P-substituted Phenyl Groups Research Articles

Panchromatic Photosensitizers Based on Push-Pull, Unsymmetrically Substituted Porphyrazines.

A series of five push-pull porphyrazines of A3 B type, in which unit B is an isoindole 4-carboxylic acid, has been prepared. The units A have been endowed with thioether, amine, ether and alkyl functions, either directly attached to the β-position of the pyrrolic units, or connected to the porphyrazine core through p-substituted phenyl groups. Attaching the electron-donor functions to the porphyrazine periphery produces strong perturbations in the electronic and redox properties of the dyes. Their HOMO and LUMO energies, estimated from the optical and redox data, as well as with DFT calculations, raise upon functionalization with amines, while the corresponding frontier orbital energetic levels lower upon functionalization with thioethers, p-methoxyphenyl or p-tert-butylphenyl groups. The effective interaction of peripheral substitution with the macrocycle produces chromophores with panchromatic absorption between 300 and 750-850 nm.

Synthesis and Metalation of Doubly o-Phenylene-Bridged Cyclic Bis(dipyrrin)s with Highly Bent Skeleton of Dibenzoporphyrin(2.1.2.1).

Facile synthesis of dibenzoporphyrins(2.1.2.1) has been successfully reported by the simple condensation reaction of o-dipyrrolylbenzene with various aldehydes in the presence of a Lewis acid. This reaction enables the preparation of various dibenzoporphyrin(2.1.2.1) derivatives with p-substituted phenyl groups, five-membered heterocycles, and ethynyl groups at the meso-positions. Dibenzoporphyrins(2.1.2.1) consist of two dipyrrin units that are connected by o-phenylene bridges, which adopt highly bent saddle-shaped structures; this was confirmed by X-ray diffraction analysis. We found that dibenzoporphyrin(2.1.2.1) can be described as a 20π antiaromatic conjugated system, but practically, it is not an antiaromatic macrocycle, which we revealed by (1) H NMR spectroscopy. The redox potentials had good correlations with Hammett substituent constant (σp ) of the substituents at the meso-positions. The free-base dibenzoporphyrin(2.1.2.1) was able to form the metal complexes with nickel(II), copper(II), palladium(II), platinum(II), and tin(IV) ions. These results suggested that dibenzoporphyrin(2.1.2.1) derivatives can be utilized as novel macrocyclic dianionic tetradentate ligands for various metal ions to give complexes with varying optical and electrochemical properties.

Synthesis and biological evaluation of new imidazo[2,1-b][1,3,4]thiadiazole-benzimidazole derivatives

In this report, we describe the synthesis and biological evaluation of a new series of 2-(imidazo[2,1-b][1,3,4]thiadiazol-5-yl)-1H-benzimidazole derivatives (5a-ac). The molecules were analyzed by 1H NMR, 13C NMR, mass spectral and elemental data. The structure of one of the pre-final compounds, 6-(4-methoxyphenyl)-2-(4-methylphenyl)imidazo[2,1-b][1,3,4]thiadiazole-5-carbaldehyde (4d) and that of a target compound, 2-[2-methyl-6-(4-methyl phenyl) imidazo[2,1-b][1,3,4]thiadiazol-5-yl]-1H-benzimidazole (5aa) were confirmed by single crystal XRD studies. All the target compounds were screened for in vitro anti-tuberculosis activity against Mycobacterium tuberculosis H37Rv strain. Seven (5c, 5d, 5l, 5p, 5r, 5z and 5aa) out of twenty nine compounds showed potent anti-tubercular activity with a MIC of 3.125 μg/mL. A p-substituted phenyl group (p-tolyl or p-chlorophenyl) in the imidazo[2,1-b][1,3,4]thiadiazole ring and/or a chloro group in the benzimidazole ring enhance anti-tuberculosis activity whereas a nitro group in the benzimidazole ring reduces the activity. In the antibacterial screening, compounds 5i, 5w and 5ac showed promising activity against the tested bacterial strains. Further, antifungal and antioxidant activities of these molecules were also investigated. In the cytotoxicity study, the active antitubercular compounds exhibited very low toxicity against a normal cell line.

