I am working on reducing an aromatic nitro group to amine and have tried SnCl2 and Fe systems without much luck. There are literature examples of this compound being reduced by H2 gas with Pd/C and a related compound being reduced with formic acid and Pd/C, all at room temperature or 0 C, with the formic acid reactions conducted open air.
I have wet Pd/C catalyst and have tried a variety of set-ups with ammonium formate and formic acid (no H2 gas for me) and have never gotten product, though I have gotten what by TLC appear to be the nitroso and hydroxyl-amine forms potentially. I have noticed that upon addition of catalyst or hydrogen donor to my stirring mixture I see no bubbles produced.
I understand that the catalyst should be more than happy to convert formic acid into CO2 and H2 regardless of the nitro substrate. Is there a way to check if my catalyst is inactive, or am I missing some necessary activation step since I do not seem to be seeing CO2 production?
Thanks
Update:
Thanks for the ideas everyone. I'll try transfer hydrogenation one more time with a new (hopefully more active) catalyst. If that fails I'll give iron and ammonium chloride a shot.
Final update: I think it was bad catalyst. I added double what I normally would and set-up oxygen free and saw moderate bubbling through a bubbler and saw substrate converted all the way to arylamine product.
You may wish to try Fe and NH4Cl in refluxing ethanol/water reaction system instead, this works best for me to reduce nitro groups and the workup is simple. Since you already have Fe (powder form works best), the rest of the reagents should be easily available.
Iron-Ammonium Chloride - A Convenient and Inexpensive Reductant
Krishnamurthy Ramadas & Natarajan Srinivasan
Synthetic communications 1992, 22, 3189
http://www.tandfonline.com/doi/abs/10.1080/00397919208021132?journalCode=lsyc20
For your question, I don't think it will be so easy to see the gas being released unless a substantial amount of formic acid/formate salt is being used, especially the H2 which is most likely going to be adsorped on the catalyst.
Dear Terence,
I have very awful experience with reduction of aromatic nitro groups.With a lot off published procedures I do not successfully reduce nitro group, prcedures give couple product, hard and complicated work up, dirtily reaction and another.... Now, I was used SnCl2, Fe/HCl, Fe/NH4Cl, Fe/HCOONH4, NiCl2/NaBH4 and with a lot off another I did not reduce nitro group.One advise, do not used this system for reduction nitro group.
I am reduce with Pd/H2 with 1 mol% od iodine.
Best,
Nenad
The Fe and NH4Cl in THF and water or as mentioned above Ethanol/water at reflux condition is the best way to reduce nitro group to Amine. Even i tried for the molecule which having two nitro group. Its very simplest way to reduce nitro to amine.
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