The reaction of cyclopropanols with Burgess reagent: A reinvestigation and correction

Article abstract of DOI:10.1080/10426507.2010.531334

Chemical Equation Presented The reaction of cyclopropanols with Burgess reagent yields the unusual sulfamates 8 and their N-methylated derivatives 9. Unlike a previous study, dicyclopropyl ether formation was not observed. Also, the mechanism of ether formation from a cyclopropanol precursor cannot follow an SN2 pathway with retention. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/10426507.2010.531334

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Phosphorus, Sulfur, and Silicon and the
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The Reaction of Cyclopropanols with
Burgess Reagent: A Reinvestigation and
Correction
Klaus Banert a , Monika Ries b & Ernst Schaumann b
a Technische Universität Chemnitz , Chemnitz, Germany
b Technische Universität Clausthal , Clausthal-Zellerfeld, Germany
Published online: 19 Feb 2011.
To cite this article: Klaus Banert , Monika Ries & Ernst Schaumann (2011) The Reaction of
Cyclopropanols with Burgess Reagent: A Reinvestigation and Correction, Phosphorus, Sulfur, and
Silicon and the Related Elements, 186:2, 205-212, DOI: 10.1080/10426507.2010.531334
To link to this article: http://dx.doi.org/10.1080/10426507.2010.531334
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Phosphorus, Sulfur, and Silicon, 186:205–212, 2011
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2010.531334
COMMUNICATION
THE REACTION OF CYCLOPROPANOLS WITH BURGESS
REAGENT: A REINVESTIGATION AND CORRECTION
Klaus Banert,1 Monika Ries,2 and Ernst Schaumann2
1Technische Universita¨t Chemnitz, Chemnitz, Germany
2Technische Universita¨t Clausthal, Clausthal-Zellerfeld, Germany
GRAPHICAL ABSTRACT
O
R
R
O
O
SO2
SO2
NH COOMe
MeO
N
SO2NEt3
27-74 %
R
OH
Me
N
+
COOMe
5-8 %
Abstract The reaction of cyclopropanols with Burgess reagent yields the unusual sulfamates
8 and their N-methylated derivatives 9. Unlike a previous study, dicyclopropyl ether formation
was not observed. Also, the mechanism of ether formation from a cyclopropanol precursor
cannot follow an SN2 pathway with retention.
Keywords Alcohols; reaction mechanisms; small ring systems; sulfonamides
INTRODUCTION
Methyl N-(triethylammoniumsulfonyl)carbamate (2, or, Burgess reagent) opens up
a convenient route for the dehydration of secondary or tertiary alcohols to give alkenes,
while primary alcohols yield carbamates, but also a variety of other applications have been
reported.1–5 So, when the Clausthal group was looking for a way to achieve dehydration of
cyclopropanol 1 with a spiro-attached thioacetal unit, the Burgess reagent was an obvious
choice.6 However, the only product that could be isolated from the complex reaction mixture
was not a cyclopropene, but based mainly on the NMR and MS data was assigned ether
structure 3. Moreover, starting from optically active spiro-alcohol (R)-1, a product with
two sets of 13C NMR signals was isolated and assigned the (R,R)-configuration (Scheme
1). This seemed to indicate an SN process with retention of configuration, as had been
previously discussed in cyclopropane substitution chemistry.7–9 Both the unusual reaction
product and the reaction mechanism called for this, more detailed study of the reaction
Received 21 September 2010; accepted 8 October 2010.
Address correspondence to Ernst Schaumann, Institut fu¨r Organische Chemie, Leibnizstraße 6, TU Clausthal,
38678 Clausthal-Zellerfeld, Germany. E-mail: ernst.schaumann@tu-clausthal.de
205

206
K. BANERT ET AL.
O
S
S
S
S
S
S
S
S
S
S
MeO
OH
N
SO2NEt3
(2)
MeCN, reflux
O
1
(R,R)-3
O
(R,S)-3
Scheme 1 Reported reaction of cyclopropanols 1 and with Burgess reagent.
of cyclopropanols with Burgess reagent 2. Here it turned out that the interpretation of the
original data cannot be sustained.
RESULTS AND DISCUSSION
Among the various methods of cyclopropanol synthesis,10,11 we found the modified
Simmons–Smith methylenation of silyl enol ethers with diiodomethane/diethylzinc to be
most convenient.12 Thus, aldehydes 4 are silylated using a conventional protocol13 to give
enol ethers 5a–c as mixtures of the geometrical isomers (E/Z in comparable amounts).
