Aziridine-allylsilane-mediated synthesis of exocyclic γ-amino olefins and azabicyclo[x.y.1]-systems

Article abstract of DOI:10.1016/S0040-4020(02)00725-1

We have shown that connection of C-2 of an allylsilane to a tethered aziridine ring yields exocyclic γ-amino olefins and desilylated azabicyclo[x.2.1]-systems upon cyclization with BF₃·OEt₂. Furthermore, manipulation of a specific exocyclic γ-amino olefin provided access to an azabicyclo[3.3.1]nonane. This methodology should be useful for the preparation of natural products and pharmacologically active agents containing these bicyclic heterocyclic systems.

Full text of DOI:10.1016/S0040-4020(02)00725-1

Tetrahedron 58 (2002) 7109–7117
Aziridine–allylsilane-mediated synthesis of exocyclic g-amino
olefins and azabicyclo[x.y.1]-systems
*
David J. Lapinsky and Stephen C. Bergmeier
Department of Chemistry and Biochemistry, Ohio University, Athens, OH 45701, USA
Dedicated to the memory of Professor Henry Rapoport (1918–2002)
Received 15 April 2002; accepted 9 May 2002
Abstract—We have shown that connection of C-2 of an allylsilane to a tethered aziridine ring yields exocyclic g-amino olefins and
desilylated azabicyclo[x.2.1]-systems upon cyclization with BF3·OEt2. Furthermore, manipulation of a specific exocyclic g-amino olefin
provided access to an azabicyclo[3.3.1]nonane. This methodology should be useful for the preparation of natural products and
pharmacologically active agents containing these bicyclic heterocyclic systems. q 2002 Elsevier Science Ltd. All rights reserved.
General methodology for the synthesis of alkaloids and
other nitrogen containing heterocycles continues to be of
immense importance to the pharmaceutical sciences. In this
regard, we have discovered a method that could serve as a
general and useful procedure for the synthesis of these
molecules. We have reported the conversion of an
aziridine–allylsilane (1) to either the g-amino olefin1 (2),
the silylated azabicyle1c (3), or the desilylated azabicycle
(4). Molecules 2 and 3 have served as instrumental
intermediates toward our synthesis of the rauwolfia alkaloid
(2)-yohimbane1b (5) and bicyclic proline analogs1c (6)
(Scheme 1).
connection to C-2 of the allylsilane could also produce
synthetically useful products. Treatment of aziridine–
allylsilanes with this connectivity (e.g. 7) could potentially
lead to the isolation of exocyclic g-amino olefins (8),
silylated azabicyclo[x.2.1]-systems (9), or desilylated aza-
bicyclo[x.2.1]-systems (10) (Scheme 2).
These cyclization products could be useful in either total
or analog synthesis of complex natural products and
pharmacologically active agents containing 6-azabicyclo-
[3.2.1]octanes2 or 3-azabicyclo[3.3.1]nonanes.2d,3 For
example, Thomas et al. reported2d the synthesis of a 1,5-di-
substituted-6-azabicyclo[3.2.1]octane (11) in order to explore
the effect of ring E contraction on nicotinic acetylcholine
receptor antagonist activity of methyllycaconitine (MLA)
Although aziridine–allylsilane 1 represents an example of
C-3 of the allylsilane tethered to an aziridine ring, we felt
Scheme 1.
Keywords: aziridines; allylsilanes; bicyclic heterocyclic compounds; nitrogen heterocycles.
*
Corresponding author. Fax: þ1-740-593-0148; e-mail: bergmeis@ohio.edu
0040–4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(02)00725-1

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D. J. Lapinsky, S. C. Bergmeier / Tetrahedron 58 (2002) 7109–7117
Scheme 2.
(12). Appropriate manipulation of olefin 8b could lead to
the inherent azabicyclo[3.3.1]nonane (13) present within the
AE rings of MLA (12) (Fig. 1). With these thoughts in mind,
we chose to prepare and cyclize a series of aziridine–
allylsilanes possessing the C-2 connectivity (7a–c). Our
synthesis of these compounds was carried out via Suzuki
coupling of an appropriately substituted aziridine with an
allylsilane,4 or via nucleophilic attack of an aziridine with
an organometallic allylsilane reagent.1b,c,5
with 9-BBN and cross-coupled to bromoallylsilane 177 to
give the racemic aziridine–allylsilane 7b in 58% yield. The
racemic substrate was then treated with 110 mol% of
BF3·OEt2 at 2788C for 4 h, then warmed to 2258C for an
additional 15 h. We were pleased to find that these
cyclization conditions provided the racemic exocyclic
g-amino olefin 8b in 86% yield. This cyclization proceeded
as expected with attack of the allylsilane at the internal
carbon of the aziridine ring, thus yielding the six-membered
carbocycle. The desilylated azabicyclo[3.2.1]-system (10b,
racemic) was also isolated in low yield (6%) (Scheme 3).
We initially prepared a racemic aziridine–allylsilane (7b)
possessing the desired C-2 connectivity as a test substrate to
explore the cyclization reaction. Commercially available
allylglycine was treated with MeOH/HCl followed by
toluenesulfonyl chloride to provide the diprotected amino
acid 146 in 80% yield from allylglycine. The ester was then
reduced with LiBH4 followed by a Mitsunobu ring closure
to provide aziridine 16. The olefin of 16 was hydroborated
The results of the initial cyclization of racemic aziridine–
allylsilane 7b prompted us to examine a series of optically
pure aziridine–allylsilanes with C-2 connectivity ((R)-7a–c),
differing only in the length of tether between the reacting
moieties. Two of the aziridines ((R )-7b and (R)-7c) were
readily prepared using our Suzuki strategy.4 Serine derived
Figure 1.
Scheme 3.

D. J. Lapinsky, S. C. Bergmeier / Tetrahedron 58 (2002) 7109–7117
7111
Scheme 4.
aziridine 185 was treated with either vinylmagnesium
bromide or allylmagnesium chloride in the presence of
CuCN to yield the desired silyl ether homologs (19 and 20).
Removal of the silyl protecting group and Mitsunobu ring
closure provided olefinic aziridines 23 and 248 in excellent
overall yield. Standard cross-coupling conditions using
bromoallylsilane 17 provided optically pure aziridine–
allylsilanes (R )-7b and (R )-7c in 58% and 68% yield,
respectively (Scheme 4).
64% yield. Deprotection with n-Bu4NF followed by a
Mitsunobu reaction formed the aziridine ring to
yield aziridine–allylsilane (R )-7a in good overall yield
(Scheme 5).
