Synlett 2008(10): 1463-1466  
DOI: 10.1055/s-2008-1078407
LETTER
© Georg Thieme Verlag Stuttgart · New York

An Efficient Organocatalyzed Interconversion of Silyl Ethers to Tosylates Using DBU and p-Toluenesulfonyl Fluoride

Vincent Gembus*, Francis Marsais, Vincent Levacher
Laboratoire de Chimie Organique Fine et Hétérocyclique, UMR 6014, IRCOF, CNRS, Université et INSA de Rouen, B.P. 08, 76131 Mont-Saint-Aignan Cédex, France
Fax: +33(2)35522962; e-Mail: vincent.gembus@insa-rouen.fr;
Further Information

Publication History

Received 27 February 2008
Publication Date:
16 May 2008 (online)

Abstract

A mild and efficient interconversion from silyl ethers to sulfonates esters is reported with good yields. This silyl-sulfonyl exchange proceeds readily in acetonitrile at room temperature in the presence of p-toluenesulfonyl fluoride and a catalytic amount of 1,8-diazabicyclo[5.4.0]undec-7ene (DBU). This method can be used with trimethysilyl (TMS), triethylsilyl (TES) and tert-butyldimethylsilyl (TBDMS) ethers.

    References and Notes

  • 1a Selected recent references: Greene TW. Wuts PGM. Protective Groups in Organic Synthesis   3rd ed.:  Wiley; New York: 1999. 
  • 1b Kim J.-G. Jang DO. Synlett  2007,  2501 
  • 1c Kazemi F. Massah AR. Javaherian M. Tetrahedron  2007,  63:  5083 
  • 1d Comagic S. Schirrmacher R. Synthesis  2004,  883 
  • Selected recent references:
  • 2a Honda T. Kaneda K. J. Org. Chem.  2007,  72:  6541 
  • 2b Prasad KR. Chandrakumar A. J. Org. Chem.  2007,  72:  6312 
  • 2c Ojika M. Kigoshi H. Yoshida Y. Ishigaki T. Nisiwaki M. Tsukada I. Arakawa M. Ekimoto H. Yamada K. Tetrahedron  2007,  63:  3138 
  • 2d Watanabe H. Mori N. Itoh D. Kitahara T. Mori K. Angew. Chem. Int. Ed.  2007,  46:  1512 
  • 2e Lawhorn BG. Boga SB. Wolkenberg SE. Boger DL. Heterocycles  2006,  70:  65 
  • 3 Movassagh B. Shokri S. Z. Naturforsch., B: Chem. Sci.  2005,  60:  763 
  • 4 Poisson T. Dalla V. Papamicaël C. Dupas G. Marsais F. Levacher V. Synlett  2007,  381 
  • For other examples in nucleophilic catalysis in which DBU is superior to other amine bases, see:
  • 6a Aggarwal VK. Mereu A. Chem. Commun.  1999,  2311 
  • 6b Shieh W.-C. Dell S. Repič O. J. Org. Chem.  2002,  67:  2188 
  • 6c Yeom C.-E. Kim HW. Lee SY. Kim BM. Synlett  2007,  146 
  • 6d Murtagh JE. McCooey SH. Connon SJ. Chem. Commun.  2005,  227 
  • 8a Olah GA. Narang SC. Gupta BGB. Malhotra R. J. Org. Chem.  1979,  44:  1247 
  • 8b Morita T. Okamoto Y. Sakurai H. J. Chem. Soc., Chem. Commun.  1978,  874 
  • 8c Morita T. Okamoto Y. Sakurai H. Tetrahedron Lett.  1978,  2523 
  • 8d Olah GA. Narang SC. Tetrahedron  1982,  38:  2225 
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General Procedure for the Preparation of Silyl Ethers 1a-m
To a solution of 3-phenylpropanol (139 mg, 1 mmol) and Et3N (120 mg, 1.1 mmol) in CH2Cl2 (5 mL) was added TMSCl (115 mg, 1.05 mmol). The mixture was stirred at r.t. overnight. The solvent was removed under reduced pressure and the residue was diluted with pentane (10 mL). Simple filtration through a short pad of Celite® provided silyl ether 1a in 93% yield which could be used in the silyl ether exchange reaction without further purification.

