Reaction of Salicylamine with α-Dicarbonyl Compounds. II. Formation of 2,2′-Bibenz-1,3-oxazines

Abstract
The compounds of a new type, 2,2′-bibenz-1,3-oxazine and its derivatives have been synthesized by the reactions of salicylamines with glyoxal or α-diketones in methanol at a temperature lower than 20°C. The oxazine structures were confirmed by infrared spectroscopy in solid state and by NMR spectroscopy in CCl4, CDCl3 and chlorobenzene. An oxazine-Schiff base equilibrium was observed in pyridine and in hot chlorobenzene by NMR spectra. It was found that hydrolytic decomposition of 2,2′-dimethyl-2,2′-bibenzoxazine leads to the formation of salicylidenesalicylamine through transamination. The mechanisms were investigated spectrophotometrically.