Synthesis of 5-arylhistidines via a Suzuki-Miyaura cross-coupling

Microwave irradiation efficiently promoted the Suzuki-Miyaura reaction of a 5-bromohistidine with various arylboronic acids in the presence of a palladium catalyst. This methodology allowed the synthesis of histidines substituted at position 5 of the imidazole ring with a phenyl, a substituted phenyl, a pyridyl or a thienyl ring. The corresponding 5-arylhistidines were obtained in moderate to good yields.     

Aromatic polyamides with pendant urea moieties

This work describes six novel aromatic polyamides with bulky pendant groups, each having a polyisophthalamide backbone substituted with different urea groups in ring position 5 of the diacid or the diamine residue. Thus, one of the nitrogen atoms of the urea is chemically anchored to the main rigid polyamide chain, while the other nitrogen atom is substituted by phenyl, nitrophenyl, naphthyl, and phenylureidophenyl groups. The polyamides are amorphous and soluble in polar aprotic solvents. They demonstrate a film‐forming capability with outstanding mechanical properties, and exhibit moderate thermal resistance in nitrogen and oxygen atmospheres. The urea group imparts hydrophilicity to the polymers, and facilitates the future preparation of specialty polymers through the easy chemical modification of this group. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4026–4036, 2007     

3-乙酰基取代吡咯衍生物的合成及其晶体结构

本文通过Knorr合成法制备了四个3-位乙酰基取代的吡咯衍生物:1, 2-二甲基-4-异丙基-5-苯基-3-乙酰基-吡咯(5a); 1, 2, 4-三甲基-5-对甲氧苯基-3-乙酰基-吡咯(5b); 1, 2, 5-三甲基-4-苯基-3-乙酰基-吡咯(5c); 1, 2, 5-三甲基-4-对甲氧苯基-3-乙酰基-吡咯(5d)。通过红外, 质谱, 核磁等方法对其结构进行了表征。测定了其中三个化合物的晶体结构。对这类吡咯环上4或5-位有芳环取代基时化合物的晶体结构特征进行了扼要讨论, 晶体衍射实验结果表明,4, 5-位上的芳环与吡咯环本身处于非共平面结构。     

NMR Characterization of Substituted Aromatic Poly (Ether Sulofone)s

Abstract

The synthesis of a variety of substituted bisphenol A polysulfones, including nitro, amino, aminomethyl, ethyl, and methyl derivatives, is described. Nuclear magnetic resonance (NMR) (both proton and carbon, and several 2-D experiments) data confirm conclusions on the substitution site based on arguments on inductive effects in the phenyl rings. The proton ortho to the oxygen in the bisphenol A (BPA) residue is replaced in electrophilic substitution reactions. The degree of substitution was also calculated from the NMR results. The ethyl and methyl derivatives were expected, from the starting reactants, to each have a BPA ring substituted. The NMR data showed that, on the average, this is true. The nitro derivative also has substitution in every BPA ring, while the amino and aminomethyl derivatives have only intermittent BPA rings substituted. Measured degrees of substitution (DS) varied from 0.11 to 2.25.     

Synthesis of 5-iodopyrrolo[1,2-a]quinolines and indolo[1,2-a]quinolines via iodine-mediated electrophilic and regioselective 6-endo-dig ring closure

The endo-cyclic ring closure of 1-(2-(substituted ethynyl)phenyl)-1H-pyrroles 3a-t and 1-(2-(substituted ethynyl)phenyl)-H-indole 4a-o mediated by Lewis acid (I(2)) under mild conditions afforded substituted 5-iodopyrrolo[1,2-a]quinolines 5a-t and 5-iodoindolo[1,2-a]quinolines 6a-o in good to excellent yields. The reaction shows selective C-C bond formation on the more electrophilic alkynyl carbon, resulting in the regioselective 6-endo-dig-cyclized product. Iodo derivatives of pyrrolo- and indoloquinolines allow functional group diversification on the quinoline nucleus, which proves to be highly advantageous for structural and biological activity assessments.     

Synthese radicalaire d'analgesiques potentiels: aryl-4 piperidines substituees en 2 et benzomorphanes

The synthesis of a series of 3-aryl 5-hexenyl amines and the cyclisations of the corresponding N-chloroamines are described. When the ring closure results from the amino radical addition to the ethylenic double bond, 2-chloromethyl 4-phenyl piperidines are obtained. These compounds lead by intramolecular Friedel-Craft reaction to varied substituted 6,7-benzomorphanes. When the phenyl ring is substituted with a methoxyl group, the cyclisation proceeds via homolytic aromatic substitution and 4-allyl tetrahydroquinolines are formed.     

