Effect of boron alkoxides as homogeneous and heterogeneous catalysts on reduction of aldehydes and ketones and examination of reduction reaction kinetic

In the present study, MCM-41, one of the most important materials of mesoporous material class with high surface area and ordered pore structure, was prepared. A new heterogeneous catalyst denoted as B(OiPr)3-MCM-41 was prepared by grafting of boron tri-isopropoxide (B(OiPr)3) on synthesized MCM-41. This catalyst was characterized in details by using XRD, FTIR, 11B NMR, 29Si NMR, 13C NMR spectroscopies, SEM, TEM, EDX techniques, N2 adsorption?desorption isotherms and ICP-OES analysis. A new hybrid material ?(B(OiPr)3-MCM-41)? was tested in the chemoselective Meerwein?Ponndorf?Verley (MPV) reduction of ?,ß-unsaturated carbonyl compounds and proved as highly active catalyst. In the reduction of ?,ß-unsaturated aldehydes and ketones, a very high selectivity for the allylic alcohols is obtained. In most cases, there were no side products other than the desired alcohol. The grafted boron akoxide catalyst did not lose its activity after sixth run, making it easy to reuse. No leaching of the grafted boron tri-isopropoxide into the reaction mixture was observed.Also catalytic activity of two different boron alkoxide compounds ?[B(OEt)3] and [B(OiPr)3]? on the reduction of various substitue, cyclic, unsaturated and aromatic aldehydes and ketones as homogeneous catalysts were studied and reaction kinetic were also examined. MPV reduction reactions of homogeneous catalysts ?[B(OEt)3] and [B(OiPr)3]? were compared with in the presence of prepared heterogeneous catalyst ?B(OiPr)3-MCM-41? for chemoselective reduction of ?,ß-unsaturated aldehydes and ketones to allylic alcohols.When compared reduction reactions occur in the presence of homogeneous and heterogeneous catalysts, the reducing reactions in the presence of homogeneous catalysts take longer time than heterogeneous catalyst, and product alcohol yields almost the same. In the presence of two catalysts type, obtained product alcohol yield and chemoselectivity of the reduction reactions are rather good, so this prove that reduction reactions in the presence of boron alkoxides is important for production of important industrial alcohols. In this accomplished studie, when the recycling advantage of heterogeneous catalyst is thought, a promising new catalyst in point of industry was improved.KEY WORDS: Homogeneous catalyst, heterogeneous catalyst, MCM-41, B(OiPr)3-MCM-41, MPV reduction reaction, boron alkoxides