Disilanes have been found to represent a new class of deoxygenating agents for aryl nitro compounds. Semiquantitative investigation of the effect of disilane structure on the deoxygenation of 2-nitrobiphenyl (1) at 240°, which yielded 2-aminobiphenyl (3) and carbazole (4), indicated only moderate reduction rate differences among those disilanes studied, with hexachlorodisilane (SisCle) and hexaphenyldisilane (SizPhe) being the most and least reactive, respectively. In contrast, the relative ratio of 4:3 was markedly dependent on disilane structure and varied between limits of ~70:1 and 1:35 for reduction with, respectively, cyclic 1,2-disilacyclopentene derivative 6 and SÍ2CI6. Deoxygenation of nitrobenzene (7a), o-nitrotoluene (7b), and p-nitrotoluene (7c) with hexamethyldisilane (SiaMes) gave their corresponding amines and azo coupling products, with AG1220o = 41 kcal/mol for the pseudo-first-order reduction of 7a in excess SisMes-Qualitative comparison of SisMee deoxygenation rates for 1 and 7a-c at 240°revealed that relative substrate reactivities were not in accord with expectations based on simple steric considerations. Failure of 2-nitrosobiphenyl to undergo deoxygenation by SiaMes has led to the suggestion that disilane reduction of 1 and, by extension, other nitro aromatics does not proceed in a stepwise fashion via nitroso intermediates. Mechanisms which accommodate this restriction and account for the observed stoichiometry and products are discussed in terms of possible transient nitrene species. Attempts to carry out low-temperature photochemical deoxygenation of 1 with SiaMee proved unsuccessful.
Bis(2-chloroethyl)phosphoramidic dichloride [MP(O)Cl2, M = N(CH2CH2Cl)2] has been used as the starting material for the synthesis of O-aryl phosphorodiamidates having the general structure MP(O)(NHR)OAr: 9, R = H, Ar = 4-NO2C6H4; 10, R = H, Ar = C6F5; 11, R = C6H5, Ar = C6F5; 12, R = 4-MeC6H4, Ar = C6F5; and 13, R = 4-EtOC6H4, Ar = C6F5. The phosphorodiamidic chloride precursor to 13 (14) was also isolated. Kinetics for the base-catalyzed hydrolysis of compounds 9--13 were investigated by UV and NMR methods and are considered in connection with service of these compounds as pro(phosphorodiamidic acid mustards) [MP(O)(NHR)OAr leads to MP(O)(NHR)OH] via an E1cB mechanism involving the intermediacy of a mustard-bearing metaphosphorodiimide [MP(O)=NR]. Anticancer screening tests against L1210 lymphoid leukemia in mice indicated that 9--14 are inactive; similar negative results were obtained with the KB cell culture, except in the case of 14 which was marginally active.
The reactivity of the title compounds under electron-impact conditions is comparable with their behaviour under thermolytic conditions. An unusual 1 ,1-elimination, having the characteristics of a linear cheletropic reaction, is observed for those compounds bearing suitable substituents.Zusammenfassung-Die Reaktivitat der Titelverbindungen unter ElektronenstoD ist vergleichbar mit dem thermischen Verhalten. Bei geeigneter Substitution findet eine ungewohnliche 1 .I-Eliminierung statt, die die Charakteristik einer linear cheletropen Reaktion besitzt.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.