N‐Benzyl‐2′‐iodo­cinnamanilide and N‐benzyl‐2′‐iodo‐4′‐methyl‐2‐phenyl­cinnamanilide

The aromatic ring of the cinnamic moiety in N‐benzyl‐2′‐iodo­cinnamanilide, C₂₂H₁₈INO, (I), and N‐benzyl‐2′‐iodo‐4′‐methyl‐2‐phenyl­cinnamanilide, C₂₉H₂₄INO, (II), makes a dihedral angle with the iodo­phenyl ring of 72.1 (2) and 81.0 (2)° in (I) and (II), respectively. In (I), mol­ecules exist as discrete components, while in (II), they form infinite chains along the b axis, through I?O non‐bonded interactions.     

Theoretical study of the structures,conformations, and spectroscopic properties of 2‐formylthiophene‐N‐acetylhydrazone and 2‐thiophenecarboxaldehyde‐2‐thienylhydrazone

2‐Formylthiophene‐N‐acetylhydrazone (Hait) and 2‐thiophenecarboxaldehyde‐2‐thienylhydrazone (Htit) in the cis and trans conformations were investigated in the gas‐phase by density functional method using B3LYP as the functional set and 6‐311++G(d,p) as the basis set. The cis and trans structures were fully optimized in the C₁ and C_s symmetries. Transition states were also modeled for the cis–trans isomerization of the title compounds and the barriers to internal rotation were calculated. This work reports the structural, energetics, and spectroscopic parameters of all the optimized geometries. Some of the structural parameters are in good agreement with experimental literature data. The computed parameters for these compounds are also in good agreement with a related molecule, namely, acetohydrazide. For both Hait and Htit, the trans conformers are more stable than the cis conformers and the energy barriers are larger compared with the energy differences between the cis and trans conformers. This accounts for Hait and Htit existing mostly in the trans conformation. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:144–150, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20526     

N‐substituted bis(tetrazol‐5‐yl)diazenes: Synthesis,spectra, X‐ray molecular and crystal structures,and quantum‐chemical DFT calculations

N‐Substituted bis(tetrazol‐5‐yl)diazenes (substituents are 1‐CH₃ ( 3a ), 1‐Ph ( 3b ), 2‐CH₃ ( 3c ), and 2‐^tBu ( 3d )) were synthesized by oxidative coupling of corresponding 5‐aminotetrazoles. All compounds were characterized with ¹H and ¹³C NMR, IR‐ and UV‐spectroscopy, and thermal analysis. Crystal and molecular structures of bis(1‐phenyltetra‐ zol‐5‐yl)diazene ( 3b ) and bis(2‐tert‐butyltetrazol‐5‐yl)diazene ( 3d ) were determined by single crystal X‐ray diffraction. Molecules of these compounds are trans‐isomers in solid. According to X‐Ray data, 3b molecule is S‐trans‐S‐trans conformer, however 3d is S‐cis‐S‐cis one. Quantum‐chemical investigation of geometry and relative stability of cis‐ and trans‐isomers and stable conformations of compounds 3a–d was carried out. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:24–35, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20574     

New isomeric N‐substituted hydrazones of 2‐, 3‐ and 4‐pyridinecarboxaldehydes and methyl‐3‐pyridylketone

Twelve compounds unknown in the literature N‐(E)‐2‐stilbenyloxymethylenecarbonyl substituted hydrazones of 2‐, 3‐ and 4‐pyridinecarboxaldehydes, as well as methyl‐3‐pyridylketone have been prepared. The stereochemical behavior of these compounds in dimethyl‐d₆ sulfoxide solution has been studied by ¹H NMR technique. The E geometrical isomers and cis/trans amide conformers have been found for N‐substituted hydrazones 1–12. EI induced mass spectral fragmentation of these compounds were also investigated. The data obtained create the basis for distinguishing isomers.     

