Burgess Reagent Facilitated Alcohol Oxidations in DMSO

Article abstract of DOI:10.1021/acs.joc.6b02629

The Burgess reagent ([methoxycarbonylsulfamoyl]triethylammonium hydroxide) has historically found utility as a dehydrating agent. Herein we show that, in the presence of dimethyl sulfoxide, the Burgess reagent efficiently and rapidly facilitates the oxidation of a broad range of primary and secondary alcohols to their corresponding aldehydes and ketones in excellent yields and under mild conditions, and can be combined with other transformations (e.g., Wittig olefinations). A mechanism similar to those described for the Pfitzner-Moffatt and Swern oxidations is proposed.

Full text of DOI:10.1021/acs.joc.6b02629

Article
pubs.acs.org/joc
Burgess Reagent Facilitated Alcohol Oxidations in DMSO
Prakash R. Sultane† and Christopher W. Bielawski*,†,‡
†Center for Multidimensional Carbon Materials (CMCM), Institute for Basic Science (IBS), Ulsan 44919, Republic of Korea
‡Department of Chemistry and Department of Energy Engineering, Ulsan National Institute of Science and Technology (UNIST),
Ulsan 44919, Republic of Korea
S
* Supporting Information
ABSTRACT: The Burgess reagent ([methoxycarbonyl-
sulfamoyl]triethylammonium hydroxide) has historically found
utility as a dehydrating agent. Herein we show that, in the
presence of dimethyl sulfoxide, the Burgess reagent efficiently and
rapidly facilitates the oxidation of a broad range of primary and
secondary alcohols to their corresponding aldehydes and ketones
in excellent yields and under mild conditions, and can be combined with other transformations (e.g., Wittig olefinations). A
mechanism similar to those described for the Pfitzner−Moffatt and Swern oxidations is proposed.
its use in late stage transformations found in the total syntheses
of numerous natural products.8 The Burgess reagent has also
been used to convert 1,2-diols into 1,2-amino alcohols and has
facilitated the synthesis of α- and β-glycosylamines.9 Several
reviews that highlight the utility of 1 as well as its derivatives6,7
are currently available.10
INTRODUCTION
■
In 1968, Atkins and Burgess reported the synthesis of the inner
salt [methoxycarbonylsulfamoyl]triethylammonium hydroxide
(1) and described its utility in facilitating alcohol dehydrations.1
Subsequently, the aforementioned compound, which is now
colloquially referred to as the “Burgess reagent”, has been
successfully employed as a selective and mild dehydrating agent
for a broad range of secondary (e.g., see Figure 1) and tertiary
At nearly the same time that the Burgess reagent was
introduced, Parikh and Doering reported11 (1967) that the
sulfur trioxide pyridine complex (C5H5N·SO3) activates
dimethyl sulfoxide (DMSO) in the presence of a base (e.g.,
Et3N) and facilitates the oxidation of primary and secondary
alcohols. While the Parikh−Doering oxidation reaction
operates under mild conditions, relatively large excesses (3−6
equiv) of pure C5H5N·SO3 are required and, as a result, other
activated DMSO-mediated oxidations are often favored.12
We hypothesized that 1, which upon the liberation of
triethylamine, should generate an electrophilic dioxosulfimidi-
num species that may activate DMSO and facilitate oxidation
reactions. Herein we report that the Burgess reagent may be
used to oxidize primary and secondary alcohols to their
respective aldehydes and ketones in the presence of DMSO.13
The reaction is rapid (minutes), operates under mild conditions
(room temperature), and affords high yields of products from a
broad range of functionally diverse starting materials.
RESULTS AND DISCUSSION
■
Figure 1. Various uses of the Burgess reagent (1).
In an initial experiment, benzyl alcohol ([BnOH]0 = 0.5 M)
was treated with 2 equiv of 1 in anhydrous DMSO at room
temperature (Scheme 1).14 After 5 min, 1H NMR spectroscopic
analysis of the crude reaction mixture indicated that
benzaldehyde (3a) was formed in quantitative yield along
with dimethyl sulfide. Subsequent efforts were directed toward
optimizing the reaction. After dissolving benzyl alcohol
alcohols1 as well as a reagent for converting primary alcohols,
primary amides, formamides, and primary nitroalkanes into
their respective urethanes,1 nitriles,2 isocyanides,3 and nitrile
oxides.4 The compound has also been employed in cyclo-
dehydrations,5 which have been particularly useful in peptide
modification chemistry, and for the preparation of sulfamides6
and cyclic sulfamidates7a from their corresponding amines and
epoxides. The mild and selective nature of 1 is underscored by
Received: October 31, 2016
© XXXX American Chemical Society
A
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a
Scheme 1. Oxidation of Benzyl Alcohol to Benzaldehyde
Scheme 3. Oxidation of Secondary Alcohols
([BnOH]0 = 0.5 M) in anhydrous DMSO at room temper-
ature, 1 equiv of the Burgess reagent was added to the solution.
Analysis of the crude reaction mixture using 1H NMR
spectroscopy revealed that the benzyl alcohol was completely
consumed within 5 min; benzaldehyde was subsequently
isolated in 94% yield. Likewise, 80% of 1-phenylethanol was
converted to acetophenone within 5 min upon treatment with 1
equiv of 1 under the aforementioned conditions and
quantitative formation of the ketone was observed when 1.3
equiv of 1 was used. The formation of mixed thioacetals12 (e.g.,
4), a common side product found in activated DMSO-based
oxidations, or urethanes1 were not observed.
