4‐Phenyl‐1H‐imidazole (a low‐temperature redetermination), 1‐benzyl‐1H‐imidazole and 1‐mesityl‐1H‐imidazole

Low‐temperature studies of the simple variously substituted imidazole types 4‐phenyl‐1H‐imidazole, C₉H₈N₂, 1‐benzyl‐1H‐imidazole, C₁₀H₁₀N₂, and 1‐mesityl‐1H‐imidazole, C₁₂H₁₄N₂, extend comparisons between parent imidazole species and their derivatives, the pronounced double‐bond localization opposite the substituted N atom common to simple neutral species being redistributed aromatically on protonation.     

Bifunktionalisierte 1 H‐Phosphiren‐ und g1‐1‐Phosphaallen‐Wolframkomplexe

Bifunctionalized 1 H‐Phosphirene and g¹‐1‐Phosphaallene Tungsten Complexes The tungsten(0) complex [{(Me₃Si)₂HCPC(Ph)=N}W(CO)₅] 1 reacts upon heating with acetylene derivatives 2 a–d in toluene to form benzonitrile and the complexes [{(Me₃Si)₂HCPC(R)=COEt} · W(CO)₅] 5 a–d ( 5 a : R = SiMe₃; 5 b : R = SiPh₃; 5 c : R = SnMe₃; 5 d : R = SnPh₃) and [{(Me₃Si)₂HCP=C=C(OEt)R} · W(CO)₅] 6 a, b ( 6 a : R = SnMe₃; 6 b : R = SnPh₃), which have been isolated by chromatography; complexes 5 c and 6 a have been characterized as mixtures. Spectroscopic and mass spectrometric data are discussed. The crystal structure of the compound 5 a was determined by X‐ray single crystal structure analysis ( 5 a : space group P2₁/n, Z = 4, a = 977.6(2) pm, b = 1814.6(4) pm, c = 1628.0(4) pm, β = 93.95(2)°).     

Synthesis of pinacol esters of 1‐alkyl‐1H‐pyrazol‐5‐yl‐ and 1‐alkyl‐1H‐pyrazol‐4‐ylboronic acids

Starting from 1H‐pyrazol, a wide number of 1‐alkyl‐1H‐pyrazol‐4‐yl and 1‐alkyl‐1H‐pyrazol‐5‐ylboronic acids and their pinacol esters were synthesized and characterized. The key step in the described methodology is the regioselective lithiation of the pyrazole ring. The synthesized pinacolates are stable under prolonged storage and can be used as convenient reagents in organic synthesis.     

Copper(II) Halide Complexes with 1‐tert‐Butyl‐1H‐1,2,4‐triazole and 1‐tert‐Butyl‐1H‐tetrazole

1‐tert‐Butyl‐1H‐1,2,4‐triazole (tbtr) was found to react with copper(II) chloride or bromide to give the complexes [Cu(tbtr)₂X₂]_n and [Cu(tbtr)₄X₂] (X = Cl, Br). 1‐tert‐Butyl‐1H‐tetrazole (tbtt) reacts with copper(II) bromide resulting in the formation of the complex [Cu₃(tbtt)₆Br₆]. The obtained crystalline complexes as well as free ligand tbtr were characterized by elemental analysis, IR spectroscopy, thermal and X‐ray analyses. For free ligand tbtr, ¹H NMR and ¹³C NMR spectra were also recorded. In all the complexes, tbtr and tbtt act as monodentate ligands coordinated by Cu^II cations via the heteroring N⁴ atoms. The triazole complexes [Cu(tbtr)₂Cl₂]_n and [Cu(tbtr)₂Br₂]_n are isotypic, being 1D coordination polymers, formed at the expense of single halide bridges between neighboring copper(II) cations. The isotypic complexes [Cu(tbtr)₄Cl₂] and [Cu(tbtr)₄Br₂] reveal mononuclear centrosymmetric structure, with octahedral coordination of Cu^II cations. The tetrazole compound [Cu₃(tbtt)₆Br₆] is a linear trinuclear complex, in which neighboring copper(II) cations are linked by single bromide bridges.     