2‐Iodo‐N‐(3‐nitrobenzyl)aniline and 3‐iodo‐N‐(3‐nitrobenzyl)aniline exhibit entirely different patterns of supramolecular aggregation

In 2‐iodo‐N‐(3‐nitro­benzyl)­aniline, C₁₃H₁₁IN₂O₂, the mol­ecules are linked into a three‐dimensional structure by a combination of C—H?O hydrogen bonds, iodo–nitro interactions and aromatic π–π‐stacking interactions, but N—H?O and C—H?π(arene) hydrogen bonds are absent. In the isomeric 3‐iodo‐N‐(3‐nitro­benzyl)­aniline, a two‐dimensional array is generated by a combination of N—H?O, C—H?O and C—H?π(arene) hydrogen bonds, but iodo–nitro interactions and aromatic π–π‐stacking interactions are both absent.     

Reaction of N‐(phenyl and methyl)‐C‐arylnitrones with DMAD in ionic liquid: Efficient synthesis of Δ4‐isoxazolines

Facile synthesis of N‐(methyl and phenyl)‐Δ⁴‐isoxazolines via the reaction of (Z)‐N‐(methyl and phenyl)‐C‐arylnitrones with dimethyl acethylenedicarboxylate, DMAD, in ionic liquid is described. (Z)‐N‐methyl‐C‐arylnitrones afforded the high yield of N‐methyl‐Δ⁴‐isoxazolines 4a , 4b , 4c , 4d , 4e in ionic liquid, [bmim]BF₄, at room temperature. However, the reaction of (Z)‐N‐phenyl‐C‐arylnitrones with DMAD afforded the mixtures of cis and trans isomers of related N‐phenyl‐Δ⁴‐isoxazolines ( 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j , 6a , 6b , 6c , 6d , 6e , 6f , 6g , 6h , 6i , 6j ) under these conditions. J. Heterocyclic Chem., (2012).     

N‐Benzyl­tetra­hydro­pyrido‐anellated thio­phene derivatives: new anti­cholinesterases

The title compounds, tert‐butyl 6‐benzyl‐2‐(3,3‐diethyl­ureido)‐4,5,6,7‐tetra­hydro­thieno[2,3‐c]pyridine‐3‐carboxyl­ate, C₂₄H₃₃N₃O₃S, (I), 7‐benzyl‐2‐diethyl­amino‐5,6,7,8‐tetra­hydro‐3‐oxa‐9‐thia‐1,7‐diaza­fluoren‐4‐one, C₂₀H₂₃N₃O₂S, (II), and N‐(7‐benzyl‐4‐oxo‐5,6,7,8‐tetra­hydro‐4H‐3,9‐dithia‐1,7‐diaza­fluoren‐2‐yl)benzamide, C₂₃H₁₉N₃O₂S₂, (III), form monoclinic crystal systems. In (I) and (II), the mol­ecules are linked into a three‐dimensional framework by weak inter­molecular C—H⋯O=C hydrogen bonds, whereas in (III) stronger inter­molecular N—H⋯O=C inter­actions are observed. The conformation of (I) is further stabilized by an intra­molecular N—H⋯O=C hydrogen bond, which effects the planarity of the ureido­thio­phene­carboxyl­ate moiety.     

N‐Benzylnicotinamide and N‐benzyl‐1,4‐dihydronicotinamide: useful models for NAD+ and NADH

