A stereoselective synthesis of alkynylaziridines

Article abstract of DOI:10.1002/1099-0690(200204)2002:8<1385::AID-EJOC1385>3.0.CO;2-K

Reactions between allenylzinc carbenoid 1 and various imines were examined; trans-substituted alkynylaziridines were produced with excellent diastereoselectivity. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.

Full text of DOI:10.1002/1099-0690(200204)2002:8<1385::AID-EJOC1385>3.0.CO;2-K

FULL PAPER
A Stereoselective Synthesis of Alkynylaziridines[‡]
[
a]
[a]
[a]
[a]
Fabrice Chemla,* Franck Ferreira, Virginie Hebbe, and Eric Stercklen
Keywords: Allenylmetal compounds / Aziridines / Carbenoids / Zinc
Reactions between allenylzinc carbenoid 1 and various im-
( Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany,
ines were examined; trans-substituted alkynylaziridines 2002)
were produced with excellent diastereoselectivity.
Results and Discussion
Introduction
Reaction with N-Benzylimines
Aziridines have provoked considerable interest over re-
Reactions between 1 and N-benzylaldimines were found
[
2Ϫ7]
cent years.
In contrast, however, very few syntheses of to occur at temperatures higher (Ϫ10 °C) than those re-
alkynylaziridines have been reported. They had previously quired for reactions with aldehydes. Ring-closure to azirid-
been prepared by treatment of nitrenes or nitrene equiva- ines occurred in the course of the reaction, and alkynylaziri-
[
8,9]
lents with enynes,
or from the corresponding alkynyloxi- dines were obtained in good to excellent yields directly
ranes in a two-step reaction.[ More recently, the con- upon hydrolysis. These aziridines 2aϪf were obtained as
10]
[11Ϫ13]
densation of propargylsulfonium ylides
or of lithiated single invertomers, the benzyl group presumably lying on
onto imines has been described, as the same side as the acetylenic moiety. Only in the case of
well as the preparation of optically pure aziridines from the reaction with N-cyclohexylidenebenzylamine was the re-
[
14]
cinnamyl chloride
[
15Ϫ17]
[1]
amino acids.
stereoselective synthesis of alkynyloxiranes by the con- in a 50:50 ratio. Our results are summarized in Table 1.
densation of the new allenylzinc carbenoid 1 with aldehydes
The stereochemistries of the aziridines were determined
Very recently, we have reported
a
sulting aziridine obtained as a mixture of two invertomers,
and ketones (Scheme 1). Here we report our studies into by measurement of the coupling constants of the two azirid-
1
reactions between 1 and various imines, which afforded inyl protons by H NMR. All the aziridines were found to
trans-substituted alkynylaziridines with excellent stereocon- be purely trans-substituted, whatever the stereochemistry of
[
18]
trol.
the starting imine. This stereoselectivity can easily be ex-
plained in terms of a cyclic transition state analogous to
the Chodkiewicz model[
19,20]
for the case of aldehydes
(
Scheme 2).
In order to prepare homochiral aziridines, treatment of 1
with N-(α-methylbenzyl)imines was investigated. Unfortu-
nately, no reaction was observed below 0 °C, while decom-
position of carbenoid 1 occurred at higher temperatures. A
similar lack of reactivity was observed in the case of N-
tritylimines and N-(4-methoxyphenyl)imines.
Reaction with N-(Trimethylsilyl)imines
Scheme 1
The N-(trimethylsilyl)imines used in this study were pre-
pared in situ by treatment of the corresponding aldehydes
[
21Ϫ23]
with LiHMDS,
or of organolithium reagents with
N,N-bis(trimethylsilyl)formamide.[ Condensation with 1
24]
[
‡]
a]
[1]
Propargylic Carbenoids, 2. Ϫ Part 1: Ref.
[
Laboratoire de Chimie des OrganoEl e´ ments, Tour 44Ϫ45, 2 e` me occurred at a lower temperature (Ϫ50 to Ϫ35 °C) than with
Etage, Bo ˆı te 183, Universit e´ Pierre et Marie Curie
N-benzylimines (except in the case of the imine derived
from pivalaldehyde, which did not react below Ϫ10 °C),
and upon hydrolysis the corresponding N-H aziridines
4
Place Jussieu, 75252 Paris Cedex 05, France
Fax: (internat.) ϩ 33-1/44277567
E-mail: fchemla@ccr.jussieu.fr
Eur. J. Org. Chem. 2002, 1385Ϫ1391

WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002 1434Ϫ193X/02/0408Ϫ1385 $ 20.00ϩ.50/0
1385

F. Chemla, F. Ferreira, V. Hebbe, E. Stercklen
FULL PAPER
Table 1. Preparation of alkynyl-substituted N-benzylaziridines
Table 2. Preparation of alkynyl-substituted N-H aziridines
[a]
Not determined. [b] Reaction performed at Ϫ10 °C.
[
a]
[b]
3 2
No purification was necessary. In the presence of BF ϪEt O
2 equiv.): 50% yield by 1H NMR.
[c]
As a mixture of two
(
invertomers in a 50:50 ratio.