1‐Acetyl‐3‐ferrocenyl‐5‐methyl‐1H‐pyrazole and 1‐acetyl‐5‐ferrocenyl‐3‐(2‐pyrid­yl)‐1H‐pyrazole

Mol­ecules of 1‐acetyl‐3‐ferrocenyl‐5‐methyl‐1H‐pyrazole, [Fe(C₅H₅)(C₁₁H₁₁N₂O)], form a centrosymmetric dimer generated by a combination of one C—H⋯π(pyrazole) and one C—H⋯π(cyclo­penta­dienyl) inter­action. The dimers are linked by C—H⋯π inter­actions, involving the pyrazole rings as acceptors, into layers parallel to (10). Mol­ecules of 1‐acetyl‐5‐ferrocenyl‐3‐(2‐pyrid­yl)‐1H‐pyrazole, [Fe(C₅H₅)(C₁₅H₁₂N₃O)], are linked by C—H⋯O inter­actions into a chain running in the [010] direction. Two chains of this type passing through each unit cell are connected by O⋯π(pyridyl) inter­actions into an [010] double chain.     

1‐(2‐Pyridyl)ethan‐1‐one 8‐quinolylhydrazone and 1‐(1H‐pyrrol‐2‐yl)ethan‐1‐one 8‐quinolylhydrazone

The structures of the title compounds, C₁₆H₁₄N₄, (I), and C₁₅H₁₄N₄, (II), respectively, have been determined, and their molecular packing arrangements compared. Both are essentially flat mol­ecules, with respective dihedral angles between the quinoline and heterocyclic rings of 19.0 (1) and 8.5 (2)°. The pyridyl derivative, (I), packs in a P2₁/c unit cell, while in the pyrrolyl compound, (II), the mol­ecules pack in Pca2₁ and form a crinkled ribbon arrangement through the association of pyrrole NH groups with the quinoline N atoms.     

4‐Carboxypiperidinium 1‐carboxycyclobutane‐1‐carboxylate

The title salt, C₆H₁₂NO₂⁺·C₆H₇O₄⁻ or ISO⁺·CBDC⁻, is an ionic ensemble assisted by hydrogen bonds. The amino acid moiety (ISO or piperidine‐4‐carboxylic acid) has a protonated ring N atom (ISO⁺ or 4‐carboxypiperidinium), while the semi‐protonated acid (CBDC⁻ or 1‐carboxycyclobutane‐1‐carboxylate) has the negative charge residing on one carboxylate group, leaving the other as a neutral –COOH group. The –⁺NH₂– state of protonation allows the formation of a two‐dimensional crystal packing consisting of zigzag layers stacked along a separated by van der Waals distances. The layers extend in the bc plane connected by a complex network of N—H...O and O—H...O hydrogen bonds. Wave‐like ribbons, constructed from ISO⁺ and CBDC⁻ units and described by the graph‐set symbols C₃³(10) and R₃³(14), run alternately in opposite directions along c. Intercalated between the ribbons are ISO⁺ cations linked by hydrogen bonds, forming rings described by the graph‐set symbols R₆⁶(30) and R₄²(18). A detailed analysis of the structures of the individual components and the intricate hydrogen‐bond network of the crystal structure is given.     

New 7‐phosphanorbornenes derived from 2‐methyl‐1‐phenyl‐ and 1‐cyclohexyl‐3‐ methyl‐2,5‐dihydro‐1H‐phosphole 1‐oxides