3‐Aminocarbonyl‐1‐benzylpyridinium bromide (N‐benzylnicotinamide, BNA), C₁₃H₁₃N₂O⁺·Br⁻, (I), and 1‐benzyl‐1,4‐dihydropyridine‐3‐carboxamide (N‐benzyl‐1,4‐dihydronicotinamide, rBNA), C₁₃H₁₄N₂O, (II), are valuable model compounds used to study the enzymatic cofactors NAD(P)⁺ and NAD(P)H. BNA was crystallized successfully and its structure determined for the first time, while a low‐temperature high‐resolution structure of rBNA was obtained. Together, these structures provide the most detailed view of the reactive portions of NAD(P)⁺ and NAD(P)H. The amide group in BNA is rotated 8.4 (4)° out of the plane of the pyridine ring, while the two rings display a dihedral angle of 70.48 (17)°. In the rBNA structure, the dihydropyridine ring is essentially planar, indicating significant delocalization of the formal double bonds, and the amide group is coplanar with the ring [dihedral angle = 4.35 (9)°]. This rBNA conformation may lower the transition‐state energy of an ene reaction between a substrate double bond and the dihydropyridine ring. The transition state would involve one atom of the double bond binding to the carbon ortho to both the ring N atom and the amide substituent of the dihydropyridine ring, while the other end of the double bond accepts an H atom from the methylene group para to the N atom.     

Structure and Photochemical Properties of r‐1, c‐2, t‐3, t‐4‐l, 3‐Bis [2‐ (5‐R‐benzoxazolyl) ] −2,4‐di (4‐R' ‐phenyl) cyclobutane

r‐1, c‐2, t‐3, t‐4‐1,3‐Bis[2‐(5‐R‐benzoxazolyl)]‐2,4‐di(4‐R'‐phenyl)cyclobutane (IIa: R=R' = H; IIb: R=Me, R'= H; IIc: R = Me, R' = OMe) was synthesized with high stereo‐selectivity by the photodimerization of trans‐l‐[2‐(5‐R‐benzoxazolyl)]‐2‐(4‐R'‐phenyl) ethene (Ia: R=R' = H; Ib: R = Me, R' = H; Ic: R = Me, R' = OMe) in sulfuric acid. The structures of IIa–IIc were identified by elemental analysis, IR, UV, ¹H NMR, ¹³C NMR and MS. The molecular and crystal structure of IIc has been determined by X‐ray diffraction method. The crystal of IIc (C₃₄H₃₀N₂O₄. 0.5C₂OH) is monoclinic, space group P2₁/n with cell dimensions of a = 1.5416(3), b =0.5625(1), c = 1.7875(4) nm, β = 91.56 (3)°, V= 1.550(1) nm³, Z = 2. The structure shows that the molecule of IIc is centrosymmetric, which indicates that the dimerization process is a head‐to‐tail fashion. The selectivity of the photodimerization of Ia–Ic has been enhanced by using acidic solvent and the reaction speed would be decreased when electron donating group was introduced in the 4‐position of the phenyl group. That the photodimerization is not affected by the presence of oxygen as well as its high stereo‐selectivity demonstrated that the reaction proceeded through an excited singlet state. It was also found that under irradiation of short wavelength UV, these dimers underwent photolysis completely to reproduce its trans‐monomers, and then the new formed species changed into their cis‐isomers through trans‐cis isomerization.     

N‐{4‐Bromo‐2‐[(3‐bromo‐1‐phenylsulfonyl‐1H‐indol‐2‐yl)methyl]‐5‐methoxyphenyl}acetamide

In the title compound, C₂₄H₂₀Br₂N₂O₄S, the indole ring system is planar and the S atom has a distorted tetrahedral configuration. The sulfonyl‐bound phenyl ring is orthogonal to the indole ring system and the conformation of the phenyl­sulfonyl substituent with respect to the indole moiety is influenced by intramolecular C—H⃛O hydrogen bonds involving the two sulfonyl O atoms. The mean plane through the acetyl­amido group makes a dihedral angle of 57.0 (1)° with the phenyl ring of the benzyl moiety. In the crystal, glide‐related mol­ecules are linked together by N—H⃛O hydrogen bonds and C—H⃛π interactions to form molecular chains, which extend through the crystal. Inversion‐related chains are interlinked by C—H⃛π interactions to form molecular layers parallel to the bc plane. These layers are interconnected through π–π interactions involving the five‐ and six‐membered rings of the indole moiety.     

