A new method for oxidation of various alcohols to the corresponding carbonyl compounds by using n-t-butylbenzenesulfinimidoyl chloride

Article abstract of DOI:10.1246/bcsj.75.223

Various primary and secondary alcohols were smoothly oxidized to the corresponding aldehydes and ketones by using a new oxidizing agent, N-t-butylbenzenesulfinimidoyl chloride (4a), in the coexistence of DBU or zinc oxide. The present oxidation proceeded under mild conditions via five-membered intramolecular proton-transfer of an alkyl arenesulfinimidate intermediate.

Full text of DOI:10.1246/bcsj.75.223

c. Jpn.
© 2002 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 75, 223–234 (2002)
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Headline Articles
A New Method for Oxidation of Various Alcohols to the Corresponding
02
3
4
SJA8
09-2673
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Carbonyl Compounds by Using N-t-Butylbenzenesulfinimidoyl Chloride
A New Method for Oxidation of Alcohols
J. Matsuo et al.
Jun-ichi Matsuo, Daisuke Iida, Kazuya Tatani, and Teruaki Mukaiyama*
Department of Applied Chemistry, Faculty of Science, Science University of Tokyo, Kagurazaka, Shinjuku-ku,
Tokyo 162-8601
01
(Received July 31, 2001)
01
Various primary and secondary alcohols were smoothly oxidized to the corresponding aldehydes and ketones by
using a new oxidizing agent, N-t-butylbenzenesulfinimidoyl chloride (4a), in the coexistence of DBU or zinc oxide. The
present oxidation proceeded under mild conditions via five-membered intramolecular proton-transfer of an alkyl arene-
sulfinimidate intermediate.
3.6
Oxidation of primary and secondary alcohols to the corre-
sponding carbonyl compounds is one of the most fundamental
and important transformations in organic synthesis because
thus formed aldehydes and ketones are valuable synthetic in-
termediates especially in carbon–carbon bond forming reac-
tions for constructing a targeted carbon skeleton. Many oxida-
tion methods have been reported to date1 and simple alcohols
that form stable carbonyl products are oxidized by a number of
oxidants. In recent years, the structures of target molecules in
organic synthesis are becoming more complicated, so better
functional compatibility and higher selectivity are required for
the efficient oxidation. In this regard, conventional oxidants do
not always satisfy such requirements; therefore, exploration of
new oxidizing agents is worth challenging.
Oxidation of alcohols by using heavy metal oxidants such as
chromium or manganese is a classical method. As a matter of
fact, chromium(Ⅵ)-based oxidizing reagents known as Jones
reagent,2 Collins reagent,3 pyridinium chlorochromate (PCC),4
pyridinium dichromate (PDC),5 etc. have been used quite com-
monly in organic synthesis. However, toxic chromium resi-
dues formed after the oxidation were the causes of some prob-
lems during work-up and also at their disposal. To solve those
problems, oxidation by using a catalytic amount of transition
metals has been developed in the past two decades, and tetra-
propylammonium perruthenate (TPAP)-catalyzed oxidation of
alcohols has spread because of its wide applicability as well as
its easy work-up procedures.6
ing without over-oxidation, and easy work-up. However, DMP
and its synthetic precursor, 1-hydroxy-1,2-benziodoxol-3(1H)-
one (IBX), are reported to be explosive on impact or heating to
> 200 °C.7d Therefore, these reagents must be kept in a refrig-
erator and should not be used in large scales.
In 1963, Pfitzner and Moffatt discovered a new dimethyl
sulfoxide-based oxidation method in which primary and sec-
ondary alcohols were efficiently oxidized to the corresponding
aldehydes and ketones, respectively, by using dimethyl sulfox-
ide, dicyclohexylcarbodiimide, and certain kinds of acids.8a
Many similar oxidation reactions using activated dimethyl sulf-
oxides have been developed since then:8e for example, activa-
tion of dimethyl sulfoxide by using acetic anhydride,8b SO2–
pyridine,8c and trifluoroacetic anhydride.8d Among them,
Swern's method is known to be one of the most useful oxida-
tion methods.9 In Swern oxidation, dimethyl sulfoxide is acti-
vated with oxalyl chloride to form chlorodimethylsulfonium
chloride (1) at −60 °C, and then an alcohol reacts with 1 to
give alkoxysulfonium chloride (2). The formed 2 is deproto-
nated with triethylamine to form alkoxysulfonium ylide (3), in
which an intramolecular proton transfer affords a carbonyl
product along with dimethyl sulfide (Scheme 1, reaction 1). A
wide variety of alcohols have effectively been oxidized and
carbonyl products are easily purified after the Swern oxidation.
However, the oxidation reaction must be carried out at strictly
controlled low reaction temperatures since 1 is not stable
above −20 °C.9a Also, an unpleasant odor of dimethyl sulfide
formed by the oxidation is another disadvantage of Swern oxi-
dation.
Of various non-metal oxidants, Dess–Martin periodinate
(1,1,1-triacetoxy-1,1-dihydro-1,2-benziodoxol-3(1H)-one,
DMP) is known to be one of the mildest reagents for the oxida-
tion of alcohols.7 It is more often employed in the oxidation of
complex or labile molecules because of the following advan-
tages: mildness, wider functional group tolerance, high yield-
During our study on the asymmetric total synthesis of
TaxolTM 10
, it was noticed that there were many alcohol-oxida-
tion steps in constructing the basic skeleton of Taxol. There-
fore, our interest was focused on the exploration of a conve-

224 Bull. Chem. Soc. Jpn., 75, No. 2 (2002)
HEADLINE ARTICLES
rides 4a–c in high purities, which could be used without fur-
ther purification. They could be further purified by distillation
under reduced pressures, if necessary.
These oxidizing agents 4a–c were synthesized in large
quantities and thus prepared 4a–c were handled without using
inert-atmosphere techniques when a slightly larger amount of
the reagents was employed. Also, they could be stored for a
long time in a sealed bottle at room temperature. Compared
with 1, the thermal stability of 4 increased a great deal just by
changing sulfur-carbon bond to sulfur-nitrogen bond. On the
other hand, the preparation of sulfinimidoyl chlorides took
place sluggishly according to the similar procedures when
electron-withdrawing groups such as NO2 or Cl were intro-
duced on the aromatic rings of S-aryl thioacetates 7. Also, S-
alkyl substituted sulfinimidoyl chlorides such as N-t-butyl-
methanesulfinimidoyl chlorides or N-t-butyl-1,1-dimethyl-
ethanesulfinimidoyl chlorides were not successfully prepared
by the reaction of 8 with S-methyl thiobutyrate or S-t-butyl
thioacetate.
Oxidation of Benzyl Alcohol (9a) and Cyclopentanol
(10a) by Using N-t-Butylbenzenesulfinimidoyl Chloride
(4a). In the first place, oxidation of benzyl alcohol (9a) to
benzaldehyde (9b) was examined by using 4a as an oxidizing
agent (Table 1). When 4a and 9a were mixed in dichlo-
romethane at −78 °C in the absence of bases, benzyl chloride
was formed as a main product while the expected oxidation re-
action hardly took place (Table 1, entry 1). It was assumed
that this chloride substitution took place via in situ formed
benzyloxy(N-t-butylamino)(phenyl)sulfonium chloride (11) as
shown in Scheme 3. Similar substitution of chloride ion for
hydroxy groups was reported in the reaction of sulfonimidoyl
chlorides and alcohol.15 When an equimolar amount of 1,8-di-
azabicyclo[5.4.0]undec-7-ene (DBU) was used for trapping
hydrogen chloride, the desired oxidation took place in 65%
yield along with 26% of benzyl chloride (Table 1, entry 2). In
the case of using two molar amounts of DBU, the above-men-
tioned substitution reaction by chloride ion was completely
suppressed and the desired oxidation smoothly took place at
−78 °C to afford 9b in almost quantitative yield (Table 1, entry
3).
