scholarly journals Reduced 3,4′-bipyrazoles carrying thiophene and thiazole substituents: structures of two intermediates and two products

2021 ◽  
Vol 77 (4) ◽  
pp. 335-340
Author(s):  
Chayanna Harish Chinthal ◽  
Hemmige S. Yathirajan ◽  
Nagaraja Manju ◽  
Balakrishna Kalluraya ◽  
Sabine Foro ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Intermolecular Interactions ◽  
Cycloaddition Reactions ◽  
Independent Components ◽  
Analogous Compound ◽  
A Chain ◽  
Related Compounds ◽  
Centrosymmetric Dimers

Cycloaddition reactions between 3-(5-aryloxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)-1-(thiophen-2-yl)prop-2-en-1-ones and thiosemicarbazide leads to the formation of reduced 3,4′-bipyrazole-2-carbothioamides. Further cycloaddition of these intermediates with either diethyl acetylenedicarboxylate or 4-bromophenacyl bromide leads to reduced 3,4′-bipyrazoles carrying oxothiazole or thiazole substituents, respectively. The structures of two representative intermediates and two representative products established unambiguously the regiochemistry of the cycloaddition reactions. The molecules of 3′-methyl-5′-(2-methylphenoxy)-1′-phenyl-5-(thiophen-2-yl)-3,4-dihydro-1′H,2H-3,4′-bipyrazole-2-carbothioamide, C25H23N5OS2 (Ia), are linked by N—H...N hydrogen bonds to form simple C(8) chains. The analogous compound 5′-(2,4-dichlorophenoxy)-3′-methyl-1′-phenyl-5-(thiophen-2-yl)-3,4-dihydro-1′H,2H-3,4′-bipyrazole-2-carbothioamide hemihydrate crystallizes as a hemihydrate, C24H19Cl2N5OS2·0.5H2O (Ib), and the independent components are linked into a chain of spiro-fused R 4 4(20) rings by a combination of O—H...N and N—H...O hydrogen bonds. In the structure of ethyl (Z)-2-{2-[3′-methyl-1′-phenyl-5-(thiophen-2-yl)-5′-(2-methylphenoxy)-3,4-dihydro-1′H,2H-3,4′-bipyrazole-2-yl]-4-oxo-4,5-dihydrothiazol-5-ylidene}acetate, C31H27N5O4S2 (II), inversion-related pairs of molecules are linked by paired C—H...π(arene) hydrogen bonds to form cyclic centrosymmetric dimers, but there are no direction-specific intermolecular interactions in 4-(4-bromophenyl)-2-[5′-(2,4-dichlorophenoxy)-3′-methyl-1′-phenyl-5-(thiophen-2-yl)-3,4-dihydro-1′H,2H-3,4′-bipyrazole-2-yl]-4-thiazole, C32H22BrCl2N5OS2 (III). Comparisons are made with the structures of some related compounds.

scholarly journals A chalcone showing positional disorder, two related diarylcyclohexenones showing enantiomeric disorder and a related hydroxyterphenyl, all derived from simple carbonyl precursors

2015 ◽  
Vol 71 (7) ◽  
pp. 610-617 ◽  
Author(s):  
Vinutha V. Salian ◽  
Badiadka Narayana ◽  
Hemmige S. Yathirajan ◽  
Mehmet Akkurt ◽  
Ömer Çelik ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Intermolecular Interactions ◽  
Carbonyl Compounds ◽  
Reference Site ◽  
Reaction Pathway ◽  
The Other ◽  
Positional Disorder ◽  
Independent Molecules ◽  
Related Compounds ◽  
Centrosymmetric Dimers