Ethers 5 are then subjected to the joint action of diiodomethane and diethylzinc.12 The
resulting cyclopropyl silyl ethers 6a,b are generated as cis/trans mixtures, while for 6c,
the presence of an additional stereogenic center gives rise to a complex mixture of four
diastereomers. The silyl residue of 6 can easily be removed by methanolic potassium
carbonate14 to give the desired cyclopropanols 7 (Scheme 2).
R
OSiMe
3
Me SiCl, NEt
3
3
CH I , ZnEt ,E t O
2 2
2
2
R
OSiMe
3
DMF, r.t.
80°C
0°C
r.t.
RCH CHO
2
C
58 - 73 %
44 % for ( 6c )
H
H
4a -c
5a-c
6a-c
R
OH
R
O
O
SO
NH
COOMe
2
K CO , MeOH
2, MeCN, r ef lux
2
3
60 - 90 %
7a -c
8a-c (27-74 %)
M e
4a- 9c : R = Pr
b : R = Bn
R
+
SO
N
2
COOM e
c : R = PhCH(M e)
9a -c (5-8 %)
Scheme 2 Synthesis of cyclopropanols 7 and their reaction with Burgess reagent.

REACTION OF CYCLOPROPANOLS WITH BURGESS REAGENT
207
Burgess reagent 2 was applied as previously6 to the diastereomeric mixtures
of cyclopropanols 7 (Scheme 2). Column chromatography allowed to isolate N-
(cyclopropyloxysulfonyl)carbamates (N-(methoxycarbonyl)sulfamates)
8
as main
products and the N-methylated derivatives 9 as major side products. Structure assignment
for 8 and 9 is based on the spectroscopic data including HRMS. It appears that a product
of type 8 has only rarely been observed in the chemistry of the Burgess reagent, especially
when a sterically very hindered hydroxy group was reacted with 2,14–16 whereas diols
readily give cyclic sulfamates with 2.17 Obviously, the reaction between alcohols 7 and the
reagent 2 is initiated by the usual SN attack of the alcoholic hydroxy group at the sulfur
of reagent 2 to give sulfamide 10 (Scheme 3). From here, attack of the amide nitrogen
on H-2 of the ring to give a cyclopropene, the “normal” Burgess product, is obviously
disfavored because of the inherent buildup of ring strain. The alternative, an intramolecular
SN attack on C-1 of the ring to give carbamate 12,1–5 is probably suppressed because this
would involve a backside attack, which has been seen in cyclopropanes only under specific
circumstances.8,18 In this situation, stabilization of intermediate 1019 to product 8 occurs.
A competing pathway is methylation of 10 by another molecule of 10 or by the already
formed product 8, though the expected parallel product 11 could not be detected. Prolonged
heating does not allow forcing of the formation of cyclopropenes or of carbamates 12.
Rather, formation of methylation product 9 seems to be further encouraged.
8
- NEt3
+ 8
2
7
9
+
R
O
SO2
N
COOMe
-
(11)
SO2NH2
R
O
HNEt3
10
- CO2
- SO3
R
NH COOMe
12
Scheme 3 Suggested mechanism for formation of products 8 and 9.
Even careful chromatography of the product mixture as formed from 2 and 7 did not
reveal the formation of dicyclopropyl ethers analogous to 3. Moreover, other than with 7, the
reaction of cyclopropanol 1 with Burgess reagent 2 had produced a very complex mixture
of, except for 3, unidentified products. This raises the suspicion that the spiro-attached
thioacetal unit in 1 interacts with the Burgess reagent. In fact, a model reaction of thioacetal
13 with Burgess reagent 2 under the same reaction conditions as used earlier6 showed
that only 47% of 13 survived this treatment. In the complex product mixture, the main
component was dithiepin 14, while only traces of acetophenone were detected. Normally,
the transition from a dithiane to a dithiepin of type 14 requires an exocyclic leaving group
in the 2-position of the dithiane20 or generation of an exocyclic carbene.21

208
K. BANERT ET AL.
S
S
Ph
S
S
Ph
13
14
Me
While the origin of ether 3 remains mysterious, the claimed formation from 1 by an
SN2 pathway with retention has to be revised in any case. Product 3 with (R,R) configuration
would give only one set of NMR signals because of its C2 axis of symmetry. However,
the isolated product showed two sets of NMR signals with comparable intensity, indicating
that the (R,S)-form of 3 is equally present. This speaks against any SN2 route with a
single stereochemical outcome. A possible explanation would be the nonstereoselective
addition of alcohol (R)-1 to a cyclopropene intermediate in an EA mechanism.22 However,
as the model reactions of cyclopropanols 7 with reagent 2 give no clue as to cyclopropene
formation, this route to 3 remains speculative.