Influence of (2,3,4,5,6-pentamethyl/phenyl)phenyl scaffold: stereoelectronic control of the persistence of o-quinonoid reactive intermediates of photochromic chromenes

Regioisomeric photochromic chromenes 1Ch-6Ch substituted with the (2,3,4,5,6-pentamethyl/phenyl)phenyl scaffold were designed to delve into stereoelectronic effects on the spectrokinetic properties of photogenerated o-quinonoid reactive intermediates. While the latter derived from 1Ch, 2Ch, 4Ch, and 5Ch were found to exhibit notable persistence, those from 3Ch and 6Ch were found to revert rapidly at room temperature to preclude visible coloration. The intermediates of 1Ch and 2Ch were found to be marginally more stable than those of 4Ch and 5Ch, respectively, attesting to the possibility of toroidal conjugation via C(ipso)-π orbitals in the former. The rapid reversion of the intermediates of 3Ch and 6Ch is attributed to unfavorable electronic repulsion between the phenyl ring of the (pentamethyl/phenyl)phenyl scaffold and one of the lone-pairs of the o-quinonoid oxygen. Thus, the regioisomerically substituted photochromic chromenes are shown to permit control of the reversion, very rapidly as well as slowly, of the colored o-quinonoid intermediates through operation of stereoelectronic effects differently.     

cis‐6‐Phenyl‐4bH,6H,11H,13H‐isoindolo[1,2‐c]benz[2,4]oxazepin‐13‐one

The title compound, C₂₂H₁₇NO₂, contains an isoindolinone moiety joined to a phenyl‐substituted benzoxazepine ring. The isoindolinone moiety is essentially planar and the oxazepine ring adopts a distorted chair conformation, with the phenyl substituent equatorial. Owing to the severe puckering of the central oxazepine ring, the mol­ecule as a whole is non‐planar; the benzene ring of the benzoxazepine fragment makes an angle of 67.7 (1)° with respect to the isoindoline ring.     

Influence of substituents on the through-space shielding of aromatic rings

A series of naphthalene derivatives, bearing a methyl group and a substituted phenyl ring in a 1,8-relationship, have been synthesized. The chemical shifts of the protons of the methyl group, which are pointed toward the shielding zone of the phenyl ring, were monitored as the phenyl substituents were varied. This work indicates that the shielding effect of the phenyl ring is not so severely altered by the substituents as to significantly influence the chemical shift of the methyl group. Nonetheless, within the small changes observed experimentally, there appears to be a tendency for electron-withdrawing X to shift the methyl signal downfield, whereas electron-donating X-groups cause a more upfield shift. Polarization and field effects are discussed as possible causes for this phenomenon. Chemical shifts computed for selected members of the series, using the recently published procedures of Rablen and Bally, are in agreement with the experimentally observed trends.     

Theoretical simulations of the tip-induced configuration changes of the 4,4(')-diacetyl-p-terphenyl molecule chemisorbed on Si(001)

We have investigated from a theoretical point of view modifications of the 4,4(')-diacetyl-p-terphenyl molecule chemisorbed on Si(001) induced by the scanning tunneling microscope (STM). In previous experiments, these modifications were observed to occur preferentially at the end of the molecule after a +4.0 V voltage pulse and at the center after a +4.5 V voltage pulse. In the framework of ab initio simulations, we have realized a systematic energetic study of the dissociative chemisorption of one, two, or three phenyl rings of the substituted p-terphenyl molecule. Charge densities were then calculated for the investigated configurations and compared to the STM topographies. Before manipulation with the STM tip, the substituted p-terphenyl molecule is preferentially adsorbed without phenyl ring dissociation, allowing a partial rotation of the central phenyl ring. Our results show that the STM induced modifications observed at the end of the molecule might originate from the dissociation of two phenyl rings (one central and one external ring), while the modifications occurring at the central part of the molecule can be interpreted as a dissociation of the two external rings.     

Infrared and Raman spectra of 3,5-diamino-6-(o-C6H4X)-1,2,4-triazines [X = F,Cl, Br,CH3

Raman and infrared spectra of four substituted 3,5-diamino-6-(ortho-substituted phenyl)-1,2,4-triazines, having ortho-fluoro, -chloro, -bromo and -methyl groups on the phenyl ring, are reported and discussed. Bands due to substituent sensitive phenyl vibrations are observed in both the Raman and infrared spectra. The Raman spectra of all four compounds have strong bands near 770 and 1330 cm(-1) which are assigned to the ring breathing vibration of the 1,2,4-triazine ring and an asymmetric triazine C-NH2 stretching vibration, respectively. A medium/strong band near 800 cm(-1) in the infrared spectra is attributed to an out-of-plane bending vibration of the substituted 1,2,4-triazine ring.     