Four compounds are reported, all of which lie along a versatile reaction pathway which leads from simple carbonyl compounds to terphenyls. (2E)-1-(2,4-Dichlorophenyl)-3- [4-(prop-1-en-2-yl)phenyl]prop-2-en-1-one, C18H14Cl2O, (I), prepared from 4-(prop-1-en-2-yl)benzaldehyde and 2,4-dichloroacetophenone, exhibits disorder over two sets of atomic sites having occupancies of 0.664 (6) and 0.336 (6). The related chalcone (2E)-3-(4-chlorophenyl)-1-(4-fluorophenyl)prop-2-en-1-one reacts with acetone to produce (5RS)-3-(4-chlorophenyl)-5-[4-(propan-2-yl)phenyl]cyclohex-2-en-1-one, C21H21ClO, (II), which exhibits enantiomeric disorder with occupancies at the reference site of 0.662 (4) and 0.338 (4) for the (5R) and (5S) forms; the same chalcone reacts with methyl 3-oxobutanoate to give methyl (1RS,6SR)-4-(4-chlorophenyl)-6-[4-(propan-2-yl)phenyl]-2-oxocyclohex-3-ene-1-carboxylate, C23H23ClO3, (III), where the reference site contains both (1R,6S) and (1S,6R) forms with occupancies of 0.923 (3) and 0.077 (3), respectively. Oxidation, using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, of ethyl (1RS,6SR)-6-(4-bromophenyl)-4-(4-fluorophenyl)-2-oxocyclohex-3-ene-1-carboxylate, prepared in a similar manner to (II) and (III), produces ethyl 4′′-bromo-4-fluoro-5′-hydroxy-1,1′:3′,1′′-terphenyl-4′-carboxylate, C21H16BrFO3, (IV), which crystallizes withZ′ = 2 in the space groupP\overline{1}. There are no significant intermolecular interactions in the structures of compounds (I) and (II), but for the major disorder component of compound (III), the molecules are linked into sheets by a combination of C—H...O and C—H...π(arene) hydrogen bonds. The two independent molecules of compound (IV) form two different centrosymmetric dimers, one built from inversion-related pairs of C—H...O hydrogen bonds and the other from inversion-related pairs of C—H...π(arene) hydrogen bonds. Comparisons are made with related compounds.

Conformational preferences in 2-nitrophenylthiolates: interplay between intra- and intermolecular forces; structures of (E)-1-(4-methyl-2-nitrobenzenethiolato)-2-phenylethene, S-(2-nitrophenyl)benzenecarbothiolate and 1-(2-nitrophenylthio)-2,5-pyrrolidinedione

2000 ◽  
Vol 56 (1) ◽  
pp. 58-67 ◽  
Author(s):  
John N. Low ◽  
Emily J. Storey ◽  
Mary McCarron ◽  
James L. Wardell ◽  
George Ferguson ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Nitro Group ◽  
Intermolecular Forces ◽  
Aryl Ring ◽  
Local Energy Minimum ◽  
Conformational Preferences ◽  
A Chain ◽  
Related Compounds ◽  
Scf Calculations ◽  
Intramolecular Forces

In (E)-1-(4-methyl-2-nitrobenzenethiolato)-2-phenylethene, C15H13NO2S (1) (orthorhombic Pbca), the nitro group is almost coplanar with the adjacent aryl ring, but the dihedral angles between the nitro-aryl and styryl fragments is ∼121°. The molecules are linked by paired C—H...O hydrogen bonds in a chain of rings. In S-(2-nitrophenyl)benzenecarbothiolate, C13H9NO3S (2) (monoclinic P21/a), the nitro group is rotated by 33.0 (2)° out of the plane of the adjacent aryl ring and the thiobenzoate group is strongly twisted away from the plane of the disubstituted aryl ring. The molecules of (2) are linked into chains by C—H...O hydrogen bonds, and each chain is linked to two neighbouring chains by means of aromatic π...π stacking interactions. In 1-(2-nitrophenylthio)-2,5-pyrrolidinedione, C10H8N2O4S (3) (monoclinic P21/a), the nitro group is again almost coplanar with the adjacent aryl ring, but the pyrrolidinedione unit is almost orthogonal to the O2NC6H4SN plane. There are three types of C—H...O hydrogen bond in the structure, and these link the molecules into a two-dimensional net. The conformations of these molecules have been investigated by SCF calculations and two energy minima have been identified for each: the molecules of (1) and (3) adopt conformations in their crystals which are close to those at the overall energy minima calculated for isolated molecules, while molecules of (2) adopt a conformation in the crystal close to that calculated for the local energy minimum. Comparisons are made with the structures of some related compounds and it is concluded that, while the nature of the two conformational minima is determined by intramolecular forces, the choice between them is determined primarily by intermolecular forces.

