Four N7‐benzyl‐substituted 4,5,6,7‐tetrahydro‐1H‐pyrazolo[3,4‐b]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐diones as ethanol hemisolvates: similar molecular constitutions but different crystal structures

3‐tert‐Butyl‐7‐(4‐chlorobenzyl)‐4′,4′‐dimethyl‐1‐phenyl‐4,5,6,7‐tetrahydro‐1H‐pyrazolo[3,4‐b]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐dione ethanol hemisolvate, C₃₀H₃₄ClN₃O₂·0.5C₂H₆O, (I), its 7‐(4‐bromobenzyl)‐ analogue, C₃₀H₃₄BrN₃O₂·0.5C₂H₆O, (II), and its 7‐(4‐methylbenzyl)‐ analogue, C₃₁H₃₇N₃O₂·0.5C₂H₆O, (III), are isomorphous, with the ethanol component disordered across a twofold rotation axis in the space group C2/c. In the corresponding 7‐[4‐(trifluoromethyl)benzyl]‐ compound, C₃₁H₃₄F₃N₃O₂·0.5C₂H₆O, (IV), the ethanol component is disordered across a centre of inversion in the space group P. In each of (I)–(IV), the reduced pyridine ring adopts a half‐chair conformation. The heterocyclic components in (I)–(III) are linked into centrosymmetric dimers by a single C—H...π interaction, with the half‐occupancy ethanol component linked to the dimer by a combination of C—H...O and O—H...π(arene) hydrogen bonds. The heterocyclic molecules in (IV) are linked into chains of centrosymmetric rings by C—H...O and C—H...π hydrogen bonds, again with the half‐occupancy ethanol component pendent from the chain. The significance of this study lies in the isomorphism of the related derivatives (I)–(III), in the stoichiometric hemisolvation by ethanol, where the disordered solvent molecule is linked to the heterocyclic component by a two‐point linkage, and in the differences between the crystal structures of (I)–(III) and that of (IV).     

Substituent position effect on the crystal structures of N‐phenyl‐2‐phthalimidoethanesulfonamide derivatives

In order to determine the impact of different substituents and their positions on intermolecular interactions and ultimately on the crystal packing, unsubstituted N‐phenyl‐2‐phthalimidoethanesulfonamide, C₁₆H₁₄N₂O₄S, (I), and the N‐(4‐nitrophenyl)‐, C₁₆H₁₃N₃O₆S, (II), N‐(4‐methoxyphenyl)‐, C₁₆H₁₆N₃O₆S, (III), and N‐(2‐ethylphenyl)‐, as the monohydrate, C₁₈H₁₈N₂O₄S·H₂O, (IV), derivatives have been characterized by single‐crystal X‐ray crystallography. Sulfonamides (I) and (II) have triclinic crystal systems, while (III) and (IV) are monoclinic. Although the molecules differ from each other only with respect to small substituents and their positions, they crystallized in different space groups as a result of differing intra‐ and intermolecular hydrogen‐bond interactions. The structures of (I), (II) and (III) are stabilized by intermolecular N—H…O and C—H…O hydrogen bonds, while that of (IV) is stabilized by intermolecular O—H…O and C—H…O hydrogen bonds. All four structures are of interest with respect to their biological activities and have been studied as part of a program to develop anticonvulsant drugs for the treatment of epilepsy.     

Three sterically hindered 6‐amino‐5‐cyano‐2‐methyl‐4‐(1‐naphthyl)‐4H‐pyran‐3‐carboxylate derivatives

In the title compounds, 2‐methoxyethyl 6‐amino‐5‐cyano‐2‐methyl‐4‐(1‐naphthyl)‐4H‐pyran‐3‐carboxylate, C₂₁H₂₀N₂O₄, (II), isopropyl 6‐amino‐5‐cyano‐2‐methyl‐4‐(1‐naphthyl)‐4H‐pyran‐3‐carboxylate, C₂₁H₂₀N₂O₃, (III), and ethyl 6‐amino‐5‐cyano‐2‐methyl‐4‐(1‐naphthyl)‐4H‐pyran‐3‐carboxylate, C₂₀H₁₈N₂O₃, (IV), the heterocyclic pyran ring adopts a flattened boat conformation. In (II) and (III), the carbonyl group and a double bond of the heterocyclic ring are mutually anti, but in (IV) they are mutually syn. The ester O atoms in (II) and (III) and the carbonyl O atom in (IV) participate in intramolecular C—H...O contacts to form six‐membered rings. The dihedral angles between the naphthalene substituent and the closest four atoms of the heterocyclic ring are 73.3 (1), 71.0 (1) and 74.3 (1)° for (II)–(IV), respectively. In all three structures, only one H atom of the NH₂ group takes part in N—H...O [in (II) and (III)] or N—H...N [in (IV)] intermolecular hydrogen bonds, and chains [in (II) and (III)] or dimers [in (IV)] are formed. In (II), weak intermolecular C—H...O and C—H...N hydrogen bonds, and in (III) intermolecular C—H...O hydrogen bonds link the chains into ladders along the a axis.     

