LETTER
Synthesis of Warfarin Derivatives and Analogues
1553
(7) (a) Rueping, M.; Nachtsheim, B. J.; Kuenkel, A. Org. Lett.
2007, 9, 825. (b) Rueping, M.; Nachtsheim, B. J.; Kuenkel,
A. Synlett 2007, 1391. (c) For a review on catalytic Friedel–
Crafts alkylations, see: Rueping, M.; Nachtsheim, B. J.
Beilstein J. Org. Chem. 2010, 6, No. 6.
(8) For reviews, see: (a) Leonard, N. M.; Wieland, L. C.;
Mohan, R. S. Tetrahedron 2002, 58, 8373. (b) Gaspard-
Iloughmane, H.; Le Roux, C. Eur. J. Org. Chem. 2004,
2517.
(12) Wabnitz, T. C.; Yu, J. Q.; Spencer, J. B. Chem. Eur. J. 2004,
10, 484.
(13) (a) Tschan, M. J. L.; Thomas, C. M.; Strub, H.; Carpentier,
J. F. Adv. Synth. Catal. 2009, 351, 2496. (b) For TfOH-
catalyzed hydroaminations and hydroalkoxylations, see:
Rosenfeld, D. C.; Shekhar, S.; Takemiya, A.; Utsunomiya,
M.; Hartwig, J. F. Org. Lett. 2006, 8, 4179.
(14) A General Procedure for the Bismuth(III)-Catalyzed
Benzylation of 4-Hydroxycoumarin
(9) (a) Rueping, M.; Nachtsheim, B. J.; Ieawsuwan, W. Adv.
Synth. Catal. 2006, 348, 1033. (b) Rueping, M.;
In a typical experiment 4-hydroxycoumarin (1 mmol) and
Bi(OTf)3 (H2O)4 (0.005 mmol, 0.5 mol%) were suspended in
DCE (5 mL) and heated to 90 °C. Subsequently, 1-phenyl-
ethanol dissolved in DCE (1 mL) was added (2.5 mmol)
dropwise over 4 h. The resulting clear solution was allowed
to cool down to r.t., the solvent evaporated under vacuum,
and the crude mixture purified by column chromatography
(hexane–EtOAc, 3:1) to afford 248 mg (89%) of 2a.
Selected Data
Nachtsheim, B. J.; Scheidt, T. Org. Lett. 2006, 8, 3717.
(10) Examples of bismuth triflate catalyzed reactions:
(a) Ollevier, T.; Lavie-Compin, G. Tetrahedron Lett. 2004,
45, 49. (b) Ollevier, T.; Mwene-Mbeja, T. M. Tetrahedron
2008, 64, 5150. (c) Ollevier, T.; Nadeau, E. Tetrahedron
Lett. 2008, 49, 1546. (d) Ollevier, T.; Bouchard, J. E.;
Desyroy, V. J. Org. Chem. 2008, 73, 331. (e) Ollevier, T.;
Nadeau, E. Org. Biomol. Chem. 2007, 5, 3126. (f) Ollevier,
T.; Mwene-Mbeja, T. M. Synthesis 2006, 3963.
Compound 2a: white amorphous solid. 1H NMR (250 MHz,
CDCl3): d = 7.76–7.66 (m, 1 H), 7.62–7.47 (m, 5 H), 7.44–
7.22 (m, 3 H), 6.02 (s, 1 H), 4.85–4.72 (q, J = 7.3 Hz, 1 H),
1.72 (d, J = 7.3 Hz, 3 H). 13C NMR (75 MHz, CDCl3): d =
163.4, 159.6, 152.5, 141.5, 131.8, 129.9, 128.0, 127.3,
123.8, 122.9, 116.4, 116.1, 110.1, 34.6, 16.5. IR (neat):
n = 3231 (b), 1669, 1610, 11216, 753 cm–1. MS (EI): m/z (%)
= 266.1 (100)[M]+, 251.1 (48) [M – CH3]+, 189.1 (7) [M –
C6H5]+. Anal. Calcd for C17H14O3: C, 76.68; H, 5.30. Found:
C, 76.84; H, 5.51.
(g) Desmurs, J. R.; Labrouillere, M.; LeRoux, C.; Gaspard,
H.; Laporterie, A.; Dubac, J. Tetrahedron Lett. 1997, 38,
8871. (h) Peterson, K. E.; Smith, R. C.; Mohan, R. S.
Tetrahedron Lett. 2003, 44, 7723. (i) Wieland, L. C.; Zerth,
H. M.; Mohan, R. S. Tetrahedron Lett. 2002, 43, 4597.
(j) Le Roux, C.; Dubac, J. Synlett 2002, 181. (k) Repichet,
S.; Le Roux, C.; Hernandez, P.; Dubac, J. J. Org. Chem.
1999, 64, 6479. (l) Repichet, S.; Le Roux, C.; Dubac, J.;
Desmurs, J. R. Eur. J. Org. Chem. 1998, 2743.
Compound 2b: white amorphous solid. 1H NMR (250 MHz,
CDCl3): d = 7.77–7.70 (m, 1 H), 7.63–7.53 (m, 3 H), 7.44–
7.26 (m, 4 H), 6.00 (s, 1 H), 4.72 (q, J = 7.3 Hz, 1 H), 1.71
(d, J = 7.3 Hz, 3 H). 13C NMR (63 MHz, CDCl3): d = 163.3,
159.6, 152.6, 140.7, 132.7, 132.1, 129.1, 124.0, 122.8,
116.5, 115.9, 109.7, 34.1, 16.6. IR (neat): n = 3436 (br),
1716, 1660, 1605, 1203, 754 cm–1. MS (EI): m/z (%) =
344.0(100) [M]+, 345.0(22) [M]+, 346.0(97) [M]+, 347.0(18)
[M]+. Anal. Calcd for C17H13BrO3: C, 59.15; H, 3.80. Found:
C, 58.91; H, 3.90.
(m) Le Roux, C.; Ciliberti, L.; Laurent-Robert, H.;
Laporterie, A.; Dubac, J. Synlett 1998, 1249.
(n) Rubenbauer, P.; Bach, T. Tetrahedron Lett. 2008, 49,
1305. (o) Rubenbauer, P.; Herdtweck, E.; Strassner, T.;
Bach, T. Angew. Chem. Int. Ed. 2008, 47, 10106.
(11) (a) Yamamoto, H.; Futatsugi, K. Angew. Chem. Int. Ed.
2005, 44, 1924. (b) Salvador, J. A. R.; Pinto, R. M. A.;
Santos, R. C.; Le Roux, C.; Beja, A. M.; Paixao, J. A. Org.
Biomol. Chem. 2009, 7, 508.
Synlett 2010, No. 10, 1549–1553 © Thieme Stuttgart · New York