Waseeq Ahmad Siddiqui

N-(X-chlorophenyl)-4-hydroxy-2-methyl-2H-1,2-benzothiazine-3-carboxamide 1,1-dioxide (with X = 2 and 4).

The structures of N-(2-chlorophenyl)-4-hydroxy-2-methyl-2H-1,2-benzothiazine-3-carboxamide 1,1-dioxide and N-(4-chlorophenyl)-4-hydroxy-2-methyl-2H-1,2-benzothiazine-3-carboxamide 1,1-dioxide, both C16H13ClN2O4S, are stabilized by extensive intramolecular hydrogen bonds. The 4-chloro derivative forms dimeric pairs of molecules lying about inversion centres as a result of intermolecular N-H...O hydrogen bonds, forming 14-membered rings representing an R2(2)(14) motif; the 2-chloro derivative is devoid of any such intermolecular hydrogen bonds. The heterocyclic thiazine rings in both structures adopt half-chair conformations.

Methyl 3-hydr­oxy-4-oxo-3,4-dihydro-2H-1,2-benzothia­zine-3-carboxyl­ate 1,1-dioxide monohydrate

In the molecule of the title compound, C10H9NO6S·H2O, the benzothiazine ring adopts an envelope conformation. An intramolecular N—H⋯O hydrogen bond results in the formation of a nonplanar five-membered ring which has a twisted conformation. In the crystal structure, intermolecular N—H⋯O, O—H⋯O and C—H⋯O hydrogen bonds link the molecules to form a three-dimensional network. There is a π–π contact between the benzene rings [centroid–centroid distance = 3.972 (2) Å].

Multilevel topological description of molecular packings in 1,2-benzothiazines

A new method for description of molecular networks and packings is proposed and implemented into the program package TOPOS. It is shown that the method is most effective in combination with the multilevel analysis of intermolecular interactions in terms of molecular Voronoi polyhedra. The method was applied to 82 1,2-benzothiazine derivatives, 11 of which we have synthesized for the first time. As a result, we have determined the main transformation routes of underlying nets, i.e. the nets of molecular centroids, at different levels of van der Waals interaction and found the most important topologies that play a key role in these routes. The method can help to create databases of topological properties of molecular packing (second-level databases) from crystallographic databases (first-level databases); this is an important step to develop predictable expert systems in materials science.

Anti-Inflammatory Oxicams as Multi-donor Ligand Systems: pH- and Solvent-Dependent Coordination Modes of Meloxicam and Piroxicam to Ru and Os

The nitrogen- and sulfur-containing 1,2-benzothiazines meloxicam and piroxicam are widely used as nonsteroidal anti-inflammatory drugs. Intrigued by the presence of multiple donor atoms and therefore potentially rich coordination chemistry, we prepared a series of organometallic Ru and Os compounds with meloxicam and piroxicam featuring either as mono- or bidentate ligand systems. The choice of the solvent and the pH value was identified as the critical parameter to achieve selectively mono- or bidentate coordination. The coordination modes were confirmed experimentally by NMR spectroscopy and single crystal X-ray diffraction analysis. Using DFT calculations, it was established that complexes in which meloxicam acts as a bidentate N,O donor are energetically more favorable than coordination as O,O and S,O donor systems. Since meloxicam and piroxicam derivatives have shown anticancer activity in the past, we aimed to compare the complexes with mono- and bidentate ligands on their in vitro anticancer activity. However, stability studies revealed that only the latter complexes were stable in [D6 ]DMSO/D2 O (5:95) and therefore no direct comparisons could be made. The meloxicam complexes 1 and 2 showed moderate cytotoxicity, whereas the piroxicam derivatives 5 and 6 were hardly active against the utilized cell lines.