The oxidation of 9a proceeded also in high yields by using
amine bases such as ethyldiisopropylamine or 1,4-diazabicy-
clo[2.2.2]octane (DABCO) (Table 1, entries 4 and 5), whereas
other organic bases such as triethylamine and any types of pyr-
idines were not effective (Table 1, entries 6–9). These results
suggest that the present oxidation proceeded more efficiently
when sterically hindered and sufficiently basic amines were
used. As described by Gilchrist et al., basicities of N-non-sub-
stituted sulfinimidates are compatible to those of primary
amines.12 Therefore, bases stronger than primary amines are
essential for the effective generation of the important interme-
diate, alkyl sulfinimidate 5.
Scheme 1.
nient and useful new oxidation method. It was then thought
that alkyl sulfinimidate 5 would work as the intermediate for
oxidation of alcohols by considering its intramolecular proton
transfer as in 3 (Scheme 1, reaction 2). Further, it was expect-
ed that 5 would be readily formed from sulfinimidoyl chloride
4 and alcohols. The results of new oxidation of alcohols under
basic or almost neutral conditions by using 4 as a new oxidiz-
ing agent were preliminary reported.11 Here, we would like to
report on a novel and efficient oxidation of primary and sec-
ondary alcohols to the corresponding aldehydes and ketones
by using N-t-butylbenzenesulfinimidoyl chlorides (4a) and
DBU or zinc oxide in further detail.
Results & Discussion
Synthesis of N-t-Butylarenesulfinimidoyl Chlorides 4a–c.
Since electron-donating alkyl groups were considered to in-
crease the nitrogen’s basicity12 of alkyl sulfinimidate 5, t-butyl
group was chosen for N-substituent of sulfinimidoyl chloride,
expecting that the proposed proton-transfer in 5 would proceed
more favorably. The preparation of sulfinimidoyl chlorides
was already reported by Markovskii et al.,13 and N-t-butylar-
enesulfinimidoyl chlorides 4a–c were prepared easily from the
corresponding S-aryl thioacetates 7a–c and N,N-dichloro-t-bu-
tylamine (8)14 (Scheme 2). That is, the two reagents were re-
fluxed in benzene and then the solvent and the formed acetyl
chloride were removed from the reaction mixture. The resi-
dues contained the desired N-t-butylarenesulfinimidoyl chlo-
In the above experiments, the oxidizing agent 4a was added
to the mixture of alcohol 9a and an amine base since the un-
desired by-product, benzyl chloride, was formed if 4a and 9a
were mixed in advance. Further, it was found that the oxidiz-
ing agent 4a reacted also with amine bases because the mixture
of 4a and DBU prepared in advance did not afford the oxida-
tion product. Therefore, it was thought that a part of 4a de-
Scheme 2.

J. Matsuo et al.
Bull. Chem. Soc. Jpn., 75, No. 2 (2002) 225
Table 1. Oxidation of Benzyl Alcohol (9a) and Cyclopentanol (10a) by Using 4a
Entry
1
2
3
4
5
6
7
8
Alcohol
9a
Base (mol amt)a)
none
DBU (1.0)
Solvent
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
THF
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
toluene
THF
Temp/°C
−78
−78
−78
−78
−78
−78
−78
−78
−78
−78
−78
−78
−45
−20
0
Yieldb)/%
2 (28)
65 (26)
98 (0)
91 (1)
85 (7)
9a
9a
9a
9a
9a
9a
9a
9a
9a
9a
9a
9a
9a
9a
9a
9a
DBU (2.0)
iPr2NEt(2.0)
DABCO (2.0)
Et3N (2.0)
57 (3)
24 (1)
Et3N (5.0)
2,6-ditBu-Py (2.0)
pyridine (2.0)
NaH (1.0)
10 (17)
6 (25)
85 (trace)
67 (14)
71 (14)
94 (1)
87 (5)
81 (5)
80 (5)
76 (trace)
69 (trace)
88 (5)
72 (0)
90 (10)
>99 (0)
9
10
11
12
13
14
15
16
17
18
19
20
21
22
MS4A (1 g/mmol)
MS4A (3 g/mmol)
DBU (2.0)
DBU (2.0)
DBU (2.0)
DBU (2.0)
DBU (2.0)
DBU (2.0)
DBU (2.0)
rt
0
0
0
0
rt
rt
9a
9a
9a
10a
10a
CH3CN
DMF
CH2Cl2
CH2Cl2
DBU (2.0)
DBU (1.0)
DBU (2.0)
a) DBU: 1,8-diazabicyclo[5.4.0]undec-7-ene. DABCO: 1,4-diazabicyclo[2.2.2]octane. 2,6-ditBu-Py: 2,6-
Di-t-butylpyridine. MS4A: Powdered molecular sieves. b) Yields were determined by GC-analysis using
an internal standard. Numbers in parentheses were yields of benzyl chloride (Entries 1–20) or cyclopentyl
chloride (Entries 21–22).
ble 1, entries 3 and 13–16). The present oxidation reaction
could still be carried out at the temperatures higher than those
required in Swern oxidation due to the higher stability of 4a.
After screening several other solvents such as toluene, THF,
acetonitrile, and DMF, it was found that any of the solvents
could be used and dichloromethane was the most preferable
Scheme 3.
(Table 1, entries 17–20).
Since benzylic position was easily substituted by chloride
ion, the effect of the amount of DBU was further examined in
the oxidation of cyclopentanol (10a) to cyclopentanone (10b).
It was then revealed that the use of an equimolar amount of
DBU gave 10b in high yield (90%), but cyclopentyl chloride
was still accompanied in 10% yield (Table 1, entry 21). As in
the case of oxidation of benzyl alcohol (9a), the use of two
molar amounts of DBU completely prevented the formation of
cyclopentyl chloride. In general, the oxidation experiments
using 4a, therefore, were carried out in the presence two molar
amounts of DBU.
composed by the interaction with amine bases before the key
intermediate 5 was formed, and better oxidation results were
obtained when sterically hindered amines which reacted slow-
ly with 4a were used.
The oxidation using 4a and sodium alkoxide, prepared from
equimolar amount of sodium hydride and 9a, gave 9b in 85%
and the undesirable substitution reaction by chloride ion was
suppressed (Table 1, entry 10). Interestingly, the oxidation
proceeded in a moderate yield when molecular sieves 4A was
used as a solid base (Table 1, entries 11 and 12). Other exam-
ples about the oxidation of alcohols by using 4a and solid
bases will be described later.
Oxidation of Benzylic and Allylic Alcohols. Oxidation
of various primary and secondary alcohols was tried by using
1.5 molar amounts of 4a and 2.0 molar amounts of DBU in
dichloromethane (Tables 2 and 3). Most of benzylic and allyl-
Our study of reaction temperatures found that the yields of
9b decreased gradually at the temperatures above −45 °C (Ta-

226 Bull. Chem. Soc. Jpn., 75, No. 2 (2002)
HEADLINE ARTICLES
Table 2. Oxidation of Benzylic and Allylic Alcohols 9a and 12–27a to the Corresponding Aldehydes and Ketones 9b and 12–27b by
using 4a and DBU
Entry
Alcohol
Conditions
Yield/%a)
Entry
10
Alcohol
Conditions
Yield/%a)
92b)
1
2
9a −78 °C, 30 min 98
12a −78 °C, 30 min 90
20a −78–0 °C, 1 h
3
4
13a −78 °C, 30 min 93
14a −78 °C, 30 min 99b)
11
12
21a −78 °C–rt, 2 h
81b)
5
6
15a −78 °C, 30 min 99b)
(99)b),c)
22a −78 °C, 30 min 94
16a −78 °C, 30 min 92b)
17a −78 °C, 30 min 86b)
18a −78 °C, 30 min 91b)
13
14
23a −78 °C, 30 min 82
24a −78 °C, 30 min 87e)
7d)
15c)
16c)
17c)
25a −78 °C, 30 min 90
26a −78 °C, 30 min 80
27a −78 °C, 30 min 92
8c)
9
19a
0 °C, 30 min 87
a) Yields were determined by GC-analysis unless otherwise mentioned. b) Isolated yield. c) Reactions were quenched by addition of
saturated aqueous sodium hydrogencarbonate. d) 4a (3.7 mol amt) and DBU (4.9 mol amt) were used. e) Isolated yield of the corre-
sponding 2,4-dinitrophenylhydrazone.
