Proton tautomerism and stereoisomerism in 5-[(dimethylamino)methylidene]-4-[3/4-(trifluoromethylphenyl)amino]-1,3-thiazol-2(5H)-ones: synthesis, crystal structure and spectroscopic studies.

5-[(Dimethylamino)methylidene]-4-{[3-(trifluoromethyl)phenyl]amino}-1,3-thiazol-2(5H)-one and the [4-(trifluoromethyl)phenyl]amino derivative, both C13H12F3N3OS, with the trifluoromethyl group substituted at the arene ring at the meta and para positions, were synthesized to study the structural changes associated with proton tautomerism of the amidine system. The studied compounds were found to be in the amine tautomeric form in both the solid and the liquid (dimethyl sulfoxide solutions) phase. In both isomers, the [(trifluoromethyl)phenyl]amino residue assumes a synperiplanar conformation with respect to the thiazolone system, while the 5-[(dimethylamino)methylidene] residue adopts the Z configuration. Density functional theory (DFT) calculations correctly predicted that the synperiplanar arrangement is favoured in both isomers. In the crystal, the whole independent molecule of the para compound is disordered over two alternative positions, with occupancy factors of 0.926 (3) and 0.074 (3).

Proton tautomerism in 5-dimethylaminomethylidene-4-(o-,m-,p-hydroxyphenyl)amino-1,3-thiazol-2(5H)-ones: synthesis, crystal structure and spectroscopic studies.

Three new 5-dimethylaminomethylidene-4-phenylamino-1,3-thiazol-2(5H)-ones with an hydroxyl group in the ortho, meta and para positions on the phenyl ring were synthesized in order to deduce the structural changes occurring on prototropic tautomerism of the amidine system. The existence of all the title compounds solely in the amino tautomeric form has been established in the solid and liquid (dimethyl sulfoxide solution) phases. The title compounds are analyzed from the point of view of the electronic effects and conformational freedom of their molecules. The intermolecular interactions in the crystals and their supramolecular architecture are highlighted.

Toward a new type of proton conductor based on imidazole and aromatic acids.

A new approach towards achieving proton conducting materials based on aromatic acids and heterocyclic bases was proposed. It can lead to a new material in which all hydrogen bonding interactions are of medium or weak strength and rotations of the base and acid molecules are possible. If the above conditions are met, one can expect a high value of proton conductivity governed by the Grotthuss mechanism. Two salts of imidazole, one with benzoic acid having one carboxylic acid group and another with salicylic acid having a carboxylic and hydroxyl group located in the ortho position, were synthesized. Physical properties of these newly synthesized proton conducting salts were investigated using experimental and theoretical methods. The structures of these salts were studied by X-ray diffraction and 1H and 13C NMR techniques. The intermolecular interactions in the salts were analyzed by DFT calculations, within the QTAiM theory, and by Hirshfeld surface analysis. The π-π interactions, the proton conduction pathways, and the transport mechanism are also discussed.

1,2-Benzoxathiin-4(3H)-one 2,2-dioxide - new enol nucleophile in three-component interaction with benzaldehydes and active methylene nitriles.

The reactivity of 1,2-benzoxathiin-4(3H)-one 2,2-dioxide was studied in multicomponent type reactions for the first time, namely, in a three-component interaction with active methylene nitriles and aromatic aldehydes in order to construct condensed 2-amino-4H-pyran derivatives. The reaction outcome strongly depended on the nature of an active methylene nitrile and an arenecarbaldehyde. Application of malononitrile resulted in novel 2-amino-4-aryl-4H-pyrano[3,2-c][1,2]benzoxathiine-3-carbonitrile 5,5-dioxides in most cases, whereas the utilization of ethyl cyanoacetate resulted in a complex mixture of products. In the last case, three different products were isolated depending on the arenecarbaldehyde used, namely ethyl 2-amino-4-aryl-4H-pyrano[3,2-c][1,2]benzoxathiine-3-carboxylate 5,5-dioxides, ethyl 2-cyano-3-arylacrylates, and salts of 3,3'-(arylmethylene)bis(4-hydroxybenzo[e][1,2]oxathiine 2,2-dioxides). Attempts to obtain separately ethyl 2-amino-4-aryl-4H-pyrano[3,2-c][1,2]benzoxathiine-3-carboxylate 5,5-dioxides enabled us to propose reaction pathways leading to these products. The salts were obtained for the first time. The preparative method for the synthesis of triethylammonium salts of 3,3'-(arylmethylene)bis(4-hydroxybenzo[e][1,2]oxathiine 2,2-dioxides) was proposed by the direct interaction of 1,2-benzoxathiin-4(3H)-one 2,2-dioxide with arenecarbaldehydes. The application of ammonium acetate as a catalyst allowed us to synthesize 7-aryl-7,14-dihydrobenzo[5,6][1,2]oxathiino[4,3-b]benzo[5,6][1,2]oxathiino[3,4-e]pyridine 6,6,8,8-tetraoxides containing a novel heterocyclic system. These facts, combined with our past investigations, allowed us to assert that the reactivity of enol nucleophiles that include the COCH2SO2X fragment has not been reported previously.

