Any one here knows how to do the Zinc\HCl reduction of NS with good yield ?

[Bennychairman]

i know that some how this reaction can have good yield ...
my friend in Taiwan manages the reaction with 60%+ yield almost half assing it while i manage to get 20-30% max ...

as i understand the reduction has multiple steps and first the nitro group is reduced , then the double bond , but according to the ZINC\HCL paper the enamine goes trough the imine to reduce to amine , and i really dont manage to get how to make it reduce to its full potential , my friend really doesnt know how to explain more and just says "he does the reaction on a hunch".

i add the zinc within 1 hour to 1:2 ipa\hcl solution , while maintaining 5C , some times the reaction gets cold at the end because it stops generating heat , maybe it slows the conversion ? , or i also read the if the zinc you use is little oxidized it can ruin the reaction (altho its might was refereed to halogenated NS )

the nitro group is reduced i am almost sure as the color changes to transparent greyish solution but upon work up and evaporation it seems the yield is very low and for some reason the conversion to amine isnt complete

i know i also can do the reduction with nabh4\cucl2 (and i plan to try it also soon)
but for now if anyone knows anything for this novel reduction it might really help

does any one here manages the reaction and knows the key points ?
i added the paper for reference as it had proposed mechanism of action

 

[Mclssmxxl]

I don’t know this reaction personally but from what you are describing maybe you can try less cooling? Do a micro synth and see what happens with temperatures increased a little.