EXPERIMENTAL
1
Melting points are uncorrected. H NMR and 13C NMR spectra were recorded on
Bruker Avance DPX 200 and Avance 400 instruments in CDCl3 as solvent. Chemical shifts
were measured in δ (ppm) and coupling constants J in Hz. TMS (δ = 0.00) or the signal
1
of the solvent (CDCl3: δ = 7.26 ppm) served as internal standard in H NMR spectra.
The solvent peak (CDCl3 at δ = 77.0 ppm) was used as reference for 13C spectra. For
assignment of the number of substituents attached to the specified carbon, each carbon
is described as + (primary or tertiary carbon), − (secondary carbon), or 0 (quaternary
carbon), as determined by the DEPT-135 method. MS were recorded on a Varian instrument
Saturn 2100T or Hewlett-Packard 5989B; high-resolution MS (HRMS) measurements were
carried out at the “Institut fu¨r Organische Chemie, Leibniz Universita¨t Hannover.” LR-
ESIMS spectra were recorded on a Hewlett Packard/Agilent instrument LC-MSD Serie
1100 at a dry gas temperature of 300◦C, a capillary voltage of 3000 V, and a fragmentor
voltage of 0 V. Samples were dissolved in HPLC grade methanol and sprayed directly
from methanol. IR spectra were recorded on a Bruker Vektor 22 FT-IR spectrometer. TLC
was performed on Merck 60 F254 precoated silica plates, and spots were detected by UV
fluorescence quenching or by spraying with a solution of anisaldehyde/sulfuric acid in
methanol and subsequent heating. Flash chromatography was performed with silica gel
60 (Merck, 230–400 mesh). Ethyl acetate (EA) and petroleum ether (PE) with the boiling
range 60–70◦C were used in the separations. All solvents were distilled before use. Silyl
ethers 5a (63%),12 b (75%),23 and c (58%)24 were obtained as E/Z mixtures by a general
procedure13 and gave spectroscopic data in accordance with the literature.
Cyclopropanation of Alkenyl Silyl Ethers 5 to Cyclopropyl Silyl Ethers 6
A literature method12 gave, after aqueous work-up, crude silyl ethers 6a,b, which
were desilylated in situ to cyclopropanols 7a,b (vide infra) by the action of K2CO3 in
MeOH.14 The desilylation step was not applied to the product from 5c.

REACTION OF CYCLOPROPANOLS WITH BURGESS REAGENT
209
2-(1-Phenylethyl)cyclopropyl Trimethylsilyl Ether (6c)
6c was prepared from 5c (5.5 g. 24.96 mmol) to give 2.59 g (44%) as a colorless
oil. The compound is a mixture of four diastereomers. The cis/trans-forms could at least
partially be separated by repeated column chromatography (PE/EA 1:50–> 1:100).
trans-6c (isolated major diastereomer): 1H NMR (200 MHz): δ = 7.45–7.21 (m, 5H,
Ph), 3.21 (dt, J = 6.6, 2.8, 1 H, H-1), 2.07 (dq, J = 9.6, 7.1, 1H, PhCH), 1.35 (d, J = 7.1,
3H, Me), 1.32–1.11 (m, 1H, H-2), 0.85 (ddd, J = 9.7, 5.8, 2.8, 1H, H-3a), 0.53 (ddd, J =
6.6, 6.3, 5.8, 1H, H-3b), -0.00 (s, 9H, SiMe3). 13C NMR (50 MHz) δ = 146.4 (o, C-Ar),
128.4, 127.1, 126.1 (+, CH-Ar), 52.0 (+, C-1), 42.4 (+, CMe), 27.7 (+, C-2), 20.2 (+,
CMe), 13.6 (−, C-3), −0.5 (+, SiMe3).
