Abstract
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.
Highlights
The palladium catalyzed Heck cross-coupling reaction of aryl halides with terminal alkenes, which provides a powerful tool for the formation of aryl-alkenes,[13,14,15] has been widely applied to such diverse areas as natural product syntheses and material sciences
The outline for the preparation of the polymer-anchored Schiff base complex is presented in Scheme 1
The metal content of polymeranchored Pd(II) complex determined by atomic absorption spectrophotometer (AAS) suggested 2.23 wt% metal loading in the immobilized palladium complex
Summary
Transition metal-catalyzed carbon-carbon bond forming reactions are widely employed methods in modern organic chemistry.[1,2,3] The use of such catalytic procedures has found applications in the preparation of many natural products, as well as in materials science and the agrochemical industry.[4,5,6,7] With various metals being employed in coupling reactions, palladium probably is the most frequently chosen transition metal due to its excellent catalytic efficiency in this type of reactions.[8,9,10,11,12] The palladium catalyzed Heck cross-coupling reaction of aryl halides with terminal alkenes, which provides a powerful tool for the formation of aryl-alkenes,[13,14,15] has been widely applied to such diverse areas as natural product syntheses and material sciences. The most common catalytic system used for this reaction is the homogeneous palladium-phosphine complexes[16,17,18,19,20] as PdCl (PPh ) or Pd(PPh ) in presence of base. The heterogenization of homogeneous catalytic reactions has attracted great attention from a wide range of organic chemists over the last few decades.[26,27,28,29,30] Immobilizations of homogeneous catalysts into insoluble polymeric supports by covalent bonding or complexation enables the easy recovery and reuse of catalysts. We have reported an efficient procedure for a heterogeneous phosphine-free Heck cross-coupling reaction of aryl halides with terminal alkenes using PS-[(C6H4CH=N)Pd(OAc)]2 as the catalyst and K2CO3 as the base
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