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Synlett 2007(19): 3050-3054  
DOI: 10.1055/s-2007-990963
LETTER
© Georg Thieme Verlag Stuttgart · New York

Reusable Scandium/Ionic Liquid Catalyst System for Sequential C-C and C-O Bond Formations between Phenols and Dienes with Atom Economy

So Won Youn
Department of Chemistry, Pukyong National University, Busan 608737, Korea
Fax: +82(51)6288147; e-Mail: sowony@pknu.ac.kr;
Further Information

Publication History

Received 7 September 2007
Publication Date:
08 November 2007 (online)

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Abstract

Mild, efficient, and atom economical sequential C-C/C-O bond formations between phenols and dienes using the reusable catalyst system, Sc(OTf)3-[bmim][PF6], have been developed to afford in good yields a variety of dihydrobenzopyran and dihydrobenzofuran ring systems, which are important motifs in both naturally occurring and biologically active compounds. In these reactions the ionic liquid acts as not only an efficient additive but also an immobilizing agent for facilitating catalyst recycling.

Key words

heterocycles - bicyclic compounds - annulations - scandium - ionic liquids

    References and Notes

  • 1a Bioactive Compounds from Natural Sources   Tringali C. Taylor & Francis; New York: 2001. 
    Google Scholar
  • 1b The Chemistry of Heterocyclic Compounds   Vol. 36:  Ellis GP. Lockhart IM. John Wiley-Interscience; New York: 1981. 
    Google Scholar
  • 2a Nichols DE. Hoffman AJ. Oberlender RA. Riggs RA. J. Med. Chem.  1986,  29:  302 
    CrossrefGoogle Scholar
  • 2b Harwood LM.
    J. Chem. Soc., Chem. Commun.  1983,  530 
    CrossrefGoogle Scholar
  • 3a For Ir-catalyzed tandem Claisen rearrangement and intramolecular hydroaryloxylation of allyl aryl ethers, see: Grant VH. Liu B. Tetrahedron Lett.  2005,  46:  1237 ; and references therein
    CrossrefGoogle Scholar
  • 3b For transition-metal-catalyzed cyclization of 2-allylphenols, see: Hori K. Kitagawa H. Miyoshi A. Ohta T. Furukawa I. Chem. Lett.  1998,  1083 
    CrossrefGoogle Scholar
  • 4 Youn SW. Pastine SJ. Sames D. Org. Lett.  2004,  6:  581 
    Google Scholar
  • 5 Yadav JS. Reddy BVS. Parisse C. Carvalho P. Rao TP. Tetrahedron Lett.  2002,  43:  2999 ; and references therein
    CrossrefGoogle Scholar
  • 6 Youn SW. Eom JI. J. Org. Chem.  2006,  71:  6705 
    CrossrefGoogle Scholar
