Synthesis of 2,5-dihydroxy-3-(indol-3-yl)benzoquinones by acid-catalyzed condensation of indoles with 2,5-dichlorobenzoquinone

Three methods for the conjugate addition of indoles to 2,5-dichlorobenzoquinone have been developed. A wide variety of indoles substituted with halogen, alkyl, alkoxy, and aryl groups participate in anaerobic condensation reactions promoted by HCl, H2SO4, or CH3CO2H. The hydroquinone product is partially oxidized by excess dichlorobenzoquinone and fully converted to the 2,5-dichloro-3-(indol-3-yl)benzoquinone targets by DDQ or Ag2CO3 oxidation. 2,5-Dihydroxy-3-(indol-3-yl)benzoquinones can be obtained from the dichlorides by alkaline hydrolysis. The rotational characteristics of the biaryl bond created in these reactions have been examined by theoretical and spectroscopic methods.     

Investigation of brush-type chiral stationary phases based on O,O'-diaroyl tartardiamide and O,O'-bis-(arylcarbamoyl) tartardiamide

Four chiral organosilanes based on O,O'-dibenzoyl tartardiamide, O,O'-bis-(3,5-dimethylbenzoyl) tartardiamide, O,O'-bis-(phenylcarbamoyl) tartardiamide and O,O'-bis-[(3,5-dimethylphenyl)carbamoyl] tartardiamide were synthesized and immobilized on silica to afford corresponding brush-type chiral stationary phases (CSPs) with well-defined structures. Using 54 compounds containing a wide variety of structures as analytes, the enantioselectivities of the four CSPs were evaluated under normal-phase modes. 3,5-Dimethyl substituent in the aryl group was found to significantly affect the enantioselectivity of CSPs containing aryl ester moieties. Aryl carbamate moieties in CSPs were observed more beneficial for enantioseparation than aryl ester moieties. The additional hydrogen-bond donors (NH) present in the carbamate groups contributed greatly to the enantioselectivity of CSPs, which is contrary to the results that have been found in network-polymeric CSPs.     

Molecular and Crystal Structure Diversity,and Physical Properties of Tetrathiafulvalene Derivatives Substituted with Various Aryl Groups through Sulfur Bridges

A library of tetrathiafulvalene (TTF) derivatives ( TTF‐1 – TTF‐47 ) bearing aryl groups attached through sulfur bridges has been created. The peripheral aryl groups exert a significant influence on both the electronic and crystallographic properties of the resulting TTFs. These TTFs display broad absorption bands at 400–500 nm caused by intramolecular charge‐transfer transitions between the aryl groups and central TTF core, and their first redox potentials increase with increasing electron‐withdrawing ability of the aryl groups. In their crystal structures (22 examples), the central TTF cores adopt various conformations, including chair, half‐chair, boat, and planar conformations. Moreover, the peripheral aryl groups exhibit multiple alignment modes with respect to the central TTF core, caused by their rotation about the two C? S bonds of the sulfur bridges. The packing motifs of these TTFs depend on both the nature of the aryl groups and their spatial alignment modes. Driven by intermolecular van der Waals forces and π–π interactions between the aryl groups and between the aryl groups and the TTF core, these TTFs adopt various packing structures. As a typical example, TTF‐14 , an achiral molecule, adopts a helical chain stack through intermolecular atomic close contacts. Moreover, the molecular geometries and packing motifs of these TTFs are sensitive to environmental variation, as exemplified by TTF‐28 , which adopts three distinct crystal modifications with diverse molecular geometries and stacking modes under different crystallization conditions. This work indicates that these TTFs are potential candidates as electronic materials, as well as functional building blocks for supramolecular assembly.     

Synthesis, crystal structures, and properties of 6,12-diaryl-substituted indeno[1,2-b]fluorenes

Fused polycyclic indeno[1,2-b]fluorene derivatives with aryl substituents at the 6,12-positions have been prepared as a potential antiaromatic 20π electronic system. They showed strong absorptions in the visible region and amphoteric redox properties. The quinoid-type molecular structures were revealed by X-ray crystal-structure analysis, which indicated that the bond lengths of the quinoid unit depend on the aryl substituents. Whereas nucleus-independent chemical shift NICS(1) calculations indicate the antiaromatic nature of the s-indacene core, they have higher stability than substituted acene derivatives. The derivatives with difluorophenyl or anthryl groups were stable in solution. Vapor-deposited thin films showed ambipolar carrier transportation in the field-effect transistor devices.     

