tailieunhanh - Modified Binh Thuan bentonite as an efficient and recyclable catalyst for the suzuki reaction between iodobenzene and phenylboronic acid

The reaction was performed using mol% catalyst at 100o C in dimethylformamide (DMF) and in the presence of K3PO4 as a base, with biphenyl being formed in a conversion of up to over 95% (GC) without added phosphine ligands. It was also observed that the modified bentonite catalyst could be facilely separated from the reaction mixture by centrifugation or simple filtration, and could be reused in subsequent reactions without significant degradation in activity. | Journal of Chemistry, Vol. 46 (4), P. 509 - 514, 2008 MODIFIED BINH THUAN BENTONITE AS AN EFFICIENT AND RECYCLABLE CATALYST FOR THE SUZUKI REACTION BETWEEN IODOBENZENE AND PHENYLBORONIC ACID Received 7 December 2007 PHAN THANH SoN NAM, TRuoNG NGUYeN THuY Vu, TRuoNG Vu THANH Hochiminh University of Technology SUMMARY Modified Binh Thuan bentonite catalyst was prepared by exchanging with aqueous solution of PdCl2, affording a catalyst loading of mmol of Pd/g (ICP-MS). The Pd2+-exchanged bentonite catalyst was assessed for its activity in the the Suzuki cross-coupling reaction between iodobenzene and phenylboronic acid to form biphenyl as the principal product. The reaction was performed using mol% catalyst at 100oC in dimethylformamide (DMF) and in the presence of K3PO4 as a base, with biphenyl being formed in a conversion of up to over 95% (GC) without added phosphine ligands. It was also observed that the modified bentonite catalyst could be facilely separated from the reaction mixture by centrifugation or simple filtration, and could be reused in subsequent reactions without significant degradation in activity. I - INTRODUCTION Transition metal-catalyzed cross-coupling reactions have attracted interests over the past thirty years in organic synthesis, in particular as convenient techniques for the formation of carbon-carbon bonds [1]. Numerous reactions have been developed to achieve cross-coupling, of which the Suzuki reaction is one of the most efficient methods for the synthesis of biaryl derivatives [2]. These biaryl units have exhibited practical applications in the production of pharmaceuticals, herbicides, as well as engineering materials such as conducting polymers and liquid crystals [3]. Catalysts used in the standard Suzuki processes are generally based on homogeneous palladium phosphine complexes, which are rarely recoverable without elaborate and wasteful procedures, and therefore commercially undesirable. Phosphine ligands are .