A chain of π-stacked molecules in 4-(2-chlorophenyl)pyrrolo[1,2-a]quinoxaline and a hydrogen-bonded sheet in (4RS)-4-(1,3-1,3-benzodioxol-6-yl)-4,5-dihydropyrrolo[1,2-a]quinoxaline

Author(s):  
Juan C. Castillo ◽  
Rodrigo Abonía ◽  
Justo Cobo ◽  
Christopher Glidewell

In the molecule of 4-(2-chlorophenyl)pyrrolo[1,2-a]quinoxaline, C17H11ClN2, (I), the bond lengths are consistent with electron delocalization in the two outer rings of the fused tricyclic system, with a localized double bond in the central ring. The molecules of (I) are linked into chains by a π–π stacking interaction. In (4RS)-4-(1,3-benzodioxol-6-yl)-4,5-dihydropyrrolo[1,2-a]quinoxaline, C18H14N2O2, (II), the central ring of the fused tricyclic system adopts a conformation intermediate between screw-boat and half-chair forms. A combination of N—H...O and C—H...π(arene) hydrogen bonds links the molecules of (II) into a sheet. Comparisons are made with related compounds.

Author(s):  
Chayanna Harish Chinthal ◽  
Hemmige S. Yathirajan ◽  
Nagaraja Manju ◽  
Balakrishna Kalluraya ◽  
Sabine Foro ◽  
...  

The crystal structures of three benzimidazole esters containing aryl or heterocyclic substituents at position 2 are reported, and all three exhibit disorder of molecular entities. In ethyl 1-methyl-2-[4-(prop-2-ynoxy)phenyl]-1H-benzimidazole-5-carboxylate, C20H18N2O3, (I), the prop-2-yn-1-oxyphenyl unit is disordered over two sets of atomic sites having effectively equal occupancies, 0.506 (5) and 0.494 (5). The propyl substituent in ethyl 1-propyl-2-(pyren-1-yl)-1H-benzimidazole-5-carboxylate, C29H24N2O2, (II), is disordered over two sets of atomic sites having occupancies 0.601 (8) and 0.399 (8), and the ester unit in ethyl 1-methyl-2-(5-chloro-3-methyl-1-phenyl-1H-pyrazol-4-yl)-1H-benzimidazole-5-carboxylate, C21H19ClN4O2 (III), is disordered over two sets of atomic sites having occupancies 0.645 (7) and 0.355 (7). In each of the C—H...π(arene) hydrogen bonds in (I), the donor and acceptor form parts of different disorder components, so that no continuous aggregation is possible. The molecules of (II) are linked by a single C—H...O hydrogen bond into C(10) chains, which are linked into sheets by a π–π stacking interaction, whereas those of (III) are just linked into C(13) chains, again by a single C—H...O hydrogen bond. Comparisons are made with the structures of some related compounds.


2019 ◽  
Vol 75 (8) ◽  
pp. 1253-1260 ◽  
Author(s):  
Haruvegowda Kiran Kumar ◽  
Hemmige S. Yathirajan ◽  
Belakavadi K. Sagar ◽  
Sabine Foro ◽  
Christopher Glidewell

Six new 1-aroyl-4-(4-methoxyphenyl)piperazines have been prepared, using coupling reactions between benzoic acids and N-(4-methoxyphenyl)piperazine. There are no significant hydrogen bonds in the structure of 1-benzoyl-4-(4-methoxyphenyl)piperazine, C18H20N2O2, (I). The molecules of 1-(2-fluorobenzoyl)-4-(4-methoxyphenyl)piperazine, C18H19FN2O2, (II), are linked by two C—H...O hydrogen bonds to form chains of rings, which are linked into sheets by an aromatic π–π stacking interaction. 1-(2-Chlorobenzoyl)-4-(4-methoxyphenyl)piperazine, C18H19ClN2O2, (III), 1-(2-bromobenzoyl)-4-(4-methoxyphenyl)piperazine, C18H19BrN2O2, (IV), and 1-(2-iodobenzoyl)-4-(4-methoxyphenyl)piperazine, C18H19IN2O2, (V), are isomorphous, but in (III) the aroyl ring is disordered over two sets of atomic sites having occupancies of 0.942 (2) and 0.058 (2). In each of (III)–(V), a combination of two C—H...π(arene) hydrogen bonds links the molecules into sheets. A single O—H...O hydrogen bond links the molecules of 1-(2-hydroxybenzoyl)-4-(4-methoxyphenyl)piperazine, C18H20N2O3, (VI), into simple chains. Comparisons are made with the structures of some related compounds.


Author(s):  
Jairo Quiroga ◽  
Dayana Pantoja ◽  
Justo Cobo ◽  
Christopher Glidewell

In the title compound, C31H29N3O2, the reduced pyridine ring adopts a conformation intermediate between the envelope and half-chair forms. The aryl rings of the benzyl and phenyl substituents are nearly parallel and overlap, indicative of an intramolecular π–π stacking interaction. A combination of two C—H...O hydrogen bonds and one C—H...N hydrogen bond links the molecules into a bilayer havingtert-butyl groups on both faces.<!?tpb=19.5pt>


Author(s):  
Jorge Trilleras ◽  
Kelly Velásquez ◽  
Justo Cobo ◽  
Christopher Glidewell

The title compound, C16H9FN2S, crystallizes as a nonmerohedral twin with twin rotation about the reciprocal-lattice vector [10\overline{1}]*. The molecules are nearly planar and the dihedral angle between the planes of the two aryl rings is only 4.4 (2)°. The molecules are linked by pairs of C—H...N hydrogen bonds to form cyclic centrosymmetricR22(18) dimers, which are linked into chains by an aromatic π–π stacking interaction. Comparisons are made with some related 3-aryl-2-thienylacrylonitriles.


