to the solvent used this reaction as regards the first process route v 0 2 is described in particular in the publication by k g piney which appeared in bioorg med chem 8 2000 2417 2425 2 methoxy 5 2 3 4 5 trimethoxyphenyl vinyl nitrobenzene is reduced according to the improved process of the invention by the action of iron it is advantageous to use an amount of iron in excess if complete conversion of the starting material is desired this excess is advantageously greater than 2 equivalents per one mol of starting nitro derivative it has been shown that the same stage carried out in the presence of zinc in acetic acid a conventional solvent for reductions with zinc does not make it possible to obtain complete reaction in u s pat no 5 525 632 the yield of the reduction carried out on the pure z isomer varies between 46 and 66 and moreover that the amounts of zinc used are large and consequently result in considerable industrial waste furthermore the process generates a large amount of u201c azo u201d compound resulting from coupling between the amino formed and the nitroso intermediate in the reduction reduction with nascent hydrogen generated by ammonium formate in the presence of a conventional catalyst such as palladium or platinum leads to.