Chiral Ansa metallocenes with Cp ring-fused to thiophenes and pyrroles: syntheses, crystal structures, and isotactic polypropylene catalysts.

Syntheses, crystal structures, and polymerization data for new isospecific metallocenes (heterocenes) having cyclopentenyl ligands b-fused to substituted thiophenes (Tp) and pyrroles (Pyr) are reported. The C2- and C1-symmetric heterocenes are dimethylsilyl bridged, have methyl groups adjacent to the bridgehead carbon atoms, and have aryl substituents protruding in the front. rac-Me2Si(2,5-Me2-3-Ph-6-Cp[b]Tp)2ZrCl2/MAO (MAO = methyl alumoxanes) is the most active metallocene catalyst for polypropylene reported to date. rac-Me2Si(2,5-Me2-3-Ph-6-Cp[b]Tp)2ZrCl2 and rac-Me2Si(2,5-Me2-1-Ph-4-Cp[b]Pyr)2ZrCl2 have the same structure, and the former is 6 times more active, produces half the total enantiofacial errors, and is 3.5 times less regiospecific in propylene polymerizations at the same conditions. rac-Me2Si(2-Me-4-Ph-1-Ind)2ZrCl2/MAO is 3.5 times lower in activity than rac-Me2Si(2,5-Me2-3-Ph-6-Cp[b]Tp)2ZrCl2 catalyst, and while the former is the more stereospecific and the less regiospecific, the sum of these two enantioface errors is the same for both species. Fine-tuning the heterocene sterics by changing selected hydrogen atoms on the ligands to methyl groups influenced their catalyst activities, stereospecificites, regiospecificites, and isotactic polypropylene (IPP) Mw. Thus, both substituting a hydrogen atom adjacent to the phenyl ring with a methyl group on an azapentalenyl ligand system and replacing one and then two hydrogens on the phenyl ring with methyls on thiopentalenyl ligands provided increased polymer Tm and Mw with increasing ligand bulk. Polymer molecular weights are sensitive to and inversely proportional to MAO concentration, and the catalyst activities increase when hydrogen is added for molecular weight control. The polymer Tm values with the thiopentalenyls as TIBAL/[Ph3C][B(C6F5)4] systems were higher than with MAO as catalyst activator. A racemic C1, pseudo-meso complex with a hybrid dimethylsilyl-bridged 2-Me-4-Ph-1-Ind/2,5-Me2-4-Ph-1-Cp[b]Pyr ligand produced the first sample of IPP with all the steric pentad intensities fitting the enantiomorphic site control model. Speculative mechanistic considerations are offered regarding electronic effects of the heteroatoms and steric effects of the ligand structures, the preferred phenyl torsion angles, and anion effects.     

Helical secondary structures and supramolecular tilted chirality in N-terminal aryl amino acids with diversified optical activities

Helix structures at atomic/molecular level have not been found in self-assembled peptide seque nce with less than three residues.As β-sheet supramolecular secondary structures have been discovered in solidstate amino acids,we here report the conjugation of simple N-terminal aryl protecting group could give rise to helical supramolecular secondary structures in solid-state,which determines the optical activities of the adjacent aryl groups.The carboxylic acid-involved asymmetric H-bonds in N-te rminal aryl amino acids induce the emergence of super-helical structures of amino acid residues and aryl groups.In most cases,supramolecular tilted chirality of aryl groups is opposite to that of amino acid sequences,of which handedness and helical pitch are determined by the H-bond modalities.Determining correlation between supramolecular tilted chirality of aryl segments and their chiroptical activities is firstly unveiled,which was verified by the computational results based on density functional theory.Most aryl amino acids self-assembled by nanoprecipitation method via crystallization induced self-assembly into rigid one-dimensional microstructures with ultra-high Young's modulus.This study reveals the generic existence of chiral supramolecular structure s in aggregated amino acid derivatives and gives an in-depth investigation into the structural-property relationships,which could guide the rational design and screening of chiroptical supramolecular materials.     

Reaction of benzoyl chlorides with Huisgen's zwitterion: synthesis of functionalized 2,5-dihydro-1H-pyrroles and tetrasubstituted furans

The 1:1 intermediate generated by the addition of alkyl(aryl) isocyanides to dimethyl acetylenedicarboxylate is trapped by benzoyl chloride to yield functionalized 2,5-dihydro-1H-pyrroles. The presence of electron-withdrawing groups at the para position of benzoyl chloride leads to tetrasubstituted furans. The structures of these products were confirmed by single-crystal X-ray diffraction studies.     

