1076
N. Hamada et al.
LETTER
(5) Sumida, N.; Nishioka, K.; Sato, T. Synlett 2001, 1921.
(6) Other lithium salts and alkali metal tetrafluoroborates are
less effective than LiBF4 in our reaction system. The
reaction of benzaldehyde under the identical conditions is as
follows: LiCl (19%), LiBr (15%), LiClO4 (36%), LiOTf
(35%), NaBF4 (8%), KBF4 (3%).
(7) Gandini, A. Adv. Polym. Sci. 1977, 25, 47.
(8) Dimethyl acetalization of citronellal using electrogenerated
acid afforded 6-methoxy-3,7-dimethyl-7-octenal dimethyl
acetal (18%) as a by-product: Gora, J.; Smigielski, K.; Kula,
J. Synthesis 1986, 586.
Table 3 LiBF4-Catalyzed Diethyl Acetalization of Carbonyl
Compoundsa
Entry
R1R2C=O
Time (h)
Yield (%)b
92c
1
2
3
4
1
2
5
1
PhCHO
100c,d
83e
CHO
CHO
CHO
Ph
Ph
79e
(9) Thurkauf, A.; Jacobson, A. E.; Rice, K. C. Synthesis 1988,
233.
HO
(10) Both methanol and trimethyl orthformate were necessary in
order to obtain the products in satisfactory yields. On the
reaction of benzophenone (3 mmol) using LiBF4 (0.3 mmol):
HC(OMe)3 (3.9 mmol) alone (90 °C, 19 h, 15%); MeOH
(1.5 cm3) alone (reflux, 19 h, 2%).
(11) (a) Tirado-Rives, J.; Gandour, R. D. Org. Prep. Proced. Int.
1985, 17, 62. (b) Ma, S.; Venanzi, L. M. Synlett 1993, 751;
and references cited therein.
(12) For the success acetalization of carbonyl compounds in the
presence of THP ethers, see: (a) Hwu, J. R.; Leu, L.-C.;
Robl, J. A.; Anderson, D. A.; Wetzel, J. M. J. Org. Chem.
1987, 52, 188. (b) Karimi, B.; Ebrahimian, G. R.; Seradj, H.
Org. Lett. 1999, 1, 1737. (c) Karimi, B.; Golshani, B.
Synthesis 2002, 784.
(13) Patwardhan, S. A.; Dev, S. Synthesis 1974, 348.
(14) (a) Firouzabadi, H.; Iranpoor, N.; Karimi, B. Synth.
Commun. 1999, 29, 2255; and references cited therein.
(b) Firouzabadi, H.; Iranpoor, N.; Karimi, B. Synlett 1999,
321. (c) Karimi, B.; Seradj, H.; Ebrahimian, G.-R. Synlett
1999, 1456.
5f
4
74c
O
n-Bu
6
0.5
4
77c
81c
71e
O
7f
O
O
Ph
Ph
8f,g
6
Ph
a Reaction conditions: R1R2C=O (5 mmol), HC(OEt)3 (6.5 mmol),
LiBF4 (0.15 mmol), anhyd EtOH (2.5 cm3), 40 °C, unless otherwise
mentioned.
b Isolated yields.
c Purified by kugelrohr distillation.
d Z/E = 0:100.
e Purified by column chromatography.
f LiBF4 (10 mol%) was used.
(15) The spectroscopic data of new compounds are shown as
follows.
g At reflux temperature.
4-(Methoxymethoxy)benzaldehyde Dimethyl Acetal: 1H
NMR (CDCl3): d = 3.32 (s, 6 H), 3.48 (s, 3 H), 5.18 (s, 2 H),
5.35 (s, 1 H), 7.03 (d, J = 8.85 Hz, 2 H), 7.36 (d, J = 8.85 Hz,
2 H). 13C NMR (CDCl3): d = 52.6, 56.0, 94.4, 103.0, 115.9,
127.9, 131.6, 157.3.
