/jo00141a005

Material-balance studies on the reaction of acetylanthranil (I) in acidified alcohol showed that the end produt is neither the expected N-(2-carboxyphenyl)acetimidate, 3, nor the o-acetamidobenzoate ester, 4, but rather mixtures of N-(2-carboxyphenyl)-2-methylquinazol-4-one (5), o-(o-acetamidobenzamido)benzoic acid (6), CH3CO2R, and R2O, where R is the alkyl group of the alcohol.The stoichiometry in anhydrous media is consistent with the following equation: 2I + (1+2x)ROH -> (1-x)5 + x6 + CH3CO2R + xROR.Time studies of this self-condensation, monitored by proton NMR, showed that the acetimidate 3 is indeed formed as expected, but it establishes equilibrium with 1 within minutes.The acetimidate, however, reacts slowly with solvent and residual 1 to give products 5 and 6, respectively, with concomitant formation of CH3CO2R and ROR as side products.The instantaneous selectivity ratio (1-x)/x increases monotonically with percent conversion to acids 5 and 6.The disappearance of 1 in alcohol solution is pseudo first order.Initially, the rate-controlling step is the slow conversion of 3 to secondary intermediates Y and Z, but ultimately it is the subsequent very slow conversion of Y an Z to end products.