Chemistry Letters Vol.32, No.2 (2003)
183
a
Table 2. Catalytic oxidation of alcohols with Br2
were easily isolated in good to high yields.
Typical experimental procedure is as follows (Table 2, entry
1): To a stirred suspension of potassium carbonate (829mg,
6.00 mmol), molecular sieves 4A (300 mg), 5-hydroxypentyl
benzoate (8) (62.5 mg, 0.30 mmol), and sulfenamide 5 (3.5 mg,
15 mmol) in dichloromethane (4.0 mL) was added dropwise a
solution of Br2 (52.7 mg, 0.33 mmol) in dichloromethane
(1.0 mL) at room temperature for 10 min. After the reaction
mixture was stirred for 50 min, the reaction was quenched by
adding 10% aqueous Na2S2O3 solution (1.0 mL). The mixture
was filtered through Celite pad, and the filtrate was extracted with
dichloromethane. The combined organic extracts were dried over
anhydrous sodium sulfate, filtered, and concentrated in vacuo.
The crude product was purified by preparative thin-layer
chromatography (hexanes - ethyl acetate = 3:1) to give 4-
formylbutyl benzoate (9) (55.6 mg, 90%) as a colorless oil.
The present work was partially supported by Grant-in-Aids
for Scientific Research from the Ministry of Education, Culture,
Sports, Science and Technology, Japan.
References and Notes
1
2
3
T. Mukaiyama, J. Matsuo, D. Iida, and H. Kitagawa, Chem.
Lett., 2001, 846.
M. A. Neirabeyeh, J.-C. Ziegler, and B. Gross, Synthesis,
1976, 811.
a) K. Saigo, A. Morikawa, and T. Mukaiyama, Chem.Lett. ,
1975, 145. b) K. Saigo, A. Morikawa, and T. Mukaiyama,
Bull.Chem.Soc.Jpn. , 49, 1656 (1976). c) Y. Ueno and M.
Okawara, Tetrahedron Lett., 1976, 4597.
4
5
L. K. Blair, J. Baldwin, and W. C. Smith, Jr., J.Org.Chem. ,
42, 1816 (1977).
a) M. P. Doyle and R. L. Dow, Synth.Commun. , 10, 881
(1980). b) M. P. Doyle and V. Bagheri, J.Org.Chem. , 46,
4806 (1981).
6
7
D. R. Williams, F. D. Klingler, E. E. Allen, and F. W.
Lichtenthaler, Tetrahedron Lett., 29, 5087 (1988).
For oxidation of alcohols to carbonyl compounds with Cl2,
see: a) E. J. Corey and C. U. Kim, J.Am.Chem.Soc. , 94, 7586
(1972). b) E. J. Corey and C. U. Kim, Tetrahedron Lett., 14,
919 (1973). c) J. Wicha and A. Zarecki, Tetrahedron Lett., 15,
3059(1974).
carried out in the absence of catalyst 5, 4-phenylcyclohexanone
was obtained in only 55% yield along with various by-products.
This result clearly indicated that sulfenamide 5 efficiently
catalyzed the oxidation of secondary alcohols with Br2 to afford
ketones in high yields. When alcohols having double bonds
within the same molecule were oxidized under the present
conditions, however, bromination of double bonds proceeded in
the first place and oxidation of a hydroxy group took place in turn.
On the other hand, p-methoxybenzyl, tert-butyldimethylsilyloxy,
and benzylcarbamoyl groups were not damaged in the present
oxidation.
8
9
Amino groups are protected with o-nitrobenzenesulfenyl
group. See: T. W. Greene and P. G. Wuts, ‘‘Protective Groups
in Organic Synthesis,’’ 3rd ed., John Wiley & Sons, New York
(1999).
N-tert-Butyl-2-nitrobenzenesulfenamide (5) was prepared by
the reaction of 2-nitrobenzenesulfenyl chloride and tert-
butylamine. See also: R. Schubart, U. Eholzer, and T.
Kempermann, Eur. Pat. Appl. 301376 (1989).
10 Catalytic oxidation of menthol by using 1 (10 mol%), NCS
(1.1 equiv.), K2CO3 (10 equiv.), and MS4A (1 g/mmol) in
CH2Cl2 at room temperature for 2 h gave menthone in 18%
yield.
Thus, it was noted that both primary and secondary alcohols
were oxidized with Br2 by using a catalytic amount of
sulfenamide 5, and the corresponding aldehydes and ketones