Heterogeneously catalyzed phosphine-free heck cross-coupling reaction of aryl halides with reusable palladium(II) schiff base complex

Abstract

O acoplamento entre haletos de arila e terminais alceno (reação de Heck) foi investigado na presença de catalisadores de paládio (II) suportados em poliestirenos contendo bases de Schiff. O catalisador é estável frente ao ar e umidade, e tem atividade catalítica significativa nas reações de acoplamento cruzado de Heck sob condições normais. Vários haletos de arila e alcenos terminais foram facilmente acoplados na presença de ar, fornecendo os correspondentes produtos de acoplamaneto cruzado, em ótimos rendimentos. O catalisador é facilmente recuperado quantitativamente por filtração simples e reutilizado por até sete ciclos sem perda de atividade.The coupling between aryl halides with terminal alkenes (Heck reaction) has been investigated in the presence of a polystyrene-supported Schiff base palladium(II) catalyst. The present catalyst is air and moisture-stable and has significant catalytic activity in Heck cross-coupling reactions under operating conditions. Various aryl halides and terminal alkenes were coupled smoothly under air, to afford the corresponding cross-coupled products in excellent yields. Furthermore, the catalyst can be easily recovered quantitatively by simple filtration and reused up to seven cycles without losing its activity.

Tetradentate N2O2 Chelated Palladium(II) Complexes: Synthesis, Characterization, and Catalytic Activity towards Mizoroki‐Heck Reaction of Aryl Bromides

“…Having established the optimum catalytic conditions, using NaOAc as a base and with 0.5 mmol% catalyst loading, the performance of catalyst 2c was further screened at different reaction temperatures (Table 3). It is well known that the reaction temperature has a very strong in�uence on Heck cross-coupling reaction [41]. However, reaction temperature must be carefully controlled to avoid the formation of palladium black which will inhibit the catalytic cycle if the temperature is too high [42].…”

Bimetallic Substituted Ceria: An Alternative Approach to Ligand-Free Heck-Mizoroki Cross-Coupling Reactions

“…Typically Heck reactions-as with many cross-coupling reactions-are palladium-catalysed [1]. Classically, homogenous catalyst systems are used in the industrial applications of Heck reactions [2][3][4][5][6][7]. Naturally, while homogenous systems have high turn-over frequencies (TOFs), their major disadvantage is the inability to be efficiently seperated from the final product.…”

“…Naturally, while homogenous systems have high turn-over frequencies (TOFs), their major disadvantage is the inability to be efficiently seperated from the final product. Incorporation of the catalyst in turn decreases the quality of the final product in terms of purity [5,6,[8][9][10][11][12][13]. For pharmaceutical products, incorporation of the catalyst can be detrimental, but most notable is the economic consideration, since palladium is a precious metal and is thus expensive and offers limited recycling prospects as a homogenous catalyst [5,14,15].…”

“…Fortunately, immobilised homogenous systems, through covalent bonding, encapsulation and/or complexation, provide a more stable catalyst that can be recycled [5]. Furthermore, supported metal catalysts, where the active metal is on a solid support, have increased the palette of materials that can be applied [5]. These materials range from carbon supports, to zeolites, porous glass, clays, metal oxides, organic polymers, molecular sieves, and various combinations of the materials mentioned.…”

Terephthalic acid derived ligand‐stabilized palladium nanocomposite catalyst for Heck coupling reaction: without surface‐modified heterogeneous catalyst

“…chlorine is less reactive when compared with bromine and bromine is less reactive than iodine under general conditions; however, chlorine gives good results with palladium catalysts with bulky phosphine ligands or carbenes . Aminopropyl‐functionalized clay has been used as a support to prepare a palladium nanocatalyst for Heck and Suzuki cross‐coupling reactions . Whereas a colloidal catalyst was not recycled quantitatively, with some exceptions on heterogeneous supports (such as silica, zeolites, carbon nanotubes, graphite oxide and graphene, polymers, metal–organic frameworks), on the other hand, surface‐modified palladium nanocomposites were used as heterogeneous catalysts wherein effective recovery of the catalyst was reported …”