Table 3. Transformation of N-H into N-benzylaziridines
Scheme 2
3
a,cϪe,g,h were obtained in good to excellent yields. Two
invertomers were observed in each case, in variable ratios
(Table 2).
The stereochemistries of the formed N-H aziridines could
1
not be determined by H NMR. They were next trans-
formed into the corresponding N-benzylaziridines by treat-
ment with benzyl bromide (Table 3). The obtained N-
benzylaziridines were again found to be purely trans-substi-
tuted and to be single invertomers (except in the case of
aziridine 2a, which was found to be a mixture of two
invertomers in a 65:35 ratio) identical to the materials previ-
ously prepared. It had to be concluded that the trans-substi-
tuted N-H aziridines were also formed with excellent ste-
reocontrol, which could again be explained by following the
transition state, similar to that depicted in Scheme 2. More-
over, the fact that only one invertomer was obtained upon
stereochemistry (the benzyl group being cis to the acetylenic
moiety), as the alkylation reaction should take place on the
less hindered side of the N-H aziridine.
Reaction with N-Sulfonylimines
Reactions between 1 and the more reactive N-sulfonylim-
benzylation in most cases supports the assignment of its ines[ were found to be surprisingly low-yielding. The cor-
25]
1386
Eur. J. Org. Chem. 2002, 1385Ϫ1391

A Stereoselective Synthesis of Alkynylaziridines
FULL PAPER
Table 4. Preparation of alkynyl-substituted N-sulfonylaziridines
Scheme 4
(
Scheme 4). Since the sulfonyl group is strongly electron-
withdrawing, the lone electron pair on the nitrogen atom
should be deactivated, and the general chelate transition
state TS2 followed by N-benzyl- and N-(trimethylsilyl)im-
ines should then be less favoured relative to TS1. This
would explain the lower diastereoselectivity in the forma-
tion of 5a and 5b. However, the reasons why the transition
state TS1 should be favoured over TS2 in the case of imine
responding N-tosylaziridines were obtained in low to fair
yields (Table 4). Moreover, the diastereoselectivity was
lower than in the cases reported above, and was also de-
pendent on the nature of the substituent on the starting
imine. With aliphatic N-tosylimines 4a and 4b, the corres-
ponding aziridines 5a and 5b were obtained in a 70:30 ratio
in favour of the trans isomer. In contrast, aziridine 5c, de-
rived from N-benzylidenebenzenesulfonamide (4c), was ob-
tained in a 90:10 ratio in favour of the cis isomer.
4
c remain unclear. It could be attributed to a possible
[30Ϫ33]
areneϪzinc interaction,
or to a possible π-stacking-
type interaction[
34,35]
between the aromatic ring and the al-
It has been shown that, under equilibrating conditions,
[
26Ϫ28]
lenyl moiety. It should be noted that the same tendency has
previously been observed in the case of aromatic aldehydes,
albeit in a much lower extent.[ These possibilities are cur-
rently under investigation in our laboratory.
unsaturated cis-N-sulfonylaziridines
and -N-phenyl-
[
16]
aziridines were formed in preference to the trans isomer.
1]
The same behaviour was reported in the case of diaryl-N-
trimethylsilyl)aziridines.[
29]
(
In order to ascertain whether
the strong cis preference in the formation of 5c was due to
a thermodynamic preference, the reaction between 1 and
Conclusion
4
c was quenched at low temperature. The alkynylchloro-N-
We report a new one-step synthesis of alkynylaziridines
by treatment of an allenylzinc carbenoid with various im-
ines. This methodology allows the formation of trans-alky-
nyl-substituted N-H and N-benzylaziridines with very high
stereoselectivities. We are currently working on some other
applications of this methodology, as well as its extension to
the enantiomerically pure series.
sulfonylamine intermediate 6 was obtained, together with
starting material, in low yield (11%) but in a 90:10 ratio in
favour of the syn isomer, as demonstrated by further ring-
Experimental Section
General Remarks: Experiments involving organometallic com-
pounds were carried out in dried glassware under a positive pres-
sure of dry nitrogen. Liquid nitrogen was used as a cryoscopic fluid.
A four-necked, round-bottomed flask equipped with an internal
thermometer, a septum cap, a nitrogen inlet, and a mechanic stirrer
was used. THF was freshly distilled from sodium benzophenone
ketyl prior to use. Zinc bromide (98%) was purchased from Aldrich.
It was melted under dry nitrogen and, immediately after cooling
to room temperature, was dissolved in anhydrous THF. All other
reagents and solvents were of commercial quality and were used
without purification. Flash column chromatographic separations
Scheme 3
closure to 7 (Scheme 3). The diastereomeric ratio in 7 was
identical to that in 5c, thus demonstrating that the syn pref-
erence was not related to any equilibration under the reac-
tion conditions.
1
were carried out on Merck 60 silica gel (0.015Ϫ0.040 mm).