Based on the aforementioned results, we concluded that 1.3
equiv of the Burgess reagent with respect to the alcohol
substrate was sufficient and practical. As summarized in
Schemes 2 and 3, a broad range of primary and secondary
alcohols were successfully oxidized and their corresponding
aldehydes and ketone products in high isolated yields. Over-
oxidation of the aldehydes to the corresponding carboxylic
acids was not observed. Likewise, olefinic products were not
a
Isolated yields are shown in parentheses. All reactions were
performed using 1 mmol of alcohol and 1.3 mmol of the Burgess
reagent in anhydrous DMSO (2 mL) at room temperature for 5 min.
b
Isolated as its 2,4-dinitrophenylhydrazone derivative.
detected when secondary alcohols containing α-hydrogens were
subjected to the reaction conditions. The reaction also
appeared to show good tolerance to functional groups as
substrates containing carboxylic acids, esters, aryl ethers, or
amides were successfully oxidized. Finally, the mild and
selective nature of the transformation was probed with N-
Cbz-(S)-phenylalaninol (CBz = carboxybenzyl); the corre-
sponding aldehyde 3o was obtained in excellent yield and
without epimerization.15
a
Scheme 2. Oxidation of Primary Alcohols
To gain a deeper understanding of the oxidation reaction, a
series of control experiments were performed. When benzyl
alcohol was treated with the Burgess reagent (1.3 equiv) and
excess diphenylsulfoxide, a disubsituted sulfoxide devoid of α-
hydrogens, in CH2Cl2 the formation of benzaldehyde was not
1
detected. Likewise, no reaction was observed by H NMR
spectroscopy when trityl alcohol was introduced to the Burgess
reagent in the presence of DMSO.16
As derivatives of the Burgess reagent are known,6,7 a series
containing different amines were prepared (see Figure 2) and
Figure 2. Structures of modified Burgess reagents.
explored for their abilities to facilitate the oxidations of alcohols.
Under otherwise identical conditions to those described above,
no reaction was observed when benzyl alcohol was treated with
6a, even after extended periods of time (up to 12 h). However,
at elevated temperatures (60 °C), benzaldehyde (3a) and
thioacetal 4 were formed in 93% and 7% yield, respectively, as
determined by H NMR spectroscopy. Similarly, no reaction
was observed when benzyl alcohol was treated with 6b at room
temperature, even after 12 h, although small quantities of the
a
Isolated yields are shown in parentheses. All reactions were
1
performed using 1 mmol of alcohol and 1.3 mmol of the Burgess
reagent in anhydrous DMSO (2 mL) at room temperature for 5 min.
b
Isolated as its 2,4-dinitrophenylhydrazone derivative.
B
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a
aldehyde product (10% conversion) were observed at 60 °C.
The most effective derivative tested was 6c, which was found to
convert 88% of the starting material to the expected product at
room temperature. Collectively, these results indicated that the
use of Burgess-type reagents containing relatively basic amines
are needed to facilitate alcohol oxidations in DMSO.
Scheme 5. Summary of Competition Experiments
Next, the versatility of the aforementioned methodology was
probed by combining Burgess reagent-facilitated oxidations
with Wittig olefinations to access γ-amino esters in a single pot.
When N-Boc-(S)-valinol (Boc = tert-butyloxycarbonyl) (1
mmol) was treated with 1 (1.3 mmol) in DMSO (4 mL)
followed by the addition of the Wittig reagent 7d (1.5 mmol),
the corresponding unsaturated ester 7a was isolated in good
yield (78%) and without racemization (Scheme 4).17 The
reaction conditions were found to tolerate CBz protecting
groups as well (c.f., 7b and 7c).
Scheme 4. One Pot Alcohol Oxidation/Wittig Olefination
Approach to γ-Amino Esters
a
a
All reactions were performed using 0.1 mmol of each alcohol and
0.13 mmol of the Burgess reagent in DMSO-d6 (0.6 mL) at room
temperature for 5 min. Conversions were determined by H NMR
1
spectroscopy
Scheme 6. Proposed Mechanism for the Oxidation of
Alcohols Using the Burgess Reagent in DMSO
a
Isolated yields are shown in parentheses. All reactions were
performed using 1 mmol of alcohol, 1.3 mmol of the Burgess reagent
and 1.5 mmol of the Wittig reagent in anhydrous DMSO (4 mL) at
room temperature for 3 h.
To elucidate of the oxidation mechanism, the kinetics of
1
various alcohol oxidation reactions were evaluated using H
NMR spectroscopy. The conversions of benzyl alcohol (kinit
=
2.4 × 10−2 mM−1 s−1), 4-methoxyphenylmethanol (kinit = 3.4 ×
10−2 mM−1 s−1), 4-trifluorophenylmethanol (kinit = 1.8 × 10−2
mM−1 s−1), and benzyl alcohol-α,α-d2 (kinit = 2.2 × 10−2 mM−1
s−1) to their respective products were independently monitored
over time (conditions: [alcohol]0 = 35 mM, [1]0 = 46.2 mM,
[1,3,5-trimethoxybenzene (internal standard)]0 = 35 mM,
DMSO-d6, 21 °C). Collectively, the kinetic studies revealed
that electron rich alcohols react faster than their electron
deficient congeners, at least during the early stages of the
reaction. Moreover, the initial rate constant measured for the
oxidation of benzyl alcohol was nearly the same as its
deuterated analogue, which excluded cleavage of the C−
H(D) bond as the rate-determining step. To verify the kinetics
data, series of competition experiments were performed. As
summarized in Scheme 5, electron rich alcohols afforded higher
conversions to their corresponding products when compared to
their electron deficient analogues. Likewise, subjecting an
equimolar mixture of benzyl alcohol and a deuterated analogue
to the Burgess reagent afforded the respective benzaldehyde
products in nearly a 1:1 ratio. Collectively, the data suggested
to us that the rate-determining step involved nucleophilic attack
of the alcohol on an activated substrate.
react with 8 to form an alkoxysulfonium intermediate (9),
which subsequently undergoes deprotonation. Decomposition
of the resulting ylide (10) should afford the carbonyl containing
compound as well as dimethyl sulfide, which was observed by
1H NMR spectroscopy (vide supra).18
Overall, the oxidation mechanism is similar to those
described for the Pfitzner−Moffatt19 and Swern oxidations
although it may proceed with a different rate-determining step.