With our requisite aziridine–allylsilanes in hand, we began
to explore cyclization conditions to selectively yield
exocyclic g-amino olefins. Treatment of aziridine–allyl-
silane (R )-7b with a stoichiometric amount of BF3·OEt2 at
2788C, followed by warming of the reaction to 2258C,
provided the exocyclic olefin (R )-8b in nearly quantitative
yield (97%). Aziridine–allylsilane (R)-7c was cyclized in a
similar manner, though additional BF3·OEt2 (200 mol%)
and higher temperatures (08C) were needed for cyclization
to the seven-membered ring to occur. Exocyclic olefin
(R )-8c was achieved in moderate yield (51%) after
purification. The other major product (ca. 35%) of the
reaction appears to be the product of protodesilylation of
(R )-7c and proved difficult to isolate cleanly (Scheme 6).
The remaining aziridine–allylsilane of interest to us ((R)-
7a) could not be accessed via the Suzuki cross-coupling
route.4 Therefore we turned our attention towards nucleo-
philic attack of aziridine 18 with an organometallic
allylsilane reagent.1b,c,5 The known allylselenide 25 was
subjected to Li–Se exchange9 then transmetallated in the
presence of CuCN10 to generate the higher order cyano-
cuprate 26. Reaction of aziridine 18 with the organometallic
allylsilane reagent provided the ring opened product 27 in
Scheme 5.
Scheme 6.

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D. J. Lapinsky, S. C. Bergmeier / Tetrahedron 58 (2002) 7109–7117
Scheme 7.
Aziridine–allylsilanes (R )-7b and (R )-7c were then
cyclized with greater than stoichiometric amounts of
BF3·OEt2 (300 mol%) and warmed to room temperature in
the hopes of forming azabicyclo[x.2.1]-systems. After
subjecting substrate (R)-7b to these conditions, we were
able to isolate the desilylated azabicyclo[3.2.1]octane
(1R,5S )-10b in good yield (77%), while a 1:1:1 mixture
of isomerized amino olefins was obtained in 15% yield.
Treatment of aziridine–allylsilane (R )-7c in a similar
manner gave a 1:1:1 mixture of isomerized amino olefins
as the major product (54% yield), while the desilylated
azabicyclo[4.2.1]nonane (1R,6S)-10c was achieved in only
31% yield. We hoped refluxing conditions could potentially
drive the mixture of amino olefins towards bicycle (1R,6S )-
10c formation, though minimal changes in yield were
observed (51 and 37% for yields of isomerized olefins and
(1R,6S )-10c, respectively) (Scheme 7). It remains unclear
as to how these desilylated azabicyclo[x.2.1]-systems are
being formed. Three possibilities exist: (1) desilylated
azabicyclo[x.2.1]-systems 10b,c could form via cyclization
of the aziridine–allylsilane to the silylated azabicycle (i.e.
9b,c) followed by protodesilylation, (2) cyclization of the
aziridine-olefin (i.e. protodesilylated (R )-7b,c), or (3)
cyclization of the g-amino olefin (exocyclic or isomerized
(R )-8b,c). We suggest that option (2) or (3) are the most
likely. We have determined that protodesilylated (R)-7b can
be cyclized to azabicyclo[3.2.1]octane (1R,5S )-10b (71%
yield) using 300 mol% of BF3·OEt2 at room temperature.
We have also determined that g-amino olefins (e.g. 2) can
be cyclized to their azabicyclic counterpart (e.g. 4) under
similar conditions.11
Cyclizations of aziridine–allylsilanes (R)-7b and (R )-7c
proceeded with attack of the allylsilane at the internal
carbon of the aziridine ring, which is consistent with
previously reported intramolecular cyclizations of aziri-
dine–allylsilanes.1 However, substrate (R)-7a provided an
alternative cyclization behavior. Treatment of this aziri-
dine–allylsilane with 200 mol% of BF3·OEt2 and warming
to 08C gave the six-membered ring 29 as the major product
(50% yield) (Scheme 8). Products resulting from attack of
the internal carbon of the aziridine (i.e. (R )-8a) were not
observed, only those resulting from attack of the terminal
position. Therefore, aziridine–allylsilane (R )-7a displays
comparable reactivity to that reported for allylsilane-
epoxides possessing identical tether length and C-2
connectivity.12 Additionally, protodesilylation of (R )-7a
was detected by 1H NMR though purification of this product
(ca. 37%) again proved troublesome.
In an effort to extend the synthesis of azabicyclo[x.y.1]-
systems, olefin (R )-8b was subjected to a hydroboration-
oxidation sequence to provide a mixture of cis and trans
amino alcohols (30). The mixture of alcohols was cyclized
under Mitsunobu conditions to provide the azabicyclo-
[3.3.1]nonane (13) resulting from closure of the cis amino
alcohol. When olefin (R )-8b was hydroborated with 9-BBN,
1H NMR of the crude reaction mixture showed a 1:1 mixture
Scheme 8.
Scheme 9.

D. J. Lapinsky, S. C. Bergmeier / Tetrahedron 58 (2002) 7109–7117
7113
of cis and trans amino alcohols. Subsequent Mitsunobu ring
closure provided the azabicycle 13 in 51% yield from olefin
(R )-8b. However, when BH3·THF was used in the
hydroboration a 1:2 mixture of cis and trans amino alcohols
was observed, thus providing only 30% yield of 13 after the
Mitsunobu reaction. Aziridine–allylsilane (R)-7b proved to
be a valuable intermediate towards both azabicyclo[3.2.1]
and [3.3.1]-systems (Scheme 9).
J¼8.78 Hz), 5.55–5.38 (m, 1H), 5.37 (d, 1H, J¼7.83 Hz),
4.99–4.93 (m, 2H), 3.62–3.48 (m, 2H), 3.29 (m, 1H), 2.69
(br s, 1H), 2.41 (s, 3H), 2.16 (m, 2H). 13C NMR (CDCl3,
100 MHz) d 143.4, 137.4, 133.3, 129.5, 127.0, 118.3, 63.9,
54.9, 35.8, 21.4. HRMS for C12H17NO3S·Naþ calcd
278.0821, found 278.0823.
1.1.2. 2-[2-Propenyl]-N-[(4-methylphenyl)sulfonyl]aziri-
dine (16). Ph3P (1.81 g, 6.90 mmol) was added to a stirred
solution of alcohol 15 (1.60 g, 6.27 mmol) in THF
(24.7 mL). The mixture was cooled to 08C and diethyl
azodicarboxylate (1.1 mL, 6.90 mmol) was added dropwise.
