Studies on pyrazines. 29. High regioselective synthesis of chloropyrazines from 3‐substituted pyrazine 1‐oxides

Abstract Reaction of 3‐methoxy‐ or 3‐chloropyrazine 1‐oxides with refluxing phosphoryl chloride in the presence of amine led to a high regioselective formation of 3‐substituted 2‐chloropyrazines. In contrast, the use of chloroacetyl chloride instead of phosphoryl chloride enabled different regioselectivity to yield 6‐substituted 2‐chloropyrazines, particularly 3‐methoxycarbonylpyrazine 1‐oxide was almost exclusively converted into methyl 6‐chloropyrazinecarboxylate under the conditions without the amine.