Determination of structure and 13C chemical shift assignments of the nitration products of 2-chloro-10-methylphenothiazine. X-Ray molecular structure of 2-chloro-7-nitro-10-methylphenothiazine 5-oxide

Nitration of 2-chloro-10-methylphenothiazine, 1, yields two mono-nitro compounds identified as sulfoxide 2 and sulfone 3. The nmr analyses of the 13C spectra of 2 and 3 establish unequivocally that in both compounds substitution has occurred at the seven position. This is supported by the X-ray crystal structure of one of the compounds 2-chloro-7-nitro-10-methylphenothiazine 5-oxide, 2, which also shows that the sulfoxide group is in the “pseudo-axial” configuration. Crystals of 2 are monoclinic, space group P21/n, a = 11.606(4), b = 13.970(4)A, c = 9.837(2), β = 127.49(2)° and Z = 4. The structure has been refined by full-matrix least-squares to R = 0.033 and Rw = 0.035, using 1704 observed reflections.