Eco-friendly quaternization of nicotinamide and 2-bromoacetophenones in deep eutectic solvents. Antifungal activity of the products

Abstract

Most organic solvents used in quaternization reactions are volatile, hazardous, toxic and form by-products, thus inducing health issues and pollution. Deep eutectic solvents are greener alternatives, but they have not been tested yet in the quaternization reaction. Here we propose eutectic solvents in the quaternization reaction of nicotinamide with substituted 2-bromoacetophenones. The reaction was performed at 80 °C by three synthetic approaches: conventional during 2–6 h, microwave during 20 min and ultrasonic during 3 h. The highest yields of about 98% were obtained by microwave. The most suitable eutectic solvents were choline chloride with either urea, oxalic or levulinic acid. The use of deep eutectic solvents has several advantages: environmental benignity, biodegradability, easy purification and simple preparation. All tested compounds showed antifungal activities against Botrytis cinerea, Colletotrichum acutatum, Alternaria radicina and Fusarium graminearum at 10 and 100 µg/mL.