Z and E isomers of butenedioic acid with 2‐amino‐1,3‐thiazole: 2‐amino‐1,3‐thiazolium hydrogen maleate and 2‐amino‐1,3‐thiazolium hydrogen fumarate

Maleic acid and fumaric acid, the Z and E isomers of butenedioic acid, form 1:1 adducts with 2‐amino‐1,3‐thiazole, namely 2‐amino‐1,3‐thiazolium hydrogen maleate (2ATHM), C₃H₅N₂S⁺·C₄H₃O₄⁻, and 2‐amino‐1,3‐thiazolium hydrogen fumarate (2ATHF), C₃H₅N₂S⁺·C₄H₃O₄⁻, respectively. In both compounds, protonation of the ring N atom of the 2‐amino‐1,3‐thiazole and deprotonation of one of the carboxyl groups are observed. The asymmetric unit of 2ATHF contains three independent ion pairs. The hydrogen maleate ion of 2ATHM shows a short intramolecular O—H...O hydrogen bond with an O...O distance of 2.4663 (19) Å. An extensive hydrogen‐bonded network is observed in both compounds, involving N—H...O and O—H...O hydrogen bonds. 2ATHM forms two‐dimensional sheets parallel to the ab plane, extending as independent parallel sheets along the c axis, whereas 2ATHF forms two‐dimensional zigzag layers parallel to the bc plane, extending as independent parallel layers along the a axis.     

5‐Hydroxyalkyl derivatives of tert‐butyl 2‐oxo‐2,5‐dihydro‐1H‐pyrrole‐1‐carboxylate: diastereoselectivity of the Mukaiyama crossed‐aldol‐type reaction

The title compounds, rac‐(1′R,2R)‐tert‐butyl 2‐(1′‐hydroxyethyl)‐3‐(2‐nitrophenyl)‐5‐oxo‐2,5‐dihydro‐1H‐pyrrole‐1‐carboxylate, C₁₇H₂₀N₂O₆, (I), rac‐(1′S,2R)‐tert‐butyl 2‐[1′‐hydroxy‐3′‐(methoxycarbonyl)propyl]‐3‐(2‐nitrophenyl)‐5‐oxo‐2,5‐dihydro‐1H‐pyrrole‐1‐carboxylate, C₂₀H₂₄N₂O₈, (II), and rac‐(1′S,2R)‐tert‐butyl 2‐(4′‐bromo‐1′‐hydroxybutyl)‐5‐oxo‐2,5‐dihydro‐1H‐pyrrole‐1‐carboxylate, C₁₃H₂₀BrNO₄, (III), are 5‐hydroxyalkyl derivatives of tert‐butyl 2‐oxo‐2,5‐dihydropyrrole‐1‐carboxylate. In all three compounds, the tert‐butoxycarbonyl (Boc) unit is orientated in the same manner with respect to the mean plane through the 2‐oxo‐2,5‐dihydro‐1H‐pyrrole ring. The hydroxyl substituent at one of the newly created chiral centres, which have relative R,R stereochemistry, is trans with respect to the oxo group of the pyrrole ring in (I), synthesized using acetaldehyde. When a larger aldehyde was used, as in compounds (II) and (III), the hydroxyl substituent was found to be cis with respect to the oxo group of the pyrrole ring. Here, the relative stereochemistry of the newly created chiral centres is R,S. In compound (I), O—H...O hydrogen bonding leads to an interesting hexagonal arrangement of symmetry‐related molecules. In (II) and (III), the hydroxyl groups are involved in bifurcated O—H...O hydrogen bonds, and centrosymmetric hydrogen‐bonded dimers are formed. The Mukaiyama crossed‐aldol‐type reaction was successful when using the 2‐nitrophenyl‐substituted hydroxypyrrole, or the unsubstituted hydroxypyrrole, and boron trifluoride diethyl ether as catalyst. The synthetic procedure leads to a syn configuration of the two newly created chiral centres in all three compounds.     

