Desulfination reaction

Scheme 20. Desulfination reactions. (A) acid-catalyzed zwitterion mechanism, (B) Se2 mechanism.

Due to their inherent polarizability, a-halo-/3-ketosulfoxides may be used as electrophilic partners in desulfination reaction to generate metal enolate. Therefore, treatment of a-halo-/3-ketosulfoxides with EtMgBr gives magnesium enolates. Trapping these reagents with various electrophiles allows the preparation of a-haloketones (equation 79, Table 10). 

Surveyed in this section are known SOg insertion and desulfination reactions. Kinetic and stereochemical results already discussed in Sections III-V, as well as the cycloaddition processes treated in Section V, have been given a cursory mention for the sake of completeness. The insertion reactions involving bonds other than M—C are omitted. Also excluded are all aspects of the chemistry of metal sulhnate complexes except sulfur dioxide insertion and desulfination. Readers interested in alternative methods of synthesis and in the physical and chemical properties of these and related compounds are referred to a recent review 128). 

The amount of Lewis acid to be used is depicted as an effective amount and a minimum limit of 0.5 mole equivalent with respect to the sulfmated compound concentration was mentioned. A wide variety of Lewis acids was mentioned to be useful for the present invention in the patent document, but only copper (II) compounds were claimed. The way in which the Lewis acid is used (either as a homogeneous or a heterogeneous phase), was reported to be irrelevant. So, it could be employed in solution in the reaction medium or insoluble as powders or on a solid support, such as alumina or a zeolite. The Lewis acid is supposed to be acting as a catalyst in the desulfination process. The temperature and pressure conditions for this reaction are substantially higher than the microbial conditions. The temperature and pressure conditions did not form part of any claim, but the document stipulates values between 50°C and 100°C, and 10 and 15psi, respectively. The quantitative effectiveness or conversion values of this reaction were not given, but it looks like it would diminish the advantages of a biocatalytic process. 

The reaction of sulfinyloxirane 130 with n-C4H9Li takes place at the sulfinyl group to afford the desulfinated epoxide 133 in good yield. This reaction proceeds at — 100°C with concomitant formation of phenyl n-butyl sulfoxide 132. Thus, oxiranyllithium 131 picks up the acidic proton of the in situ formed 132 to generate the reduce epoxide 133 (equation 46) . 

This effect cannot be explained by simply considering differences in frontier orbital energies. A useful monofluorinated dienophile has been prepared [364] using metallated difluoroenol carbamate chemistry (Eq. 143) cycloaddition occurred smoothly with a range of dienes, and desulfination could be achieved under mild conditions without loss of the fluorine atom. Wakselman and co-workers [365] synthesised a rare competent difluorinated dienophile. Lewis acid catalysed Diels-Alder reaction with furan afforded an acceptable yield of (unfortunately) unstable cycloadduct which decomposed to a phenolic product via a dehydrofluorination reaction, circumscribing its utility (Eq. 144). 

The alkyls CpMo(CO)3R (R = Me, Et, and CHaPh) readily insert SOa (57) these reactions were the subject of a kinetic study (71, 76). When R = CHaPh, the 0-sulfinato intermediate was detected spectroscopically (72, 73). Contrasting with the above behavior is the apparent lack of reactivity of CpMo(CO)3CFa (57) and CpMo(CO)3CHaCN (124) toward neat SOa- However, the dicarbonyl CpMo(CO)a(PPh3)Me does afford the corresponding >S -sulfinate, the reaction proceeding much more rapidly than that of its parent tricarbonyl, CpMo(CO)3Me (57). The photochemically induced desulfination of CpMo(CO)3S(0)a-CHaPh furnishes CpMo(CO)3CHaPh (35% yield) in contrast, irradiation of CpMo(CO)3S(0)aMe yields [CpMo(CO)3]a (57). 

The reaction of palladium(II) complexes with arenesulfinic acids or their salts to yield the organic biaryls appears to proceed by formation of palladium sulhnato compounds and their desulfination 53a). 

Electronegative substituents promote the reaction e.g., desulfination of YCgF4S02Li with HgX2 proceeds at RT . Either mono- or diorganomercurials can be obtained ... 

HC(OH)CH(HgCl)(CH2)3CH2 Reaction with R2CN2 5.7.2.3.3 C Hi.CIHgOjS cyclo-C HiiSOjHgCl Desulfination 5,7,2,3,7 C HijCljLiSi... 

A variation of the sulfinylpyruvate pathway has been reported in rat liver mitochondrial acetone powders. In this, DPN is used to support an oxidative deamination. This reaction also yields /S-sulfinylpyni-vate, which is desulfinated as described above. 

Extracts of P. vulgaris contained a cysteinesulfinic acid transaminase which, in the presence of a-ketoglutarate, converts the sulfinate to /3-sulfinylpyruvic acid. The sulfinylpyruvate, in turn, is desulfinated to pyruvate and SOs (reaction 5). The SO3" is then oxidized to S04 (reaction 6). 

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