After the addition, the ice bath was removed and the
reaction was warmed to room temperature and stirred for
an additional 16 h. The mixture was concentrated and
chromatographed (8–15% EtOAc in hexanes) to give 1.23 g
of aziridine 16 (82%). Rf 0.21 (15% EtOAc in hexanes). 1H
NMR (CDCl3, 250 MHz) d 7.82 (d, 2H, J¼7.80 Hz), 7.33
(d, 2H, J¼8.80 Hz), 5.68–5.52 (m, 1H), 5.10–4.95 (m, 2H),
2.80 (m, 1H), 2.63 (d, 1H, J¼6.85 Hz), 2.44 (s, 3H), 2.31–
2.14 (m, 2H), 2.10 (d, 1H, J¼3.90 Hz). 13C NMR (CDCl3,
100 MHz) d 144.4, 134.9, 132.7, 129.5, 127.8, 117.5, 39.1,
35.0, 33.0, 21.5. HRMS for C12H15NO2S·Naþ calcd
260.0716, found 260.0710.
In conclusion, we have shown that connection of C-2 of
an allylsilane to a tethered aziridine ring yields exocyclic
g-amino olefins and desilylated azabicyclo[x.2.1]-systems
upon cyclization with BF3·OEt2. Furthermore, manipulation
of a specific exocyclic g-amino olefin provided access to an
azabicyclo[3.3.1]nonane. This methodology should be
useful for the preparation of natural products and pharma-
cologically active agents containing these bicyclic hetero-
cyclic systems.
1. Experimental
1.1. General
1H spectra were recorded on a Bruker AG 250 MHz
spectrometer. 13C spectra were recorded on a Varian VX
400 MHz spectrometer. Chemical shifts are reported in ppm
relative to CDCl3 (7.27 for 1H, 77.23 for 13C) or C6D6 (7.16
for 1H, 128.39 for 13C). Coupling constants (J ) are reported
in Hz. Thin layer chromatography (TLC) was performed on
EM Science pre-coated silica gel 60 F254 aluminum foils.
Purification of the reaction products was carried out by flash
chromatography using a glass column dry packed with silica
1.1.3. 2-[4-[(Trimethylsilyl)methyl]-4-pentenyl]-N-[(4-
methylphenyl)sulfonyl]aziridine (7b, racemic). A stirred
solution of olefin 16 (0.42 g, 1.77 mmol) in THF (6.1 mL)
was cooled to 08C and treated with 9-BBN (4.3 mL, 0.5 M
in THF, 2.13 mmol). After the addition, the ice bath was
removed and the mixture was warmed to room temperature
and stirred for an additional 3 h. DMF (3.1 mL) and K3PO4
(1.2 mL, 3 M in H2O, 3.72 mmol) were added followed
quickly by the addition of (2-bromoallyl)trimethylsilane
177 (0.3 mL, 1.95 mmol). PdCl2(dppf) ·CH2Cl2 (0.07 g,
0.09 mmol) was added and the mixture stirred at room
temperature for 18.5 h, then concentrated to the DMF layer.
The residue was taken up in Et2O and washed with H2O. The
layers were separated and the aqueous layer was extracted
with Et2O (£2). The combined organic layers were washed
with sat. aq. NaHCO3 solution, dried (MgSO4), filtered,
concentrated, and chromatographed (100% benzene) to give
0.36 g of racemic aziridine–allylsilane 7b (58%). Rf 0.31
(10% EtOAc in hexanes). 1H NMR (C6D6, 250 MHz) d 7.89
(d, 2H, J¼8.78 Hz), 6.73 (d, 2H, J¼7.83 Hz), 4.59 (app s,
2H), 2.71–2.62 (m, 1H), 2.44 (d, 1H, J¼6.85 Hz), 1.86 (s,
3H), 1.80 (t, 2H, J¼6.85 Hz), 1.52 (d, 1H, J¼4.88 Hz), 1.41
(s, 2H), 1.35–0.96 (m, 4H), 0.01 (s, 9H). 13C NMR (C6D6,
100 MHz) d 146.9, 143.8, 136.8, 129.6, 128.3, 107.7, 40.0,
37.8, 33.5, 31.1, 26.6, 25.2, 21.1, 21.3. HRMS for
C18H29NO2SSi·Naþ calcd 378.1530, found 378.1538.
˚
gel (ICN SiliTech 32-63D 60 A) according to the method of
Still.13 Visualization was accomplished with UV light, I2,
and/or phosphomolybdic acid solution followed by heating.
HRMS measurements were determined at the Ohio State
University Chemical Instrument Center with a Kratos
MS-30 mass spectrometer in the electron impact (EI)
mode. Optical activity was measured on an Autopol IV
automatic polarimeter. THF and Et2O were distilled from
sodium and benzophenone. DMF, CH2Cl2, and BF3·OEt2
were distilled from CaH2 before use. Et3N was distilled
from CaH2 and stored over KOH pellets. All reactions were
carried out in flame-dried glassware under an Ar atmosphere
unless otherwise specified.
1.1.1. N-[(4-Methylphenyl)sulfonyl]-2-amino-4-pentenol
(15). Dry LiCl (0.99 g, 23.4 mmol) was added to a stirred
solution of ester 146 (2.21 g, 7.81 mmol) in THF (10.9 mL)
and EtOH (21.8 mL). The mixture was cooled to 08C and
NaBH4 (0.89 g, 23.4 mmol) was added over 5 min. After the
addition, the ice bath was removed and the mixture was
warmed to room temperature and stirred for an additional
14 h. The reaction was quenched with acetone and
concentrated to a white residue, which was carefully
dissolved in 1 M HCl: EtOAc (ca. 1:1). The layers were
separated and the aqueous layer was extracted with EtOAc.
