Structural Characterization of a Phenoxazine Analog Formed as a By-product of the Synthesis of a 3-Amino-N,N-dimethylsalicylamide

Abstract

A highly colored impurity formed at low levels during the preparation of 3-amino N,N-dimethyl salicylamide was isolated and identified as 2-amino-N,N,N′,N′-tetramethyl-3-oxo-3H-phenoxazin-4,6-dicarboxamide using mass spectrometry and two-dimensional NMR methods that included long-range 1H-15N heteronuclear chemical shift correlation data to assemble the proton-deficient “right-half” of the 2-aminophenoxazin-3-one nucleus. The structure was independently confirmed using computer-assisted structure elucidation methods and by synthesis.