Six closely related 4,6‐disubstituted 2‐amino‐5‐formylpyrimidines: different ring conformations,polarized electronic structures,and hydrogen‐bonded assembly in zero,one, two and three dimensions

In each of ethyl N‐{2‐amino‐5‐formyl‐6‐[methyl(phenyl)amino]pyrimidin‐4‐yl}glycinate, C₁₆H₁₉N₅O₃, (I), N‐{2‐amino‐5‐formyl‐6‐[methyl(phenyl)amino]pyrimidin‐4‐yl}glycinamide, C₁₄H₁₆N₆O₂, (II), and ethyl 3‐amino‐N‐{2‐amino‐5‐formyl‐6‐[methyl(phenyl)amino]pyrimidin‐4‐yl}propionate, C₁₇H₂₁N₅O₃, (III), the pyrimidine ring is effectively planar, but in each of methyl N‐{2‐amino‐6‐[benzyl(methyl)amino]‐5‐formylpyrimidin‐4‐yl}glycinate, C₁₆H₁₉N₅O₃, (IV), ethyl 3‐amino‐N‐{2‐amino‐6‐[benzyl(methyl)amino]‐5‐formylpyrimidin‐4‐yl}propionate, C₁₈H₂₃N₅O₃, (V), and ethyl 3‐amino‐N‐[2‐amino‐5‐formyl‐6‐(piperidin‐4‐yl)pyrimidin‐4‐yl]propionate, C₁₅H₂₃N₅O₃, (VI), the pyrimidine ring is folded into a boat conformation. The bond lengths in each of (I)–(VI) provide evidence for significant polarization of the electronic structure. The molecules of (I) are linked by paired N—H...N hydrogen bonds to form isolated dimeric aggregates, and those of (III) are linked by a combination of N—H...N and N—H...O hydrogen bonds into a chain of edge‐fused rings. In the structure of (IV), molecules are linked into sheets by means of two hydrogen bonds, both of N—H...O type, in the structure of (V) by three hydrogen bonds, two of N—H...N type and one of C—H...O type, and in the structure of (VI) by four hydrogen bonds, all of N—H...O type. Molecules of (II) are linked into a three‐dimensional framework structure by a combination of three N—H...O hydrogen bonds and one C—H...O hydrogen bond.     

Four related esters: two 4‐(aroylhydrazinyl)‐3‐nitrobenzoates and two 3‐aryl‐1,2,4‐benzotriazine‐6‐carboxylates

The molecules of both methyl 4‐[2‐(4‐chlorobenzoyl)hydrazinyl]‐3‐nitrobenzoate, C₁₅H₁₂ClN₃O₅, (I), and methyl 4‐[2‐(2‐fluorobenzoyl)hydrazinyl]‐3‐nitrobenzoate, C₁₅H₁₂FN₃O₅, (II), contain an intramolecular N—H...O hydrogen bond, and both show electronic polarization in the nitrated aryl ring. In both compounds, molecules are linked by a combination of N—H...O and C—H...O hydrogen bonds to form sheets, which are built from R₄³(18) rings in (I) and from R₄⁴(28) rings in (II). In each of methyl 3‐phenyl‐1,2,4‐benzotriazine‐6‐carboxylate, C₁₅H₁₁N₃O₂, (III), and methyl 3‐(4‐methylphenyl)‐1,2,4‐benzotriazine‐6‐carboxylate, C₁₆H₁₃N₃O₂, (IV), the benzotriazine unit shows naphthalene‐type delocalization. There are no hydrogen bonds in the structures of compounds (III) and (IV), but in both compounds, the molecules are linked into chains by π–π stacking interactions involving the benzotriazine units. The mechanism of chain formation is the same in both (III) and (IV), and the different orientations of the two chains can be related to the approximate relationship between the unit‐cell metrics for (III) and (IV).     

