Ali A. Khalaf

New polymer syntheses. IX. Synthesis and properties of new conducting polyazomethine polymers containing main chain cycloalkanone and pyridine moieties

Novel polyazomethines containing cycloalkanones or pyridine moieties were synthesized by the polycondensation of 2,5-bis(m-aminobenzylidene)cyclopentanone (BMAP, IV), 2,6-bis(m-aminobenzylidene)cyclohexanone (BMAH, V), 2,6-bis(p-aminobenzylidene)cyclohexanone (BPAH, VI), and 2,6-bis(m-aminostyryl)pyridine (BMAS, VIII) diamines with terephthalaldehyde in EtOH at 25°C. These polymers were yellow to orange in color, had reduced viscosities up to 1.42 dL/g, and had electric conductivities as high as 10 -11 -10 -12 S cm -1 . All the polyazomethines were insoluble in common organic solvents but dissolved completely in concentrated sulfuric acid. However, they were readily hydrolyzed in concentrated H 2 SO 4 . X-ray diffraction diagrams showed that the crystallinities of the polyazomethines were low. These azomethine polymers showed high thermal and thermooxidative stability and exhibited no appreciable decomposition up to 400°C in air. The electronic spectra of the polymers indicated a large bathochromic shift of the π-π * absorption band (∼360 nm) that was due to the presence of C=N bonds in the polymer main chain. Doping with iodine dramatically raised the conductivity and produced dark brown to black colored semiconductive polymers with a maximum conductivity on the order of 10 -7 S cm -1 . Furthermore, the morphology of selected examples of the four polyazomethines was examined by scanning electron microscopy.

Liquid crystalline polymers VII. Thermotropic liquid crystalline poly(azomethine-ether)s containing dibenzylidene derivatives in the main chain

Abstract A new homologous series of thermotropic liquid crystalline poly(azomethine-ether)s based on dibenzylidene derivatives was synthesized by solution polycondensation of various diformyl-α,ω-diphenoxyalkanes, I–VIII with 2,7-bis-(m-aminobenzylidene)cycloheptanone IX and bis-(m-aminobenzylidene)acetone X. The inherent viscosities of the polymers were in the range 0.23–0.69 dl/g. All the poly(azomethine-ether)s were insoluble in common organic solvents but dissolved completely in concentrated H2SO4 and methanesulphonic acid. The mesomorphic properties were studied as a function of the diphenoxyalkane space length. Analysis by differential scanning calorimetry and optical polarized microscopy demonstrated that the poly(azomethine-ether)s from nematic mesophases over wide temperature ranges.

New polymer syntheses XII. Polyketones based on diarylidenecycloalkanones

Abstract Two new series of polyketones containing diarylidene links was synthesized by the Friedel–Crafts polymerization of diarylidenecyclopentanone or diarylidenecyclohexanone with aromatic diacid chlorides, azodibenzoyl chlorides, or aliphatic diacid chlorides. The resulting polymers had inherent viscosities in the range 0.76–1.18 dl/g and showed poor solubilities to common organic solvents excepts strong acids. The thermal stabilities of these polymers were evaluated and correlated to their structural units by thermogravimetric analysis (TGA), DTG and DSC measurements. The TGA data revealed 10% weight losses at 190–300 °C. Moreover, the crystallinity of some polymers were tested by X-ray analyses and the UV–visible spectra showed characteristic absorption bands in the range 240–350 nm.

NEW POLYMER SYNTHESES. XIII. SYNTHESIS AND CHARACTERIZATION OF NOVEL POLYKETONES VIA FRIEDEL-CRAFTS REACTION AND BASED ON DIARYLIDENE DERIVATIVES

ABSTRACT An interesting new class of polyketones based on diarylidene derivatives were synthesized by Friedel-Crafts reaction of 2,7-dibenzylidenecycloheptanone (I) and dibenzylideneacetone (II) monomers, with different diacid chlorids including: isophthalic, terephthalic, 3,3′-azodibenzoic, 4,4′-azodibenzoic, biphenic, adipic, sebacic and oxalic diacids in dry dichloromethane solvent and AlCl3 catalyst. The model compounds were synthesized by reacting I and II with benzoyl chloride and characterized by 1H-NMR, IR and elemental analyses. The polyketones were insoluble in most organic solvents but dissolved easily in concentrated sulfuric acid. The thermal properties of these polymers were evaluated and correlated to their structural units by TGA, DTG measurements and had inherent viscosity up to 0.36–0.84 dI/g. The crystallinity of some polymers were tested by X-ray analysis. The electronic spectra of selected examples were measured in DMSO solution and the morphological properties were detected by SEM.

Modern Friedel-Crafts chemistry. XI: Cyclization of aryl haloalkyl sulfones, arylsulfonylacyl chlorides and their corresponding sulfides

Abstract The sulfone group deactivation for cyclialkylation and cycliacylation reactions in the presence of Friedel-Crafts catalysts was demonstrated in a number of aryl chlorlalkylsulfones (1–8) and arylsulfonylacyl chlorides (17a-22a), respectively. As expected, the corresponding arylchloralkyl sulfides (9–16) and arylmercaptoacyl chlorides (13a-28a) underwent ring-closure reaction in most cases under the same conditions. The ease of cyclization was governed by the ring size, the stability of the attacking carbocation and the nucleophilicity of the aryl moiety. Also the behaviour of benzyl sulfones (29, 31a, and 32a) and sulfides (33, and 36a) was inconsistent. Noteworthy, the Friedel-Crafts cyclization reaction is thus considered an accessible method for the synthesis of compound 37–41 and 45,51.

