X. Jia et al. / Tetrahedron Letters 48 (2007) 971–974
973
1969, 34, 1977–1979; (c) Corriu, R. J. P.; Lanneau, G. F.;
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R.; Stoltz, B. M. J. Am. Chem. Soc. 2002, 124, 13179–
13184.
RCOCl
RCHO
2
1
1
0
%
K
2
C
O
3
3
8. (a) Davies, A. G. Organotin Chemistry; VCH: New York,
1997; (b) Lusztyk, J.; Lusztyk, E.; Maillard, B.; Lunazzi,
L.; Ingold, K. U. J. Am. Chem. Soc. 1983, 105, 4475–4477;
(c) Four, P.; Guibe, F. J. Org. Chem. 1981, 46, 4439–4445.
9. For reviews and representative examples, see: (a) Girard,
P.; Namy, J. L.; Kagan, H. B. J. Am. Chem. Soc. 1980,
102, 2693–2698; (b) Kagan, H. B. Tetrahedron 2003, 59,
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31, 603–609; (e) Molander, G. A.; Harris, C. R. Tetra-
hedron 1998, 54, 3321–3354; (f) Molander, G. A.; Harris,
C. R. Chem. Rev. 1996, 96, 307–338; (g) Molander, G. A.
Chem. Rev. 1992, 92, 29–68.
O
O
OH
R PBu3
Sm
H+
R
PBu3
R
PBu3
O
B
C
A
+ 2e
R
Scheme 3.
cal reduction of acyl chloride in the presence of ester
functionality (entry 10).
10. (a) Girard, P.; Couffignal, R.; Kagan, H. B. Tetrahedron
Lett. 1981, 22, 3959–3960; (b) Souppe, J.; Namy, J. L.;
Kagan, H. B. Tetrahedron Lett. 1984, 25, 2869–2872; (c)
Collin, J.; Namy, J. L.; Dallemer, F.; Kagan, H. B. J. Org.
Chem. 1991, 56, 3118–3122.
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1994, 35, 1723–1726.
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2431–2444.
13. (a) Li, J.; Xu, H.; Zhang, Y. M. Tetrahedron Lett. 2005,
46, 1931–1934; (b) Jia, X.; Wang, H.; Huang, Q.; Kong,
L.; Zhang, W. J. Chem. Res. 2006, 135–138.
14. For reduction of aroyl chlorides with samarium metal in
DMF, see also: Liu, Y. J.; Wang, X. X.; Zhang, Y. M.
Synth. Commun. 2004, 34, 4009–4022.
15. Vedejs, E.; Diver, S. T. J. Am. Chem. Soc. 1993, 115,
3358–3359.
16. Vedejs, E.; Bennett, N. S.; Conn, L. M.; Diver, S. T.;
Gingras, M.; Lin, S.; Oliver, P. A.; Peterson, M. J. J. Org.
Chem. 1993, 58, 7286–7288.
The mechanism of the above conversion could be
depicted as follows (Scheme 3): acyl chloride may react
with Bu3P to form an acyltributylphosphonium ion A,15
which could accept two electrons from samarium(0) to
form the corresponding intermediate a-oxyylide B, an
equivalent of acyl anion. Further protonation of B
would afford the a-hydroxyalkalphosphonium ion C,
which could be converted to the corresponding aldehyde
under weak basic conditions. As shown in this catalytic
cycle, the formation of phosphonium salt A was consid-
ered to be the key step.
In summary, we have developed a facile and novel meth-
od for the synthesis of aldehydes from acyl chlo-
rides.19,20 This new protocol allows for the efficient
conversion of both aromatic and aliphatic acyl chlorides
to their corresponding aldehydes without the occurrence
of over-reduction to alcohols. The mild conditions, high
yields and broad scope of this reaction make it an excel-
lent alternative to the existing methods.
17. Ph3P was also investigated in our attempts, but the
formation of corresponding salt was quite slow (several
days).
18. (a) Inoue, K.; Yasuda, M.; Shibata, I.; Baba, A. Tetra-
hedron Lett. 2000, 41, 113–116; (b) Geng, L.; Lu, X. J.
Organomet. Chem. 1989, 379, 41–43; (c) Entwistle, I. D.;
Boehm, P.; Johnstone, R. A. W.; Telfort, R. P. . J. Chem.
Soc., Perkin Trans. 1 1980, 27–30; (d) Leblanc, J. C.;
Moise, C.; Tirouflet, J. J. Organomet. Chem. 1985, 292,
225–228.
Acknowledgement
We thank the National Natural Science Foundation of
China (Nos. 20472048 and 20572068) for financial
support.
19. A typical procedure for the preparation of aromatic
aldehydes 2 is as follows: To a stirred solution of 1 mmol
acyl chloride 1 dissolved in 10 mL CH3CN was added
1.2 mmol Bu3P at À20 ꢁC under a nitrogen atmosphere.
About 15 min later, 0.33 mL HCl (6 M) and 2/3 mmol
samarium powder (0.1 g) were added successively. After
being stirred for 1 h, the reaction mixture was allowed to
warm to room temperature gradually. Upon completion
of the reaction, the resulting mixture was poured into
aqueous 10% HCl (30 mL) and extracted with CH2Cl2
(50 mL · 2). The organic phase was washed with aqueous
10% K2CO3 (80 mL), dried over anhydrous Na2SO4,
filtered, concentrated and the residue was purified by
column chromatography on silica gel eluting with hexane/
ethyl acetate (10:1) to afford the products. All of the
products are known and were characterized by com-
parison of their spectral data with those of authentic
samples.
References and notes
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