Studies on pyrazines. 13 . Chlorination of 1‐hydroxy‐2(1 H )‐pyrazinones with phosphoryl chloride. Formation of 2,5‐dichloro‐3‐phenylpyrazine from 1‐hydroxy‐3‐phenyl‐2(1 H )‐pyrazinone

The chlorination of 1‐hydroxy‐3‐phenyl‐2(1 H )‐pyrazinone with phosphoryl chloride proceeded to 5‐chloro‐3‐phenyl‐2( H )‐pyrazinone or 2,5‐dichloro‐3‐phenylpyrazine on heating to elevated temperatures. To define the mechanism of the novel formation, reactions of the parent or methyl‐substituted 1‐hydroxy‐2(1 H )‐pyraz‐inones with the same reagent were investigated.