ic alcohols were oxidized smoothly at −78 °C (Table 2); how-
ever, hydroxy groups at sterically hindered positions (Table 2,
entries 9 and 10) or those adjacent to an electron-withdrawing
trifluoromethyl group (Table 2, entry 11) were oxidized at ele-
vated temperatures (up to room temperature). α-Ketol (16a)
and 1,2-diol (17a) were oxidized efficiently to the correspond-
ing dicarbonyl compounds without accompanying glycol car-
bon–carbon bond cleavage (Table 2, entries 6 and 7). It was
noted that the secondary hydroxy group of 18a was successful-
ly oxidized in the presence of trimethylsiloxy group by the
present oxidation method (Table 2, entry 8). Further, the at-
tempted direct oxidation of trimethylsilyl ether of cyclohex-
anol did not afford cylohexanone, and almost all the starting
material was recovered. Different from Swern oxidation
which affords the corresponding carbonyl compounds directly
on treating trimethysilyl ethers of primary and secondary alco-
hols,16 selective oxidation successfully proceeded by the
present procedure. An acetylenic alcohol (24a) was also oxi-
dized at −78 °C in a high yield (Table 2, entry 14), and those
having heterocyclic rings were again readily oxidized regard-
less of the kind of hetero atoms included in the heterocyclic
rings (Table 2, entries 15–17). Pyridine, furan, and thiophene
rings were not damaged during the oxidation with 4a. Thus,
an effective oxidation method for a wide variety of alcohols
having various highly functional groups was established.
Oxidation of Primary and Secondary Alcohols. Prima-
ry and secondary alcohols were also smoothly oxidized by the
combined use of 4a and DBU at the temperatures between 0
°C and room temperature (Table 3). The temperatures for the
oxidation of primary alcohols were obviously lower than that
of secondary ones, which indicated the influence of steric fac-
tors on the present oxidation. In fact, oxidation of a sterically
hindered alcohol, (+)-menthol (39a), was slow and gave men-
thone in only 49% yield (entry 13), while secondary alcohols
giving methyl ketones such as 2-pentanol and 4-phenyl-2-bu-
tanol were oxidized in about 80% yields (Table 3, entries 15–
17). Interestingly, the oxidation of isoborneol (44a) was some-
what different from that of borneol (45a) (Table 3, entries 18
and 19), and 44a was oxidized more effectively than 45a.
In addition to 4a, several N-t-butylarenesulfinimidoyl chlo-
rides were prepared and oxidations were examined by taking
4-phenyl-2-butanol (42a) as a model substrate. Substituents at
para position of the aryl group such as methyl (4b) or methoxy
(4c) group did not exhibit any advantageous effects (Table 3,
entry 16).
According to the assumed mechanism of the present oxida-
tion (Scheme 1, reaction 2), the oxidizing reagent 4a was con-
verted to N-t-butylbenzenesulfenamide (6a).17 In fact, 95% of
6a was detected by 1H NMR after the oxidation of benzyl alco-
hol (9) by using 4a and DBU (Scheme 4).

J. Matsuo et al.
Bull. Chem. Soc. Jpn., 75, No. 2 (2002) 227
Table 3. Oxidation of Various Alcohols 10a and 28–45a to the Corresponding Carbonyl Compounds 10b and 28–45b by using 4a
and DBU
Entry
Alcohol
Conditions
Yield/%a)
Entry
13
Alcohol
Conditions
Yield/%a)
49
1
2
28a 0 °C, 30 min
29a 0 °C, 30 min
94b)
97(98)b),e)
39a rt, 30 min
3
4
5
30a 0 °C, 30 min
31a 0 °C, 1 h
87c)
92c)
14
15
16
40a rt, 30 min
41a rt, 30 min
42a rt, 30 min
98
82
32a 0 °C–rt, 1 h
75
(77)d)
76c)
6
7
33a 0 °C, 30 min
34a 0 °C–rt, 1 h
99
82
78
74f)
83g)
8
9
35a rt, 30 min
10a rt, 30 min
36a rt, 30 min
> 99
17
18
19
43a rt, 1 h
78
97
74
10
91
87
44a rt, 30 min
45a rt, 30 min
11
12
37a rt, 30 min
38a rt, 30 min
82
a) Determined by GC-analysis unless otherwise mentioned. b) Isolated yields of the corresponding 2,4-dinitrophenylhydrazones.
c) Isolated yield. d) Reactions were quenched by addition of saturated aqueous sodium hydrogencarbonate. e) Reaction condi-
tions: rt, 30 min. f) 4b was used instead of 4a. g) 4c was used instead of 4a.
dures: for example, 15b was isolated in 99% yield by quench-
ing with both 1% aqueous HCl solution and saturated aqueous
NaHCO3 (Table 2, entry 5).
To purify the formed carbonyl compounds was often trou-
blesome because co-products of the present oxidation, such as
6a, diphenyl disulfide, and N-t-butylbenzenesulfinamide (46),
had to be removed by silica gel- or alumina-column chroma-
tography after the oxidation using 4b. However, aldehydes
could be isolated without purification with column chromatog-
raphy by transforming them into the corresponding hydrogen-
sulfite addition compounds19: that is, i) converting them first to
water-soluble hydrogensulfite addition compounds with aque-
ous sodium hydrogensulfite solution; ii) washing out the oxi-
dation co-products by extraction with organic solvents; iii) de-
sired aldehydes were regenerated from the aqueous solution by
the decomposition of hydrogensulfite addition compounds.
The above-mentioned procedure afforded the desired aldehyde
30b in 73% yield without purification by column chromatogra-
phy (Scheme 5).
Scheme 4.
The detected 6a was formed by the reduction of 4a during
the oxidation process. The sulfenamide 6a whose basicity was
much weaker than that of t-butylamine18 could not be removed
from the reaction mixture by washing with 1% aqueous HCl
solution. On the other hand, diphenyl disulfide which was
formed by the direct hydrolysis of 4a and by the decomposi-
tion of 6a18 was isolated by the purification with silica gel col-
umn chromatography. It was also shown that 6a was partially
decomposed during the purification with silica gel column
chromatography.
Oxidation of Alcohols Giving Labile Carbonyl Com-
pounds. The oxidization of relatively simple alcohols giving
stable carbonyl compounds smoothly proceeded by using 4a
and DBU whereas the oxidation of several alcohols such as β-
aryl, and β-carbonyl alcohols proceeded to give the corre-
sponding carbonyl compounds in low yields. For example, the
Most of the present oxidation reactions shown in Tables 1,
2, and 3 were quenched with dilute hydrochloric acid. When
carbonyl products had acid-sensitive functional groups, satu-
rated aqueous NaHCO3 solution was used for quenching the
present reaction. The same results were obtained when carbon-
yl products were kept stable under these two work-up proce-

228 Bull. Chem. Soc. Jpn., 75, No. 2 (2002)
HEADLINE ARTICLES
Table 4. Effect of Solid Bases on the Oxidation of 2-Phen-
ylethanol (47a) to Phenylacetaldehyde (47b) by Using 4a
Entry
1
2
3
4
5
6
7
8
Base
Yield/%a)
24
DBU (2 mol amt)
MS3A (1 g/mmol)
MS4A (1 g/mmol)
MS5A (1 g/mmol)
CsF (5 mol amt)
MgO (10 mol amt)
CaO (5 mol amt)
BaO (5 mol amt)
TiO2 (5 mol amt)
NiO (5 mol amt)
CuO (5 mol amt)
ZnO (5 mol amt)
Al2O3 (5 mol amt)
21
73(56)b)
35
6
58
56
70
0
trace
37
Scheme 5.
oxidation of 2-phenylethanol (47a) by using 4a and DBU gave
phenylacetaldehyde (47b) in only 24% yield. Swern et al. re-
ported also that the oxidation of 47a by using dimethyl sulfox-
ide, oxalyl chloride, and triethylamine afforded 47b in a low
yield (23%).9b It was assumed that a labile aldehyde 47b de-
composed under those basic oxidation conditions since 3-phen-
ylpropanol was oxidized to 3-phenylpropanal in 94% yield by
using 4a and DBU (Table 3, entry 1). In fact, decomposition
of 47b was observed in the presence of two molar amounts of
DBU, giving a complex mixture. Therefore, it was necessary
to perform this oxidation reaction under nearly neutral condi-
tions, and thus it was planned to use a suitable solid base as a
scavenger of hydrogen chloride.
