Metal‐Free [4+2] Annulation of Arylalkynes with tert‐Butyl Nitrite through C(sp²)H Oxidation to Assemble Benzo[e][1,2]oxazin‐4‐ones

A metal‐free radical‐mediated [4+2] annulation of internal arylalkynes with tert ‐butyl nitrite ( t‐ BuONO) is presented for the synthesis of benzo[ e ][1,2]oxazin‐4‐ones through the addition of t‐ BuONO across the CC triple bond, hydration, isomerization and aromatic C( sp 2 )H oxidation cascades. The 18 O‐labeling experiment shows that two oxygen atoms in the product system are from water. magnified image