trans-6c (isolated minor diastereomer): 1H NMR (200 MHz): δ = 7.45–7.21 (m, 5H,
Ph), 3.27 (dt, J = 6.4, 2.8, 1 H, H-1), 2.12 (dq, J = 9.9, 7.0, 1H, PhCH), 1.47 (d, J = 7.0,
3 H, Me), 1.32–1.10 (m, 1H, H-2), 0.73 (ddd, J = 9.7, 5.9, 2.8, 1H, H-3a), 0.43 (ddd, J =
6.4, 6.1, 5.9, 1H, H-3b), 0.25 (s, 9H, SiMe3). 13C NMR (50 MHz,) δ = 146.1 (o, C-Ar),
128.3, 127.0, 126.0 (+, CH-Ar), 53.0 (+, C-1), 42.4 (+, CMe), 26.9 (+, C-2), 21.9 (+,
CMe), 13.6 (−, C-3), −0.1 (+, SiMe3).
1
cis-6c (isolated major diastereomer): H NMR (200 MHz): δ = 7.36–7.07 (m, 5H,
Ph), 3.48 (dt, J = 6.3, 3.4, 1 H, H-1), 2.53 (dq, J = 10.2, 7.0, 1 H, PhCH), 1.31 (d, J = 7.0,
3 H, Me), 0.94–0.72 (m, 1H, H-2), 0.69 (dt, J = 9.4, 6.3, 1 H, H-3a), 0.54 (dt, J = 9.4, 6.3,
1H, H-3b), 0.14 (s, 9H, SiMe3). 13C NMR (50 MHz,) δ = 148.0 (o, C-Ar), 128.2, 127.2,
125.7 (+, CH-Ar), 50.8 (+, C-1), 37.7 (+, CMe), 23.6 (+, C-2), 22.5 (+, CMe), 12.8 (−,
C-3), −0.0 (+, SiMe3).
cis-6c (isolated minor diastereomer): 1H NMR (200 MHz): δ = 7. 36–7.07 (m, 5H,
Ph), 3.36 (dt, J = 6.6, 3.4, 1 H, H-1), 2.63 (dq, J = 7.0, 3.9, 1H, PhCH), 1.35 (d, J = 7.0,
3 H, Me), 0.94–0.72 (m, 1H, H-2), 0.25 (mc, 1 H, H-3a), 0.18–0.08 (m, overlapping, 1 H,
H-3b), 0.00 (s, 9H, SiMe3). 13C NMR (50 MHz,) δ = 147.7 (o, C-Ar), 128.1, 127.2, 125.6
(+, CH-Ar), 50.7 (+, C-1), 37.0 (+, CMe), 24.5 (+, C-2), 21.8 (+, CMe), 12.6 (−, C-3),
−0.3 (+, SiMe3).
Cyclopropanols 7
Alcohols 7a,b were obtained by in-situ desilylation.14 The same procedure allowed
conversion of 6c into 7c.
2-Propylcyclopropanol (7a). Yield 2.49 g (68%) over two steps from 5a (5.76 g,
36.4 mmol) as a colorless oil. The spectroscopic data match the literature.25
2-Benzylcyclopropanol (7b). Yield 2.19 g (90%) over two steps from 5b (3.39
g, 16.4 mmol) as a colorless oil: cis/trans mixture. The spectroscopic data for cis-7b match
the literature.26 Data for the trans compound: 1H NMR (200 MHz): δ = 7.35–7.15 (m, 5H,
Ph), 3.35 (dt, J = 6.0, 2.7, 1H, H-1), 2.53 (m, 2H, PhCH), 1.9 (broad s, 1H, OH), 1.39–1.15
(m, 1H, H-2), 0.80 (ddd, J = 9.7, 6.0, 2.7, 1H, H-3a), 0.50 (“q”, J = 6.0, 1H, H-3b). 13C
NMR (50 MHz,) δ = 141.0 (o, C-Ar), 128.4, 128.3, 126.0 (+, CH-Ar), 52.6 (+, C-1), 37.3
(+, CPh), 21.5 (+, C-2), 14.6 (−, C-3). IR (NaCl): ν˜ = 3421, 3062, 3028, 2926, 1716.