Solid bases were screened by model oxidation of 47a into a
labile aldehyde 47b by using 1.5 molar amounts of 4a (Table
4). In the first place, molecular sieves 4A (MS4A) was tested
as a solid base since the oxidation of benzyl alcohol (9a) by the
combined use of 4a and MS4A had given good results (Table
1, entries 11 and 12). Similar behavior of MS4A to work as a
neutral scavenger of hydrogen chloride was reported.20 Ex-
pectedly, the yield of 47b was improved from 24% up to 73%
when 1 g/mmol of MS4A was used instead of DBU. Other
types of zeolites such as MS3A and 5A were not as effective as
MS4A. Also, cesium fluoride,21 which is another type of dehy-
drohalogenating agent, was ineffective in this oxidation.
Next, the oxidation was further examined by using several
metal oxides as acid scavengers since solid bases such as mag-
nesium oxide22 and zinc oxide23 were reported to be effective
in Friedel–Crafts type reactions. Of several metal oxides
screened, zinc oxide, which did not work as an oxidant by it-
self, was found to be the most effective acid-scavenger in the
oxidation of 47a. Interestingly, a considerable amount (55%)
of (2-chloroethyl)benzene was detected only in the case of us-
ing NiO (Table 4, entry 10). Because the yield of 47b lowered
considerably when the amount of zinc oxide decreased from
five to two molar amounts, five molar amounts of zinc oxide
were used in all the experiments thereafter.
9
10
11
12
13
91(35)c) (0)d)
trace
a) Determined by GC-analysis using an internal standard.
b) MS4A (3 g/mmol) was used. c) Zinc oxide (2 mol amt)
was used. d) 4a was not used.
present oxidation method of using 4a and zinc oxide (Table 5,
entries 6–15). However, oxidation of secondary alcohols was
slower than that of primary ones, and yields of ketones re-
mained moderate to good.
Since simple primary and secondary alcohols were quite
smoothly oxidized to the corresponding carbonyl compounds
according to the procedure using DBU as a base (Table 5, en-
tries 17–19), oxidation conditions of using 4a and zinc oxide
had an advantage over the above-mentioned procedure of us-
ing DBU only in the oxidations of β-aryl, β-alkoxy, and β-phen-
oxy primary alcohols.
Mechanism. In order to investigate the present oxidation
pathway whether intramolecular or intermolecular proton
transfer took place in the key oxidation step, the oxidation re-
actions using two alkoxysulfonium salts (59 and 61) were tried
(Scheme 6). These two alkoxysulfonium salts25 were prepared
in high yields by selective O-alkylation of the corresponding
sulfinamides (58 and 60) as shown in Scheme 6. It is noted
that the alkoxysulfonium salts having low-nucleophilic counter
anions such as tetrafluoroborate or triflate anion were isolated
as stable salts. On the other hand, it was hard to isolate the
alkoxysulfonium salts when the counter anion was chloride ion
because the nucleophilic substitution by chloride ion took
place as previously described in the oxidation of benzyl alco-
hol (Cf. Scheme 3).
When thus prepared N-monoalkylated sulfonium salt 59
was treated with DBU, octanal (29b) was detected in 88%
yield, as expected (Scheme 6, reaction 2).26 On the other hand,
a similar experiment using N,N-diethylsulfonium salt 61 with
DBU did not afford octanal at all and N-octylated DBU (62)
was obtained in 34% yield along with 41% of sulfinamide 60
and 37% of 61 was recovered (Scheme 6, reaction 3).
Thus, it is noted that alkyl sulfinimidate 5 was the important
intermediate of the oxidation reaction because 5 was easily
It was found that the oxidation of 47a by the combined use
of 4a and zinc oxide was more effective than others, including
Swern,9 a modified Swern,24 PDC,5 and TPAP6 oxidations (Ta-
ble 5, entries 1–5). The oxidation of 47a to 47b with Dess–
Martin periodinate7 proceeded in high yield under wet condi-
tions.7c
Other primary and secondary alcohols involving β-aryl, β-
alkoxy, and β-phenoxy ones were oxidized smoothly by the

J. Matsuo et al.
Bull. Chem. Soc. Jpn., 75, No. 2 (2002) 229
Table 5. Oxidation of Alcohols by Using 4a and Zinc Oxide
Entry
1
Alcohol
Conditions
Yield/%a)
91 (24)
Entry
Alcohol
Conditions
Yield/%a)
52e)
47a 0°C, 30 min
2
3
4
5
Swern Oxidation 23b),73c)
PDC
TPAP/NMO
Dess–Martin
Oxidation
11
12
52a −78 °C, 2 h
31
trace
96
47a
53a
0 °C, 30 min 84
13
14
54a
55a
0 °C, 1 h
rt, 30 min
78
60
6
48a 0 °C, 30 min
94 (0)
15
56a
0 °C, 30 min 78
0 °C, 4 h
78e)
7
8
9
48a
Swern Oxidation 38b)
16
17
18
19
57a
49a 0 °C, 30 min
50a rt, 30 min
91
9a −78 °C, 30 min 90 (98)
28a
36a
0 °C, 30 min 92 (94)
0 °C, 30 min 77 (91)
66 (62)
10
51a 0 °C, 30 min
84d)
a) Determined by GC-analysis using an internal standard unless otherwise noted. Numbers in parentheses were yields of carbonyl
products obtained by the original method of using DBU (2 mol amt) as a base instead of using zinc oxide. b) Ref. 9b. c) By Walba’s
procedure. See Ref. 24. d) Isolated yield of its 2,4-dinitrophenylhydrazone. e) Isolated yield.
Scheme 6.

230 Bull. Chem. Soc. Jpn., 75, No. 2 (2002)
HEADLINE ARTICLES
× 25 m) using helium as carrier gas. Analytical TLC was per-
formed on Merk precoated TLC plates (silica gel 60 GF254, 0.25
mm). Silica-gel column chromatography was carried out on Merk
silica gel 60 (0.063–0.200 mm). Preparative thin-layer chroma-
tography (PTLC) was carried out on silica gel Wakogel B-5F.
Powdered molecular sieves 4A (purchased from nakarai tesque)
was dried in vacuo at 250 °C for 8 h before use. Unless otherwise
noted, commercially available reagents were used without purifi-
cation. Dry solvents were prepared by distillation under appropri-
ate drying agents. Organic bases such as DBU, diisopropylamine,
DABCO, triethylamine, and pyridine were purified by distillation.
4-Methylphenyl thioacetate (7b),27 4-methoxyphenyl thioacetate
(7c),28 8-benzyloxy-1-octanol (30a),29 10-benzyloxy-1-decanol
(31a),30 4-hydroxybutyl benzoate (33a),31 and 6-hydroxyhexyl
benzoate (56a)32 were prepared according to the literature proce-
dures. The oxidation products were identified by comparing those
authentic samples with their GC retention times, spectroscopic
Fig. 1.
formed from N-monoalkylated sulfonium salt 59 by treating
with bases. On the other hand, N,N-diethylsulfonium salt 61
could not form a similar oxidation intermediate. Further, it
was suggested that the oxidation proceeded by five-membered
intramolecular proton-transfer of alkyl sulfinimidate because
N,N-diethylsulfonium salt 61 could not be oxidized when it
was treated with DBU; that is, intermolecular deprotonation of
the octyloxy α-proton had never occurred (Scheme 6, reaction
3, path a). In the case of the oxidation of N-monoalkylated sul-
fonium salt 59, DBU worked only to neutralize 59, and the ni-
trogen of the formed alkyl sulfinimidate 5 directly participated
in the oxidation step via the intramolecular five membered cy-
clic transition state as shown in Fig. 1.