For example, the rate-determining step of the Swern oxidation
has been reported to be deprotonation of the alkoxysulfonium
intermediate to form the corresponding ylide.12 As a result, the
Swern and related oxidations typically involve a series of timed
reagent additions and are conducted at low temperatures (−78
°C). In comparison, the methodology described herein can be
performed in one pot as all requisite activation agents are
generated in situ and conducted at room temperature.
In conclusion, we have discovered that the Burgess reagent, a
compound that has historically found utility as a dehydrating
agent, may be used to oxidize primary and secondary alcohols
to their corresponding aldehydes and ketones in dimethyl
sulfoxide. The reactions were found to be rapid, operated under
mild conditions, and afforded oxidized products in excellent
isolated yields. The methodology is advantageous to others in
that it is convenient and broadly useful, the oxidation reaction
Based on the aforementioned results, an oxidation
mechanism was deduced and is proposed in Scheme 6. The
reaction may start with the attack of DMSO on the Burgess
reagent to afford sulfonium ion 8. Benzyl alcohol may then
C
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complete (∼1 h), the triethylammonium hydrochloride precipitate was
removed by filtration, and the filtrate was concentrated to give 1 as an
off-white solid (21.7 g, 86% yield). mp 71−73 °C; IR (ATR): νco 1686,
1440, 1327, 1245, 1108; 1H NMR (400 MHz, CDCl3): δ 3.69 (s, 3H),
3.47 (q, J = 7.3 Hz, 6H), 1.41 (t, J = 7.3 Hz, 9H); 13C NMR (100
MHz, CDCl3): δ 158.4, 53.4, 50.6, 9.5; HRMS (ESI): m/z calcd for
C8H18N2O4SNa [M+Na]+, 261.0879; found, 261.0849.
does not evolve toxic byproducts (e.g., carbon monoxide), low
temperatures or timed additions are not required, and the
oxidation agent is commercially available.
EXPERIMENTAL SECTION
■
General Considerations. Unless otherwise specified, all reagents
were purchased from commercial sources and used without further
purification. Solvents were dried and degassed using a solvent
purification system. Aluminum-backed plates precoated with silica
gel 60F254 were used for thin layer chromatography and were
visualized with a UV lamp or by staining with 2,4-dinitrophenylhy-
Benzaldehyde (3a).20 Using Procedure A afforded 0.1 g (94%
yield) of the desired product as a colorless liquid. 1H NMR (400 MHz,
CDCl3): δ 10.02 (s, 1H), 7.89−7.87 (m, 2H), 7.65−7.61 (m, 1H),
7.55−7.51 (m, 2H); 13C NMR (100 MHz, CDCl3): δ 192.5, 136.5,
134.6, 129.9, 129.1; GCMS (EI): m/z 106.
drazine. H NMR and 13C NMR spectra were recorded in CDCl3
4-Methoxybenzaldehyde (3b).21 Using Procedure A afforded 0.13
1
1
(internal standard: 7.26 ppm, H; 77.2 ppm, 13C), CD2Cl2 (internal
1
g (94% yield) of the desired product as a colorless liquid. H NMR
standard: 5.32 ppm, 1H; 54.0 ppm, 13C), acetone-d6 (internal standard:
2.05 ppm, 1H; 29.8 ppm, 13C), or DMSO (internal standard: 2.5 ppm,
1H; 39.5 ppm, 13C) using 400 and 100 MHz spectrometers,
respectively. Coupling constants (J) are expressed in hertz (Hz).
Gas chromatograph mass spectrometry data were obtained with a
GCMS spectrometer. High-resolution mass spectrometry (HRMS)
data were obtained on a time-of-flight instrument. Optical rotations
were determined using a polarimeter. Melting points are uncorrected.
General Procedures. Procedure A. A 25 mL Schlenk flask
outfitted with a septum was charged with an alcohol (1 mmol),
anhydrous DMSO (2 mL), and a stir bar. To the resulting solution was
added freshly prepared Burgess reagent (1.3 mmol). After stirring the
resulting mixture at ambient temperature for 5 min, the reaction
mixture was diluted with diethyl ether and water. The organic layer of
the mixture was isolated and the aqueous layer was washed twice with
diethyl ether. The combined organic layers were washed with brine,
dried over anhydrous Na2SO4, and concentrated under reduced
pressure. The residue was purified by silica gel column chromatog-
raphy (n-pentane: Et2O, 9:1 v/v).
Procedure B. A 25 mL Schlenk flask outfitted with a septum was
charged with an alcohol (1 mmol), anhydrous DMSO (2 mL), and a
stir bar. To the resulting solution was added freshly prepared Burgess
reagent (1.3 mmol). After 5 min, the resulting mixture was poured
onto ice. The precipitate was filtered, washed with cold water, and
dried under reduced pressure to afford pure product.
Procedure C. A 25 mL Schlenk flask outfitted with a septum was
charged with an alcohol (1 mmol), anhydrous DMSO (2 mL), and a
stir bar. To the resulting solution was added freshly prepared Burgess
reagent (1.3 mmol). After stirring at ambient temperature for 5 min,
the reaction mixture was diluted with ethanol and H2O. Next, 2,4-
dinitrophenyl hydrazine (1.05 mmol) was added followed by conc.
