Homogeneous Catalysts - Hydrogen Peroxide as the Terminal Oxidant

Homogeneous Catalysts - Hydrogen Peroxide as the Terminal Oxidant 

In more recent work, Noyori and coworkers found conditions for the selective epoxidation of aliphatic terminal alkenes either in toluene, or using a completely solvent-free reaction setup [23, 24]. One of the disadvantages with the previous 

A major limitation of this method is the low pH at which the reactions are performed. This led to substantially lower yields in reactions with substrates leading to acid-sensitive epoxides, where competing ring-opening processes effectively reduced the usefulness of the protocol. As an example, the oxidation of styrene led to 70% conversion after 3 h at 70 ° C, although the observed yield for styrene oxide was only 2% (Table 2.3, entry 5). 

When the (aminomethyl)phosphonic acid was replaced by other phosphonic acids or simply by phosphoric acid, significantly lower conversions were obtained. The nature of the phase-transfer reagent was further established as an important para- 

2 Transition Metal-catalyzed Epoxidation of Alkenes 1.5 equiv. H2O2 (35% aq) 

More recently, Sundermeyer and coworkers reported on the use of long-chain trialkylamine oxides, trialkylphosphane oxides or trialkylarsane oxides as mono-den- 

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