A green method for the direct precipitation of 3-methylpyrido[2,3-b]pyrazin-2(1H)-one and 2-methylpyrido[3,4-b]pyrazin-3(4H)-one from ethyl lactate solutions

Green methods for synthesizing pyridopyrazinones were developed due to their usefulness as scaffolds in the design of therapeutic compounds. Reaction conditions using aqueous ethyl lactate solutions were optimized to maximize yields through direct product precipitation. Two key scaffolds, 3-methylpyrido[2,3-b]pyrazin-2(1H)-one and 2-methylpyrido[3,4-b]pyrazin-3(4H)-one, were obtained in yields of 88 % and 85 %, respectively. The highest yields were achieved using 92:8 and 99:1 ethyl lactate:water mixtures, with the latter including 1.5 mol% lactic acid at 35 °C. These results are comparable to traditional syntheses using anhydrous chloroform but offer a more sustainable alternative by avoiding hazardous solvents.