Davis oxidant

Cheng, L., E. Peake, D. Rogers, and A. Davis, Oxidation of Nitric Oxide Controlled by Turbulent Mixing in Plumes from Oil Sands Extraction Plants, Atmos. Enriron., 20, 1697-1703 (1986). 

Colophony-Starch Nitrated Mixture, called hy Davis Oxidized Rosin and by its inventor E. Steele Residee. Colliery expls contg it are known as Steelites (Brit). See Vol 3, p C404-L... 

Colophony —Starch Nitrated Mixture (called by Davis Oxidized Rosin and by its inventor E, Steele Residee). It is a solid prepd by treating an intimate mixture of finely pulverized colophony 90 Sc starch 10% with cold 42 Be nitric acid. A homogeneous solid, tormed after several mins, was used as an ingredient in the prepn of potassium chlorate expls, known as Steelites. For their prepn, finely pulverized and dried K chlorate residee, in desired propns, were slightly moistened... 

Cyclohexyl selenides 162 can be prepared from the 4-substituted cyclohexanones via the selenoketals and upon oxidation with chiral oxidants, compounds 163 were obtained in high yields and with excellent stereoselectivities. Some representative examples are summarized in Table 5 and it is obvious that only the Davies oxidant 158 is leading to high enantiomeric excesses in the product 163 whereas under Sharpless oxidation conditions no selectivity is obtained. The titanium complex formed in the Sharpless oxidant may promote the racemization of the intermediate selenoxide by acting as a Lewis acid catalyst, while the aprotic nature of the Davies oxidant 158 slows down racemization dramatically. 

Asymmetric [2,3]sigmatropic rearrangements can proceed via optically active selenoxides. It has been shown that the Davis oxidant 158 can be used for the oxidation of selenides such as 172. The reaction product, after oxidation and rearrangement, is the allylic alcohol 173 formed with 35% ee (Scheme 50).279,282 Also Sharpless conditions (Ti(/ -PrO)4, (+)-DIPT, /-BuOOH) have been applied to this reaction and the product has been obtained in 69% ee. When, however, the phenyl selenide moiety in 172 is replaced with an or/ < -nitrophenyl selenide, the selectivity is increased to 92% ee in the allylic alcohol 173 using Sharpless conditions.296 Other selenides such as 2 -pyridyl or ferrocenyl selenides gave much lower selectivities. 

In the former case, almost complete stereoselective oxidation to the chiral selenoxides has been accomplished quite recently. The Davis oxidant, 3,3-di-chloro-l,7,7-trimethyl-2 -(phenylsulfonyl)spirobicyclol2.2.11heptane-2,3 -oxa-ziridine, was found to be the most efficient reagent for the enantioselective oxidation of a variety of prochiral alkyl aryl selenides [81. Asymmetric oxidation was accomplished by the treatment of the selenides with 1 molar equivalent of the Davis oxidant at 0°C to afford the corresponding chiral alkyl aryl selenoxides in quantitative yields with 91-95% ee (Scheme 1). The oxidation of methyl phenyl selenide was complete within 1 min, whereas that of triiso-propyl(a bulkier alkyl) phenyl selenide required a few hours. Typical results are... 

Scheme 1. Asymmetric oxidation of the prochiral selenides to the selenoxides using the Davis oxidant...

Thus, when cyclohexyl selenides 1, prepared from the corresponding 4-sub-stituted cyclohexanone via the selenoketals, were oxidized with various Davis and Sharpless oxidants, the chiral alkyl aryl 4-substituted cyclohexylidenemethyl ketones were obtained in excellent chemical yields with high enantiomeric excesses. Typical results are summarized in Table 4. In this asymmetric induction, of the substrate and the chiral oxidant employed were revealed to show a remarkable effect upon the enantioselectivity of the product. The use of a methyl moiety as instead of a phenyl moiety gave a higher ee value, probably due to the steric difference between the two groups bonded to the selenium atom of the substrate. The results indicate that the titanium complex of the Sharpless oxidant may promote the racemization of the chiral selenoxide intermediate by acting as a Lewis acid catalyst, whereas the racemization in the case of the Davis oxidant, which is aprotic in nature, is slow. 

OAKIN Oxidation 84 DAKIN WEST Acylation 84 DANHEISER Annulation 85 DANISHEFSKY Sitytoxydenes 66 DARAPSKI Ammoacid synthesis 87 DARZENS-NENITZESCU Acylation 87 DAR2fENS Epoxide synthesis 88 DAVIDSON Oxazola synthesa 89 OELEPINEAMehydeoxidalion 89 DAVIS Oxidizing reagent 90 Decker 127... 

Proceedings of the 9th International Symposium, Lexington, KY, USA, October 2001 edited by J.J. Spivey, G.W. Roberts and B.H. Davis Oxide-based Systems at the Crossroads of Chemistry. 

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