A highly efficient synthesis of the potent CDKs (cyclin-dependent kinases) inhibitors, aloisines (substituted 5H-pyrrolo [2, 3-b] pyrazines) is presented. The method is based on highly selective monosubstitution of a single chlorine atom in 2, 3-dichloropyrazine with lithiated ketones, esters, and nitriles followed by co-cyclization of the resulting intermediates with primary amines or hydrazines.