Subject nitrene

Attempts to initiate formation of a nitrene, and its rearrangement to the iminooxo-phosphorane 80, by subjecting l-chloroamino-2,2,3,4,4-pentamethylphosphetane 1-oxide to a-elimination with sodium methoxide proved unsuccessful48). In contrast, however, the phosphorylhydroxylamides 88 rearrange in the presence of tert-butyl-amine to the heterocumulene 89 and then add base to give the phosphonic diamides 90 (>90%)49). The reaction is reminiscent of the well-known Lossen degradation. 

The intermediacy of a discrete nitrene species in these deoxygenations has been the subject of some debate. Supporting evidence comes from studies on the deoxygenation of a series of mainly m-nitroarenes in the presence of diethylamine, which reveal that the... 

The four ttutin characteristic reactions of nitrenes are summarized in Scheme 2. All of these reactions have parallels in carbene chemistry for example, a full discussion of the C—insertion reaction of car-benes is given in Volume 3, Ch ter 4.2. The first reaction, the addition to an alkene to form an aziridine, is covered in detail in Volume 7, Chapter 3.S. The C—insertion reaction, the subject of this chapter, can, in principle, occur by severid mechanisms. However nx>st of the reactions are believed to involve... 

Photolysis of phenyl and o-trifluoromethylphenyl azide in solid matrices led to the triplet nitrene as detected by e.s.r. The actual processes involved in aromatic azide photolyses have been the subject of much studyThe electronic spectra of the nitrenes were measured by photolysis of a number of aryl azides in organic matrices at 77°K . These species were stable indefinitely at this temperature, no change being observed in the spectra for hours. The photolysis of diazides at 77°K, whether conjugated (e.g. / -diazido-benzene) or not [e.g. bis (j6-azidophenyl) methane] proceeded in two distinct steps to the dinitrene. The second step was about two to three times as efficient as the first ( 2/ 1 2-3)... 

The subject matter of the present article has been discussed with varying degrees of completeness in reviews on the general reactions of organic azides and on nitrenes . ... 

The l,6,6a-l -trithiapentalene system (178) reacts with ethoxycarbonyl-nitrene to give, after ring expansion, the little-known 1,3,2-dithiazine derivative (181) (Scheme 20) <83CJCli6i>. The mechanism is believed to proceed by attack of the nitrene at the nucleophilic S position to give intermediate (179) which then is subject to insertion of the nitrogen into the S,—Sea bond. The final product is obtained after cleavage of the Se—Sea bond in (180). 

Force-field calculations have shown that when there is a spacer between the two phenyl rings, such as in (2-nitrophenyl) phenyl thioether and 2-nitrobenzophenone, the distances between the nitrene nitrogen and the ortho carbon, where cyclization should occur in the hypothetical imido clusters, are much longer than in compound This explains why these substrates afforded the corresponding amines, with only trace amounts of the desired six-membered heterocycles being observable, when subjected to reaction conditions the same as those used for Eq. (12). ... 

The initial product of elimination is a highly electron-deficient species, usually a carbene or a nitrene, which subsequently reacts rapidly to give products. The base-catalysed hydrolysis of chloroform is an alpha-elimination . The properties of the electron-deficient species represent a rapidly expanding field of organic chemistry and this subject is discussed in the following chapter. In this chapter, only apparent alpha-eliminations, (e.g. reaction (5)), are included. The nature of the products indicates the intermediacy of electron-deficient species, but kinetic studies show the processes occur via reactions of the precursor carbanions, viz. 

The tetrazoles family of compounds represents an important source of nitrenes, carbenes and ylides when subjected to UV irradiation. Baskir et isolated 5-amino- and 5-(dimethyl)amino-2-methyl-... 

Addition of Carbene and Carbenoids to Olefins.—The addition of carbenes and carbenoids to olefins continues to be one of the most popular routes used for cyclopropane synthesis. A review of carbenes (and nitrenes) based on the 1973 literature has appeared during the year, and methoxycarbonyl carbene has been the subject of a theoretical study. ... 

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