H
1
3
The formation of the syn diastereomer of 5c could also NMR and C NMR spectra were recorded with Bruker ARX 400
be explained in terms of an open transition state TS1 or AC 200 spectrometers. Chemical shifts are reported in δ relative
Eur. J. Org. Chem. 2002, 1385Ϫ1391
1387

F. Chemla, F. Ferreira, V. Hebbe, E. Stercklen
saturated aqueous NH Cl solution and NH . After the mixture had
FULL PAPER
to an internal standard of residual chloroform (δ ϭ 7.27 for 1H
4
3
NMR and δ ϭ 77.1 for 13C NMR) unless otherwise noted. IR warmed to room temperature, the aqueous layer was extracted with
spectra were recorded with a PerkinϪElmer 1420 spectrophoto-
meter. Mass spectra were performed by the Service de Spectrom e´ -
trie de Masse de l’Universit e´ Pierre et Marie Curie. Elemental ana-
lyses were performed by the Service de Microanalyses de l’Univers-
Et
a saturated aqueous NaHCO
dried with anhydrous Na SO
dryness. The crude brownish oils were purified by flash chromato-
O/2% Et N/pentane, to give N-H azirid-
2
O (three times). The combined organic layers were washed with
solution, water (twice) and brine,
, and then concentrated in vacuo to
3
2
4
it e´ Pierre et Marie Curie. Some elemental analyses could not be graphy, eluting with 3% Et
2
3
obtained, presumably due to the hygroscopic character of the cor-
responding aziridines.
ines 3 as yellow oils.
General Procedure 6. Preparation of N-Benzylaziridines 2 from N-
H Aziridines 3: Benzyl bromide (3.5 equiv.) was added dropwise at
General Procedure 1. Preparation of Allenylzinc Compound 1: 1-
Chloro-3-(trimethylsilyl)prop-2-yne[
36,37]
(1.0 equiv.) was added at room temperature, under argon, to a stirred 0.1  suspension of
Ϫ20 °C to a solution of ZnBr (1.0 , 2.0 equiv.) in THF. The N-H aziridines 3 (1.0 equiv.) and K CO (3.5 equiv.) in 10% DMF/
2
2 3
resulting white suspension was cooled to Ϫ80 °C, and a freshly
prepared solution of lithium diisopropylamide (1.0 , 2.0 equiv.)
in anhydrous THF was slowly added dropwise. The yellow solution
was stirred at Ϫ80 °C for 1 h and immediately used for the prepara-
tion of aziridines.
2 2
CH Cl . The mixture was stirred at room temperature for 3 d and
was then quenched with a 65:35 mixture of a saturated aqueous
NH Cl solution and NH . The aqueous layer was extracted with
4
3
Et O (three times), and the combined organic layers were washed
2
with water and brine, dried with anhydrous MgSO , and then con-
4
centrated to dryness in vacuo. The crude oils were purified by flash
chromatography, eluting with 2% Et N/pentane, to afford N-
3
benzylaziridines 2 as pale yellow oils.
General Procedure 2. Preparation of N-Benzylimines: Molecular
sieves (4 A, 0.6 g/1.00 mmol of aldehyde) were added under argon
to a 1.0  solution of the aldehyde (1.0 equiv.) and benzylamine
˚
(
2 2
1.0 equiv.) in CH Cl . The resulting suspension was stirred over-
(
(
2R*,3R*)-N-Benzyl-3-(n-butyl)-2-[(trimethylsilyl)ethynyl]aziridine
2a): This compound was prepared by General Procedure 4, from
night at room temperature, and after filtration through a Celite
pad, the volatiles were removed in vacuo to afford N-benzylimines
as pale yellow oils in yields from 30 to 100%.
N-pentylidenebenzylamine (870 mg, 5.00 mmol) in 50% yield
(
2
0
2
3
600 mg, 2.50 mmol); trans/cis Ͼ 98:2. IR (NaCl, film): ν˜ ϭ 2980,
Ϫ1
1
910, 2840, 2160, 840 cm
3
. H NMR (CDCl , 400 MHz): δ ϭ
General Procedure 3. Preparation of N-Sulfonylimines 4: A 0.5 
solution of sodium 4-methylbenzenesulfinate (1.0 equiv.), benzene-
sulfonamide (1.0 equiv.), or 4-methylbenzenesulfonamide (1.0
equiv.) and aldehyde (1.0 equiv.) in a 40% water/formic acid mix-
ture was stirred at room temperature for 20 h. After filtration, the
white solid was washed successively with water and pentane and
then taken up into CH
which was treated with a saturated aqueous NaHCO
stirred for 5 h at room temperature. The aqueous layer was then
extracted with CH Cl (twice). The combined organic layers were
washed with brine, dried with anhydrous NaHCO and then con-
.24 (s, 9 H), 0.86 (m, 3 H), 1.19Ϫ1.50 (m, 6 H), 1.77 (m, 1 H),
3
2
.38 (d, J ϭ 3.4 Hz, 1 H), 3.60 (AB system, J ϭ 13.2 Hz, 1 H),
2
13
.87 (AB system, J ϭ 13.2 Hz, 1 H), 7.26Ϫ7.43 (m, 5 H).
