4 -Amino-4-nitro

Ozonation of Aromatics. Aromatic ring unsaturation is attacked much slower than olefinic double bonds, but behaves as if the double bonds in the classical Kekule stmctures really do exist. Thus, benzene yields three moles of glyoxal, which can be oxidized further to glyoxyUc acid and then to oxahc acid. Substituted aromatics give mixtures of aUphatic acids. Ring substituents such as amino, nitro, and sulfonate are cleaved during ozonation. 

These are arranged alphabetically according to the atom attached to the ring carbon, halogen, nitrogen (amino, nitro, etc.), oxygen (alkoxy, aryloxy, hydroxy, phosphoryloxy, sulfonyloxy, etc.), and... 

The condensation of nitro compounds and imines, the so-called aza-Henry or nitro-Mannich reaction, has recently emerged as a powerful tool for the enantioselective synthesis of 1,2-diamines through the intermediate /3-amino nitro compounds. The method is based on the addition of a nitronate ion (a-nitro carbanion), generated from nitroalkanes, to an imine. The addition of a nitronate ion to an imine is thermodynamically disfavored, so that the presence of a protic species or a Lewis acid is required, to activate the imine and/or to quench the adduct. The acidic medium is compatible with the existence of the nitronate anion, as acetic acid and nitromethane have comparable acidities. Moreover, the products are often unstable, either for the reversibility of the addition or for the possible /3-elimination of the nitro group, and the crude products are generally reduced, avoiding purification to give the desired 1,2-diamines. Hence, the nitronate ion is an equivalent of an a-amino carbanion. 

The imidazothienopyridines can be prepared in two different ways, both starting from the same amino-nitro-thienopyridine 48. This can be treated with triethyl orthoformate in acetic acid under reductive conditions to give... 

Attempts to reduce larger quantities of the amino-nitro compound by this method usually give lower yields. For larger quantities severed reductions may be carried out simultaneously, and the filtrates may be combined for isolation of the diamine. 

In the following we will present the explicit form of the potential functions and the parameterization of most of the force fields used in molecular mechanics calculations of amino, nitro and nitroso compounds and evaluate their performance according to these criteria. 

Several force fields have been used in molecular mechanics calculations of amino, nitro and nitroso compounds. The most intensive work has been done with MM2 and, in recent years, also with MM3, probably due to the generally recognized high performance of these force fields and since they are the only ones which have undergone extensive specific parameterization for these systems, however, several other calculations are also found in the literature (see below). We therefore start with the MM2 and MM3 force fields where we briefly outline the specific form of the potential functions and discuss, in some detail, the parameterization procedure for the type of compounds discussed in this chapter. We then turn to several other force fields which have not undergone specific parameterization but were nevertheless used in the calculations (AMBER, Tripos, DREI-DING, UFF). We conclude with a brief comparison of the energetic performance of all force fields. 

No specific parameterization of AMBER for amino, nitro or nitroso compounds has been published. However, several calculations with this force field are found in the literature and are discussed in Section II.D and in Section m of this chapter. 

As in the case of DREIDING, the underlying philosophy of UFF does not allow for parameters to be developed for specific molecular systems (e.g. amino, nitro or nitroso). Rather, these are extracted from atomic parameters using a set of combination rales. Several calculations on amino and nitro compounds were performed as part of the validation of UFF58,59. In the following we refer to the structural results and save the discussion of the energetic ones to Section II.D. 

TABLE 2. Approximate range of nitrogen chemical shifts in organic molecules with amino, nitro and nitroso groups... 

III. EFFECT OF AMINO, NITRO AND NITROSO GROUPS ON THE NMR SPECTRA OF THE AROMATIC RING... 

The H-NMR spectra of amino, nitro and nitroso compounds have been reviewed16,17, and the effects of these substituents on the proton chemical shifts have been investigated16. Table 4 gives these substituent effects for mono-substituted benzenes. 

The present chapter deals with amino, nitro and nitroso groups, quaternary ammonium compounds, and with several minor related functional groups. Analytical aspects concerning these functional groups were reviewed in the past to various extents1-3. The present chapter will deal with certain general aspects and especially with advancements that took place in the last few years. 

Rearrangement reactions involving the amino, nitro and nitroso... 

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