LETTER
Palladium(II)-Catalyzed Synthesis of 2-Alkoxytetrahydrofurans
3113
References and Notes
H
Ph
H
(1) (a) Hosokawa, T.; Murahashi, S.-I. In Handbook of
Organopalladium Chemistry for Organic Synthesis, Vol. 2;
Negishi, E.-i., Ed.; John Wiley and Sons: New York, 2002,
2141–2192. (b) Hosokawa, T.; Murahashi, S.-I. Acc. Chem.
Res. 1990, 23, 45. (c) Henry, P. M. In Handbook of
Organopalladium Chemistry for Organic Synthesis, Vol. 2;
Negishi, E.-i., Ed.; John Wiley and Sons: New York, 2002,
2119–2139.
H
H
Ph
H
3
2
2
5
H
OEt
OEt
O
O
(Z)-4
(E)-5
Figure 3
(2) (a) Fugami, K.; Oshima, K.; Utimoto, K. Tetrahedron Lett.
1987, 28, 809. (b) See also: Fugami, K.; Oshima, K.;
Utimoto, K. Bull. Chem. Soc. Jpn. 1989, 62, 2050.
(c) Kraus, G. A.; Thurston, J. J. Am. Chem. Soc. 1989, 111,
9203. (d) Larock, R. C.; Lee, N. H. J. Am. Chem. Soc. 1991,
113, 7815. (e) Evans, M. A.; Morken, J. P. Org. Lett. 2005,
7, 3367. (f) Evans, M. A.; Morken, J. P. Org. Lett. 2005, 7,
3371. (g) Scarborough, C. C.; Stahl, S. S. Org. Lett. 2006, 8,
3251.
(8) (a) Bräse, S.; de Meijere, A. In Handbook of
Organopalladium Chemistry for Organic Synthesis, Vol. 1;
Negishi, E.-i., Ed.; John Wiley and Sons: New York, 2002,
1123–1178. (b) As for recent studies of Pd–H elimination,
see: Lloyd-Jones, G. C.; Slatford, P. A. J. Am. Chem. Soc.
2004, 126, 2690. (c) Zhao, H.; Ariafard, A.; Lin, Z.
Organometallics 2006, 25, 812.
(9) As for the chemistry of Pd–H, see: Grushin, V. V. Chem.
Rev. 1996, 96, 2011.
(3) Minami, T.; Kawamura, Y.; Koga, K.; Hosokawa, T. Org.
Lett. 2005, 7, 5689.
(10) (a) Byström, S. E.; Larsson, E. M.; Åkermark, B. J. Org.
Chem. 1990, 55, 5674. (b) Bäckvall, J.-E.; Hopkins, R. B.;
Grennberg, H.; Mader, M. M.; Awasthi, A. K. J. Am. Chem.
Soc. 1990, 112, 5160; and references cited therein.
(11) (a) Hosokawa, T.; Takano, M.; Murahashi, S.-I. J. Am.
Chem. Soc. 1996, 118, 3990. (b) Lax, J.-Y.; Shi, X.-I.;
Gong, Y.-S.; Dai, L.-X. J. Org. Chem. 1993, 58, 4775.
(c) Ref. 5e.
(12) (a) Speier, G. J. Mol. Catal. 1986, 37, 259. (b) Berreau, L.
M.; Mahapatra, S.; Halfen, J. A.; Houser, R. P.; Young, V.
G. Jr.; Tolman, W. B. Angew. Chem. Int. Ed. 1999, 38, 207;
and references cited therein. (c) Kodera, M.; Kawata, T.;
Kano, K.; Tachi, Y.; Ito, S.; Kojo, S. Bull. Chem. Soc. Jpn.
2003, 76, 1957; and also references cited therein.
(13) The reaction of 3,5-di-tert-butylcatechol (11, 67.0 mg, 0.3
mmol) with Pd(OAc)2 (33.7 mg, 0.15 mmol) and Cu(OAc)2
(27.2 mg, 0.15 mmol) in MeCN (1.5 mL) for 0.5 h under O2
(balloon) at r.t. gave quinone 10 in ca. 98% yield (GC). For
the survey of these points, the use of catechol itself, instead
of 11, was not successful, because the analysis of o-quinone
was difficult because of its instability.
(14) Pd(0) species derived from H–Pd–OAc does not seemingly
participate in the catalysis directly, but is possible to be
converted into Pd(II) by the function of AcOH and O2, see:
(a) Mueller, J. A.; Goller, C. P.; Sigman, M. S. J. Am. Chem.
Soc. 2004, 126, 9724. (b) See also: Steinhoff, B. A.; Guzei,
I. A.; Stahl, S. S. J. Am. Chem. Soc. 2004, 126, 11268.
Although such a catalysis is not necessarily ruled out in the
present case, it seems to be difficult to accommodate the
observed effect of catechol or quinone into it.
(4) In this report, we use the term of stereospecificity as a
classical sense, see: Ward, R. S. Chem. Br. 1991, 803.
