钛(Ⅳ)催化Meerwein-Ponndorf-Verley-Oppenauer反应  

TITANIUM COMPOUNDS AS CATALYSTS IN MEERWEIN - PONNDORF - VERLEY - OPPENAUER REACTION

作　　者：李春玲[1] 丘昌隆[1] 郭宏勋 

机构地区：[1]兰州大学化学系

出　　处：《分子催化》1990年第3期173-180,共8页Journal of Molecular Catalysis(China)

摘　　要：本文研究了各种Ti(Ⅳ)化合物:Ti(OR)_4(R=Et,~iPr,~nBu),TiCl_4,CP_2TiC_2,Cp_2Ti(OPh)_2对Meerwein-Ponndorf-Verley-Oppenauer反应的催化活性。试验表明Ti(O^iPr)_4对还原反应显示出极好的催化活性,还原苯甲醛,对氯苯甲醛,对硝基苯甲醛,对甲氧基苯甲醛,糠醛,巴豆醛的产率可达80％以上。Ti(OEt)_4对氧化反应有良好的催化活性,对正辛醇,2-辛醇,苯甲醇,环已醇,肉桂醇的氧化产率在69％以上。同时还考察了各种参数对反应的影响。Meerwein- Ponndorf - Verley reduction of aldehydes and ketones and Oppenauer oxidation of alcohols have been known for a long time. These reactions are useful tools for the synthesis of various organic compounds. Although extensive studies of the experimental conditions of these reactions have been performed, the requirement of using great amount of reagents, usually in stoichiometric quantities (or even an excess) severely limits its application to a wide range of organic substrates. Only a few examples using aluminum alkoxides in catalytic amount have appeared in the literature. In this paper, six titanium compounds, i.e. Ti( OR) 4 ( R = Et, iso -Pr, n-Bu), TiCl4, Cp2TiCl2, Cp2Ti(OPh)2 were used as catalysts in the reactions, and it was found that they have different catalytic activities. In the reductions, Ti(O - iso - Pr)4 has excellent catalytic activities. Good results were obtained for benzaldehyde ( 98% ) , p - nitro-benzaldehyde ( 100% ) , p-methoxybenzaldehyde (94%), crotonaldehyde (<89%)and furaldehyde (86%) (yield is given in parenthsis) with the used 0.1 mole equivalent of catalyst with respect to the substrate.Reduction of different ketones gave rather low yields of secondary alcohols, which indicate that catalytic amount of Ti(O-iso-Pr)4 can not reduce ketones effectively. Reaction mechanism of the aldehyde reduction has been discussed, and a catalytic cycle similar to the Zr(O-n-Bu)4 is suggested ( see the figure on p.176). Carbonyl compound is coordinated with Ti(O-iso-Pr)4 to form a penta-coordinated active intermediate complex, then it undergoes intermolecular hydrogen transfer and elimination of acetone, and gives the reduction product. The best catalyst for the oxidations is Ti(OEt)4 and its amount is 0.05 mole equivalent with respect to the substrate. The yields of oxidation of 2-octanol, 1 - octanol, benzyl alcohol, cyclohexanol and cinnamyl alcohol are more than 69%. Different oxidants were examined, and the results are rather complicated. For the oxidation of 2 -octanol, trichlor

关 键 词：钛 还原反应 催化活性 

分 类 号：O643.38[理学—物理化学]