Exo conformers of N‐(pyridin‐2‐yl)‐ and N‐(pyridin‐3‐yl)norbornene‐5,6‐dicarboximide crystals

Two isomeric pyridine‐substituted norbornenedicarboximide derivatives, namely N‐(pyridin‐2‐yl)‐exo‐norbornene‐5,6‐dicarboximide, (I), and N‐(pyridin‐3‐yl)‐exo‐norbornene‐5,6‐dicarboximide, (II), both C₁₄H₁₂N₂O₄, have been crystallized and their structures unequivocally determined by single‐crystal X‐ray diffraction. The molecules consist of norbornene moieties fused to a dicarboximide ring substituted at the N atom by either pyridin‐2‐yl or pyridin‐3‐yl in an anti configuration with respect to the double bond, thus affording exo isomers. In both compounds, the asymmetric unit consists of two independent molecules (Z′ = 2). In compound (I), the pyridine rings of the two independent molecules adopt different conformations, i.e. syn and anti, with respect to the methylene bridge. The intermolecular contacts of (I) are dominated by C—H...O interactions. In contrast, in compound (II), the pyridine rings of both molecules have an anti conformation and the two independent molecules are linked by carbonyl–carbonyl interactions, as well as by C—H...O and C—H...N contacts.     

A Conformational Study of Cyclohexane‐1,3,5‐tricarbonitrile Derivatives

Cyclohexane‐1,3,5‐tricarbonitrile reached equilibrium having 1,3‐cis‐1,5‐cis and 1,3‐cis‐1,5‐trans isomers in a ratio of 3:7. The cis, cis‐isomer preferred the conformation with three equatorial cyano groups, where as the cis, trans‐isomer displayed two cyano groups on equatorial positions and another cyano group on axial position. Condensation of cis, cis‐cyclohexane‐1,3,5‐tricarbonitrile with L‐(S)‐valinol by the catalysis of ZnCl₂ in refluxing 1,2‐dichlorobenzene afforded two isomeric cyclohexane‐1,3,5‐trioxazolines in favor of the 1,3‐cis‐1,5‐trans isomer. Metalation of cis, cis‐cyclohexane‐1,3,5‐tricarbonitrile, followed by alkylations with dimethyl sulfate, benzyl bromide or allyl bromide, gave the cor responding trialkylation products with predominance of 1,3‐cis‐1,5‐trans isomers. The cis, trans‐isomer showed two cyano groups on axial positions and another cyano group on equatorial position, where as the cis, cis‐isomer exhibited three axial cyano groups. Treatment of trimethyl cis, cis‐cyclohexane‐1,3,5‐tricarboxylate with lithium diisopropylamide and dimethyl sulfate afforded mainly the trimethyl ester of Kemp's triacid, which showed three axial carboxylate groups. Two competitive factors, i.e. the steric effect of in coming electrophiles and the dipole‐dipole inter actions of the cyano or carboxylate groups, might inter play to give different stereoselectivities in these reaction systems.     

N‐Meth­yl‐N‐(2‐nitro­phen­yl)nitramine and N‐meth­yl‐N‐(3‐nitro­phen­yl)­nitramine

The structures of the two title isomeric compounds (systematic names: N‐meth­yl‐N,2‐dinitro­aniline and N‐meth­yl‐N,3‐di­nitro­aniline, both C₇H₇N₃O₄) are slightly different because they exhibit different steric hindrances and hydrogen‐bonding environments. The aromatic rings are planar. The –N(Me)NO₂ and –NO₂ groups are not coplanar with the rings. Comparison of the geometric parameters of the ortho, meta and para isomers together with those of N‐meth­yl‐N‐phenyl­nitramine suggests that the position of the nitro group has a strong influence on the aromatic ring distortion. The crystal packing is stabilized by weak C—H⋯O hydrogen bonds to the nitramine group.     

