A mild and efficient oxidation of alcohols with N-tert-butylphenylsulfinimidoyl chloride in the coexistence of zinc oxide

Article abstract of DOI:10.1246/cl.2001.150

Various primary and secondary alcohols bearing β-aryl, alkenyl, or alkoxy moiety were efficiently oxidized to the corresponding labile aldehydes and ketones under mild conditions with N-tert-butylphenylsulfinimidoyl chloride (1) in the coexistence of zinc oxide.

Full text of DOI:10.1246/cl.2001.150

150
Chemistry Letters 2001
A Mild and Efficient Oxidation of Alcohols with
N-tert-Butylphenylsulfinimidoyl Chloride in the Coexistence of Zinc Oxide
Jun-ichi Matsuo, Hideo Kitagawa, Daisuke Iida, and Teruaki Mukaiyama*
Department of Applied Chemistry, Faculty of Science, Science University of Tokyo, Kagurazaka, Shinjuku-ku, Tokyo 162-8601
(Received November 22, 2000; CL-001061)
Various primary and secondary alcohols bearing β-aryl,
alkenyl, or alkoxy moiety were efficiently oxidized to the corre-
sponding labile aldehydes and ketones under mild conditions
with N-tert-butylphenylsulfinimidoyl chloride (1) in the coexis-
tence of zinc oxide.
equivalents of 1 in dichloromethane as a model reaction (Table
1). In the first place, molecular sieves 4A (MS4A) was tested
as a solid base because it was reported to work as a neutral
scavenger of hydrogen chloride.4 When MS4A (1 g/mmol) was
used, the yield of 3 was sufficiently improved (73%, entry 3).
When other types of zeolites such as MS3A and 5A were used,
on the other hand, the oxidation did not proceed smoothly. It
was then noted that MS4A was a preferred scavenger of hydro-
gen chloride among the three types of molecular sieves.
Cesium fluoride, which is known as a hydrogen bond-assisted
dehydrohalogenating agent, was ineffective in this oxidation.
Next, the oxidation was further tried in the coexistence of sev-
eral metal oxides since magnesium oxide5 and zinc oxide6 were
shown to be effective acid-scavengers in Friedel–Crafts type
reactions. Of several metal oxides screened,7 zinc oxide was
the most effective acid-scavenger in this reaction and it was
experimentally shown that zinc oxide itself did not work as an
oxidant (entry 12). Because the yield of 3 dropped significantly
when the amount of zinc oxide decreased from five to two
equivalents, experiments thereafter were carried out by using
five equivalents of zinc oxide.
A number of useful carbon–carbon bond forming reactions
using aldehydes and ketones have been developed to date, and
efficient and reliable methods for preparing various types of
aldehydes and ketones are important in organic synthesis.
Especially, oxidation of alcohols to the desired carbonyl com-
pounds is considered as a convenient tool for this purpose,
although most current oxidations are carried out under either
acidic or basic conditions which sometimes cause the decompo-
sition, polymerization, isomerization, or epimerization of the
prepared labile aldehydes and ketones.1 In order to prevent
such unfavorable side reactions, it may be worthwhile to con-
duct the oxidation under almost neutral conditions.
It was recently reported from our laboratory that primary
and secondary alcohols were efficiently oxidized with N-tert-
butylphenylsulfinimidoyl chloride (1) in the presence of DBU.2
Although a variety of primary and secondary alcohols were
efficiently oxidized by this new oxidation method, some types
of aldehydes such as α-aryl and α-ketoaldehydes were not
obtained in sufficient yields. For example, 3-phenylpropanol
was smoothly oxidized to 3-phenylpropanal by using 1 and
DBU (94%) while oxidation of 2-phenylethanol (2) gave
phenylacetaldehyde (3) in only 24% yield (Table 1, entry 1).
Swern et al. also reported that the oxidation of 2 using dimethyl
sulfoxide activated with oxalyl chloride afforded 3 in a low
yield (23%).3a These results suggested that the formed 3
decomposed under these basic oxidation conditions. In fact,
40%, 51%, and 55% of 3 decomposed in the presence of two
equivalents of DBU giving a complex mixture in CH2Cl2 at 0
°C after 5 min, 30 min, and 1 h, respectively. In order to pre-
vent the decomposition of the formed carbonyl product, the oxi-
dation using 1 must be conducted under as neutral conditions as
possible. Therefore, the original procedure was changed by
replacing DBU with another suitable scavenger of hydrogen
chloride, which was liberated during the formation of an inter-
mediate, alkoxysulfilimine, from 1 and an alcohol. Then, it was
thought that an insoluble solid base would be suitable because it
would not cause the decomposition of the formed carbonyl
compounds. In search for appropriate solid bases, zinc oxide
turned out to be the most effective, and in this communication
we would like to describe a mild and efficient oxidation of pri-
mary and secondary alcohols to the corresponding sensitive
aldehydes and ketones with 1 in the coexistence of zinc oxide.
Suitable solid bases were examined taking the oxidation of
2-phenylethanol (2) to phenylacetaldehyde (3) by using 1.5
Comparing with other oxidation methods (Table 2, entries
1–5), the combined use of 1 and zinc oxide was more effective
than Swern,3 PDC,8 and TPAP–NMO1a oxidations. On the
other hand, Dess–Martin periodinate (DMP)9 was also effective
in the oxidation of 2 to 3.10 These results indicate that the pres-
Copyright © 2001 The Chemical Society of Japan