2-(1-Phenylethyl)cyclopropanol (7c). Yield 463 mg (60%) from cis-6c (1.12
g, 4.79 mmol) as a colorless oil; diastereomeric mixture, the two cis-isomers could be
obtained in relatively pure form by repeated column chromatography (PE/EA 8:1). Major
cis-isomer: 1H NMR (200 MHz): δ = 7.38–7.12 (m, 5H, Ph), 3.67 (ddd, J = 6.5, 6.3, 3.3,
1H, H-1), 2.64 (dq, J = 10.3, 7.0, 1H, PhCH), 1.96 (broad s, 1H, OH), 1.38 (d, J = 7.0,

210
K. BANERT ET AL.
3 H, Me), 0.93 (dddd, J = 10.3, 9.3, 6.5, 6.3, 1H, H-2), 0.67 (dt, J = 9.3, 6.3, 1H, H-3a),
0.28 (dt, J = 6.3, 3.3, 1H, H-3b). 13C NMR (50 MHz,) δ = 147.4 (o, C-Ar), 128.3, 127.1,
125.9 (+, CH-Ar), 50.7 (+, C-1), 37.5 (+, CMe), 20.1 (+, C-2), 22.9 (+, CMe), 13.1 (−,
C-3).
Minor cis-isomer: 1H NMR (200 MHz): δ = 7.37–7.12 (m, 5H, Ph), 3.53 (ddd, J =
6.4, 6.1, 3.2, 1H, H-1), 2.64 (dq, J = 10.2, 7.1, 1H, PhCH), 1.65 (broad s, 1H, OH), 1.41
(d, J = 7.1 H, Me), 0.99 (dddd, J = 10.2, 9.2, 6.2, 6.1, 1H, H-2), 0.83 (ddd, J = 9.2, 6.4,
5.7, 1H, H-3a), 0.41 (ddd, J = 6.2, 5.7, 3.2, 1H, H-3b). 13C NMR (50 MHz,) δ = 147.5 (o,
C-Ar), 128.5, 126.7, 126.0 (+, CH-Ar), 50.4 (+, C-1), 38.1 (+, CMe), 25.1 (+, C-2), 22.7
(+, CMe), 13.0 (−, C-3).
Typical Procedure for the Reaction of Cyclopropanols 7 with Burgess
Reagent 2: Formation of Sulfamates 8a, 9a
Cyclopropanol 7a (3.8 mmol) and reagent 2 (918 mg, 3.85 mmol) in MeCN (2 mL)
were heated to 80◦C over 15 min and kept boiling for 1 h. After cooling, water (5 mL) was
added to the reaction mixture and the organic products extracted by washing with ether (3 ×
10 mL) and CH2Cl2 (5 × 10 mL). The combined organic phases were washed with sat. brine
(1 × 10 mL) and dried (MgSO4). After filtration, the solvents were carefully evaporated
in vacuo. The residue was dissolved in MeOH (20 mL) and stirred with freshly activated
Dowex 50 × 8 (1.0 g) at rt. After removal of the ion exchange resin, the concentrated
filtrate was subjected to column chromatography (silica) using PE/EA (6:1 –> 1:1) and
then CH2Cl2/MeOH (10:1).
Methyl N-(2-propylcyclopropyloxysulfonyl)carbamate (8a). From 7a (381
1
mg, 3.81 mmol) to give 239 mg (27%). Colorless oil. Cis/trans mixture. H NMR (200
MHz): δ = 7.95 (broad s, 2H, NH), 4.32 (dt, J = 6.6, 3.0, 1H, H-1, cis), 4.00 (dt, J = 6.6, 2.6,
1H, H-1, trans), 3.85 (s, 6H, OMe), 1.64–0.80 (m, 18H, H-2, H-3a or H-3b, CH2CH2CH3),
0.72–0.53 (m, 2 H-3b or H-3a). 13C NMR (50 MHz): δ = 150.6 (o, cis- and trans-C = O),
61.9 and 60.9 (+, C-1), 54.1 and 54.0 (+, OMe), 32.8 and 29.2 (−, CH2C-1), 22.4 and 21.5
(−, CH2C-2), 18.1 and 16.3 (+, C-2), 13.8 and 13.7 (+, CMe), 11.7 and 11.0 (−, C-3). IR
(NaCl): ν˜ = 3261, 2962, 2957, 2932, 2874, 1758, 1467, 1428, 1381, 1245, 1174.
Methyl N-methyl-N-(2-propylcyclopropyloxysulfonyl)carbamate (9a).
Also from 7a (381 mg, 3.81 mmol) to give 72 mg (8%). Colorless oil. Cis/trans mixture.