4‐Ethynyl‐4‐hydroxycyclohexan‐1‐one and 4‐ethynyl‐4‐hydroxy‐2,3,5,6‐tetramethylcyclohexa‐2,5‐dien‐1‐one

The title compounds, C₈H₁₀O₂, (I), and C₁₂H₁₄O₂, (II), occurred as by‐products in the controlled synthesis of a series of bis­(gem‐alkynols), prepared as part of an extensive study of synthon formation in simple gem‐alkynol derivatives. The two 4‐(gem‐alkynol)‐1‐ones crystallize in space group P2₁/c, (I) with Z′ = 1 and (II) with Z′ = 2. Both structures are dominated by O—H?O=C hydrogen bonds, which form simple chains in the cyclo­hexane derivative, (I), and centrosymmetric dimers, of both symmetry‐independent mol­ecules, in the cyclo­hexa‐2,5‐diene, (II). These strong synthons are further stabilized by C[triple‐bond]C—H?O=C, C_methylene—H?O(H) and C_methyl—H?O(H) interactions. The direct intermolecular interactions between donors and acceptors in the gem‐alkynol group, which characterize the bis­(gem‐alkynol) analogues of (I) and (II), are not present in the ketone derivatives studied here.     

Determination of diphenylarsinic acid and phenylarsonic acid,the degradation products of organoarsenic chemical warfare agents,in well water by HPLC–ICP‐MS

Diphenylarsinic acid (DPAA) and phenylarsonic acid (PAA), which were degradation products of organoarsenic chemical warfare agents used as sternutatory gas, were detected in the well water at Kamisu, Ibaraki Prefecture, Japan. The standard material of DPAA was synthesized with aqueous arsenic acid and phenylhydrazine in order to determine organic arsenic compounds in well water. The DPAA showed a protonated ion at m/z 263 [M + H]⁺ and a loss of H₂O ion at m/z 245 [M + H ? H₂O]⁺ from protonated ion by the electrospray ionization time‐of‐flight mass spectrometry. The quantitative analysis of DPAA and PAA was performed by high‐performance liquid chromatography inductively coupled plasma mass spectrometry and the system worked well for limpid liquid samples such as well water. Copyright © 2005 John Wiley & Sons, Ltd.     

4‐(4‐Chloro­benzyl­ideneamino)‐1,5‐dimethyl‐2‐phenyl‐1H‐pyrazol‐3(2H)‐one and 4‐(2‐chloro­benzyl­idene­amino)‐1,5‐dimethyl‐2‐phenyl‐1H‐pyrazol‐3(2H)‐one

The two title compounds, both with formula C₁₈H₁₆ClN₃O, are structurally similar Schiff bases derived from the condensation of 4‐chloro­benzaldehyde or 2‐chloro­benzaldehyde with 4‐amino­anti­pyrine in methanol solution. As expected, both compounds adopt trans configurations about the central C=N bonds. In the crystal structure of the 4‐chloro analogue, mol­ecules are linked through weak C—H⋯O hydrogen bonds, forming chains running along the a axis. In the crystal structure of the 2‐chloro analogue, mol­ecules are linked through weak C—H⋯O and C—H⋯Cl hydrogen bonds, forming layers parallel to the ab plane.     

pH‐Directed Synthesis of Two Luminescent Zinc(II) Coordination Compounds based on 5‐Aminotetrazole‐1‐propanoic Acid

Two Zn^II‐tetrazole‐carboxylate coordination compounds are reported, mononuclear [Zn(atzpa)₂(H₂O)₄] · 2H₂O ( 1 ) and one‐dimensional [Zn(atzpa)₂(H₂O)₂]_n ( 2 ), derived from 5‐aminotetrazole‐1‐propanoic acid (Hatzpa). The structures of both compounds are determined by the pH value of the reaction system. The luminescence properties of Hatzpa and the compounds were investigated at room temperature in the solid state. Furthermore, differential scanning calorimetry (DSC) and thermogravimetric‐differential thermogravimetric (TG‐DTG) analyses were applied to evaluate the thermal decomposition behavior of such compounds. The relevant thermodynamic parameters (ΔH, ΔS, and ΔG) of the decompostion process of compound 1 were calculated, as well.     

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).     

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°.     