Conversion of 3‐amino‐4‐arylamino‐1H‐isochromen‐1‐ones to 1‐arylisochromeno[3,4‐d][1,2,3]triazol‐5(1H)‐ones: synthesis,spectroscopic characterization and the structures of four products and one ring‐opened derivative

An efficient synthesis of 1‐arylisochromeno[3,4‐d][1,2,3]triazol‐5(1H)‐ones, involving the diazotization of 3‐amino‐4‐arylamino‐1H‐isochromen‐1‐ones in weakly acidic solution, has been developed and the spectroscopic characterization and crystal structures of four examples are reported. The molecules of 1‐phenylisochromeno[3,4‐d][1,2,3]triazol‐5(1H)‐one, C₁₅H₉N₃O₂, (I), are linked into sheets by a combination of C—H…N and C—H…O hydrogen bonds, while the structures of 1‐(2‐methylphenyl)isochromeno[3,4‐d][1,2,3]triazol‐5(1H)‐one, C₁₆H₁₁N₃O₂, (II), and 1‐(3‐chlorophenyl)isochromeno[3,4‐d][1,2,3]triazol‐5(1H)‐one, C₁₅H₈ClN₃O₂, (III), each contain just one hydrogen bond which links the molecules into simple chains, which are further linked into sheets by π‐stacking interactions in (II) but not in (III). In the structure of 1‐(4‐chlorophenyl)isochromeno[3,4‐d][1,2,3]triazol‐5(1H)‐one, (IV), isomeric with (III), a combination of C—H…O and C—H…π(arene) hydrogen bonds links the molecules into sheets. When compound (II) was exposed to a strong acid in methanol, quantitative conversion occurred to give the ring‐opened transesterification product methyl 2‐[4‐hydroxy‐1‐(2‐methylphenyl)‐1H‐1,2,3‐triazol‐5‐yl]benzoate, C₁₇H₁₅N₃O₃, (V), where the molecules are linked by paired O—H…O hydrogen bonds to form centrosymmetric dimers.     

Four N7‐alkoxybenzyl‐substituted 4,5,6,7‐tetrahydro‐1H‐pyrazolo[3,4‐b]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐diones: hydrogen‐bonded supramolecular structures in zero,one, two or three dimensions

3‐tert‐Butyl‐7‐(4‐methoxybenzyl)‐4′,4′‐dimethyl‐1‐phenyl‐4,5,6,7‐tetrahydro‐1H‐pyrazolo[3,4‐b]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐dione, C₃₁H₃₇N₃O₃, (I), 3‐tert‐butyl‐7‐(2,3‐dimethoxybenzyl)‐4′,4′‐dimethyl‐1‐phenyl‐4,5,6,7‐tetrahydro‐1H‐pyrazolo[3,4‐b]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐dione, C₃₂H₃₉N₃O₄, (II), 3‐tert‐butyl‐4′,4′‐dimethyl‐7‐(3,4‐methylenedioxybenzyl)‐1‐phenyl‐4,5,6,7‐tetrahydro‐1H‐pyrazolo[3,4‐b]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐dione, C₃₁H₃₅N₃O₄, (III), and 3‐tert‐butyl‐4′,4′‐dimethyl‐1‐phenyl‐7‐(3,4,5‐trimethoxybenzyl)‐4,5,6,7‐tetrahydro‐1H‐pyrazolo[3,4‐b]pyridine‐5‐spiro‐1′‐cyclohexane‐2′,6′‐dione ethanol 0.67‐solvate, C₃₃H₄₁N₃O₅·0.67C₂H₆O, (IV), all contain reduced pyridine rings having half‐chair conformations. The molecules of (I) and (II) are linked into centrosymmetric dimers and simple chains, respectively, by C—H...O hydrogen bonds, augmented only in (I) by a C—H...π hydrogen bond. The molecules of (III) are linked by a combination of C—H...O and C—H...π hydrogen bonds into a chain of edge‐fused centrosymmetric rings, further linked by weak hydrogen bonds into supramolecular arrays in two or three dimensions. The heterocyclic molecules in (IV) are linked by two independent C—H...O hydrogen bonds into sheets, from which the partial‐occupancy ethanol molecules are pendent. The significance of this study lies in its finding of a very wide range of supramolecular aggregation modes dependent on rather modest changes in the peripheral substituents remote from the main hydrogen‐bond acceptor sites.     

