D. Yamanaka et al. / Tetrahedron Letters 49 (2008) 53–56
55
Ph
.
Fe(ClO4)3 6H2O
+
(2
R
*, 2'
R
*)-3 + PhCH2OH
THF
OCH2Ph
O
O
OCH2Ph
1b
4
Scheme 2.
PhCH2OH
4
+
O
Ph
Fe3+
3
O
O
O
-Fe3+
Ph
Ph
H+
PhCH2OH / Fe3+
Fe3+
1b
-
O
OH
O
O
2a
Scheme 3.
8. Bartoli, G.; Bosco, M.; Locatelli, M.; Marcantoni, E.;
Melchiorre, P.; Sambri, L. Org. Lett. 2005, 7, 427–
430.
9. (a) Minami, K.; Kawamura, Y.; Koga, K.; Hosokawa, T.
Org. Lett. 2005, 7, 5689–5692; (b) Kawamura, Y.; Imai,
T.; Hosokawa, T. Synlett 2006, 3110–3114.
Morken and Duenes have recently shown that 2-alkoxy-
˜
4-vinyl-tetrahydrofurans undergo facile Lewis acid cata-
lyzed diastereoselective transacetalization with other
nucleophiles such as allylsilane.20 Combined with their
success, our present results prove a synthetic mobility
of acetal unit in 1. In addition, we believe that the pres-
ent method must contribute to the synthetic chemistry
of furanoside and pyranoside acetals related to
carbohydrates.
10. Hosokawa, T.; Sazuka, M.; Minami, K.; Kawamura, Y.
Unpublished result.
11. Fe(ClO4)3Æ6H2O (22.8 mg, 0.05 mmol) was placed in a
25 mL side-armed round bottomed flask under Ar, and a
solution of (Z)-4-benzylidene-2-ethoxytetrahydrofuran
(1a) (102 mg, 0.5 mmol) and benzyl alcohol (0.25 mL,
2.5 mmol) in THF (2.0 mL) was added. After the reaction
mixture was stirred for 2 h at room temperature, the
mixture was filtered through silica gel column
(15 mm · 60 mm 5 g, diethyl ether 100 mL), and the
solvent was evaporated under reduced pressure to give
1b with unreacted benzyl alcohol and 1a. The yield of 1b
was determined to be 79% by NMR from this mixture. In
a separate experiment, isolation of 1b was performed by
Kugelrohr distillation (40–80 ꢁC/5 mm Hg), which affor-
ded pure 1b (80 mg, 0.3 mmol) in 60% yield. 1b: 1H NMR
(400 MHz, CDCl3): d 2.78 (dm, J = 16.4 Hz, 1H), 2.95
(dm, J = 16.4 Hz, 1H), 4.54 (d, J = 12.0 Hz, 1H), 4.72–
4.74 (m, 2H), 4.75 (d, J = 12.0 Hz, 1H), 5.31 (d,
J = 4.8 Hz, 1H), 6.41–6.44 (m, 1H), 7.13 (d, J = 7.5 Hz,
2H), 7.21 (t, J = 7.5 Hz, 1H), 7.26–7.36 (m, 5H), 7.33 (t,
J = 7.5 Hz, 2 H); 13C NMR (101 MHz, CDCl3): d 41.06,
68.08, 68.69, 101.34, 121.69, 126.48, 127.58, 127.81,
127.92, 128.37, 128.44, 137.33, 137.94, 138.81; FTIR
(KBr, cmꢁ1): 3048, 2913, 2863, 1595, 1491, 1448, 1421,
1364, 1258, 1199, 1166, 1076, 1037, 1008, 993, 969, 755;
GCMS m/z: 266 (M+).
In summary, Fe(ClO4)3 serves as an effective catalyst
for the transacetalization of 2-alkoxy-4-benzylidene-
tetrahydrofurans 1 with various alcohols under mild
conditions. In this reaction, water can be used as a
nucleophile to give the corresponding 2-hydroxy-
tetrahydrofurans 2.
References and notes
1. (a) Bolm, C.; Legros, J.; Le Paih, J.; Zani, L. Chem. Rev.
2004, 104, 6217–6254; (b) Diaz, D. D.; Miranda, P. O.;
Padron, J. I.; Martin, V. S. Curr. Org. Chem. 2006, 10,
457–476.
2. (a) Salehi, P.; Iranpoor, N.; Behbahani, F. K. Tetrahedron
1998, 54, 943–948; (b) Pelzer, S.; Kauf, T.; van Wullen, C.;
¨
Christoffers, J. J. Organomet. Chem. 2003, 684, 308–314.
3. It is reported that such a reputation is due to the mistaken
association of metallic perchlorates with the oxidizing
potential of perchloric acid and the pyrotechnic perfor-
mances of NH4ClO4 (Bartoli, G.; Locatelli, M.; Melchi-
orre, P.; Sambri, L. Eur. J. Org. Chem. 2007, 2037–2049,
and also see: Bartoli, G.; Sambri, L.; Locatelli, M. J.
Fudan University, Natl. Sci. 2005, 44, 650–651).
12. 2-Pyranoxytetrahydrofurans 3 were prepared from com-
mercially available 2-vinyloxytetrahydropyran and
cinnamyl alcohol by using palladium(II) catalyst, and
the diastereomers of (2R*,20R*) and (2R*,20S*)-3 were
separated by TLC, as reported previously see: Ref. 9a.
4. Bartoli, G.; Bosco, M.; Dalpozzo, R.; Marcantoni, E.;
Massaccesi, M.; Sambri, L. Eur. J. Org. Chem. 2003,
4611–4617.
1
13. Compound 2a: H NMR (400 MHz, CDCl3): d 2.73 (dm,
5. (a) Gooßen, L.; Do¨hring, A. Adv. Synth. Catal. 2003, 345,
943–947; As for simple esterification of carboxylic acids,
see: (b) Bartoli, G.; Boeglin, J.; Bosco, M.; Locatelli, M.;
Massaccesi, M.; Melchiorre, P.; Sambri, L. Adv. Synth.
Catal. 2005, 347, 33–38.
6. Bartoli, G.; Bosco, M.; Locatelli, M.; Marcantoni, E.;
Melchiorre, P.; Sambri, L. Synlett 2004, 239–242.
7. Heravi, M. M.; Behbahani, F. K.; Oskooie, H. A.; Shoar,
R. H. Tetrahedron Lett. 2005, 46, 2543–2545.
J = 16.3 Hz, 1 H), 2.81 (br s, 1H), 2.96 (dm, J = 16.3 Hz,
1H), 4.71 (dq, J = 13.8, 2.1 Hz, 1H), 4.82 (dm, J =
13.8 Hz, 1H), 5.63 (dd, J = 4.8, 2.5 Hz, 1H), 6.45–6.49
(m, 1H), 7.13 (d, J = 7.5 Hz, 2H), 7.21 (t, J = 7.5 Hz, 1H),
7.34 (t, J = 7.5 Hz, 2H); 13C NMR (101 MHz, CDCl3): d
41.84, 68.18, 96.93, 122.31, 126.64, 127.86, 128.48, 137.15,
138.17; GCMS m/z: 190 (M+).
14. The essentially same result was obtained even by using a
mixture of (2R*,20R*) and (2R*,20S*)-3 (87:13).