NEW HETEROCYCLIC OXIME ETHERS OF 1-(BENZOFURAN-2-YL)ETHAN- 1-ONE AND THEIR ANTIMICROBIAL ACTIVITY.

In this study, some O-benzyl (benzofuran-2-yl)ethan-1-one ether oximes were synthesized starting from 2-acetylbenzofuran. The structure elucidation of the compounds was performed by IR, 1H-NMR and 13C-NMR spectra. Antimicrobial activities of the compounds were examined and notable activity was observed.

Heterocyclic tautomerism: reassignment of two crystal structures of 2-amino-1,3-thiazolidin-4-one derivatives.

The structures of 5-(2-hydroxyethyl)-2-[(pyridin-2-yl)amino]-1,3-thiazolidin-4-one, C10H11N3O2S, (I), and ethyl 4-[(4-oxo-1,3-thiazolidin-2-yl)amino]benzoate, C12H12N2O3S, (II), which are identical to the entries with refcodes GACXOZ [Vána et al. (2009). J. Heterocycl. Chem. 46, 635-639] and HEGLUC [Behbehani & Ibrahim (2012). Molecules, 17, 6362-6385], respectively, in the Cambridge Structural Database [Allen (2002). Acta Cryst. B58, 380-388], have been redetermined at 130 K. This structural study shows that both investigated compounds exist in their crystal structures as the tautomer with the carbonyl-imine group in the five-membered heterocyclic ring and an exocyclic amine N atom, rather than the previously reported tautomer with a secondary amide group and an exocyclic imine N atom. The physicochemical and spectroscopic data of the two investigated compounds are the same as those of GACXOZ and HEGLUC, respectively. In the thiazolidin-4-one system of (I), the S and chiral C atoms, along with the hydroxyethyl group, are disordered. The thiazolidin-4-one fragment takes up two alternative locations in the crystal structure, which allows the molecule to adopt R and S configurations. The occupancy factors of the disordered atoms are 0.883 (2) (for the R configuration) and 0.117 (2) (for the S configuration). In (I), the main factor that determines the crystal packing is a system of hydrogen bonds, involving both strong N-H...N and O-H...O and weak C-H...O hydrogen bonds, linking the molecules into a three-dimensional hydrogen-bond network. On the other hand, in (II), the molecules are linked via N-H...O hydrogen bonds into chains.

1-(1-Benzo-furan-2-yl)ethanone O-(2,6-di-fluoro-benz-yl)oxime.

In the title compound, C17H13F2NO2, the 2,2-di-fluoro-benz-yloxy residue assumes an E configuration with respect to the benzo-furan system. The benzene ring makes a dihedral angle of 61.70 (4)° with the fused ring system (r.m.s. deviation = 0.008 Å). In the crystal, mol-ecules are connected by weak C-H⋯F hydrogen bonds into chains extending parallel to the b-axis direction.

2-{[5-(Pyridin-4-yl)-4-p-tolyl-4H-1,2,4-triazol-3-yl]meth-yl}acrylic acid hemi-hydrate.

The asymmetric unit of the title compound, 2C18H16N4O2·H2O, consists of two organic molecules and one solvent molecule. The symmetry-independent organic mol-ecules have slightly different conformations: the 1,2,4-triazole ring forms dihedral angles of 84.61 (4), 89.68 (5) and 22.38 (6)°, respectively, with the 2-propenecarbocylic, p-tolyl and 4-pyridyl groups in one independent molecule, and 71.35 (4), 82.13 (5) and 24.82 (6)°, respectively, in the second. In the crystal, mol-ecules ralated by the 21 screw axes are assembled via O-H⋯N and O-H⋯O hydrogen bonds into infinite chains and these are linked by further O-H⋯N hydrogen bonds into undulating sheets parallel to the bc plane. Adjacent sheets are connected by weak C-H⋯O inter-actions, forming a three-dimensional structure.

2-[N-(2,4-Dimeth-oxy-phen-yl)acetamido]-1,3-thia-zol-4-yl acetate.

