Nitrostilbene nitrostyrene

If the nitro group is located at the ethylene fragment, one-electron transfer initiates dimerization of the developing anion-radicals. a-Nitrostilbene, w-methyl-co-nitrostyrene, and a-nitro-p-ferrocenylethylene give anion-radicals, which dimerize spontaneously. It is interesting to compare reactions of cyclooctatetraene dipotassium (C8HgK2) with a-nitro and a-cyano ferrocenylethylenes (Todres and Tsvetkova 1987, Todres and Ermekov 1989 Scheme 3.4). 

Even though the high carbon basicity of thiolate ion nucleophiles is a major reason why their nucleophilic reactivity is much higher than that of oxyanions or amines of comparable pATa, there is an added effect that comes from a reduced intrinsic barrier. For example, intrinsic rate constants for thiolate ion addition to a-nitrostilbene or p-nitrostyrene are up to 100-fold higher than for amine addition. This has been explained in terms of the soft soft interaction... 

The intrinsic rate constants for thiolate ion addition to 76-Cr and 76-W are substantially larger than those for alkoxide ion addition. This is similar to the previously mentioned higher intrinsic reactivity of thiolate ions compared to amine nucleophiles for the addition to a-nitrostilbene and p-nitrostyrene. It can be understood in terms of the soft-soft interaction of the thiolate ion with the carbene complex which is more advanced than C S bond formation at the transition state.184... 

Nitro alcohols ate usually isolated (method 102) but are sometimes dehydrated directly to olefinic nitro compounds as in the preparation of co-nitro-2-vinylthiophene from nitromethane, thiophenecarboxaldehyde, and sodium hydroxide (78% yield). Many substituted /3-nitrostyrenes have been obtained by condensation of nitromethane or nitroethane with substituted benzaldehydes. A methyl group on the benzene ring is sufficiently activated by nitro groups in the orlio or para position to cause condensation with aldehydes. A series of nitrostilbenes has been made in this way from substituted benzaldehydes. ... 

In a similar reaction, a-cyano-yS-nitrostyrene and a-acyl- S-nitrostilbene form isoxa-zoles on cathodic reduction [50]. 

In liquid solutions in the absence of a sensitizer, T-T absorption has hitherto been observed predominantly with nitro-substituted frans-arylethy-lenes (Tables 16c-e) such as nitrostilbenes [31,200], nitroazastilbenes [172,416], and nitrostyrenes [417], Apparently, the nitro group enhances strongly thioindigo dyes [418,419]. No triplet could be measured for stilbene under direct excitation conditions at room temperature [96,200] because the triplet yield is too small (see Section 1V.B.6). 

The reactivity toward singlet oxygen [238,454] should be taken into consideration if triplet states are involved (either as intermediate or as sensitizer) on irradiation of air- or oxygen-saturated solutions. Benzaldehyde, hydroperoxides, and dioxetanes have been found as products from the reaction of stilbenes with reactive oxygen species [464,465]. A rearrangement reaction has been reported for nitrostilbenes formation of a-oximinoketones, typical for / -nitrostyrenes, which may be accompanied by cleavage products [466],... 

There was further exploration of a catalytic method for reduction of nitrostyrenes to indoles. A PhClj(PPh3)j-SnClj system catalyzes cyclization with CO as the reductant. <94J0C3375> Several representative nitrostyrenes, such as 2-nitrostilbene and methyl 2-nitrocinnamate gave the expected products. 

The Cadogan-Sundberg indole synthesis, often known as the Cadogan reaction, refers to the deoxygenation of o-nitrostyrenes or o-nitrostilbenes... 

The Cadogan reaction refers to the deoxygenation of o-nitrostyrenes 1 or o-nitrostilbenes with trialkyl phosphite or trialkylphosphine and subsequent cyclization of the resulting intermediate nitrene 2 to form indoles 3. The reductive cyclization protocol has also been exploited to prepare a variety of A -containing heterocyclic compounds including carbazoles, indazoles, benzimidazole, benzotriazoles, anthranils, phenazines, phenothiazines, quinolines, and related compounds. 

Synthesis of N,N-diethanol-4 -amino-4-nitrostilbene (16). A mixture of of 4-bromo-N,N-diethanolaniline (0.872 g, 3.35 mmol), 4-nitrostyrene (0.500 g, 3.35 mmol), Pd(OAc)2 (0.0752 g, 0.335 mmol), tri-o-tolyl phosphine (0.204 g, 0.670 mmol), and Et3N (0.513 mL, 3.685 mmol) in DMF was heated in a screw tapped tube purged with argon at 90 C for 48 h. The reaction mixture was cooled, filtered, and poured into ice cold water. The organic layer was extracted with EtOAc. The organic extract was dried over MgS04 solvent removed in vacuo. Stilbene... 

A comprehensive comparison among different expressions was done by Koutek, in a remarkable paper of the late 1970s [201] on the basis of the data available for 9 compounds, viz. carbazole, indole, l,3-diphenyl-2-pyrazoline, (hexamethyl-benzene + tetrachlorophthalic anhydride) CT-complex, 4-amino-4 -nitrostilbene, 4-dimethylamino-benzonitrile, 4-dimethylamino-4 -nitrostilbene, 4-dimethylamino-co-nitrostyrene, and 4-dimethylamino-benzylidene-4 -nitroaniline. Unfortunately, the analysis was limited to neutral molecules characterised by the presence of a symmetry axis, or at least by expected co-directional electric dipole moment vectors. 

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