Facile Construction of Benzo[ d ][1,3]oxazocine: Reductive Radical Dearomatization of N -Alkyl Quinoline Quaternary Ammonium Salts.

Reductive radical dearomatization N -alkyl quinoline quaternary ammonium salts to synthesize structurally complex and challenging polysubstituted benzo[ d ][1,3]oxazocines was first reported. The mechanism showed various allyl alcohols can be converted into alkyl radicals under reduction conditions of iron/silane. These radicals then nucleophilically attack the C4 site of N -alkyl quinoline quaternary ammonium salts, and intramolecular cyclization of the resulting intermediate generates the target product. This method not only produced a series of novel polysubstituted benzo[ d ][1,3]oxazocines but also prepared polycyclic benzo[ d ][1,3]oxazocines. Finally, this strategy made up for the lack of reductive radical reports on N -alkylquinolinium salts and also had the advantages of mild reaction conditions, wide substrate range, and novel product structure.