An efficient method has been developed for the synthesis of monoalkylated 1, 2-diones by using steric approach control. The dihydropyrazine 2 prepared from 2, 3-butanedione and 1, 2-diamino-2-methylpropane is selectively deprotonated on the less hindered methyl group to give an anion which is alkylated with alkyl iodides and activated bromides. In situ hydrolysis of the alkylated dihydropyrazines gives monoalkylated diones 4 in good yield.