Green Synthesis : Crystal Structure and Bioactivity of C-(Psubstituted Phenyl) Calix[4] Resorcinarenes-Dmso Inclusion Complexes

Green synthesis of calix[4]resorcinarene hosts with p-substituted phenyl group at their methine carbons was achieved. Fluorine, chlorine and bromine atoms, as well as methoxy group, were selected as substituents at the para position of the benzaldehyde which was condensed with resorcinol in presence of solid p-toluenesulfonic acid. The solid state structures of the newly prepared C-(p-fluorophenyl)calix[4]resorcinarene-DMSO and C-(p-chlorophenyl)calix[4]resorcinarene-DMSO inclusion complexes were determined by single-crystal X-ray diffraction and found to form different structural conformations; chair (C2h) and boat (C2v), respectively. In addition, both crystal structures adopted several intermolecular noncovalent supramolecular interactions which were carefully investigated and presented in terms of crystal engineering and supramolecular chemistry. The synthesized C-(p-substitutedphenyl)calix[4]resorcinarene hosts inhibited the growth of Gram-positive bacteria with the C-(p-bromophenyl)calix[4]resorcinarene derivative being the most potent agent (MIC=15.6-125 μg/ml).

Systematic Synthesis and Characterization of a Series of Tetra(5-aryl-2-thienyl)thiophenes

Abstract We have succeeded in the synthesis of a series of tetra(5-aryl-2-thienyl)thiophenes as aryl-functionalized tetrathienylthiophenes. Characterization of these chemicals was performed by physical and spectroscopic means. The electrochemical properties were examined by cyclic voltammetry. The CV of all compounds showed that the redox behavior and potentials were controlled by the electronic effect of the p-substituted phenyl groups introduced at the outer α-positions on the four thiophene units linked to the thiophene core.

Mechanofluorochromism of heteropolycyclic donor–π-acceptor type fluorescent dyes

This paper reports that mechanofluorochromism is found for a series of benzofuro[2,3-c]oxazolo[4,5-a]carbazole-type fluorophores (1a–5a) with different p-substituted phenyl groups as acceptor and dibutylamino groups as donor. Grinding of as-recrystallized dyes 1a–3a with strong electron-accepting group induces a fluorescent color change with an enhanced quantum yield and the fluorescent color is recovered by heating or exposure to solvent vapor. On the basis of experimental results and semi-empirical molecular orbital calculations (AM1 and INDO/S), we clarified that the mechanofluorochromism is attributed to a reversible switching between crystalline and amorphous states with changes of dipole–dipole interaction and intermolecular π–π interaction by changes of the densities of the solids before and after grinding.

Push–pull structures with a pyrazine core and hexatriene chain: synthesis and light-emitting properties

In this paper, we describe the synthesis of various push–pull molecules with a central pyrazine unit connected to a hexatriene chain terminated by various p-substituted phenyl groups. The key steps involve metallation and subsequent transmetallation of 2-chloro and 2,6-dichloropyrazine followed by a Negishi cross-coupling reaction of the intermediate organozinc derivative with (2 E,4 E)-5-bromopentadienal. The aldehydes are then submitted to a Wittig reaction with the appropriate phosphonium salts readily obtained from various substituted benzyl alcohols. The light-emitting properties of the so obtained molecules are then investigated in terms of absorption and emission spectra and non-linear optics experiments have been carried out in two cases.