The combined organic layers were washed with brine, dried
(MgSO4), filtered, concentrated, and chromatographed
(40% EtOAc in hexanes) to give 1.60 g of alcohol 15
(80%). Rf 0.27 (40% EtOAc in hexanes). 1H NMR (CDCl3,
250 MHz) d 7.77 (d, 2H, J¼8.78 Hz), 7.29 (d, 2H,
1.1.4. 3-(N-[(4-Methylphenyl)sulfonyl]aminomethyl)-1-
methylenecyclohexane (8b, racemic). A stirred solution
of racemic aziridine 7b (0.94 g, 2.68 mmol) in CH2Cl2
(26.8 mL) was cooled to 2788C and treated with freshly
distilled BF3·OEt2 (0.2 mL, 1.34 mmol). After 1 h at 2788C
another 0.6 eq. (0.2 mL, 1.61 mmol) of BF3·OEt2 was
added. The reaction was stirred at 2788C for 3 h then
maintained at 2258C for 15 h. The reaction was quenched
with sat. aq. NaHCO3 solution then warmed to room
temperature. The layers were separated and the aqueous
layer was extracted with CH2Cl2. The combined organic

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D. J. Lapinsky, S. C. Bergmeier / Tetrahedron 58 (2002) 7109–7117
layers were dried (MgSO4), filtered, concentrated, and
chromatographed (25% Et2O in hexanes) to first provide
44.7 mg of racemic desilylated bicycle 10b (6%), followed
by 0.64 g of racemic exocyclic olefin 8b (86%). Rf 0.49 for
racemic desilylated bicycle 10b, 0.41 for racemic exocyclic
olefin 8b (25% EtOAc in hexanes). 1H NMR (C6D6,
250 MHz) d 7.90 (d, 2H, J¼8.78 Hz), 6.84 (d, 2H, J¼
7.83 Hz), 5.26 (t, 1H, J¼6.85 Hz), 4.62 (d, 2H, J¼4.88 Hz),
2.67 (t, 2H, J¼5.85 Hz), 2.19–2.01 (m, 2H), 1.92 (s, 3H),
1.79–1.66 (m, 1H), 1.54–1.32 (m, 4H), 1.17–1.03 (m, 1H),
0.87–0.72 (m, 1H). 13C NMR (C6D6, 100 MHz) d 147.7,
142.9, 138.4, 129.7, 127.5, 108.3, 48.8, 39.1, 38.9, 35.0,
29.8, 26.6, 21.1. HRMS for C15H21NO2S·Naþ 302.1185,
found 302.1169.
137.7, 129.6, 127.0, 115.0, 64.0, 54.4, 31.4, 29.7, 25.8, 21.4,
18.2, 25.6. HRMS for C19H33NO3SSi·Naþ calcd 406.1843,
found 406.1855.
1.1.7. (2R )-N-[(4-Methylphenyl)sulfonyl]-2-amino-4-
pentenol (21). A stirred solution of silyl ether 19 (4.70 g,
12.71 mmol) in THF (30.1 mL) was cooled to 08C and
treated with n-Bu4NF (14.0 mL, 1 M in THF, 13.98 mmol).
After 2 h at 08C the reaction was partitioned between H2O
and Et2O. The layers were separated and the aqueous layer
was extracted with Et2O. The combined organic layers were
washed with brine, dried (MgSO4), filtered, concentrated,
and chromatographed (40% EtOAc in hexanes) to give
2.49 g of alcohol 21 (77%). Analytical data was the same as
that reported for 15 except [a ]2D4¼23.58 (c 2.4, EtOAc).
1.1.5. (2R )-1-(tert-Butyldimethylsilyl)oxo-N-[(4-methyl-
phenyl)sulfonyl]-2-amino-4-pentene (19). Vinylmag-
nesium bromide (30.6 mL, 1 M in THF, 30.60 mmol) was
added to a 2788C slurry of CuCN (0.50 g, 5.64 mmol) in
Et2O (34 mL). After stirring for 20 min, a solution of
aziridine 185 (3.44 g, 10.07 mmol) in THF (51 mL) was
added via cannula. After the addition, the mixture was
maintained at 08C for 4 days then quenched with a solution
composed of 10% conc. NH4OH/90% sat. aq. NH4Cl
solution. The mixture was diluted with Et2O and stirred at
room temperature until all solids were dissolved (ca. 4 h).
The layers were separated and the aqueous layer was
extracted with Et2O. The combined organic layers were
washed with brine, dried (MgSO4), filtered, concentrated,
and chromatographed (10% EtOAc in hexanes) to give
3.31 g of silyl ether 19 (89%). Rf 0.32 (15% EtOAc in
hexanes), [a ]2D4¼þ17.98 (c 1.1, EtOAc). 1H NMR (CDCl3,
250 MHz) d 7.75 (d, 2H, J¼7.80 Hz), 7.30 (d, 2H,
J¼8.80 Hz), 5.68–5.51 (m, 1H), 5.04–4.98 (m, 2H), 4.75
(d, 1H, J¼7.80 Hz), 3.53–3.48 (m, 1H), 3.39–3.33 (m, 1H),
3.28 (m, 1H), 2.43 (s, 3H), 2.25 (t, 2H, J¼6.83 Hz), 0.85 (s,
9H), 20.01 (s, 3H), 20.03 (s, 3H). 13C NMR (CDCl3,
100 MHz) d 143.2, 137.8, 133.6, 129.5, 127.0, 118.2, 63.4,
54.2, 36.2, 25.7, 21.4, 18.1, 25.7. HRMS for C18H31NO3-
SSi·Naþ calcd 392.1686, found 392.1706.
1.1.8. (2R )-N-[(4-Methylphenyl)sulfonyl]-2-amino-5-
hexenol (22). A stirred solution of silyl ether 20 (5.80 g,
15.12 mmol) in THF (30.2 mL) was cooled to 08C and
treated with n-Bu4NF (16.6 mL, 1 M in THF, 16.63 mmol).
After 1 h at 08C the reaction was partitioned between H2O
and Et2O. The layers were separated and the aqueous layer
was extracted with Et2O. The combined organic layers were
washed with brine, dried (MgSO4), filtered, concentrated,
and chromatographed (40% EtOAc in hexanes) to give
3.59 g of alcohol 22 (88%). Rf 0.33 (50% EtOAc in
1
hexanes), [a]2D4¼þ3.58 (c 2.8, EtOAc). H NMR (CDCl3,
250 MHz) d 7.79 (d, 2H, J¼8.80 Hz), 7.31 (d, 2H, J¼
7.83 Hz), 5.68–5.51 (m, 1H), 5.37 (d, 1H, J¼8.80 Hz),
4.90–4.81 (m, 2H), 3.61–3.45 (m, 2H), 3.26 (m, 1H), 2.48
(br s, 1H), 2.42 (s, 3H), 2.03–1.78 (m, 2H), 1.61–1.38 (m,
2H). 13C NMR (CDCl3, 100 MHz) d 143.5, 137.7, 137.3,
129.7, 127.1, 115.2, 64.5, 55.0, 30.8, 29.6, 21.5. HRMS for
C13H19NO3S·Naþ calcd 292.0978, found 292.0972.