Four 7‐aryl‐substituted pyrido[2,3‐d]pyrimidine‐2,4(1H,3H)‐diones: similar molecular structures but different crystal structures

Molecules of 1,3‐dimethyl‐7‐(4‐methylphenyl)pyrido[2,3‐d]pyrimidine‐2,4(1H,3H)‐dione, C₁₆H₁₅N₃O₂, (I), are linked by paired C—H...O hydrogen bonds to form centrosymmetric R₂²(10) dimers, which are linked into chains by a single π–π stacking interaction. A single C—H...O hydrogen bond links the molecules of 7‐(biphenyl‐4‐yl)‐1,3‐dimethylpyrido[2,3‐d]pyrimidine‐2,4(1H,3H)‐dione, C₂₁H₁₇N₃O₂, (II), into C(10) chains, which are weakly linked into sheets by a π–π stacking interaction. In 7‐(4‐fluorophenyl)‐3‐methylpyrido[2,3‐d]pyrimidine‐2,4(1H,3H)‐dione, C₁₄H₁₀FN₃O₂, (III), an N—H...O hydrogen bond links the molecules into C(6) chains, which are linked into sheets by a π–π stacking interaction. The molecules of 7‐(4‐methoxyphenyl)‐3‐methylpyrido[2,3‐d]pyrimidine‐2,4(1H,3H)‐dione, C₁₅H₁₃N₃O₃, (IV), are also linked into C(6) chains by an N—H...O hydrogen bond, but here the chains are linked into sheets by a combination of two independent C—H...π(arene) hydrogen bonds.     

Seven 5‐benzylamino‐3‐tert‐butyl‐1‐phenyl‐1H‐pyrazoles: unexpected isomorphisms,and hydrogen‐bonded supramolecular structures in zero,one and two dimensions

5‐Benzylamino‐3‐tert‐butyl‐1‐phenyl‐1H‐pyrazole, C₂₀H₂₃N₃, (I), and its 5‐[4‐(trifluoromethyl)benzyl]‐, C₂₁H₂₂F₃N₃, (III), and 5‐(4‐bromobenzyl)‐, C₂₀H₂₂BrN₃, (V), analogues, are isomorphous in the space group C2/c, but not strictly isostructural; molecules of (I) form hydrogen‐bonded chains, while those of (III) and (V) form hydrogen‐bonded sheets, albeit with slightly different architectures. Molecules of 3‐tert‐butyl‐5‐(4‐methylbenzylamino)‐1‐phenyl‐1H‐pyrazole, C₂₁H₂₅N₃, (II), are linked into hydrogen‐bonded dimers by a combination of N—H...π(arene) and C—H...π(arene) hydrogen bonds, while those of 3‐tert‐butyl‐5‐(4‐chlorobenzylamino)‐1‐phenyl‐1H‐pyrazole, C₂₀H₂₂ClN₃, (IV), form hydrogen‐bonded chains of rings which are themselves linked into sheets by an aromatic π–π stacking interaction. Simple hydrogen‐bonded chains built from a single N—H...O hydrogen bond are formed in 3‐tert‐butyl‐5‐(4‐nitrobenzylamino)‐1‐phenyl‐1H‐pyrazole, C₂₀H₂₂N₄O₂, (VI), while in 3‐tert‐butyl‐5‐(3,4,5‐trimethoxybenzylamino)‐1‐phenyl‐1H‐pyrazole, C₂₃H₂₉N₃O₃, (VII), which crystallizes with Z′ = 2 in the space group P, pairs of molecules are linked into two independent centrosymmetric dimers, one generated by a three‐centre N—H...(O)₂ hydrogen bond and the other by a two‐centre N—H...O hydrogen bond.     

Hydrogen‐bonded sheet structures in neutral,anionic and hydrated 6‐amino‐2‐(morpholin‐4‐yl)‐5‐nitrosopyrimidines

In each of 6‐amino‐3‐methyl‐2‐(morpholin‐4‐yl)‐5‐nitrosopyrimidin‐4(3H)‐one, C₉H₁₃N₅O₃, (I), morpholin‐4‐ium 4‐amino‐2‐(morpholin‐4‐yl)‐5‐nitroso‐6‐oxo‐1,6‐dihydropyrimidin‐1‐ide, C₄H₁₀NO⁺·C₈H₁₀N₅O₃⁻, (II), and 6‐amino‐2‐(morpholin‐4‐yl)‐5‐nitrosopyrimidin‐4(3H)‐one hemihydrate, C₈H₁₁N₅O₃·0.5H₂O, (III), the bond distances within the pyrimidine components are consistent with significant electronic polarization, which is most marked in (II) and least marked in (I). Despite the high level of substitution, the pyrimidine rings are all effectively planar, and in each of the pyrimidine components, there are intramolecular N—H...O hydrogen bonds. In each compound, the organic components are linked by multiple N—H...O hydrogen bonds to form sheets of widely differing construction, and in compound (III) adjacent sheets are linked by the water molecules, so forming a three‐dimensional hydrogen‐bonded framework. This study also contains the first direct geometric comparison between the electronic polarization in a neutral aminonitrosopyrimidine and that in its ring‐deprotonated conjugate anion in a metal‐free environment.     