2,3:4,6‐Di‐O‐isopropylidene‐α‐l‐sorbofuranose and 2,3‐O‐isopropylidene‐α‐l‐sorbofuranose

In the title compounds, C₁₂H₂₀O₆, (I), and C₉H₁₆O₆, (II), the five‐membered furanose ring adopts a ⁴T₃ conformation and the five‐membered 1,3‐dioxolane ring adopts an E₃ conformation. The six‐membered 1,3‐dioxane ring in (I) adopts an almost ideal ^OC₃ conformation. The hydrogen‐bonding patterns for these compounds differ substantially: (I) features just one intramolecular O—H...O hydrogen bond [O...O = 2.933 (3) Å], whereas (II) exhibits, apart from the corresponding intramolecular O—H...O hydrogen bond [O...O = 2.7638 (13) Å], two intermolecular bonds of this type [O...O = 2.7708 (13) and 2.7730 (12) Å]. This study illustrates both the similarity between the conformations of furanose, 1,3‐dioxolane and 1,3‐dioxane rings in analogous isopropylidene‐substituted carbohydrate structures and the only negligible influence of the presence of a 1,3‐dioxane ring on the conformations of furanose and 1,3‐dioxolane rings. In addition, in comparison with reported analogs, replacement of the –CH₂OH group at the C1‐furanose position by another group can considerably affect the conformation of the 1,3‐dioxolane ring.     

2‐(4‐Bromophenyl)‐1,2‐dihydropyrimido[1,2‐a]benzimidazol‐4(3H)‐one and 4‐(4‐methylphenyl)‐3,4‐dihydropyrimido[1,2‐a]benzimidazol‐2(1H)‐one form hydrogen‐bonded base‐paired dimers

The title compounds, 2‐(4‐bromo­phenyl)‐1,2‐di­hydro­pyrimido­[1,2‐a]­benzimidazol‐4‐(3H)‐one, C₁₆H₁₂Br­N₃O, (IVa), and 4‐(4‐methylphenyl)‐3,4‐dihydropyrimido[1,2‐a]benzimidazol‐2‐(1H)‐one, C₁₇H₁₅N₃O, (Vb), both form R(8) centrosymmetric dimers via N—H?N hydrogen bonds. The N?N distance is 2.943 (3) Å for (IVa) and 2.8481 (16) Å for (Vb), with the corresponding N—H?N angles being 129 and 167°, respectively. However, in other respects, the supra­molecular structures of the two compounds differ. Both compounds contain different C—H?π interactions, in which the C—H?π(centroid) distances are 2.59 and 2.47 Å for (IVa) and (Vb), respectively (the latter being a short distance), with C—H?π(centroid) angles of 158 and 159°, respectively. The supramolecular structures also differ, with a short Br?O distance of 3.117 (2) Å in bromo derivative (IVa), and a C—H?O interaction with a C?O distance of 3.2561 (19) Å and a C—H?O angle of 127° in tolyl system (Vb). The di­hydro­pyrimido part of (Vb) is disordered, with a ratio of the major and minor components of 0.9:0.1. The disorder consists of two non‐interchangeable envelope conformers, each with an equatorial tolyl group and an axial methine H atom.     

Effect of the position of a methoxy substituent on the antimicrobial activity and crystal structures of 4‐methyl‐1,6‐diphenylpyrimidine‐2(1H)‐selenone derivatives

Derivatives of pyrimidine‐2(1H)‐selenone are a group of compounds with very strong antimicrobial activity. In order to study the effect of the position of the methoxy substituent on biological activity, molecular geometry and intermolecular interactions in the crystal, three derivatives were prepared and evaluated with respect to their antimicrobial activities, and their crystal structures were determined by X‐ray diffraction. The investigated compounds, namely, 1‐(X‐methoxyphenyl)‐4‐methyl‐6‐phenylpyrimidine‐2(1H)‐selenones (X = 2, 3 and 4 for 1 , 2 and 3 , respectively), C₁₈H₁₆N₂OSe, showed very strong activity against selected strains of Gram‐positive bacteria and fungi. Two compounds, 1 and 2 , crystallize in the monoclinic space group P2₁/c, while 3 crystallizes in the space group P2₁/n; 1 has two molecules in the asymmetric unit and the other two ( 2 and 3 ) have one molecule. The geometries of the investigated compounds differ slightly in the mutual orientations of the aromatic and pyrimidineselenone rings. The O atom in 1 stabilizes the conformation of the molecules via intramolecular C—H…O hydrogen bonding. The packing of molecules is determined by weak C—H…N and C—H…Se intermolecular interactions and additionally in 1 and 2 by C—H…O intermolecular interactions. The introduction of the methoxy substituent results in greater selectivity of the investigated compounds.     

