Oxidative synthesis of benzo[1,4]oxazines from α-branched primary amines and ortho-benzoquinones

Facile approach to N,O,S-heteropentacycles via condensation of sterically crowded 3H-phenoxazin-3-one with ortho-substituted anilines

A convenient method for the synthesis of a series of 2-(arylamino)-3H-phenoxazin-3-ones based on the nucleophilic substitution reaction between sterically crowded 3H-phenoxazin-3-one and arylamines performed by short-term heating of the melted reactants at 220-250 °C is described, and the compounds were characterized by means of single-crystal X-ray crystallography, NMR, UV-vis, and IR spectroscopy, as well as cyclic voltammetry. The reaction with o-amino-, o-hydroxy-, and o-mercapto-substituted arylamines widened the scope and provided an access to derivatives of N,O- and N,S-heteropentacyclic quinoxalinophenoxazine, triphenodioxazine and oxazinophenothiazine systems.

A new heteropentacyclic system via coupling sterically crowded o-benzoquinone with o-phenylenediamines

The reaction between 3,5-di(tert-butyl)-o-benzoquinone 1 and o-phenylenediamine performed under oxidative conditions that is highly sensitive to the reaction conditions (type of solvent, ratio of reactants, and duration of the reaction) gives rise to various derivatives of a new condensed 10H-quinoxalino[3,2,1-kl]phenoxazin-10-one heteropentacyclic system. The reaction of 1 with N-phenyl-o-phenylenediamine results in the formation of three phenazine-like compounds and, unexpectedly, a derivative of a new spiro[1,3]dioxole-2,2'-furanyl-1H-benzo[d]imidazole system. The molecular structures of the prepared compounds were authenticated by NMR, mass spectra and X-ray crystallography data.

Condensation-Based Methods for the C-H Bond Functionalization of Amines

This review aims to provide a comprehensive overview of condensation-based methods for the C-H bond functionalization of amines that feature azomethine ylides as key intermediates. These transformations are typically redox-neutral and share common attributes with classic name reactions such as the Strecker, Mannich, Friedel-Crafts, Pictet-Spengler, and Kabachnik-Fields reaction, while incorporating a redox-isomerization step. This approach provides an ideal platform to rapidly transform simple starting materials into complex amines.