Supramolecular aggregation in three 4‐aryl‐6‐(1H‐indol‐3‐yl)‐3‐methyl‐1‐phenyl‐1H‐pyrazolo[3,4‐b]pyridine‐5‐carbonitriles

Both 6‐(1H‐indol‐3‐yl)‐3‐methyl‐4‐(4‐methylphenyl)‐1‐phenyl‐1H‐pyrazolo[3,4‐b]pyridine‐5‐carbonitrile and 6‐(1H‐indol‐3‐yl)‐3‐methyl‐4‐(4‐methoxyphenyl)‐1‐phenyl‐1H‐pyrazolo[3,4‐b]pyridine‐5‐carbonitrile crystallize from dimethylformamide solutions as stoichiometric 1:1 solvates, viz. C₂₉H₂₁N₅·C₃H₇NO, (I), and C₂₉H₂₁N₅O·C₃H₇NO, (II), respectively; however, 6‐(1H‐indol‐3‐yl)‐3‐methyl‐1‐phenyl‐4‐(3,4,5‐trimethoxyphenyl)‐1H‐pyrazolo[3,4‐b]pyridine‐5‐carbonitrile, C₃₁H₂₅N₅O₃, (III), crystallizes in the unsolvated form. The heterocyclic components of (I) are linked by C—H...π(arene) hydrogen bonds to form cyclic centrosymmetric dimers, from which the solvent molecules are pendent, linked by N—H...O hydrogen bonds. In (II), the heterocyclic components are linked by a combination of C—H...N and C—H...π(arene) hydrogen bonds into chains containing two types of centrosymmetric ring, and the pendent solvent molecules are linked to these chains by N—H...O hydrogen bonds. Molecules of (III) are linked into simple C(12) chains by an N—H...O hydrogen bond, and these chains are weakly linked into pairs by an aromatic π–π stacking interaction.     

Synthesis and structures of six closely related N‐[3‐(2‐chlorobenzoyl)‐5‐ethylthiophen‐2‐yl]arylamides,together with an isolated reaction intermediate: order versus disorder,molecular conformations and hydrogen bonding in zero,one and two dimensions

Six closely related N‐[3‐(2‐chlorobenzoyl)‐5‐ethylthiophen‐2‐yl]arylamides have been synthesized and structurally characterized, together with a representative reaction intermediate. In each of N‐[3‐(2‐chlorobenzoyl)‐5‐ethylthiophen‐2‐yl]benzamide, C₂₀H₁₆ClNO₂S, (I), N‐[3‐(2‐chlorobenzoyl)‐5‐ethylthiophen‐2‐yl]‐4‐phenylbenzamide, C₂₆H₂₀ClNO₂S, (II), and 2‐bromo‐N‐[3‐(2‐chlorobenzoyl)‐5‐ethylthiophen‐2‐yl]benzamide, C₂₀H₁₅BrClNO₂S, (III), the molecules are disordered over two sets of atomic sites, with occupancies of 0.894 (8) and 0.106 (8) in (I), 0.832 (5) and 0.168 (5) in (II), and 0.7006 (12) and 0.2994 (12) in (III). In each of N‐[3‐(2‐chlorobenzoyl)‐5‐ethylthiophen‐2‐yl]‐2‐iodobenzamide, C₂₀H₁₅ClINO₂S, (IV), and N‐[3‐(2‐chlorobenzoyl)‐5‐ethylthiophen‐2‐yl]‐2‐methoxybenzamide, C₂₁H₁₈ClNO₃S, (V), the molecules are fully ordered, but in N‐[3‐(2‐chlorobenzoyl)‐5‐ethylthiophen‐2‐yl]‐2,6‐difluorobenzamide, C₂₀H₁₄ClF₂NO₂S, (VI), which crystallizes with Z′ = 2 in the space group C2/c, one of the two independent molecules is fully ordered, while the other is disordered over two sets of atomic sites having occupancies of 0.916 (3) and 0.084 (3). All of the molecules in compounds (I)–(VI) exhibit an intramolecular N—H…O hydrogen bond. The molecules of (I) and (VI) are linked by C—H…O hydrogen bonds to form finite zero‐dimensional dimers, which are cyclic in (I) and acyclic in (VI), those of (III) are linked by C—H…π(arene) hydrogen bonds to form simple chains, and those of (IV) and (V) are linked into different types of chains of rings, built in each case from a combination of C—H…O and C—H…π(arene) hydrogen bonds. Two C—H…O hydrogen bonds link the molecules of (II) into sheets containing three types of ring. In benzotriazol‐1‐yl 3,4‐dimethoxybenzoate, C₁₅H₁₃N₃O₄, (VII), the benzoate component is planar and makes a dihedral angle of 84.51 (6)° with the benzotriazole unit. Comparisons are made with related compounds.     