Crystal structures and Hirshfeld surface analysis of four 1,4-bis(methoxyphenyl)-2,3-diazabuta-1,3-dienes: comparisons of the intermolecular interactions in related compounds

2019 ◽  
Vol 234 (1) ◽  
pp. 59-71 ◽  
Author(s):  
Ligia R. Gomes ◽  
John N. Low ◽  
Nathasha R. de L. Correira ◽  
Thais C.M. Noguiera ◽  
Alessandra C. Pinheiro ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Intermolecular Interactions ◽  
Three Dimensional ◽  
Hirshfeld Surface ◽  
Dimensional Structure ◽  
Intermolecular Hydrogen Bonds ◽  
Π Interactions ◽  
Isomeric Compound ◽  
Related Compounds

Abstract The crystal structures of four azines, namely 1-3-bis(4-methoxyphenyl)-2,3-diaza-1,4-butadiene, 1, 1,3-bis(2,3-dimethoxyphenyl)-2,3-diaza-1,4-butadiene, 2, 1,3-bis(2-hydroxy-3-methoxyphenyl)-2,3-diaza-1,4-butadiene, 3, and 1,3-bis(2-hydroxy-4-methoxyphenyl)-2,3-diaza-1,4-butadiene, 4, are reported. Molecules of 3 and 4, and both independent molecules of 2, Mol A and Mol B, possess inversion centers. The central C=N–N=C units in each molecule is planar with an (E,E) conformation. The intermolecular interactions found in the four compounds are C–H···O, C–H–N, C–H---π and π---π interactions. However, there is no consistent set of intermolecular interactions for the four compounds. Compound, 1, has a two-dimensional undulating sheet structure, generated from C–H···O and C–H···N intermolecular hydrogen bonds. The only recognized intermolecular interaction in 2 is a C–H···O hydrogen bond, which results in a zig-zag chain of alternating molecules, Mol A and Mol B. While 3 forms a puckered sheet of molecules, solely via C–H···π interactions, its isomeric compound, 4, has a more elaborate three-dimensional structure generated from a combination of C–H···O hydrogen bonds, C–H···π and π···π interactions. The findings in this study, based on both PLATON and Hirshfeld approaches, for the four representative compounds match well the reported structural findings in the literature of related compounds, which are based solely on geometric parameters.

scholarly journals Crystal structure ofO-ethylN-(ethoxycarbonyl)thiocarbamate

2015 ◽  
Vol 71 (10) ◽  
pp. o782-o783 ◽  
Author(s):  
Matthew J. Henley ◽  
Alex M. Schrader ◽  
Victor G. Young ◽  
George Barany
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Least Squares ◽  
Title Compound ◽  
Compound C ◽  
The One ◽  
Related Compounds ◽  
Centrosymmetric Dimers

The title compound, C6H11NO3S, provides entries to novel carbamoyl disulfanes and related compounds of interest to our laboratory. The atoms of the central O(C=S)N(C=O)O fragment have an r.m.s. deviation of 0.1077 Å from the respective least-squares plane. While several conformational orientations are conceivable, the crystal structure shows only the one in which the carbonyl and the thiocarbonyl moieties areantito each other across the central conjugated C—N—C moiety. Pairs of 2.54 Å N—H...S=C hydrogen bonds between adjacent molecules form centrosymmetric dimers in the crystal.

scholarly journals (E)-N′-Hydroxy-1,3-diphenyl-4,5-dihydro-1H-pyrazole-5-carboximidamide

2012 ◽  
Vol 68 (6) ◽  
pp. o1661-o1662 ◽  
Author(s):  
Chandra ◽  
N. Srikantamurthy ◽  
K. B. Umesha ◽  
S. Jeyaseelan ◽  
M. Mahendra
Keyword(s):  
Hydrogen Bonds ◽  
Dihedral Angle ◽  
Title Compound ◽  
Pyrazole Ring ◽  
Dihedral Angles ◽  
Compound C ◽  
Benzene Rings ◽  
Phenyl Rings ◽  
A Chain ◽  
Centrosymmetric Dimers

