Persulfate-activated charcoal mixture: an efficient oxidant for the synthesis of sulfonated benzo[ d ][1,3]oxazines from N -(2-vinylphenyl)amides and thiols in aqueous solution.

A series of 2,4-aryl-4-((arylsulfonyl)methyl)-4 H -benzo[ d ][1,3]oxazines in good to excellent yields have directly been obtained from N -(2-vinylphenyl)amides and thiols by employing a mixture of K 2 S 2 O 8 -activated charcoal in aqueous acetonitrile solution at 50 °C. A plausible mechanism for the reaction is reported. It reveals that the reaction follows a radical pathway and the persulfate has been the oxygen source for formation of the sulfone group in the products. It is worth mentioning that this protocol utilizes an easily accessible K 2 S 2 O 8 -activated charcoal mixture and thiols, respectively, as an oxidant and sulfonylating precursors for the first time.