H2SO4 (0.2 mL) and the resulting reaction mixture was stirred for
another 10 min. Formation of the hydrazone was indicated by
appearance of an orange precipitate, which was filtered, washed with
cold water, collected, and dried under reduced pressure.
Procedure D. A 25 mL Schlenk flask outfitted with a septum was
charged with an alcohol (1 mmol), anhydrous DMSO (4 mL), and a
stir bar. To the resulting solution was added freshly prepared Burgess
reagent (1.3 mmol) followed by a Wittig salt (1.5 mmol). After stirring
the resulting mixture at ambient temperature for 3 h, the reaction
mixture was diluted with diethyl ether and water. The organic layer of
the mixture was isolated and the aqueous layer was washed twice with
diethyl ether. The combined organic layers were washed with brine,
dried over anhydrous Na2SO4, and concentrated under reduced
pressure. The residue was purified by silica gel column chromatog-
raphy (n-hexane:EtOAc, 9:1 v/v).
The Burgess Reagent (1). Following procedures reported in the
literature,1d−f a solution of chlorosulfonylisocyanate (9.23 mL, 106
mmol) in benzene (50 mL) at 0 °C was added to a solution of
methanol (4.5 mL, 111.3 mmol) in benzene (20 mL) over the course
of 30 min. Once the addition was complete, the residual solvent was
removed from the reaction mixture under reduced pressure to give the
desired sulfamoyl chloride intermediate as a white solid. A solution of
the newly formed sulfamoyl chloride in a benzene:toluene mixture (50
mL:50 mL) was added dropwise to a solution of Et3N (33.2 mL, 238.5
mmol) in benzene (150 mL) at 25 °C. After the addition was
(400 MHz, CDCl3): δ 9.87 (s, 1H), 7.82 (d, J = 8.8 Hz, 2H), 6.99 (d, J
= 8.8 Hz, 2H), 3.87 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 190.1,
164.7, 132.1, 130.1, 114.4, 55.7; GCMS (EI): m/z 136.
4-Trifluoromethylbenzaldehyde (3c).22 Using Procedure A af-
forded 0.15 g (89% yield) of the desired product as a colorless liquid.
1H NMR (400 MHz, CDCl3): δ 10.11 (s, 1H), 8.0 (d, J = 8.0 Hz, 2H),
7.80 (d, J = 8.1 Hz, 2H); 13C NMR (100 MHz, CDCl3): δ 191.3,
138.9, 135.7 (q, J = 32.7 Hz), 130.1, 126.2 (q, J = 3.8 Hz), 123.6 (q, J
= 272.9 Hz); GCMS (EI): m/z 174.
4-Nitrobenzaldehyde (3d).22 Using Procedure B afforded 0.142 g
1
(94% yield) of the desired product as a light yellow solid. H NMR
(400 MHz, CDCl3): δ 10.16 (s, 1H), 8.40 (d, J = 8.7 Hz, 2H), 8.08 (d,
J = 8.7 Hz, 2H); 13C NMR (100 MHz, CDCl3): δ 190.4, 151.3, 140.2,
130.6, 124.5; GCMS (EI): m/z 151.
4-Formylbenzoic Acid (3e).23 A 25 mL Schlenk flask outfitted with
a septum was charged with the corresponding alcohol (1 mmol),
anhydrous DMSO (2 mL), and a stir bar. To the resulting solution was
added freshly prepared Burgess reagent (1.3 mmol). After stirring at
ambient temperature for 5 min, the reaction mixture was quenched by
the addition of 1 N HCl (aq.). The mixture was then diluted with
diethyl ether and water. The organic layer was isolated and the
aqueous layer was washed twice with diethyl ether. The combined
organic layers were washed with brine, dried over anhydrous Na2SO4,
and concentrated under reduced pressure. Purification of the residue
by silica gel column chromatography (n-pentane:Et2O, 7:3 v/v)
afforded 0.14 g (92%) of the desired product as an off-white solid. 1H
NMR (400 MHz, DMSO-d6): δ 10.10 (s, 1H), 8.13 (d, J = 8.2 Hz,
2H), 8.01 (d, J = 8.2 Hz, 2H); 13C NMR (100 MHz, DMSO-d6): δ
193.1, 166.6, 138.8, 136.0, 129.9, 129.6; MS (ESI) [M−H]+: m/z 149.
Methyl 4-Formylbenzoate (3f).24 Using Procedure B afforded 0.15
1
g (94% yield) of the desired product as an off-white solid. H NMR
(400 MHz, CDCl3): δ 10.10 (s, 1H), 8.20 (d, J = 8.3 Hz, 2H), 7.95 (d,
J = 8.5 Hz, 2H), 3.96 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 191.8,
166.2, 139.3, 135.2, 130.3, 129.7, 52.7; MS (ESI) [M+H]+: m/z 165.
N-Benzyl-4-formylbenzamide (3g).25 Using Procedure B afforded
1
0.15 g (92% yield) of the desired product as an off-white solid. H
NMR (400 MHz, CDCl3): δ 10.08 (s, 1H), 7.95 (s, 4H), 7.39−7.31
(m, 5H), 6.43 (bs, 1H), 4.66 (d, J = 5.6 Hz, 2H); 13C NMR (100
MHz, CDCl3): δ 191.6, 166.4, 139.7, 138.4, 137.8, 130.0, 129.0, 128.2,
128.0, 127.8, 44.5; MS (ESI) [M+H]+: m/z 240.
Picolinaldehyde (3h).26 Using Procedure A afforded 95 mg (88%
1
yield) of the desired product as a pale yellow liquid. H NMR (400
MHz, CDCl3): δ 10.06 (s, 1H), 8.77 (d, J = 4.7 Hz, 1H), 7.94 (d, J =
7.7 Hz, 1H), 7.86 (t, J = 7.6 Hz, 1H), 7.60−7.41 (m, 1H); 13C NMR
(100 MHz, CDCl3): δ 193.5, 153, 150.3, 137.2, 128, 121.8; GCMS
(EI): m/z 107.
