Preparation and reactivities of chiral manganese(III) and copper(II) complexes of binaphthyl Schiff bases
作者:Chun-Wah Ho、Wing-Chi Cheng、Ming-Chuan Cheng、Shie-Ming Peng、Kin-Fai Cheng、Chi-Ming Che
DOI:10.1039/dt9960000405
日期:——
A series of chiral Schiff bases, 2,2′-bis(3-R1-5-R2-2-hydroxybenzylideneamino)-1,1′-binaphthyl H2L (R2= Cl, R1= Cl, Me, Et or NO2; R2= Me, R1= But; R2= NO2, R1= H, Me, Et, Pri, But or Cl), and their complexes [CuL1]1 and [Mn2L12(OMe)2]2(R1= R2= Cl) have been prepared. The crystal structure of the racemic form of 1 has been determined. Complex 1 is an active catalyst for the oxidation of alkenes by tert-butyl hydroperoxide. On the contrary, 2 is inert towards alkene epoxidation by PhIO. However, upon mixing Mn(O2CMe)3·xH2O and H2L in acetonitrile a green solution was obtained which could effect asymmetric epoxidation of alkenes by PhIO. The effects of the steric and electronic effects of the R1 and R2 substituents, temperature, and the addition of donors like N-methyl- and 2-methyl-imidazole and pyridine N-oxide on the catalytic activity of the MnIII+(S)-H2L systems towards alkene epoxidation have been investigated. When R1= Et and R2= NO2 the best enantiomeric excesses of 58 and 43% were found for epoxidation of cis-β-methylstyrene to (1S,2R)-cis-β-methylstyrene oxide and 4-chlorostyrene to 4-(S)-chlorostyrene oxide respectively.
一系列手性席夫碱,2,2'-双(3-R1-5-R2-2-羟基亚苄胺基)-1,1'-联萘H2L(R2=Cl,R1=Cl、Me、Et或NO2;R2=Me,R1=But;R2=NO2,R1=H、Me、Et、Pri、But或Cl)及其配合物[CuL1]1和[Mn2L12(OMe)2]2(R1=R2=Cl)已被制备。1的外消旋形式的晶体结构已被确定。配合物1是叔丁基过氧化氢氧化烯烃的活性催化剂。相反,2对PhIO引发的烯烃环氧化是无活性的。然而,将Mn(O2CMe)3·xH2O和H2L混合在乙腈中,获得了一种绿色溶液,这种溶液可以催化PhIO引发的对烯烃的不对称环氧化。已经研究了R1和R2取代基的立体和电子效应对MnIII+(S)-H2L体系催化烯烃环氧化的影响,以及温度和加入供体如N-甲基-和2-甲基咪唑以及吡啶N-氧化物的影响。当R1=Et和R2=NO2时,烯烃环氧化过程得到了最好的对映体过剩,分别为:将顺-β-甲基苯乙烯环氧化成(1S,2R)-顺-β-甲基苯乙烯氧化物,对映体过剩为58%;将4-氯苯乙烯环氧化成4-(S)-氯苯乙烯氧化物,对映体过剩为43%。