Gamal A. El-Hiti

Acetylation of aromatic ethers using acetic anhydride over solid acid catalysts in a solvent-free system. Scope of the reaction for substituted ethers

The acetylation of aryl ethers using acetic anhydride in the presence of zeolites under modest conditions in a solvent-free system gave the corresponding para-acetylated products in high yields. The zeolite can be recovered, regenerated and reused to give almost the same yield as that given when fresh zeolite is used.

Regioselective Control of Electrophilic Aromatic Substitution Reactions

para-Regioselective electrophilic aromatic substitution reactions, for example nitration, alkylation, acylation, sulfonylation and halogenation, can be achieved by carrying out reactions over solid catalysts such as zeolites, under modest conditions via shape-selectivity. By contrast, organolithium reagents can play an important role when ortho-products are desirable. ortho-Lithiation has been applied for the synthesis of more complex substituted heterocycles that are difficult to prepare by other means.

Synthesis, antimicrobial and anticancer activities of a novel series of diphenyl 1-(pyridin-3-yl)ethylphosphonates

A novel series of diphenyl 1-(arylamino)-1-(pyridin-3-yl)ethylphosphonates 1-5 was obtained in high yields from reactions of 3-acetyl pyridine with aromatic amines and triphenylphosphite in the presence of lithium perchlorate as a catalyst. The structures of the synthesized compounds were confirmed by IR, (1)H NMR spectral data and microanalyses. Compounds 1-5 showed high antimicrobial activities against Escherichia coli (NCIM2065) as a Gram-negative bacterium, Bacillus subtilis (PC1219) and Staphylococcus aureus (ATCC25292) as Gram-positive bacteria and Candidaalbicans and Saccharomyces cerevisiae as fungi, at low concentrations (10-100 μg/mL). Also, the synthesized compounds showed significant cytotoxicity anticancer activities against liver carcinoma cell line (HepG2) and human breast adenocarcinoma cell line (MCF7). The lethal dose of the synthesized compounds was also determined and indicated that most compounds are safe to use.

3-Acetylindoles: Synthesis, Reactions and Biological Activities

This review deals with synthesis and reactions of 3-acetylindoles as well as their biological activities. The data published over the last few years on the methods of synthesis and chemical properties of 3-acetylindoles are reviewed here for the first time. 3-Acetylindole derivatives have been in the centre of at- tention of researchers over many years due to the high prac- tical value of these compounds, in the first place, the unusu- ally broad spectrum of biological activities. For example, 4- (1H-indol-3-yl)-2-hydroxy-4-oxobut-2-enoic acid was useful as anti-HIV agent, other compounds derived from 3-acetylindoles used in the treatment of gastrointestinal, car- diovascular and CNS disorders, and also used as HIV-1 inte- grase inhibitors. Despite this importance, 3-acetylindoles have not been previously reviewed. The main purpose of this review is to present a survey of the literature on 3- acetylindoles chemistry and provides useful and up-to-date data for medicinal chemists.

Role of modern chemistry in sustainable arable crop protection

Organic chemistry has been, and for the foreseeable future will remain, vitally important for crop protection. Control of fungal pathogens, insect pests and weeds is crucial to enhanced food provision. As world population continues to grow, it is timely to assess the current situation, anticipate future challenges and consider how new chemistry may help meet those challenges. In future, agriculture will increasingly be expected to provide not only food and feed, but also crops for conversion into renewable fuels and chemical feedstocks. This will further increase the demand for higher crop yields per unit area, requiring chemicals used in crop production to be even more sophisticated. In order to contribute to programmes of integrated crop management, there is a requirement for chemicals to display high specificity, demonstrate benign environmental and toxicological profiles, and be biodegradable. It will also be necessary to improve production of those chemicals, because waste generated by the production process mitigates the overall benefit. Three aspects are considered in this review: advances in the discovery process for new molecules for sustainable crop protection, including tests for environmental and toxicological properties as well as biological activity; advances in synthetic chemistry that may offer efficient and environmentally benign manufacturing processes for modern crop protection chemicals; and issues related to energy use and production through agriculture.

