Stilbenes nitro

Nitro derivatives of bibenzyl and stiibcnc Nitre derivatives of bibenzyl Nitro derivatives of stilbene Nitro derivatives of aromatic aza pentalenes Nona... 

In contrast to other furoxans, the cycloreversion of 3,4-dinitrofuroxan to nitro-formonitrile oxide was observed even at room temperature. The nitrile oxide could be trapped in situ with electron-deficient nitriles (Scheme 149) (95MC231). Attempts to obtain cyclo adducts with styrene, phenylacetylene, rran.s-stilbene, and cyclohexene failed. 

Sodium i-nitro-2-naphtholate, 13, 78 Sodium perbenzoate, 13, 86 Sodium succinate, 12, 72 Sodium sulfide, 12, 68, 76 16, 72 Soxhlet extractor, 16, 69 17, 74 Stannic chloride, 18,1 Stannous chloride, 17, 10, 11 Steam distillation, rapid, 17, 20 Stilbene, 17, 90... 

The next stage in the process, the reduction of the nitro-groups on the stilbene to amines, which had been developed many years previously, used old iron and water reduction technology, which resulted in significant... 

Synthesis of the amino-triazole derivative (43) was performed in the authors laboratory by Pati et al. [52] (Scheme 7). Substituted benzyl bromide was reacted with triphenylphosphine to produce the phosphonium bromide starting material, 44. The Wittig reagent, obtained by treatment with sodium hydride, was reacted with 3,4,5-trimethoxybenzaldehyde 18 to generate the nitro-stilbene 45 in good yields. The alkyne 46 was obtained by bromination of the stilbene, followed by didehydrobromination. Compound 46 was then reacted under thermal conditions with benzyl azides... 

The effects of nitro substituents on the cis-trans isomerization of stilbenes has been reviewed70 (equation 63). The trans-to-cis isomerization occurs from a triplet excited state, whereas the reverse cis-to-trans isomerization occurs through a main route which bypasses the triplet state. A nitro substituent usually causes a significant enhancement of the quantum yield of the intersystem crossing. Nitro substituent effects on the photoisomerization of trans-styrylnaphthalene71 (equation 64), trans-azobenzenes72 and 4-nitrodiphenylazomethines73 (equation 65) have been studied for their mechanisms. 

Titanium ions can also he used as redox catalysts for the indirect cathodic reduction of nitro compounds (417). The electroreduction is carried out in an H20-H2S04/Ti(S04)2-(Pb/Cu) system at 45 80°C under 5 20Am . Nitrobenzene, dinitrobenzene, nitrotoluene, 2,4-dinitrotoluene, 2-nitro-m-xylene, nitro-phenol, 2,4-dinitrophenol, nitrophenetole, o-nitroanisole, 4-nitrochlorotoluene, ni-trobenzenesulfonic acid, and 4,4 -dinitro-stilbene-2,2 -disulfonic acid can all be reduced by this procedure to the corresponding amino compounds (418) in good yields (Scheme 146) [513-516]. Tin... 

Nitro substituted stilbenes have been used as models in stUbene cis trans-isomerization studies. It had been reported previously, that cis -v benzene solution, and a photostationary state of 99.5% trans isomer had been reached 132) ... 

Laser flash photolysis (30 ns, 50 mj, 347 nm) of 4-nitrostilbene, 4,4 -dinitro-stilbene, 4-nitro-4 -methoxystilbene and 4-dimethyl-amino-4 -nitrostilbene permits the observation of transients 133) por the latter two compounds, the lifetime and the absorption spectra of the transients vary strongly with the polarity of the solvent used. First order decay rate constants are given in Table 4. 

The photocyclization has been found not to occur with stilbenes substituted with acetyl, dimethylamino, or nitro groups, lodo substituents are replaced by hydrogen by photolysis in cyclohexane solution. w-Substituted stilbenes give mixtures of 2- and 4-substituted phenanthrenes which generally are difficult to separate. 

Reaction of the TMS-nitro compound 1496 and the indole carboxaldehyde 1497 with a catalytic amount of TBAF led to the desired alcohol 1498, which, on further treatment with TFAA, followed by elimination of the corresponding trifluoroacetate with DBU, afforded the frans-stilbene 1499. Reductive cyclization of 1499 under Cadogan-Sundberg conditions afforded the bisindole 1500. Finally, condensation of 1500 with (dimethylamino)acetaldehyde diethyl acetal led to tjipanazole D (359) in 71% yield (796) (Scheme 5.255). 

Cohare and co-workers reported that aristolactam BU (22) was prepared, following Kupchen s method, by Perkin condensation of 6-bromo-3,4-di-methoxy phenyl acetic acid (119) and o-nitrobenzaldehyde (120) (Scheme 14). The 2-bromo-4,5-dimethoxy-2 -nitro-ds-stilbene-a-carboxylic acid (121) was obtained. The nitro group of 121 was reduced with ferrous sulfate and ammonium hydroxide, and the resulting 2-bromo-4,5-dimethoxy-2 -amino-cw-stilbene-a-carboxylic acid (122) without purification was submitted to the Pschorr phenanthrene synthesis to yield l-bromo-3,4-dimethoxyphen-anthrene-lO-carboxylic acid (123). The phenanthrylamine 124 was prepared from 123 via a Schmidt reaction, and, by treatment with n-butyllithium and CO2, 124, afforded 22 (42). 