1
data such as H NMR, 13C NMR, and on analytical TLC. Their
derivatization to 2,4-dinitrophenylhydrazones was conducted ac-
cording to Swern’s procedure.33
All reactions were carried out under an atmosphere of argon in
oven-dried glassware with magnetic stirring.
Conclusion.
N,N-Dichloro-t-butylamine (8).14 To a stirred suspension of
t-butylamine (10.0 g, 0.14 mol) and calcium hypochlorite (60%,
68.4 g, 0.29 mol) in dichloromethane (360 mL), 3 M hydrochloric
acid (1 M = 1 mol dm−3) (360 mL) was added dropwise during 1
h at 0 °C. Both liquid phases became yellow and the reaction mix-
ture was stirred for 2 h at the same temperature. The layers were
separated, and an aqueous layer was extracted with dichlo-
romethane (100 mL × 2). The combined organic phases were
washed with H2O and brine, dried over anhydrous Na2SO4, fil-
tered, and concentrated on a rotary evaporator (> 20 kPa) to af-
ford a pale yellow oil (16.9 g, 0.12 mol, 87%). 1H NMR (270
MHz, CDCl3) δ 1.39 (9H, s). 13C NMR (68 MHz, CDCl3) δ
25.80, 72.52.
A new oxidizing agent, N-t-butylbenzenesulfinimidoyl chlo-
ride (4a), efficiently oxidizes a variety of primary and second-
ary alcohols to the corresponding aldehydes and ketones in the
presence of DBU or zinc oxide by simple oxidation proce-
dures. Mechanistic investigations suggested that the oxidation
proceeded via an intermediate, alkyl sulfinimidate 5 which af-
forded the corresponding carbonyl compound by the intramo-
lecular proton transfer via the five-membered cyclic transition
state.
The oxidation using 4a and DBU proceeded under basic
conditions without affecting double bonds, triple bonds, and an
acid labile protecting group such as trimethylsilyl group. By
changing the base from DBU to zinc oxide, the oxidation pro-
ceeded under nearly neutral conditions. Therefore, it was use-
ful for the oxidation giving labile aldehydes and ketones which
readily decompose under basic conditions. Each oxidization
procedure with 4a and DBU or with 4a and zinc oxide has its
own advantages; therefore, an appropriate choice of suitable
oxidation conditions would provide very useful methodologies
in organic synthesis.
N-t-Butylbenzenesulfinimidoyl Chloride (4a).13a
A yellow
solution of S-phenyl thioacetate (7a) (12.2 g, 80.0 mmol) and N,N-
dichloro-t-butylamine (8) (11.9 g, 84.0 mmol) in benzene (80 mL)
was refluxed for 1 h. Volatiles were removed under reduced pres-
sure and by azeotropic distillation with benzene to give 4a as a
red-orange oil (17.2 g, 79.6 mmol, quantitative yield determined
by 1H NMR). This product partially solidified to yellow solid by
keeping it still or by cooling it at 0 °C. The crude product was
used for the present oxidation without further purification. If nec-
essary, it could be purified by careful distillation (112–116 °C/67
Pa). The sulfinimidoyl chloride 4a decomposed at ca. above 160
°C. 1H NMR (270 MHz, dry CDCl3) δ 1.58 (9H, s), 7.5–7.7 (3H,
m), 8.1–8.2 (2H, m). 13C NMR (68 MHz, CDCl3) δ 29.53, 64.15,
125.91, 129.19, 133.17, 142.63.
Experimental
General. All melting points were determined on a Yanagimo-
to micro melting point apparatus (Yanaco MP-S3) and are uncor-
rected. Infrared (IR) spectra were recorded on a Horiba FT300
FT-IR spectrometer. 1H NMR spectra were recorded on a JEOL
EX270 (270 MHz) or a JEOL JNM-LA300 (300 MHz) spectrom-
eter; chemical shifts (δ) are reported in parts per million relative to
tetramethylsilane. Splitting patterns are designated as s, singlet; d,
doublet; t, triplet; q, quartet; m, multiplet; br, broad. 13C NMR
spectra were recorded on a JEOL EX270 (68 MHz) spectrometer
with complete proton decoupling. Chemical shifts are reported in
parts per million relative to tetramethylsilane with the solvent res-
onance as the internal standard (CDCl3; δ 77.0 ppm). High resolu-
tion mass spectra (HRMS) were recorded on a HiTACHI M-80B
or a JEOL JMS-AX505HA mass spectrometer. Analytical gas-
liquid chromatography (GLC) was performed on a Shimadzu GC–
9A instrument equipped with a flame ionizing detector and a cap-
illary column of OV–101 (0.25 mm × 50 m) or CBP10 (0.25 mm
N-t-Butyl-4-methylbenzenesulfinimidoyl Chloride (4b).13a
1H NMR (270 MHz, CDCl3) δ 1.57 (9H, s), 2.44 (3H, s), 7.38
(2H, d, J = 8.1 Hz), 8.01 (2H, dd, J = 1.5, 8.1 Hz). 13C NMR (68
MHz, CDCl3) δ 21.61, 29.57, 64.36, 126.04, 129.93, 139.86,
144.48.
N-t-Butyl-4-methoxybenzenesulfinimidoyl Chloride (4c).
1H NMR (270 MHz, CDCl3) δ 1.57 (9H, s), 3.86 (3H, s), 7.05
(2H, d, J = 9.2 Hz), 8.08 (2H, d, J = 8.9 Hz). 13C NMR (68
MHz, CDCl3) δ 29.35, 55.58, 64.46, 114.53, 128.18, 133.86,
163.68.
Typical Experimental Procedure for Oxidation of Alcohols.
A. Determination of Yields of Carbonyl Products by GC-
Analysis (Table 1, entry 3). A solution of 4a (266 mg, 1.23

J. Matsuo et al.
Bull. Chem. Soc. Jpn., 75, No. 2 (2002) 231
mmol) in CH2Cl2 (1.5 mL) was added to a solution of benzyl alco-
hol (103 mg, 0.82 mmol) and DBU (251 mg, 1.65 mmol) in
CH2Cl2 (1.5 mL) at −78 °C. The reaction mixture was stirred for
30 min at the same temperature and the reaction was quenched by
adding 1% hydrochloric acid (5 mL). The mixture was extracted
with CH2Cl2 (20 mL × 3) and the yield of benzaldehyde was de-
termined by GC-analysis using naphthalene as an internal stan-
dard (0.80 mmol, 98%).
(2,4-Dinitrophenyl)hydrazone Derivative of 2-Pentynal
(24b). Isolated as a yellow solid: mp 91.5–92.5 °C (lit.38 mp 91
°C). 1H NMR (270 MHz, CDCl3) δ 1.36 (3H, t, J = 7.4 Hz), 2.63
(2H, qd, J = 7.4, 1.7 Hz), 6.81 (1H, t, J = 1.7 Hz), 7.94 (1H, d, J
= 9.4 Hz), 8.34 (1H, ddd, J = 9.4, 2.5, 0.7 Hz), 9.13 (1H, d, J =
2.5 Hz), 12.0 (1H, brs). 13C NMR (68 MHz, CDCl3) δ 13.1, 13.4,
70.8, 109.6, 116.9, 123.2, 126.8, 129.7, 129.9, 138.6, 144.1.
2,4-Dinitrophenylhydrazone Derivative of 3-Phenylpropa-
nal (28b). Isolated as a yellow solid: mp 148–149 °C (lit.39 149
B. Isolation of Carbonyl Products by an Acidic Work-Up
Procedure (Table 2, entry 5). To a solution of 15a (117 mg,
0.48 mmol) and DBU (146 mg, 0.96 mmol) in CH2Cl2 (1.5 mL)
was added a solution of 4a (155 mg, 0.72 mmol) in CH2Cl2 (1.5
mL) at −78 °C. After the reaction mixture was stirred at −78 °C
for 30 min, 1% hydrochloric acid (5 mL) was added and the mix-
ture was extracted with CH2Cl2 (20 mL × 3). The combined or-
ganic extracts were washed with H2O and brine, dried over anhy-
drous Na2SO4, filtered, and concentrated in vacuo to afford a crude
product (216 mg), which was purified by column chromatography
on silica gel (hexanes–ethyl acetate, 12/1–5/1) to give 15b (115
mg, 99%) as a colorless solid: mp 138–140 °C (lit.34 144.5 °C).
