Synthesis and Molecular Structure of Ethyl-4-Hydroxy-1-Phenyl-2,2-Dioxo-1H-2λ6,1-Benzothiazine-3-Carboxylate

Methyl-4-hydroxy-1-phenyl-2,2-dioxo-1 H -2λ 6 ,1-benzothiazine-3-carboxylate was found to undergo transesterification even during crystallization from EtOH to convert into the corresponding ethyl ester. The molecular structure of the obtained compound was studied. In particular, PMR spectroscopy and x-ray crystal structure analysis established that the 1- N -phenyl substituent was situated in solution at an angle of ~60° to the plane formed by the aminophenylcarbinol fragment of the 2,1-benzothiazine whereas this angle increased to 80° in the crystal because of packing effects.