7‐Amino‐2‐methylsulfanyl‐1,2,4‐triazolo[1,5‐a]pyrimidine‐6‐carboxylic acid as the dimethylformamide and water monosolvates at 293 K

The molecular structure of 7‐amino‐2‐methylsulfanyl‐1,2,4‐triazolo[1,5‐a]pyrimidine‐6‐carboxylic acid is reported in two crystal environments, viz. as the dimethylformamide (DMF) monosolvate, C₇H₇N₅O₂S·C₃H₇NO, (I), and as the monohydrate, C₇H₇N₅O₂S·H₂O, (II), both at 293 (2) K. The triazolo[1,5‐a]pyrimidine molecule is of interest with respect to the possible biological activity of its coordination compounds. While the DMF solvate exhibits a layered structural arrangement through N...O hydrogen‐bonding interactions, the monohydrate displays a network of intermolecular O...O and N...O hydrogen bonds assisted by cocrystallized water molecules and weak π–π stacking interactions, leading to a different three‐dimensional supramolecular architecture. Based on results from topological analyses of the electron‐density distribution in X—H...O (X = O, N and C) regions, hydrogen‐bonding energies have been estimated from structural information only, enabling the characterization of hydrogen‐bond graph energies.     

Novel chalcones derived from 2‐chloro‐3‐formyl‐6‐methylquinoline

Molecules of (E)‐3‐(2‐chloro‐6‐methylquinolin‐3‐yl)‐1‐(5‐iodo‐2‐thienyl)prop‐2‐en‐1‐one, C₁₇H₁₁ClINOS, (I), and (E)‐3‐(2‐chloro‐6‐methylquinolin‐3‐yl)‐1‐(5‐methyl‐2‐furyl)prop‐2‐en‐1‐one, C₁₈H₁₄ClNO₂, (II), adopt conformations slightly twisted from coplanarity. Both structures are devoid of classical hydrogen bonds. However, nonclassical C—H...O/N interactions [with C...O = 3.146 (5) Å and C...N = 3.487 (3) Å] link the molecules into chains extended along the b axis in (I) and form dimers with an R₂²(8) motif in (II). The structural analysis of these compounds provides an insight into the correlation between molecular structures and intermolecular interactions in compounds for drug development.     

Facile Synthesis of N‐(Benzyl‐1H‐1,2,3‐Triazol‐5‐yl) Methyl)‐4‐(6‐Methoxybenzo [d] Thiazol‐2‐yl)‐2‐Nitrobenzamides via Click Chemistry

A series of novel N‐((l‐benzyl‐lH‐l,2,3‐triazol‐5‐yl) methyl)‐4‐(6‐methoxy benzo[d ]thiazol‐2‐yl)‐2‐nitrobenzamide derivatives were prepared from 4‐(6‐methoxybenzo[d ]thiazol‐2‐yl)‐2‐nitro‐N‐(prop‐2‐ynyl) benzamide with benzyl azides by using click reaction (copper‐catalyzed Huisgen 1,3‐dipolar cycloaddition reaction) in the presence of CuSO₄.5H₂O and sodium ascaorbate. All the newly synthesized compounds were evaluated further in vitro antimicrobial activity against Gram‐positive bacteria (Staphylococcus aureus and Bacillus subtillis ), Gram‐negative bacteria (Echerichia coli and Pseudomonas aeuroginosa ), and fungi (Aspergillus niger and Aspergillusfumigatus ) strains. The new compounds were characterized based on spectroscopic evidence. Among them compounds 10a , 10h , and 10i were showed promising activity when compared with standard drugs Ciprofloxacin and Miconazole.     

Bis(μ‐benzene‐1,2‐dicarboxylato)bis{aqua[2‐(2‐chloro‐6‐fluorophenyl)‐1H‐imidazo[4,5‐f][1,10]phenanthroline]cadmium(II)} and its zinc(II) analogue

In the isomorphous title compounds, [Cd₂(C₈H₄O₄)₂(C₁₉H₁₀ClFN₄)₂(H₂O)₂] and [Zn₂(C₈H₄O₄)₂(C₁₉H₁₀ClFN₄)₂(H₂O)₂], the Cd^II centre is seven‐coordinated by two N atoms from one [2‐(2‐chloro‐6‐fluorophenyl)‐1H‐imidazo[4,5‐f][1,10]phenanthroline (L) ligand, one water O atom and four carboxylate O atoms from two different benzene‐1,2‐dicarboxylate (1,2‐bdc) ligands in a distorted pentagonal–bipyramidal coordination, while the Zn^II centre is six‐coordinated by two N atoms from one L ligand, one water O atom and three carboxylate O atoms from two different 1,2‐bdc ligands in a distorted octahedral coordination. Each pair of adjacent metal centres is bridged by two 1,2‐bdc ligands to form a dimeric structure. In the dimer, each L ligand coordinates one metal centre. The dimer is centrosymmetric, with a crystallographic inversion centre midway between the two metal centres. The aromatic interactions lead the dimers to form a two‐dimensional supramolecular architecture. Finally, O—H...O and N—H...O hydrogen bonds reinforce the two‐dimensional structures of the two compounds.     

