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A. Watanabe et al. / Tetrahedron Letters 45 (2004) 6229–6233
6. Liang, S.; Bu, X. R. J. Org. Chem. 2002, 67, 2702–
2704.
7. Li(salen) has been used as a catalyst: Holmes, I. P.;
Kagan, H. B. Tetrahedron Lett. 2000, 41, 7457–
7460.
8. (a) BelokonÕ, Y.; Caveda-Cepas, S.; Green, B.; Ikonnikov,
N.; Khrustalev, V.; Larichev, V.; Moskalenko, M.; North,
M.; Orizu, C.; Tararov, V.; Tasinazzo, M.; Timofeeva, G.;
Yashkina, L. J. Am. Chem. Soc. 1999, 121, 3968–3973; (b)
BelokonÕ, Y.; Green, B.; Ikonnikov, N.; Larichev, V.;
Lokshin, B.; Moskalenko, M.; North, M.; Orizu, C.;
Peregudov, A.; Timofeeva, G. Eur. J. Org. Chem., 2000,
2655–2661; (c) BelokonÕ, Y.; Green, B.; Ikonnikov, N.;
North, M.; Parsons, T.; Tararov, V. Tetrahedron 2001, 57,
771–779.
Figure 2. Positive nonlinear effect observed in MPV cyanation of 3-
phenylpropanal with oxovanadium(V) complex 4 at room tempera-
ture.
9. BelokonÕ, Y.; North, M.; Parsons, T. Org. Lett. 2000, 2,
1617–1619.
10. Ooi, T.; Miura, T.; Takaya, K.; Ichikawa, H.; Maruoka,
K. Tetrahedron 2001, 57, 867–873.
11. (a) Saito, B.; Katsuki, T. Tetrahedron Lett. 2001, 42,
3873–3876; (b) Saito, B.; Katsuki, T. Tetrahedron Lett.
2001, 42, 8333–8336.
12. (a) Zr(salen) complex catalyzes Baeyer–Villiger reaction,
in which a ketone and hydrogen peroxide are coordinated
to the zirconium ion and reacted to give a chiral lactone:
Watanabe, A.; Uchida, T.; Ito, K.; Katsuki, T. Tetrahe-
dron Lett. 2002, 43, 4481–4485; (b) Watanabe, A.; Uchida,
T.; Irie, R.; Katsuki, T. Proc. Natl. Acad. Sci. USA 2004,
101, 5737–5742.
13. (a) Nakajima, K.; Kojima, K.; Kojima, M.; Fujita, J. Bull.
Chem. Soc. Jpn. 1990, 63, 2620–2630; (b) BelokonÕ, Y.;
Carta, P.; Gutnov, A.; Maleev, V.; Moskalenko, M.;
Yashkina, L.; Ikonnikov, N.; Voskoboev, N.; Khrustalev,
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3312.
complex 4 can be converted into the desired cis-b vana-
dium(V)(salen) complex.19 On the other hand, cyanation
of 3-phenylpropanal with acetone cyanohydrin in the
presence of the BelokonÕs vanadium(IV) complex was
sluggish (65% ee, 7%, 7h at rt), while the corresponding
vanadium(V) complex catalyzed the cyanantion
smoothly with modest enantioselectivity (45% ee, 99%,
12h at rt). These results agree with the above assump-
tion that a vanadium(V) complex is a suitable catalyst
and demonstrate that use of oxovanadium(V) complex
bearing the salen ligand including a binaphthyl unit is
essential for achieving high enantioselectivity in the pre-
sent MPV cyanation, though we could not completely
rule out the possibility that the reaction proceeds
through a l-oxo vanadium species as proposed for
asymmetric cyanation using trimethylsilyl cyanide.
14. Participation of a cis-b vanadium(salen) species has been
proposed by North and co-workers.9
15. Typical experimental procedure was as follows: catalyst 4
(5.0mg, 5lmol) was dissolved in a 0.01M CH2Cl2 solution
of 2,4,6-collidine (0.5mL) at room temperature. Acetone
cyanohydrin (36.5lL, 0.40mmol) was added to the
solution. The solution was cooled to 10°C. Octylaldehyde
(15.6lL, 0.10mmol) was added and the solution was
stirred at the temperature. After 48h, the reaction was
quenched by 1M HCl and extracted by CH2Cl2. The
extract was evaporated in vacuo. The resultant cyanohyd-
rin was acetylated by Ac2O (24lL, 0.25mmol), pyridine
(20lL, 0.25mmol) and a catalytic amount of 4-(N,N-
dimethylamino)pyridine in CH2Cl2 (1.0mL) at 0°C. After
2h, the reaction was quenched by water and extracted by
CH2Cl2. The extract was concentrated in vacuo and the
residue was chromatographed on silica gel (n-hex-
ane:AcOEt=19:1) to give the acetate (11.5mg, 65%).
Enantiomeric excess of the acetylated cyanohydrin was
determined by GLC analysis as described in the footnote
of Table 2.
In conclusion, we were able to demonstrate that oxova-
nadium(V)(salen) complex 4 serves as a catalyst for
asymmetric MPV cyanation. Further study on the
mechanism of the present reaction is under way.
References and notes
1. (a) Mori, A.; Inoue, S. In Comprehensive Asymmetric
Catalysis, Jacobsen, E. N., Pfaltz, A., Yamamoto, H.,
Eds.; Springer: Berlin, 1999; Vol. 2, pp. 983–994; (b)
North, M. Tetrahedron: Asymmetry 2003, 14, 147–176; (c)
Brunel, J.; Holmes, I. Angew. Chem. Int. Ed. 2004, 43,
2752–2778.
2. Shibasaki, M.; Kanai, M. Chem. Pharm. Bull. 2001, 49,
511–524.
3. (3) Hayashi, M.; Miyamoto, Y.; Inoue, T.; Oguni, N. J.
Org. Chem. 1993, 58, 1515–1522; (a) Zhou, X.-G.; Huang,
J.-S.; Ko, P.-H.; Cheng, K.-K.; Che, C.-M. J. Chem. Soc.,
Dalton. Trans. 1999, 3303–3309.
16. All the cyanohydrins and the corresponding acetates gave
satisfactory 1H NMR spectra that were in agreement with
the reported ones (Ref. 10), except for the cyanohydrin
and the acetate derived from 6-phenoxyhexanal. The
cyanohydrin and acetate are unknown compounds. The
benzoate derived from 2,2-dimethylpropanal also gave a
4. Katsuki, T. Synlett 2003, 281–297.
5. (a) Pan, W.; Feng, X.; Gong, L.; Hu, W.; Li, Z.; Mi, A.;
Jiang, Y. Synlett 1996, 337–338; (b) Belokon, Y.; Ikon-
nikov, N.; Moscalenko, M.; North, M.; Orlova, S.;
Tararov, V.; Yashkina, L. Tetrahedron: Asymmetry
1996, 7, 851–855.
1
satisfactory H NMR spectrum.
17. This assumption requires participation of a cis-b vana-
dium(V)(salen) species (see also Ref. 19), because coordi-
nation of two neutral ligands (acetone cyanohydrin