Bassam El Ali

Total regioselective control of the carbonylative coupling of 1-heptyne with aniline and N-methyl aniline catalyzed by palladium(II) and phosphine ligand

Abstract The carbonylative coupling of 1-heptyne ( 1a ) with aniline ( 2a ) has been successfully achieved in the presence of Pd(OAc) 2 and a suitable bidentate phosphine ligand and solvent. The gem -α,β-unsaturated amide ( 3aa ) was formed as a predominant product in the presence of the catalytic system Pd(OAc) 2 /1,3-bis(diphenylphosphino)propane (dppp)/ p -toluenesulfonic acid ( p -TsOH)/CO in THF as a solvent. While the use Pd(OAc) 2 and 1,4-bis(diphenylphosphino)butane (dppb), under syngas (CO/H 2 ) conditions and in CH 2 Cl 2 as a solvent, affords the trans -α,β-unsaturated amide ( 4aa ) as the major product. A minor cyclic product ( 5aa ) was formed via the double carbonylation reaction. The regioselective carbonylative coupling reaction was also successfully applied to N -methyl aniline ( 2b ) with 1-heptyne ( 1a ) producing excellent yields of tertiary unsaturated amides.

Regiochemical synthesis of straight chain acids by the palladium (II) catalysed hydrocarboxylation of olefins with oxalic acid

Abstract Olefins react with carbon monoxide and oxalic acid, catalysed by palladium acetate in the presence of 1,4-bis(diphenylphosphino)butane, to give linear carboxylic acids regioselectively or regiospecifically. This process shows excellent functional group tolerance.

H3+nPMo12−nVnO40-catalyzed selective oxidation of benzoins to benzils or aldehydes and esters by dioxygen

Abstract Heteropolyacids H 3+ n PMo 12− n V n O 40 (HPA- n , n =1–4) catalyze efficiently the oxidation and the oxidative cleavage of benzoin derivatives in the presence of dioxygen. HPA-2 gave the highest total yields in aldehydes and carboxylic esters by using primary alcohols as solvents. No oxidative cleavage products were obtained with secondary or tertiary alcohols. HPA-2 catalyzes the oxidation of benzoin to benzil in the presence of t -BuOH or other polar solvents such THF, CH 3 CN, DME.

Anticorrosion/antifouling properties of bacterial spore-loaded sol-gel type coating for mild steel in saline marine condition: a case of thermophilic strain of Bacillus licheniformis

This work reports the performance of a sol–gel type coating encapsulated with biofilm of inoculums of protective thermophilic strain of Bacillus licheniformis endospores isolated from the Gazan hot springs-Saudi Arabia for the inhibition of marine fouling and corrosion protection of S36-grade mild steel in 3.5 wt% NaCl medium. In order to improve its anticorrosion properties, the hybrid sol–gel coating is further doped with zinc molybdate (MOLY) and zinc aluminum polyphosphate (ZAPP) pigments. Marine fouling study was conducted at the Arabia Gulf water of Half Moon Bay, Al-Khobar, Saudi Arabia for 10 weeks on the coated samples with and without the bacterial endospores. The assessment of fouling results reveals that the bacterial endospores possess antifouling potentials since it performed better compared to its abiotic counterpart within the immersion period of study due to their foul-releasing effect. Improved corrosion and fouling resistant in the presence of the bacterial endospores could be attributed to their multi-layered hydrophobic and antibiotic coating surface after bacterial encapsulation. Spores accumulation in the sol–gel coating altered the surface wetness thereby preventing the diffusion of corrosion molecules and ions through the bulk of the coating to the metal surface; this is evident in the trend of electrochemical coating resistance and capacitance. Confocal laser scanning fluorescence and scanning electron microscopies were employed to probe bacterial viability and surface micro-cracks inherent in the coating, respectively. This is the first report of axenic thermophilic strain of Bacillus licheniformis isolated from the Arabian Gulf with inhibiting potentials against corrosion and fouling of industrial steel.