1.1.9. (2R)-2-[2-Propenyl]-N-[(4-methylphenyl)sulfonyl]-
aziridine (23). Ph3P (1.27 g, 4.83 mmol) was added to a
stirred solution of alcohol 21 (1.12 g, 4.39 mmol) in THF
(22.0 mL). The mixture was cooled to 08C and diethyl
azodicarboxylate (0.8 mL, 4.83 mmol) was added dropwise.
After the addition, the ice bath was removed and reaction
was warmed to room temperature and stirred for an
additional 4 h. The mixture was concentrated and chro-
matographed (8% to 15% EtOAc in hexanes) to give 0.94 g
1.1.6. (2R )-1-(tert-Butyldimethylsilyl)oxo-N-[(4-methyl-
phenyl)sulfonyl]-2-amino-5-hexene (20). Allylmagnesium
chloride (30.5 mL, 2 M in THF, 60.94 mmol) was added to
a 2788C slurry of CuCN (1.01 g, 11.23 mmol) in Et2O
(67.7 mL). After stirring for 20 min, a solution of aziridine
185 (6.85 g, 20.05 mmol) in THF (101.6 mL) was added via
cannula. After the addition, the reaction was maintained at
08C for 45 h then quenched with a solution composed of
10% conc. NH4OH/90% sat. aq. NH4Cl solution. The
mixture was diluted with Et2O and stirred at room
temperature until all solids were dissolved (ca. 6 h). The
layers were separated and the aqueous layer was extracted
with Et2O. The combined organic layers were washed with
brine, dried (MgSO4), filtered, concentrated, and chromato-
graphed (10% EtOAc in hexanes) to give 5.80 g of silyl
ether 20 (75%). Rf 0.24 (10% EtOAc in hexanes), [a ]2D5¼
þ25.48 (c 2.7, EtOAc). 1H NMR (CDCl3, 250 MHz) d 7.75
(d, 2H, J¼8.78 Hz), 7.29 (d, 2H, J¼8.78 Hz), 5.79–5.63
(m, 1H), 4.98–4.90 (m, 2H), 4.81 (d, 1H, J¼7.80 Hz),
3.44–3.29 (m, 2H), 3.24 (m, 1H), 2.42 (s, 3H), 2.07–1.96
(m, 2H), 1.61–1.52 (m, 2H), 0.84 (s, 9H), 20.03 (s, 3H),
20.05 (s, 3H). 13C NMR (CDCl3, 100 MHz) d 143.2, 138.3,
of aziridine 23 (90%). Analytical data was the same as that
reported for 16 except [a] ¼þ18.98 (c 4.3, EtOAc).
24
365
1.1.10. (2R)-2-[3-Butenyl]-N-[(4-methylphenyl)sulfonyl]-
aziridine (24). Ph3P (0.78 g, 2.96 mmol) was added to a
stirred solution of alcohol 22 (0.72 g, 2.69 mmol) in THF
(13.5 mL). The mixture was cooled to 08C and diethyl
azodicarboxylate (0.5 mL, 2.96 mmol) was added dropwise.
After the addition, the ice bath was removed and reaction
was warmed to room temperature and stirred for an
additional 4 h. The mixture was concentrated and chro-
matographed (15% EtOAc in hexanes) to give 0.63 g of
aziridine 24 (93%). Rf 0.32 (15% EtOAc in hexanes),
[a ]2D5¼27.08 (c 3.6, EtOAc). 1H NMR (CDCl3, 250 MHz) d
7.83 (d, 2H, J¼7.80 Hz), 7.34 (d, 2H, J¼8.78 Hz), 5.81–
5.65 (m, 1H), 5.01–4.93 (m, 2H), 2.75 (m, 1H), 2.63 (d, 1H,
J¼6.83 Hz), 2.44 (s, 3H), 2.08 (d, 1H, J¼4.90 Hz), 2.09–
1.99 (m, 2H), 1.72–1.58 (m, 1H), 1.52–1.37 (m, 1H). 13C
NMR (CDCl3, 100 MHz) d 144.4, 136.9, 135.1, 129.6,

D. J. Lapinsky, S. C. Bergmeier / Tetrahedron 58 (2002) 7109–7117
7115
127.9, 115.5, 39.7, 33.8, 30.7, 30.6, 21.6. HRMS for
C13H17NO2S·Naþ calcd 274.0872, found 274.0860.
J¼7.83 Hz), 4.99 (d, 1H, J¼7.80 Hz), 4.65 (s, 1H), 4.61
(s, 1H), 3.51–3.32 (m, 3H), 2.03–1.72 (m, 3H), 1.93 (s,
3H), 1.63–1.51 (m, 1H), 1.45 (s, 2H), 0.88 (s, 9H), 0.02 (s,
6H), 20.03 (s, 9H). 13C NMR (CDCl3, 100 MHz) d 146.6,
143.1, 138.2, 129.6, 127.0, 107.3, 64.0, 54.7, 34.1, 30.2,
26.6, 25.8, 21.4, 18.2, 21.4, 25.6. HRMS for C23H43NO3-
SSi2·Naþ calcd 492.2394, found 492.2403.
1.1.11. (2R )-2-[4-[(Trimethylsilyl)methyl]-4-pentenyl]-
N-[(4-methylphenyl)sulfonyl]aziridine ((R)-7b). Aziri-
dine–allylsilane (R )-7b was prepared using aziridine 23
(0.42 g, 1.77 mmol) following the same procedure as
reported for racemic 7b. This reaction provided 0.36 g of
(R)-7b (58%). Analytical data was the same as that reported
for 7b except [a] ¼þ14.58 (c 0.9, EtOAc).