Polylithiumorganic compounds. Part 29: C,C Bond cleavage of phenyl substituted and strained carbocycles using lithium metal

The reaction of phenyl substituted cyclopropanes phenylcyclopropane and 1,1-diphenylcyclopropane, phenyl substituted bicyclobutanes 1-phenylbicyclobutane, 1-methyl-3-phenylbicyclobutane, 1-methyl-2,2-diphenylbicyclobutane, as well as phenyl substituted spiropentanes phenylspiropentane and 1,1-diphenylspiropentane with lithium metal or lithium di-t-butylbiphenyl (LiDBB) was investigated. Under suitable reaction conditions and choice of solvent in all cases cleavage of the single bond next to the activating phenyl group was observed. The dilithiumorganic compounds thus obtained are sufficiently stable and can be trapped with electrophiles. Lithium hydride elimination is observed as follow-up reaction only in a few cases. The corresponding anions of the strained ring systems 1-lithio-2,2-diphenylcyclopropane, 1-lithio-3-phenylbicyclobutane, 1-lithio-3-methyl-2,2-diphenylbicyclobutane, and 1-lithio-4-phenylspiropentane, which can be obtained by lithium bromine exchange or by metalation of the unsubstituted carbocycle, do not show any cleavage upon reaction with lithium metal.     

Enantioseparation of 2‐(substituted phenyl)propanoic acids by high‐speed countercurrent chromatography and investigation of the influence of substituents in enantiorecognition

This paper concentrates on the enantioseparation of racemic 2‐(substituted phenyl)propanoic acids by high‐speed countercurrent chromatography with substituted β‐cyclodextrin as the chiral selector, and an investigation of the influence of the substituent on the benzene ring in enantiorecognition between the chiral selector and enantiomer of each racemate is presented. This is an extension research of our previous work on the enantioseparation of 2‐phenyl propanoic acid derivatives, to investigate the relationship between the value of enantioseparation factor and the different substituent on the benzene ring. In total, ten racemic 2‐(substituted phenyl)propanoic acids were investigated, of which four including 2‐(4‐nitrophenyl)propanoic acid, 2‐(4‐methylphenyl)propanoic acid, 2‐(4‐hydroxyphenyl)propanoic acid, and 2‐(4‐chlorophenyl)propanoic acid, were studied by countercurrent chromatography for the first time, and two racemates were successfully enantioseparated. The distribution ratio and enantioseparation factor for all the ten racemates were determined by enantioselective liquid–liquid extraction. The results showed that an electron‐donating group on the benzene ring presents a higher enantiorecognition induced by chiral selector than that of racemates with an electron‐withdrawing group on the benzene ring.     

Substituent effects on exchange coupling: 5-Aryl-substituted semiquinones and their complexes with MnII and CuII

A series of functionalized radical anion semiquinone (SQ-Ar) ligands and their MnII- and CuIIhydro-tris(3-cumenyl-5-methylpyrazolyl)borate (TpCum,MeMII) complexes were prepared and characterized. The semiquinone ligands have substituted phenyl rings (Ar = -C6H5NO2, -C6H5OMe, -C6H5-tert-Bu, etc.) attached to the SQ 5-position. Despite the "remoteness" of the phenyl ring substituents, the MII-SQ exchange parameters, J, were found to vary nearly 3-fold. Attempts to quantify the substituent effects on J are complicated by the fact that not all complexes could be structurally characterized. As such, substituent effects and phenyl-ring torsion angles could conspire to produce the observed variation in J values. Although there is no clear trend in the J values as a function of SQ substituent for the MnII complexes, for the CuII complexes, electron-withdrawing substituents on the phenyl ring have greater ferromagnetic J values than the CuII complexes of SQ ligands with electron-donating substituents. This trend suggests a FM contribution from MLCT excited states in the copper complexes.     

Substituent effects on the stereochemical outcome of the baker’s yeast-mediated biotransformation of α-hydroxy- and α-acetoxymethyl-5-phenylfuran-2-yl-ethanones

In this Letter the baker’s yeast-mediated biotransformation of variously substituted α-hydroxy- and α-acetoxymethyl-5-phenylfuran-2-yl-ethanones is described. The stereochemical outcome of the reactions was strongly influenced by the nature of the substituents on the phenyl ring.     

