The Structure of 2,3-Dihydro-3-(2,4-dioxo-6-methylpyran-3-ylidene)2-(2-nitrobenzyl)-1,4-b Enzothiazine and the Problem of Orthogonal Interactions

The structure of the title compound has been determined. The compound crystallizes in the P2(1)/n space group with 4 molecules in the unit cell. The structure is consistent with previous conclusions based on NMR spectroscopy; moreover it provides new information about the conformation of the thiazine ring, the nature of the intramolecular hydrogen bond and the sulfur/nitro "orthogonal interaction". This last aspect has been examined through the use of DFT calculations on a simplified model system.