In the molecule of the title compound, C16H16N4O, the pyrazole ring makes dihedral angles of 8.52 (13) and 9.26 (12)° with the phenyl rings. The dihedral angle between the benzene rings is 1.86 (13)°. In the crystal, molecules are linked into centrosymmetric dimers via pairs of O—H...N hydrogen bonds. Weak N—H...N interactions connect the dimers into a chain along the [100] direction. The pyrazole ring adopts a highly flattened envelope conformation.

Interplay of hydrogen bonds, iodo...nitro interactions and aromatic π...π stacking interactions in iodo-nitroanilines

2002 ◽  
Vol 58 (4) ◽  
pp. 701-709 ◽  
Author(s):  
Simon J. Garden ◽  
Silvia P. Fontes ◽  
James L. Wardell ◽  
Janet M. S. Skakle ◽  
John N. Low ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Nitro Group ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Single Type ◽  
Stacking Interactions ◽  
Π Stacking ◽  
Independent Molecules ◽  
Related Compounds ◽  
Centrosymmetric Dimers

Molecules of 2-iodo-5-nitroaniline (I) are linked by N—H...O hydrogen bonds into centrosymmetric dimers and by asymmetric three-centre iodo...nitro interactions into chains, so forming chains of fused centrosymmetric rings: these chains are linked by aromatic π...π stacking interactions to form a three-dimensional structure. In the isomeric 4-iodo-2-nitroaniline (II), each of the two independent molecules forms hydrogen-bonded chains that are linked by two-centre iodo...nitro interactions into sheets of two types, each containing only a single type of molecule: π...π stacking interactions are absent. In 2,4-diiodo-3-nitroaniline (III), where the nitro group is almost orthogonal to the aryl ring, a combination of N—H...O hydrogen bonds and two distinct two-centre iodo...nitro interactions links the molecules into a three-dimensional framework that is reinforced by aromatic π...π stacking interactions. Bond lengths and conformations are discussed and comparisons are drawn with related compounds.

scholarly journals Different patterns of supramolecular assembly in constitutionally similar 6-arylimidazo[2,1-b][1,3,4]thiadiazoles

2014 ◽  
Vol 70 (9) ◽  
pp. 920-926 ◽  
Author(s):  
Aletti S. Praveen ◽  
Hemmige S. Yathirajan ◽  
Manpreet Kaur ◽  
Badiadka Narayana ◽  
Eric C. Hosten ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Three Dimensional ◽  
Reaction Times ◽  
Supramolecular Assembly ◽  
Dihedral Angles ◽  
Stacking Interactions ◽  
Aryl Group ◽  
Π Stacking ◽  
Related Compounds ◽  
Centrosymmetric Dimers

Four imidazo[2,1-b][1,3,4]thiadiazoles containing a simply-substituted 6-aryl group have been synthesized by reaction of 2-amino-1,3,4-thiadiazoles with bromoacetylarenes using microwave irradiation and brief reaction times. 6-(2-Chlorophenyl)imidazo[2,1-b][1,3,4]thiadiazole, C10H6ClN3S, (I), 6-(2-chlorophenyl)-2-methylimidazo[2,1-b][1,3,4]thiadiazole, C11H8ClN3S, (II), 6-(3,4-dichlorophenyl)imidazo[2,1-b][1,3,4]thiadiazole, C10H5Cl2N3S, (III), and 6-(4-fluoro-3-methoxyphenyl)-2-methylimidazo[2,1-b][1,3,4]thiadiazole, C12H10FN3OS, (IV), crystallize withZ′ values of 2, 1, 1 and 2 respectively. The molecular skeletons are all nearly planar and the dihedral angles between the imidazole and aryl rings are 1.51 (8) and 7.28 (8)° in (I), 9.65 (7)° in (II), 10.44 (8)° in (III), and 1.05 (8) and 7.21 (8)° in (IV). The molecules in (I) are linked by three independent C—H...N hydrogen bonds to form ribbons containing alternatingR22(8) andR44(18) rings, and these ribbons are linked into a three-dimensional array by three independent π-stacking interactions. Both (II) and (III) contain centrosymmetric dimers formed by π-stacking interactions but hydrogen bonds are absent, and the molecules of (IV) are linked into centrosymmetricR22(8) dimers by C—H...N hydrogen bonds. Comparisons are made with a number of related compounds.