4‐(2‐Hydroxyphenyl)‐2‐phenyl‐2,3‐dihydro‐1H‐1,5‐benzodiazepine and the 2‐(2,3‐dimethoxyphenyl)‐, 2‐(3,4‐dimethoxyphenyl)‐ and 2‐(2,5‐dimethoxyphenyl)‐substituted derivatives

The 1,5‐benzodiazepine ring system exhibits a puckered boat‐like conformation for all four title compounds [4‐(2‐hydroxyphenyl)‐2‐phenyl‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₁H₁₈N₂O, (I), 2‐(2,3‐dimethoxyphenyl)‐4‐(2‐hydroxyphenyl)‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₃H₂₂N₂O₃, (II), 2‐(3,4‐dimethoxyphenyl)‐4‐(2‐hydroxyphenyl)‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₃H₂₂N₂O₃, (III), and 2‐(2,5‐dimethoxyphenyl)‐4‐(2‐hydroxyphenyl)‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₃H₂₂N₂O₃, (IV)]. The stereochemical correlation of the two C₆ aromatic groups with respect to the benzodiazepine ring system is pseudo‐equatorial–equatorial for compounds (I) (the phenyl group), (II) (the 2,3‐dimethoxyphenyl group) and (III) (the 3,4‐dimethoxyphenyl group), while for (IV) (the 2,5‐dimethoxyphenyl group) the system is pseudo‐axial–equatorial. An intramolecular hydrogen bond between the hydroxyl OH group and a benzodiazepine N atom is present for all four compounds and defines a six‐membered ring, whose geometry is constant across the series. Although the molecular structures are similar, the supramolecular packing is different; compounds (I) and (IV) form chains, while (II) forms dimeric units and (III) displays a layered structure. The packing seems to depend on at least two factors: (i) the nature of the atoms defining the hydrogen bond and (ii) the number of intermolecular interactions of the types O—H...O, N—H...O, N—H...π(arene) or C—H...π(arene).     

A concise synthesis of a highly substituted 6‐(1H‐benzimidazol‐1‐yl)‐5‐nitrosopyrimidin‐2‐amine: synthetic sequence and the molecular and supramolecular structures of one product and two intermediates

A concise and efficient synthesis of 6‐benzimidazolyl‐5‐nitrosopyrimidines has been developed using Schiff base‐type intermediates derived from N⁴‐(2‐aminophenyl)‐6‐methoxy‐5‐nitrosopyrimidine‐2,4‐diamine. 6‐Methoxy‐N⁴‐{2‐[(4‐methylbenzylidene)amino]phenyl}‐5‐nitrosopyrimidine‐2,4‐diamine, (I), and N⁴‐{2‐[(ethoxymethylidene)amino]phenyl}‐6‐methoxy‐5‐nitrosopyrimidine‐2,4‐diamine, (III), both crystallize from dimethyl sulfoxide solution as the 1:1 solvates C₁₉H₁₈N₆O₂·C₂H₆OS, (Ia), and C₁₄H₁₆N₆O₃·C₂H₆OS, (IIIa), respectively. The interatomic distances in these intermediates indicate significant electronic polarization within the substituted pyrimidine system. In each of (Ia) and (IIIa), intermolecular N—H…O hydrogen bonds generate centrosymmetric four‐molecule aggregates. Oxidative ring closure of intermediate (I), effected using ammonium hexanitratocerate(IV), produced 4‐methoxy‐6‐[2‐(4‐methylphenyl‐1H‐benzimidazol‐1‐yl]‐5‐nitrosopyrimidin‐2‐amine, C₁₉H₁₆N₆O₂, (II) [Cobo et al. (2018). Private communication (CCDC 1830889). CCDC, Cambridge, England], where the extent of electronic polarization is much less than in (Ia) and (IIIa). A combination of N—H…N and C—H…O hydrogen bonds links the molecules of (II) into complex sheets.     

