Synlett 2019; 30(20): 2300-2304
DOI: 10.1055/s-0039-1690236
letter
© Georg Thieme Verlag Stuttgart · New York

An Efficient Deprotection of 2,6-Bis(trifluoromethyl)phenylboronic Esters via Catalytic Protodeboronation Using Tetrabutyl­ammonium Fluoride

Sari Urata
,
Shinya Nojima
,
Kazuishi Makino
,
Japan Society for the Promotion of Science [JSPS KAKENHI Grant 19K07000 (N.S.) for Scienfic Research (C)], Japan Society for the Promotion of Science [JSPS KAKENHI Grant 17K08218 (K.M.) for Scienfic Research (C)], Sasakawa Scientific Research Grant from The Japan Science Society (S.U.), and Kitasato University Research Grant for Young Researchers (N.S.).
Further Information

Publication History

Received: 20 September 2019

Accepted after revision: 16 October 2019

Publication Date:
30 October 2019 (online)


Abstract

We herein describe an efficient deprotection of 2,6-bis(trifluoromethyl)phenylboronic esters, which serve as effective protective groups for 1,2- or 1,3-diols in various organic transformations, via protodeboronation by using a catalytic amount of tetrabutylammonium fluoride (TBAF).

Supporting Information

 
  • References and Notes

  • 1 Wuts PG. M. Greene’s Protective Groups in Organic Synthesis, 5th ed . John Wiley & Sons; Hoboken: 2014
  • 2 Hall DG. Boronic Acids, 2nd ed. . Wiley-VCH; Weinheim: 2011
    • 3a Ferrier RJ. Methods Carbohydr. Chem. 1972; 6: 419
    • 3b Ferrier RJ. Adv. Carbohydr. Chem. Biochem. 1978; 35: 31

      For a book, and reviews of boronic acids as protective reagents, see:
    • 4a Wuts PG. M. In Greene’s Protective Groups in Organic Synthesis, 5th ed . John Wiley & Sons; Hoboken: 2014: 468
    • 4b Duggan PJ, Tyndall EM. J. Chem. Soc., Perkin Trans. 1 2002; 1325
    • 4c McClary CA, Taylor MS. Carbohydr. Res. 2013; 381: 112

      For selected examples of boronic esters as protective groups or transient masking groups, see:
    • 5a Kaji E, Nishino T, Ishige K, Ohya Y, Shirai Y. Tetrahedron Lett. 2010; 51: 1570
    • 5b Nishino T, Ohya Y, Murai R, Shirahata T, Yamamoto D, Makino K, Kaji E. Heterocycles 2012; 84: 1123
    • 5c Kaji E, Yamamoto D, Shirai Y, Ishige K, Arai Y, Shirahata T, Makino K, Nishino T. Eur. J. Org. Chem. 2014; 3536
    • 5d Nakanishi M, Takahashi D, Toshima K. Org. Biomol. Chem. 2013; 11: 5079
    • 5e Fenger TH, Madsen R. Eur. J. Org. Chem. 2013; 5923
    • 5f Nakagawa A, Tanaka M, Hanamura S, Takahashi D, Toshima K. Angew. Chem. Int. Ed. 2015; 54: 10935
    • 5g Mancini RS, McClary CA, Anthonippillai S, Taylor MS. J. Org. Chem. 2015; 80: 8501
    • 5h Fukuhara K, Shimada N, Nishino T, Kaji E, Makino K. Eur. J. Org. Chem. 2016; 902
    • 5i Mancini RS, Lee JB, Taylor MS. Org. Biomol. Chem. 2017; 15: 132
    • 5j Dimakos V, Garrett GE, Taylor MS. J. Am. Chem. Soc. 2017; 139: 15515
    • 5k Mancini RS, Lee JB, Taylor MS. J. Org. Chem. 2017; 82: 8777
    • 5l Manhas S, Taylor MS. J. Org. Chem. 2017; 82: 11406
    • 5m Kanzaki Y, Hirano Y, Mitsunuma H, Kanai M. Org. Biomol. Chem. 2019; 17: 6562
    • 6a Shimada N, Urata S, Fukuhara K, Tsuneda T, Makino K. Org. Lett. 2018; 20: 6064
    • 6b Shimada N, Fukuhara K, Urata S, Makino K. Org. Biomol. Chem. 2019; 17: 7325