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DBU (Sigma-Aldrich) and p-toluenesulfonyl fluoride 97% (Acros Organics) were used as received.

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General Procedure for the Interconversion of Silyl Ethers 1a-m
To a solution of TMS ether 1a (209 mg, 1 mmol) and TsF (179 mg, 1 mmol) in MeCN (2 mL) was added DBU (30 µL, 0.2 mmol). The mixture was stirred for 4 h at r.t. followed by addition of H2O (4 mL). The aqueous phase was extracted with EtOAc (3 × 10 mL). The combined organic layers were washed with H2O (10 mL) and brine (10 mL). After drying (MgSO4) and concentration under vacuum, the residue was chromatographed on SiO2 (cyclohexane-Et2O, 9:1) affording tosylate 2a (278 mg, 96% yield).

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Spectral Data for Tosylate 2h
1H NMR (300 MHz, CDCl3): δ = 7.77 (d, 2 H, J = 8.3 Hz), 7.51 (d, 1 H, J = 7.5 Hz), 7.36 (d, 2 H, 8.3 Hz), 7.29 (t, 1 H, J = 7.5 Hz), 7.21 (t, 1 H, J = 7.5 Hz), 6.86 (d, 1 H, J = 7.5 Hz), 4.58 (s, 2 H), 2.61 (s, 1 H), 2.48 (s, 3 H). 13C (75 MHz, CDCl3): δ = 146.9, 145.9, 134.6, 132.2, 130.3, 130.0, 128.8, 128.5, 127.6, 122.3, 59.6, 21.8. IR (KBr): νmax = 3392, 1597, 1487, 1453, 1371, 1192, 1179, 1156, 1089, 1040.
Spectral Data for Tosylate 2d
1H NMR (300 MHz, CDCl3): δ = 7.66 (d, 2 H, J = 8.3 Hz), 7.35-7.17 (m, 7 H), 5.20-5.18 (m, 1 H), 4.93-4.89 (m, 1 H), 4.28-4.15 (m, 2 H), 2.43 (s, 3 H), 1.41 (s, 9 H). 13C (75 MHz, CDCl3): δ = 155.0, 145.0, 137.8, 132.4, 129.9, 128.8, 128.0, 127.9, 126.6, 80.1, 71.6, 28.3, 21.7. IR (KBr): νmax = 3383, 1690, 1525, 1361, 1172, 1097, 1052, 964. Mp 123-124 °C.
Spectral Data for Tosylate 2i
1H NMR (300 MHz, CDCl3): δ = 9.13 (d, 1 H, J = 6.0 Hz), 8.22 (t, 1 H, J = 7.7 Hz), 7.80 (d, 1 H, J = 7.7 Hz), 7.72 (t, 1 H, J = 6.9 Hz), 7.59 (d, 2 H, J = 8.1 Hz), 7.04 (d, 2 H, J = 8.1 Hz), 4.96 (t, 2 H, J = 7.7 Hz), 3.44 (t, 2 H, J = 7.7 Hz), 2.43-2.35 (m, 2 H), 2.27 (s, 3 H). 13C (75 MHz, CDCl3): δ = 158.4, 144.9, 144.1, 142.4, 139.2, 128.7, 126.0, 125.9, 124.6, 59.4, 32.5, 21.7, 21.4. IR (KBr): νmax = 3434, 1628, 1505, 1190, 1129, 1039, 1012, 812, 691, 571. Mp 120-121 °C. All other synthesized compounds are in accordance with the literature data.

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Polystyrene-bound DBU (1.15 mmol/g loading, 1% cross-linked with DVB) was purchased from Aldrich.