The title compound, C15H16N2O5S, is a product of the reaction of 2-(2,4-dimeth-oxy-phenyl-amino)-1,3-thia-zol-4(5H)-one with acetic anhydride. The presence of the acetyl and acet-oxy groups in the mol-ecule indicates that the starting thia-zole exists as a tautomer in the reaction mixture with exocyclic amino and enol moieties. The acetyl group is tilted slightly from the heterocyclic ring plane [dihedral angle = 4.46 (11)°], while the acet-oxy group is almost perpendicular to this ring [dihedral angle = 88.14 (12)°]. An intra-molecular acet-yl-meth-oxy C-H⋯O inter-action is noted. In the crystal, mol-ecules are connected into a three-dimensional architecture by C-H⋯O inter-actions.

2-[N-(4-Meth-oxy-phen-yl)acetamido]-1,3-thia-zol-4-yl acetate.

The structural analysis of the title compound, C14H14N2O4S, particularly the presence of an acetyl group at the exocyclic N atom and the C(H)-C(O2CMe)-N acet-oxy group in the thia-zole ring, may indicate that one of the starting materials, i.e. 2-(4-meth-oxy-anilino)-1,3-thia-zol-4(5H)-one, exists in the reaction mixture, at least partially, as a tautomer with an exocyclic amine N atom and an enol group. The acet-oxy and acetyl groups deviate from the thia-zole plane by 69.17 (6) and 7.25 (19)°, respectively. The thia-zole and benzene rings form a dihedral angle of 73.50 (4)°. In the crystal, centrosymmetrically related mol-ecules are connected into dimeric aggregates via C-H⋯O inter-actions.

1-(1-Benzofuran-2-yl)ethanone O-(4-chloro-benz-yl)oxime.

In the title compound, C(17)H(14)ClNO(2), the p-chloro-benz-yloxy residue assumes an E conformation with respect to the benzofuran system. The carbo- and heterocyclic systems make a dihedral angle of 47.99 (4)°. In the crystal, there are no significant intermolecular interactions present.

3ß-Acet-oxy-12α-chloro-d-friedooleanan-28,14ß-olide.

The title compound, C(32)H(49)ClO(4), was obtained along with nitrile and lactam products in the POCl(3)-catalysed Beckmann rearrangement from 3ß-acet-oxy-12-hydroxyiminoolean-28-olic acid methyl ester. The mechanism of the transformation leading to the title compound remains unclear and requires further investigation. Rings A, B and E are in chair conformations, ring C has a twisted-boat conformation, ring D a conformation halfway between boat and twisted-boat and rings D and E are cis-fused. In the crystal, mol-ecules are connected by weak inter-molecular C-H⋯O hydrogen bonds into layers extending parallel to the bc plane.

Oleanolic acid ethanol monosolvate.

CRYSTALS OF THE TITLE COMPOUND (SYSTEMATIC NAME: 3ß-hy-droxy-olean-12-en-28-oic acid ethanol monosolvate), C(30)H(48)O(3)·C(2)H(5)OH, were obtained from unsuccessful co-crystallization trials. The asymmetric unit contains two symmetry-independent oleanolic acid mol-ecules, as well as two ethanol solvent mol-ecules. Inter-molecular O-H⋯O hydrogen bonds stabilize the crystal packing. In the oleanolic acid mol-ecules, ring C has a slightly distorted envelope conformation, while rings A, B, D and E adopt chair conformations and rings D and E are cis-fused. Both independent ethanol mol-ecules are orientationally disordered [occupancy ratios of 0.742 (8):0.258 (8) and 0.632 (12):0.368 (12).

(4S)-(-)-4-Benzyl-2,2-dimethyl-3-o-toluoyl-1,3-oxazolidine.

The absolute configuration of the title compound, C(20)H(23)NO(2), has been confirmed as 4S. The benzyl residue and H atom at the asymmetric C-atom centre occupy pseudo-axial and bis-ectional positions, respectively. The oxazolidine ring adopts an envelope conformation. In the crystal structure, the mol-ecular packing is stabilized by non-classical C-H⋯O hydrogen bonds.

(E)-17ß,19-Epoxy-methano-17,23,24-tridemethyl-4-nor-5ß,18α-olean-3-one oxime.

In the penta-cyclic triterpenoide skeleton of the title mol-ecule, C(27)H(43)NO(2) [systematic name: (3E,3aS,5aR,5bR,7aR,11R,11aR,11bR,13aR,13bR)-5a,5b,10,10,13b-penta-methyl-icosa-hydro-1H-11,7a-(epoxy-methano)cyclo-penta-[a]chrysen-3-one oxime], the five-membered ring A has an envelope conformation, while the six-membered rings B-E adopt chair conformations. Rings A and B are cis-fused. The hydroximino group has an E configuration. Strong inter-molecular O-H⋯O hydrogen bonds link the mol-ecules into helical chains.