3-Nitroanisole. nucleophilic photosubstitution

Other factors, however, should also be effective. A specific influence of the solvent 101,116) added detergents 12 ) and remote electron donating substituents 119) has been observed. Steric hindrance, which certainly is of influence in the nucleophilic photosubstitution reactions of a-nitronaphthalenes, has been found to alter the reactivity of nitroanisoles... 

Nitroanisole also undergoes nucleophilic photosubstitution in an alkaline medium (pH = 12) to yield 3-nitrophenolate by hydroxylation of the methoxy substituent. The rate of the reaction is sharply reduced in the presence of p-CD. The result is in agreement with a complete protection of the molecule from reaction, owing to inaccessibility of the reactive intermediate to hydroxide [310],... 

Wubbels reported the temperatiire dependence of regioselectivity in nucleophilic photosubstitution of triplet 4-nitroanisole (151) by hydroxide ion in water giving 4-methoxyphenol (152) and 4-nitrophenol... 

Pleixats, R., Figueredo, M., Marquet, J., Moreno-Manas, M., and Cantos, A., The search for new biochemical photoprobes. II. The nucleophilic photosubstitution of 2-fluoro-4-nitroanisole, Tetrahedron, 45, 7817, 1989. 

A competition between substitution and two kinds of quenching processes, either dependent or independent on the added nucleophile, is envisaged for the photosubstitutions of p-nitroanisole (pNA) ni.ns). With cyanide ions in aqueous aerated solution pNA is transformed on irradiation into 2-cyano-4-nitroanisole in high yield ns,ii8) probably via addition of cyanide to excited pNA. 

These optimistic views received a first blow by the discovery of another category of nucleophilic aromatic photosubstitutions occurring in liquid ammonia as a solvent and nucleophile. In this medium the nitroanisoles still show the pattern that had become familiar, i.e., photosubstitution of OCH3 by NH2 with preference for reaction at the position meta with respect to the nitro-group. However, nitrobenzene, dinitrobenzenes, and nitrohalogenobenzenes... 

In the range of leaving groups, fluorine has been recognized as a valuable substituent that has practically no heavy atom effect and that in many cases is smoothly replaced under the influence of irradiation (Brasem et al., 1972). With 2-fluoro-4-nitroanisole it even proved capable of efficient substitution by the weak nucleophile water, a reaction that has not been equalled by any other substituent. Curiously, the photosubstitution of fluorine by cyanide is generally less efficient than that by other nucleophiles. 

Already, with one of the first nucleophilic aromatic photosubstitutions encountered, curious behaviour was found when studying the rate of reaction as a function of pH. m-Nitrophenyl sulphate shows no increase in the quantum yield of photohydrolysis with increase of hydroxide ion concentration up to values as high as 0-1 M. This behaviour, also found with one other compound (5-chloro-3-nitroanisole), is in clear contradistinction to what is... 

Wubbels et al. reported the temperature dependent nucleophilic aromatic photosubstitution of the Sn2 Ar type. Irradiation of 2-chloro-4-nitroanisole (122) at 25 °C in aqueous NaOH gave three substitution products 2-methoxy-5-nitrophenol (123), 2-chloro-4-nitrophenol (124), and... 

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