N-Methyl-N-(2-phenylethenyl)trifluoromethanesulfonamide

Abstract

SHORT COMMUNICATIONSThere are only a few published data on N-alkenylsubstituted sulfonamides of the general formula R 1 SO 2 N(R 2 )-C(R 3 )=CR 4 R 5 . Hydrostannylation of N-tosyl-substituted ynamines TsN(Bzl)C≡CSiMe 3 [1] and TsN(Bzl)C≡CH [2] led to the corresponding N-tosyl enamines TsN(Bzl)C(SnBu 3 )=CHSiMe 3 [1] and TsN(Bzl)C(SnBu 3 )=CH 2 , and coupling of the latter with various organic halogen compounds RX afforded N-benzyl-N-(1-R-vinyl)-p-toluenesulfonamides TsN(Bzl)C(R)=CH 2 ; N-alkenylsultams were synthesized from N-alkynyl precursors [3]. Unsaturated derivatives of trifluoromethanesulfonamide containing a CF 3 SO 2 N(R)CH=CHR′ fragment were not reported so far. With a view to obtain N-(2-phenylethenyl)-trifluoromethanesulfonamide CF 3 SO 2 NHCH=CHPh we previously synthesized N-(2-phenylethyl)trifluoromethanesulfonamide whose bromination gave N-(2-bromo-2-phenylethyl)trifluoromethanesulfonamide, and the latter was subjected to dehydrobromination by the action of triethylamine [4]. Unexpectedly, the product of this reaction was 2,5-diphenyl-1,4-bis(trifluoromethylsulfonyl)piperazine (Scheme 1); its 1 H and 13 C NMR spectra and melting point were identical to those of a sample synthesized by us previously from styrene and trifluoromethanesulfonamide (its structure was proved by X-ray analysis [5]). initial trifluoromethanesulfonamide contains an NH proton. To rule out this possibility N-(2-phenylethyl)-trifluoromethanesulfonamide (I) was preliminarily subjected to methylation with methyl iodide. N-Methyl-N-(2-phenylethyl)trifluoromethanesulfonamide (II) thus formed was brominated to N-(2-bromo-2-phenylethyl)-N-methyltrifluoromethanesulfonamide (III), and dehydrobromination of the latter with alcoholic alkali afforded N-methyl-N-[(E)-2-phenylethenyl]trifluoromethanesulfonamide (IV) (Scheme 2) as the first representative of N-alkenyl-substituted trifluoromethanesulfonamide derivatives.

Unsaturated Derivatives of Trifluoromethanesulfonamide

“…It is worth mentioning that the first attempt to synthesize an N ‐vinylated triflamide by bromination/dehydrobromination of N ‐phenethyltriflamide ( 1 , Scheme ) failed – the product turned out to be the dimer, the 2,5‐disubstituted piperazine 2 . [18a] Apparently, this was due to the presence of the free NH group; this is deprotonated by a base, and the formed anion acts as an N‐nucleophile, replacing the bromine atom and forming the N–C bond rather than eliminating HBr. Indeed, removal of the NH group by methylation, followed by the same sequence of bromination/dehydrobromination steps, gave N ‐methyl‐ N ‐styryltriflamide ( 3 ) as the first representative of N ‐alkenyltriflamides with the C=C bond directly attached to the nitrogen atom (Scheme ).…”

“…Indeed, removal of the NH group by methylation, followed by the same sequence of bromination/dehydrobromination steps, gave N ‐methyl‐ N ‐styryltriflamide ( 3 ) as the first representative of N ‐alkenyltriflamides with the C=C bond directly attached to the nitrogen atom (Scheme ). [18b]…”

Oxidative addition/cycloaddition of arenesulfonamides and triflamide to N-allyltriflamide and N,N-diallyltriflamide

“…The rst representative of N-alke-nyltriamides was synthesized by us in 2012. 3 Since then, numerous unsaturated triamide compounds having one or two double or/and triple bonds have been synthesized and investigated in different reactions. 4 Another fascinating eld of the triamide chemistry is the reactions of oxidative triamidation of alkenes and dienes, leading in many cases to the products different from those obtained with arenesulfonamides.…”

Highly unsaturated trifluoromethanesulfonamide derivatives

“…The only published data concerned the hydrostannylation of N-tosyl-substituted ynamines TsN(Bn)C≡CSiMe 3 [1] and TsN(Bn)C≡CH [2] resulting in N-tosylsubstituted enamines TsN(Bn)C(SnBu 3 )=CHSiMe 3 [1] and TsN(Bn)C(SnBu 3 )=CH 2 respectively, the coupling of the latter with diverse organyl halides RX afforded N-benzyl-N- (1-R-vinyl)tosylamides TsN(Bn)C(R) =CH 2 , and also the formation of N-alkenylsultams from their N-alkynyl precursors was described [3]. Recently, we have prepared by dehydrobromination of N-(2-bromo-2-phenylethyl)-N-(methyl)-trifluoromethane-sulfonamide CF 3 SO 2 N(Me)CH 2 CHBrPh the first representative of N-alkenyl-substituted trifluoromethanesulfonamides containing a double bond at the nitrogen atom: [4]. We failed to obtain its NH-analog by a similar procedure: Dehydrobromination of N-(2-bromo-2-phenylethyl)-trifluoromethanesulfonamide with trimethylamine yielded the product of cyclodimerization, 2,5-diphenyl-1,4-bis(trifluoromethyl-sulfonyl)-piperazine [5].…”

“…Recently, we have prepared by dehydrobromination of N-(2-bromo-2-phenylethyl)-N-(methyl)-trifluoromethane-sulfonamide CF 3 SO 2 N(Me)CH 2 CHBrPh the first representative of N-alkenyl-substituted trifluoromethanesulfonamides containing a double bond at the nitrogen atom: N-methyl-N-[(E)-2-phenylethenyl]trifluoromethanesulfonamide CF 3 SO 2 N(Me)CH=CHPh [4]. We failed to obtain its NH-analog by a similar procedure: Dehydrobromination of N-(2-bromo-2-phenylethyl)-trifluoromethanesulfonamide with trimethylamine yielded the product of cyclodimerization, 2,5-diphenyl-1,4-bis(trifluoromethyl-sulfonyl)-piperazine [5].…”