Efficient synthesis of [1,3]thiazolo[2,3-b][1,3]oxazin-5,6,7-tricarboxylate

An efficient synthesis of 7-ethyl 5,6-dialkyl 7H-[1,3]thiazolo[2,3-b][1,3]oxazin-5,6,7-tricarboxylate is described. This involves a reaction of activated dialkyl acetylenedicarboxylates with Pyruvates in the Presence of thiazole.