  • 7 For one-pot synthesis of dihydrobenzopyrans by the reactions of phenols with dienes using Amberlyst 15 as a reusable catalyst, see: Cichewicz RH. Kenyon VA. Whitman S. Morales NM. Arguello JF. Holman TR. Crews P. J. Am. Chem. Soc.  2004,  126:  14910 ; and references therein
    CrossrefGoogle Scholar
  • For recent reviews on ionic liquids, see:
  • 8a Afonso CAM. Branco LC. Candeias NR. Gois PMP. Lourenço NMT. Mateus NMM. Rosa JN. Chem. Commun.  2007,  2669 
    CrossrefPubMedGoogle Scholar
  • 8b Pârvulescu VI. Hardacre C. Chem. Rev.  2007,  107:  2615 
    CrossrefPubMedGoogle Scholar
  • 8c Binnemans K. Chem. Rev.  2007,  107:  2592 
    CrossrefPubMedGoogle Scholar
  • 8d Imperato G. König B. Chiappe C. Eur. J. Org. Chem.  2007,  1049 
    CrossrefPubMedGoogle Scholar
  • 8e Song CE. Yoon MY. Choi DS. Bull. Korean Chem. Soc.  2005,  26:  1321 
    CrossrefPubMedGoogle Scholar
  • 8f Dupont J. de Souza RF. Suarez PAZ. Chem. Rev.  2002,  102:  3667 
    CrossrefPubMedGoogle Scholar
  • 8g Sheldon R. Chem. Commun.  2001,  2399 
    CrossrefPubMedGoogle Scholar
  • 8h Wasserscheid P. Keim W. Angew. Chem. Int. Ed.  2000,  39:  3772 
    CrossrefPubMedGoogle Scholar
  • 8i Welton T. Chem. Rev.  1999,  99:  2071 
    CrossrefPubMedGoogle Scholar
  • For recent related examples of Sc(OTf)3-catalyzed reactions in ionic liquids, see the following. For hydroarylations:
  • 9a Song CE. Jung D. Choung SY. Roh EJ. Lee S. Angew. Chem. Int. Ed.  2004,  43:  6183 
    CrossrefGoogle Scholar
  • 9b Song CE. Shim WH. Roh EJ. Choi JH. Chem. Commun.  2000,  1695 
    CrossrefGoogle Scholar
  • 9c For Claisen rearrangement/cyclization: Zulfiqar F. Kitazume T. Green Chem.  2000,  2:  296 
    CrossrefGoogle Scholar
  • 9d For Diels-Alder reactions: Song CE. Shim WH. Roh EJ. Lee S. Choi JH. Chem. Commun.  2001,  1122 
    CrossrefGoogle Scholar
  • 9e For C-C bond-forming reactions, see: Gu Y. Ogawa C. Kobayashi J. Mori Y. Kobayashi S. Angew. Chem. Int. Ed.  2006,  45:  7217 
    CrossrefGoogle Scholar
  • For dimerization and telomerization of 1,3-butadiene in ionic liquids, see:
  • 10a Silva SM. Suarez PAZ. de Souza RF. Dupont J. Polym. Bull. (Berlin)  1998,  40:  401 
    CrossrefGoogle Scholar
  • 10b Dullius JEL. Suarez PAZ. Einloft S. de Souza RF. Dupont J. Fischer J. Cian AD. Organometallics  1998,  17:  815 
    CrossrefGoogle Scholar
  • 11 Yadav JS. Reddy BVS. Gayathri KU. Prasad AR. Synthesis  2002,  2537 
    Article in Thieme ConnectGoogle Scholar
  • 12a For effect of the structures of ionic liquids on their physical-chemical properties, see: Hu Y.-F. Xu C.-M. Chem. Rev.  2007,  in press
    CrossrefGoogle Scholar
  • 12b

