Di‐2‐pyridyl ketone 4‐methyl‐4‐phenyl­thio­semicarbazone

The mol­ecule of the title compound, C₁₉H₁₇N₅S, adopts a Z configuration about the azomethine bond and exists as the thione tautomer. The overall structure of the mol­ecule is distributed in four different planes. An intramolecular hydrogen bond involving the pyridyl N atom and the H atom attached to the hydrazine N atom leads to the formation of a six‐membered ring.     

4‐Methyl‐2‐[N‐(3,4‐methyl­ene­dioxy­benzyl­idene)hydrazino]­thia­zole and its reduction product, 4‐methyl‐2‐[N‐(3,4‐methyl­ene­dioxybenzyl­idene)hydrazono]‐4,5‐di­hydro­thia­zole

The crystal structures of 4‐methyl‐2‐[N‐(3,4‐methyl­ene­dioxybenzyl­idene)hydrazino]­thia­zole, C₁₂H₁₁N₃O₂S, and its reduction product 4‐methyl‐2‐[N‐(3,4‐methyl­ene­dioxybenzyl­idene)hydrazono]‐4,5‐di­hydro­thia­zole, C₁₂H₁₃N₃O₂S, have been determined and compared. In the reduction product, the tautomer observed bears an H atom on the exocyclic N atom. Both compounds form hydrogen‐bonded dimers over centers of inversion.     

True symmetry or pseudosymmetry: 5‐amino‐1‐(4‐methylphenylsulfonyl)‐4‐pyrazolin‐3‐one and a comparison with its 1‐phenylsulfonyl analogue

The title compound, C₁₀H₁₁N₃O₃S, (I), crystallizes as the NH tautomer. The two rings subtend an interplanar angle of 72.54 (4)°. An intramolecular hydrogen bond is formed from the NH₂ group to a sulfonyl O atom. The molecular packing involves layers of molecules parallel to the bc plane at x≃ 0, 1 etc., with two classical linear hydrogen bonds (amino–sulfonyl and pyrazoline–carbonyl N—H...O) and a further interaction (amino–sulfonyl N—H...O) completing a three‐centre system with the intramolecular contact. The analogous phenyl derivative, (II) [Elgemeie, Hanfy, Hopf & Jones (1998). Acta Cryst. C 54 , 136–138], crystallizes with essentially the same unit cell and packing pattern, but with two independent molecules that differ significantly in the orientation of the phenyl groups. The space group is P2₁/c for (I) but P2₁ for (II), which is thus a pseudosymmetric counterpart of (I).     

2‐(6‐Bromo­pyridin‐2‐yl)‐6‐methyl‐[1,3,6,2]­diox­aza­borocane,a new stable (pyridin‐2‐yl)­boronic acid derivative

The crystal structure of the first reported non‐substituted N‐methyl­diox­aza­borocane confirms that the presence of a methyl group attached to the N atom introduces an NB bond length that is longer than that in a simple diox­aza­borocane ring. The presence of more N atoms in the vicinity of the B atom in the title compound [systematic name: 6a‐(6‐bromo­pyridin‐2‐yl)‐3a‐methyl‐2,3,4,5‐tetra­hydro‐1,6‐dioxa‐3a‐aza‐6a‐borapentalene], C₁₀H₁₄BBrN₂O₂, does not modify significantly any structural parameter in the diox­aza­borocane ring. On the other hand, a small asymmetry appears in the bond angles of the pyridine C atom next to the B atom.     

3‐(4‐Cyano­phenyl)­pentane‐2,4‐dione and its copper(II) complex

The β‐diketone 3‐(4‐cyano­phenyl)­pentane‐2,4‐dione crystallizes as the enol tautomer 4‐(2‐hydroxy‐4‐oxopent‐2‐en‐3‐yl)­benzo­nitrile, C₁₂H₁₁NO₂, (I), with an intramolecular O—H⋯O hydrogen bond [O⋯O = 2.456 (2) Å]. Reaction of (I) with copper acetate monohydrate in the presence of triethyl­amine leads to the formation of the copper(II) complexbis­[3‐(4‐cyano­phenyl)­pentane‐2,4‐dionato‐κ²O,O]copper(II), [Cu(C₁₂H₁₀NO₂)₂], (II). In the structure of (II), the Cu atom is coordinated by four β‐diketonate O atoms in a slightly distorted square‐planar geometry, with Cu—O distances in the range 1.8946 (11)–1.9092 (11) Å. The nitrile moieties in (II) make it a candidate for reaction with other metal ions to produce supramolecular structures.     

