Hydrogen bromide epoxides

It appears necessary to effectively remove the residual o-xylenc during this distillation in order that it not interfere (by liberation of hydrogen bromide) with the subsequent bromination of the epoxide. The checkers used a spinning-band column for this distillation. 

Trichlorobenzene. Trichloroethylene Hydrogen azide, see Alachlor. Aldicarb. Atrazine Hydrogen bromide, see Ethylene dibromide Hydrogen chloride, see Atrazine. Captan. Carbon tetrachloride. Chloroform. Chlorpropham. Chlorpyrifos. 1.2-Dichloroethane. Diuron. Endrin. Formaldehyde. Heptachlor. Heptachlor epoxide. Hexachlorocyclopentadiene. Linuron. Methyl chloride. Methylene chloride. Methyl formate. Monuron. Propanil. Tetrachloroethylene. Trichloroethylene. Vinyl chloride Hydrogen cyanide, see Acetontrile. Alachlor. Aldicarb. 

Iodine-catalysed hydroperoxidation of cyclic and acyclic ketones with aqueous hydrogen peroxide in acetonitrile is an efficient and eco-friendly method for the synthesis of gem -dihydroperoxides and the reaction is conducted in a neutral medium with a readily available low-cost oxidant and catalyst.218 Aryl benzyl selenoxides, particularly benzyl 3,5-bis(trifluoromethyl)phenyl selenoxide, are excellent catalysts for the epoxidation of alkenes and Baeyer-Villiger oxidation of aldehydes and ketones with hydrogen peroxide.219 Efficient, eco-friendly, and selective oxidation of secondary alcohols is achieved with hydrogen peroxide using aqueous hydrogen bromide as a catalyst. Other peroxides such as i-butyl hydroperoxide (TBHP), sodium... 

Epoxides from ic-diols. The reaction if secondary, primary v/c-diols with a mixture of 6 M hydrogen bromide in HOAc n suits in a vR -2-acetoxy-l-bromoalkane, which is converted into an alkyloxirane on treaiment with base. The method is suitable for preparation of chiral alkyloxiranes. 

In principle, process integration applies even more to direct synthesis of hydrogen peroxide, further improving the advantages over the anthraquinone route. Methanol can be used to replace water as the solvent and the dilute methanol solution obtained fed into the epoxidation reactor. Minimal purification may be required, for example for the removal of hydrogen bromide and other additives that may have been needed to increase the selectivity. 

In the second approach, 16-dehydropregnenolone was employed, the double bond of which at the 16,17- position was epoxidised, the epoxide cleaved with hydrogen bromide to the bromohydrin which was reduced and following formation of the 3-formoxy derivative, acetylation of the 17-hydroxy compound gave an intermediate which was oxidised by the Oppenauer reaction to give cortexolone (56) as the diacetate to which the microbiological oxidation could be applied. The process is outlined. 

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