organic chemistry - Reduction of α,β-unsaturated nitro compounds

Would it be possible to reduce a α,β-unsaturated nitro compound to a saturated amine using for example $\ce{NaBH4}$? I know these kind of compounds will be reduced by hydrogenation using a $\ce{Pt/C}$ catalyst, $\ce{LiAlH4}$ or freshly prepared Raney Nickel, but I'm looking for a reducing agent that is easier to handle than those.

The book from which I'm learning, Clayden et al., does not really go into much detail on reduction of nitro compounds or unsaturated alkanes, other than that hydrogenation is a good approach to both and that the nitro group is one of the most easily reduceable functional groups. But how about a α,β unsaturated compounds then? How would I asses whether some reducing agent is able to reduce both simultaneously?

Answer

I'm not aware of a $\ce{NaBH4}$-based reduction of nitroalkenes to saturated amines, such as in:

It is however possible to reduce nitroalkenes to saturated hydroxylamines using $\ce{BH3*THF}$ in the presence of catalytic amounts of $\ce{NaBH4}$. (DOI)

If there's a chance to perform the desired transformation in one step via catalytic hydrogenation at normal pressure: go for it!

The handling of these reactions is nothing to be afraid of.

Typically, I performed hydrogenations in a standard 2- or 3-neck flasks and used ordinary balloons (think childrens' birthday) as gas storage. Advice: Stuff a piece of rubber tube into the inlet of the balloon and secure it with teflon tape.

• Either attach this to the glas olive of a valve attached to your flask



• or take a plastic syringe, cut off the base, stuff the the plastic cylinder into the rubber tube. Fill the balloon and attach a needle. Hydrogen may now be fed to your reaction mixture through a rubber septum cap.

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UPDATE

I still doubt that the intended reduction by $\ce{NaBH4}$ is possible.

There is however another established route from $\alpha,\beta$-unsaturated nitroalkenes to amines which is worth to be mentioned:

Condensation products of aromatic aldehydes and nitroalkenes are reduced by iron in hydrochloric (or acetic) acid to the corresponding arylalkanones.

These ketones can be converted to primary amines by reductive amination in methanol (or ethanol) in the presence of (excess) ammonia and, of course, hydrogen over Raney Nickel or Urushibara Nickel.

In the course of this reaction, the imine intermediate is in situ reduced to the desired primary amine.

The resulting amines are valuable precursors in the synthesis of natural products: Their conversion to imines or amides and subsequent Pictet-Spengler or Bischler-Napieralski cyclisations furnish tetrahydro- and 3,4-dihydroisoquinolines.