A NOVEL MONOALKYLATION OF SYMMETRICAL ALPHA-DIONES

An efficient method has been developed for the synthesis of monoalkyla ted 1,2-diones by using steric approach control. The dihydropyrazine 2 prepared from 2,3-butanedione and 1,2-diamino-2-methylpropane is sele ctively deprotonated on the less hindered methyl group to give an anio n which is alkylated with alkyl iodides and activated bromides. In sit u hydrolysis of the alkylated dihydropyrazines gives monoalkylated dio nes 4 in good yield. (C) 1998 Published by Elsevier Science Ltd. All r ights reserved.