Toward π-Conjugated Molecule Bundles: Synthesis of a Series of B,B‘,B‘‘-Trianthryl-N,N‘,N‘‘-triarylborazines and the Bundle Effects on Their Properties

As a prototype of a pi-conjugated molecule bundled system, a series of B,B',B''-trianthryl- N,N',N''-triarylborazine derivatives bearing various p-substituted phenyl groups (p-R-C(6)H(4): R = hexyl (1), i-Pr (2), CF(3) (3), Br (5)) as aryl groups was designed and synthesized. The crystal structure analysis of these derivatives confirmed that the three anthryl and three phenyl groups are bundled up alternately in a C(3) symmetrical gear-shaped fashion. On the basis of this structure, the trianthrylborazine derivatives form a unique honeycomblike packing structure consisting of intermolecular pi-stacking of the anthryl moieties. Significant bundle effects were observed in the photophysical and electrochemical properties of these compounds. In their fluorescence spectra, the trianthrylborazine derivatives (1-3) show intense emissions around 390 nm, whose quantum yields (1, Phi(F) = 0.62; 2, Phi(F) = 0.59; 3, Phi(F) = 0.63) are about twice high as that of anthracene (Phi(F) = 0.27). The cyclic voltammetry measurements show that the oxidation peak potential can be tuned by varying the substituents on the phenyl moieties. Theoretical calculations (B3LYP/ 6-31G(d)) suggested that secondary through-bond/through-space interactions in the bundled structure play an important role in the tuning of these properties. Facile structural derivatization at the 10-position of the anthryl moieties of trianthrylborazine was conducted to demonstrate the utility of the borazine skeleton as a core framework for new organic electronic materials.

SELECTIVE PREPARATION OF OXACYCLIC AND LINEAR PHOSPHONATES AND THE EFFECT OF DIETHYL PHOSPHONATE GROUP ON SPECTROSCOPIC DETERMINATION OF THE STRUCTURES

The formation of either oxacyclic or linear phosphonates by alternating the synthetic condition of a single method is described. Structural identification of these two isomeric oxacyclic and linear phosphonates, 2 and 3, were performed with IR, MS, 1H & 13C NMR. The 1H & 13C NMR spectroscopic data (ie., the chemical shifts and coupling constants) showed that the phosphonate group was the dominant factor in the conformation of oxacyclic phosphonate, with little effect from the phenyl and p-substituted phenyl groups. The phosphonate group with two ethoxy groups hovered over the THF-ring, thus presenting a complex 1H & 13C NMR spectra. The results indicated that the phenyl group stretched out and away from the THF-ring, thus exerting little electronic influence on the oxacyclic ring. For linear phosphonate 3, McLafferty rearrangements with both C = O and P = O groups were observed in mass fragmentations. Spectroscopic data provided the information for identification of these phosphonates.

Determination of reactivity constants of 5-substituted 2-indolyl groups by means of13C NMR

1. 13C chemical shifts have been measured for 3-substituted biphenyls in acetone. 2. On the basis of correlation equations for the benzene ring, the σI and σR∘ constants have been determined for m- and p-substituted phenyl groups. 3. Relationships have been found that can be used to estimate the σ-constants of any m- or p-substituted phenyl group, using known constants of the substituent X.

Dehydroannulenes. IX. Effects of Substituents on the 1H NMR Spectra of Tetrakisdehydro[18]- and Bisdehydro[14]annulenes

Abstract In order to obtain information on the cause of low field shift of 1H NMR signals of ‘acetylene-cumulene’-dehydroannulenes on introduction of substituents, the syntheses of 1,8-bisdehydro[14]- and 6,8,15,17-tetrakisdehydro[18]annulenes bearing p-substituted phenyl group(s) have been performed. The examination of their 1H NMR spectra indicates that the low field shift of NMR signals can be regarded as a superposition of three effects, i.e., 1) decrease of ring current in annulene nucleus by perturbation of substituent group(s), 2) Deshielding effect of ring current in aryl substituent(s) exerted on annulene protons, and 3) Electronic effect of p-substituent in phenyl group(s) transmitted to annulene ring.

Polar Substituent Constants for Substituted Phenyl Groups. The Extended Taft Equation.