Friedel–Crafts Chemistry. Part 39. Unprecedented Facile Route to the Synthesis of Benzo[b][1]benzazepines via Intramolecular Friedel–Crafts Cyclialkylations

A series of six pharmaceutically promising 5,6-dihydro-11H-benzo[b][1]benzazepine derivatives (1c–h) were cleanly prepared by Friedel–Crafts cyclialkylations of nitrogen-containing alkanols in the presence of AlCl3, 85 % H2SO4 or polyphosphoric acid catalysts. The precursor alkanols (13a–f) were readily prepared by reaction of two synthesized carboxylic acid esters (12a, b) with different Grignard reagents. Also, two dibenzo[b,f]azepinones (15a, b) were prepared by Friedel–Crafts cycliacylation and reduced to the corresponding 5,6-dihydro-11H-benzo[b][1]benzazepines (1a, b). Overall, this approach allows easy and efficient access to polytricyclic amines from easily synthesized alkanols or cycloketones. A plausible carbocation mechanism is proposed to account for the results.

Friedel–Crafts Chemistry. Part 46. Unprecedented Construction of Tricyclic Pyrazolo[3,4-b]quinolines, -[1,8]naphthyridines, -azepines, -azocines, -pyrido[3,2-g]azocines, and pyrazolo[3,4-b]azonines via Friedel–Crafts Ring Closures

A series of keto-substituted pyrazolo[3,4-b]quinolines, pyrazolo[3,4-b][1,8]naphthyridines, benzo[e]pyrazolo[3,4-b]azepines, benzo[g]pyrazolo[3,4-b]azocines, pyrazolo[3,4-b]pyrido[3,2-g]azocines, and benzo[g]pyrazolo[3,4-b]azonines scaffolds were synthesized via a Friedel–Crafts cyclialkylation approach. The precursor acids were obtained by utilizing the modified Ullman coupling reactions of 5-chloro-3-methyl-1-phenyl-1H-pyrazole-4-carboxylic acid with different aryl amines followed by ring closures in the presence of AlCl3/CH3NO2 or P2O5 or polyphosphoric acid catalysts. Particular attention is given to the novel structures especially in regard to the promising pharmaceutical and therapeutic values associated with their skeletons.

Modern Friedel-Crafts chemistry. XIV: On the cyclization of selected aryl hydroxyalkyl sulfides

Abstract The feasibility of cycloalkylation reactions in the presence of Friedel–Crafts catalysts was demonstrated in a number of aryl hydroxyalkyl sulfides (1–5), and benzyl hydroxyalkyl sulfides (6–7). Treatment of compounds (1–7) with Friedel-Crafts catalysts gave diaryl disulfides, diaryl sulfides, arene thiols, chlorohydrins, aryl chloroalkyl sulfides, aryl alkenyl sulfides and cyclization products. It is noteworthy to mention that cyclization products were isolated only in cases where the hydroxyl group is linked to a tertiary carbon atom as in compounds 3 and 7. A suitable reaction pathway is suggested to rationalize the formation of the various reaction products.

Friedel–Crafts Chemistry. Part 43. A Convergent Construction of Some New Bridged Aza-Bicyclic Analogues of Azocine, Azonine, and Azecine via Friedel–Crafts Ring Closures

Our present study provides an expedient general approach for the synthesis of some novel bridged dibenzo-azocinone, -azoninone, -azecinone, -azocine, -azonine, and -azecine derivatives via Friedel–Crafts intramolecular ring-closure reactions. The methodology is realized by a four-step protocol involving first preparation of 7-methyl-3,3-diphenylindoline through the reduction of 7-methyl-3,3-diphenylindolin-2-one followed by N-alkylations with different haloesters (α-, β- or γ-). The resulting indoline ester derivatives were allowed to react both by addition of Grignard reagents to afford alcohols and by hydrolysis to afford acids. Particular attention has been given to the novel structures especially in regard to the promising pharmaceutical and therapeutic values associated with their skeletons.

Modern Friedel-Crafts Chemistry. Part 38. Facile Synthesis of Acenaphthenes via Direct and Rearranged Intramolecular Friedel-Crafts Cyclialkylations of Intermediate Carbinols

A novel one-pot synthesis of six di-, tri-, and tetra-substituted acenaphthenes 18a-f via direct and/or rearranged Friedel-Crafts cyclialkylations of seven novel carbinols 1a-g is described. The methodology involves treatment of alkanols 1a-g in the presence of both Brønsted (PPA, H2SO4) and Lewis (AlCl3/CH3NO2) acid catalysts. The method offers several advantages such as high yields, high selectivities, and easily accessible starting materials. A plausible mechanism for this type of Friedel-Crafts cyclialkylation is proposed.