Novel reactions of carbon suboxide. Part 8. Kinetic study of the reaction with substituted 2-hydroxybenzaldehyde oximes
Abstract
The kinetics of the reaction of carbon suboxide with aryl-substituted 2-hydroxybenzaldehyde oximes to give coumarin derivatives have been studies. A Hammett plot gave a ρ value of ca.–1.5, indicating that the reaction was promoted by electron-releasing groups para to the oxime function. Increasing the dielectric constant of the solvent raises the reaction rate; we have therefore proposed the formation of an ionic intermediate, after fast attack of carbon suboxide on the phenol hydroxy group.