Abstract Values of the σ* constants have been defined for some m- and p-substituted phenyl groups from the 29Si–H coupling constants for a series of m- and p-substituted phenylsilanes, phenylmethylsilanes, and phenyldimethylsilanes. The σ* constants for the groups, XC6H4, were found to be directly related to the Hammett σ constants for the ring substituents, X. From this correlation the σ* constants for a number of other substituted phenyl groups have also been calculated. Examples have been presented in which a simple relationship holds between the Taft polar substituent constants including the newly derived σ* constants and molecular properties for a series of compounds covering both aliphatic and aromatic substances. Correlations of reactivities with the extended σ* values have been illustrated and the implications of the results are discussed.

Pyrimidine reactions. XX. Thermal rearrangement of 5-(p-substituted phenyl)-2(and 4)-methoxypyrimidines.

2(and 4)-Methoxy-5-phenylpyrimidine and some p-substituted derivatives are rearranged by heating in triethylamine to give the corresponding N-methyl-2(or 4)-oxopyrimidines. The log k1 values for rearrangement of the 2-methoxypyrimidines show a rectilinear relationship to the known σ values for p-substituted phenyl groups, save when such values are highly negative. 4-Methoxy-5-phenylpyrimidine and its p-nitro-derivative rearrange more rapidly than their respective 2-methoxy-isomers; in addition, each gives a mixture of N-1 and N-3 methylated products in which the latter predominates. These facts are consistent with the recently proposed intermolecular and ionic nature of such rearrangements. Some of the intermediate 2-hydroxy-5-phenylpyrimidines and their N-methyl derivatives are made by a novel modification of the principal pyrimidine synthesis, namely condensation of urea or N-methylurea with 3-imino-2-phenylpropionaldehyde or a derivative. 1H N.m.r. and u.v. spectra are used to follow rearrangements and to confirm structures.

The relative migration tendencies of p-substituted phenyl groups in carbonium ion doubly-degenerate rearrangements

The order of the migration tendencies of p-X-phenyl groups in the doubly-degenerate rearrangement of stable 9-p-X-phenyl-9,10-dimethylphenanthrenonium ions (Ia—e) is X = Me > F ∼ H > Cl > CF3.

Synthesis of p-alkylphenylacetic acids

The preparation of fatty acids is described where the β-carbon atom has been replaced by a p-substituted phenyl group. Friedel-Crafts acylation of phenylacetic esters gives mixtures consisting chiefly of m- and p-acylphenylacetates.

Isomerisations akin to the Dimroth rearrangement. Part II. The equilibria of 4-mercapto-1,2,3,5,7-penta-azaindenes with 4-amino-1-thia-2,3,5,7-tetra-azaindenes

When 1-benzyl-4-mercapto-1,2,3,5,7-penta-azaindene or 4-benzylamino-1-thia-2,3,5,7-tetra-azaindene is boiled in an alcohol or maintained in the molten state, the equilibrium mixture consists largely of the thia-isomer. Analogues in which the benzyl group is replaced by a phenyl or p-substituted phenyl group behave similarly. For each pair of isomers, the first-order rate constant for equilibration in butanol–methoxyethanol, and the equilibrium constant are recorded. The plot, log forward component of the rate constant versus Hammett's sigma value for the p-substituent, is rectilinear. Equilibrium constants also vary with the substituents and with temperature: the thiaisomer is more strongly favoured by electron withdrawal and by higher temperatures. In dimethyl sulphoxide solution equilibrium lies about midway; in aqueous sodium hydroxide, the penta-azaindene (anion) is favoured. Each compound was prepared by a direct route as well as by isomerisation.

Syntheses of 1-phenyl-2-thiobarbituric acid derivatives and their analgesic activity

5-Alkylamino-2-thiobarbituric acid derivatives containing a p-substituted phenyl group in the nitrogen were synthesized in order to examine the presence of analgesic action in a compound by the introduction of two kinds of atom group, one having a pyrolytic and the other hypnotic activity, in one molecule. Attempt for further introduction of an alkyl group in the carbon atom at 5-position failed. Pharmacological test of 19 kinds of the barbituric acid derivatives synthesized showed that none of them had a strong analgesic action.