1-Phenyl-1H-imidazol-3-ium Trifluoromethanesulfonate

Used Chemicals

• 2-Cyanoethyl N,N,N',N'-Tetraisopropylphosphordiamidite [C2228]
• 1-Phenyl-1H-imidazol-3-ium Triflate (= N-PhIMT) [P2822]
• Acetonitrile
• DMF

Procedure

To an acetonitrile (2 mL)　solution of 2-cyanoethyl N,N,N',N'-tetraisopropylphosphordiamidite (0.42 g, 1.4 mmol) and N-PhIMT (0.34 g, 1.2 mmol) were added a DMF solution of 1 (0.40 g, 1.2 mmol) under nitrogen atmosphere. The reaction mixture was stirred overnight at room temperature, then diluted with TBME and washed with H₂O, DMF:H₂O (1:1) solution, H₂O and brine. The organic layer was concentrated under reduced pressure. The resulting crude product was purified by column chromatography (hexane:ethyl acetate:triethylamine = 1:2:0.03 on silica gel) to give 2 as a white powder (0.43 g, 66% yield).

Experimenter’s Comments

The reaction mixtures were monitored by LCMS.

Analytical Data

Compound 2

¹H NMR (400 MHz, DMSO-d6); δ 11.36 (brs, 1H), 8.05-7.96 (m, 2H), 7.73-7.64 (m, 1H), 7.59-7.51 (m, 2H), 7.45-7.37 (m, 1H), 6.25-6.17 (m, 1H), 4.72-4.62 (m, 1H), 4.62-4.52 (m, 1H), 4.51-4.38 (m, 1H), 4.32-4.15 (m, 1H), 3.84-3.66 (m, 2H), 3.66-3.51 (m, 2H), 2.84-2.73 (m, 2H), 2.47-2.22 (m, 2H), 1.67-1.53 (m, 3H), 1.27-1.03 (m, 12H).

¹³C NMR (101 MHz, DMSO-d6); δ 165.5, 163.6, 150.4, 135.8, 133.7, 129.3 (3C), 128.9 (2C), 119.0, 109.9, 84.1, 82.8, 72.8, 64.9, 58.3 (2C), 42.7, 37.7, 24.3 (4C), 19.8, 11.9.

³¹P NMR (162 MHz, DMSO-d6); δ 147.89.

Lead Reference

• Acid/Azole Complexes as Highly Effective Promoters in the Synthesis of DNA and RNA Oligomers via the Phosphoramidite Method
• Y. Hayakawa, R. Kawai, A. Hirata, J. Sugimoto, M. Kataoka, A. Sakakura, M. Hirose, R. Noyori, J. Am. Chem. Soc. 2001, 123, 8165.

References

• N-phenylimidazolium triflate as a highly effective promoter for the interribonucleotide-bond formation via the phosphoramidite method
  • R. Kawai, J.-i. Sugimoto, M. Kataoka, Y. Hayakawa, Nucleosides Nucleotides Nucleic Acids 2001, 20, 1047.
• Acid/Azole Complexes as Highly Effective Promoters in the Synthesis of DNA and RNA Oligomers via the Phosphoramidite Method
  • Y. Hayakawa, R. Kawai, A. Hirata, J.-i. Sugimoto, M. Kataoka, A. Sakakura, M. Hirose, R. Noyori, J. Am. Chem. Soc. 2001, 123, 8165.
• Utility of azolium triflates as promoters for the condensation of a nucleoside phosphoramidite and a nucleoside in the Agrawal's stereoselective synthesis of nucleoside phosphorothioates
  • M. Hyodo, H. Ando, H. Nishitani, A. Hattori, H. Hayakawa, M. Kataoka, Y. Hayakawa, Eur. J. Org. Chem. 2005, 5216.
• Nucleosidic Phosphoramidite Synthesis via Phosphitylation: Activator Selection and Process Development
  • C. Xie, M. A. Staszak, J. T. Quatroche, C. D. Sturgill, V. V. Khau, M. J. Martinelli, Org. Process Res. Dev. 2005, 9, 730
• Benzimidazolium triflate (a review)
  • Y. Hayakawa, e-EROS Encyclopedia of Reagents for Organic Synthesis. 2003, 1.