1H NMR (200 MHz): δ = 4.23 (dt, J = 6.6, 3.0, 1H, H-1, cis), 3.91 (dt, J = 6.4, 2.4,
1H, H-1, trans), 3.87 (s, 6H, OMe), 3.36 (s, 6H, NMe), 1.60–0.84 (m, 18H, H-2, H-3a or
H-3b, CH2CH2CH3), 0.65–0.53 (m, 2H, H-3b or H-3a).13C NMR (50 MHz): δ = 152.8
and 152.7 (o, C = O), 61.3 and 60.1 (+, C-1), 54.6 and 54.5 (+, OMe), 35.8 and 35.7 (+,
NMe), 32.9 and 29.2 (−, CH2C-1), 22.4 and 21.5 (−, CH2Me), 18.1 and 16.3 (+, C-2),
13.8 and 13.7 (+, CMe), 11.6 and 10.8 (−, C-3). IR (NaCl): ν˜ = 3008, 2961, 2957, 2933,
2874, 1746, 1447, 1398, 1293, 1180.
Analogously were prepared:
Methyl N-(2-benzylcyclopropyloxysulfonyl)carbamate (8b). From 7b (523
mg, 3.53 mmol) to give 405 mg (42%). Colorless oil. Cis/trans mixture.1H NMR (400
MHz): δ = 7.35–7.19 (m, 10H, Ph), 4.41 (dt, J = 6.7, 3.2, 1H, H-1, cis), 4.09 (m, 1 H, H-1,
trans), 3.84 (s, 3H, OMe, cis), 3.79 (s, 3H, OMe, trans), 2.95 (dd, J = 15.0, 6.8, 1H, AB
system, PhCH, cis), 2.71 (dd, J = 15.0, 7.8, 1H, AB system, PhCH, cis), 2.64 (dd, J = 14.9,
7.2, 1H, AB system, PhCH, trans), 2.58 (dd, J = 14.9, 7.6, 1H, AB system, PhCH, trans),
1.66–1.54 (m, 1H, H-2, trans), 1.40–1.20 (m, 2H, H-2 cis, H-3a or H-3b trans), 1.07 (dt,
J = 9.5, 6.7, 1H, H-3a or H-3b, cis), 0.90 (dt, J = 7.3, 3.2, 1H, H-3b or H-3a, cis), 0.80

REACTION OF CYCLOPROPANOLS WITH BURGESS REAGENT
211
(“q”, J = 6.9, 1H, H-3b or H-3a, trans), δNH not found.13C NMR (50 MHz, cis): δ = 151.0
(o, C = O), 140.5 (o, C-Ar), 128.5, 128.3, 126.2 (+, CH-Ar), 60.4 (+, C-1), 54.1 (+, OMe),
33.0 (−, CH2Ph), 17.5 (+, C-2), 11.5 (−, C-3). 13C NMR (50 MHz, trans): δ = 150.7 (o,
C O), 139.4 (o, C-Ar), 128.6, 128.4, 126.6 (+, CH-Ar), 61.1 (+, C-1), 54.0 (+, OMe),
36.3 (−, CH2Ph), 19.4 (+, C-2), 11.7 (−, C-3). IR (NaCl): ν˜ = 3254, 3029, 2961, 1761,
1604, 1456, 1383, 1244, 1173, 897. HRMS (ESI): m/z calcd. for C12H15NO5S ([M—H]−)
284.0593, found 284.0595.
Methyl N-(2-benzylcyclopropyloxysulfonyl)-N-methylcarbamate (9b).
Also from 7b (523 mg, 3.53 mmol) to give 51 mg (5%). Colorless oil. Cis/trans mixture
1H (400 MHz): δ = 7.36–7.15 (m, 10H, Ph), 4.33 (dt, J = 6.6, 3.2, 1H, H-1, cis), 4.03 (dt,
J = 6.6, 2.6, 1H, H-1, trans), 3.88 (s, 3H, OMe, cis), 3.85 (s, 3H, OMe, trans), 3.38 (s,
3H, NMe, cis), 3.23 (s, 3H, NMe, trans), 2.92 (dd, J = 15.0, 7.0, 1H, AB system, PhCH,
cis), 2.72 (dd, J = 15.0, 7.6, 1H, AB system, PhCH, cis), 2.68 (dd, J = 14.8, 6.9, 1H,
PhCH, trans), 2.57 (dd, J = 14.8, 7.3, 1H, PhCH, trans), 1.68–0.72 (m, 6H, H-2, H-3a,b).