scholarly journals Four 1-aryl-1H-pyrazole-3,4-dicarboxylate derivatives: synthesis, molecular conformation and hydrogen bonding

2018 ◽  
Vol 74 (12) ◽  
pp. 1783-1789
Author(s):  
Asma ◽  
Balakrishna Kalluraya ◽  
Hemmige S. Yathirajan ◽  
Ravindranath S. Rathore ◽  
Christopher Glidewell
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Dicarboxylic Acid ◽  
Molecular Conformation ◽  
Three Dimensional ◽  
Framework Structure ◽  
Related Compounds ◽  
Centrosymmetric Dimers

Four 1-aryl-1H-pyrazole-3,4-dicarboxylate derivatives, one acid, two esters and a dicarbohydrazide have been synthesized starting from 3-aryl sydnones, and structurally characterized. There is an intramolecular O—H...O hydrogen bond in 1-phenyl-1H-pyrazole-3,4-dicarboxylic acid, C11H8N2O4, (I), and the molecules are linked into a three-dimensional framework structure by a combination of O—H...O, O—H...N, C—H...O and C—H...π(arene) hydrogen bonds. In each of the two esters dimethyl 1-phenyl-1H-pyrazole-3,4-dicarboxylate, C13H12N2O4, (II), and dimethyl 1-(4-methylphenyl)-1H-pyrazole-3,4-dicarboxylate, C14H14N2O4, (III), C—H...O hydrogen bonds lead to the formation of cyclic centrosymmetric dimers: in (III), one of the methoxycarbonyl groups is disordered over two sets of atomic sites having occupancies 0.71 (2) and 0.29 (2). An intramolecular N—H...O hydrogen bond is present in the structure of 1-(4-methoxyphenyl)-1H-pyrazole-3,4-dicarbohydrazide, C12H14N6O3, (IV), and the molecules are linked into a three-dimensional framework structure by a combination of N—H...O, N—H...N, N—H...π(arene) and C—H...O hydrogen bonds. Comparisons are made with the structures of a number of related compounds.

Conversion of substituted 5-aryloxypyrazolecarbaldehydes into reduced 3,4′-bipyrazoles: synthesis and characterization, and the structures of four precursors and two products, and their supramolecular assembly in zero, one and two dimensions

2019 ◽  
Vol 75 (6) ◽  
pp. 768-776 ◽  
Author(s):  
Haruvegowda Kiran Kumar ◽  
Hemmige S. Yathirajan ◽  
Nagaraj Manju ◽  
Balakrishna Kalluraya ◽  
Ravindranath S. Rathore ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Supramolecular Assembly ◽  
Two Dimensions ◽  
Subsequent Reaction ◽  
Orientational Disorder ◽  
New Compounds ◽  
Cyclocondensation Reactions ◽  
Related Compounds ◽  
Centrosymmetric Dimers ◽  
C Nmr

