Sandmeyer
National Hazard
Posts: 784
Registered: 9-1-2005
Location: Internet
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Mood: abbastanza bene
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sulfone removal with RaNi
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
___ __ _
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]
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solo
International Hazard
Posts: 3975
Registered: 9-12-2002
Location: Estados Unidos de La Republica Mexicana
Member Is Offline
Mood: ....getting old and drowning in a sea of knowledge
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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]
It's better to die on your feet, than live on your knees....Emiliano Zapata.
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