Metallierung und C‐C‐Kupplung von 2‐Pyridylmethylamin: Synthese und Strukturen von Methylzink‐2‐pyridylmethylamid,Tris(trimethylsilyl)methylzink‐2‐pyridylmethylamid und (Z)‐1‐Amino‐1,2‐bis(2‐pyridyl)ethen

Metalation and C‐C Coupling Reaction of 2‐Pyridylmethylamine: Synthesis and Structures of Methylzinc‐2‐pyridylmethylamide, Tris(trimethylsilyl)methylzinc‐2‐pyridylmethylamide and (Z)‐1‐Amino‐1,2‐bis(2‐pyridyl)ethene The metalation of 2‐pyridylmethylamine with dimethylzinc yields methylzinc‐2‐pyridylmethylamide ( 1 ), which shows a dimer‐trimer equilibrium in solution. Compound 1 crystallizes trimeric with a Zn₃N₃‐cycle in boat conformation. The endocyclic Zn‐N distances vary between 202 and 206 pm. Heating of this compound in toluene in the presence of dimethylzinc leads to the precipitation of zinc metal and to the formation of a few crystals of bis—[methylzinc‐2‐pyridylmethylamido]‐N, N′‐bis(methylzinc)‐2,3,5,6—tetrakis(2‐pyridyl)‐1,4‐diazacyclohexane ( 2 ). The protolysis of this solution with acetamide gives yellowish (Z)‐1‐amino‐1,2‐dipyridylethene ( 3 ) in a rather poor yield. The enamine tautomer is stabilized by N‐H···N hydrogen bridges. The demanding tris(trimethylsilyl)methyl group at the zinc atom allows the isolation of the dimeric tris(trimethylsilyl)methylzinc‐2‐pyridylmethylamide (4) ₂ in good yield. A C‐C coupling reaction of this compound with dimethylzinc is not possible.     

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 [Váňa 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. B 58 , 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.     

Two tautomeric forms of 2‐amino‐5,6‐dimethylpyrimidin‐4‐one

Derivatives of 4‐hydroxypyrimidine are an important class of biomolecules. These compounds can undergo keto–enol tautomerization in solution, though a search of the Cambridge Structural Database shows a strong bias toward the 3H‐keto tautomer in the solid state. Recrystallization of 2‐amino‐5,6‐dimethyl‐4‐hydroxypyrimidine, C₆H₉N₃O, from aqueous solution yielded triclinic crystals of the 1H‐keto tautomer, denoted form (I). Though not apparent in the X‐ray data, the IR spectrum suggests that small amounts of the 4‐hydroxy tautomer are also present in the crystal. Monoclinic crystals of form (II), comprised of a 1:1 ratio of both the 1H‐keto and the 3H‐keto tautomers, were obtained from aqueous solutions containing uric acid. Forms (I) and (II) exhibit one‐dimensional and three‐dimensional hydrogen‐bonding motifs, respectively.     

Zwitterionic 5‐(1‐piperidiniomethyl)‐1H‐tetrazolide

The title compound, C₇H₁₃N₅, a tetrazole analogue of betaines, exists as a zwitterion, with the H atom of the tetrazole ring being transferred to the piperidine ring N atom. The tetrazole ring symmetry is close to C_2v, which suggests strong charge delocalization in the N—C—N fragment of the ring. There are classical hydrogen bonds in the structure which are responsible for the formation of two‐membered aggregates.     

An unusual syn conformation of 5‐formyluracil stabilized by supramolecular interactions

The asymmetric unit of the amino–oxo tautomer of 5‐formyluracil (systematic name: 2,4‐dioxo‐1,2,3,4‐tetrahydropyrimidine‐5‐carbaldehyde), C₅H₄N₂O₃, comprises one planar amino–oxo tautomer, as every atom in the structure lies on a crystallographic mirror plane. At variance with all the previously reported small‐molecule crystal structures containing the 5‐formyluracil residue, the formyl substituent in the title compound exhibits an unusual syn conformation. The molecules are linked into planar sheets parallel to the bc plane by a combination of six N—H...O and C—H...O hydrogen bonds. Four of the hydrogen bonds are utilized to stabilize the formyl group in the syn conformation.     

