Synthesis of tricarbonylated propargylamine and conversion to 2,5-disubstituted oxazole-4-carboxylates.

The ,-acetal derived from diethyl mesoxalate (DEMO) undergoes elimination of acetic acid upon treatment with a base, leading to the formation of -acylimine in situ. Lithium acetylide readily attacks the imino group to afford ,1,1-tricarbonylated propargylamines. When the resulting propargylamine reacts with butyllithium, ring closure occurs between the ethynyl and carbamoyl groups, yielding 2,5-disubstituted oxazole-4-carboxylates.

Synthesis of Bis(functionalized) Aminals via Successive Nucleophilic Amidation and Amination.

The central carbonyl group of diethyl mesoxalate (DEMO) exhibits high electrophilicity that allows it to be attacked by versatile nucleophiles. Even a less nucleophilic acid amide serves as a nucleophile to produce ,-acetal upon treatment with DEMO in the presence of acetic anhydride. When the obtained ,-acetal was treated with a base, the elimination of acetic acid generated -acylimine in situ.