C. Isolation of Carbonyl Products by a Basic Work-Up
Procedure (Table 2, entry 5). The oxidation of 15a to 15b us-
ing 4a was quenched by adding saturated aqueous NaHCO3 solu-
tion (5 mL) and the mixture was extracted with CH2Cl2 (20 mL ×
3). The combined organic extracts were washed with H2O and
brine, dried over anhydrous Na2SO4, filtered, and concentrated in
vacuo to afford a crude product, which was purified by column
chromatography on silica gel (hexanes–ethyl acetate, 12/1–5/1) to
obtain 15b (99%) as a colorless solid: mp 139–140 °C (lit.34 144.5
°C).
1
°C). H NMR (270 MHz, CDCl3) δ 2.7–2.8 (2H, m), 2.98 (2H, t, J
= 7.3 Hz), 7.00 (0.14H, t, J = 5.1 Hz), 7.2–7.4 (5H, m), 7.56
(0.86H, t, J = 5.1 Hz), 7.90, 7.92 (1H, d, J = 9.5 Hz), 8.2–8.3
(1H, m), 9.12 (1H, dd, J = 0.9, 2.6 Hz), 11.01 (0.86H, brs), 11.14
(0.14H, brs).
2,4-Dinitrophenylhydrazone Derivative of 1-Octanal (29b).
A yellow solid: mp 105–106 °C (lit.40 106 °C). 1H NMR (270
MHz, CDCl3) δ 0.90 (3H, t, J = 6.8 Hz), 1.3–1.6 (8H, m), 1.6–1.7
(2H, m), 2.2–2.4 (2H, m), 6.96 (0.2H, t, J = 5.4 Hz), 7.54 (0.8H, t,
J = 5.4 Hz), 7.93 (0.8H, d, J = 9.5 Hz), 7.96 (0.2H, d, J = 9.5
Hz), 8.30 (0.8H, dd, J = 2.4, 9.5 Hz), 8.33 (0.2H, dd, J = 2.4, 9.5
Hz), 9.12 (0.8H, d, J = 2.4 Hz), 9.14 (0.2H, d, J = 2.4 Hz), 11.01
(0.8H, brs), 11.19 (0.2H, brs).
8-Benzyloxy-1-octanal (30b).41 1H NMR (270 MHz, CDCl3)
δ 1.3–1.4 (5H, m), 1.5–1.7 (5H, m), 2.39 (2H, td, J = 7.4, 1.7 Hz),
3.45 (2H, t, J = 6.4 Hz), 4.48 (2H, s), 7.2–7.3 (5H, m), 9.71 (1H,
t, J = 1.7 Hz).
10-Benzyloxy-1-decanal (31b).42 1H NMR (300 MHz,
CDCl3) δ 1.2–1.5 (10H, m), 1.5–1.7 (4H, m), 2.39 (2H, t, J = 6.5
Hz), 3.45 (2H, t, J = 6.6 Hz), 4.49 (2H, s), 7.2–7.3 (5H, m), 9.73
(1H, s).
1,2-Diphenyl-2-trimethylsiloxyethanol (18a). To a solution
of ( )-1,2-diphenyl-1,2-ethanediol (510 mg, 2.38 mmol) and tri-
ethylamine (242 mg, 2.39 mmol) in dichloromethane (15 mL), a
solution of chlorotrimethylsilane (256 mg, 2.36 mmol) was added
at 0 °C. After the reaction mixture was stirred at room tempera-
ture for 24 h, the reaction was quenched with saturated aqueous
NaHCO3 (10 mL). The mixture was extracted with dichlo-
romethane (10 mL × 3), and combined organic extracts were
dried over anhydrous Na2SO4, filtered, and concentrated in vacuo.
The crude product was purified by column chromatography (silica
gel, hexanes–ether) to afford 18a as a colorless solid (540 mg,
79%): mp 38 °C. IR (KBr, cm−1) 3371, 2900, 1088. 1H NMR
(270 MHz, CDCl3) δ −0.02 (9H, s), 3.32 (1H, brs), 4.56 (1H, d, J
= 7.0 Hz), 4.62 (1H, d, J = 7.0 Hz), 7.0–7.1 (4H, m), 7.1–7.2
(6H, m); 13C NMR (68 MHz, CDCl3) δ −0.04, 79.14, 80.56,
127.02, 127.53, 127.61, 127.81, 127.87, 139.89, 140.63. MS (EI)
m/z 179 (M − PhCwOH+), 107 (PhCwOH+). HRMS Found: m/z
271.1140. Calcd for C17H22O2Si − CH3: 271.1154.
1,2-Diphenyl-2-(trimethylsilyloxy)ethanone (18b). Isolat-
ed as a colorless solid: mp 75–77 °C (lit.35 79–80 °C). Rf 0.67
(hexane–ethyl acetate = 5/1). IR (KBr, cm−1) 1681(CwO). 1H
NMR (270 MHz, CDCl3) δ 0.00 (9H, s), 5.70 (1H, s), 7.14–7.37
(8H, m), 7.86–7.88 (2H, m); 13C NMR (76 MHz, CDCl3) δ 0.00,
79.38, 126.38, 127.94, 128.22, 128.66, 129.64, 132.92, 134.64,
138.80, 198.54.
Dimesityl Ketone (20b). Isolated as a colorless solid: mp
135–137 °C (lit.36 mp 136–137 °C). 1H NMR (300 MHz, CDCl3)
δ 2.12 (12H, s), 2.27 (6H, s), 6.83 (4H, s).
3-Formylpropyl Benzoate (33b).31 1H NMR (270 MHz,
CDCl3) δ 2.11 (2H, tt, J = 6.2, 7.0 Hz), 2.64 (2H, td, J = 7.0, 1.1
Hz), 4.36 (2H, t, J = 6.2 Hz), 7.39–7.59 (3H, m), 7.99–8.05 (2H,
m), 9.83 (1H, t, J = 1.1 Hz); 13C NMR (68 MHz, CDCl3) δ 21.3,
40.4, 63.8, 128.3, 129.4, 129.9, 132.9, 166.3, 201.1.
Oxidation of Cyclohexyloxytrimethylsilane. To
a stirred
solution of cyclohexyloxytrimethylsilane (81.2 mg, 0.47 mmol)
and DBU (143 mg, 0.94 mmol) in dichloromethane (1.5 mL), a
solution of 4a (152 mg, 0.71 mmol) in dichloromethane (1.0 mL)
was added at −78 °C. After the mixture was stirred at −78 °C for
1 h, a cooling bath was removed and the reaction temperature was
gradually raised to room temperature during 30 min. The reaction
was quenched with saturated aqueous NaHCO3, and the mixture
was extracted with dichloromethane. Yields of cyclohexanone
(36b) (0%) and recovered cyclohexyloxytrimethylsilane (> 99%)
were determined by GC-analysis using naphthalene as an internal
standard.
Detection of 6a after the Oxidation Reaction of 9a by Using
4a and DBU (Scheme 4). To a stirred solution of 9a (52.6 mg,
0.49 mmol) and DBU (148 mg, 0.97 mmol) in CH2Cl2 (2 mL), a
solution of 4a (157 mg, 0.73 mmol) in CH2Cl2 (1 mL) was added
at −78 °C. After the reaction mixture was stirred at −78 °C for
30 min, the reaction was quenched with saturated aqueous
NaHCO3 (5 mL), and the mixture was extracted with CH2Cl2 (10
mL × 3). The yield of 9b (93%) was determined by GC-analysis
after adding naphthalene (62.8 mg) as an internal standard. After
the GC-analysis, the organic extracts were dried over anhydrous
Na2SO4, filtered, and concentrated in vacuo to give a crude prod-
uct. Triphenylmethane (100 mg, 0.41 mmol) was added to the
Trifluoromethyl 9-Anthryl Ketone (21b). A colorless sol-
id: mp 82–85 °C (lit.37 mp 81–84 °C). 1H NMR (300 MHz,
CDCl3) δ 7.4–7.6 (4H, m), 7.72 (2H, d, J = 8.4 Hz), 7.97–8.00
(2H, m), 8.52 (1H, s).
