2-(Fluoro-) and 2-(methoxyanilino)-1,4-naphthoquinones. Synthesis and mechanism and effect of fluorine substitution on redox reactivity and NMR

Abstract

Abstract The influence of catalysts on the addition of methoxy- and fluoroanilines with 1,4-naphthoquinone to give methoxy- and fluoro-substituted 2-(anilino)-1,4-naphthoquinones was investigated. In the absence of a catalyst, this reaction requires long times and low yields of the anilino derivatives are obtained accompanied with the formation of several secondary products. Excellent yields were obtained with a catalytic amount of a Lewis acid with strong oxidation properties such as CeCl3 or FeCl3. Excellent yields were also obtained when the reaction was performed with a Bronsted acid/oxidant mixture such as AcOH/Cu(OAc)2. This addition reaction was also investigated using microwave irradiation. A discussion on reaction conditions and mechanism is presented. The 1H and 13C NMR data of all the derivatives were analyzed and assigned using two dimensional 1H–13C gHSQC and gHMBC NMR experiments. The effect of fluorine substitution on redox and NMR properties was also investigated.