Nitro Substituted Derivatives

Naphthalene-1,8-dicarboxylic add, its nitro-substituted derivatives, and naphthalene-1,4,5,8 tetracarboxylic acid, on treatment with sulfur tetrafluoride at 0 C, undergo dehydration to form quantitatively the corresponding anhydrides [218, 221] Unsubstituted and mononitrated monoanhydndes react further at 200-250 °C to give derivatives of 1,1,3,3-tetrafluoro-l// naphtho[I,8 c,d]pyran Dinitronaphthalene-l,8-di-carboxyhc acid anhydndes and naphthalene 1,4,5,8 tetracarboxylic acid dianhydnde give the respective tetra- and octafluoroethers only in the presence of an excess of anhydrous hydrogen fluoride [221] (equabons 113 and 114)... 

The behavior of the chloropyridines and their nitro-substituted derivatives is apparently similar, the 2-chloro compounds having less tendency to show autocatalytic behavior than the 4-chloro analogues with a given nucleophile. For 4-chloropyridines the reaction may be further complicated by self-quaternization. ... 

This magnetic behavior is very sensitive to the chemical structure of the spin carrier and to the crystal packing. For instance, for the para-nitro substituted derivative, Nit(p-NO )Ph, which crystallizes in four different phases, the p phase only orders ferromagnetically (Tc = 0.6 K) [8,9], Moreover, attaching the nitro group in the meta-, rather than the / ara-position of the phenyl, leads to an antiferromagnetic compound [2],... 

Afterward, analogous intermediates have been isolated by several authors in the nitration of other furan derivatives bearing electron-withdrawing substituents.119 120 Michels and Hayes119 studied the kinetics of the conversion of the addition intermediate into the final nitro-substituted derivative by the action of several bases. 

The results show that all the 6-substituted 3-formylchromones, and the 6-nitro-substituted derivative FC5, exhibit a more potent cytotoxicity against tumor cell lines than the parent 3-formylchromone (FC1). However, there was no clear-cut correlation between the chemical structure of the com-... 

The subsequent effects found in this series are very similar to those previously reported.28 In particular, electron-donor groups (e.g., CH30) at C8 increase the photostabihty of C6 nitro-substituted derivatives (216 vs. 217, Table 17). For C8 nitro derivatives (223-230), CH30 and CH3 at C5 decrease photodegradation (224 vs. 223 and 226 vs.227). In general, dilute solutions of these spiropyrans have a better colorability and a poorer photostability (Figure 18). 

All these spectral data are consistent with a delocalized rt-electron system for the merocyanine-like open form. In particular, for the thoroughly studied nitro-substituted derivatives, it appears that the closed forms convert, under UV light irradiation, to highly conjugated open forms. In these structures, the n electrons are principally delocalized along the dimethinic chain, with probably an involvement of the nitro substituent, in accordance with a zwitterionic form like that shown in Scheme 2 for the benzothiazoline photomerocyanine (Mero.). 

TABLE XXVIII. 3-Pyrazolin-5-ones. Nitroso and Nitro Substituted Derivatives... 

It was also found by H-NMR spectroscopy that the phenyl ring in arylidenebarbiturates (5) is twisted in relation to the plane of the ylidenebarbi-turate.114115 A detailed analysis of chemical shifts of particular aromatic protons and their coupling constants with the vinyl proton leads to the conclusion that the value of the dihedral angle 6 (Fig. 9) depends on the nature and position of substitution in the aromatic ring. Ortho substitution in the phenyl ring, where steric effects predominate, results in hindrance to rotation. Thus of the two possible conformations conformer A (Fig. 10) is favored. Moreover, for o-nitro substituted derivative 5 the dihedral angle is 43°.115... 

One might expect that a phosphorus reagent having for R an aryl group activated for bimolecular nucleophilic substitution (68) by electron- withdrawing substituents might participate in a Michaelis-Arbuzov reaction. Kamai and Koshkina (159), who prepared a number of chloro-and nitro-substituted derivatives of triphenyl phosphite, found this to be the case for both ortho and para isomers of tris(monochlorophenyl) phosphite, which reacted with alkyl halides to furnish phosphonates. On the other hand, tris(2,4,6-trichlorophenyl) phosphite and tris(2,4-dichlorophenyl) phosphite (155) gave only complexes with methyl iodide however, lower reaction temperatures were employed. 

Another class of merocyanines consists of ring-opened spiropyrans, such as spiro[2H-l-benzopyran-2,2 -indolines] (BIPS), especially of 6-nitro-substituted derivatives (NOjBIPS). The photochromism of spiro... 

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