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Author: Subject: Reduction of substituted 2-phenylnitroethenes to 2-phenylnitroethanes with NaBH4 - Maybe the greatest way to make tar
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[*] posted on 10-11-2018 at 02:19

Quote: Originally posted by clearly_not_atara  

However, the thread linked above by laserlisa seems to indicate success at least with 4-trifluoromethyl-2,5-dimethoxynitrostyrene (although only 71% yield under ideal conditions).


The thesis includes a few more substrates. I would be interesting to see if people can reproduce these results. Perhaps the conditions can be tweaked to improve the yields further.

[Edited on 10-11-2018 by laserlisa]
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[*] posted on 1-12-2019 at 03:13

Since i've played around quite a bit with biphasic PTC reductions, e.g. toluene/water/Aliquat 336, i'd like to see if this concept can be extended to incorporate the Cu(2+) reduction step in a one-pot reaction.

The PTC/NaBH4 reduction works exceptionally well for phenyl-2-nitropropenes to phenyl-2-nitropropanes, with yields in the high 80s to 90s, but i've yet to try it out with phenyl-2-nitroethenes.

The latter substrates always carry the risk of dimerization, and that wouldn't change when working with this biphasic system, since the substrate is added as a solution in toluene and the PTC might just carry the increasing amounts of negatively charged phenyl-2-nitropropane-BH4(-) adduct to the toluene phase with the substrate instead of the decreasing amounts of BH4-.

That's where flow chemistry would come in handy - all it would take (lol) is determining the optimal amounts of each reagent injected together in a static mixer of sufficient length, then inject the effluent into a second static mixer together with an aqueous solution of Cu(2+). Inject that effluent in a third static mixer along with some acid, and drip-drip-drip, got your amine salt in the aqueous phase and unreacted organics in the toluene phase.
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