Synthesis of Monospiro‐2‐amino‐4H‐pyran Derivatives Catalyzed by Propane‐1‐sulfonic Acid‐Modified Magnetic Hydroxyapatite Nanoparticles

Various monospiro‐2‐amino‐4H‐pyran derivatives have been synthesized in high yields (via three‐component coupling of ninhydrin or different isatins with malononitrile and 1,3‐dicarbonyl compounds) in the presence of catalytic amount of propane‐1‐sulfonic acid‐modified magnetic hydroxyapatite nanoparticles in H₂O. Due to easy magnetic removal of nanocatalyst and applying of H₂O as solvent, this protocol enhanced product purity, and promised economic as well as environmental benefits, exemplifying a waste‐free chemistry. More importantly, the catalyst could be easily recycled for more than five times without loss of activity.     

Mononuclear nickel(II) and zinc(II) complexes with deprotonated forms of the tripodal hexadentate ligand 1,3‐bis(2‐hydroxybenzylidene)‐2‐(2‐hydroxybenzylideneaminomethyl)‐2‐methylpropane‐1,3‐diamine

In the crystal structures of both title compounds, [1,3‐bis(2‐hydroxybenzylidene)‐2‐methyl‐2‐(2‐oxidobenzylideneaminomethyl)propane‐1,3‐diamine]nickel(II) [2‐(2‐hydroxybenzylideneaminomethyl)‐2‐methyl‐1,3‐bis(2‐oxidobenzylidene)propane‐1,3‐diamine]nickel(II) chloride methanol disolvate, [Ni(C₂₆H_25.5N₃O₃)]₂Cl·2CH₄O, and [1,3‐bis(2‐hydroxybenzylidene)‐2‐methyl‐2‐(2‐oxidobenzylideneaminomethyl)propane‐1,3‐diamine]zinc(II) perchlorate [2‐(2‐hydroxybenzylideneaminomethyl)‐2‐methyl‐1,3‐bis(2‐oxidobenzylidene)propane‐1,3‐diamine]zinc(II) methanol trisolvate, [Zn(C₂₆H₂₅N₃O₃)]ClO₄·[Zn(C₂₆H₂₆N₃O₃)]·3CH₄O, the 3d metal ion is in an approximately octahedral environment composed of three facially coordinated imine N atoms and three phenol O atoms. The two mononuclear units are linked by three phenol–phenolate O—H...O hydrogen bonds to form a dimeric structure. In the Ni compound, the asymmetric unit consists of one mononuclear unit, one‐half of a chloride anion and a methanol solvent molecule. In the O—H...O hydrogen bonds, two H atoms are located near the centre of O...O and one H atom is disordered over two positions. The Ni^II compound is thus formulated as [Ni(H_1.5L)]₂Cl·2CH₃OH [H₃L is 1,3‐bis(2‐hydroxybenzylidene)‐2‐(2‐hydroxybenzylideneaminomethyl)‐2‐methylpropane‐1,3‐diamine]. In the analogous Zn^II compound, the asymmetric unit consists of two crystallographically independent mononuclear units, one perchlorate anion and three methanol solvent molecules. The mode of hydrogen bonding connecting the two mononuclear units is slightly different, and the formula can be written as [Zn(H₂L)]ClO₄·[Zn(HL)]·3CH₃OH. In both compounds, each mononuclear unit is chiral with either a Δ or a Λ configuration because of the screw coordination arrangement of the achiral tripodal ligand around the 3d metal ion. In the dimeric structure, molecules with Δ–Δ and Λ–Λ pairs co‐exist in the crystal structure to form a racemic crystal. A notable difference is observed between the M—O(phenol) and M—O(phenolate) bond lengths, the former being longer than the latter. In addition, as the ionic radius of the metal ion decreases, the M—O and M—N bond distances decrease.     

