Y. Maeda et al. / Tetrahedron Letters 42 (2001) 8877–8879
8879
k) gave the corresponding ketones in low yields (entries
10–13).
rocas, G.; Ventura, M.; Maestro, M.; Mah´ıa, J.; Villal-
gordo, J. M. Tetrahedron: Asymmetry 2000, 11, 2483–2493;
(e) Wei, H.-X.; Kim, S. H.; Caputo, T. D.; Purkiss, D. W.;
Li, G. Tetrahedron 2000, 56, 2397–2401.
The present catalytic system was found to be ineffective
to the oxidation of such alcohols as benzyl alcohol and
1-dodecanol; 13 and 11% yields of the corresponding
aldehydes were obtained, respectively, under the same
conditions.
2. Li, P.; Fong, W. M.; Chao, L. C. F.; Fung, S. H. C.;
Williams, I. D. J. Org. Chem. 2001, 66, 4087–4090 and
references cited therein.
3. (a) Ley, S. V.; Madin, A. In Comprehensive Organic Syn-
thesis; Trost, B. M.; Fleming, I., Eds.; Pergamon Press:
New York, 1991; Vol. 7, pp. 251–289; (b) Lee, T. V. In
Comprehensive Organic Synthesis; Trost, B. M.; Fleming,
I., Eds.; Pergamon Press: New York, 1991; Vol. 7, pp.
291–303; (c) Procter, G. In Comprehensive Organic Synthe-
sis; Trost, B. M.; Fleming, I., Eds.; Pergamon Press: New
York, 1991; Vol. 7, pp. 305–327; (d) Carreira, E. M.; Bois,
J. D. J. Am. Chem. Soc. 1995, 117, 8106–8125; (e) Han, Z.;
Shinokubo, H.; Oshima, K. Synlett 2001, 1421–1422.
4. (a) Sakaguchi, S.; Takase, T.; Iwahara, T.; Ishii, Y. Chem.
Commun. 1998, 2037–2038; (b) Masutani, K.; Uchida, T.;
Irie, R.; Katsuki, T. Tetrahedron Lett. 2000, 41, 5119–
5123.
The reaction mechanism is not yet clear, but the main
reaction course should be an ionic one, because the
oxidation was not much influenced by the addition of a
radical inhibitor such as 2,6-di-tert-butylphenol.
In summary, we found that the oxidation of some
propargylic alcohols to the corresponding carbonyl
compounds proceeded efficiently using VO(acac)2 as a
,
catalyst and in the presence of 3 A molecular sieves in
acetonitrile under an atmospheric pressure of molecular
oxygen. Further study to find the effective catalytic
oxidation system for a-acetylenic alkanols such as 1i–k
is in progress.
5. (a) Nishimura, T.; Onoue, T.; Ohe, K.; Uemura, S. Tetra-
hedron Lett. 1998, 39, 6011–6014; (b) Nishimura, T.;
Onoue, T.; Ohe, K.; Uemura, S. J. Org. Chem. 1999, 64,
6750–6755; (c) Nishimura, T.; Kakiuchi, N.; Inoue, M.;
Uemura, S. Chem. Commun. 2000, 1245–1246; (d)
Nishimura, T.; Maeda, Y.; Kakiuchi, N.; Uemura, S. J.
Chem. Soc., Perkin Trans. 1 2000, 4301–4305; (e) Kaki-
uchi, N.; Nishimura, T.; Inoue, M.; Uemura, S. Bull.
Chem. Soc. Jpn. 2001, 74, 165–172.
6. For recent advances in the aerobic oxidations catalyzed by
oxovanadium complexes, see: (a) Takai, T.; Yamada, T.;
Mukaiyama, T. Chem. Lett. 1990, 1657–1660; (b) Inoki,
S.; Takai, T.; Yamada, T.; Mukaiyama, T. Chem. Lett.
1991, 941–944; (c) Hirao, T. Chem. Rev. 1997, 97, 2707–
2724; (d) Kirihara, M.; Takizawa, S.; Momose, T. J.
Chem. Soc., Perkin Trans. 1 1998, 7–8; (e) Kirihara, M.;
Ochiai, Y.; Arai, N.; Takizawa, S.; Momose, T.; Nemoto,
H. Tetrahedron Lett. 1999, 40, 9055–9057; (f) Chu, C.-Y.;
Hwang, D.-R.; Wang, S.-K.; Uang, B.-J. Chem. Commun.
2001, 980–981; (g) Hirao, T.; Morimoto, C.; Takada, T.;
Sakurai, H. Tetrahedron 2001, 57, 5073–5079.
General procedure for the oxidation of propargylic alco-
hols using molecular oxygen: To a solution of VO(acac)2
(2.65 mg, 0.01 mmol) in acetonitrile (1.5 mL) in a 10
,
mL two-necked round-bottomed flask was added 3 A
molecular sieves (500 mg, powder). Next, a solution of
propargylic alcohol (1 mmol) in acetonitrile (0.5 mL)
was added and the resulting mixture was stirred. Oxy-
gen gas was then introduced into the flask from an O2
balloon under atmospheric pressure and then the mix-
ture was stirred vigorously for 3 h at 80°C under
oxygen. After the reaction, the mixture was cooled to
,
room temperature and 3 A molecular sieves was sepa-
rated by filtration through a glass filter. The amount of
the product was determined by GLC analysis using
bibenzyl as an internal standard. For isolation of the
product the solvent was evaporated and the residue was
purified by column chromatography (Merck silica gel
60; hexane–diethyl ether as an eluent) to give the
product.
7. For oxovanadium complex-catalyzed aerobic oxidation of
a-ketoalcohols, see: Kirihara, M.; Ochiai, Y.; Takizawa,
S.; Nemoto, H. Chem. Commun. 1999, 1387–1388.
8. Molecular sieves may work to remove water formed dur-
ing the oxidation. Such positive effect has been known.
See, for example: (a) Ref. 5b; See also: (b) Kato, K.;
Yamada, T.; Takai, T.; Inoki, S.; Isayama, S. Bull. Chem.
Soc. Jpn. 1990, 63, 179–186 and references cited therein.
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