1.1.14. (2R )-N-[(4-Methylphenyl)sulfonyl]-2-amino-5-
(trimethylsilyl)methyl-5-hexenol (28). A stirred solution
of silyl ether 27 (1.87 g, 3.97 mmol) in THF (4.1 mL) was
cooled to 08C and treated with n-Bu4NF (4.4 mL, 1 M in
THF, 4.37 mmol). The reaction was stirred for 30 min at
08C then partitioned between H2O and Et2O. The layers
were separated and the aqueous layer was extracted with
Et2O. The combined organic layers were washed with brine,
dried (MgSO4), filtered, concentrated, and chromato-
22
365
1.1.12. (2R )-2-[5-[(Trimethylsilyl)methyl]-5-hexenyl]-N-
[(4-methylphenyl)sulfonyl]aziridine ((R )-7c). A stirred
solution of olefin 24 (0.98 g, 3.90 mmol) in THF (13.4 mL)
was cooled to 08C and treated with 9-BBN (8.6 mL, 0.5 M
in THF, 4.29 mmol). After the addition, the ice bath was
removed and the mixture was warmed to room temperature
and stirred for an additional 7 h. (2-Bromoallyl)trimethyl-
silane 177 (0.84 g, 4.34 mmol), DMF (5.0 mL), K3PO4
(2.7 mL, 3 M in H2O, 8.18 mmol), and PdCl2(dppf)·CH2Cl2
(0.16 g, 0.19 mmol) were added to a separate flask and the
organoborane solution was added via cannula with an
additional DMF (1.7 mL) rinsing. After the addition, the
reaction was stirred at room temperature for 25 h then
poured into Et2O and washed with H2O and brine. The
aqueous layers were extracted with Et2O (£3). The
combined organic layers were dried (MgSO4), filtered,
concentrated, and chromatographed (50% hexanes in
graphed (60% Et2O in hexanes) to give 1.39 g of alcohol
28 (98%). Rf 0.24 (30% EtOAc in hexanes), [a] ¼24.98
24
365
1
(c 7.4, EtOAc). H NMR (C6D6, 250 MHz) d 7.94 (d, 2H,
J¼7.83 Hz), 6.89 (d, 2H, J¼8.78 Hz), 5.94 (d, 1H, J¼
7.80 Hz), 4.57 (s, 1H), 4.55 (s, 1H), 3.72–3.64 (m, 1H),
3.56–3.48 (m, 1H), 3.37–3.35 (m, 1H), 3.20 (t, 1H, J¼
5.88 Hz), 1.95 (s, 3H), 1.92–1.51 (m, 4H), 1.35 (s, 2H),
20.02 (s, 9H). 13C NMR (CDCl3, 100 MHz) d 146.2, 143.3,
137.8, 129.7, 127.1, 107.4, 64.5, 55.4, 34.1, 29.6, 26.5, 21.5,
21.5. HRMS for C17H29NO3SSi·Naþ calcd 378.1530,
found 378.1513.
benzene then 100% benzene) to give 0.96 g of aziridine–
24
allylsilane (R )-7c (68%). Rf 0.34 (Benzene), [a]
¼
1.1.15. (2R)-2-[3-[(Trimethylsilyl)methyl]-3-butenyl]-N-
Ph3P
365
þ16.28 (c 7.5, EtOAc). 1H NMR (CDCl3, 250 MHz) d
7.81 (d, 2H, J¼7.80 Hz), 7.32 (d, 2H, J¼8.80 Hz), 4.51 (app
s, 1H), 4.48 (app s, 1H), 2.71 (m, 1H), 2.62 (d, 1H, J¼
6.83 Hz), 2.43 (s, 3H), 2.05 (d, 1H, J¼4.88 Hz), 1.85 (t, 2H,
J¼7.80 Hz), 1.47 (s, 2H), 1.59–1.16 (m, 6H), 0.00 (s, 9H).
13C NMR (CDCl3, 100 MHz) d 147.1, 144.3, 135.1, 129.6,
127.9, 107.0, 40.3, 37.9, 33.7, 31.2, 27.1, 26.6, 26.4, 21.6,
21.4. HRMS for C19H31NO2SSi·Naþ calcd 388.1737,
found 388.1735.
[(4-methylphenyl)sulfonyl]aziridine
((R)-7a).
(0.98 g, 3.72 mmol) was added to a stirred solution of
alcohol 28 (1.20 g, 3.38 mmol) in THF (13.3 mL). The
mixture was cooled to 08C and diethyl azodicarboxylate
(0.6 mL, 3.72 mmol) was added dropwise. After the
addition, the ice bath was removed and the reaction was
warmed to room temperature and stirred for an additional
2.5 h. The mixture was concentrated and chromatographed
(2% to 15% EtOAc in hexanes) to give 0.82 g of aziridine
(R )-7a (72%). Rf 0.37 (15% EtOAc in hexanes), [a ]2D4¼
1
1.1.13. (2R)-1-(tert-Butyldimethylsilyl)oxo-N-[(4-methyl-
phenyl)sulfonyl]-2-amino-5-(trimethylsilyl)methyl-5-
hexene (27). A solution of allylselenide 259 (1.44 g,
6.51 mmol) in THF (4.3 mL) was added dropwise to a
2788C stirred solution of n-BuLi (3.3 mL, 1.96 M in
hexanes, 6.51 mmol). After 40 min the allyllithium solution
was transferred via cannula into a flask containing a 2788C
slurry of CuCN (0.29 g, 3.25 mmol) in THF (3.8 mL). After
8 min the mixture was warmed to 08C and stirred for 1 h.
The reaction was recooled to 2788C and a solution of
aziridine 185 (0.74 g, 2.17 mmol) in THF (2.3 mL) was
added via cannula. After the addition, the reaction was
maintained at 08C for 22.5 h then quenched with a solution
composed of 10% conc. NH4OH/90% sat. aq. NH4Cl
solution. The mixture was diluted with Et2O then stirred at
room temperature to allow the solids to dissolve. The layers
were separated and the aqueous layer was extracted with
Et2O (£3). The combined organic layers were washed with
H2O, brine, dried (MgSO4), filtered, concentrated, and
chromatographed (100% hexanes then 100% benzene) to
give 0.66 g of allylsilane silyl ether 27 (64%). Rf 0.29
(Benzene), [a]2D4¼þ16.58 (c 4.3, EtOAc). 1H NMR (C6D6,
250 MHz) d 7.85 (d, 2H, J¼7.83 Hz), 6.81 (d, 2H,
210.28 (c 5.8, EtOAc). H NMR (C6D6, 250 MHz) d 7.88
(d, 2H, J¼8.78 Hz), 6.74 (d, 2H, J¼8.80 Hz), 4.57 (s, 2H),
2.74–2.64 (m, 1H), 2.44 (d, 1H, J¼6.85 Hz), 1.86 (s, 3H),
1.83 (t, 2H, J¼7.80 Hz), 1.54 (d, 1H, J¼4.88 Hz), 1.53–
1.38 (m, 1H), 1.35 (s, 2H), 1.33–1.09 (m, 1H), 20.04 (s, 9H).
13C NMR (CDCl3, 100 MHz) d 145.9, 144.4, 135.1, 129.6,
128.0, 107.4, 40.1, 35.1, 33.7, 29.6, 26.8, 21.6, 21.5. HRMS
for C17H27NO2SSi·Naþ calcd 360.1424, found 360.1411.