References
(1) (a) Loewenthal, H. J. E. In Protective Groups in Organic
Chemistry; McOmie, J. F. W., Ed.; Plenum: London, 1973,
Chap. 9. (b) Kocienski, P. J. In Protecting Groups; Thieme:
Stuttgart, 1994, Chap. 5. (c) Greene, T. W.; Wuts, P. G. M.
In Protective Groups in Organic Synthesis, 3rd ed.; Wiley:
New York, 1999, Chap. 4.
(2) (a) Schmitz, E.; Eichhorn, I. In The Chemistry of the Ether
Linkage; Patai, S., Ed.; Wiley: New York, 1967, Chap. 7.
(b) Mukaiyama, T.; Murakami, M. Synthesis 1987, 1043.
(c) Alexakis, A.; Mangeney, P. Tetrahedron: Asymmetry
1990, 1, 477.
(3) (a) Meskens, F. A. J. Synthesis 1981, 501. (b) Leonard, N.
M.; Oswald, M. C.; Freiberg, D. A.; Nattier, B. A.; Smith, R.
C.; Mohan, R. S. J. Org. Chem. 2002, 67, 5202; and
references cited therein. (c) Gopinath, R.; Haque, S. J.;
Patel, B. K. J. Org. Chem. 2002, 67, 5842. (d) Basu, M. K.;
Samajdar, S.; Becker, F. F.; Banik, B. K. Synlett 2002, 319.
(4) For recent leading references, see: (a) Kazemi, F.; Kiasat,
A. R.; Ebrahimi, S. Synth. Commun. 2003, 33, 999.
(b) Yadav, J. S.; Reddy, B. V. S.; Vishnumurthy, P.
Tetrahedron Lett. 2003, 44, 5691.
4-(2-Methoxyethoxy)benzaldehyde Dimethyl Acetal: 1H
NMR (CDCl3): d = 3.32 (s, 6 H), 3.37 (s, 3 H), 3.53–3.57 (m,
2 H), 3.80–3.84 (m, 2 H), 5.27 (s, 2 H), 5.34 (s, 1 H), 7.05 (d,
J = 8.70 Hz, 2 H), 7.36 (d, J = 8.70 Hz, 2 H). 13C NMR
(CDCl3): d = 52.6, 59.0, 67.6, 71.6, 93.4, 103.0, 115.9,
127.9, 131.6, 157.3.
4-(Perhydro-2H-pyran-2-yloxymethyl)benzaldehyde
Dimethyl Acetal: 1H NMR (CDCl3): d = 1.49–1.92 (m, 6 H),
3.33 (s, 6 H), 3.52–3.56 (m, 1 H), 3.89–3.95 (m, 1 H), 4.51
(d, J = 12.2 Hz, 1 H), 4.70 (t, J = 3.35 Hz, 1 H), 4.79 (d,
J = 12.2 Hz, 1 H), 5.39 (s, 1 H), 7.37 (d, J = 7.95 Hz, 2 H),
7.43 (d, J = 7.95 Hz, 2 H). 13C NMR (CDCl3): d = 19.4, 25.5,
30.6, 52.7, 62.1, 68.5, 97.8, 103.1, 126.7, 127.6, 137.3,
138.6.
4-(5,5-Dimethyl-1,3-dioxan-2-yl)benzaldehyde Dimethyl
Acetal: 1H NMR (CDCl3): d = 0.80 (s, 3 H), 1.30 (s, 3 H),
3.29 (s, 6 H), 3.65 (d, J = 10.9 Hz, 2 H), 3.77 (d, J = 10.9 Hz,
2 H), 5.40 (s, 1 H), 5.41 (s, 1 H), 7.46 (d, J = 8.25 Hz, 2 H),
7.51 (d, J = 8.25 Hz, 2 H). 13C NMR (CDCl3): d = 21.9, 23.0,
30.2, 52.4, 77.7, 101.5, 102.6, 126.0, 126.7, 138.6.
Synlett 2004, No. 6, 1074–1076 © Thieme Stuttgart · New York