Novel 7‐phosphanorbornene derivatives, such as 4, 5, 10 , and 11 were synthesized utilizing 1‐phenyl‐2‐methyl‐2,5‐dihydro‐1H‐phosphole oxide ( 1 ) and 1‐cyclohexyl‐3‐methyl‐2,5‐dihydro‐1H‐phosphole oxide ( 7 ) as the starting materials. Products 4 and 10 were prepared by trapping the corresponding phosphole oxide intermediates ( 3 and 9 , respectively) by N‐phenylmaleimide, while 5 and 11 were obtained by the dimerization of 3 and 9 , respectively. The trapping reaction was studied in details; on one hand, bromo‐2,3‐dihydro‐1H‐phosphole oxides ( 6‐1 and 6‐2 ) were pointed out as the intermediates, on the other hand, the trapping reaction was optimized. Bri‐ dged P‐heterocycles 4, 5, 10 , and 11 were tested in the fragmentation‐related phosphorylation of methanol. Hydrogenation of phosphanorbornenes 4 and 5 led to the corresponding phosphanorbornanes ( 12 and 14 , respectively) and to a reductive type of retro cycloaddition. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:320–326, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20097     

Ritter Reaction of 1‐Aryl‐1‐Fluoro‐2‐Haloethanes

Fluorinated phenethyl bromides 1,2 , and 3 , prove to be totally inert under Ritter reaction conditions in the presence of either SnCl₄ or AgNO₃, due to the strong deactivation by the gem‐difluoro unit. Subjecting 2‐bromo‐1‐fluoro‐1‐phenylethane to SnCl₄ in MeCN at elevated temperatures led to formation of 2‐methyl‐4‐phenyl‐4,5‐dihydrooxazole.     

Synthesis of some new 1‐acyl‐5‐aryl‐3‐(5‐methyl‐1‐p‐tolyl‐1H‐1,2,3‐triazol‐4‐yl)‐4,5‐dihydro‐1H‐pyrazole

Some new compounds (E)‐3‐aryl‐1‐(5‐methyl‐1‐p‐tolyl‐1H‐1,2,3‐triazol‐4‐yl)‐prop‐2‐en‐1‐ones 5a–e were prepared by 1‐(5‐methyl‐1‐p‐tolyl‐1H‐1,2,3‐triazol‐4‐yl)‐ethanone and various aromatic aldehydes. Then one pot reaction was happened by compounds 5a–e with hydrazine hydrate in acetic acid or propionic acid, respectively, to give the title compounds 1acyl‐5‐aryl‐3‐(5‐methyl‐1‐p‐tolyl‐1H‐1,2,3‐triazol‐4‐yl)‐4,5‐dihydro‐1H‐pyrazoles 6a–i . All structures were established by MS, IR, CHN, ¹H‐NMR and ¹³C‐NMR spectral data. J. Heterocyclic Chem., (2012).     

Efficient synthesis of 1‐substituted‐4‐phenyl‐1, 4‐dihydro‐5H‐tetrazole‐5‐thione and (1‐phenyl‐1H‐tetrazol‐5‐yl)thioacetyl derivatives

A new and convenient synthesis of a variety of N‐ and S‐substituted tetrazoles has been developed via azide and Mannich reaction methods. Compounds were characterized by elemental analysis, MALDI MS, and ¹H NMR data. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:637–643, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20353     

Head‐to‐head dimers in the zwitterion of 1‐hydroxy‐1‐phosphono‐3‐(1‐piperidino)propylidene‐1‐phosphonate (PHPBP)

The title compound, C₈H₁₉NO₇P₂, is a member of the bis­phosphonate family of therapeutic compounds. PHPBP has inner‐salt character, consisting of a negatively charged PO₃ group and a positively charged N atom. The six‐membered piperidine ring adopts an almost‐perfect chair conformation. The hydroxyl group and the N atom have gauche and trans conformations in relation to the O—C—C—C—N backbone, respectively. Hydrogen bonding is the main contributor to the packing in the crystal, which consists of head‐to‐head dimers formed through phosphonyl–phosphonyl hydrogen bonds, while O—H⋯O and N—H⋯O interactions join the dimers into a plane parallel to crystallographic b and c axes.     

