Nitrophenoxy group

The stereochemistries of the reactions between 0-aryl 0-methyl phosphonochloridothioates and nucleophiles have been studied in relation to the synthesis of 1,3,2-oxazaphospholidines. No displacement of chlorine takes place on treatment of O-methyl 0-4-nitrophenyl phosphonochloridothioate with 2-methoxyethanol, and in the presence of 1-phenylethylamine, it is only the latter which reacts. In addition, when the same phosphonochloridothioate is treated with sodium ethoxide, it is the 4-nitrophenoxy group, rather than chlorine, which is displaced. Both displacements were shown to occur with inversion of configuration at phosphorus. The use of such an acid chloride as a two-step 1cyclophosphorylating1 agent of 2-aminoalcohols to give 1,3,2-oxazaphospholidines (209), is illustrated. ... 

The question of whether the reaction proceeds through an intermediate or whether it is a concerted displacement such as has been demonstrated by Ba-Saif and Williams41 for the displacement of the / -nitrophenoxy group from ester 2 (18d) by... 

The tautomerism of hydroxythiophenes has been discussed in Section 3.01.6. In nucleophilic substitution reactions the p-nitrophenoxy group has been extensively investigated as a leaving group in order to give a unified picture, details of such studies have been included in Section 3.14.3.8. 

A conclusion can therefore be reached that electronic effects are not important in the rate of hydrolysis of acetals, but this is valid only if these compounds hydrolyze in their ground state conformation. The reality could well be completely different. For instance, an acetal could prefer to hydrolyze with stereoelectronic control via a higher energy conformation. Thus, the hydrolysis of 127 and 128 could occur with stereoelectronic control at a more or less competitive rate. Compound 127 would hydrolyze via its ground state conformation whereas 128 would hydrolyze via the boat conformation 129. This situation is possible because the enthalpy of activation for the cleavage of the 4-nitrophenoxy group in 127 and 128 is close to 25 kcal/mol, a much greater value than the barrier for the formation of the boat conformation 129 which is of the order of 10 kcal/mol (94). Therefore, 129 could lie on the reaction coordinates. 

The incorporation of p-cyanophenoxy and p-nitrophenoxy groups into PHAs synthesized by P. putida and P. oleovorans has also been reported (Kim et al. 1995a). However, the extent of the incorporation of these functional groups into PHA was significantly lower than the incorporations reported for other aromatic groups, and always required that octanoic acid be cofed to the culture. 

The p-nitrophenoxy group reacts readily with compounds that contain an aliphatic amino group, with the formation of an amide bond. The reaction may be easily detected spectrophotometrically in the UV... 

---