Cinnamaldehyde (3i).21 Using Procedure A afforded 0.12 g (91%
yield) of the desired product as a colorless liquid. 1H NMR (400 MHz,
CDCl3): δ 9.72 (d, J = 7.7 Hz, 1H), 7.63−7.54 (m, 2H), 7.49 (d, J =
15.9 Hz, 1H), 7.46−7.43 (m, 3H), 6.73 (dd, J = 15.9, 7.7 Hz, 1H); 13C
NMR (100 MHz, CDCl3): δ 193.9, 153.0, 134.2, 131.4, 129.23, 128.8,
128.6; GCMS (EI): m/z 132.
3-Phenylpropiolaldehyde (3j).27 Using Procedure A afforded 0.116
1
g (89% yield) of the desired product as a colorless liquid. H NMR
(400 MHz, CDCl3): δ 9.43 (s, 1H), 7.97−7.56 (m, 2H), 7.56−7.46
D
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(m, 1H), 7.45−7.36 (m, 2H); 13C NMR (100 MHz, CDCl3): δ 176.9,
133.4, 131.4, 128.9, 119.6, 95.3, 88.6; GCMS (EI): m/z 130.
6-Bromohexanal (3k).28 Using Procedure A afforded 0.15 g (88%
yield) of the desired product as a colorless liquid. 1H NMR (400 MHz,
CDCl3): δ 9.78 (t, J = 1.6 Hz, 1H), 3.41 (t, J = 6.7 Hz, 2H), 2.47 (td, J
= 7.2, 1.6 Hz, 2H), 1.93−1.82 (m, 2H), 1.71−1.61 (m, 2H), 1.53−1.43
(m, 2H); 13C NMR (100 MHz, CDCl3): δ 202.3, 43.8, 33.5, 32.6, 27.8,
21.3; GCMS (EI): m/z 178.
7.20−7.07 (m, 2H), 3.62 (dd, J = 12.1, 5.4 Hz, 1H), 2.92−2.39 (m,
2H), 2.28 (m, 1H), 2.23−1.94 (m, 3H), 1.93−1.73 (m, 2H); 13C
NMR (100 MHz, CDCl3): δ 210.4, 138.9, 128.7, 128.5, 127.0, 57.5,
42.4, 35.2, 28, 25.5; GCMS (EI): m/z 174.
1-Phenylpropan-2-one (5h).35 Using Procedure A afforded 0.12 g
(87% yield) of the desired product as a colorless liquid. 1H NMR (400
MHz, CDCl3): δ 7.37−7.32 (m, 2H), 7.31−7.25 (m, 1H), 7.24−7.19
(m, 2H), 3.70 (s, 2H), 2.16 (s, 3H); 13C NMR (100 MHz, CDCl3): δ
206.6, 134.4, 129.5, 128.9, 127.2, 51.2, 29.4; GCMS (EI): m/z 134.
1-(2,4-Dinitrophenyl)-2-(propan-2-ylidene)hydrazine (5i).36 Using
Procedure C afforded 0.2 g (85% yield) of the desired product as an
orange solid. 1H NMR (400 MHz, CDCl3): δ 11.05 (s, 1H), 9.15 (d, J
= 2.6 Hz, 1H), 8.32 (ddd, J = 9.6, 2.6, 0.8 Hz, 1H), 7.98 (d, J = 9.6 Hz,
3H), 2.20 (s, 3H), 2.11 (s, 3H); 13C NMR (100 MHz, CDCl3): δ
155.3, 145.3, 137.8, 130.2, 123.7, 116.5, 25.7, 17.2; HRMS (ESI): m/z
calcd for C9H11N4O4 [M+H]+: 239.0775; found, 239.0776.
(E)-1-(2,4-Dinitrophenyl)-2-(3-methylbutylidene)hydrazine (3l).29
Using Procedure C afforded 0.23 g (86% yield) of the desired product
as an orange solid. 1H NMR (400 MHz, CDCl3): δ 11.03 (s, 1H), 9.12
(d, J = 2.6 Hz, 1H), 8.30 (ddd, J = 9.6, 2.6, 0.8 Hz, 1H), 7.94 (d, J =
9.6 Hz, 1H), 7.53 (t, J = 5.8, 1H), 2.32 (dd, J = 6.9, 5.8 Hz, 2H), 1.98
(m, 1H), 1.02 (d, J = 6.7 Hz, 6H); 13C NMR (100 MHz, CDCl3): δ
152.1, 150.7, 145.3, 138.0, 130.1, 123.7, 117.0, 41.4, 36.4, 26.9, 22.6;
MS (ESI) [M+H]+: m/z 267.1127.
Decanal (3m).30 Using Procedure A afforded 0.14 g (91% yield) of
the desired product as a colorless liquid. 1H NMR (400 MHz, CDCl3):
δ 9.76 (t, J = 1.9 Hz, 1H), 2.41 (td, J = 7.4, 1.9 Hz, 2H), 1.82−1.56 (m,
2H), 1.45−1.19 (m, 12H), 0.86 (t, J = 8 Hz, 3H); 13C NMR (100
MHz, CDCl3): δ 203.1, 44.1, 32.0, 29.53, 29.50, 29.4, 29.3, 22.8, 22.4,
14.2; GCMS (EI): m/z 156.
((4-(Dimethyliminio)pyridin-1(4H)-yl)sulfonyl)(methoxycarbonyl)-
amide (6a). This compound was prepared according to a modified
literature procedure.37 To a solution of methanol (0.28 mL, 7.06
mmol) in CH2Cl2 (10 mL) at 0 °C was added chlorosulfonylisocya-
nate (1 g, 7.06 mmol) dropwise (∼10 min). Once the addition was
complete, 4-dimethylaminopyridine (1.72 g, 14.12 mmol) was added.