Supramolecular structures of three isomeric 4‐(methyl­phenylamino)­pyridine‐3‐sulfonamides

The structures of the three title isomers, namely 4‐(2‐methyl­anilino)pyridine‐3‐sulfonamide, (I), 4‐(3‐methyl­anilino)pyridine‐3‐sulfonamide, (II), and 4‐(4‐methyl­anilino)pyridine‐3‐sulfonamide, (III), all C₁₂H₁₃N₃O₂S, differ in their hydrogen‐bonding arrangements. In all three mol­ecules, the conformation of the 4‐amino­pyridine‐3‐sulfon­amide moiety is conserved by an intra­molecular N—H⋯O hydrogen bond and a C—H⋯O inter­action. In the supra­mol­ecular structures of all three isomers, similar C(6) chains are formed via inter­molecular N—H⋯N hydrogen bonds. N—H⋯O hydrogen bonds lead to C(4) chains in (I), and to R₂²(8) centrosymmetric dimers in (II) and (III). In each isomer, the overall effect of all hydrogen bonds is to form layer structures.     

Two (Z)‐N‐aryl‐3‐benzylideneisoindolin‐1‐ones

Two isoindolin‐1‐one derivatives, (Z)‐3‐benzyl­idene‐N‐phenyl­isoindolin‐1‐one, C₂₁H₁₅NO, (II), and (Z)‐3‐benzyl­idene‐N‐(4‐methoxy­phenyl)­isoindolin‐1‐one, C₂₂H₁₇NO₂, (III), were synthesized by the palladium‐catalysed heteroannulation. The mol­ecules of both compounds have a Z configuration. The interplanar angles between the five‐ and six‐membered rings of the isoindolinone moiety in (II) and (III) are 1.66 (11) and 2.26 (7)°, respectively. The phenyl rings at the N‐position in (II) and (III) are twisted out of the C₄N ring plane by 62.77 (11) and 67.10 (7)°, respectively. The substitutions at the N and C‐3 positions of the isoindolinone system have little influence on the molecular dimensions of the resulting compounds.     

Five N′‐benzylidene‐N‐methylpyrazine‐2‐carbohydrazides

The compounds N′‐benzylidene‐N‐methylpyrazine‐2‐carbohydrazide, C₁₃H₁₂N₄O, (IIa), N′‐(2‐methoxybenzylidene)‐N‐methylpyrazine‐2‐carbohydrazide, C₁₄H₁₄N₄O₂, (IIb), N′‐(4‐cyanobenzylidene)‐N‐methylpyrazine‐2‐carbohydrazide dihydrate, C₁₄H₁₁N₅O·2H₂O, (IIc), N‐methyl‐N′‐(2‐nitrobenzylidene)pyrazine‐2‐carbohydrazide, C₁₃H₁₁N₅O₃, (IId), and N‐methyl‐N′‐(4‐nitrobenzylidene)pyrazine‐2‐carbohydrazide, C₁₃H₁₁N₅O₃, (IIe), have dihedral angles between the pyrazine rings and the benzene rings in the range 55–78°. These methylated pyrazine‐2‐carbohydrazides have supramolecular structures which are formed by weak C—H...O/N hydrogen bonds, with the exception of (IIc) which is hydrated. There are π–π stacking interactions in all five compounds. Three of these structures are compared with their nonmethylated counterparts, which have dihedral angles between the pyrazine rings and the benzene rings in the range 0–6°.     

Three 1,2,4‐triazole derivatives containing subtituted benzyl and benzyl­amino groups

The title compounds, 4‐benzyl­amino‐3‐(4‐methyl­benzyl)‐1H‐1,2,4‐triazol‐5(4H)‐one, C₁₇H₁₈N₄O, (I), 3‐(4‐methyl­benzyl)‐4‐(4‐methyl­benzyl­amino)‐1H‐1,2,4‐tri­azol‐5(4H)‐one, C₁₈H₂₀N₄O, (II), and 3‐(4‐chloro­benzyl)‐4‐(4‐methyl­benzyl­amino)‐1H‐1,2,4‐triazol‐5(4H)‐one, C₁₇H₁₇ClN₄O, (III), were obtained from the corresponding Schiff base in the presence of diglyme and NaBH₄. Each compound contains a 1,2,4‐triazole ring and two benzene rings, which are essentially planar. The molecules are linked by a combination of intermolecular N—H⋯O and N—H⋯N hydrogen bonds. Additionally, there is a weak π–π stacking interaction in (I), involving the benzene ring of the amino­benzyl group and the partially aromatic 1,2,4‐triazole moiety, with a centroid–centroid distance of 3.7397 (10) Å.     

