Aboel-Magd A. Abdel-Wahab

Photocatalytic oxidation of selected aryl alcohols in acetonitrile

Abstract Photocatalytic oxidation of selected aryl alcohols ( 1 – 7 ) has been carried out by using anatase titanium dioxide catalyst. The main oxidation products were the corresponding aldehydes or ketones and acids, in addition to unidentified minor compounds. Kinetic studies revealed a second-order reaction rate for benzyl alcohol, as a model alcohol, photocatalytic oxidation. The suggested mechanism envisages electron–hole pair formation on the catalyst surface followed by oxidation–reduction reactions.

TiO2-photocatalytic oxidation of selected heterocyclic sulfur compounds

Polynuclear-heterocyclic sulfides (I–IV) were oxidized dominantly to the corresponding sulfoxides and sulfones via TiO2-mediated photocatalytic oxidation in aerated acetonitrile. Also, methylene group in IV and V and active methene groups in VI have been readily oxidized to carbonyl one in a high yield under the same prevailing conditions. A plausible electron transfer mechanism, in which an electronhole pair is generated on the surface of TiO2 by illumination, is suggested for the semiconductor-mediated photocatalysis.

Synthesis of IR‐sensitive photoswitchable molecules: photochromic 9′‐ styrylquinolinedihydroindolizines

New mono- (5a–t, w) and biphotochromic (5u, v) 9′-styrylquinolinespirodihydroindolizines (DHIs) with IR-absorbing colored forms (4) were prepared. The conformation and configuration of these new DHIs were investigated by NMR studies and the structure was proved by x-ray analysis. The kinetics of the fast cyclizing process of betaine 4 to DHI 5 takes place in the millisecond range and were studied by flash photolysis. The absorption bands of the betaines 4 were recorded at low temperature by FT-UV/VIS/near-IR spectroscopy. Large solvent effects on the absorption maxima of betaines 4 were observed. Copyright

Steric substituent effects of new photochromic tetrahydroindolizines leading to tunable photophysical behavior of the colored betaines

Abstract Various substituted photochromic tetrahydroindolizine (THIs) derivatives 4a–r have been synthesized by nucleophilic addition of 1-phenyl-3,4-dihydroisoquinolines 2 to spirocyclopropene 1. After irradiation of the THIs 4a–r with UV light, a blue to green colored zwitterionic betaines 3a–r was formed which undergoes a thermal electrocyclization leading to colorless THIs 4a–r. Both the half-life of the thermal back reaction and the absorption spectra of the colored forms are found to be strongly dependent on the position and size of the substituent in the 10′b-phenyl ring. A strong pronounced effect was observed by comparison of each ortho-substituents to the corresponding para-substituents which showed increase in the half-life by a factor of 4 for o-, p-fluoro-substitution 3h–j and a factor of 2000 for o-, p-iodo-substitution 3q,r. Meta- and para-substitution showed no pronounced influence on the half-life. The steric effect of different groups was well proved by CHARMm calculation. The computational results provided a new insight into the reaction pathway signifying the steric effect of substituents on THIs 4. The energies of the unsubstituted THI 4a, the ortho-substituted THIs 4b,e,k and the meta-derivatives 4c,f,l as well as their betaines for the cisoid 3″ and transoid 3‴ were studied. The structures and energies for 3b,e,k,c,f,l were monitored. In conclusion, the formation of the twisted open form 3′ is responsible for value of the rate constant of the thermal cyclization.

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.

First intramolecular trapping and structural proof of the key intermediate in the formation of indolizine photochromics

The reaction of substituted spirocyclopropenes 1 with 1-(3,5-dinitrophenyl)-3,4-dihydroisoquinoline 2 in dry ether solution afforded not only the expected THI 4 by 1,5-electrocyclization but also novel fluorenespiroazanorcaradienes 5 which is the first intramolecularly trapped product of the key intermediate in the formation of indolizine photochromics.

NONCONVENTIONAL FRIEDEL-CRAFTS CHEMISTRY II. ON THE CATALYTIC ACTION OF TRIFLIC ACID AND ALUMINIUM CHLORIDE ON SELECTED ARYL THIOESTERS

Abstract The catalytic action of triflic acid and/or aluminium chloride on seven selected aryl thioesters (1-7) gave in all cases aryl thiols, diaryl sulfides, diaryl disulfide, and thianthrene derivatives in addition to the corresponding aryl carboxylic acids. Thioester 5 gave thiochromanone derivatives in good yield under the same conditions. Plausible mechanisms were suggested to rationalize the obtained results.

SYNTHESIS AND BIOLOGICAL ACTIVITIES OF NEW INDOLE DERIVATIVES CONTAINING SULFIDE AND/OR SULFONE MOIETIES. PART I

Abstract 4-Amino-halonitrodiphenyl sulfides(I) and/or 4-amino-halonitrodiphenyl sulfones have been found to react with isatin, N-acetyl isatin, isatin-N-Mannich bases, indole-3-carboxaldehyde and N-substituted indole-3-carboxaldehyde producing the corresponding indole derivatives. The biological activity of some of these products was screened against selected strains of bacteria.

TiO2 Nanoparticles-Photocatalytic Oxidation of Selected Cycloalkanols

Photocatalytic oxidation of cyclohexanol (1), cyclopentanol (2), and cycloheptanol (3) was investigated by using titanium dioxide (Degussa P25) as a semiconductor photocatalyst .The effect of different operational parameters such as the catalyst, the solvent, time, and oxidant was also studied. Results showed a high percentage of conversion for 1–3 (71.6%, 94.2%, and 100%, resp.) and that the primary photocatalytic oxidation products are the corresponding cycloalkanones (4–6). They were formed with high selectivity (>85%). Several other products were also identified using GC, GC/MS techniques and authentic samples. The photocatalytic activity is explained by a photoinduced electron transfer mechanism through the formation of electron-hole pair at the surface of the semiconductor particles. A first-order kinetic model was observed for the photocatalytic oxidation of the investigated cycloalkanols.

CYCLIZATION OF SELECTED BENZYL SULFONE DERIVATIVES UNDER PHASE TRANSFER CATALYTIC CONDITIONS

Abstract Seven selected benzyl chloroalkyl sulfones(1a-c) and benzyl carboethoxyalkyl sulfones (1d-q) has been subjected to treatment with aqueous NaOH (50%) under PTC conditions. Analysis of the product mixtures revealed competitive cyclization, elimination and hydrolysis reactions. Correlation of the reaction products and the starting sulfone has been discussed.