After stirring the resulting mixture at ambient temperature for 2 h, it
was diluted with H2O. The organic layer was isolated and the aqueous
layer was washed twice with CH2Cl2 (30 mL). The combined organic
layers were washed with brine, dried over anhydrous Na2SO4, and
concentrated under reduced pressure to afford 1.42 g (78%) of 6a as
off-white solid. m.p.: 161−163 °C; IR (ATR): νco 1662, 1627, 1560,
Palmitaldehyde (3n).31 Using Procedure A afforded 0.22 g (93%
1
yield) of the desired product as an off-white solid. H NMR (400
MHz, CDCl3): δ 9.76 (t, J = 1.9 Hz, 1H), 2.41 (td, J = 7.4, 1.9 Hz,
2H), 1.80−1.52 (m, 2H), 1.47−1.13 (m, 24H), 0.87 (t, 3H); 13C
NMR (100 MHz, CDCl3): δ 203.1, 44.1, 32.1, 29.8, 29.7, 29.6, 29.5,
29.3, 22.9, 22.3, 14.3; GCMS (EI): m/z 240.
Benzyl (S)-(1-oxo-3-Phenylpropan-2-yl)carbamate (3o).32 Using
Procedure A afforded 0.25 g (89% yield) of the desired product as an
off-white solid. [α]23D = −52 (c 1, MeOH) (Lit.:15 [α]20D = −51.3 (c
1, MeOH)); 1H NMR (400 MHz, CDCl3): δ 9.67 (s, 1H), 7.81−7.25
(m, 9H), 7.17 (d, J = 8 Hz, 2H), 5.33 (s, 1H), 5.14 (s, 2H), 4.55 (q, J
= 6.7 Hz, 1H), 3.17 (d, J = 6.6 Hz, 2H); 13C NMR (100 MHz,
CDCl3): δ 199, 156.0, 136.2, 135.5, 129.4, 129, 128.7, 128.4, 128.3,
127.3, 67.3, 61.2, 35.5; MS (APCI) [M−H]+: m/z 282.2832.
Acetophenone (5a).33 Using Procedure A afforded 0.11 g (94%
yield) of the desired product as a colorless liquid. 1H NMR (400 MHz,
CDCl3): δ 7.97−7.95 (m, 2H), 7.59−7.54 (m, 1H), 7.48−7.44 (m,
2H), 2.61 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 198.3, 137.2,
133.2, 128.7, 128.4, 26.8; GCMS (EI): m/z 120.
1
1437, 1325, 1270, 1107, 1048; H NMR (400 MHz, DMSO-d6): δ
8.47 (d, J = 8.0 Hz, 2H), 6.97 (d, J = 8.0 Hz, 2H), 3.39 (s, 3H), 3.23
(s, 6H); 13C NMR (100 MHz, DMSO-d6): δ 158.4, 156.6, 139.0,
138.4, 107, 106.3, 51.9, 40.2, 40.1, 39.9, 39.7, 39.5, 39.3, 39.1, 38.9;
HRMS (ESI): m/z calcd for C9H14N3O4S [M+H]+, 260.0700; found,
260.0704.
(Methoxycarbonyl)(pyridin-1-ium-1-ylsulfonyl)amide (6b). To a
solution of chlorosulfonylisocyanate (1 g, 7.06 mmol) in benzene (6
mL) at 0 °C was added a solution of methanol (0.28 mL, 7.06 mmol)
in benzene (4 mL) over the course of 30 min. Once the addition was
complete, residual solvent was removed under reduced pressure to
give the desired sulfamoyl chloride intermediate as a white solid (1.15
g). A solution of the newly formed sulfamoyl chloride (1.15 g, 6.64
mmol) in benzene (8 mL) was added dropwise to a solution of
pyridine (1 mL, 13.2 mmol) in benzene (10 mL) at 25 °C. After the
addition was complete (∼1 h), 20 mL of H2O was added and the
resulting mixture was extracted twice with EtOAc (30 mL). The
organic layer was separated, washed with brine and the solvent was
removed under reduced pressure to afford 0.93 g (65%) of 6b as a
white solid. m.p.: 109−111 °C; IR (ATR): νco 3077, 1729, 1607, 1532,
1211, 1043; 1H NMR (400 MHz, CDCl3): δ 9.33 (d, J = 5.5 Hz, 2H),
8.41 (t, J = 7.7 Hz, 1H), 7.95 (t, J = 6.9 Hz, 2H), 3.59 (s, 3H); 13C
NMR (100 MHz, CDCl3): δ 159.1, 145.5, 141.5, 126.7, 53.2; HRMS
(ESI): m/z calcd for C7H9N2O4S [M+H]+, 217.0278; found,
217.0278.
1-(4-Methoxyphenyl)ethan-1-one (5b).34 Using Procedure A
afforded 0.14 g (92% yield) of the desired product as a colorless
liquid. 1H NMR (400 MHz, CDCl3): δ 7.93 (d, J = 8.9 Hz, 2H), 6.92
(d, J = 8.8 Hz, 2H), 3.86 (s, 3H), 2.55 (s, 3H); 13C NMR (100 MHz,
CDCl3): δ 196.9, 163.6, 130.7, 130.5, 113.8, 55.6, 26.5; GCMS (EI):
m/z 150.
1-(4-Bromophenyl)ethan-1-one (5c).33 Using Procedure A af-
forded 0.18 g (93% yield) of the desired product as an off-white solid.