Reduced 3,4′‐bipyrazoles from a simple pyrazole precursor: synthetic sequence,molecular structures and supramolecular assembly

The reaction of 5‐chloro‐3‐methyl‐1‐phenyl‐1H‐pyrazole‐4‐carbaldehyde and N‐benzylmethylamine under microwave irradiation gives 5‐[benzyl(methyl)amino]‐3‐methyl‐1‐phenyl‐1H‐pyrazole‐4‐carbaldehyde, C₁₉H₁₉N₃O, (I). Subsequent reactions under basic conditions, between (I) and a range of acetophenones, yield the corresponding chalcones. These undergo cyclocondensation reactions with hydrazine to produce reduced bipyrazoles which can be N‐formylated with formic acid or N‐acetylated with acetic anhydride. The structures of (I) and of representative examples from this reaction sequence are reported, namely the chalcone (E )‐3‐{5‐[benzyl(methyl)amino]‐3‐methyl‐1‐phenyl‐1H‐pyrazol‐4‐yl}‐1‐(4‐bromophenyl)prop‐2‐en‐1‐one, C₂₇H₂₄BrN₃O, (II), the N‐formyl derivative (3RS )‐5′‐[benzyl(methyl)amino]‐3′‐methyl‐1′,5‐diphenyl‐3,4‐dihydro‐1′H ,2H‐[3,4′‐bipyrazole]‐2‐carbaldehyde, C₂₈H₂₇N₅O, (III), and the N‐acetyl derivative (3RS )‐2‐acetyl‐5′‐[benzyl(methyl)amino]‐5‐(4‐methoxyphenyl)‐3′‐methyl‐1′‐phenyl‐3,4‐dihydro‐1′H ,2H‐[3,4′‐bipyrazole], which crystallizes as the ethanol 0.945‐solvate, C₃₀H₃₁N₅O₂·0.945C₂H₆O, (IV). There is significant delocalization of charge from the benzyl(methyl)amino substituent onto the carbonyl group in (I), but not in (II). In each of (III) and (IV), the reduced pyrazole ring is modestly puckered into an envelope conformation. The molecules of (I) are linked by a combination of C—H…N and C—H…π(arene) hydrogen bonds to form a simple chain of rings; those of (III) are linked by a combination of C—H…O and C—H…N hydrogen bonds to form sheets of R ²₂(8) and R ⁶₆(42) rings, and those of (IV) are linked by a combination of O—H…N and C—H…O hydrogen bonds to form a ribbon of edge‐fused R ²₄(16) and R ⁴₄(24) rings.     

Eight new crystal structures of 5‐(hydroxymethyl)uracil, 5‐carboxyuracil and 5‐carboxy‐2‐thiouracil: insights into the hydrogen‐bonded networks and the predominant conformations of the C5‐bound residues

In order to examine the preferred hydrogen‐bonding pattern of various uracil derivatives, namely 5‐(hydroxymethyl)uracil, 5‐carboxyuracil and 5‐carboxy‐2‐thiouracil, and for a conformational study, crystallization experiments yielded eight different structures: 5‐(hydroxymethyl)uracil, C₅H₆N₂O₃, (I), 5‐carboxyuracil–N,N‐dimethylformamide (1/1), C₅H₄N₂O₄·C₃H₇NO, (II), 5‐carboxyuracil–dimethyl sulfoxide (1/1), C₅H₄N₂O₄·C₂H₆OS, (III), 5‐carboxyuracil–N,N‐dimethylacetamide (1/1), C₅H₄N₂O₄·C₄H₉NO, (IV), 5‐carboxy‐2‐thiouracil–N,N‐dimethylformamide (1/1), C₅H₄N₂O₃S·C₃H₇NO, (V), 5‐carboxy‐2‐thiouracil–dimethyl sulfoxide (1/1), C₅H₄N₂O₃S·C₂H₆OS, (VI), 5‐carboxy‐2‐thiouracil–1,4‐dioxane (2/3), 2C₅H₄N₂O₃S·3C₆H₁₂O₃, (VII), and 5‐carboxy‐2‐thiouracil, C₁₀H₈N₄O₆S₂, (VIII). While the six solvated structures, i.e. (II)–(VII), contain intramolecular S(6) O—H…O hydrogen‐bond motifs between the carboxy and carbonyl groups, the usually favoured R₂²(8) pattern between two carboxy groups is formed in the solvent‐free structure, i.e. (VIII). Further R₂²(8) hydrogen‐bond motifs involving either two N—H…O or two N—H…S hydrogen bonds were observed in three crystal structures, namely (I), (IV) and (VIII). In all eight structures, the residue at the ring 5‐position shows a coplanar arrangement with respect to the pyrimidine ring which is in agreement with a search of the Cambridge Structural Database for six‐membered cyclic compounds containing a carboxy group. The search confirmed that coplanarity between the carboxy group and the cyclic residue is strongly favoured.     

