Epoxidation vanadium catalysed

The polymer boxmd peroxocomplexes prepared in the present work have excellent catalytic potentiality and selectivity in the production of quinones. The chromium peroxocomplexes loses its activity on reaction and could be regenerated. The pwlymer bound vanadium catalyses sharpless epoxidation reactions. The high pore volume and a marginally good surface area shows that GMA-EGDM copolymers are good choice as supports. 

A study of the epoxidation of allylic alcohols by various epoxidizing agents has shown that there are a number of errors in earlier work. It has now been shown that vanadium-catalysed epoxidation favours formation of the erythro-epoxy-alcohol (8), whereas peracid epoxidation gives excess of the r/treo-epoxy-alcohol (9) 20 appears, however, to be some confusion over molybdenum-... 

Two separate reports on the vanadium-catalysed epoxidation of allylic alcohols have appeared. In the case of secondary acyclic E -allylic alcohols opposite stereospecificity to peracid and molybdenum-catalysed systems is observed. This... 

The asymmetric oxidation of sulphides to chiral sulphoxides with t-butyl hydroperoxide is catalysed very effectively by a titanium complex, produced in situ from a titanium alkoxide and a chiral binaphthol, with enantioselectivities up to 96%342. The Sharpless oxidation of aryl cinnamyl selenides 217 gave a chiral 1-phenyl-2-propen-l-ol (218) via an asymmetric [2,3] sigmatropic shift (Scheme 4)343. For other titanium-catalysed epoxidations, see Section V.D.l on vanadium catalysis. 

The importance of 1,2- rather than 1,3-allylic strain in the vanadium(V)-catalysed BufOOH epoxidation directed by hydroxy groups has been assessed using (Z)-3-en-2-ols as model substrates344. 

If substituents on the sulphur are more electron-withdrawing, or to obtain faster reaction, activated peroxygen systems can be used to make sulphoxides, overoxidation to sulphones being minimised simply by controlling temperature and addition rate, at the correct molar ratio. Examples include H2O2 catalysed by tungsten(VI), vanadium(V) [213], molybdenum(VI) [214], or selenium(IV) [215], and peracetic acid (which, as for epoxidations, works better in non-protic media) [216]. Sodium perborate in acetic acid is also effective [217]. 

The mechanism of olefin epoxidation with iodosylbenzene in the presence of Cr(III) Schiff base complexes has been studied.The same reaction is catalysed by V0(acac)2 probably yij free radicals.Trans-stilbene is epoxidised by NalOi, in the presence of RuClg and substituted phenanthroline ligands. Vanadium(V) supported on a functionalised polystyrene resin is a good catalyst for the epoxidation of allylic alcohols by ButQOH a similar Mo(VI) catalyst is more suitable for cyclohexene epoxidation. ... 

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