13C NMR (50 MHz, cis): δ = 152.8 (o, C O), 140.4 (o, C-Ar), 128.5, 128.3, 126.3 (+,
CH-Ar), 59.8 (+, C-1), 54.6 (+, OMe), 35.8 (+, NMe), 33.0 (−, CH2Ph), 17.5 (+, C-2),
11.3 (−, C-3). 13C NMR (50 MHz, trans): δ = 152.7 (o, C O), 139.1 (o, C-Ar), 128.6,
128.4, 126.5 (+, CH-Ar), 60.7 (+, C-1), 54.5 (+, OMe), 36.3 (−, CH2Ph), 35.6 (+, NMe),
18.9 (+, C-2), 11.7 (−, C-3). IR (NaCl): ν˜ = 3029, 2969, 1744, 1604, 1497, 1447, 1399,
1294, 1178. HRMS (ESI): m/z calcd. for C13H17NO5S ([M + Na]+) 322.0725, found
322.0721.
Methyl N-[2-(1-phenylethyl)cyclopropyloxysulfonyl]carbamate (8c).
From cis-7c (175 mg, 1.08 mmol) to give 240 mg (74%). Colorless oil. Mixture of two
diastereomers, one of which could be fully characterized. 1H NMR (200 MHz): δ = 7.60
(broad s, 1H, NH), 7.36–7.17 (m, 5H, Ph), 4.45 (dt, J = 6.6, 3.2, 1H, H-1), 3.85 (s, 3H,
OMe), 2.57 (dq, J = 10.5, 7.0, 1H, H-4), 1.40 (d, J = 7.0, 3H, CMe), 1.32–1.14 (m, 1H,
H-2), 0.94 (dt, J = 9.5, 6.7, 1H, H-3a), 0.78 (dt, J = 7.5, 3.2, 1H, H-3b). 13C NMR (50
MHz): δ = 151.0 (o, C O), 146.0 (o, C-Ar), 128.5, 126.9, 126.3 (+, CH-Ar), 60.9 (+,
C-1), 54.1 (+, OMe), 38.2 (−, CH2Ph), 23.1 and 22.2 (+, C-2 and CCH3), 11.3 (−, C-3).
HRMS (ESI): m/z calcd. for C12H15NO5S ([M-H]−) 298.0749, found 298.0750.
Methyl
N-methyl-
N-[2-(1-phenylethyl)cyclopropyloxysulfonyl]-N-
methylcarbamate (9c). Also from 7c (175 mg, 1.08 mmol) to give 12 mg (5%).
Colorless oil. Mixture of two diastereomers, one of which could be fully characterized. 1H
NMR (200 MHz): δ = 7.37–7.17 (m, 5H, Ph), 4.37 (dt, J = 6.4, 3.2, 1H, H-1), 3.91 (s,
3H, OMe), 3.39 (s, 3H, NMe), 2.55 (dq, J = 10.2, 6.9, 1H, PhCH), 1.40 (d, J = 6.9, 3H,
CMe), 1.33–1.11 (m, 1H, H-2), 0.90 (ddd, J = 9.6, 7.3, 6.4, 1H, H-3a), 0.70 (dt, J = 7.3,
3.2, 1H, H-3b). 13C NMR (50 MHz): δ = 152.8 (o, C O), 145.9 (o, C-Ar), 128.5, 126.9,
126.4 (+, CH-Ar), 60.3 (+, C-1), 54.6 (+, OMe), 35.8 (+, NMe), 38.3 (−, CH2Ph), 23.2
and 22.3 (+, C-2 and CCH3), 11.1 (−, C-3). HRMS (ESI): m/z calcd. for C12H15NO5S
([M + Na]+) 336.0882, found 336.083.
Reaction of Thioacetal 13 with Burgess Reagent 2
Thioacetal 13 (170 mg, 0.81 mmol) and 2 (192.5 mg, 0.81 mmol) were reacted
as reported above for the formation of 8a, 9a. Column chromatography (silica) gave
80 mg (47%) of 13 and 26 mg (16%) of 14.20 Acetophenone was detected in the H NMR
spectrum (δMe = 2.61 in CDCl3) and by addition of a weighed amount of authentic material
determined to be formed in 1.2% yield.

212
K. BANERT ET AL.
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