title: Three novel benzothiazine-fused triazoles as potential centrally acting muscle relaxants.
abstract: The structures of the novel triazolobenzothiazines 2,4-dihydro-1H-benzo[b][1,2,4]triazolo[4,3-d][1,4]thiazin-1-one (IDPH-791), C(9)H(7)N(3)OS, (I), a potential muscle relaxant, its benzoyl derivative, 2-(2-oxo-2-phenylethyl)-2,4-dihydro-1H-benzo[b][1,2,4]triazolo[4,3-d][1,4]thiazin-1-one, C(20)H(17)N(3)O(4)S, (II), and the β-keto ester derivative, ethyl 3-oxo-2-(1-oxo-2,4-dihydro-1H-benzo[b][1,2,4]triazolo[4,3-d][1,4]thiazin-2-yl)-3-phenylpropanoate, C(17)H(13)N(3)O(2)S, (III), are the first examples of benzothiazine-fused triazoles in the crystallographic literature. The heterocyclic thiazine rings in all three structures adopt a distorted half-chair conformation. Compound (III) exists in the trans-β-diketo form. Other than N-H···O hydrogen bonds in (I) forming dimers, no formal intermolecular hydrogen bonds are involved in the crystal packing of any of the three structures, which is dominated by C-H···O/N and π-π stacking interactions.
authors.affiliation: Laboratory of X-ray Crystallography, CSIR Indian Institute of Chemical Technology, Hyderabad 500 007, India. sshiya@yahoo.com
authors.forename: Krishnan
authors.initials: K
authors.lastname: Ravikumar
authors.forename: Balasubramanian
authors.initials: B
authors.lastname: Sridhar
authors.forename: Venkatasubramanian
authors.initials: V
authors.lastname: Hariharakrishnan
authors.forename: Awadesh Narain
authors.initials: AN
authors.lastname: Singh
mesh_terms: D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008958:Models, Molecular; D015394:Molecular Structure; D009125:Muscle Relaxants, Central / Q000737:chemistry*; D013843:Thiazines / Q000737:chemistry*; D014230:Triazoles / Q000737:chemistry*
chemical_list: D009125:Muscle Relaxants, Central; D013843:Thiazines; D014230:Triazoles; C070154:IDPH-791