N-[1-(取代苯基)乙基]-2-羟基苯甲酰肼的合成、表征及抑菌活性

依据邻羟基二苯醚及芳香肼类化合物的抗菌特性, 以邻羟苯基为分子核心, 酰肼键为桥基, 设计合成了7种未见报道的N-(取代苯基)乙基-2-羟基苯甲酰肼类化合物. 以水杨酸甲酯为原料, 经肼解反应后与取代苯乙酮缩合, 再与硼氢化钠反应制得目标化合物, 化合物结构经IR, ¹H NMR和元素分析等证实. 抗菌活性测试结果表明, 该类化合物对不同菌株的抑菌活性具有明显的选择性和特异性. 当质量浓度为1×10^-4 g/mL时, 化合物3b和3e对大肠杆菌和白色念珠菌的抑菌率高达100%, 有极强的抑菌活性; 所有化合物对金黄色葡萄球菌的抑菌率均大于70%, 有一定的抑菌活性. 构效关系分析结果表明, 苯基中引入Cl或Br等卤原子能显著增强化合物的抑菌活性, 而引入-NO₂及-CH₃基团则会降低其抑菌活性.     

Modular Synthesis of Phenanthro[9,10‐c]thiophenes by a Sequence of CH Activation,Suzuki Cross‐Coupling and Photocyclization Reactions

A total number of 15 different 3,4‐diarylthiophenes were synthesized, which bear a chlorine atom in ortho‐position of one of the aryl substituents. One aryl group was introduced by an oxidative cross‐coupling reaction, involving a C?H activation at C4(3) of the thiophene core. The other aryl group was in most cases introduced by a Suzuki cross‐coupling reaction, which succeeded the oxidative cross‐coupling step. Photocyclization reactions of the 3,4‐diarylthiophenes were performed in a solvent mixture of benzene and acetonitrile (50:50 v/v) at λ=254 nm and proceeded to the title compounds in yields of 60–82 %. The selectivity of the photocyclization was determined at the ortho‐chloro‐substituted aryl ring by the position of the chlorine substituent. At the other ring, a single regioisomer was observed for phenyl and para‐substituted phenyl groups. For 2‐naphthyl and ortho‐substituted phenyl rings a clear preference was observed in favor of a major regioisomer, while meta‐substitution in the phenyl ring led to a about 1:1 mixture of 5‐ and 7‐substituted phenanthro[9,10‐c]thiophenes. Mechanistically, the photocyclization is likely to occur as a photochemically allowed, conrotatory [(4n+2)π] process accompanied by elimination of HCl. It was shown for two phenanthro[9,10‐c]thiophene products that they can be readily brominated in positions C1 and C3 (74–77 %), which in turn allows for further functionalization at these positions, for example, in the course of halogen–metal exchange and polymerization reactions.     

4,5‐Di­hydro‐3‐methyl‐5‐(4‐methyl­phenyl)‐1H‐pyrazole‐1‐carbox­amide

The reaction between 4‐(4‐methyl­phenyl)­but‐3‐en‐2‐one and amino­guanidine produced an unexpected product of formula C₁₂H₁₅N₃O, consisting of a carbox­amide moiety joined to a substituted pyrazoline ring at one of the N atoms. The pyrazoline ring adopts a flat‐envelope conformation and the substituted phenyl ring is oriented almost perpendicular to the heterocycle. The carbonyl O atom has partial anionic character as a result of the transfer of π density from the two adjacent sp² N atoms and is involved in an intermolecular hydrogen bond with the amide group.     

Dissociative protonation and proton transfers: fragmentation of alpha, beta-unsaturated aromatic ketones in mass spectrometry

In mass spectrometry of the alpha,beta-unsaturated aromatic ketones, Ph-CO-CH=CH-Ph', losses of a benzene from the two ends and elimination of a styrene are the three major fragmentation reactions of the protonated molecules. When the ketones are substituted on the right phenyl ring, the electron-donating groups are in favor of losing a styrene to form the benzoyl cation, PhCO(+), whereas the electron-withdrawing groups strongly favor loss of benzene of the left side to form a cinnamoyl cation, Ph'CH=CHCO(+). When the ketones are substituted on the left phenyl ring, the substituent effects on the reactions are reversed. In both cases, the ratios of the two competitive product ions are well-correlated with the sigma p(+) substituent constants. Theoretical calculations indicate that the carbonyl oxygen is the most favorable site for protonation, and the olefinic carbon adjacent to the carbonyl is also favorable especially when a strong electron-releasing group is present on the right phenyl ring. The energy barrier to the interconversion between the ions formed from protonation at these two sites regulates the overall reactions. Transfer of a proton from the carbonyl oxygen to the ipso position on either phenyl ring, which is dissociative, triggers loss of benzene.     

Effets de substituants et conformation de stilbenes

Simultaneous study of para nitrostilbenes by X-ray diffraction and ¹³C nuclear magnetic resonance shows a quantitative relationship between the effect of a para nitro substituent on the chemical shift of ethylenic carbon not adjacent to the substituted phenyl ring and the dihedral angle between this phenyl ring and the central double bond. The alternative introduction of substituents in each phenyl ring discloses at the position of carbon β a certain π-polarization which extends to the double bond and to an unsaturated group carried by carbon α.