Gold-catalyzed cyclization of unconjugated ynone derivatives for 2H-1,2-oxazine and 1-hydroxypyrrole skeletons through one-pot and single-step strategy

Unconjugated ynone derivatives with the 1,3-dicarbonyl structure are synthesized, and they are directly subjected to goldcatalyzed reaction with hydroxylamine without obtaining the oxime derivative. Among the different metal salts investigated, AuCl3 is the best for yielding and obtaining two different heterocyclic skeletons. Thanks to this reaction, two important heterocyclic molecules, 2H-1,2-oxazine and 1-hydroxypyrrole, are obtained as a one-pot and single-step strategy with favorable yields. Eleven different 2H-1,2-oxazine and 6 different 1-hydroxypyrrole derivatives are synthesized using starting compounds containing different substituents, in which steric hindrance and electronic effect are also taken into account. When the same reaction is carried out with the unconjugated ynone derivative containing only one carbonyl group, the only 1-hydroxypyrrole derivative is observed to be formed, and 1,2- oxazine ring is not observed.