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Synlett 2009(10): 1621-1626  
DOI: 10.1055/s-0029-1217349
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© Georg Thieme Verlag Stuttgart ˙ New York

(η6-Arene)RuII/Chiral SN Ligand: A Novel Bifunctional Catalyst System for Asymmetric Transfer Hydrogenation of Aromatic Ketones

Masato Ito, Yuji Shibata, Akira Watanabe, Takao Ikariya*
Department of Applied Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, O-okayama 2-12-1-E4-1, Meguro, Tokyo 152-8552, Japan
Fax: +81(3)57342637; e-Mail: tikariya@apc.titech.ac.jp;
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Publication History

Received 27 January 2009
Publication Date:
02 June 2009 (online)

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Abstract

A binary catalyst system of [RuCl2(η6-arene)]2 and a protic aminothiol (SN) ligand has been found to promote hydrogen transfer between alcohols and carbonyl compounds. The chiral catalyst system with the pipecolinol-derived chiral SN ligand displays excellent stereoselectivity in the asymmetric transfer hydrogenation of aromatic ketones using HCO2H-Et3N. Novel unsymmetrical bis(thiolate)-bridged binuclear complex, which is relevant to the generation of catalytically active species, has been synthesized and structurally characterized.

Key words

[RuCl2(η6-arene)]2 - protic aminothiol ligand - asymmetric transfer hydrogenation - aromatic ketone - bifunctionality

    References and Notes

  • 1a Ito M. Ikariya T. J. Synth. Org. Chem. Jpn.  2008,  66:  1042 
    Google Scholar
  • 1b Ito M. Ikariya T. Chem. Commun.  2007,  5134 
    Google Scholar
  • 1c Ikariya T. Blacker AJ. Acc. Chem. Res.  2007,  40:  1300 
    Google Scholar
  • 1d Ikariya T. Murata K. Noyori R. Org. Biomol. Chem.  2006,  4:  393 
    Google Scholar
  • 2a Ito M. Hirakawa M. Murata K. Ikariya T. Organometallics  2001,  20:  379 
    Google Scholar
  • 2b Ito M. Hirakawa M. Osaku A. Ikariya T. Organometallics  2003,  22:  4190 
    Google Scholar
  • 2c Ito M. Sakaguchi A. Kobayashi C. Ikariya T. J. Am. Chem. Soc.  2007,  129:  290 
    Google Scholar
  • 2d Ito M. Koo L.-W. Himizu A. Kobayashi C. Sakaguchi A. Ikariya T. Angew. Chem. Int. Ed.  2009,  48:  1324 
    Google Scholar
  • 3a Ito M. Osaku A. Kitahara S. Hirakawa M. Ikariya T. Tetrahedron Lett.  2003,  44:  7521 
    Google Scholar
  • 3b Ito M. Kitahara S. Ikariya T. J. Am. Chem. Soc.  2005,  127:  6172 
    Google Scholar
  • 3c Ito M. Osaku A. Shiibashi A. Ikariya T. Org. Lett.  2007,  9:  1821 
    Google Scholar
  • 3d Ito M. Osaku A. Kobayashi C. Shiibashi A. Ikariya T. Organometallics  2009,  28:  390 
    Google Scholar
  • 4a Capper G. Davies DL. Fawcett J. Russell DR. Acta Crystallogr., Sect. C: Cryst. Struct. Commun.  1995,  51:  578 
    Google Scholar
  • 4b Wang F. Chen H. Parkinson JA. Murdoch PS. Sadler PJ. Inorg. Chem.  2002,  41:  4509 
    Google Scholar
  • 4c

    A part of this work was presented in 2007 on the 54th symposium on organometallic chemistry at Hiroshima, Japan (A206) as well as in 2008 on the 102nd CATSJ Meeting at Nagoya, Japan (3K03).