, 100.6 MHz): δ ϭ 0.0, 14.0, 22.4, 29.2, 32.4, 32.8,
8.7, 58.4, 88.8, 102.7, 127.0, 128.3, 128.7, 139.3. MS (E.I., 70 eV):
C
NMR (CDCl
4
3
m/z (%) ϭ 285 (31), 212 (12), 194 (100), 91 (71), 73 (53). This
compound was also prepared by General Procedure 6, from N-H
aziridine 3a (see below; 195 mg, 1.00 mmol) in 69% yield (196 mg,
2
Cl
2
in order to obtain a 0.2  solution,
3
solution and
0
.69 mmol) as a mixture of two invertomers maj/min ϭ 65:35;
2
2
trans/cis Ͼ 98:2. IR (NaCl, film): ν˜ ϭ 2980, 2910, 2840, 2160, 835
cm
invertomers: δ ϭ 0.20 (s, 9 H maj), 0.29 (s, 9 H min), 0.86 (m, 3 H),
1
(
1
3
Ϫ1
1
3
. H NMR (CDCl , 400 MHz) for the mixture of the two
centrated in vacuo to afford N-sulfonylimines 4 as white solids in
yields from 54 to 89%.
3
.19Ϫ1.50 (m, 6 H), 1.77 (m, 1 H), 2.38 (d, J ϭ 3.0 Hz, 1 H), 3.43
General Procedure 4. Preparation of N-Benzyl- and N-Sulfonylaziri-
dines 2 and 5 from the Corresponding Imines: Under nitrogen, the
N-benzylimines or the N-sulfonylimines 4 (1.0 equiv.) were added
dropwise at Ϫ60 °C to a solution of allenylzinc compound 1 (1.0
equiv.). The mixture was allowed to warm slowly to room temper-
ature, stirred overnight at this temperature and then quenched with
a 65:35 mixture of a saturated aqueous NH
The aqueous layer was extracted with Et O (twice). The combined
organic layers were washed with water (twice) and brine, dried with
anhydrous MgSO , and then concentrated in vacuo to dryness. The
crude oils were purified by flash chromatography, eluting with 5% (2R*,3R*)-N-Benzyl-3-cyclohexyl-2-[(trimethylsilyl)ethynyl]-
2
2
AB system, J ϭ 13.7 Hz, 1 H min), 3.61 (AB system, J ϭ
2
3.2 Hz, 1 H maj), 3.81 (AB system, J ϭ 13.7 Hz, 1 H min), 3.87
2
13
(
(
0
AB system, J ϭ 13.2 Hz, 1 H maj), 7.26Ϫ7.43 (m, 5 H). C NMR
CDCl , 100.6 MHz) for the mixture of the two invertomers: δ ϭ
.0 (maj), 0.3 (min), 14.0, 22.2 (min), 22.4 (maj), 28.5 (min), 29.2
3
(
(
maj), 29.7 (min), 32.4 (maj), 32.8 (maj), 34.3 (min), 48.7 (maj), 55.6
min), 58.4 (maj), 59.1 (min), 88.8 (maj), 91.6 (min), 101.2 (min),
4 3
Cl solution and NH .
2
1
(
02.7 (maj), 127.0 (maj), 127.3 (min), 128.3 (maj), 128.4 (min), 128.7
maj), 129.1 (min), 138.8 (min), 139.3 (maj).
4
ethyl acetate/cyclohexane, to afford N-benzylaziridines 2 or N-sul-
fonylaziridines 5 as pale yellow oils.
aziridine (2b): This compound was prepared by General Procedure
4, from N-(cyclohexylmethylidene)benzylamine (1.00 g, 5.00 mmol)
in 98% yield (1.52 g, 4.90 mmol). Purification was not necessary;
trans/cis Ͼ 98:2. IR (NaCl, film): ν˜ ϭ 3030, 2920, 2840, 2160, 840
General Procedure 5. Preparation of N-H Aziridines 3: Under nitro-
gen, n-butyllithium (2.5  in hexanes, 1.1 equiv.) was slowly added,
at a temperature below 25 °C, to hexamethyldisilazane (1.1 equiv.).
After the mixture had been stirred for 30 min, the volatiles were
removed in vacuo and the resulting white solid was taken up into
anhydrous THF in order to obtain a 0.5  solution. This was co-
oled to Ϫ55 °C, and the aldehyde (1.0 equiv.) was added dropwise.
The solution was stirred for 2 h at Ϫ40 °C and was cannulated into
Ϫ1
1
3
cm . H NMR (CDCl , 200 MHz): δ ϭ 0.21 (s, 9 H), 0.80Ϫ1.93
3
2
(
m, 12 H), 2.41 (d, J ϭ 3.0 Hz, 1 H), 3.53 (AB system, J ϭ
2
1
5
3
3.1 Hz, 1 H), 3.87 (AB system, J ϭ 13.1 Hz, 1 H), 7.25Ϫ7.40 (m,
H). C NMR (CDCl
1.8, 35.5, 41.0, 53.9, 58.7, 88.6, 102.7, 127.0, 128.3, 128.9, 139.3.
