Chemistry

S. P. Makarov, A. Ya. Yakubovich, V. A. Ginsburg, A. S. Filatov,
M. A. Englin, N. F. Privezentsеva, and T. Ya. Nikiforova

Reactions of Polyfluorinated Nitrosoalkanes with Amines

(Presented by Academicians I. L. Knunyants and M. I. Kabachnik on June 1, 1961)

Polyfluorinated nitrosoalkanes are compounds with strongly pronounced electrophilic properties [1]. Below we describe a study of the reactions of polyfluorinated nitroso compounds with substances containing the nucleophilic group \(NH_2\). In ether or alcoholic media, polyfluorinated nitrosoalkanes react vigorously with amines, forming resinous products. At low temperatures (\(-70 \div -100^\circ\)) or in the presence of \(CH_3COOH\), the corresponding azo compounds are obtained:

\[ R_fNO + H_2NR \to [R_fN(OH)NHR] \to H_2O + R_fN = NR. \]

Aliphatic, alicyclic, and aromatic primary amines react in the indicated manner. As the basicity decreases, the reactivity of the amine decreases. Thus, the rate of reaction of aniline with trifluoronitrosomethane is more than 3 orders of magnitude lower than with aliphatic amines. Amides and urethanes do not react with nitroso compounds.

The mechanism of the reaction under consideration is clearly illustrated by the example of the interaction of primary amines with polyfluoronitrosoalkanes containing a chlorine atom at the carbon bonded to the nitroso group. In this case, in ether at \(-50 \div -30^\circ\), along with azo compounds, \(\alpha\)-H-containing polyfluorinated azoxy compounds are formed. In the reaction with carbonic acid salts of amines, the azoxy compounds are the main products:

\[ R_fCFClNO + H_2NR \to [R_fCFClN(OH)NHR] \mathop{\longrightarrow}^{-HCl} \]

\[ \to R_fCF = N(O)NHR] \to R_fCFHN(O) = NR. \]

Thus, from the primary product of amine addition to the nitroso compound, either the elements of water may be split off, forming azo compounds, or \(HX\) may be split off, forming azoxy compounds. Similarly to primary amines, organic hydrazine derivatives also react with polyfluorinated nitroso compounds:

\[ R_fNO + H_2NNHR \to R_fN = NNHR, \qquad R_fNO + H_2NNHCOR \to R_fN = NNHCOR \]

and \(O\)-alkylhydroxylamines,

\[ R_fNO + H_2NOR \to R_fN = NOR. \]

Of interest were the properties of polyfluorotriazene, formed in the reaction of trifluoronitrosomethane with phenylhydrazine. This substance is cleaved under the action of phenol with formation of difluoroformimine:

\[ [C_6H_5NHN = NCF_3] \to C_6H_5N = NNHCF_3 \mathop{\longrightarrow}^{C_6H_5OH} C_6H_5N = NC_6H_4OH + [CF_3NH_2] \to HF + \]

\[ + CF_2 = NH. \]

The latter, at \(420—450^\circ\), undergoes pyrolysis (in vacuum over \(NaF\)), turning into fluorocyanogen:

\[ CF_2 = NH \mathop{\longrightarrow}^{-HF} FC \equiv N. \]

The structure of fluorocyanogen is unequivocally proved both by its conversion into cyanogen fluoride and by other reactions (on hydrolysis—the formation of \(HF\) and \(HOCN\); with aniline—\(N,N'\)-diphenylguanidine; with potassium sulfide—potassium thiocyanate, etc.). Many attempts to synthesize this compound-

Compounds synthesized for the first time

Table 1

* Mol. wt.: found 46.92; 45.94; calculated 45.0. Upon storage for 3 days at −70°, the substance is converted into fluorocyanide with b.p. +72—72.5°; \(d = 1.5270\); analysis: % C 27.78; % F 41.75. (Calculated: % C—26.66; % F—42.2.) It is hydrolyzed to \( \mathrm{C_3H_3O_3N_3} \). Analysis: % C 28.41; 28.60; % H 1.91; 2.20; % N 31.97; 32.30. (Calculated: % C—27.9; % H—2.30; % N—32.51.) On reaction with aniline—\(N_1N\)-diphenylguanidine, m.p. 147°.

