Bistrifluoromethyl nitroxide

Bistrifluoromethyl nitroxide, (CF3)2NO, is a stable purple gas and is of particular interest because, of course, nitroxides are stable free radicals. The nitroxide is prepared from bistrifluoromethylhydroxylamine [283] by reaction with, for example, silver oxide [284] (Figure 8.111) or potassium permanganate [285]. 

Photochemical chlorination of perfluorobenzene [170] and perfluoropyridine [171], and reactions with bistrifluoromethyl nitroxide [171], give addition products, although the C=N bond is very resistant to radical attack (Figure 9.71). 

As expected (c/. ref. 196), one of the materials produced via interaction of bistrifluoromethyl nitroxide with phosphorus trifluoride is also the familiar N-O-N... 

Pentafluorobenzalddiyde reacts with bistrifluoromethyl nitroxide (see also p. 414) to give the amino-oxy-compound C6Fs CX>2-N(CF3)s, with the monohydrazide of cyclic trimeric phosphonitrile fluoride to give the hydrazone (117), and with ethyl acetoacetate and ammonia to give the expected dihydropyridine derivative (118). (Pfcntajauorophenyl)acetaldehyde is obtained in excellent yield from 2-(pentafluoropheny])ethanol and sodium dichromate in dimethyl sulphoxide the solvent may prevent further oxidation of the aldehyde. ... 

Tetrafluoroallene reacts with two moles of bistrifluoromethyl nitroxide at ambient temperature. The initial adduct (134) reacts further with the radical to give a ketone (135a) and the bistrifiuoromethylamino-radical, which may attack the allene at the central carbon atom since the enamine (136) is isolated in substantial yield. Alternatively, the enamine (136) may arise by reaction of the allene with perfluoro-(2,4-dimethyl-3-oxa-2,4-diazapentane) (135b), because the N—O—N compound was shown to react in this way with the allene at room temperature. The yield of the ketone rose to 89%, accompanied by an equimolar proportion of the N—O—compound, when the allene was treated with a six-fold excess of the nitroxide, further justifying the proposed reaction scheme (Scheme 29). 

The simplest perfluorinated diketone, perfluorobiacetyl, has featured in publications dealing with photolysis of anhydrides in the presence of iron pentacarbonyl [(RfC0),0 —(RrCO)2, RfC0j CRf CRf 02CRf, RfCOF, and (Rf)2 (Rp = CF, or CHF2)], in e.s.r. studies on the mechanism of reduction of a-diketones by alkali metals, and in the reaction between perfluorobut-2-yne and bistrifluoromethyl nitroxide (see p. 117). 

Nitroxides, Hydroxylamines, and Nitroso- and Nitro-compounds. The chemistry of the magic radical , bistrifluoromethyl nitroxide, and related compounds particularly (CF3)jN OH and [(CFj),N O],Hg has been dealt with at some length in the review literature full details of the work on reactions between (i) the nitroxide and tetrasulphur tetranitride -> N4S4[O N(CF8)2]4, also obtainable from (CFj),N-0- + N4S4H4 or N3S3CI3 and [(CF3)jN-0]jHg + N3S3CI3, (ii) the mercurial [(CF3)3N-0]3Hg and thiazyl fluoride - ... 

When Blackley and Reinhard first isolated bistrifluoromethyl nitroxide, they found it unreactive towards mercury -a conclusion they have since revised, but perhaps not before Emeleus and Spaziante reported the formation of mercuric bistrifluoromethylnitroxide from the radical and mercury at 20 °C. ... 

The compound produced by u.v. irradiation of bistrifluoromethyl nitroxide, and hitherto believed to be the peroxidic dimer (CFa)jN O O N(CFs)2, has now been shown to be the well known N—O—N compound perfluoro-(2,4-dimethyl-3-oxa-2,4-diazapentane) chemical proof of structure was provided through study of its thermal decomposition [2 (CF3)2N-O N(CF3)2... 

C( CFa)-CF2-0 N(CFj)j]. A new method for converting bistrifluoromethyl nitroxide into perf uoro-(2,4-dimfithyl-3-oxa-2,4-diazapentane) comprises mixing it with iron pentacarbonyl at room temperature at ISO—170 °C this reagent converts the N—O—compound into perfluoro-2-azapropene [as expected, since the dissociation (CFs jN-O-NCCF,), (CF3)3N O + (CF,)2N occurs at temperatures above 80 °C] and JVJV-bistrifluoromethyl-hydroxylamine into bistrifluoromethylamine. ... 

The main reaction paths proposed to account for the outcome of reactions between bistrifluoromethyl nitroxide and the isocyanides Bu NC and CF -NC are shown in Scheme 28b. t-Butyl isocyanide was shown by separate experiment to undergo a novel insertion reaction with perfluoro-(2,4-dimethyl-3-oxa-2,4-diazapentane)to yield the mixed imineBu N CtN(CF,), ]-[0-N(CF3)J."=>... 

The molecular structures of bistrifluoromethyl nitroxide and its parent hydroxylamine have been determined by electron diffraction. 

Nitroxides and Nitroso- and Nitro-compounds. Further examples of the formation of 2 1 adducts from bistrifluoromethyl nitroxide and halogenated olefins [those used were CF CHF, CHjtCFj, CFg CFCI, CFjtCFBr, CF2 C(CFa)2, and COjrCCls] have been quoted, and perfiuorobutadiene has been shown to give a 2 1 and, under forcing conditions (250°C), a 4 1 adduct. Kinetic studies have established the following order of susceptibility towards attack by the nitroxide ... 

Treatment of pentafluoropyridine with an excess of bistrifluoromethyl nitroxide at 80°C for a week yields only the 4 1 adduct (23) [X = (CF8)aN 0-l (97%) similarly, photochemical chlorination gives the tetra-chloro-derivative (23) (X = Cl) (99%). These results accord with the resistance shown by the C N bond in perfluoro-2,3,4,5-tetrahydropyridine (23) (X = F) towards attack by bistrifluoromethyl nitroxide and atomic chlorine. ... 

Bistrifluoromethyl nitroxide combines with tristrifluoromethylphosphine to yield the phosphorane (CF8)sP[0-N(CF,)2]a, and has been likened to chlorine in this respect similarly, chlorobistrifluoromethylphosphine gives (CFa)2PCl[0 N(CF3)2]a. The trimethylsiloxyphosphorane (CFj)3-P(O SiMe3)3 is formed almost quantitatively when tristrifluoromethylphosphine oxide is left in contact with hexamethyldisiloxane at room temperature for several days thermal decomposition of the phosphorane yields principally the ester (CFalaPCOl O SiMej, another new compound which can also be prepared from (CFs)2P(0)Cl and MeaSi-O-SiMea. ... 

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