(5) (a) Tsuji, J. Palladium Reagents and Catalysts, Innovation
in Organic Synthesis; John Wiley and Sons: New York,
1995, 19–124. (b) Zeni, G.; Larock, R. C. Chem. Rev. 2004,
104, 2285. (c) Nishimura, T.; Uemura, S. Synlett 2004, 201.
(d) Stahl, S. S. Angew. Chem. Int. Ed. 2004, 43, 3400.
(e) Muzart, J. Tetrahedron 2005, 61, 5955. (f) Muzart, J.
Tetrahedron 2005, 61, 9423.
(6) Experimental Procedure for the Preparation of (Z)-2 and
(E)-5.
A suspension of 3-phenyl-2-propyne-1-ol (231 mg, 1.75
mmol) and 5 wt% palladium on CaCO3 poisoned with lead
(Aldrich, 46.1 mg, 0.087 mmol) in toluene (5 mL) was
stirred under H2 (balloon) at r.t. for 2 h, and the reaction
mixture was filtered through a pad of cotton with Et2O (50
mL). Evaporation of solvent gave nearly pure (Z)-2 (202 mg,
86% by NMR) as an oil. 1H NMR (400 MHz, CDCl3):
d = 4.45 (d, J = 6 Hz, 2 H), 5.88 (dt, J = 6.4 Hz, 1 H), 6.58
(d, J = 12 Hz, 1 H), 7.19–7.45 (m, 5 H).
A 25-mL side-armed round-bottom flask was charged with
Pd(OAc)2 (11.2 mg, 0.05 mmol), Cu(OAc)2 (9.1 mg, 0.05
mmol), and catechol (11.0 mg, 0.10 mmol) to which was
added MeCN (0.5 mL) under O2 (balloon). The resulting
solution was stirred for 0.5 h at r.t., and ethyl vinyl ether (288
mg, 4.0 mmol) was added to the flask, and subsequently a
solution of (Z)-2 (134 mg, 1.0 mmol) in MeCN (0.5 ml) was
added. After stirring was continued for 3 h at r.t., the reaction
mixture was filtered through Florisil column (3 g, 10
mm × 80 mm, EtOAc–n-hexane, 1:20), and the solvent was
evaporated under reduced pressure. The product (E)-5,
nearly pure by NMR, was obtained in 77% yield (157 mg,
0.77 mmol) as an oil. Further purification was made by TLC
on SiO2. (E)-5; Rf = 0.45 (EtOAc–n-hexane, 1:20). 1H NMR
(400 MHz, CDCl3): d = 1.20 (t, J = 7.2 Hz, 3 H), 2.84 (d,
J = 16.8 Hz, 1 H), 2.91–2.98 (dm, 1 H), 3.50 (dq, J = 7.2 Hz,
1 H), 3.78 (dq, J = 7.2 Hz, 1 H), 4.54 (d, J = 12.8 Hz, 1 H),
4.63 (d, J = 12.8 Hz, 1 H), 5.36 (d, J = 5.2 Hz, 1 H), 6.38 (s,
1 H), 7.18–7.36 (m, 5 H).
(15) (a) Keith, J. M.; Nielsen, R. J.; Oxgaard, J.; Goddard, W. A.
III J. Am. Chem. Soc. 2005, 127, 13172. (b) Privalov, T.;
Linde, C.; Zetterberg, K.; Moberg, C. Organometallics
2005, 24, 885. (c) Denney, M. C.; Smythe, N. A.; Cetto, K.
L.; Kemp, R. A.; Goldberg, K. I. J. Am. Chem. Soc. 2006,
128, 2508.
(16) Experimental Procedure for the Preparation of (E)-4 in
a Relatively Large Scale.
In a 25-mL side-armed round-bottomed flask, Pd(OAc)2
(65.1 mg, 0.25 mmol), Cu(OAc)2 (45.4 mg, 0.25 mmol), and
catechol (55.0 mg, 0.50 mmol) were dissolved in MeCN (2.5
mL) under O2 (balloon). After the mixture was stirred for 0.5
h at r.t. (aging time of catalyst), ethyl vinyl ether (1442 mg,
20 mmol) was added to the flask, and a solution of (E)-3-
phenyl-2-propen-1-ol (670 mg, 5.0 mmol) in MeCN (2.5
mL) was then added. The reaction mixture was stirred for
7 h at r.t. In order to determine GC yield of 4, tetraethylene
glycol dimethyl ether (63.43 mg) was added to the flask as
(7) NOE correlation of vinyl proton (d = 6.42 ppm) in (Z)-4 was
observed with one of C-3 protons (d = 2.70 ppm), suggesting
that these protons are proximal to each other, but not with
C-5 protons. On the other hand, vinyl proton (d = 6.38 ppm)
in (E)-5 correlates with one of C-5 protons (d = 4.54 ppm),
but not with C-3 protons (Figure 3).
Synlett 2006, No. 18, 3110–3114 © Thieme Stuttgart · New York