1
crude product, and the yield of 6a (95%) was determined by H
NMR. The authentic sample of 6a was prepared according to the
procedure described below.

232 Bull. Chem. Soc. Jpn., 75, No. 2 (2002)
HEADLINE ARTICLES
N-t-Butylbenzenesulfenamide (6a).17 To a stirred solution
of t-butylamine (13.6 g, 185 mmol) in dry ether (150 mL), a solu-
tion of benzenesulfenyl chloride43 (12.2 g, 84.2 mmol) in dry ether
(30 mL) was added dropwise during 30 min at 0 °C. After the re-
action mixture was stirred for 2 h at room temperature, the result-
ing white suspension was filtered and the filtrate was concentrat-
ed. The crude product was distilled (94–95 °C/933 Pa) to give 6a
as a colorless oil (9.53 g, 62%). 1H NMR (270 MHz, CDCl3) δ
1.18 (9H, s), 2.79 (1H, brs), 7.0–7.1 (1H, m), 7.2–7.3 (2H, m),
7.3–7.4 (2H, m). 13C NMR (68 MHz, CDCl3) δ 29.14, 54.71,
122.35, 124.40, 128.34, 144.35.
termined by GC-analysis of the combined organic phase using an
internal standard.
(2,4-Dinitrophenyl)hydrazone Derivative of 2-(4-Methoxy-
phenyl)acetaldehyde (51b). Isolated as orange needles: mp
135–136 °C. 1H NMR (270 MHz, CDCl3) δ 3.69 (2H, d, J = 5.7
Hz), 3.81 (3H, s), 6.88–6.93 (2H, m), 7.56 (1H, t, J = 5.9 Hz),
7.97 (1H, d, J = 9.7 Hz), 8.32 (1H, dd, J = 9.5, 2.2 Hz), 9.12 (1H,
d, J = 2.4 Hz), 11.04 (1H, brs); 13C NMR (68 MHz, CDCl3) δ
38.15, 55.31, 114.37, 114.60, 116.53, 123.45, 127.22, 129.69,
129.98, 145.10, 149.08, 150.64, 158.83. IR (KBr, cm−1) 1612,
1512, 1335. MS (EI) m/z 330 (M+). HRMS (ESI) Found: m/z
330.0970. Calcd for C15H14N4O5: 330.0964.
N-t-Butylbenzenesulfinamide (46). To a mixture of S-phen-
yl thioacetate (1.22 g, 8.01 mmol) and acetic anhydride (0.82 g,
8.03 mmol), sulfuryl chloride (2.20 g, 16.3 mmol) was added
dropwise at 0 °C. After stirring at 0 °C for 8 h, volatiles were re-
moved under reduced pressure to afford a crude benzenesulfinyl
chloride.44 Then, to a solution of the crude benzenesulfinyl chlo-
ride in dichloromethane (10 mL), t-butylamine (1.76 g, 24.1 mol)
was added dropwise at 0 °C. After the reaction mixture was
stirred at room temperature for 1 h, H2O (10 mL) was added and
the mixture was extracted with dichloromethane (20 mL × 3).
Combined organic extracts were washed with saturated aqueous
NaHCO3 (10 mL) and brine, dried over anhydrous Na2SO4, fil-
tered, and concentrated to give a colorless solid (1.48 g). The
crude product was purified by column chromatography (silica gel,
hexanes–AcOEt) to give 12 as a colorless solid (1.20 g, 6.08
mmol, 76%). Recrystallization from hexanes gave 12 as colorless
2-(2-Naphthyl)ethanal (52b).46 Isolated as a colorless oil.
1H NMR (300 MHz, CDCl3) δ 4.10 (2H, d, J = 2.4 Hz), 7.39–7.57
(4H, m), 7.82–7.91 (3H, m), 9.77 (1H, t, J = 2.4 Hz). 13C NMR
(75 MHz, CDCl3) δ 48.33, 123.51, 125.62, 126.05, 126.69,
128.37, 128.39, 128.46, 128.88, 128.89, 133.91, 199.61.
5-Formylpentyl Benzoate (57b).32 Isolated as a colorless
oil. 1H NMR (300 MHz, CDCl3) δ 1.49–1.54 (2H, m), 1.66–1.84
(4H, m), 2.47 (2H, dt, J = 1.8, 7.5 Hz), 4.32 (2H, t, J = 6.6 Hz),
7.41–7.46 (2H, m), 7.52–7.58 (1H, m), 8.02–8.05 (2H, m), 9.77
(1H, t, J = 1.8 Hz); 13C NMR (75 MHz, CDCl3) δ 21.53, 25.49,
28.38, 43.56, 64.51, 128.21, 129.37, 130.18, 132.76, 166.46,
202.28.
N-t-Butylmethanesulfinamide (58). To a stirred solution of
t-butylamine (6.12 g, 83.7 mmol) in CH2Cl2 (40 mL) was added
dropwise a solution of methanesulfinyl chloride47 (3.3 g, 33.5
mmol) in CH2Cl2 (5 mL) at 0 °C. After the white suspension was
stirred for 30 min at room temperature, H2O and NaCl were added
and the mixture was extracted with CH2Cl2. The combined organ-
ic extracts were dried over anhydrous Na2SO4, filtered, and con-
centrated in vacuo. The obtained crude oil was distilled (85–90
°C/2 KPa) to afford 58 (2.87 g, 63%) as a colorless solid. 1H
NMR (270 MHz, CDCl3) δ 1.31 (9H, s), 2.59 (3H, s), 3.72 (1H,
brs); 13C NMR (68 MHz, CDCl3) δ 30.85, 43.95, 53.86. IR (neat,
cm−1) 3487, 1049. MS (EI) m/z 135 (M+). HRMS Found: m/z
135.0723. Calcd for C5H13NOS: 135.0718.
1
leaflets: mp 189–191 °C. H NMR (270 MHz, CDCl3) δ 1.41 (9H,
s), 3.96 (1H, brs), 7.4–7.5 (3H, m), 7.6–7.8 (2H, m). 13C NMR
(68 MHz, CDCl3) δ 30.96, 54.12, 125.49, 128.56, 130.42, 146.39.
IR (KBr, cm−1) 3564, 1412 1088 1041; MS(EI) m/z 197 (M+).
HRMS Found: m/z 198.0947. Calcd for C10H16NOS: 198.0953.
Purification of Formed Aldehyde 30b via a Hydrogensulfite
Addition Compound (Scheme 5). To a stirred mixture of 30a
(131 mg, 0.55 mmol) and DBU (168 mg, 1.11 mmol) in CH2Cl2 (2
mL) was added a solution of 4a (179 mg, 0.83 mmol) in CH2Cl2
(1.5 mL) at 0 °C. After the reaction mixture was stirred for 30 min
at the same temperature, the oxidation reaction was quenched by
adding saturated NaHCO3 (5 mL). The resulting mixture was ex-
tracted with Et2O, and combined organic extracts were then
washed with water.
N-t-Butylamino(methyl)(octyloxy)sulfonium Triflate (59).
To a stirred solution of 58 (2.99 g, 11.4 mmol) in CH2Cl2 (10 mL)
was added a solution of octyl triflate48 (1.54 g, 11.4 mmol) in
CH2Cl2 (15 mL) at room temperature. A slight exothermic reac-
tion was observed. After the reaction mixture was stirred for 42 h
at room temperature, the solvent was removed and the residue was
washed with petroleum ether (5 mL × 5) and dried in vacuo to af-
ford 59 as a colorless oil (4.31 g). Purity of the obtained 59 (99.8
Saturated NaHSO3 solution (2 mL) and THF (8 mL) were add-
ed to the above etheral solution containing 30b, and the mixture
was stirred for 17 h at room tempetature. After evaporation of or-
ganic solvents, the resulting aqueous solution was washed with
Et2O. Then Na2CO3 was added to the washed aqueous phase and
the mixture was stirred for 4 h at room temperature. The mixture
was extracted with Et2O, and the extracts were washed with H2O
and brine, dried over anhydrous Na2SO4, filtered, and concentrat-
ed to give 30b as a colorless oil (95 mg, 73%). Spectrum data of
thus obtained 30b were identical with those of the authentic sam-
ple.
