Catalytic reactions involving nitro compounds

Thus in this case the catalytic reaction involves the anionic -form o f the nitroalkaneI which in general undergoes reactions at the metal centre di-f-ferent than those observed with the nitro derivatives in their neutral -form (3.2.) However it is interesting to point out the similarity between the probable intermediate formed during the deoxygenation reactions o-f nitro compounds by carbon monoxide <3.2.1.), and the intermediate which should lead to the oxime in the copper-catalysed reactions ... 

The similarity between the reactions described in this last section and the ones involved in the catalytic processes discussed in this paragraph is quite close and it becomes even closer when we consider that carbonate esters have also been observed in up to 11% yield during reductive carbonylation reactions of nitro compounds catalysed by PdCb and an iron cocatalyst [74, 75]. Since carbonate esters are volatile compounds, their presence may easily escape attention and their formation is probably much more widespread than it is generally believed. 

At this point, the traditionally accepted mechanism required some re-investigation to gain some insight into the real processes involved. In recent work, - we unequivocally showed that aniline is an intermediate during the reaction. Thus any mechanistic picture not implying the intermediate reduction of the nitro compound to aniline, including all of the previously suggested reactions, cannot be of any relevance to the actual catalytic cycle. 

A catalytic system involving supported palladium and a phenantroline in equimolar ratio, has been shown to be active and selective in reductive carbonyl ation of aromatic nitro compounds to the corresponding urethanes when the reaction is conducted in anhydrous ethanol and in the presence of a catalytic amount of a weak, non ester ifiable Broensted acid [252. ... 

Nitronate salts have been shown to be oxidized to gem-dinitro-compounds by nitrite ion and persulphate in the presence of catalytic amounts of ferricyanide. gem-Cyanonitro- and a-nitro-sulphones were similarly obtained from reactions involving use of cyanide and sulphinate salts respectively. A 1,M-dinitro-compound... 

The competition between the catalytic carbonylation of organic nitro compounds and other chemical routes for the synthesis of a variety of organic compounds has not yet come to an end, but many progresses have been done in the former field. We also like to emphasize that this type of research does not only involve relevant industrial problems to be solved, but it opens a research field where the academic interests (mechanism of the reactions, isolation of the intermediates in the catalytic cycles, synthesis of model compounds and so on) can find a lot of opportunities. 

We next analyzed the role of the chloride anion. We have already mentioned that chloride has been reported to accelerate the reaction of nitrosoarenes with Ru3(CO)i2 and also to promote the formation of phenyl isocyanate from a trinu-clear imido-halide cluster. However, neither of these effects seems relevant to the effect observed in catalysis. In fact, apart from the problem of the cluster nature of the compounds involved, nitrosoarenes are always much more reactive than their nitro counterparts and the reaction of a free nitroso intermediate should be very fast relative to the other steps in the catalytic cycle, so that its further acceleration should not be influential. The promotion effect on the isocyanate-producing step, on the other hand, cannot be relevant to the catalytic cycle because it has been shown that the eorresponding imido clusters are not involved. So we must look for other effects. 

---