Dinitro-p-azostilbene or Azobis (3-nitro stilbene, called in Ref 2 3,3,-Dinitro-4/4 -distyryl-azobenzene, CjHg-CHiCH--QHsfNO NrN-QH NOJ-CHiCH-QH, carmine-red crysts mp 260-1°. Prepn and props are given in Ref 2... 

Groups of reportedly photochromic systems which deserve further study include (a) disulfoxides (123,124), (b) hydrazones (125-129), (c) osazones (130-133), (d ) semicarbazones (134-143), (e) stilbene derivatives (144), (/) succinic anhydrides (145-148), and (g) various dyes (149,150). A number of individual compounds also remain unclassified as to their mechanism of photochromic activity. These include o-nitro-benzylidine isonicotinic acid hydrazide (151), 2,3-epoxy-2-ethyl-3-phenyl-1-indanone (152), p-diethyl- and p-dimethyl-aminophenyli-minocamphor (153), brucine salts of bromo- and chloro-nitromethionic acid (154), diphenacyldiphenylmethane (155,156), 2,4,4,6-tetraphenyl-1,4,-dihydropyridine (155,156), 2,4,4,6-3,5-dibenzoyltetrahydropyran (155,156), o-nitrobenzylidenedesoxybenzoin (157), p-nitrobenzylidene-desoxybenzoin (157), N-(3-pyridyl)sydnone (158,159), tetrabenzoyl-ethylene (160), and the oxidation product of 2,4,5-triphenylimidazole (161,162). 

Dinitro-p-azostilbene or Azobis-(9-nitrostilbene, called in Beil Bis-[4 -nitro-stilbenyl-(4)]-diimid or [4 -Nitro-stilben]-<4azo4>-[4,-nitro- stilben], (OjN KAf- CH CH— C6H4-N N-C6H4-CH CH-CsH4(N01) yel-red Crystspmp 263°. It is listed in Beil 16, 84 without reference to its source was not found in CA through 1956... 

Several organometallic moieties serving as acceptors and donors have been evaluated. Molecular crystals of stilbenes have been shown to be unusually active in second harmonic generation. The linear and nonlinear optical properties of 3-methyl-4-methoxy-4 -nitro-stilbene (MMONS) single crystals will be presented. 

An interesting observation is that the differences between the nitro and sulfonyl electron accepting properties have less of an impact on the nonlinearity for the more highly conjugated stilbene compounds than they do in the case of the aniline systems. A similar effect also can also be seen in substituted polyenes. The calculated results for /3Z of A-(CH=CH2)n-NH2 (A = N02, S02CH3) are shown in Figure 2 as a... 

The theoretical models discussed above indicate that the sulfonyl group, although slightly weaker in electron acceptor strength, is indeed a viable alternative to the nitro group. In particular, sulfonyl derivatives of stilbene and azobenzene display large molecular hyperpolarizabilities and can be used as bifunctional chromophores for the construction of materials with nonlinear optical properties. 

The optical spectra of the stilbene and azobenzene derivatives were studied in different solvents to establish the solvatochromic shifts of the new sulfonyl-containing chromophores, and to compare them to those found for the nitro analogues. Figure 3 shows the spectra in toluene and in DMF of 4-dibutylamino-4 -nitrostilbene, and of 4-dibutylamino-4 -methylsulfonylstilbene, and Figure 4 shows the spectra in the same solvents, but of 4-dibutylamino-4 -nitroazobenzene, and 4-dibutylamino-4 -methylsulfonylazobenzene. Table II summarizes the results. 

The most important feature of the spectra is the large blue shift of the sulfones vs the nitro derivatives, i.e., 53 nm (3098 cm 1) for the stilbene, and 30 nm (1400 cm 1) for the azobenzene derivatives, in toluene). These large blue shifts suggest that sulfonyl compounds are more transparent in the visible region than their nitro... 

If we compare AX values (AX - XDMSO - Xj0iuene) for the four dyes under study we get 35 nm (1428 cm 1), and 27 nm (1269 cm 1), for the nitro, and methylsulfonyl azobenzene derivatives, respectively, and 22 nm (1077 cm 1), and 7 nm (457 cm1), for the nitro, and methylsulfonyl stilbene derivatives, respectively. Further examination reveals that the difference in AX between the two stilbene derivatives is 15 nm (620 cm 1), while that in the case of the azobenzene derivatives is 8 nm (159 cm1). Thus, two interesting conclusions can be drawn from this data a) the bathochromic shift is not only a function of the donor and acceptor groups, but also of the intermediate -system between them and (b) while the measured hyperpolarizability coefficients for the stilbene and azobenzene sulfonyl derivatives are very similar (see below), their solvatochromism behavior is different, and therefore solvatochromism is not an accurate prediction of p. 

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