Typical Experimental Procedure for the Oxidation of 47a to
47b by Using 4a and Zinc Oxide (Table 5, entry 1). To a stir-
red white suspension of 47a (70 mg, 0.57 mmol) and zinc oxide45
(233 mg, 2.86 mmol) in dry CH2Cl2 (1.5 mL) was added a solu-
tion of 4a (185 mg, 0.86 mmol) in CH2Cl2 (2 mL) at 0 °C. The re-
action mixture was stirred for 30 min at the same temperature and
then quenched with water (5 mL). The mixture was filtered
through Celite and the Celite pad was washed with CH2Cl2 and
water. The layers were separated and the aqueous phase was ex-
tracted with CH2Cl2. The yield of 47b (0.52 mmol, 91%) was de-
1
wt% purity) was checked by H NMR analysis using triphenyl-
methane as an internal standard and its yield was estimated to be
95%. 1H NMR (270 MHz, CDCl3) δ 0.88 (3H, t, J = 7.1 Hz),
1.27–1.48 (10H, m), 1.42 (9H, s), 1.66–1.76 (2H, m), 3.39 (3H, s),
4.09 (1H, td. J = 6.4, 9.2 Hz), 4.27 (1H, td, J = 6.4, 9.2 Hz), 8.34
(1H, bs). 13C NMR (68 MHz, CDCl3) δ 13.78, 22.33, 25.12,
28.76, 28.90, 29.59, 31.42, 34.06, 34.11, 57.40, 69.08, 120.20 (J
= 319 Hz). MS (FAB+) m/z 248 ([n-BuOSMeNHtBu]+). MS
(FAB−) m/z 149 (OTf−). IR (neat, cm−1) 1242, 1296. HRMS
(ESI positive) Found: m/z 248.2050. Calcd for C13H30NOS:
248.2048.
Oxidation Reaction via 59 (Scheme 6, reaction 2). To a sti-
rred suspension of 59 (99.8% purity, 205 mg, 0.51 mmol) in tolu-
ene (1.5 mL) was added a solution of DBU (86 mg, 0.57 mmol) in
toluene (2 mL) at room temperature, then the reaction mixture was
stirred for 1 h at the same temperature. The reaction was next
quenched with 1% hydrochloric acid and the resulting mixture

J. Matsuo et al.
Bull. Chem. Soc. Jpn., 75, No. 2 (2002) 233
was extracted with CH2Cl2. The yield of octanal (29b, 0.45 mmol,
88%) was determined by GC-analysis using an internal standard.
N,N-Diethylbenzenesulfinamide (60).49 It was prepared ac-
cording to the procedure for the preparation of 46, and isolated as
a colorless oil (82% yield). 1H NMR (270 MHz, CDCl3) δ 1.41
(6H, t, J = 7.3 Hz), 3.14 (4H, q, J = 7.3 Hz), 7.4–7.5 (3H, m),
7.6–7.7 (2H, m). 13C NMR (68 MHz, CDCl3) δ 14.30, 41.94,
126.18, 128.61, 130.45, 144.19.
er-Verlag, New York (1984). f) W. J. Mijs and C. R. H. de Jonge,
“Organic Synthesis by Oxidation with Metal Compounds,” Ple-
num, New York (1986). g) “Comprehensive Organic Synthesis,”
ed by B. M. Trost, Pergamon Press, Oxford (1991), Vol. 7, pp.
251, 291 and 305.
2
a) K. Bowden, I. M. Heilbron, E. R. H. Jones, and B. C. L.
Weedon, J. Chem. Soc., 1946, 39. b) A. Bowers, T. G. Halsall, E.
R. H. Jones, and A. J. Lemin, J. Chem. Soc., 1953, 2548.
N,N-Diethylamino(octyloxy)(phenyl)sulfonium Triflate (61).
To the stirred solution of 60 (334 mg, 2.47 mmol) in CH2Cl2 (2
mL) was added a solution of octyl triflate (712 mg, 2.72 mg) at
room temperature. After the mixture was stirred at the same tem-
perature for 43 h, the solvent was evaporated and the residue was
washed with petroleum ether (5 mL × 5) and dried in vacuo to af-
ford N,N-diethylamino(octyloxy)(phenyl)sulfonium triflate (61) as
a colorless oil (91% yield, 94% purity which was determined by
3
J. C. Collins, W. W. Hess, and F. J. Frank, Tetrahedron
Lett., 1968, 3363.
4
a) E. J. Corey and J. W. Suggs, Tetrahedron Lett., 1975,
2647. b) G. Piancatelli, A. Scettri, and M. D’Auria, Synthesis,
1982, 245.
5
e) E. J. Corey and G. Schmidt, Tetrahedron Lett., 1979,
399. b) S. Czernecki, C. Georgoulis, C. L. Stevens, and K.
Vijayakumaran, Tetrahedron Lett., 26, 1699 (1985).
1
1H NMR using an internal standard). H NMR (270 MHz, CDCl3)
6
a) W. P. Griffith, S. V. Ley, G. P. Whitcombe, and A. D.
δ 0.88 (3H, t, J = 6.5 Hz), 1.27–1.44 (16H, m), 1.86–1.96 (2H,
m), 3.54 (4H, m), 4.52 (1H, td, J = 6.5, 9.7 Hz), 4.62 (1H, td, J =
6.5, 9.7 Hz). 13C NMR (68 MHz, CDCl3) δ 11.0, 13.9, 22.5, 25.3,
28.9, 29.7, 31.6, 43.2, 45.5, 76.2, 120.7 (q, J = 318 Hz), 127.9,
129.5, 130.8, 134.8. IR (neat, cm−1) 1242, 1273. HRMS (ESI
positive) Found: m/z 310.2207. Calcd for C18H32NOS: 310.2205.
8-Octyl-1,8-diazabicyclo[5.4.0]undec-7-ene Trifluorometh-
anesulfonate (62). To the stirred solution of 61 (216 mg, 0.44
mmol) in toluene (1.5 mL) was added a solution of DBU (84 mg,
0.55 mmol) in toluene (2.0 mL) at room temperature. After the re-
action mixture was stirred at the same temperature for 1 h, 1%
hydrochloric acid was added to the reaction mixture, and the re-
sulting mixture was extracted with CH2Cl2. Octanal (29b) was not
detected in the combined CH2Cl2 extracts by GC-analysis. The
combined CH2Cl2 solution was dried over anhydrous Na2SO4, fil-
tered, and concentrated in vacuo. The residue was purified by thin
layer chromatography (silica gel, elution with CHCl3–MeOH,
5:1) to give recovered 61 (74 mg, 0.16 mmol, 37%), 60 (36 mg,
0.18 mmol, 41%), and 8-octyl-1,8-diazabicyclo[5.4.0]-7-undec-7-
ene trifluoromethanesulfonate (62) (62 mg, 0.15 mmol, 34%) as
colorless oils. 62: 1H NMR (270 MHz, CDCl3) δ 0.88 (3H, t, J =
6.4 Hz), 1.29–1.30 (10H, m), 1.62–1.79 (8H, m), 2.09–2.17 (2H,
m), 2.84 (2H, d, J = 9.2 Hz), 3.45–3.69 (8H, m). 13C NMR (68
MHz, CDCl3) δ 14.0, 20.0, 22.5, 23.0, 25.9, 26.4, 28.3, 28.5, 28.6,
29.0, 29.0, 31.6, 47.0, 49.0, 54.1, 55.2, 120.8 (q, J = 318 Hz),
166.5. HRMS (ESI positive) Found: m/z 265.2637. Calcd for
C17H33N2: 265.2644.
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The present research was partially supported by Grants-in-
Aid for Scientific Research from the Ministry of Education,
Culture, Sports, Science and Technology. The authors wish to
thank Dr. Hirokazu Ohsawa, Banyu Pharmaceutical Company,
for his kind help for mass spectrometry analysis.
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V. Kirsanov, J. Org. Chem. USSR, 9, 1435 (1973).
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