Five related N′‐(2,2,2‐trichloroethanimidoyl)benzene‐1‐carboximidamides

In the solid state, 4‐methoxy‐N′‐(2,2,2‐trichloroethanimidoyl)benzene‐1‐carboximidamide, C₁₀H₁₀Cl₃N₃O, (I), N′‐(2,2,2‐trichloroethanimidoyl)benzene‐1‐carboximidamide, C₉H₈Cl₃N₃, (II), 4‐chloro‐N′‐(2,2,2‐trichloroethanimidoyl)benzene‐1‐carboximidamide, C₉H₇Cl₄N₃, (III), 4‐bromo‐N′‐(2,2,2‐trichloroethanimidoyl)benzene‐1‐carboximidamide, C₉H₇BrCl₃N₃, (IV), and 4‐trifluoromethyl‐N′‐(2,2,2‐trichloroethanimidoyl)benzene‐1‐carboximidamide, C₁₀H₇Cl₃F₃N₃, (V), display strong intramolecular N—H...N hydrogen bonding across the chelate ring and also intramolecular N—H...Cl contacts. Additional intermolecular hydrogen bonds link the molecules into chains, double chains or sheets in all cases except for compound (V). For compound (II), there are three independent molecules per asymmetric unit.     

A structural systematic study of four isomers of difluoro‐N‐(3‐pyridyl)benzamide

The four isomers 2,4‐, (I), 2,5‐, (II), 3,4‐, (III), and 3,5‐difluoro‐N‐(3‐pyridyl)benzamide, (IV), all with formula C₁₂H₈F₂N₂O, display molecular similarity, with interplanar angles between the C₆/C₅N rings ranging from 2.94 (11)° in (IV) to 4.48 (18)° in (I), although the amide group is twisted from either plane by 18.0 (2)–27.3 (3)°. Compounds (I) and (II) are isostructural but are not isomorphous. Intermolecular N—H...O=C interactions form one‐dimensional C(4) chains along [010]. The only other significant interaction is C—H...F. The pyridyl (py) N atom does not participate in hydrogen bonding; the closest H...N_py contact is 2.71 Å in (I) and 2.69 Å in (II). Packing of pairs of one‐dimensional chains in a herring‐bone fashion occurs viaπ‐stacking interactions. Compounds (III) and (IV) are essentially isomorphous (their a and b unit‐cell lengths differ by 9%, due mainly to 3,4‐F₂ and 3,5‐F₂ substitution patterns in the arene ring) and are quasi‐isostructural. In (III), benzene rotational disorder is present, with the meta F atom occupying both 3‐ and 5‐F positions with site occupancies of 0.809 (4) and 0.191 (4), respectively. The N—H...N_py intermolecular interactions dominate as C(5) chains in tandem with C—H...N_py interactions. C—H...O=C interactions form R₂²(8) rings about inversion centres, and there are π–π stacks about inversion centres, all combining to form a three‐dimensional network. By contrast, (IV) has no strong hydrogen bonds; the N—H...N_py interaction is 0.3 Å longer than in (III). The carbonyl O atom participates only in weak interactions and is surrounded in a square‐pyramidal contact geometry with two intramolecular and three intermolecular C—H...O=C interactions. Compounds (III) and (IV) are interesting examples of two isomers with similar unit‐cell parameters and gross packing but which display quite different intermolecular interactions at the primary level due to subtle packing differences at the atom/group/ring level arising from differences in the peripheral ring‐substitution patterns.