Syntheses of 1-alkyl-1,2,4-triazoles and the formation of quaternary 1-alkyl-4-polyfluoroalkyl-1,2,4-triazolium salts leading to ionic liquids

Abstract

1,2,4-Triazole was alkylated (alkyl = methyl, butyl, heptyl, decyl) at N-1 in >90% isolated yields. The resulting 1-alkyl triazoles were quaternized at N-4 in >98% isolated yields using fluorinated alkyl halides with >98% isolated yields, under neat reaction conditions at 100-120 °C to form N1-CH3-N4-(CH2)2Cm F2m+1-triazolium (Taz) iodide (m = 1, 6), N1-C4H9-N4-(CH2)2 CmF2m+1-Taz iodide (m = 1, 4, 6), N1-C7H15-N4-(CH2)2 CmF2m+1-Taz iodide (m = 1, 4, 6), N1-C10H21-N4-(CH2)2 CmF2m +1-Taz iodide (m = 1, 4), and N1-CnH2n+1-(CH2)2F-Taz bromide (n = 4, 7, 10). Single-crystal X-ray analyses confirmed the structure of [1-CH3-4-CH2CH2 CF3-Taz]+I-. It crystallized in the orthorhombic space group Pccn, and the unit cell dimensions were a = 13.8289(9) Å, b = 17.3603-(11) Å, c = 9.0587(6) Å (α = β = γ = 90°). Metathesis of these polyfluoroalkyl-substituted triazolium halides with other salts led to the formation of quaternary compounds, some of which comprise ionic liquids, namely, [R(Rf)-Taz]+Y- (Y = NTf2, BF4, PF6, and OTf), in good isolated yields without the need for further purification: N1-CH3-N4-(CH2)2 CmF2m+1-1-Taz Y (m = 1, 6; Y = NTf2), N1- C4H9-N4-(CH2)2 CmF2m+1-Taz Y (m = 1, 4, 6; Y = NTf2), N1-C7H15-N4-(CH2)2 CmF2m+1-Taz Y (m-1, 4, 6; Y = NTf2), N1-CnH2n+1-N4-(CH2)2F-Taz Y (n = 7, 10; Y = NTf2), N1-C10H21-N4-(CH2)2F-TazY (Y = OTf), N1-C7H15-N4-(CH2)2F-TazY (Y = BF4), N1-C4H9-N4-(CH2)2 CmF2m+1-Taz Y (m = 4, 6; Y = PF6), N1-C7H15-N4-(CH2)2 C4F9-Taz Y (Y = PF6), N1-C4H9-N4-(CH2)2 CmF2m+1-Taz Y (m = 4, 6; Y = OTf). All new compounds were characterized by 1H, 19F, and 13C NMR and MS spectra and elemental analyses. Tgs and Tms of ionic liquids were determined by DSC.