1‐Carboxymethyl‐3‐methyl‐1H‐imidazol‐3‐ium chloride 2‐(3‐methyl‐1H‐imidazol‐3‐ium‐1‐yl)acetate monohydrate: a crystal stabilized by imidazolium zwitterions

The title compound, C₆H₉N₂O₂⁺·Cl⁻·C₆H₈N₂O₂·H₂O, contains one 2‐(3‐methyl‐1H‐imidazol‐3‐ium‐1‐yl)acetate inner salt molecule, one 1‐carboxymethyl‐3‐methyl‐1H‐imidazol‐3‐ium cation, one chloride ion and one water molecule. In the extended structure, chloride anions and water molecules are linked via O—H...Cl hydrogen bonds, forming an infinite one‐dimensional chain. The chloride anions are also linked by two weak C—H...Cl interactions to neighbouring methylene groups and imidazole rings. Two imidazolium moieties form a homoconjugated cation through a strong and asymmetric O—H...O hydrogen bond of 2.472 (2) Å. The IR spectrum shows a continuous D‐type absorption in the region below 1300 cm⁻¹ and is different to that of 1‐carboxymethyl‐3‐methylimidazolium chloride [Xuan, Wang & Xue (2012). Spectrochim. Acta Part A, 96 , 436–443].     

Selective Synthesis of 2‐Aryl‐1‐benzylated‐1H‐benzimidazoles

An efficient and simple procedure was developed for the green synthesis of various 2‐aryl‐1‐ben‐zylated‐1H‐benzimidazoles in high yields by condensation of o‐phenylenediamine with aldehydes with P₂O₅/SiO₂ as catalyst under solvent‐free and ambient conditions.     

Tacticity of poly‐α‐olefins from poly‐1‐hexene to poly‐1‐octadecene

A systematic study of the influence of the α‐olefin size, the catalyst stereospecificity and the reaction temperature was done on the catalytic activity and tacticity of poly‐α‐olefins from 1‐hexene to 1‐octadecene. The metallocenes used were rac‐Et[Ind₂]ZrCl₂ ( 1 ) and Me₂C[Cp(9‐Flu)]ZrCl₂ ( 2 ) to obtain isotactic and syndiotactic polyolefins. Some catalysts giving atactic polymers were also used in order to study all the possible ¹³C NMR pentades. Catalytic activities increased and isotacticity and syndiotacticity decreased with temperature, but no real trend was found with the α‐olefin size. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4744–4753, 2005     

Synthesis of some 3‐aryl‐1H‐isochromene‐1‐thiones

A rapid microwave‐accelerated thionation of some 3‐substitued isocoumarins to corresponding 1‐thio‐isocoumarins was achieved employing Lawesson's reagent under solventless conditions.     

N‐{(1E)‐Amino­[3‐methyl‐5‐(4‐methyl­phenyl)‐4,5‐di­hydro‐1H‐pyrazol‐1‐yl]­methyl­ene}‐1H‐imidazole‐1‐carbox­amide

In the title compound, C₁₆H₁₈N₆O, an N‐carbonyl­imidazole derivative of pyrazoline‐1‐carboximid­amide, the π‐electron density of the N atom in the 1‐position on the pyrazoline ring is delocalized through the amidine moiety and the adjacent carbonyl group. The imidazole ring, though coplanar with the rest of the mol­ecule, is deconjugated. The pyrazoline ring adopts a flat‐envelope conformation, having the substituted phenyl ring oriented perpendicular to the mean plane of the heterocycle. Both of the two potential hydrogen‐bond donors are involved in intramolecular hydrogen‐bonding interactions.     

1‐Phenyl‐5‐(piperidino­methyl)‐1H‐tetrazole

In the mol­ecule of the title 1,5‐disubstituted tetrazole, C₁₃H₁₇N₅, the tetrazole and benzene rings are not coplanar, having a dihedral angle of 42.96 (5)° between them. The piperidine fragment adopts a chair conformation, and there is a non‐classical intramolecular contact between the benzene H atom and the piperidine N atom. Intermolecular C—H⋯π interactions involving the piperidine C—H groups and the benzene rings are responsible for the formation of two‐dimensional networks, extending parallel to the ab plane. These networks are linked together into a three‐dimensional polymeric structure viaπ–π stacking interactions between the tetrazole rings of two adjacent mol­ecules.