Synthesis of novel coumarin derivatives based on 6-aminocoumarin, kinetic inspection of base hydrolysis, and spectrophotometric tracer of intermediate progress

Abstract

The importance of 6-aminocoumarin, d-glucose, and ethyl cyanoacetate in pharmaceutical field was documented in literatures. Therefore, 6-aminocoumarin was reacted with single and double molarity of d-glucose forming Schiff’s base and bis-compound derivatives. Also, it was reacted with CS₂ in phase transfer catalysis condition producing dithiocarbamate, which was used as an intermediate for the preparation of fused and polyfused derivatives. Additionally, it was reacted with dicarbonyl compounds via the condensation reaction to give the polycarbonyl derivatives. 6-Aminocoumarin was reacted with ethyl cyanoacetate via the addition and condensation reaction mechanisms; the effect of the side chains at the stability of some of these coumarins has been recorded. The kinetics of the base hydrolysis of 6-aminocoumarin and some of its derivatives was studied spectrophotometrically in aqueous medium at 298 K under pseudo-first-order conditions ([OH⁻] >> [Compound]). The suggested general rate equation can be given as: rate = {k ₁ + k ₂ [OH⁻]} [complex]. The reasonable mechanism suggested that the investigated reaction proceeded via the formation of an intermediate and the ring opening of the formed intermediate was the rate determining step. This is the first time in which the kinetics of the formation and decay of the intermediate were followed (at [OH⁻] ≤ 3.5 × 10⁻² mol dm⁻³).

Graphical Abstract