Sciencemadness Discussion Board

sulfone removal with RaNi

Sandmeyer - 23-8-2005 at 12:11

Is it possible to remove sulfur derivatives at higher oxidation state i.e sulfones (and sulfoxides) directly with Raney nickel in the same way as thioethers can be removed?

Like in this simple illustrative example:
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Ethyl 2-methylindole-5-carboxylate. A solution of 10.0 g. (0.0402 mole) of ethyl 2-methyl-3-methylthioindole-5-carboxylate in 300 ml. of absolute ethanol is placed in a 500-ml., three-necked, round-bottomed flask fitted with a mechanical stirrer. An excess (15 teaspoons), of freshly washed W-2 Raney nickel is added, and the mixture is stirred for one hour. Stirring is then stopped, the liquid phase is decanted, and the catalyst is washed twice by stirring for 15 minutes with 100-ml. portions of absolute ethanol and decanting the solvent. The combined ethanolic solutions are concentrated on a rotary evaporator. The residual solid is dissolved in 150 ml. of warm dichloromethane, dried over anhydrous magnesium sulfate, and filtered; the drying agent is washed with 40 ml. of dichloromethane. Concentration of the combined filtrates with a rotary evaporator gives 7.5–8.1 g. (93–99%) of ethyl 2-methylindole-5-carboxylate, m.p. 140.5–142.0°C
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Now suppose the starting material in the above synthesis was not a simple thioether but rather a sulfone or sulfoxide. The question is would it be possible to apply RaNi removal of these groups exactly as described above?

Now, of course, the reductive fission by aluminium amlagam can do this - and is indeed extensivly described in the literture, but I couldn't find any raney nickel procedure for the higher oxidation states. I would avoid Al/Hg as much as I can and using Raney nickel for this is so fantasticly easy, quantitative yilding - and gives such an simple workup.

Thanks for the tips!

[Edited on 23-8-2005 by Sandmeyer]

solo - 23-8-2005 at 12:54

In my recent down time from my computer I visited some of my texts and found some interesting information as I was reading about Hydrogenation.........solo

Reduction In Organic Chemistry-Hudlicky

.........page 10

In the reduction via catalytic Hydrogenation there is a discussion of about efficiency of increase and decrease of catalytic activity, for example there is a bit about using Raney nickel to remove the sulfur in some product that one might want to hydrogenate and want to avoid the sulfur poisoning that nulls the effect of Palladium .

[Edited on 23-8-2005 by solo]