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Synlett 2014; 25(18): 2665-2668
DOI: 10.1055/s-0034-1379167
letter
© Georg Thieme Verlag Stuttgart · New York

A Late-Stage Strategy for the Functionalization of Triazolium-Based NHC Catalysts

Kerem E. Ozboya
Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA   Fax: +1(970)4911801   Email: rovis@lamar.colostate.edu
,
Tomislav Rovis*
Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA   Fax: +1(970)4911801   Email: rovis@lamar.colostate.edu
› Author Affiliations
Further Information

Publication History

Received: 29 July 2014

Accepted after revision: 27 August 2014

Publication Date:
18 September 2014 (online)

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Abstract

A strategy for the diversification of triazolium-based catalysts is presented. This method is based on the reduction to the triazoline, which serves as a suitable and stable substrate for palladium-mediated cross-coupling, followed by trityl cation mediated reoxidation to the triazolium.

Key words

NHC Catalysis - organocatalysis - asymmetric catalysis

Supporting Information

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  • References and Notes


      • For reviews, see:
    • 1a Enders D, Niemeier O, Henseler A. Chem. Rev. 2007; 107: 5606
    • 1b Nair V, Vellalath S, Babu BP. Chem. Soc. Rev. 2008; 37: 2691
      CrossrefPubMed
    • 1c Moore JL, Rovis T. Top. Curr. Chem. 2010; 291: 77
      PubMed
    • 1d Nair V, Menon RS, Biju AT, Sinu CR, Paul RR, Jose A, Sreekumar V. Chem. Soc. Rev. 2011; 40: 5336
    • 1e Vora HU, Wheeler P, Rovis T. Adv. Synth. Catal. 2012; 354: 1617
      CrossrefPubMed
    • 1f Bugaut X, Glorius F. Chem. Soc. Rev. 2012; 41: 3511
      CrossrefPubMed
    • 1g Studer A, De Sarkar S, Biswas A, Samanta RC. Chem. Eur. J. 2013; 19: 4664
      Crossref
    • 1h Hopkinson MN, Richter C, Schedler M, Glorius F. Nature (London, U.K.) 2014; 510: 485
  • 2 Seebach D. Angew. Chem., Int. Ed. Engl. 1979; 18: 239