13
3
, 50.3 MHz): δ ϭ 0.0, 25.6, 26.3, 30.0, 30.6,
(2R*,3R*)-N-Benzyl-3-(tert-butyl)-2-[(trimethylsilyl)ethynyl]-
a cooled (Ϫ80 °C) solution of allenylzinc compound 1 (1.0 equiv.). aziridine (2c): N-(2,2-Dimethylpropylidene)benzylamine (870 mg,
The mixture was allowed to warm very slowly (over a period of
5.00 mmol) was added dropwise at Ϫ60 °C, under nitrogen, to a
freshly prepared solution of allenylzinc compound 1 (5.00 mmol)
1
1
8 h) to Ϫ35 °C and then quenched with a 65:35 mixture of a
388
Eur. J. Org. Chem. 2002, 1385Ϫ1391

A Stereoselective Synthesis of Alkynylaziridines
in THF, followed by BF ϪEt
O (0.63 mL, 5.00 mmol). The mixture (2R*,3R*)-N-Benzyl-3-isopropyl-2-[(trimethylsilyl)ethynyl]aziridine
FULL PAPER
3
2
was allowed to warm slowly to room temperature, stirred overnight
at this temperature and then quenched successively with absolute
(2g): This compound was prepared by General Procedure 6, from
N-H aziridine 3g (181 mg, 1.00 mmol) in 66% yield (178 mg,
MeOH (2 mL), Et
tion (25 mL). The aqueous layer was extracted with Et
0 mL), and the combined organic layers were washed with water δ ϭ 0.20 (s, 9 H), 0.82 (d, J ϭ 6.6 Hz, 3 H), 0.95 (d, J ϭ 7.1 Hz,
3 4
N (2 mL), and a saturated aqueous NH
Cl solu- 0.66 mmol); trans/cis Ͼ 98:2. IR (NaCl, film): ν˜ ϭ 3030, 2960,
Ϫ1
1
O (2 ϫ
2910, 2880, 2160, 1605, 835 cm . H NMR (CDCl
3
3
, 400 MHz):
2
3
4
3
3
(
twice) and brine, dried with anhydrous MgSO
trated in vacuo to dryness. The crude oil was purified by flash
chromatography, eluting with 5% ethyl acetate/cyclohexane, to give H), 3.89 (AB system, J ϭ 13.2 Hz, 1 H), 7.33Ϫ7.43 (m, 5 H).
N-benzylaziridine 2c in 12% yield (180 mg, 0.60 mmol) as a pale NMR (CDCl , 100.6 MHz): δ ϭ 0.0, 19.4, 20.0, 31.6, 32.1, 55.1,
yellow oil; trans/cis Ͼ 98:2. IR (NaCl, film): ν˜ ϭ 3030, 2960, 2900, 58.6, 88.6, 102.8, 127.0, 128.3, 128.9, 139.3. MS (E.I., 70 eV): m/z
4
, and then concen- 3 H), 1.26 (oct, J ϭ 7.1 Hz, 1 H), 1.57 (dd, J ϭ 3.1, 8.1 Hz, 1
3
2
H), 2.42 (d, J ϭ 3.1 Hz, 1 H), 3.55 (AB system, J ϭ 13.2 Hz, 1
2
13
C
3
Ϫ1
1
2
9
1
1
870, 2160, 840 cm . H NMR (CDCl
3
, 400 MHz): δ ϭ 0.21 (s,
(%) ϭ 271 (39), 180 (100), 91 (74), 73 (100).
3
3
H), 0.78 (s, 9 H), 1.62 (d, J ϭ 3.6 Hz, 1 H), 2.48 (d, J ϭ 3.6 Hz,
2
2
(2R*,3R*)-N-Benzyl-3-(2-methylprop-1-enyl)-2-[(trimethylsilyl)-
ethynyl]aziridine (2h): This compound was prepared by General
Procedure 6, from N-H aziridine 3h (180 mg, 1.02 mmol) in 67%
yield (182 mg, 0.68 mmol); trans/cis Ͼ 98:2. IR (NaCl, film): ν˜ ϭ
030, 2940, 2880, 2180, 1645, 810 cm
00 MHz): δ ϭ 0.20 (s, 9 H), 1.71 (dd, J ϭ 2.0 Hz and J ϭ 6.6 Hz,
H), 3.53 (AB system, J ϭ 13.2 Hz, 1 H), 3.91 (AB system, J ϭ
3.2 Hz, 1 H), 7.32Ϫ7.44 (m, 5 H). 13C NMR (CDCl
3
, 100.6 MHz):
δ ϭ 0.0, 26.5, 29.2, 30.6, 57.9, 58.7, 88.1, 103.2, 126.9, 128.1, 128.9,
39.6. C18 26NSi (285.50): calcd. C 75.72, H 9.53, N 4.91; found
1
H
Ϫ1
1
3
4
3
3
.
3
H NMR (CDCl ,
C 75.32, H 9.54, N 4.61. This compound was also prepared by
General Procedure 6, from N-H aziridine 3c (see below; 197 mg,
4
3
3
3
H), 2.28 (dd, J ϭ 3.0, 7.6 Hz, 1 H), 2.55 (d, J ϭ 3.0 Hz, 1 H),
.76 (AB system, J ϭ 13.7 Hz, 1 H), 3.87 (AB system, J ϭ
1.01 mmol) in 69% yield (196 mg, 0.69 mmol); trans/cis Ͼ 98:2.
