New nitroalkene reduction with NaBH4 / Cu(OAc)2

[Rhodium]

A saturated aqueous solution of Cu(OAc)2 (containing some solid) (1ml) was added to a solution of the nitroalkene (0.22 mmol) in 5ml MeOH. Small portions of NaBH4 (0.090g) were added with stirring at room temp over 2h. Then 10ml ethyl acetate was added. The reaction mixture was washed with aqueous NaHCO3. The aqueous layer was further extracted with ethyl acetate and the combined organic layers were dried over Na2SO4, filtered and vaporated. Column chromatography afforded the phenethylamine in 60% yield.

Chem Pharm Bull 44(11) 2165-2168 (1996)

[Dr_Sister]

that's cuprous acetate? the same stuff you get disolving pennies in GAA? or is that the cupric stuff we don't want here.
7.10.01

[Rhodium]

That is the acetate gotten from dissolving pennies, yes. Copper(II)acetate. I think it would be easier to digest copper metal with a stronger acid (like nitric or sulfuric) first, and then crash out the Cu(II) ions as copper carbonate by adding soda, filter and dry, and then dissolving the copper carbonate in acetic acid, giving copper(II)acetate and carbon dioxide.

The only "catch" is that the nitrostyrene they reduced in the article was incorporated in a larger steroid molecule, but it was still a nitrostryrene with a lots of add-ons. I just can't find a reason why it wouldn't work just as good with simple nitrostyrenes like those we so often use here at the board. Many other transition metals are known to catalyze NaBH4 reductions very well, like cobalt and nickel for example.

[Dr_Sister]

or just start with the carbonate from the pottery supply house  thanks Rhod, sometimes its hard to see the forest for all the damn trees
7.10.01

[Barium]

Which nitroalkene did they try this with? What kind of ring-substituents would tolerate this reduction system?
Catalytic hydrogenation freak

[Rhodium]

I don't remember exactly, but it was one standard steroid, with a nitro group conjugated with one of the double bonds. Not much functional groups.

[starlight]

Found this a couple of weeks ago. May help further:

reduction of organic compounds with sodium borhydride-copper (II) sulfate system.  Yoo, Sung Eun, Sang Hee. Korea Res. Inst. Chem. Technol., Chungnam, S.Korea. Synlett (1990), (7), 419-20. Journal Written in English.

Abstract
The reduction of various functional groups was investigated using sodium borohydride-copper (II) sulfate. Ketones, aliph. esters, olefins, nitriles and aliphatic and aromatic nitro groups were reduced, but amides and aliphatic and aromatic carboxylic acids were inert. The rate of reaction was different for the various functional groups, allowing selective reductions to be performed.

[moo]

In Chem. Pharm. Bull. 44(11) 2165-2168 (1996) 2-nitroacronycine is reduced to 2-amino-1,2-dihydroacronycine.

[Rhodium]

Starlight: I must unfortunately warn for that Synlett article, as it seems to be entirely made up. A group of french chemists published an article in Synlett 791-2 (1993), where they pull everything said in the 1990 article apart, saying that nothing could be reproduced - the solubility of CuSO₄ is actually too low to make the stock solution described by them. They finally conclude that by instead using Cu(OAc)₄ and running the reaction strictly anhydrous, the yields go up from 12% to 99% in the reduction of nitrobenzene to aniline.

Tet. Lett. 27(10), 1205-8 (1986) also discusses the Cu²⁺/BH₄^- reducing system, here for reducing phenyl-2-nitropropanes to amphetamines.

[starlight]

its great that there are people here with the depth of knowledge to save bees from wasting hours reading and experimenting to no avail.