In the presence of a bis(1,3-diketonato)nickel(II) complex, various olefins are directly monooxygenated into the corresponding epoxides on treatment with atmospheric pressure of oxygen or air and aldehydes. Especially, it is noted that bis[1,3-bis(p-methoxyphenyl)-1,3-propanedionato]nickel(II) behaves as an excellent catalyst in the present epoxidation.
Selective epoxidation of monoterpenes with methyltrioxorhenium and H2O2
作者:Aída L.P. de Villa、Dirk E. De Vos、Consuelo C. de Montes、Pierre A. Jacobs
DOI:10.1016/s0040-4039(98)01853-x
日期:1998.11
terpenes such as α-pinene with H2O2 with minimal rearrangement of the epoxide. Pyridine is also critical to suppress isomerisation of the olefin substrate (in case of nerol, geraniol). The reaction can be directed towards selective single or double epoxidation, or in one step towards the rearranged product (e.g. from linalool to the ring-closure product linalool oxide).
在吡啶作为助催化剂的存在下,CH 3 ReO 3以最小的环氧基重排催化H 2 O 2对萜烯(如α-pine烯)的环氧化。吡啶对于抑制烯烃底物的异构化也是至关重要的(如果是神经醇,香叶醇)。该反应可以针对选择性的单或双环氧化,或在一步中针对重排的产物(例如从芳樟醇到闭环产物芳樟醇氧化物)。
The selectivities and the mechanism on highly efficient epoxidation of olefins with 2,6-disubstituted pyridine N-oxides catalyzed by ruthenium porphyrin
作者:Hiro Ohtake、Tsunehiko Higuchi、Masaaki Hirobe
DOI:10.1016/s0040-4039(00)92231-7
日期:1992.4
Several remarkable selectivities in competitive epoxidations using a ruthenium porphyrin/ 2,6-disubstittuted pyridine N-oxide system were observed. The proposl that the active intermediate of this system differed from the trans-dioxo complex of ruthenium porphyrin was indicated.
In the presence of a catalytic amount of a bis(1,3-diketonato)nickel(II) complex, trisubstituted and exo-terminal olefins or norbornene analogues are smoothly monooxygenated into the corresponding epoxides in high to quantitative yields on treatment with aldehyde under an atmospheric pressure of oxygen at room temperature.
Catalytic epoxidation of monoterpenes with aqueous hydrogen peroxide catalyzed by peroxotung-stophosphate (PCWP) under biphase conditions using chloroform as the solvent was examined. A variety of terpenes was oxidized to the corresponding monoepoxides or diepoxides in good yields under mild conditions. For example, limonene (1) was converted into limonene oxide (la) in which the cyclohexene double bond was selectively epoxidized in almost quantitative yield. The oxidation of gamma-terpinene (2) with 2.2 equiv of 35% H2O2 took place with high stereoselectivity to give cis-diepoxide 2c. In terpenes bearing electron-withdrawing groups such as neryl acetate (3), geranyl acetate (4), citral (5), and geranyl nitrile (6), the double bonds remote from the substituents were epoxidized in preference to the others. The epoxidation of linalool (9) by the present catalyst-oxidant system produced the cyclic products, hydroxy furan 9a and hydroxy pyran 9b, rather than epoxide. tert-Butyl alcohol was successfully employed as the solvent by treating a hydrogen peroxide solution of tert-butyl alcohol with MgSO4 prior to use. The regioselectivities in the epoxidation of monoterpenes can be favorably explained from the electron densities of the double bonds which were estimated using the CAChe system.