2
2
4
3
(
(
2R*,3R*)-N-Benzyl-3-phenyl-2-[(trimethylsilyl)ethynyl]aziridine 13.7 Hz, 1 H), 5.22 (ddd, J ϭ 2.0, J ϭ 7.6 and 15.3 Hz, 1 H),
2d): This compound was prepared by General Procedure 4, from
3
13
5.82 (dq, J ϭ 7.6 and 15.3 Hz, 1 H), 7.33Ϫ7.44 (m, 5 H).
C
N-benzylidenebenzylamine (975 mg, 5.00 mmol) in 73% yield
NMR (CDCl , 100.6 MHz): δ ϭ 0.0, 18.0, 34.1, 49.6, 57.9, 88.6,
3
(
1.12 g, 3.65 mmol); trans/cis Ͼ 98:2. IR (NaCl, film): ν˜ ϭ 3030, 101.8, 127.0, 128.3, 128.4, 129.2, 129.3, 139.2. C H NSi (269.46):
17 23
Ϫ1
1
2
4
950, 2910, 2840, 2160, 1600, 840 cm
.
H NMR (CDCl
3
,
calcd. C 75.78, H 8.60, N 5.20; found C 76.09, H 8.72, N 4.65.
3
00 MHz): δ ϭ 0.21 (s, 9 H), 2.66 (d, J ϭ 3.0 Hz, 1 H), 2.81 (d,
3
2
(2R*,3R*)-3-(n-Butyl)-2-[(trimethysilyl)ethynyl]aziridine (3a): n-Bu-
tyllithium (2.5  in hexanes, 2.00 mL, 5.00 mmol) was added drop-
wise at Ϫ80 °C, under nitrogen, to a stirred solution of bis(trime-
thylsilyl)formamide (1.08 mL, 5.00 mmol). The solution was stirred
for 2 h at Ϫ80 °C and was cannulated into a cooled (Ϫ80 °C) solu-
tion of allenylzinc compound 1 (5.00 mmol). The mixture was al-
lowed to warm very slowly (over a period of 18 h) to Ϫ35 °C and
J ϭ 3.0 Hz, 1 H), 3.90 (AB system, J ϭ 13.9 Hz, 1 H), 4.06 (AB
system, 2J ϭ 13.9 Hz, 1 H), 7.26Ϫ7.46 (m, 10 H). 13C NMR
(CDCl
3
, 100.6 MHz): δ ϭ 0.0, 37.0, 49.9, 58.1, 89.6, 101.6, 126.3,
27.6, 128.0, 139.2. This compound was also prepared by General
1
Procedure 6, from N-H aziridine 3d (see below; 211 mg, 0.98 mmol)
in 90% yield (270 mg, 0.88 mmol); trans/cis Ͼ 98:2.
(
2R*,3R*)-N-Benzyl-3-(2-phenylethenyl)-2-[(trimethylsilyl)ethynyl]-
aziridine (2e): This compound was prepared by General Procedure
then quenched with a 65:35 mixture of a saturated aqueous NH
solution and NH (25 mL). After the mixture had been allowed to
warm to room temperature, the aqueous layer was extracted with
Et O (3 ϫ 25 mL). The combined organic layers were washed with
a saturated aqueous NaHCO solution, water (twice) and brine,
dried with anhydrous Na SO , and then concentrated to dryness in
vacuo. The crude brownish oil was purified by flash chromato-
graphy, eluting with 8% Et O/2% Et N/pentane, to give aziridine
a in 63% yield (614 mg, 3.15 mmol) as a mixture of two
invertomers. Yellow oil. IR (NaCl, film): ν˜ ϭ 3320, 2950, 2880,
4
Cl
3
4,
from
N-(3-phenylprop-2-enylidene)benzylamine
(1.10 g,
4.98 mmol) in 65% yield (1.08 g, 3.26 mmol); trans/cis Ͼ 98:2. IR
2
Ϫ1
(
NaCl, film): ν˜ ϭ 3030, 2970, 2910, 2860, 2160, 1600, 840 cm
.
3
1
3
H NMR (CDCl
3
, 400 MHz): δ ϭ 0.21 (s, 9 H), 2.50 (dd, J ϭ 2.8,
2
4
3
2
7
1
7
1
9
.6 Hz, 1 H), 2.72 (d, J ϭ 2.8 Hz, 1 H), 3.83 (AB system, J ϭ
2
3
3.7 Hz, 1 H), 3.96 (AB system, J ϭ 13.7 Hz, 1 H), 6.00 (dd, J ϭ
2
3
3
.6 and 16.0 Hz, 1 H), 6.71 (d, J ϭ 16.0 Hz, 1 H), 7.21Ϫ7.50 (m,
3
0 H). 13C NMR (CDCl
, 100.6 MHz): δ ϭ 0.0, 35.1, 49.9, 57.9,
0.2, 101.4, 126.3, 128.6, 132.6, 136.6, 139.0. MS (E.I., 70 eV):
3
Ϫ1
1
2
3
160, 1450, 835 cm . H NMR (CDCl , 400 MHz) for the mixture
m/z (%) ϭ 331 (29), 106 (59), 91 (100), 73 (96). This compound
was also prepared by General Procedure 6, from N-H aziridine 3e
3
of the two invertomers: δ ϭ 0.17 (s, 9 H), 0.92 (t, J ϭ 7.1 Hz, 3
H), 1.36Ϫ1.45 (m, 6 H), 1.70 (m, 1 H), 2.05 (m, 1 H), 2.27 (m,
(see below; 242 mg, 1.00 mmol) in 66% yield (216 mg, 0.66 mmol);
13
1
3
H). C NMR (CDCl , 100.6 MHz) for the mixture of the two
trans/cis Ͼ 98:2.