1H NMR (400 MHz, CDCl3): δ 7.82 (d, J = 8.5 Hz, 2H), 7.61 (d, J =
8.6 Hz, 2H), 2.58 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 197.1,
136.0, 132.0, 130.0, 128.4, 26.7; GCMS (EI): m/z 198.
Benzophenone (5d).27 Using Procedure A afforded 0.17 g (93%
yield) of the desired product as a colorless solid. 1H NMR (400 MHz,
CDCl3): δ 7.83−7.80 (m, 4H), 7.61−7.57 (m, 2H), 7.51−7.46 (m,
4H); 13C NMR (100 MHz, CDCl3): δ 196.8, 137.7, 132.5, 130.2,
128.4; MS (ESI) [M+H]+: m/z 183.
(Methoxycarbonyl)((1-methyl-1H-imidazol-3-ium-3-yl)sulfonyl)-
amide (6c). To a solution of methanol (0.28 mL, 7.06 mmol) in
CH2Cl2 (10 mL) at 0 °C was added chlorosulfonylisocyanate (1 g,
7.06 mmol) dropwise (∼10 min). Once the addition was complete, 1-
methylimidazole (1.6 g, 14.12 mmol) was added. After stirring the
resulting mixture at ambient temperature for 2 h, it was diluted with
H2O. The organic layer was isolated and the aqueous layer was washed
twice with CH2Cl2 (30 mL). The combined organic layers were
washed with brine, dried over anhydrous Na2SO4, and concentrated
under reduced pressure to afford 1.44 g (93%) of 6a as an off-white
solid. m.p = 142−144 °C; IR (ATR): νco 3133, 1651, 1439, 1314,
2,2-Dimethyl-1-phenylpropan-1-one (5e).21 Using Procedure A
afforded 0.15 g (93% yield) of the desired product as a colorless oil. 1H
NMR (400 MHz, CDCl3): δ 7.69 (d, J = 6.9 Hz, 2H), 7.56−7.35 (m,
3H), 1.35 (s, 9H); 13C NMR (100 MHz, CDCl3): δ 209.4, 138.8,
130.9, 128.2, 128, 44.4, 28.2. GCMS (EI): m/z 162.
Adamantan-2-one (5f).21 Using Procedure A afforded 0.13 g (89%
yield) of the desired product as a colorless solid. 1H NMR (400 MHz,
CDCl3): δ 2.53 (s, 2H), 2.09−1.92 (m, 12H); 13C NMR (100 MHz,
CDCl3): δ 218.6, 47.1, 39.4, 36.4, 27.6; GCMS (EI): m/z 150.
(S)-2-Phenylcyclohexan-1-one (5g).31 Using Procedure A afforded
1
1297, 1105, 1086; H NMR (400 MHz, acetone-d6): δ 9.05 (s, 1H),
7.72 (t, J = 1.8 Hz, 1H), 7.59 (t, J = 1.8 Hz, 1H), 4.12 (s, 3H), 3.46 (s,
3H); 13C NMR (100 MHz, acetone): δ 206.1, 159.9, 137.6, 123.6,
121.7, 52.3, 36.6; HRMS (ESI): m/z calcd for C6H10N3O4S [M+H]+,
220.0387; found, 220.0396.
0.16 g (82% yield) of the desired product as an off-white solid. [α]24
D
= −106 (c 0.34, CHCl3) (Lit.:31 [α]25D = −103.4 (c 0.32, CHCl3); 1H
NMR (400 MHz, CDCl3): δ 7.39−7.30 (m, 2H), 7.30−7.22 (m, 1H),
E
DOI: 10.1021/acs.joc.6b02629
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
Methyl (E,4S)-4-((tert-Butoxycarbonyl)amino)-6-methylhept-2-
Chem. Soc. 1972, 94, 6135. (d) Burgess, E. M.; Penton, H. R.; Taylor,
E. A. J. Org. Chem. 1973, 38, 26. (e) Burgess, E. M.; Penton, H. R., Jr.;
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(g) Wipf, P.; Miller, C. P.; Venkatraman, S.; Fritch, P. C. Tetrahedron
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Hudlicky, T. J. Org. Chem. 2010, 75, 3447. (c) Sullivan, B.; Gilmet, J.;
Leisch, H.; Hudlicky, T. J. Nat. Prod. 2008, 71, 346.
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(b) Dolle, R. E.; Nicolaou, K. C. J. Am. Chem. Soc. 1985, 107, 1691.
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1992, 57, 7133. (d) Holton, R. A.; Kim, H. B.; Somoza, C.; Liang, F.;
Biediger, R. J.; Boatman, P. D.; Shindo, M.; Smith, C. C.; Kim, S. J.
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Longbottom, D. A. J. Am. Chem. Soc. 2004, 126, 6234. (b) Nicolaou,
K. C.; Huang, X.; Snyder, S. A.; Rao, P. B.; Bella, M.; Reddy, M. V.
Angew. Chem., Int. Ed. 2002, 41, 834. (c) Nicolaou, K. C.; Longbottom,
D. A.; Snyder, S. A.; Nalbanadian, A. Z.; Huang, X. Angew. Chem., Int.
Ed. 2002, 41, 3866.
enoate (7a).17 Using Procedure D afforded 0.2 g (78% yield) of the
desired product as a colorless oil. [α]23 = −18 (c 1, CHCl3) (Lit.:17
D
[α]25D = −17 (c 1, CHCl3); 1H NMR (400 MHz, CDCl3): δ 6.86 (dd,
J = 15.6, 5.5 Hz, 1H), 5.94 (dd, J = 15.7, 1.5 Hz, 1H), 4.68−4.23 (m,
2H), 3.75 (s, 3H), 1.71 (dt, J = 13.4, 6.7 Hz, 1H), 1.46 (s, 9H), 1.40 (t,
J = 7.3 Hz, 2H), 0.95 (d, J = 6.6 Hz, 6H); 13C NMR (100 MHz,
CDCl3) δ 167, 155.2, 149.4, 120.1, 79.9, 51.8, 48, 43.9, 28.5, 24.9, 22.8,
22.3; HRMS (ESI): m/z calcd for C14H25NO4Na [M+Na]+, 294.1676;
found, 294.1711.
