Oxygen from solvents

The present procedure affords a simple and general method for preparing bromohydrins from alkenes which avoids the heterogeneous solvent systems often used in such reactions. Labeling experiments have demonstrated that the oxygen from the dimethyl sulfoxide appears in the hydroxyl group of the bromohy-drin. Therefore the role of the water is to hydrolyze the intermediate /3-bromodimethylsulfoxonium ion. 

The asymmetric unit contains one [Cun(hfac)2(TTF—CH=CH—py)2]+ radical cation and one PFfi anion both in special positions, as well as one dichloromethane solvent molecule in the general position. The Cu11 ion lies in a distorted octahedral coordination, two oxygen from two hfac ions and two nitrogen from TTF CH=CH py are trans to each other and form the square plane (Cu-N bond length of 2.016(5) A) the two reminiscent oxygen atoms from the two hfac ions occupy the apical positions. 

Oxygen-containing solvents with a strong coordinating ability, such as diethyl ether, methyl /.so-butyl ketone and /.so-amyl acetate, form oxonium cations with protons under strongly acidic conditions, e.g. (R20) H. Metals which form anionic complexes in strong acid can be extracted as ion pairs into such solvents. For example, Fe(III) is extracted from 7 M hydrochloric acid into diethyl ether as the ion pair... 

Since S03/H2S04 is clearly not the most desirable system for industrial applications, a formidable challenge is to find an oxidant that oxidizes Pt(II) much faster than S03 does, operates in an environmentally friendly solvent, and can be (like SVI/SIV) reoxidized by oxygen from air. Ideally, the reduced oxidant would get reoxidized in a continuous process, such that the oxidant acts as a redox mediator. In addition, the redox behavior has to be tuned such that the platinum(II) alkyl intermediate would be oxidized but the platinum(II) catalyst would not be completely oxidized. Such a system that efficiently transfers oxidation equivalents from oxygen to Pt(II) would be highly desirable. A redox mediator system based on heteropolyacids has been reported for the Pt-catalyzed oxidation of C-H bonds by 02, using Na8HPMo6V6O40... 

In an acidic medium there will be an equilibrium set up such that any one of the three oxygen atoms may be protonated they all have the same or similar basicities. The equilibrium will involve loss of proton to the solvent, followed by reprotonation of another oxygen from the solvent. This equilibrium will then be disturbed as one of the protonated species is removed by further reaction. We shall meet this... 

I OH2 HsC OH OEt an equilibrium loss of proton to solvent, then reprotonation from solvent the molecule may have any one of the three oxygens protonated... 

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