2,5-二甲基-3,4-二乙酰基-1-芳基吡咯的合成

多取代吡咯;二乙酰基己二酮;取代苯胺;2;5-二甲基-3;4-二乙酰基-1-芳基吡咯的合成     

Copper-catalyzed intramolecular hydroalkoxylation of α-(1-hydroxy-1-alkyl- and -aryl)methylallenoates by a 5-endo mode for preparation of 2-alkyl- and 2-aryl-2,5-dihydrofurans

Ethyl α-(1-hydroxy-1-alkyl)methylallenoates and α-(1-hydroxy-1-aryl)methylallenoates containing not only electron-donating groups but also an electron-withdrawing group on the aryl group at the α-position have been shown to undergo an efficient and selective copper-catalyzed intramolecular hydroalkoxylation to give functionalized 3-ethoxycarbonyl-2-alkyl- and -aryl-2,5-dihydrofurans in good to excellent yields through a 5-endo mode.     

Synthesis,Photochromic, and Computational Studies of Dithienylethene‐Containing β‐Diketonate Derivatives and Their Near‐Infrared Photochromic Behavior Upon Coordination of a Boron(III) Center

A series of dithienylethene‐containing 1‐thienyl‐3‐aryl‐propane‐1,3‐diones (aryl=phenyl (Ph), thienyl (Th), and 4,5‐bis(2,5‐dimethylthiophen‐3‐yl)thiophen‐2‐yl (DTE‐Th)) and the corresponding boron(III) diketonates, (O^O)BR₂ (R=F, C₆F₅, and Ph), have been designed and synthesized. Their photophysical, electrochemical, and photochromic properties have been studied. Upon coordination of a boron(III) center, the closed forms of the dithienylethene‐containing β‐diketonates show near‐infrared response and the photochromic behavior was also found to be affected by the aryl substituents at the 3‐position of the β‐diketonates. Moreover, computational studies have been performed that help to provide an understanding of the effect of substituents on the photophysical and photochromic properties.     

Reaction of glyceraldehyde with aryl and alkyl chloroformates

A number of 2,5-bis(aryl- and alkyloxycarbonyloxymethylene)-3,6-bis(aryl- and alkoxycarbonyloxy)-1,4-dioxanes 5a-d have been prepared by the reaction of glyceraldehyde with aryl and alkyl chloroformates. Bis aryl carbonates were also formed under certain conditions in this reaction. Nuclear magnetic resonance analysis of 5c indicated that it existed in a chair conformation with all the substituents in an equatorial position.     

Synthesis,Crystal Structures,and Properties of 6,12‐Diaryl‐Substituted Indeno[1,2‐b]fluorenes

Fused polycyclic indeno[1,2‐b]fluorene derivatives with aryl substituents at the 6,12‐positions have been prepared as a potential antiaromatic 20π electronic system. They showed strong absorptions in the visible region and amphoteric redox properties. The quinoid‐type molecular structures were revealed by X‐ray crystal‐structure analysis, which indicated that the bond lengths of the quinoid unit depend on the aryl substituents. Whereas nucleus‐independent chemical shift NICS(1) calculations indicate the antiaromatic nature of the s‐indacene core, they have higher stability than substituted acene derivatives. The derivatives with difluorophenyl or anthryl groups were stable in solution. Vapor‐deposited thin films showed ambipolar carrier transportation in the field‐effect transistor devices.     

The synthesis, structures, and electrochemistry of 1′-heteroaryl-2,5-dimethylazaferrocenes

We report the synthesis of 1′-heteroaryl-2,5-dimethylazaferrocenes (heteroaryl = 2-bromothiophen-5-yl and 2-bromopyrid-6-yl) via palladium catalysed cross-coupling reactions along with their crystallographically determined structures. The newly synthesized compounds as well as the parent 2,5-dimethylazaferrocene have been investigated by cyclic voltammetry (CV) and were found to exhibit reversible first oxidations followed by an irreversible oxidation at considerably higher potential.     