    For effects of the anions, see: refs. 9b and 8c and references therein.
    Crossref
  • 12c For effects of the alkyl chain lengths of the cations, see: Williams DBG. Ajam M. Ranwell A. Organometallics  2006,  25:  3088 ; and ref. 9c
    CrossrefGoogle Scholar
  • 13 For miscibility of organic compounds in [bmim][PF6], see: Blanchard LA. Breunecke JF. Ind. Eng. Chem. Res.  2001,  40:  287 ; and ref. 8f
    CrossrefGoogle Scholar
  • 14 Kim DW. Hong DJ. Seo JW. Kim HS. Kim HK. Song CE. Chi DY. J. Org. Chem.  2004,  69:  3186 
    CrossrefGoogle Scholar
15

General Procedure for the Sc-IL-Catalyzed Reaction of Phenols and Dienes and Catalyst Recycling: To a solution of phenol and diene (2 equiv) in toluene (0.1 M) and [bmim][PF6] (0.5 equiv) was added Sc(OTf)3 (20 mol%). The resulting mixture was stirred at the reported temperature for 18-48 h. The organic(toluene) layer was decanted to leave the ionic liquid phase containing Sc(OTf)3 which was washed with Et2O (3 ×) for extraction of the product. The combined organic layer was concentrated and the residue was purified by column chromatography on silica gel (EtOAc-n-hexanes, 1:20-1:100) to give the corresponding product.
The recovered ionic liquid layer remaining in the vessel was reused without any pre-treatment. For the second cycle, more reactants (phenol and diene) and toluene were added to the recovered ionic liquid layer.
5,7-Dimethoxy-2,2-dimethylchroman (5): Colorless oil (EtOAc-n-hexane, 1:20). 1H NMR (400 MHz, CDCl3): δ = 1.32 (s, 6 H), 1.75 (t, J = 6.8 Hz, 2 H), 2.57 (t, J = 6.8 Hz, 2 H), 3.75 (s, 3 H), 3.78 (s, 3 H), 6.01 (d, J = 2.4 Hz, 1 H), 6.03 (d, J = 2.4 Hz, 1 H). 13C NMR (100 MHz, CDCl3): δ = 16.6, 26.6, 32.4, 55.2, 55.3, 74.2, 90.8, 93.5, 102.4, 155.0, 158.5, 159.3. HRMS (EI): m/z [M]+ calcd for C13H18O3: 222.1256; found: 222.1255.
5,6,7-Trimethoxy-2,2-dimethylchroman (6): Colorless oil (EtOAc-n-hexane, 1:20). 1H NMR (400 MHz, CDCl3): δ = 1.31 (s, 6 H), 1.74 (t, J = 6.8 Hz, 2 H), 2.63 (t, J = 6.8 Hz, 2 H), 3.78 (s, 3 H), 3.80 (s, 3 H), 3.88 (s, 3 H), 6.16 (s, 1 H). 13C NMR (100 MHz, CDCl3): δ = 17.0, 26.6, 32.3, 55.7, 60.5, 61.0, 74.0, 96.5, 106.6, 135.3, 149.9, 151.3, 152.3. HRMS (EI): m/z [M]+ calcd for C14H20O4: 252.1362; found: 252.1364.
2,2,8,8-Tetramethyl-3,4,9,10-tetrahydro-2 H ,8 H -pyrano[2,3- f ]chromene (8) and 2,2,8,8-Tetramethyl-3,4,7,8-tetrahydro-2 H ,6 H -pyrano[3,2- g ]chromene (9): The mixture of isomers was obtained as a colorless oil (8/9 = 3:2, EtOAc-n-hexane, 1:50). Signals corresponding to 8: 1H NMR (400 MHz, CDCl3): δ = 1.32 (s, 3 H), 1.33 (s, 3 H), 1.77 (m, 4 H), 2.62 (t, J = 6.8 Hz, 2 H), 2.70 (t, J = 6.8 Hz, 2 H), 6.34 (d, J = 8.5 Hz, 1 H), 6.80 (d, J = 8.2 Hz, 1 H). 13C NMR (100 MHz, CDCl3): δ = 17.1, 22.0, 26.7, 27.1, 32.4, 32.9, 73.5, 73.9, 108.4, 109.5, 111.3, 127.0, 151.7, 152.8. Signals corresponding to 9: 1H NMR (400 MHz, CDCl3): δ = 1.32 (s, 6 H), 1.77 (m, 4 H), 2.69 (t, J = 6.8 Hz, 4 H), 6.24 (s, 1 H), 6.74 (s, 1 H). 13C NMR (100 MHz, CDCl3): δ = 21.8, 26.8, 33.1, 73.8, 104.7, 112.6, 129.3, 153.1. HRMS (EI): m/z [M]+ calcd for C16H22O2: 246.1620; found: 246.1618.
2,2,8,8,10-Pentamethyl-3,4,7,8-tetrahydro-2 H ,6 H -pyrano[3,2- g ]chromene (10): White solid (EtOAc-n-hexane, 1:50). 1H NMR (400 MHz, CDCl3): δ = 1.33 (s, 12 H), 1.76 (t, J = 6.8 Hz, 4 H), 2.03 (s, 3 H), 2.70 (t, J = 6.8 Hz, 4 H), 6.62 (s, 1 H). 13C NMR (100 MHz, CDCl3): δ = 8.0, 22.1, 27.1, 33.1, 73.5, 111.8, 113.0, 125.8, 150.7. HRMS (EI): m/z [M]+ calcd for C17H24O2: 260.1776; found: 260.1776.