Novel hybrid epoxy silicone materials as efficient anticorrosive coatings for mild steel

Novel hybrid-sol–gel materials (C1–C5) based on silica–epoxy composite resins were successfully prepared by coupling different aminosilanes with DER736 epoxy resin, followed by an in situ sol–gel process, and finally introducing the urethane moieties to the final coatings. This research has emphasized the effect of changing the type of aminosilane on the properties of the prepared hybrid coatings. Three different aminosilanes were examined and their reaction parameters with the epoxy and the trialkoxysilanes were carefully optimized in order to avoid fast gelation and to obtain the desired properties of the hybrid coatings. The prepared organic–inorganic hybrid coatings were loaded and cured on mild steel panels and characterized for FTIR, NMR, TGA, water contact angles (WCA), nanoindentation hardness, pull-off adhesion, SEM, EIS and polarization studies. The results revealed that the coatings prepared from the trialkoxysilanes APTMS and MTMS (C4) demonstrate the best mechanical, anticorrosion and adhesion properties on mild steel substrates as compared to all other coatings in a 3.5 wt% NaCl medium. Electrochemical impedance spectroscopy (EIS) results indicated a corrosion resistance value for this coating in the range of 106 Ω cm2 after 10 days of continuous immersion in the saline medium. The SEM observations suggest that coatings produced from the other aminosilanes, APT-PDMS and APM–DMS are inhomogeneous and have some defects which have ultimately affected their barrier protection properties.

Pd(II)—dppb and syngas catalyze regioselective hydroesterification of terminal alkynes under neutral conditions

Palladium(II) regioselectively catalyzes the hydroesterification of terminal alkynes under syngas forming α,β-unsaturated esters 3 and 4 in excellent chemical yields under neutral conditions. The high selectivity for the linear ester 4 was obtained with a catalytic system that includes Pd(II), 1,4-bis(diphenylphosphino)butane (dppb) and CO/H2 in CH2Cl2 as solvent. The control of the regioselectivity depends strongly upon the type of ligand, the solvent and the use of the syngas mixture.

Synthesis of bislactones catalysed by a Pd–dppb system†

Palladium acetate [Pd(OAc) 2 ] and 1,4-bis(diphenylphosphino)butane (dppb) catalyse regioselective cyclocarbonylation of bisallyl derivatives of bisphenols affording seven-membered ring bislactones in good yields. Double cyclocarbonylation reactions carried out using different conditions afforded bislactones with two different ring sizes (7-6 and 7-5-membered).

Effective palladium(II)-bis(oxazoline) catalysts: synthesis, crystal structure, and catalytic coupling reactions

New bis(oxazoline) ligands and their palladium complexes were synthesized and characterized. X-ray crystal structures of the two new complexes showed distorted square planar geometry with the palladium ion bonded to nitrogens of two bidentate heterocycles in addition to two bromides and two acetate ions for Pd-BOX-1 and Pd-BOX-2, respectively. The complexes adopt a chair structure with a rigid curvature inducing an inherent chirality. The complexes were effective catalysts for Suzuki–Miyaura, Mizoroki–Heck, and copper-free Sonogashira coupling reactions in aqueous dimethylformamide and under aerobic conditions. The reaction conditions were optimized for best solvent, base, and temperature. The substrate scope of the new catalytic system was evaluated for coupling reactions of a variety of aryl halides with aryl boronic acids, alkenes, and alkynes.

Catalytic and selective synthesis of lactones and bis-lactones by palladium acetate/1,4-bis(diphenylphosphino)butane system under syngas conditions

The combination of palladium acetate and 1,4-bis(diphenylphosphino)butane (dppb) proved once again to form an effective catalytic system for the selective cyclocarbonylation of 2-allyl phenols and other bis-2-allyl phenol systems such as steroids and other important compounds. The reactions afforded new important five-, six- and seven-membered ring lactones and bis-lactones. The seven-membered ring lactones were predominant in most reactions.

Palladium complex–potassium carbonate-catalysed reductive carbonylation of mono- and di-nitroaromatic compounds

Mono- and di-nitroaromatic compounds react with carbon monoxide in benzene containing methanol, with catalytic quantities of 1,3-bis(diphenylphosphino)propanepalladium dichloride and potassium carbonate as the base, to give urethans in reasonable yields.