Aromatic rigid chain copolymers. I. Synthesis,structure, and solubility of phenyl-substituted para-linked aromatic random copolyamides

Four 2,5-biphenylene based difunctional condensation monomers, such as 2,5-diphenyldicar-boxylic acid or phenylterephthalic acid (PTA), 2,5-bis(carbonylimino-4-benzoic acid)biphenyl (2,5-BCIBABP), 2,5-diaminobiphenyl hydrochloride (2,5-DABP.HCl) and 2,5-bis(iminocarbonyl-4-benzoic acid)biphenyl (2,5-BICBABP), have been synthesized and characterized. These monomers were polymerized in combination with terephthalic acid (TA) and p-phenylenediamine (PPD) via the phosphorylation reaction to prepare a series of phenyl-substituted random copolyamides having all amide groups attached to para-positions of the benzene rings. All the copolyamides have been characterized by solubility, solution viscosity, and by differential scanning calorimetry (DSC). Some of these copolyamides have unusual solubility in organic solvents such as N,N-dimethylacetamide (DMAc) and N-methyl-2-pyrrolidinone (NMP) containing dissolved lithium chloride. A few copolyamides were tested for lyotropic behavior and found to form anisotropic solutions at critical concentrations in organic solvents. A randomly distributed unsymmetrical phenyl substituent on the benzene ring of para-oriented wholly aromatic polyamides dramatically changes the solubility and melting point. The phenyl substituent on a terephthalic acid unit is more efficient in decreasing melting point and increasing solubility in organic solvents of aromatic polyamides than the one on a p-phenylenediamine unit. However, the former also introduces a more flexible link in the extended polyamide chain.     

One pot Pd(OAc)2-catalysed 2,5-diarylation of imidazoles derivatives

The regioselective 2- or 5-arylation of imidazole derivatives with aryl halides using palladium catalysts has been described in recent years; whereas the arylation at both C2 and C5 carbons of imidazoles in high yields has not been performed. We found conditions allowing the access to these 2,5-diarylimidazoles via a one pot reaction. The choice of the base was found to be crucial to obtain these products in high yields. Using CsOAc as the base, DMA as the solvent and only 2 mol % of the phosphine-free Pd(OAc)₂ the catalyst, the target 2,5-diarylated imidazoles were obtained in moderate to good yields with a wide variety of aryl bromides. Substituents such as fluoro, trifluoromethyl, formyl, acetyl, propionyl, ester, nitro or nitrile on the aryl bromide were tolerated. Sterically congested aryl bromides or heteroaryl bromides can also be employed. Surprisingly the nature of the substituent at position 1 on the imidazole derivative exhibits a huge influence on the reaction.     

Different supramolecular architectures mediated by different weak interactions in the crystals of three N‐aryl‐2,5‐dimethoxybenzenesulfonamides

The synthesis and evaluation of the pharmacological activities of molecules containing the sulfonamide moiety have attracted interest as these compounds are important pharmacophores. The crystal structures of three closely related N‐aryl‐2,5‐dimethoxybenzenesulfonamides, namely N‐(2,3‐dichlorophenyl)‐2,5‐dimethoxybenzenesulfonamide, C₁₄H₁₃Cl₂NO₄S, (I), N‐(2,4‐dichlorophenyl)‐2,5‐dimethoxybenzenesulfonamide, C₁₄H₁₃Cl₂NO₄S, (II), and N‐(2,4‐dimethylphenyl)‐2,5‐dimethoxybenzenesulfonamide, C₁₆H₁₉NO₄S, (III), are described. The asymmetric unit of (I) consists of two symmetry‐independent molecules, while those of (II) and (III) contain one molecule each. The molecular conformations are stabilized by different intramolecular interactions, viz. C—H…O interactions in (I), N—H…Cl and C—H…O interactions in (II), and C—H…O interactions in (III). The crystals of the three compounds display different supramolecular architectures built by various weak intermolecular interactions of the types C—H…O, C—H…Cl, C—H…π(aryl), π(aryl)–π(aryl) and Cl…Cl. A detailed Hirshfeld surface analysis of these compounds has also been conducted in order to understand the relationship between the crystal structures. The d _norm and shape‐index surfaces of (I)–(III) support the presence of various intermolecular interactions in the three structures. Analysis of the fingerprint plots reveals that the greatest contribution to the Hirshfeld surfaces is from H…H contacts, followed by H…O/O…H contacts. In addition, comparisons are made with the structures of some related compounds. Putative N—H…O hydrogen bonds are observed in 29 of the 30 reported structures, wherein the N—H…O hydrogen bonds form either C (4) chain motifs or R ₂²(8) rings. Further comparison reveals that the characteristics of the N—H…O hydrogen‐bond motifs, the presence of other interactions and the resultant supramolecular architecture is largely decided by the position of the substituents on the benzenesulfonyl ring, with the nature and position of the substituents on the aniline ring exerting little effect. On the other hand, the crystal structures of (I)–(III) display several weak interactions other than the common N—H…O hydrogen bonds, resulting in supramolecular architectures varying from one‐ to three‐dimensional depending on the nature and position of the substituents on the aniline ring.     