Cyclic and acyclic products from the reactions between methyl 3‐oxobutanoate and arylhydrazines

The molecules of methyl 3‐(2‐nitrophenylhydrazono)butanoate, C₁₁H₁₃N₃O₄, (I), and methyl 3‐(2,4‐dinitrophenylhydrazono)butanoate, C₁₁H₁₂N₄O₆, (II), both prepared from methyl 3‐oxobutanoate and the corresponding nitrophenylhydrazine, exhibit polarized molecular electronic structures; in each of (I) and (II), the molecules are linked into chains by a single C—H...O hydrogen bond. The molecules of 5‐hydroxy‐3‐methyl‐1‐phenyl‐1H‐pyrazole, C₁₀H₁₀N₂O, (III), prepared by the reaction of methyl 3‐oxobutanoate and phenylhydrazine, are linked into chains by a single O—H...N hydrogen bond. The reaction between methyl 3‐oxobutanoate and 3‐nitrophenylhydrazine yields 5‐hydroxy‐3‐methyl‐1‐(3‐nitrophenyl)‐1H‐pyrazole, (IV), which when crystallized from acetone yields 4‐isopropylidene‐3‐methyl‐1‐(3‐nitrophenyl)‐1H‐pyrazol‐5(4H)‐one, C₁₃H₁₃N₃O₃, (V).     

Two isomorphous crotonatolanthanide complexes: tetra‐μ‐but‐2‐enoato‐bis[diaqua(but‐2‐enoato)Ln]–2,6‐diaminopurine (1/2) (Ln = Dy and Ho)

The title isomorphous compounds, tetra‐μ‐but‐2‐enoato‐bis[diaqua(but‐2‐enoato)dysprosium(III)]–2,6‐diaminopurine (1/2), [Dy₂(C₄H₅O₂)₆(H₂O)₄]·2C₅H₆N₆, and tetra‐μ‐but‐2‐enoato‐bis[diaqua(but‐2‐enoato)holmium(III)]–2,6‐diaminopurine (1/2), [Ho₂(C₄H₅O₂)₆(H₂O)₄]·2C₅H₆N₆, consist of [Ln(crot)₃(H₂O)₂]₂ dimers (crot is crotonate or but‐2‐enoate; Ln is the lanthanide cation), built up around inversion centres and completed by 2,6‐diaminopurine molecules. The lanthanide cation is coordinated by three chelating crotonate units and two water molecules. One of the chelating carboxylate groups acts also in a bridging mode sharing one O atom with both cations and the final result is a pair of DyO₉ tricapped prismatic polyhedra linked to each other through a central (Dy—O)₂ loop. A feature of the structures is the existence of a complex intermolecular interaction scheme involving two sets of tightly interlinked non‐intersecting one‐dimensional structures, one of them formed by the [Dy(crot)₃(H₂O)₂]₂ dimers (running along [100] and linked by O—H...O hydrogen bonds) and the second formed by 2,6‐diaminopurine molecules (evolving along [010] linked by N—H...N hydrogen bonds).     

Conformational isomers of the [(5‐methyl‐2‐pyridinio)aminomethylene]diphosphonate dianion and [(5‐methyl‐2‐pyridyl)aminomethylene]diphosphonate trianion in salts with 4‐aminopyridine and ammonia

The crystal structures of two salts, products of the reactions between [(5‐methyl‐2‐pyridyl)aminomethylene]bis(phosphonic acid) and 4‐aminopyridine or ammonia, namely bis(4‐aminopyridinium) hydrogen [(5‐methyl‐2‐pyridinio)aminomethylene]diphosphonate 2.4‐hydrate, 2C₅H₇N₂⁺·C₇H₁₀N₂O₆P₂²⁻·2.4H₂O, (I), and triammonium hydrogen [(5‐methyl‐2‐pyridyl)aminomethylene]diphosphonate monohydrate, 3NH₄⁺·C₇H₉N₂O₆P₂³⁻·H₂O, (II), have been determined. In (I), the Z configuration of the ring N—C and amino N—H bonds of the bisphosphonate dianion with respect to the C_ring—N_amino bond is consistent with that of the parent zwitterion. Removing the H atom from the pyridyl N atom results in the opposite E configuration of the bisphosphonate trianion in (II). Compound (I) exhibits a three‐dimensional hydrogen‐bonded network, in which 4‐aminopyridinium cations and water molecules are joined to ribbons composed of anionic dimers linked by O—H...O and N—H...O hydrogen bonds. The supramolecular motif resulting from a combination of these three interactions is a common phenomenon in crystals of all of the Z‐isomeric zwitterions of 4‐ and 5‐substituted (2‐pyridylaminomethylene)bis(phosphonic acid)s studied to date. In (II), ammonium cations and water molecules are linked to chains of trianions, resulting in the formation of double layers.