Intramolecular Metal‐Free Oxidative Aryl–Aryl Coupling: An Unusual Hypervalent‐Iodine‐Mediated Rearrangement of 2‐Substituted N‐Phenylbenzamides

Hypervalent‐iodine‐mediated oxidative coupling of the two aryl groups in either 2‐acylamino‐N‐phenyl‐benzamides or 2‐hydroxy‐N‐phenylbenzamides, with concomitant insertion of the ortho‐substituted N or O atom into the tether, has been described for the first time. This unusual metal‐free rearrangement reaction involves an oxidative C(sp²)? C(sp²) aryl–aryl bond formation, cleavage of a C(sp²)? C(O) bond, and a lactamization/lactonization. Furthermore, unsymmetrical diaryl compounds can be easily obtained by removing the tether within the cyclized product.     

Hydrogen‐bonding patterns in 3‐alkyl‐3‐hydroxyindolin‐2‐ones

The molecules of racemic 3‐benzoylmethyl‐3‐hydroxyindolin‐2‐one, C₁₆H₁₃NO₃, (I), are linked by a combination of N—H...O and O—H...O hydrogen bonds into a chain of centrosymmetric edge‐fused R₂²(10) and R₄⁴(12) rings. Five monosubstituted analogues of (I), namely racemic 3‐hydroxy‐3‐[(4‐methylbenzoyl)methyl]indolin‐2‐one, C₁₇H₁₅NO₃, (II), racemic 3‐[(4‐fluorobenzoyl)methyl]‐3‐hydroxyindolin‐2‐one, C₁₆H₁₂FNO₃, (III), racemic 3‐[(4‐chlorobenzoyl)methyl]‐3‐hydroxyindolin‐2‐one, C₁₆H₁₂ClNO₃, (IV), racemic 3‐[(4‐bromobenzoyl)methyl]‐3‐hydroxyindolin‐2‐one, C₁₆H₁₂BrNO₃, (V), and racemic 3‐hydroxy‐3‐[(4‐nitrobenzoyl)methyl]indolin‐2‐one, C₁₆H₁₂N₂O₅, (VI), are isomorphous in space group P. In each of compounds (II)–(VI), a combination of N—H...O and O—H...O hydrogen bonds generates a chain of centrosymmetric edge‐fused R₂²(8) and R₂²(10) rings, and these chains are linked into sheets by an aromatic π–π stacking interaction. No two of the structures of (II)–(VI) exhibit the same combination of weak hydrogen bonds of C—H...O and C—H...π(arene) types. The molecules of racemic 3‐hydroxy‐3‐(2‐thienylcarbonylmethyl)indolin‐2‐one, C₁₄H₁₁NO₃S, (VII), form hydrogen‐bonded chains very similar to those in (II)–(VI), but here the sheet formation depends upon a weak π–π stacking interaction between thienyl rings. Comparisons are drawn between the crystal structures of compounds (I)–(VII) and those of some recently reported analogues having no aromatic group in the side chain.     

Similarities and differences in the structures of 5‐bromo‐6‐hydroxy‐7,8‐dimethylchroman‐2‐one and 6‐hydroxy‐7,8‐dimethyl‐5‐nitrochroman‐2‐one

The title compounds, C₁₁H₁₁BrO₃, (I), and C₁₁H₁₁NO₅, (II), respectively, are derivatives of 6‐hydroxy‐5,7,8‐trimethylchroman‐2‐one substituted at the 5‐position by a Br atom in (I) and by a nitro group in (II). The pyranone rings in both molecules adopt half‐chair conformations, and intramolecular O—H...Br [in (I)] and O—H...O_nitro [in (II)] hydrogen bonds affect the dispositions of the hydroxy groups. Classical intermolecular O—H...O hydrogen bonds are found in both molecules but play quite dissimilar roles in the crystal structures. In (I), O—H...O hydrogen bonds form zigzag C(9) chains of molecules along the a axis. Because of the tetragonal symmetry, similar chains also form along b. In (II), however, similar contacts involving an O atom of the nitro group form inversion dimers and generate R₂²(12) rings. These also result in a close intermolecular O...O contact of 2.686 (4) Å. For (I), four additional C—H...O hydrogen bonds combine with π–π stacking interactions between the benzene rings to build an extensive three‐dimensional network with molecules stacked along the c axis. The packing in (II) is much simpler and centres on the inversion dimers formed through O—H...O contacts. These dimers are stacked through additional C—H...O hydrogen bonds, and further weak C—H...O interactions generate a three‐dimensional network of dimer stacks.