1.1.16. (3R )-3-(N-[(4-Methylphenyl)sulfonyl]amino-
methyl)-1-methylenecyclohexane ((R )-8b). A stirred solu-
tion of aziridine (R )-7b (0.53 g, 1.52 mmol) in CH2Cl2
(15.2 mL) was cooled to 2788C and treated with freshly
distilled BF3·OEt2 (0.2 mL, 1.52 mmol). The reaction was
stirred for 1 h at 2788C then maintained at 2258C for 22 h.
The reaction was quenched with sat. aq. NaHCO3 solution
then warmed to room temperature. The layers were
separated and the aqueous layer was extracted with
CH2Cl2. The combined organic layers were dried
(MgSO4), filtered, concentrated, and chromatographed
(25% Et2O in hexanes) to give 0.41 g of exocyclic olefin
(R )-8b (97%). Analytical data was the same as that reported
for 8b except [a ]2D3¼221.58 (c 1.8, EtOAc).

7116
D. J. Lapinsky, S. C. Bergmeier / Tetrahedron 58 (2002) 7109–7117
1.1.17. (3R )-3-(N-[(4-Methylphenyl)sulfonyl]amino-
methyl)-1-methylenecycloheptane ((R )-8c). A stirred
solution of aziridine (R)-7c (0.37 g, 1.0 mmol) in CH2Cl2
(10.0 mL) was cooled to 2788C and treated with freshly
distilled BF3·OEt2 (0.3 mL, 2.0 mmol). The reaction was
stirred for 1 h at 2788C then maintained at 08C for 19 h. The
reaction was quenched with sat. aq. NaHCO3 solution then
warmed to room temperature. The layers were separated
and the aqueous layer was extracted with CH2Cl2. The
combined organic layers were dried (MgSO4), filtered,
concentrated, and chromatographed (25% Et2O in hexanes)
to give 0.15 g of exocyclic olefin (R)-8c (51%). Rf 0.40
(25% EtOAc in hexanes), [a]2D4¼þ7.58 (c 2.2, EtOAc). 1H
NMR (CDCl3, 250 MHz) d 7.75 (d, 2H, J¼8.78 Hz), 7.30
(d, 2H, J¼8.80 Hz), 4.88 (t, 1H, J¼5.85 Hz), 4.69 (app s,
1H), 4.64 (app s, 1H), 2.79 (t, 2H, J¼6.83 Hz), 2.42 (s, 3H),
2.38–2.24 (m, 1H), 2.18–1.85 (m, 2H), 1.72–1.57 (m, 5H),
1.42–1.07 (m, 3H). 13C NMR (CDCl3, 100 MHz) d 148.9,
143.2, 137.0, 129.6, 127.0, 112.0, 49.0, 39.3, 39.2, 36.1,
142.1, 139.9, 129.4, 127.5, 68.6, 56.4, 43.7, 40.8, 34.9, 33.5,
28.8, 25.5, 23.9, 21.1. HRMS for C16H23NO2S·Naþ calcd
316.1342, found 316.1330.
1.1.20. 4-(N-[(4-Methylphenyl)sulfonyl]amino)-1-
methylenecyclohexane (29). A stirred solution of aziridine
(R )-7a (0.18 g, 0.54 mmol) in CH2Cl2 (5.4 mL) was cooled
to 2788C and treated with freshly distilled BF3·OEt2
(0.1 mL, 1.09 mmol). The reaction was stirred at 2788C
for 1 h then maintained at 08C for 16.5 h. The mixture was
quenched with sat. aq. NaHCO3 solution then warmed to
room temperature. The layers were separated and the
aqueous layer was extracted with CH2Cl2 (£2). The
combined organic layers were dried (MgSO4), filtered,
concentrated, and chromatographed (25% Et2O in hexanes)
to give 71.6 mg of olefin 29 (50%). Rf 0.37 (25% EtOAc in
1
hexanes). H NMR (CDCl3, 250 MHz) d 7.79 (d, 2H, J¼
7.83 Hz), 7.30 (d, 2H, J¼8.80 Hz), 4.84 (d, 1H, J¼6.83 Hz),
4.60 (app s, 2H), 3.35–3.21 (m, 1H), 2.43 (s, 3H), 2.26–
2.17 (m, 2H), 2.05–1.93 (m, 2H), 1.86–1.68 (m, 2H), 1.38–
1.23 (m, 2H). 13C NMR (CDCl3, 100 MHz) d 146.5, 143.2,
138.2, 129.6, 126.9, 108.3, 51.8, 34.4, 32.4, 21.5. HRMS for
C14H19NO2S·Naþ calcd 288.1029, found 288.1032.
1
32.7, 28.2, 26.8, 21.5. H and 13C NMR also contained
signals representing a small amount (ca. ,5%) of iso-
merized amino olefin. HRMS for C16H23NO2S·Naþ calcd
316.1342, found 316.1338.
1.1.18. (1R,5S )-5-Methyl-6-[(4-methylphenyl)sulfonyl]-
6-azabicyclo[3.2.1]octane ((1R,5S )-10b). A stirred solu-
tion of allylsilane (R )-7b (0.38 g, 1.07 mmol) in CH2Cl2
(10.8 mL) was cooled to 2788C and treated with freshly
distilled BF3·OEt2 (0.4 mL, 3.22 mmol). After the addition,
the ice bath was removed and the reaction was stirred at
room temperature for 16 h then quenched with sat. aq.
NaHCO3 solution and diluted with CH2Cl2. The layers were
separated and the aqueous layer was extracted with CH2Cl2
(£2). The combined organic layers were dried (MgSO4),
filtered, concentrated, and chromatographed (15% EtOAc in
hexanes) to give 0.23 g of (1R,5S )-10b (77%). Rf 0.49 (25%
EtOAc in hexanes), [a ]2D4¼26.48 (c 2.2, EtOAc). 1H NMR
(C6D6, 250 MHz) d 7.82 (d, 2H, J¼8.78 Hz), 6.83 (d, 2H,
J¼8.80 Hz), 3.52 (d, 1H, J¼9.76 Hz), 3.24–3.18 (m, 1H),
2.19–2.12 (m, 1H), 1.94 (s, 3H), 1.88–1.66 (m, 2H), 1.45
(s, 3H), 1.36–1.25 (m, 3H), 1.11–0.99 (m, 3H). 13C NMR
(CDCl3, 100 MHz) d 142.3, 139.9, 129.3, 126.5, 66.4,
54.4, 47.2, 37.8, 32.4, 29.9, 24.9, 21.4, 19.3. HRMS for
C15H21NO2S·Naþ calcd 302.1185, found 302.1189.
