Mansur B. Ibrahim

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.

A palladium–bisoxazoline supported catalyst for selective synthesis of aryl esters and aryl amides via carbonylative coupling reactions

The catalytic synthesis of aryl esters and amides has been successfully achieved in the presence of the efficient palladium–bisoxazoline supported on Merrifields resin (Pd–BOX-M). The palladium heterogeneous catalyst was prepared and characterized using various spectroscopic techniques. A bisoxazoline ligand having a suitable functional group (BOX-OH) was first synthesized, characterized, chemically supported on Merrifields resin, and finally coordinated to palladium(II) chloride. The catalytic activity and the recycling ability of the new palladium supported catalyst have been investigated in the alkoxycarbonylation and aminocarbonylation of various aryl iodides using different alkyl and aromatic alcohols and amines as nucleophiles. The palladium heterogeneous catalyst demonstrated excellent catalytic activity and very high recycling ability in the above two carbonylation reactions. The palladium heterogeneous catalysts showed an excellent stability under carbon monoxide and under the experimental conditions.

A silica-supported palladium-bis(oxazoline) complex efficiently catalyzes the synthesis of cinnamic acid derivatives via Mizoroki–Heck coupling reactions

A palladium(II)-bis(oxazoline) complex supported on silica (Pd-BOX-Si) was prepared, characterized and applied as a catalyst in Mizoroki–Heck cross-coupling reactions. The bis(oxazoline) (BOX) ligand has a hydroxyl group that can be anchored to 4-benzyl chloride-functionalized silica gel, followed by the coordination of palladium(II) chloride. The catalytic activity and the recyclability of Pd-BOX-Si have been investigated in the production of cinnamic acid derivatives via Mizoroki–Heck coupling reactions of acrylates with aryl halides; The Pd-BOX-Si catalyst demonstrated excellent catalytic activity. Characterization of the recycled Pd-BOX-Si catalyst revealed its good stability under the reaction conditions employed.

New palladium-bis(oxazoline)-phosphine complexes: synthesis, characterization and catalytic application in alkoxycarbonylation of alkynes

Abstract New cationic palladium-bis(oxazoline)-phosphine (Pd-BOX-PR3) complexes (Pd-BOX-B and Pd-BOX-C) have been synthesized and characterized using 1H, 13C and 31P NMR, FTIR spectroscopy, and electrospray ionization mass spectrometry (ESI-MS). The new complexes were used as catalysts in the alkoxycarbonylation of alkynes with various alcohols as nucleophiles. The carbonylation has produced the gem-α,β-unsaturated ester isomer (3) in high regioselectivity and excellent yields. The catalyst systems have been optimized by screening the type of palladium complexes and also by varying the reaction parameters including the reaction time, solvent, and temperature. A mechanism of the catalytic cycle based on a N-protonated palladium bis(oxazoline) phosphine active species was proposed for the alkoxycarbonylation reaction.

Synthesis, crystal structures and catalytic activities of new palladium(II)–bis(oxazoline) complexes

Abstract Palladium–bis(oxazoline) complexes (Pd-BOX-A and Pd-BOX-B) were synthesized and characterized by 1H, 13C NMR, IR and elemental analysis. The molecular structures of the complexes were confirmed by single-crystal X-ray analysis. In both cases, the palladium center is coordinated by the nitrogen atoms of the two oxazoline rings and two chloride ligands in a distorted square planar geometry. Despite the fact that the bis(oxazoline) ligand is achiral, the asymmetrical substitution on the phenyl spacer and the rigid backbone of the complex Pd-BOX-A induce inherent chirality and the compound crystallizes as a racemic mixture. Both complexes were found to be highly effective catalysts for Suzuki–Miyaura, Mizoroki–Heck and Sonogashira cross-coupling reactions. They also show excellent catalytic activities toward carbonylative coupling reactions.