  • 5 Dijksman A. Elzinga JM. Li Y.-X. Arends IWCE. Sheldon RA. Tetrahedron: Asymmetry  2002,  13:  879 
    CrossrefGoogle Scholar
  • 6a Bennett MA. Matheson TW. Robertson GB. Smith AK. Tucker PA. Inorg. Chem.  1980,  19:  1014 
    Google Scholar
  • 6b Bennett MA. Huang T.-N. Matheson TW. Smith AK. Inorg. Synth.  1982,  21:  74 
    Google Scholar
  • 7a Ishibashi H. Uegaki M. Sakai M. Synlett  1997,  915 
    Google Scholar
  • 7b Ishibashi H. Uegaki M. Sakai M. Takeda Y. Tetrahedron  2001,  57:  2115 
    Google Scholar
  • 7c Carroll FI. White JD. Wall ME. J. Org. Chem.  1963,  28:  1236 
    Google Scholar
  • 9a Hashiguchi S. Fujii A. Takehara J. Ikariya T. Noyori R. J. Am. Chem. Soc.  1995,  117:  7562 
    Google Scholar
  • 9b Haack KJ. Hashiguchi S. Fujii A. Ikariya T. Noyori R. Angew. Chem., Int. Ed. Engl.  1997,  36:  285 
    Google Scholar
  • 9c Takehara J. Hashiguchi S. Fujii A. Inoue S.-I. Ikariya T. Noyori R. Chem. Commun.  1996,  233 
    Google Scholar
  • 10a Fujii A. Hashiguchi S. Uematsu N. Ikariya T. Noyori R. J. Am. Chem. Soc.  1996,  118:  2521 
    Google Scholar
  • 10b Palmer M. Walsgrove T. Wills M. J. Org. Chem.  1997,  62:  5226 
    Google Scholar
  • 10c Alonso DA. Nordin SJM. Roth P. Tarnai T. Andersson PG. Thommen M. Pittelkow U. J. Org. Chem.  2000,  65:  3116 
    Google Scholar
  • 13a

    Details will be reported separately.

  • 13b

    Preparation of ( S , S )-15e
    A mixture of [RuCl2 (hmb)]2 (314.5 mg, 0.470 mmol), (S)-2e˙HCl (143.1 mg, 0.931 mmol), and KOt-Bu (157.1 mg, 1.40 mmol) in CH2Cl2 (6 mL) was stirred at r.t. for 12 h. Removal of the solvent under reduced pressure gave a dark yellow powder, which was washed with THF and then extracted with CH2Cl2. The extract was concentrated in vacuo to give a red solid, which was purified by recrys-tallization from MeOH and Et2O to give pure (S,S)-15e as red crystals (258.0 mg, 63%). ¹H NMR (300 MHz, CD2Cl2, 300 K): δ = 1.81-1.90 (m, 5 H), 1.98-2.10 (m, 4 H), 2.02 (s, 18 H), 2.11 (s, 18 H), 2.02-2.32 (m, 5 H), 2.69-2.72 (m, 2 H), 2.88-2.90 (m, 1 H), 3.25-3.27 (m, 1 H), 3.81-3.83 (m, 1 H), 6.07 (br s, 1 H), 9.61 (br s, 1 H), 10.32 (br s, 1 H). ¹³C{¹H} NMR (75 MHz, CO2Cl2, 300 K): δ = 15.3, 15.6, 24.0, 26.6, 27.2, 27.6, 30.8, 45.1, 50.1, 52.8, 58.5, 75.0, 95.3, 96.0. Anal. Calcd for C34H57Cl3N2Ru2S2×5/2H2O: C, 44.8; H, 6.86; N, 3.07. Found: C, 44.74; H, 6.94; N, 3.20. CCDC-717904 contains the supplementary crystallographic data
    for (S,S)-15e. These data can be obtained free of charge
    from the Cambridge Crystallographic Data Centre via
    http://www.ccdc.cam.ac.uk/data_request/cif.

