The mechanism of carbon dioxide catalysis in the hydrogen peroxide n-oxidation of amines
The mechanism of carbon dioxide catalysis in the hydrogen peroxide n-oxidation of amines
复制标题
DOI：
10.1021/ic701402h
复制
发表时间：
2008-02-04
影响因子：
4.6
通讯作者：
Richardson, David E.
中科院分区：
文献类型：
--
作者：
Balagam, Bhararthi;Richardson, David E.
研究了过氧单碳酸盐离子HCO4-在脂肪胺氧化反应中的反应活性。叔胺以较高的产率被氧化成相应的N-氧化物，而仲胺则生成相应的硝酮。提出了在25℃时，CO2(低于1大气压)和H_2O_2催化H_2O_2氧化叔胺的密切相关机理。得到了N-甲基吗啉(1)氧化为N-甲基吗啉N-氧化物和N，N-二甲基苄胺(2)氧化为N，N-二甲基苄胺N-氧化物的速率规律。在水/丙酮(5：1)中，HCO4-氧化反应的二级速率常数为k(1)=0.016 M-1 S(-1)，2为k(1)=0.042 M-1 S(-1)。HCO4-氧化叔胺的二级速率常数比单独氧化H_2O_2的速率常数大400多倍。报道了在水中用HCO4-氧化1的活化参数(Delta H-双匕首=36+/-2kJ mol(-1)和Delta S-双匕首=-154+/-7Jmol(-1)K-1)。BAP(NH4HCO3活化的过氧化氢)或CO2/H_2O_2氧化试剂是制备叔胺N-氧化物的简单、经济的方法。反应进行到完全，不需要萃取，并且在水介质中以优异的产率提供纯N-氧化物。
The reactivity of the peroxymonocarbonate ion, HCO4- (an active oxidant derived from the equilibrium reaction of hydrogen peroxide and bicarbonate), has been investigated in the oxidation of aliphatic amines. Tertiary aliphatic amines are oxidized to the corresponding N-oxides in high yields, while secondary amines give corresponding nitrones. A closely related mechanism for the H2O2 oxidation of tertiary amines catalyzed by CO2 (under 1 atm) and H2O2 at 25 degrees C is proposed. The rate laws for the oxidation of N-methylmorpholine (1) to N-methylmorpholine N-oxide and N,N-dimethylbenzylamine (2) to N,N-dimethylbenzylamine N-oxide have been obtained. The second-order rate constants for the oxidation by HCO4- are k(1)= 0.016 M-1 s(-1) for 1 in water and k(1) = 0.042 M-1 s(-1) for 2 in water/acetone (5:1). The second-order rate constants for tertiary amine oxidations by HCO4- are over 400-fold greater than those for H2O2 alone. Activation parameters for oxidation of 1 by HCO4- in water are reported (Delta H-double dagger = 36 +/- 2 kJ mol(-1) and Delta S-double dagger = -154 +/- 7 J mol(-1) K-1). The BAP (NH4HCO3-activated peroxide) or CO2/ H2O2 oxidation reagents are simple and economical methods for the preparation of tertiary amine N-oxides. The reactions proceed to completion, do not require extraction, and afford the pure N-oxides in excellent yields in aqueous media.