4-(2-Iodo­benzene­sulfonamido)benzoic acid monohydrate

In the molecule of the title compound, C13H10INO4S·H2O, the coordination around the S atom is distorted tetrahedral. The aromatic rings are oriented at a dihedral angle of 74.18 (17)°. Intramolecular C—H⋯O hydrogen bonds result in the formation of non-planar five- and six-membered rings, which adopt envelope and twist conformations, respectively. In the crystal structure, intermolecular N—H⋯O, O—H⋯O and C—H⋯O hydrogen bonds link the molecules. π–π Contacts between the phenyl rings [centroid–centroid distance = 3.726 (3) Å] may further stabilize the structure. There is also a C—H⋯π interaction.

2-Methyl-1,2-benzisothia­zol-3(2H)-one 1,1-dioxide

All atoms of the title molecule, C8H7NO3S, except the two oxide O atoms and two H atoms of the methyl group, lie on a crystallographic mirror plane. The crystal structure is stabilized by weak inter- and intramolecular C—H⋯O hydrogen bonds.

LIGAND FREE Pd CATALYZED CYCLIZATION-INFLUENCE OF STERIC HINDRANCE

ABSTRACT Synthesis of sultams was performed using ligand free palladium catalyst following Heck cyclization. The diverse synthesized intermediates in this strategy includes halogenated sulfonyl chloride, alkyl/aryl sulfonamides, N -alkylation using halogenated alkenyl reagents followed by improved Heck cyclization with Pd(OAc) 2 /DIPA in 1-methyl-pyrolidin-2-one/toluene. In this way, isomeric six membered sultams with endocyclic & exocyclic double bonds (benzothiazine) and seven membered (thiazipene) were obtained. Endocyclic double bond isomer was dominates in respect of yield over the exocyclic double bond isomer. The isolated amounts of endocyclic sultams and thiazipene were almost equal in amounts. The intermediates and final products were characterized using IR, 1 H-NMR, 13 C-NMR and EI-MS techniques. Key words; cyclic sultams, 1,2-benzothiazine, ligand free Heck reaction e-mail: mnachemist@hotmail.com 1. INTRODUCTION Synthesis of new organic compounds is a highly cherished sector of chemistry. After the first Kolbe’s synthesis developed for construction of the carbon-carbon (C-C) bond, literature provides references like, Grignard-, aldol- and pericyclic type of reactions. Formation of C-C bond through cleavage of C-H bond

N-(2-Chloro-phen-yl)-4-hydr-oxy-2H-1,2-benzothia-zine-3-carboxamide 1,1-dioxide.

In the title compound, C15H11ClN2O4S, there are two independent molecules in the asymmetric unit, in which the heterocyclic thiazine rings in both molecules adopt half-chair conformations. The conformations about the C—C and C—N bonds in the central C—C—N—C chain in both molecules are all EZ. There are strong intramolecular O—H⋯O and N—H⋯N hydrogen bonds resulting in graph-set patterns S(6) and S(5) for the oxo and amino rings, in addition to intramolecular N—H⋯Cl interactions. In the crystal structure, molecules are linked by intermolecular O—H⋯O and N—H⋯O hydrogen bonds into chains along [100].

Sodium 2-iodo­benzene­sulfonate monohydrate

In the title compound, Na+·C6H4IO3S−·H2O, the Na atom is hexacoordinated by O atoms, forming a two-dimensional sheet-like structure in the bc plane, with the iodobenzene rings protruding above and below. Na⋯O contact distances are in the range 2.419 (2)–2.7218 (18) Å and O⋯Na⋯O angles are in the range 73.70 (5)–158.64 (7)°. The crystal structure is stabilized by O—H⋯O and C—H⋯O hydrogen bonds and C—H⋯π interactions. The I atom is disordered over two positions with occupancies of 0.78 (2) and 0.22 (2).

2,6-Dibromo-4-chloro­aniline

The title compound, C6H4Br2ClN, is almost planar (r.m.s. deviation = 0.024 Å) and two intramolecular N—H⋯Br hydrogen bonds generate S(5) rings. In the crystal, N—H⋯Br hydrogen bonds link the molecules into chains propagating in [010].