invertomers: δ ϭ 0.0, 14.1, 22.5, 25.5, 29.3, 32.7 (broad), 40.6, 84.7,
06.1. C11 21NSi (195.38): calcd. C 67.62, H 10.83, N 7.17; found
C 68.10, H 10.94, N 6.65.
1
H
N-Benzyl-2-[(trimethylsilyl)ethynyl]-1-azaspiro[2.5]octane (2f): This
compound was prepared by General Procedure 4, from N-cyclohex-
ylidenebenzylamine (0.93 g, 5.00 mmol) in 40% yield (1.00 g,
(
2R*,3R*)-3-(tert-Butyl)-2-[(trimethysilyl)ethynyl]aziridine
(3c):
2
.00 mmol), as a mixture of two invertomers in a 50:50 ratio;
This compound was prepared by General Procedure 5, from pival-
aldehyde (0.53 mL, 4.90 mmol) in 40% yield (374 mg, 1.92 mmol)
after stirring for 16 h at Ϫ10 °C as a single invertomer. IR (NaCl,
trans/cis Ͼ 98:2. IR (NaCl, film): ν˜ ϭ 3030, 2950, 2920, 2840, 2160,
8
Ϫ1
1
3
40 cm . H NMR (CDCl , 200 MHz) for the mixture of the two
invertomers: δ ϭ 0.19 (s, 9 H for one invertomer), 0.23 (s, 9 H for
one invertomer), 0.77Ϫ0.87 (m, 10 H), 1.90 (s, 1 H for one
invertomer), 2.40 (s, 1 H for one invertomer), 3.69 (AB system,
Ϫ1 1
film): ν˜ ϭ 3330, 2950, 2880, 2165, 840 cm . H NMR (CDCl
3
,
4
2
4
7
00 MHz): δ ϭ 0.17 (s, 9 H), 0.90 (s, 9 H), 1.70 (m, 1 H), 2.17 (m,
H). C NMR (CDCl , 100.6 MHz): δ ϭ 0.0, 22.2, 26.5, 30.7,
3
9.6, 84.3, 106.5. MS (E.I., 70 eV): m/z (%) ϭ 195 (43), 180 (86),
3 (53), 57 (33).
13
2
2
J ϭ 14.1 Hz, 1 H for one invertomer), 3.70 (AB system, J ϭ
2
1
1
4.6 Hz, 1 H for one invertomer), 3.84 (AB system, J ϭ 14.1 Hz,
2
H for one invertomer), 3.86 (AB system, J ϭ 14.6 Hz, 1 H for
13
one invertomer), 7.17Ϫ7.41 (5 H). C NMR (CDCl
for the mixture of the two invertomers: δ ϭ 0.0, 24.6, 39.3, 47.1, compound was prepared by General Procedure 5, from benzal-
7.7, 48.7, 49.9, 86.3, 90.2, 101.6, 104.1, 126.5, 128.2, 139.5, 140.1. dehyde (522 mg, 4.92 mmol) in 62% yield (649 mg, 3.02 mmol) as
3
, 50.3 MHz)
(2R*,3R*)-3-Phenyl-2-[(trimethysilyl)ethynyl]aziridine (3d): This
4
Eur. J. Org. Chem. 2002, 1385Ϫ1391
1389

F. Chemla, F. Ferreira, V. Hebbe, E. Stercklen
25NSiSO (335.54): calcd. C 60.85, H 7.51, N
FULL PAPER
a mixture of two invertomers maj/min ϭ 95:5; trans/cis Ͼ 98:2. IR 139.1, 144.5. C17
H
2
Ϫ1
1
(
NaCl, film): ν˜ ϭ 3320, 3030, 2930, 2160, 1580, 830 cm
.
H
4.17; found C 61.16, H 7.84, N 3.95.
3
NMR (CDCl , 400 MHz) for the mixture of the two invertomers:
3
(2R*,3R*)-3-Isopropyl-N-(4-methylphenyl)sulfonyl-2-[(trimethyl-
silyl)ethynyl]aziridine (5b): This compound was prepared by Gen-
eral Procedure 4, from 4-methylbenzenesulfonamide 4b (1.13 g,
δ ϭ 0.20 (s, 9 H), 1.62 (s, 1 H), 2.32 (dd, J ϭ 2.5, 8.1 Hz, 1 H
3
maj), 2.75 (m, 1 H min), 3.16 (m, 1 H min), 3.36 (dd, J ϭ 2.5,
.1 Hz, 1 H maj), 7.28 (m, 5 H). 1 C NMR (CDCl
3
7
3
, 100.6 MHz)
5
.02 mmol) in 27% yield (0.45 g, 1.34 mmol) after flash chromato-
for the mixture of the two invertomers: δ ϭ 0.0, 30.2, 41.4, 85.6,
graphy, eluting with 20% ethyl acetate/cyclohexane; trans/cis ϭ
105.2, 126.0, 127.7, 128.5, 138.3. C13
H17NSi (215.37): calcd. C
Ϫ1
1
7
0:30. IR (NaCl, film): ν˜ ϭ 2920, 2190, 1600, 800 cm . H NMR
72.50, H 7.96, N 6.50; found C 72.57, H 8.10, N 6.34.