      • Some recent advances include:
    • 3a Fu Z, Xu J, Zhu T, Leong WW. Y, Chi YR. Nat. Chem. 2013; 5: 835
    • 3b White NA, DiRocco DA, Rovis T. J. Am. Chem. Soc. 2013; 135: 8504
    • 3c Cheng J, Huang Z, Chi YR. Angew. Chem. Int. Ed. 2013; 52: 8592
  • 4 Rovis T. Chem. Lett. 2008; 37: 2
    Crossref
    • 5a Kerr MS, Read de Alaniz J, Rovis T. J. Am. Chem. Soc. 2002; 124: 10298
      CrossrefPubMed
    • 5b Read de Alaniz J, Kerr MS, Moore JL, Rovis T. J. Org. Chem. 2008; 73: 2033
      CrossrefPubMed
    • 5c DiRocco DA, Oberg KM, Dalton DM, Rovis T. J. Am. Chem. Soc. 2009; 131: 10872
      CrossrefPubMed
    • 6a Vora HU, Lathrop SP, Reynolds NT, Kerr MS, Read de Alaniz J, Rovis T. Org. Synth. 2010; 87: 350
      Crossref
    • 6b Benhamou L, Chardon E, Lavigne G, Bellemin-Laponnaz S, César V. Chem. Rev. 2011; 111: 2705
    • 6c Kerr MS, Read de Alaniz J, Rovis T. J. Org. Chem. 2005; 70: 5725
      CrossrefPubMed
  • 7 See ref. 4. See also: Mahatthananchai J, Bode JW. Chem. Sci. 2012; 3: 192
  • 8 For a superb example, see: Neel AJ, Hehn JP, Tripet PF, Toste FD. J. Am. Chem. Soc. 2013; 135: 14044
    CrossrefPubMed
  • 9 Brand JP, Osuna Siles JI, Waser J. Synlett 2010; 881
    Article in Thieme Connect
  • 10 Zheng P, Gondo CA, Bode JW. Chem. Asian J. 2011; 6: 614
    Crossref
    • 11a Kobayashi T, Tanaka K, Miwa J, Katsumura S. Tetrahedron: Asymmetry 2004; 15: 185
      Crossref
    • 11b Liu SY, Katsumura S. Chin. Chem. Lett. 2009; 20: 1204
      Crossref
    • 11c Kobayashi T, Hasegawa F, Hirose Y, Tanaka K, Mori H, Katsumura S. J. Org. Chem. 2012; 77: 1812
      Crossref
    • 11d Kuwano S, Harada S, Kang B, Oriez R, Yamaoka Y, Takasu K, Yamada K. J. Am. Chem. Soc. 2013; 135: 11485
      CrossrefPubMed
  • 12 Hsieh S.-Y, Binanzer M, Kreituss I, Bode JW. Chem. Commun. 2012; 48: 8892
    Crossref
    • 13a Miyaura N, Suzuki A. Chem. Rev. 1995; 95: 2457
    • 13b Martin R, Buchwald SL. Acc. Chem. Res. 2008; 41: 1461
      CrossrefPubMed
  • 14 There are several decomposition pathways available to NHC catalysts; for a report, see: Zhao X, Glover GS, Oberg KM, Dalton DM, Rovis T. Synlett 2013; 24: 1229
    Article in Thieme Connect
  • 15 Egert M, Walther S, Plenio H. Eur. J. Org. Chem. 2014; 4362
  • 16 Bildstein B, Malaun M, Kopacka H, Ongania K.-H, Wurst K. J. Organomet. Chem. 1999; 572: 177
  • 17 Typical Experimental Procedure – Synthesis of 5a In a glove box, a dry 2-dram glass vial was loaded with PdCl2(PPh3)2 (7 mg, 0.01 mmol, 0.05 equiv). The vial was sealed and removed from the glove box. To this vial was added triazoline (100 mg, 0.22 mmol, 1 equiv), phenylboronic acid (0.32 mmol, 1.5 equiv), and potassium phosphate tribasic (93 mg, 0.44 mmol, 2 equiv). Anhydrous THF (1.5 mL) was added followed by H2O (0.5 mL), as well as a magnetic stir bar. The vial was sealed, secured with Teflon tape, and heated by oil bath at 60 °C for 6 h. Reaction was deemed complete by TLC. The reaction was cooled to r.t. and brine (1 mL) and EtOAc (1 mL) was added to the reaction. The aqueous fraction was removed, and the organic layer was dried over MgSO4. The crude reaction product was filtered and concentrated. The crude product was purified by flash column chromatography, eluting with 0–50% EtOAc–hexanes through basic alumina, and 60 mg of dark brown solid was isolated (60% yield). Rf  = 0.5 (50% EtOAc–hexane). 1H NMR (300 MHz, acetone-d 6): δ = 7.70–7.60 (m, 4 H), 7.47–7.35 (m, 4 H), 5.68–5.67 (m, 1 H), 5.04 (t, J = 1.1 Hz, 1 H), 4.78 (dd, J = 5.6, 1.1 Hz, 1 H), 4.64–4.55 (m, 2 H), 4.47 (d, J = 15.6 Hz, 1 H), 3.30–3.28 (m, 2 H). 13C NMR (101 MHz, acetone-d 6): δ = 149.0, 141.6, 140.9, 140.3, 139.6, 129.82, 129.73, 128.49, 128.44, 128.38, 127.8, 127.25, 127.18, 127.16, 126.8, 125.6, 123.8, 123.2, 77.1, 73.6, 62.3, 59.2, 34.8. MS: m/z calcd for C24H16F5N3O: 457.4; found: 458.1 [M + H]. IR (neat): 2914, 1626, 1504, 1479, 1429, 1340, 1307, 1055, 1039, 977 cm–1. [α]D 23 –39.17 (c 2.4, acetone).