Selective Oxidation Examples of Directions to Improve Sustainability

3 Selective Oxidation Examples of Directions to Improve Sustainability 

Another very interesting example from the same group is the use of Sn-Beta for the synthesis of melonal (2,6-dimethyl-5-hepten-l-al), a fragrance that is produced industrially by a Darzens reaction from 6-methyl-5-hepten-2-one, with ethyl chlor-oacetate as reagent. A novel halogen-free synthesis involves the chemoselective 

Chemoseiective Baeyer-Viiiiger oxidation with Sn-Beta 

Some of these W-based catalysts could be transformed into insoluble salts for example, the phosphotungstate-pyridinium salt in a toluene-tributyl phosphate (4 3) solvent mixture [328]. In this solvent the pre-catalyst is insoluble, but upon reaction with H2O2 it gives the catalytically active W-peroxo complex, which is soluble. The catalytic action is then performed under homogeneous conditions and, at the end of the reaction, H2O2 being completely consumed, the precatalyst precipitates and can be easily filtered off and recovered. The method is smart, but from an industrial point of view the separation and recovery is costly. 

Novel Pathways and Reactants This is a very broad area. We will thus restrict discussion to few examples. The first regards the important reaction of phenol synthesis and the possibility to realize it in one step directly from benzene using molecular oxygen as the oxidant. Various aspects of direct phenol synthesis from benzene are discussed in Chapter 13. We highlight here only recent results that exemplify how starting from the previously cited activity of Re complexes in the epoxidation in homogeneous phase could lead to investigation of the behavior of Re complexes when inserted into the channels of zeolites (ZSM-5) and in gas-phase selective oxidations. This has opened a new unexpected direction. 

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