      For review and book for protodeboronation, see:
    • 7a Matteson DS. J. Organomet. Chem. 1999; 581: 51
    • 7b Lee C.-Y, Cheon C.-H. In Boron Reagents in Synthesis, ACS Symposium Series 1236. American Chemical Society; Washington DC: 2016: 483
    • 8a Kuivila HG, Nahabedian KV. J. Am. Chem. Soc. 1961; 83: 2159
    • 8b Kuivila HG, Reuwer JF, Mangravite JA. Can. J. Chem. 1963; 41: 3081
    • 8c Kuivil AH. G, Reuwer JF, Mangravite JA. J. Am. Chem. Soc. 1964; 86: 2666

      For selected examples of base-promoted protodeboronation, see:
    • 9a Lozada J, Liu Z, Perrin DM. J. Org. Chem. 2014; 79: 5365
    • 9b Ahn S.-J, Lee C.-Y, Kim N.-K, Cheon C.-H. J. Org. Chem. 2014; 79: 7277
    • 9c Ding Q, Song Q. Org. Chem. Front. 2016; 3: 14
    • 9d Lee C.-Y, Cheon C.-H. Adv. Synth. Catal. 2016; 358: 549
    • 9e Cox PA, Leach AG, Campbell AD, Lloyd-Jones GC. J. Am. Chem. Sci. 2016; 138: 9145
    • 9f Cox PA, Reid M, Leach AG, Campbell AD, King EJ, Lloyd-Jones GC. J. Am. Chem. Sci. 2017; 139: 13156
    • 9g Huang X, Hu J, Wu M, Wang J, Peng Y, Song G. Green Chem. 2018; 20: 255
    • 10a Klingensmith LM, Bio MM, Moniz GA. Tetrahedron Lett. 2007; 48: 8242
    • 10b Zhang G, Li Y, Liu J. RSC Adv. 2017; 7: 34959 ; see also ref. 9b
  • 11 Barker G, Webster S, Johnson DG, Curley R, Andrews M, Young PC, Macgregor SA, Lee A.-L. J. Org. Chem. 2015; 80: 9807
    • 12a Fürstner A, Radkowski K. Chem. Commun. 2002; 2182
    • 12b Lacombe F, Radkowski K, Seidel G, Fürstner A. Tetrahedron 2004; 60: 7315
    • 12c Sundararaju B, Fürstner A. Angew. Chem. Int. Ed. 2013; 52: 14050
    • 12d Liu C, Li X, Wu Y. RSC Adv. 2015; 5: 15354
    • 12e Nagao K, Yamazaki A, Ohmiya H, Sawamura M. Org. Lett. 2018; 20: 1861
  • 13 Liu C, Li X, Wu Y, Qiu J. RSC Adv. 2014; 4: 54307
  • 14 Shen F, Tyagarajan S, Perera D, Krska SW, Maligres PE, Smith MR. III, Maleczka RE. Jr. Org. Lett. 2016; 18: 1554
  • 15 Clausen F, Kischkewiz M, Bergander K, Studer A. Chem. Sci. 2019; 10: 6210
  • 16 Nave S, Sonawane RP, Elford TG, Aggarwal VK. J. Am. Chem. Soc. 2010; 132: 17096
    • 17a Elford TG, Nave S, Sonawane RP, Aggarwal VK. J. Am. Chem. Soc. 2011; 133: 16798
    • 17b Roesner S, Casatejada JM, Elford TG, Sonawane RP, Aggarwal VK. Org. Lett. 2011; 13: 5740
    • 17c Scott HK, Aggarwal VK. Chem. Eur. J. 2011; 17: 13124
    • 17d Aggarwal VK, Ball LT, Carobene S, Connelly RL, Hesse MJ, Partridge BM, Roth P, Thomas SP, Webster MP. Chem. Commun. 2012; 48: 9230
    • 17e Roesner S, Aggarwal VK. Can. J. Chem. 2012; 90: 965
    • 17f Watson CG, Aggarwal VK. Org. Lett. 2013; 15: 1346
    • 17g Roesner S, Blair DJ, Aggarwal VK. Chem. Sci. 2015; 6: 3718
  • 18 TBAF (ca. 1 mol/L in tetrahydrofuran including maximum 10% of water) was purchased from Tokyo Chemical Industry Co., Ltd and used.
  • 19 In this study, maximun 6.7 equiv of water are included when 120 mol% of TBAF were used.
  • 20 The only byproduct of this reaction is 1,3-bis(trifluoromethyl)benzene (3) with low boiling point (b.p. 116 °C), which can be easily removed by evaporation during the workup procedure. Therefore, the desired diol at satisfactory level of purity was obtained by simple filtration of reaction mixture through a pad of basic amino silica gel eluting with EtOAc. See Supporting Information for experimental details.
  • 21 For a report on the effect of water in reactivity of fluoride ion, see: Sun H, DiMagno SG. J. Am. Chem. Soc. 2005; 127: 2050
  • 22 Deprotection of the corresponding phenylboronic ester only gave the small amount of diol 2a (16% conversion yield) after 24 h under the conditions using 10 mol% of TBAF in the presence of 3.0 equiv of water at room temperature. See the Supporting Information for details.

