Yu. S. Danilevich

Synthesis and properties of N-(allyl)trifluoromethanesulfonamide

We have recently synthesized the first N-alkenylsubstituted trifluoromethanesulfonamide, N-methyl-N[(E)-2-phenylethenyl]trifluoromethanesulfonamide CF3SO2N(Me)CH=CHPh, by dehydrobromination of N-(2-bromo-2-phenylethyl)-N-(methyl)trifluoromethanesulfonamide [1]. An attempt to obtain in a similar way its NH analog, CF3SO2NHCH=CHPh was unsuccessful; instead of the dehydrobromination product, we isolated 2,5-diphenyl-1,4-(trifluoromethylsulfonyl)piperazine [2]. However, N-monosubstituted trifluoromethanesulfonamides CF3SO2NHR attract particular interest as strong NH acids which can be functionalized at the nitrogen atom. Therefore, the present communication describes the synthesis and transformations of the first unsaturated NH trifluoromethanesulfonamide, N-(allyl)trifluoromethanesulfonamide (I).

N -allenyl- N -benzyltrifl uoromethanesulfonamide

First N-allenyl-substitued triflamides CF3SO2N(Bn)CH=C=CH2 were synthesized from N-allyltriflamides by sucessive reactions of bromination, N-alkylation, and dehydrobromination. Isomeric N-propargyltriflamide CF3SO2N(Bn)CH2C≡CH is present in the reaction products as a minor admixture.

Highly unsaturated trifluoromethanesulfonamide derivatives

Reactions of N-propargyltriflamide TfNHCH2C≡CH (Tf = CF3SO2) with allyl bromide or propargyl bromide in DMSO afforded highly unsaturated triflamide derivatives: N-allyl-N-propargyltriflamide TfN·(CH2CH=CH2)(CH2C≡CH), N-allenyl-N-allyltriflamide TfN(CH2CH=CH2)(CH=C=CH2), and N-allenyl-N-propargyltriflamide TfN(CH=C=CH2)(CH2C≡CH). By the reaction of triflamide with propargyl bromide in DMSO N,N-dipropargyltriflamide TfN(CH2C≡CH)2 was obtained, which under the treatment with t-BuOK in DMSO underwent isomerization giving an equilibrium mixture with N-allenyl-N-propargyltriflamide TfN (CH2C≡CH)(CH=C=CH2) in a ratio 85: 15.

Reactions of trifluoromethanesulfonamide with amides and paraformaldehyde

Two- and three-component condensations of paraformaldehyde with trifluoromethanesulfonamide, acetamide, trifluoroacetamide, 1H-benzotriazole, methanesulfonamide, and malonamide were studied. N-Hydroxymethyl derivatives of trifluoroacetamide and 1H-benzotriazole reacted with trifluoromethanesulfonamide to give N-(trifluoroacetylaminomethyl)- and N-(1H-benzotriazol-1-ylmethyl)-substituted derivatives of tri-fluoromethanesulfonamide, as well as N,N′-methylenebis(trifluoromethylsulfonamide) and N-(trifluoromethyl-sulfonylaminomethyl)trifluoroacetamide as transamination products. Three-component condensation of trifluoromethanesulfonamide with paraformaldehyde and methanesulfonamide led to the formation of 1-methylsulfonyl-3,5-bis(trifluoromethylsulfonyl)hexahydro-1,3,5-triazine, and the reaction of trifluoromethanesulfonamide with paraformaldehyde and malonamide gave 4,10-bis(trifluoromethylsulfonyl)-2,4,8,10-tetraazaspiro-[5.5]undecane-1,7-dione whose structure was proved by X-ray analysis.

Bromination of highly unsaturated trifluoromethanesulfonamide derivatives

The bromination of trifluoro-N-(prop-2-yn-1-yl)methanesulfonamide with molecular bromine gives a mixture of Z- and E-isomeric N-(2,3-dibromoprop-2-en-1-yl)trifluoromethanesulfonamides, regardless of the reaction conditions. Bromine adds to both triple bonds of trifluoro-N,N-bis(prop-2-yn-1-yl)methanesulfonamide, yielding a mixture of N-(2,3-dibromprop-2-en-1-yl)trifluoro-N-(prop-2-yn-1-yl)methanesulfonamide, N,N-bis(2,3-dibromoprop-2-en-1-yl)trifluoromethanesulfonamide, and trifluoro-N,N-bis(2,2,3,3-tetrabromopropyl) methanesulfonamide. Diacetylenic trifluoromethanesulfonamide derivative, N,N′-hexa-2,4-diyne-1,6-diylbis( trifluoromethanesulfonamide), reacts with bromine to afford N,N′-[(2E,4E)-2,3,4,5-tetrabromohexa-2,4-diene-1,6-diyl]bis(trifluoromethanesulfonamide) and isomeric N-(2,3-dibromoprop-2-en-1-yl)trifluoromethanesulfonamides resulting from reductive cleavage of the central C–C bond in the former.