Chemistry Letters 2001
151
ent oxidation could be carried out under milder conditions than
those of Swern, PDC, and TPAP–NMO oxidations.
Thus, various alcohols, especially, primary alcohols bear-
ing β-aryl, alkenyl, or alkoxy moiety were smoothly oxidized to
the corresponding carbonyl compounds with the combined use
of the oxidizing agent 1 and zinc oxide. The oxidation
described here is accomplished under mild conditions and suc-
cessfully applied to the preparation of sensitive carbonyl com-
pounds.
A typical experimental procedure is given for the oxidation
corresponding to Table 2, entry 1. To a stirred white suspen-
sion of 2 (70 mg, 0.57 mmol) and zinc oxide11 (233 mg, 2.86
mmol) in dry CH2Cl2 (1.5 mL) was added a solution of 1 (185
mg, 0.86 mmol) in CH2Cl2 (2 mL) at 0 °C. The reaction mix-
ture was stirred for 30 min at the same temperature and then
quenched with water (5 mL). The mixture was filtered through
Celite and the filter cake was washed with CH2Cl2 and water.
The layers were separated and the aqueous phase was extracted
with CH2Cl2. The yield of 3 (0.52 mmol, 91%) was determined
by GC analyses of the combined organic phase using an inter-
nal standard.
In addition to 2, primary and secondary alcohols bearing β-
aryl, alkoxy, or phenoxy moiety were oxidized smoothly by the
present oxidation method of using 1 and zinc oxide (entries
6–15). However, oxidation of secondary alcohols was slower
than that of primary ones, and yields of ketones were moderate to
good. Compared to the original procedure using DBU as a base,
the present oxidation was carried out under slightly acidic condi-
tions and a cleavage of trimethylsiloxy group was observed while
an ester group survived during this oxidation. Also, simple pri-
mary and secondary alcohols were oxidized to the corresponding
aldehydes and ketones by the present oxidation, although higher
yields of the corresponding carbonyl compounds were achieved
by the original procedure of using DBU as a base (entries 17–19).
References and Notes
1
a) S. V. Ley, J. Norman, W. P. Griffith, and S. P. Marsden,
Synthesis, 1994, 639, and references are cited therein. b)
A. B. Smith, III and P. A. Levenberg, Synthesis, 1981, 567.
c) T. T. Tidwell, Synthesis, 1990, 857.
2
3
T. Mukaiyama, J. Matsuo, and M. Yanagisawa, Chem.
Lett., 2000, 1072.
a) A. J. Mancuso and D. Swern, Synthesis, 1981, 165. b)
D. M. Walba, W. N. Thurmes, and R. C. Haltiwanger, J.
Org. Chem., 53, 1046 (1988).
4
a) Y. Miyake and Y. Yoshiura, Japanese Patent, 73 26,683
(1971); Chem. Abstr., 79, 18021y (1973). b) L. M.
Weinstock, S. Karady, F. E. Roberts, A. M. Hoinowski, G.
S. Brenner, T. B. K. Lee, W. C. Lumma, and M.
Sletzinger, Terahedron Lett., 1975, 3979.
5
6
T. Mukaiyama, M. Nakano, W. Kikuchi, and J. Matsuo,
Chem. Lett., 2000, 1010.
a) T. Mukaiyama, H. Kitagawa, and J. Matsuo,
Tetrahedron Lett., 41, 9383 (2000). For other examples,
see ref 6b and 6c. b) J. L. Charlton, Can. J. Chem., 64, 720
(1986). c) J. L. Charlton and M. M. Alauddin, J. Org.
Chem., 51, 3490 (1986).
7
Only in the case of NiO, a considerable amount (55%) of
(2-chloroethyl)benzene was detected (Table 1, entry 10).
E. J. Corey and G. Schmidt, Tetrahedron Lett., 1979, 399.
a) D. B. Dess and J. C. Martin, J. Org. Chem., 48, 4155
(1983). b) S. D. Meyer and S. L. Schreiber, J. Org. Chem.,
59, 7549 (1994).
8
9
10 The oxidation of 2 to 3 was carried out under following
conditions. Entry 3: PDC (1.5 equiv), CH2Cl2, rt, 12 h.
Entry 4: TPAP (20 mol%), NMO (1.5 equiv), MS4A (500
mg/mmol), CH2Cl2, 0 °C, 1 h. Entry 5: DMP (1.5 equiv),
wet CH2Cl2, rt, 30 min.
11 Commercial zinc oxide (purchased from Kanto Chemical
Co., Inc.) was used without purification, because the oxida-
tion of 2 by using dried zinc oxide (in vacuo, 150 °C, 5 h)
and 1 gave 3 in a comparable yield (89%).