    • The Perrin and Lloyd-Jones groups independently reported that two ortho electron-withdrawing substituents on arylboronic acid accelerate base-catalyzed protodeboronation, see:
    • 23a Lozada J, Liu Z, Perrin DM. J. Org. Chem. 2014; 79: 5365
    • 23b Cox PA, Reid M, Leach AG, Campbell AD, King EJ, Lloyd-Jones GC. J. Am. Chem. Soc. 2017; 139: 13156
  • 24 The reaction in the presence of 3.0 equiv of water with 5 mol% of TBAF resulted in a remarkably decreased yield (53%).
  • 25 Our attempt to deprotect under the optimized conditions using boronic ester derived from 4,6-dihydoroxyhexanoic acid failed, resulting in a nearly quantitative recovery of the starting material.
  • 26 General Procedure for the Deprotection of the Boronic Esters with TBAF; Method A (Catalytic Conditions, Table [1], Entry 8) TBAF (0.20 M in THF, 100 μL, 0.0200 mmol, 10 mol%) and H2O (6.0 M in THF, 100 μL, 0.600 mmol, 3.0 equiv) were added to a solution of 1a (89.2 mg, 0.200 mmol, 1.0 equiv) in dry THF (1.8 mL, total 0.10 M) at room temperature. After stirring for 2 h under reflux and cooling to room temperature, the reaction mixture was filtered through a short pad of amino silica gel (800 mg) eluting with EtOAc (20 mL), and the filtrate was concentrated under reduced pressure to give 2a (46.8 mg, 0.200 mmol, >99% yield) as a colorless oil. Analytical Data for 2a Rf = 0.13 (n-hexane/EtOAc, 4:1). 1H NMR (400 MHz, CDCl3): δ = 7.38–7.27 (m, 5 H), 4.53 (s, 2 H), 3.90–3.79 (m, 3 H), 3.57–3.49 (m, 2 H), 2.34 (br s, 2 H), 1.79–1.52 (m, 6 H). 13C NMR (100 MHz, CDCl3): δ = 137.9, 128.4, 127.8, 127.7, 73.1, 71.9, 70.5, 61.7, 38.3, 35.2, 26.2. IR (neat): ν = 3372, 2942, 2865, 1278, 1099 cm–1. HRMS (ESI): m/z calcd for C13H20O3Na [M + Na]+: 247.1310; found: 247.1311. Method B (Stoichiometric Conditions, Table [1], Entry 1) TBAF (1.0 M in THF, 0.24 mL, 0.240 mmol, 120 mol%) was added to a solution of 1a (89.2 mg, 0.200 mmol, 1.0 equiv) in dry THF (1.8 mL, total 0.10 M) at room temperature. After stirring for 2 h under reflux, cooling to room temperature, the reaction mixture was filtered through a short pad of amino silica gel (800 mg) eluting with EtOAc (20 mL), and the filtrate was concentrated under reduced pressure to give 2a (44.8 mg, 0.200 mmol, >99% yield) as a colorless oil.