N-[(2Z,4Z)-4-Benzyl­idene-6-chloro-1,4-dihydro­pyrido[2,3-d][1,3]thia­zin-2-yl­idene]benzamide

In the crystal structure of the title compound, C(21)H(14)ClN(3)OS, mol­ecules assemble into inversion dimers via pairs of N—H⋯N hydrogen bonds involving the N—H hydrogen of the thia­zine ring and the N atom of the pyridine ring. There is a close intra­molecular contact [2.570 (2) Å] between the carbonyl O atom of the benzamide and the S atom of the puckered thia­zine ring. The title compound can exist in two tautomeric forms, viz. amino or imino. The observed structure is compatible with the imino form on the basis of observed residual electron density and the two C—N bond lengths of 1.308 (2) and 1.353 (2) Å.