The reaction of 5-chloro-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde with phenols under basic conditions yields the corresponding 5-aryloxy derivatives; the subsequent reaction of these carbaldehydes with substituted acetophenones yields the corresponding chalcones, which in turn undergo cyclocondensation reactions with hydrazine in the presence of acetic acid to form N-acetylated reduced bipyrazoles. Structures are reported for three 5-aryloxycarbaldehydes and the 5-piperidino analogue, and for two reduced bipyrazole products. 5-(2-Chlorophenoxy)-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde, C17H13ClN2O2, (II), which crystallizes with Z′ = 2 in the space group P\overline{1}, exhibits orientational disorder of the carbaldehyde group in each of the two independent molecules. Each of 3-methyl-5-(4-nitrophenoxy)-1-phenyl-1H-pyrazole-4-carbaldehyde, C17H13N3O4, (IV), 3-methyl-5-(naphthalen-2-yloxy)-1-phenyl-1H-pyrazole-4-carbaldehyde, C21H16N2O2, (V), and 3-methyl-1-phenyl-5-(piperidin-1-yl)-1H-pyrazole-4-carbaldehyde, C16H19N3O, (VI), (3RS)-2-acetyl-5-(4-azidophenyl)-5′-(2-chlorophenoxy)-3′-methyl-1′-phenyl-3,4-dihydro-1′H,2H-[3,4′-bipyrazole] C27H22ClN7O2, (IX) and (3RS)-2-acetyl-5-(4-azidophenyl)-3′-methyl-5′-(naphthalen-2-yloxy)-1′-phenyl-3,4-dihydro-1′H,2H-[3,4′-bipyrazole] C31H25N7O2, (X), has Z′ = 1, and each is fully ordered. The new compounds have all been fully characterized by analysis, namely IR spectroscopy, 1H and 13C NMR spectroscopy, and mass spectrometry. In each of (II), (V) and (IX), the molecules are linked into ribbons, generated respectively by combinations of C—H...N, C—H...π and C—Cl...π interactions in (II), C—H...O and C—H...π hydrogen bonds in (V), and C—H...N and C—H...O hydrogen bonds in (IX). The molecules of compounds (IV) and (IX) are both linked into sheets, by multiple C—H...O and C—H...π hydrogen bonds in (IV), and by two C—H...π hydrogen bonds in (IX). A single C—H...N hydrogen bond links the molecules of (X) into centrosymmetric dimers. Comparisons are made with the structures of some related compounds.

scholarly journals Three closely related 4,5,6,7-tetrahydro-1H-pyrazolo[4,3-c]pyridines: synthesis, molecular conformations and hydrogen bonding in zero, one and two dimensions

2017 ◽  
Vol 73 (3) ◽  
pp. 298-304
Author(s):  
Belakavadi K. Sagar ◽  
Kachigere B. Harsha ◽  
Hemmige S. Yathirajan ◽  
Kanchugarakoppal S. Rangappa ◽  
Ravindranath S. Rathore ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Pyridine Ring ◽  
Chair Conformation ◽  
Two Dimensions ◽  
Relative Orientation ◽  
Molecular Conformations ◽  
Space Groups ◽  
Related Compounds ◽  
Trifluoromethyl Groups ◽  
Centrosymmetric Dimers

In each of 1-(4-fluorophenyl)-5-methylsulfonyl-3-[4-(trifluoromethyl)phenyl]-4,5,6,7-tetrahydro-1H-pyrazolo[4,3-c]pyridine, C21H19F4N3O2S, (I), 1-(4-chlorophenyl)-5-methylsulfonyl-3-[4-(trifluoromethyl)phenyl]-4,5,6,7-tetrahydro-1H-pyrazolo[4,3-c]pyridine, C21H19ClF3N3O2S, (II), and 1-(3-methylphenyl)-5-methylsulfonyl-3-[4-(trifluoromethyl)phenyl]-4,5,6,7-tetrahydro-1H-pyrazolo[4,3-c]pyridine, C22H22F3N3O2S, (III), the reduced pyridine ring adopts a half-chair conformation with the methylsulfonyl substituent occupying an equatorial site. Although compounds (I) and (II) are not isostructural, having the space groups Pbca and P212121, respectively, their molecular conformations are very similar, but the conformation of compound (III) differs from those of (I) and (II) in the relative orientation of the N-benzyl and methylsulfonyl substituents. In compounds (II) and (III), but not in (I), the trifluoromethyl groups are disordered over two sets of atomic sites. Molecules of (I) are linked into centrosymmetric dimers by C—H...π(arene) hydrogen bonds, molecules of (II) are linked by two C—H...O hydrogen bonds to form ribbons of R 3 3(18) rings, which are themselves further linked by a C—Cl...π(arene) interaction, and a combination of C—H...O and C—H...π(arene) hydrogen bonds links the molecules of (III) into sheets. Comparisons are made with the structures of some related compounds.

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