Methyl (E,4S)-4-(((Benzyloxy)carbonyl)amino)pent-2-enoate
(7b). Using Procedure D afforded 0.22 g (83% yield) of the desired
product as an off-white solid. m.p.: 45−47 °C; [α]23 = −18 (c 1,
D
CHCl3); IR (ATR): νco 3277, 2952, 1709, 1690, 1540; 1H NMR (400
MHz, CDCl3): δ 7.60−7.29 (m, 5H), 6.88 (dd, J = 15.7, 5.1 Hz, 1H),
6.08−5.79 (m, 1H), 5.35−4.99 (m, 2H), 4.77 (d, J = 8.2 Hz, 1H),
4.65−4.40 (m, 1H), 3.73 (s, 3H), 1.29 (d, J = 7.0 Hz, 3H); 13C NMR
(100 MHz, CDCl3) δ 166.8, 155.5, 149.1, 136.3, 128.7, 128.4, 128.3,
120.2, 67.1, 51.8, 47.7, 20.4; HRMS (ESI): m/z calcd for
C14H17NO4Na [M+Na]+, 286.1050; found, 286.1079.
Methyl (E,4S)-4-(((Benzyloxy)carbonyl)amino)-5-phenylpent-2-
enoate (7c). Using the Procedure D afforded 0.28 g (82% yield) of
the desired product as an off-white solid. m.p.: 75−77 °C; [α]23D = −4
(c 1, CHCl3); IR (ATR): νco 3320, 2923, 1715, 1690, 1532; 1H NMR
(400 MHz, CDCl3): δ 7.47−7.23 (m, 8H), 7.22−7.14 (m, 2H), 6.95
(dd, J = 15.7, 5.1 Hz, 1H), 5.89 (dd, J = 15.7, 1.6 Hz, 1H), 5.09 (d, J =
2.1 Hz, 2H), 4.88−4.57 (m, 2H), 3.75 (s, 3H), 2.95 (d, J = 6.1 Hz,
2H); 13C NMR (100 MHz, CDCl3): δ 166.6, 155.6, 147.4, 136.3,
136.1, 129.5, 128.8, 128.7, 128.4, 128.3, 127.2, 121.1, 77.5, 77.2, 76.8,
67.1, 52.9, 51.8, 40.7; HRMS (ESI): m/z calcd for C20H21NO4Na [M
+Na]+, 362.1363; found, 362.1374.
Kinetics Data. An oven-dried NMR tube was charged with the
Burgess reagent (0.028 mmol) followed by a solution of an alcohol
(0.0212 mmol) and 1,3,5-trimethoxybenzene (0.0212 mmol) (as an
internal standard) in DMSO-d6 (0.6 mL). Conversions of the alcohols
to their respective oxidized products were independently monitored
1
over time using H NMR spectroscopy.
Competition Experiments. An oven-dried NMR tube was
charged with various alcohols (0.1 mmol each) and DMSO-d6 (0.6
mL). The Burgess reagent (0.13 mmol) was added to the NMR tube
and the conversions of the alcohols to their respective oxidized
products were independently monitored using 1H NMR spectroscopy.
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.joc.6b02629.
■
S
(10) (a) Burckhardt, S. Synlett 2000, 2000, 559. (b) Lamberth, C. J. J.
Prakt. Chem. 2000, 342, 518.
(11) Parikh, J. R.; Doering, W. v. E. J. Am. Chem. Soc. 1967, 89, 5505.
(12) (a) Mancuso, A. J.; Huang, S.-L.; Swern, D. J. Org. Chem. 1978,
43, 2480. (b) Omura, K.; Swern, D. Tetrahedron 1978, 34, 1651.
(13) The Burgess reagent has been reported to oxidize benzoin
derivatives in yields of up to 67% in dry CH2Cl2; see: Jose, B.; Unni,
M. V. V.; Prathapan, S.; Vadakkan, J. J. Synth. Commun. 2002, 32,
2495. Rappai, J. P.; Karthikeyan, J.; Prathapan, S.; Unnikrishnan, P. A.
Synth. Commun. 2011, 41, 2601. In our hands, the oxidation of benzyl
alcohol to benzaldehyde was not observed when subjected to similar
conditions.
Kinetics data and NMR spectra (PDF)
AUTHOR INFORMATION
Corresponding Author
*E-mail: bielawski@unist.ac.kr.
■
ORCID
Christopher W. Bielawski: 0000-0002-0520-1982
Notes
The authors declare no competing financial interest.
(14) The Burgess reagent is commercially available but can be
conveniently prepared on the multigram scale from chlorosulfonyl
chloride, CH3OH and Et3N; see ref 1d.
ACKNOWLEDGMENTS
(15) The [α]23 of 3o was measured to be −52 (c 1, MeOH) and
D
■
was in agreement with the literature value ([α]20 = −51.3, c 1,
D
We are grateful to the IBS (IBS-R019-D1) and the BK21 Plus
Program as funded by the Ministry of education and the
National Research Foundation of Korea for financial support
MeOH); see: De Luca, L.; Giacomelli, G.; Porcheddu, A. Org. Lett.
2001, 3, 3041.
(16) Subjecting tert-butanol to the reaction conditions resulted in the
formation of an unidentified product; the formation of olefins or
thioacetals were not observed by NMR spectroscopy.
REFERENCES
■
(17) The [α]23D of 7a was measured to be −18 (c 1, CHCl3) and was
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