Synthesis and bromination/dehydrobromination of N,N-diallyltrifluoromethanesulfonamide

The reaction of triflluoromethanesulfonamide with allyl bromide in dimethyl sulfoxide gave N,N-diallyltrifluoromethanesulfonamide which was subjected to bromination with 1 and 2 equiv of bromine. The product of bromine addition to both allyl groups, CF3SO2N(CH2CHBrCH2Br)2, was found to exist as a mixture of two diastereoisomers at a ratio of 9: 11. Its dehydrobromination by the action of sodium methoxide was chemoselective with successive elimination of one, two, and three hydrogen bromide molecules to afford N-(2-bromoprop-2-en-1-yl)-N-(2,3-dibromopropyl)trifluoromethanesulfonamide, N,N-bis(2-bromoprop-2-en-1-yl)trifluoromethanesulfonamide, and N-(2-bromoprop-2-en-1-yl)-N-(propadienyl)trifluoromethanesulfonamide, respectively.

Reaction of N-phenyltriflamide with 1,2-dibromoethane and propargyl bromide. Unexpected cleavage of С–С and С–N bonds

Reaction of N-phenyltriflamide with 1,2-dibromoethane under basic conditions in DMSO unexpectedly results in N-methyl-N-phenyltriflamide and 1,3-diphenylurea. The presumed reaction mechanism includes the formation of unstable intermediate disubstitution product TfN(Ph)CH2CH2N(Ph)Tf that suffers the the С–С bond cleavage resulting in TfN(Me)Ph and N,N′-methanediylbis(N-phenyltriflamide). The latter reacts with K2CO3 releasing two molecules of potassium triflinate and after hydrolysis of diphenylcarbodiimide PhN=C=NPh gives 1,3-diphenylurea. With propargyl bromide, N-phenyltriflamide affords N-propargyl-Nphenyltriflamide in high yield. The bromination of the latter results in a mixture of Z,E-isomers of N-(2,3-dibromoprop-2-en-1-yl)-N-phenyltriflamide which undergo dehydrobromination giving first N-(3-bromopropanedienyl)-N-phenyltriflamide and then the products of the C–N bond cleavage: N-phenyltriflamide and 3,3-dimethoxyprop-1-yne.

Unsaturated derivatives of trifluoromethanesulfonimide

N-Allyl- and N-propargyltrifluoromethanesulfonimides were synthesized by reaction of trifluoromethanesulfonic anhydride with allylamine and propargylamine. Some reactions of the resulting unsaturated derivatives were studied, in particular bromination, dehydrobromination of the bromination product, and nucleophilic substitution of bromine.

Electrochemical fluorination of benzamide and acetanilide in anhydrous HF and in acetonitrile

Electrochemical fluorination of benzamide in anhydrous hydrogen fluoride does not involve the amide group but occurs exclusively at the aromatic ring, yielding isomeric fluoro- and difluorobenzamides and 3,3,6,6-tetrafluoro-1,4-cyclohexadienecarboxamide. Electrochemical fluorination of benzamide in acetonitrile as solvent gives the same products, as well as benzonitrile and its fluorinated derivatives and products of hydrolysis and fluorination of acetonitrile. Electrochemical fluorination of acetanilide in anhydrous HF leads to complete tarring of the reaction mixture, while its fluorination in acetonitrile results in selective formation of m-fluoroacetanilide.

Reactions of N-Allyl- and N-Propargyltriflimides with N,N′-Disubstituted Carbodiimides

The alkylating activity of N-allyl- and N-propargyltriflimides toward N,N′-dicyclohexyl- and N,N′-diphenylcarbodiimides has been studied. Activation of the nitrogen atom by two electron-withdrawing trifluoromethanesulfonyl groups favors cleavage of the C–N bond in the absence of a catalyst with the formation of N-substituted unsaturated ureas.