** Mol. wt.: found 100.0; 95.0; calculated 97.0.

...were unsuccessful \((^{2-7})\), and the data given in the work of Cosslett \((^2)\) on the properties of fluorocyanogen proved to be erroneous*. In the reaction of trifluoronitrosomethane with ammonia at \(-70^\circ\) in an alcoholic or ethereal medium, an unstable trifluoromethylazohydride is formed, whose presence in solution is demonstrated by the transformations:

\[ \begin{gathered} \mathrm{CF_3NO + NH_3 \to [CF_3N = NH]} \begin{array}{c} \xrightarrow{\mathrm{NOCl}} \mathrm{N_2 + CF_3NO}\\[-2mm] \begin{array}{c} \nearrow^{\mathrm{Hal_2}} \mathrm{N_2 + CF_3Hal\ (Hal = Cl,J)}\\ \searrow_{\substack{-\mathrm{HF}\\+\mathrm{NH_3}}} [\mathrm{CF_2N_2}] \end{array} \end{array} \\ \mathrm{[CF_2N_2] \xrightarrow{P(C_6H_5)_3} CF_2 = P(C_6H_5)_3.} \end{gathered} \]

Trifluoronitrosomethane reacts with aqueous ammonia with formation of nitrogen and fluoroform:

\[ \mathrm{CF_3NO + NH_3 \to [CF_3N = NH] \to N_2 + CF_3H.} \]

With aqueous methylamine, trifluoronitrosomethane quantitatively forms trifluoroazomethane. The interaction of trifluoronitrosomethane with hydrazine under ordinary conditions leads to mineralization of the nitroso compound. At low temperatures \((-70^\circ)\) in methanol, an unstable triazene arises, which under the action of chlorine is converted into trifluoromethyl azide:

\[ \mathrm{CF_3NO + NH_2NH_2 \xrightarrow{-H_2O} [CF_3N = NNH_2] \xrightarrow{Cl_2} 2HCl + CF_3N_3.} \]

Analogously, at low temperature the reaction of trifluoronitrosomethane with hydroxylamine proceeds, forming trifluoromethyldiazohydrate, which in alcoholic media is converted into the corresponding trifluoromethyl ethers:

\[ \mathrm{CF_3NO + H_2NOH \xrightarrow{-H_2O} [CF_3N = NOH] \xrightarrow{ROH} N_2 + H_2O + CF_3OR.} \]

In an alcoholic–alkaline medium the reaction between trifluoronitrosomethane and hydroxylamine proceeds in another direction; instead of elimination of the elements of water, the primary addition product loses hydrogen fluoride, being converted into difluoronitromethane:

\[ \mathrm{[CF_3N(OH)NHOH] \xrightarrow{-HF} CF_2 = N(O)NHOH \to \tfrac{1}{3}NH_3 + \tfrac{1}{3}N_2 + [CF_2 = N(O)OH] \to CF_2HNO_2.} \]

On interaction with nitrogen oxides in carbon tetrachloride at \(0^\circ\), difluoronitromethane forms difluoromethyl nitrite and bis-\(N_1,N'\)-difluoromethylhydroxylamine:

\[ \mathrm{CF_2HNO_2 \xrightarrow{N_2O_4} \begin{cases} \mathrm{CF_2HONO}\\ \mathrm{(CF_2H)_2NONO} \end{cases}} \]

As is evident from the present communication, the nitroso group in polyfluorinated nitrosoalkanes behaves like the nitroso group in aromatic compounds; in many condensation reactions with substances containing an \(\mathrm{NH_2}\) group, this is evidently due to the strong electrophilic effect of the polyfluorinated radicals (cf. \(^{9-14}\)).

Received
5 VI 1961

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* In 1960, when the present investigation had been completed, a report appeared that, during pyrolysis of fluorocyanogen at \(1300^\circ\) in vacuum, fluorocyanide is formed, the constants of which coincide with ours \((^8)\).