Alkenes Sodium dithionite

Viologen salts act as one-electron phase-transfer agents and, in conjunction with sodium dithionite which regenerates the bipyridinium radical cation, they have been used for the debromination of 1,2-dibromoalkanes to yield alkenes in variable yields [13-15]. Nitroarenes are reduced to anilines in high yield (>90%) under similar conditions [16], whereas conjugated nitroalkenes are converted into the oximes of the saturated ketones [17] saturated aliphatic nitro compounds are not reduced by this process. 

More recently, methods based on the use of mild reductants, able to transfer a single electron to the polyhaloalkyl halide, have been described. Various metals or their derivatives have been employed ruthenium, platinum and their complexes in low oxidation state, iron" and its carbonyl complexes, or tetrakis(triphenylphosphane)palladium. Sodium arcncsul-finate, sodium dithionite" and various oxidants have also been used. Other examples of polyhaloalkyl halide additions to simple alkenes are summarized in Table 1. Typical examples are the formation of diiodide 6, chloro iodide 7, and iodo steroid 8. ... 

Julia and co-workers reported on the highly stereoselective reductions of ( )- and (Z)-alkenyl phenyl sulfones 11 into alkenes 14 by sodium dithionite (Na2S204) in aqueous 7V,7V-dimethylformamide (OMF). " The mechanism of this reaction (Scheme 22.4) implies the conjugate addition of HSOj (resulting from Na2S204 + H2O NaHSChT NaHSOs), which behaves like or other... 

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