Green chemistry synthesis: 2‐amino‐3‐[(E)‐(2‐pyridyl)methylideneamino]but‐2‐enedinitrile monohydrate and 5‐cyano‐2‐(2‐pyridyl)‐1‐(2‐pyridylmethyl)‐1H‐imidazole‐4‐carboxamide

The title compounds, C₁₀H₉N₅O·H₂O (L1·H₂O) and C₁₆H₁₂N₆O (L2), were synthesized by solvent‐free aldol condensation at room temperature. L1, prepared by grinding picolinaldehyde with 2,3‐diamino‐3‐isocyanoacrylonitrile in a 1:1 molar ratio, crystallized as a monohydrate. L2 was prepared by grinding picolinaldehyde with 2,3‐diamino‐3‐isocyanoacrylonitrile in a 2:1 molar ratio. By varying the conditions of crystallization it was possible to obtain two polymorphs, viz. L2‐I and L2‐II; both crystallized in the monoclinic space group P2₁/c. They differ in the orientation of one pyridine ring with respect to the plane of the imidazole ring. In L2‐I, this ring is oriented towards and above the imidazole ring, while in L2‐II it is rotated away from and below the imidazole ring. In all three molecules, there is a short intramolecular N—H...N contact inherent to the planarity of the systems. In L1·H₂O, this involves an amino H atom and the C=N N atom, while in L2 it involves an amino H atom and an imidazole N atom. In the crystal structure of L1·H₂O, there are N—H...O and O—H...O intermolecular hydrogen bonds which link the molecules to form two‐dimensional networks which stack along [001]. These networks are further linked via intermolecular N—H...N(cyano) hydrogen bonds to form an extended three‐dimensional network. In the crystal structure of L2‐I, symmetry‐related molecules are linked via N—H...N hydrogen bonds, leading to the formation of dimers centred about inversion centres. These dimers are further linked via N—H...O hydrogen bonds involving the amide group, also centred about inversion centres, to form a one‐dimensional arrangement propagating in [100]. In the crystal structure of L2‐II, the presence of intermolecular N—H...O hydrogen bonds involving the amide group results in the formation of dimers centred about inversion centres. These are linked via N—H...N hydrogen bonds involving the second amide H atom and the cyano N atom, to form two‐dimensional networks in the bc plane. In L2‐I and L2‐II, C—H...π and π–π interactions are also present.     

(1S)‐1‐Phenylethanaminium 4‐{[(1S,2S)‐1‐hydroxy‐2,3‐dihydro‐1H,1′H‐[2,2′‐biinden]‐2‐yl]methyl}benzoate

The title molecular salt, C₈H₁₂N⁺·C₂₆H₂₁O₃⁻, contains a dimeric indane pharmacophore that demonstrates potent anti‐inflammatory activity. The indane group of the anion exhibits some disorder about the α‐C atom, which appears common to many structures containing this group. A model to account for the slight disorder was attempted, but this was deemed unsuccessful because applying bond‐length constraints to all the bonds about the α‐C atom led to instability in the refinement. The absolute configuration was determined crystallographically as S,S,S by anomalous dispersion methods with reference to both the Flack parameter and Bayesian statistics on Bijvoet differences. The configuration was also determined by an a priori knowledge of the absolute configuration of the (1S)‐1‐phenylethanaminium counter‐ion. The molecules pack in the crystal structure to form an infinite two‐dimensional hydrogen‐bond network in the (100) plane of the unit cell.     

2‐Oxo‐2‐phenyl‐N‐[(R)‐1‐phenylethyl]acetamide and N,N‐dimethyl‐2‐(1‐naphthyl)‐2‐oxoacetamide: possibility of Yang photocyclization in a crystal

The crystal structures of 2‐oxo‐2‐phenyl‐N‐[(R)‐1‐phenylethyl]acetamide, C₁₆H₁₅NO₂, (I), and N,N‐dimethyl‐2‐(1‐naphthyl)‐2‐oxoacetamide, C₁₄H₁₃NO₂, (II), were determined in an attempt to understand the reason for the lack of Yang photocyclization in their respective crystals. In the case of (I), the long distance between the O atom of the carbonyl group and the γ‐H atom, and between the C atom of the carbonyl group and the γ‐C atom, preclude Yang photocyclization. For (II), the deviation of the γ‐H atom from the plane of the carbonyl group and interactions between the naphthalene rings are regarded as possible reasons for the chemical inertia. The two independent molecules of (I) differ in their conformation. N—H...O hydrogen bonds link molecules of (I) into chains extended along the b axis.     