Simultaneous quantification of multiple nucleic acid targets using chemiluminescent probes

A novel method is described for simultaneous detection and quantification of attomoles or a few femtomoles of two (or potentially more) nucleic acid targets, without need for amplification. The technique depends on spectral-temporal resolution of chemiluminescence emitted from independent hybridization-induced chemiluminescent signal probes. The probes are internally quenched except in the presence of their specific targets, thereby allowing detection limits up to 10,000 times lower than with fluorescent probes. This is sufficient to obviate the need for amplification in many cases. The utility of the technique has been demonstrated by use of resolvable N-linked acridinium and 2,7-dimethoxyacridinium ester labeled probes in a homogeneous assay for sensitive and simultaneous independent quantification of pan-bacterial and pan-fungal target sequences in seawater.

Use of zeolites for greener and more para-selective electrophilic aromatic substitution reactions

Electrophilic aromatic substitution is one of the most important reactions in synthetic organic chemistry. Such reactions are used for the synthesis of important intermediates that can be used as precursors for the production of pharmaceutical, agrochemical and industrial products. However, many commercial processes to produce such materials still rely on technology that was developed many years ago. Such processes commonly lead to mixtures of regioisomers and in recent years several new approaches have been developed to gain control over the regiochemistry of the reactions. Zeolites can act as heterogeneous catalysts, support reagents, entrain by-products, enhance product para-selectivities via shape-selectivity and avoid aqueous work-ups. For example, zeolites can have advantages in para-regioselective nitration, halogenation, alkylation, acylation and methanesulfonylation reactions under modest conditions. Moreover, usually they can be easily removed from reaction mixtures by simple filtration and regenerated by heating and can then be reused several times to give almost the same yield and selectivity as fresh samples. This review surveys the use of zeolites as para-selective catalysts for a whole range of aromatic substitution reactions, based largely on our own work in the area, but set in the wider context of other related work.

Synthesis of New Thiophene Derivatives and Their Use as Photostabilizers for Rigid Poly(vinyl chloride)

Five new thiophenes, namely, N-[(3-bromo-2-methylthiophen-5-yl)methylene]-4-methoxyaniline (4a), N-[(3-bromo-2-methylthiophen-5-yl)methylene]-3,4-dimethoxyaniline (4b), N-[(3-bromo-2-methylthiophen-5-yl)methylene]-3,4-dimethylaniline (4c), 3-[(3-bromo-2-methylthiophen-5-yl)methyleneamino]-2-methylquinazolin-4(3H)-one (4d), and 3-[(3-bromo-2-methylthiophen-5-yl)methyleneamino]-2-isopropylquinazolin-4(3H)-one (4e), have been synthesized. All of these materials brought about a reduction in the level of photodegradation of poly(vinyl chloride) (PVC) films containing the synthesized thiophenes (0.5%; by weight). The results obtained showed that the extent of photostabilization of PVC in the presence of an additive was in the order 4e > 4d > 4b > 4a > 4c. For the most favorable additive (4e), the rate of appearance of infrared absorption bands of degradation products was reduced by around two-thirds, while the quantum yield of chain scission was calculated to be reduced by a factor of more than one thousand. It is suggested that the additives may help stabilize PVC by direct absorption of UV radiation and dissipation of the energy as heat or that electrostatic attraction between the additives and PVC may assist transfer of energy from excited state PVC to the additive, from where it can be dissipated.

2-Acetylbenzofurans: synthesis, reactions and applications

This review deals with synthesis and reactions of 2-acetylbenzofurans. Some of these reactions have been applied successfully to the synthesis of biologically important compounds. The main purpose of this review is to present a survey of the literature on 2-acetylbenzofurans chemistry and provides useful and up-to-date data for their applications since such compounds have not been previ- ously reviewed.

New polymeric sulfide-borane complexes: convenient hydroborating and reducing reagents

New polymeric borane adducts have been synthesized from polymeric sulfides, which are solids with a minimal odour. The adducts contain a high concentration of borane, have significant stability and are soluble in THF. They act as hydroborating and reducing reagents with behaviour similar to that of borane-methyl sulfide, making them attractive borane sources.