2000 ◽  
Vol 56 (1) ◽  
pp. 58-67 ◽  
Author(s):  
John N. Low ◽  
Emily J. Storey ◽  
Mary McCarron ◽  
James L. Wardell ◽  
George Ferguson ◽  
...  

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.


2006 ◽  
Vol 62 (4) ◽  
pp. 666-675 ◽  
Author(s):  
Christopher Glidewell ◽  
John N. Low ◽  
Janet M. S. Skakle ◽  
James L. Wardell

The structures of five of the possible six isomers of (E,E)-1,4-bis(nitrophenyl)-2,3-diaza-1,3-butadiene are reported, including two polymorphs of one of the isomers. (E,E)-1,4-Bis(2-nitrophenyl)-2,3-diaza-1,3-butadiene, C14H10N4O4 (I), crystallizes in two polymorphic forms (Ia) and (Ib) in which the molecules lie across centres of inversion in space groups P21/n and P21/c, respectively: the molecules in (Ia) and (Ib) are linked into chains by aromatic π...π stacking interactions and C—H...π(arene) hydrogen bonds, respectively. Molecules of (E,E)-1-(2-nitrophenyl)-4-(3-nitrophenyl)-2,3-diaza-1,3-butadiene (II) are linked into sheets by two independent C—H...O hydrogen bonds. The molecules of (E,E)-1,4-bis(3-nitrophenyl)-2,3-diaza-1,3-butadiene (III) lie across inversion centres in the space group P21/n, and a combination of a C—H...O hydrogen bond and a π...π stacking interaction links the molecules into sheets. A total of four independent C—H...O hydrogen bonds link the molecules of (E,E)-1-(3-nitrophenyl)-4-(4-nitrophenyl)-2,3-diaza-1,3-butadiene (IV) into sheets. In (E,E)-1,4-bis(4-nitrophenyl)-2,3-diaza-1,3-butadiene (V) the molecules, which lie across centres of inversion in the space group P21/n, are linked by just two independent C—H...O hydrogen bonds into a three-dimensional framework.


2007 ◽  
Vol 63 (1) ◽  
pp. 101-110 ◽  
Author(s):  
Solange M. S. V. Wardell ◽  
Marcus V. N. de Souza ◽  
James L. Wardell ◽  
John N. Low ◽  
Christopher Glidewell

1-(2-Chloronicotinoyl)-2-(2-nitrophenyl)hydrazine, C12H9ClN4O3, crystallizes in three polymorphic forms, two monoclinic forms in space groups Cc (Ia) and P21 (Ib), and an orthorhombic form in space group Pbcn (Ic). In the Cc polymorph (Ia) the molecules are linked into sheets by combinations of one N—H...O and two C—H...O hydrogen bonds, while in the P21 polymorph (Ib) the molecules are linked into sheets by combinations of three hydrogen bonds, one each of N—H...O, C—H...N and C—H...O types. In the orthorhombic polymorph (Ic) the molecules are linked into a complex three-dimensional framework structure by a combination of one N—H...O, one N—H...N and three C—H...O hydrogen bonds, and an aromatic π...π stacking interaction. In the isomeric compound 1-(2-chloronicotinoyl)-2-(3-nitrophenyl)hydrazine (II) the molecules are again linked into a three-dimensional framework, this time by a combination of three hydrogen bonds, one each of N—H...O, N—H...N and C—H...O types, weakly augmented by a π...π stacking interaction. The molecules of 1-(2-chloronicotinoyl)-2-(4-nitrophenyl)hydrazine (III) are linked into sheets by a combination of three hydrogen bonds, one each of N—H...O, N—H...N and C—H...O types.


Author(s):  
Chayanna Harish Chinthal ◽  
Hemmige S. Yathirajan ◽  
Nagaraja Manju ◽  
Balakrishna Kalluraya ◽  
Sabine Foro ◽  
...  

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.


2016 ◽  
Vol 72 (7) ◽  
pp. 549-554 ◽  
Author(s):  
Lina M. Acosta Quintero ◽  
Alirio Palma ◽  
Justo Cobo ◽  
Christopher Glidewell

Compounds containing the tricyclic dibenzo[b,e]azepine system have potential activity in the treatment of a number of diseases. Continuing with our studies on the synthesis of new small and potentially bioactive molecules, a synthetic route, involving acid-catalysed intramolecular Friedel–Crafts cyclization, to the readily separable diastereoisomers of 11-ethyl-6,11-dihydro-5H-dibenzo[b,e]azepine-6-carboxamide, a potentially useful precursor in the synthesis of analogues of some anti-allergenic, antidepressant and antihistaminic drugs currently in use, has been developed starting from 2-allylphenylamine and methyl 2-bromo-2-phenylacetate and proceedingviaracemic methyl 2-[(2-allylphenyl)amino]-2-phenylacetate (A) and racemic 2-[(2-allylphenyl)amino]-2-phenylacetamide (B), to give the two diastereoisomers (I) and (II), C17H18N2O. Isomers (I) and (II), and their precursors (A) and (B), have all been fully characterized spectroscopically. Structure analysis of the minor isomer (I) shows that it has the (6RS,11RS) configuration, and that the azepine ring adopts a conformation intermediate between the boat and twist-boat forms, with the carboxamide and ethyl substituents both occupying quasi-equatorial sites. The molecules of (I) are linked by a combination of N—H...O, N—H...π(arene) and C—H...π(arene) hydrogen bonds to form complex sheets. Comparisons are made with the structures of some related compounds.


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