  • 14 Koike T. Ikariya T. Adv. Synth. Catal.  2004,  346:  37 
    CrossrefGoogle Scholar
  • 15a

    Yield 95%, based on (S)-4-phenyl-2-oxazolidinone. ¹H NMR (300 MHz, CDCl3, 300 K): δ = 1.21 (br s, 2 H), 2.53 (dd, J = 13.3, 9.0 Hz, 1 H), 2.68 (dd, J = 13.3, 4.2 Hz, 1 H), 3.61 (s, 2 H), 3.94 (dd, J = 9.0, 4.2 Hz, 1 H), 7.18-7.27
    (m, 10 H).

  • 15b

    Yield 25%, based on (S)-4-isopropyl-2-oxazolidinone. ¹H NMR (300 MHz, CDCl3, 300 K):
    δ = 0.83-0.86 (m, 6 H), 1.28 (br s, 2 H), 1.54-1.65 (m, 1 H), 2.24 (dd, J = 13.6, 3.7 Hz, 1 H), 2.56-2.61 (m, 2 H), 3.69 (s, 2 H), 7.18-7.30 (m, 5 H).

  • 15c

    Yield 82%, based on (S)-4-benzyl-2-oxazolidinone. ¹H NMR (300 MHz, CDCl3, 300 K): δ = 1.27 (br s, 2 H), 2.34 (dd, J = 13.2, 8.3 Hz, 1 H), 2.56-2.62 (m, 2 H), 2.73 (dd, J = 13.2, 5.6 Hz, 1 H), 3.04-3.12 (m, 1 H), 3.69 (s, 2 H), 7.16-7.30 (m, 10 H).

  • 15d

    Yield 81%, based on N,O-carbonyl-l-prolinol.³d ¹H NMR (300 MHz, CDCl3, 300 K): δ = 1.31-1.43 (m, 1 H), 1.67-1.93 (m, 4 H), 2.49-2.53 (m, 2 H), 2.82-2.88 (m, 1 H), 2.92-3.00 (m, 1 H), 3.13-3.22 (m, 1 H), 3.74 (s, 2 H), 7.21-7.31 (m, 5 H).

  • 16a Bruk YA. Derzhavets AA. Pavlova LV. Rachinskii FY. Slavachevskaya NM. J. Gen. Chem. USSR  1970,  40:  2300 
    Google Scholar
  • 16b Meinzer A. Breckel A. Thaher BA. Manicone N. Otto H.-H. Helv. Chim. Acta  2004,  87:  90 
    Google Scholar
  • 16c Myllymäki VT. Lindvall MK. Koskinen AMP. Tetrahedron  2001,  57:  4629 
    Google Scholar
  • 16d Handrick GR. Atkinson ER. Granchelli FE. Bruni RJ. J. Med. Chem.  1965,  8:  762 
    Google Scholar
  • 16e Schwenkkraus P. Otto H.-H. Arch. Pharm.  1990,  323:  93 
    Google Scholar
  • 16f Chi DY. O’Neil JP. Anderson CJ. Welch MJ. Katzenellenbogen JA. J. Med. Chem.  1994,  37:  928 
    Google Scholar
  • 16g Franzen V. Chem. Ber.  1957,  90:  2036 
    Google Scholar
  • 16h Searles S. Roelofs GE. Tamres M. McDonald RN. J. Org. Chem.  1965,  30:  3443 
    Google Scholar
8

The rate difference between enantiomeric 1 became more significant with the catalyst system with (S)-2e. Thus, it reduced the ee value of (S)-1 (>99% ee) to 13% within 6 h but that of (R)-1 (>99% ee) did not change significantly (94%) under identical conditions.

11

In contrast with the outcome in entry 1 of Table  [¹] , (S)-1 with moderate ee (61%) was obtained from 3 in lower yield (38%) with the binary catalyst system of [RuCl2 (hmb)]2 and (S)-pipecolinol with under otherwise identical conditions.

12

The catalyst system of [RuCl2 (η6-p-cymene)]2 and (S)-2f˙HCl promoted the ATH of 3 to give (S)-1 with 12% ee in 31% yield and that with [RuCl2 (η6-benzene)]2 and (S)-2f˙HCl hardly promoted the ATH of 3 to give rac-1 in 4% yield under otherwise identical conditions.