Natural Science Forum / Chemistry / Organic Synthesis / October 2003

Fe-reduction is not nice way to make anilines from nitroaromatics, try
hydrogenation on Pd-C or even better, Raney Nickel in EtOH with
hydrazine as H2 source (hydrazine is unpleasant and has to be added
slowly - in form of diluted solution). Another alternative is SnCl2 in
acidic media (with extra HCl) or Sn/HCl. Na2S hydrate with a trace of
elementary selenium as a catalyst also works nicely. (Conditions:
aqueous solution, reflux) or Na2S2O4 (=dithionite) at 40-70C.

Also, there is a better preparation for perylene: 1-bromonaphtalene is
treated with Mg in THF, the obtained Grignard is added at low
temperature to anhydrous CuCl2 (prepared from CuCl2-hydrate by neat
SOCl2 excess at room temperature). The obtained 1,1-binaphtyl is a
nice crystalline material. Its treatment with AlCl3 produces perylene.
(Probably by air oxidation)

Hi Albert,
the problem you have is very probably due to complex formation between
ferrous ions and the diamin, which is an perfect ligand for forming
complexes. What you should do, is the removal of the iron ions from
the solution by precipitation. For example you could take hydrogen
sulfide to precipitate the iron as iron sulfide, after removing of the
prcipitate you should be able to isolate the 1,8-diamine. But at all,
reduction of a nitro compound with iron is a very ugly way to do this
reaction. It is far better to use SnCl2 or Sn in concentrated hydrogen
chloride acid. The Sn salts will precipitate as insoluable
Sn(IV)-oxide, even in acidic environment, than you could isolate the
diamin in the filrate after neutralising the acid in the filtrate, and
extracting the diamine into an organic solvent.
The use of Sn also will give a much more better yield, since the Fe
approach is sometimes accompanied by uncomplete reduction, resultion
in the formation of nitroso compounds and things like
this.............

Good luck

Hi, Albert!
Use the next procedure:

330 mL water + 350g iron dust + 15mL CH3COOH and stirr for 30 min. at 95
Celsius degree (to form (CH3COO)2Fe - the catalyst). Then introduce in
the flask 800 mL m-xylene at 95 oC.Separate, make a suspension consists
of 218g 1,8-dinitronaphtaline (it contains usually 5-10%
1,5-dinitronaphtaline)in 350 mL xylene. Add this mixture to the first
one in about 2-3 hours at 95 oC through continous stirring. Stirr
another 3 hours at 95 oC. Finally, add to the hot mixture 20g (13 mL)
NaOH 50%. Distill the water-Xylene azeotrope. Then introduce in the
flask other 850 mL xylene, warm at about 95 oC for 30 min. and allow the
iron oxides to decant (aprox. 50-60 min.). Siphon the superior organic
layer. Filter the organic mixture at 90 oC to remove traces of iron
oxides. Concentrate the extract. Cool at 30 oC and allow the mixture to
stand for 3 hours. 1,5-diaminonaphtalene will precipitate. Filter off.
Distill the xylene. Then, vacuum distill 1,8 diaminonaphtalene (m.p.
66.5 oC, b.p. 205 oC/12 mm Hg). Yield aprox. 68%.

Good Luck,
Narcis

I think to try  the reduction with Sn+HCl (conc.) because I have  ragents.
Thank you all for yours answers!

--
______________
Albert Ruggi
a.ruggi@inwind.it
www.chimicavita.cjb.net