1.1.21. (1R,5S)-3-[(4-Methylphenyl)sulfonyl]-3-azabicyclo-
[3.3.1]nonane (13): using 9-BBN. A solution of olefin
(R )-8b (0.55 g, 1.98 mmol) in THF (4.1 mL) was treated
with 9-BBN (15.8 mL, 0.5 M in THF, 7.91 mmol) at room
temperature and stirred for 6.5 h. The reaction was then
cooled to 08C and treated with EtOH (4.65 mL) dropwise,
followed by stirring for 5 min to quench the excess 9-BBN.
6N aq. NaOH (1.6 mL) was then added dropwise followed
by 30% H2O2 (2.9 mL). After the addition, the mixture was
refluxed for 1 h, cooled to room temperature and diluted
with H2O and EtOAc. The layers were separated and
the aqueous layer was extracted with EtOAc (£2). The
combined organic layers were washed with brine, dried
1
(MgSO4), filtered, and concentrated. H NMR of the crude
reaction mixture indicated a 1:1 mixture of cis and trans
amino alcohols 30. The crude mixture was chromato-
graphed (50% EtOAc in hexanes) to give 0.59 g of a mixture
of alcohols 30 (100%), which was immediately used in the
Mitsunobu reaction. Ph3P (0.57 g, 2.18 mmol) was added to
a stirred solution of the alcohol mixture 30 (0.59 g,
1.98 mmol) in THF (7.8 mL). The mixture was cooled to
08C and diethyl azodicarboxylate (0.3 mL, 2.18 mmol) was
added dropwise. After the addition, the ice bath was
removed and the reaction was warmed to room temperature
and stirred for an additional 17 h. The mixture was
concentrated and chromatographed (4–10% EtOAc in
hexanes) to give 0.28 g of bicycle 13 (51% from (R )-8b).
1.1.19. (1R,6S )-6-Methyl-7-[(4-methylphenyl)sulfonyl]-
7-azabicyclo[4.2.1]nonane ((1R,6S)-10c). A stirred solu-
tion of aziridine (R )-7c (0.38 g, 1.04 mmol) in CH2Cl2
(10.4 mL) was cooled to 2788C and treated with freshly
distilled BF3·OEt2 (0.4 mL, 3.11 mmol). After the addition,
the ice bath was removed and the reaction was stirred at
room temperature for 23 h then refluxed for 23 h. The
reaction was diluted with CH2Cl2 and quenched with sat.
aq. NaHCO3 solution. The layers were separated and the
aqueous layer was extracted with CH2Cl2 (£2). The com-
bined organic layers were dried (MgSO4), filtered, con-
centrated, and chromatographed (15% EtOAc in hexanes) to
give 0.11 g of (1R,6S )-10c (37%). Rf 0.46 (25% EtOAc in
1.1.22. Using BH3·THF. A stirred solution of olefin (R )-8b
(0.52 g, 1.85 mmol) in THF (3.8 mL) was treated with
BH3·THF (7.4 mL, 1 M in THF, 7.41 mmol) at 08C then
warmed to room temperature and stirred for an additional
6.5 h. The above oxidation protocol was followed using
EtOH (4.7 mL), 6N aq. NaOH (1.5 mL), and 30% H2O2
(2.7 mL). Standard work up gave 0.54 g of a 1:2 mixture
1
hexanes), [a]2D4¼27.98 (c 3.5, EtOAc). H NMR (C6D6,
1
250 MHz) d 7.82 (d, 2H, J¼7.80 Hz), 6.85 (d, 2H, J¼
8.78 Hz), 3.29 (d, 1H, J¼9.78 Hz), 3.19–3.12 (m, 1H),
2.69–2.58 (m, 1H), 1.95 (s, 3H), 1.86–1.71 (m, 1H), 1.69–
1.12 (m, 9H), 1.43 (s, 3H). 13C NMR (C6D6, 100 MHz) d
(via crude H NMR) of cis and trans amino alcohols 30
(99%), which was immediately used in the Mitsunobu
reaction. Ph3P (0.53 g, 2.02 mmol) was added to a stirred
solution of the alcohol mixture 30 (0.54 g, 1.83 mmol) in

D. J. Lapinsky, S. C. Bergmeier / Tetrahedron 58 (2002) 7109–7117
7117
9411–9412. (d) Jeyaraman, R.; Avila, S. Chem. Rev. 1981, 81,
149–174.
THF (7.2 mL). The mixture was cooled to 08C and treated
with diethyl azodicarboxylate (0.3 mL, 2.02 mmol) drop-
wise. After the addition, the ice bath was removed and the
reaction was warmed to room temperature and stirred for
an additional 15 h. The mixture was concentrated and
chromatographed (4–10% EtOAc in hexanes) to give 0.15 g
of bicycle 13 (30% from (R )-8b). Rf 0.43 (25% EtOAc in
4. Bergmeier, S. C.; Lapinsky, D. J. Tetrahedron Lett. 2001, 42,
8583–8586.
5. Bergmeier, S. C.; Seth, P. P. J. Org. Chem. 1997, 62,
2671–2674.
6. (a) Voigtmann, U.; Blechert, S. Synthesis 2000, 6, 893–898.
(b) Varray, S.; Gauzy, C.; Lamaty, F.; Lazaro, R.; Martinez, J.
J. Org. Chem. 2000, 65, 6787–6790. (c) Witulski, B.;
Gossman, M. Chem. Commun. 1999, 18, 1879–1880.
(d) Bolton, G. L.; Hodges, J. C.; Rubin, J. R. Tetrahedron
1997, 53, 6611–6634.
1
hexanes). H NMR (CDCl3, 250 MHz) d 7.61 (d, 2H, J¼
7.50 Hz), 7.31 (d, 2H, J¼7.50 Hz), 3.75 (d, 2H, J¼
11.73 Hz), 2.51–2.42 (m, 3H), 2.42 (s, 3H), 1.89–1.85
(m, 4H), 1.73–1.44 (m, 4H), 1.36–1.30 (m, 1H). 13C NMR
(CDCl3, 100 MHz) d 143.1, 132.5, 129.4, 127.6, 51.1, 32.4,
30.6, 28.0, 21.4, 20.8. HRMS for C15H21NO2S·Naþ calcd
302.1185, found 302.1169.
7. (2-Bromoallyl)trimethylsilane is commercially available from
Aldrich Chemical Co. or can easily be prepared via: Trost,
B. M.; Grese, T. A.; Chan, D. M. T. J. Am. Chem. Soc. 1991,
113, 7350–7362.
8. Kim, S. H.; Fuchs, P. L. Tetrahedron Lett. 1996, 37,
2545–2548.
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