Poly[[diaquabis(μ2‐1‐oxo‐2,6,7‐trioxa‐1‐phosphabicyclo[2.2.2]octane‐4‐carboxylato)copper(II)] dihydrate]

The asymmetric unit of the title complex, {[Cu(C₅H₆O₆P)₂(H₂O)₂]·2H₂O}_n, consists of half a Cu atom, one complete 1‐oxo‐2,6,7‐trioxa‐1‐phosphabicyclo[2.2.2]octane‐4‐carboxylate anion ligand and two non‐equivalent water molecules. The Cu atom lies on a crystallographic inversion centre and has an elongated axially distorted octahedral environment. A two‐dimensional layer structure parallel to (100) is formed as a result of the connectivity brought about by each anion bonding to two different Cu atoms via a carboxylate O atom and a bridging O atom of a C—O—P group. The water molecules participate in extensive O—H...O hydrogen bonding. Neighbouring layers are linked together by intermolecular hydrogen‐bonding interactions. The crystal structure is characterized by intra‐ and interlayer motifs of a hydrogen‐bonded network. This study demonstrates the usefulness of carboxylates with caged phosphate esters in crystal engineering.     

NMR and X‐ray structural studies on 3‐benzyl‐8‐bromoadenine

8‐Bromoadenine was benzylated in the presence of base to give a mixture of two regioisomers. One was easily recognized as 9‐benzyl‐8‐bromoadenine, but the other structure could not be determined with absolute certainty by NMR. Therefore, X‐ray crystallography was used to prove that the benzyl group was attached to N‐3. Furthermore, it is shown that the 3‐benzyl adenine derivative exists as the amine tautomer both in the crystalline state as well as in solution (DMSO‐d₆), with restricted rotation around the N⁶? C6 bond. J. Heterocyclic Chem., (2011).     

(1R,2S)‐2‐[N‐Methyl‐N‐(4‐toluene­sulfonyl)amino]‐1‐phenylpropan‐1‐ol

In the title compound, C₁₇H₂₁NO₃S, the S atom is in a distorted tetrahedral geometry and the N atom exhibits sp² character. The antiperiplanar conformation is observed for the N and hydroxyl‐O atoms and the torsion angle around the N—C linkage is ?136.3 (2)°. The mol­ecules are linked by O—H?O intermolecular hydrogen bonds to form an infinite one‐dimensional chains along the c axis.     

Biological properties of two enantiomorphic forms of N‐(2,6‐dimethylphenyl)‐4‐hydroxy‐2,2‐dioxo‐1H‐2λ6,1‐benzothiazine‐3‐carboxamide,a structural analogue of piroxicam

The title benzothiazine‐3‐carboxamide, C₁₇H₁₆N₂O₄S, crystallized in two enantiomorphic crystal forms with the space groups P3₂ and P3₁ despite the absence of a classic stereogenic atom. The molecular structures are mirror images of each other. Only one sulfonyl O atom takes part in intramolecular hydrogen bonding as a proton acceptor and this atom is different in the two enantiomorphic structures. As a result, the S atom becomes a pseudo‐stereogenic centre. This fact is worth taking into account due to the different biological activities of the enantiomorphic forms. One form possesses a high analgesic activity, while the other form revealed a high anti‐inflammatory activity.     

(E)‐4‐[(2‐Carbamoylhydrazinylidene)methyl]‐3‐hydroxy‐5‐hydroxymethyl‐2‐methylpyridin‐1‐ium nitrate

The title compound, C₉H₁₃N₄O₃⁺·NO₃⁻, is the first structurally characterized Schiff base derived from semicarbazide and pyridoxal. Unusually for an unsubstituted semicarbazone, the compound adopts a syn conformation, in which the carbonyl O atom is in a cis disposition relative to the azomethine N atom. This arrangement is supported by a pair of hydrogen bonds between the organic cation and the nitrate anion. The cation is essentially planar, with only a hydroxymethyl O atom deviating significantly from the mean plane of the remaining atoms (r.m.s. deviation of the remaining non‐H atoms = 0.01 Å). The molecules are linked into flat layers by N—H...O and C—H...O hydrogen bonds. O—H...O hydrogen bonds involving the hydroxymethyl group as a donor interconnect the layers into a three‐dimensional structure.     

Tris[2‐(morpholin‐4‐ylmethyl)phenyl‐κ2C1,N]antimony(III)

The title compound, [Sb(C₁₁H₁₄NO)₃], is monomeric with the Sb atom located on a threefold axis. The complex exhibits distorted trigonal–antiprismatic geometry around the Sb atom, owing to the presence of intramolecular N→Sb interactions. H...phenyl intermolecular interactions lead to the formation of dimers stacked along the c axis. The morpholine rings exhibit almost ideal chair conformations. No intermolecular interactions between the morpholine rings of neighbouring molecules were observed.     

7‐Nitro­indazole

The title compound, C₇H₅N₃O₂, is an inhibitor of nitric oxide synthase and mono­amine oxidase. The N1H tautomer crystallized as a dimer and adopts a planar conformation assisted by intramolecular hydrogen bonding.