Synthesis and auration of primary and di-primary heteroaryl-phosphines

Convenient high-yield syntheses of the primary and di-primary heteroaryl-phosphines R-PH2 and H2P-R'-PH2(with R = 2-thienyl, 2-furyl, and R'= 2,5-thiophenediyl, 2,5-furandiyl, respectively) are presented. The products and a set of precursor molecules have been characterized by analytical and spectral data, and the crystal structures of selected molecules have been determined: 2-C4H3O-PCl2, 2,5-(Cl2P)2C4H2O, 2,5-[(Et2N)2P]2C4H2E (with E = O, S). In the crystals, the two molecules with -PCl2 substituents adopt trans conformations, while the other two have the -P(NEt2)2 groups rotated into a twist conformation. The reaction of the thienyl compounds with tris[(tert-phosphine)gold]oxonium tetrafluoroborates gave almost quantitative yields of the tri- and hexanuclear gold complexes, respectively: {2-C4H3S-P[Au(PR3)]3}+BF4- and [2,5-{[(R3P)Au]3P}2C4H2S]2+(BF4(-)2, (R =tBu, Ph). The structures of the compounds with R3P =tBu3P ligands have been determined. In both cases the [2-C4H3/2S-P] units cap triangles of gold atoms in an array that can be described as three [Au(PR3)]+ cations bridged by a phosphido dianion (RP)2-.     

The double reduction of cyclic sulfonamides for the synthesis of (4S-Phenylpyrrolidin-2R-yl)methanol and 2S-methyl-4S-phenylpyrrolidine

The synthesis of (4S-phenylpyrrolidin-2R-yl)methanol and 2S-methyl-4S-phenylpyrrolidine has been achieved via the double reduction of their cyclic sulfonamide precursors which themselves were prepared following the stereoselective intramolecular Heck reaction of a chiral pool derived 2,5-dihydropyrrole. We have recently described a process whereby cyclic aryl sulfonamides, such as 2, are reductively ring-opened to furnish amino products in which the aryl group is incorporated in the final compound. (Evans, P.; McCabe, T.; Morgan, B. S.; Reau, S. Org. Lett. 2005, 7, 43.) The precursors for this reaction were assembled using an intramolecular Heck reaction followed by reduction of the alkene. Overall, this sequence represents an efficient means to construct molecules of this type in which the aryl sulfonyl moiety acts as both an N-protecting group and as an aryl donor. Use of Benkeser's stronger reducing conditions enables molecules such as 4 to be prepared in which both the sulfonamide functional group and the aromaticity of the aryl substituent have been destroyed.     

One-pot multicomponent synthesis of functionalized 2,5-disubstituted-1,3,4-thiadiazine derivatives

An atom-efficient and environmentally friendly approach to the synthesis of 2,5-disubstituted-1,3,4-thidiazine derivatives has been developed. These compounds were synthesized by a reaction of 2-(2-bromoacetyl)benzofuran and thiocarbohydrazide with various aryl aldehydes, acetylacetones, and pthalic anhydrides in good yields. The advantages of this methodology are mild reaction conditions, easy workup procedure, clean reaction profile, shorter reaction time, and a wide range of substrate applicability. The structures of all synthesized compounds were confirmed from their analytical and spectral data.     

Mild conditions for Pd-catalyzed carboamination of N-protected hex-4-enylamines and 1-, 3-, and 4-substituted pent-4-enylamines. Scope, limitations, and mechanism of pyrrolidine formation

The use of the weak base Cs2CO3 in Pd-catalyzed carboamination reactions of N-protected gamma-aminoalkenes with aryl bromides leads to greatly increased tolerance of functional groups and alkene substitution. Substrates derived from (E)- or (Z)-hex-4-enylamines are stereospecifically converted to 2,1'-disubstituted pyrrolidine products that result from suprafacial addition of the nitrogen atom and the aryl group across the alkene. Transformations of 4-substituted pent-4-enylamine derivatives proceed in high yield to afford 2,2-disubstituted products, and cis-2,5- or trans-2,3-disubstituted pyrrolidines are generated in good yield with excellent diastereoselectivity from N-protected pent-4-enylamines bearing substituents at C1 or C3. The reactions tolerate a broad array of functional groups, including esters, nitro groups, and enolizable ketones. The scope and limitations of these transformations are described in detail, along with models that account for the observed product stereochemistry. In addition, deuterium labeling experiments, which indicate these reactions proceed via syn-aminopalladation of intermediate palladium(aryl)(amido)complexes regardless of degree of alkene substitution or reaction conditions, are also discussed.