Deoxygenations hexachlorodisilane

Deoxygenation. Hexachlorodisilane is useful for deoxygenation of nitrones and various N-oxides in good yields under exceptionally mild conditions (25° or below).1 It is recommended for deoxygenation of 2,3-disubstitutcd quinoxaline 1,4-dioxides under mild conditions yet at reasonable rates.2... 

DEOXYGENATION Hexachlorodisilane. Iron pentacarbonyl. Sulfur trioxide—Pyridine. 

The successful deoxygenation of the sulfoxide 18a by either hexachlorodisilane as the reducing agent, or diiron nonacarbonyl according to the deoxygenation-complexation route can also be rationalized in terms of electrophilic attack of the reagents used on the nucleophilic sulfoxy oxygen. 

Deoxygenation of the N-oxide 194 was achieved using hexachlorodisilane in chloroform.168... 

The oxide may be deoxygenated to the starting thiatriazole, but the oxygen is released rather slowly, even with the potent deoxygenating agent hexachlorodisilane. 

Removal of an IV-oxide function utilizes the usual reagents such as zinc and acetic or hydrochloric acids, sodium borohydride, hydriodic acid, phosphoryl chloride, sodium dithionite, phosphorus trichloride or hydrogenation over Raney nickel. When l-hydroxy-2-methyl-5-phenylimidazole (262) reacts with butyllithium and hexachlorodisilane this also induces dehydroxylation (Scheme 152) (80AHC(27)24l). At times, as with other heterocyclic A-oxides, deoxygenation with phosphorus halides can introduce a halogen atom at C-2 of imidazole (75JCS(P1)275). 

Hexachlorodisilane has been found to be a convenient deoxygenating agent of amine oxides and sulfoxides, and has been used in the synthesis of condensed bridged phosphinesIn addition, the first and only stereospecific desulfurization of phosphine sulfides reported to date was also accom-... 

Deoxygenation and Desulfurization. Hexachlorodisilane has been shown to effect the stereospecific reduction of phosphine oxides to phosphines with inversion of configuration (eq 1 ), although short reaction times are required to prevent chemical racemization of the phosphine products under the reaction conditions. This protocol complements trichlorosilane which, under appropriate conditions, reduces phosphine oxides with retention of configuration. Reductions of bridged bicyclic phosphine oxides and cyclic halophospholene oxides by hexachlorodisilane have also been reported. 

In contrast to the deoxygenation of phosphine oxides by hexachlorodisilane, desulfurization of phosphine sulfides by this reagent occurs stereospecifically with retention of configuration (eq 2). ... 

Dehydroxylation occurred upon treatment of the alkoxide of a l-hydrox3umidazole derivative with hexachlorodisilane (eq 6) In the same report it was observed that nitrones are deoxygenated upon treatment with hexachlorodisilane, while C=N reduction occurs to yield hydroxylamines with trichlorosilane (eq 7). 

Oxidation of llb(5 /2/iS) with excess MCPBA gave the diastereomeric sulfones 17 (39%) and sulfone 1-N-oxides 19 (51%) that were separated by silica gel chromatography. Deprotection of 17 or 19 gave the corresponding 5 -deoxy-5 -fluoro-5 -[(4-methoxyphenyl)sulfonyl]adenosines (18) or 1-N-oxides (20). Fractional crystallization of 20 (MeOH) gave 5 -deoxy-5 (S)-fluoro-5 -[(4-methoxyphenyl)sulfonyl]adenosine-l-N-oxide [20(5 5)] with I F NMR 5 -192.85 (dd, Vf-s = 45.0 Hz, = 28.5 Hz, F(5 S)]. Hexachlorodisilane effected smooth 1-N-deoxygenation of 19 to give 17. 

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