(
CDCl , 400 MHz): δ ϭ 0.12 (s, 9 H cis), 0.34 (s, 9 H trans), 0.68
3
3
3
(
(
(
2R*,3R*)-3-(2-Phenylethenyl)-2-[(trimethysilyl)ethynyl]aziridine (d, J ϭ 6.9 Hz, 3 H trans), 0.72 (d, J ϭ 6.9 Hz, 3 H trans), 0.93
3
3
3e): This compound was prepared by General Procedure 5, from (d, J ϭ 6.9 Hz, 3 H cis), 0.97 (d, J ϭ 6.9 Hz, 3 H cis), 1.21 (m,
E)-cinnamaldehyde (0.62 mL, 4.90 mmol) in 65% yield (784 mg, 1 H trans), 1.45 (m, 1 H cis), 1.87 (s, 3 H cis), 1.94 (s, 3 H trans),
.25 mmol) as a mixture of two invertomers maj/min ϭ 73:27. IR
3
3
3
2.68 (dd, J ϭ 6.8, 9.6 Hz, 1 H cis), 2.96 (d, J ϭ 4.3 Hz, 1 H trans),
Ϫ1
1
3
3
(
NaCl, film): ν˜ ϭ 3315, 3080, 2940, 2165, 1580, 840 cm
.
H
3.16 (dd, J ϭ 4.3, 7.8 Hz, 1 H trans), 3.58 (d, J ϭ 6.8 Hz, 1 H
3
3
3
NMR (CDCl , 400 MHz) for the mixture of the two invertomers: cis), 6.76 (d, J ϭ 8.3 Hz, 2 H cis), 6.88 (d, J ϭ 8.1 Hz, 2 H trans),
δ ϭ 0.20 (s, 9 H), 0.89 (m, 1 H min), 1.05 (s, 1 H maj), 2.33 (dl, 7.94 (d, J ϭ 8.3 Hz, 2 H cis), 8.15 (d, J ϭ 8.1 Hz, 2 H trans).
3
3
13
C
3
J ϭ 6.1 Hz, 1 H maj), 2.60 (m, 1 H min), 2.83 (m, 1 H min), 3.01 NMR (CDCl
3
, 100.6 MHz): δ ϭ Ϫ0.1 (cis), 0.0 (trans), 18.7 (cis),
3
3
(t, J ϭ 7.1 Hz, 1 H maj), 5.65 (m, 1 H min), 5.86 (dd, J ϭ 7.7 19.2 (trans), 19.7 (trans), 20.6 (cis), 21.4 (trans), 29.2 (cis), 30.6,
3
and 15.8 Hz, 1 H maj), 6.73 (d, J ϭ 15.8 Hz, 1 H), 7.32Ϫ7.36 (m,
H). 13C NMR (CDCl
, 100.6 MHz) for the mixture of the two
invertomers: δ ϭ 0.0, 28.8, 41.5 (broad), 86.0, 104.7, 126.3, 127.9,
51.2, 54.0, 92.5, 99.7, 128.1, 129.7, 138.0, 144.2.
2S*,3S*)-3-Phenyl-N-(phenylsulfonyl)-2-[(trimethylsilyl)ethynyl]-
5
3
(
aziridine (5c): This compound was prepared by General Procedure
, from benzenesulfonamide 4c (1.22 g, 4.98 mmol) in 41% yield
0.72 g, 2.03 mmol) after flash chromatography, eluting with 10%
ethyl acetate/cyclohexane; trans/cis ϭ 10:90. IR (NaCl, film): ν˜ ϭ
128.7, 132.8, 136.4. C15H19NSi (241.40): calcd. C 74.63, H 7.93, N
4
(
5.80; found C 74.47, H 7.91, N 5.58.
(
2R*,3R*)-3-Isopropyl-2-[(trimethysilyl)ethynyl]aziridine (3g): This
compound was prepared by General Procedure 5, from isobutyral-
dehyde (0.45 mL, 4.90 mmol) in 69% yield (614 mg, 3.38 mmol) as δ ϭ Ϫ0.1 (s, 9 H cis), 0.01 (s, 9 H trans), 3.20 (d, J ϭ 4.1 Hz, 1 H
Ϫ1
1
3
3030, 2180, 1590, 1450, 800 cm . H NMR (CDCl , 400 MHz):
3
3
3
a mixture of two invertomers maj/min ϭ 89:11. IR (NaCl, film):
trans), 3.71 (d, J ϭ 7.0 Hz, 1 H cis), 4.02 (d, J ϭ 7.0 Hz, 1 H cis),
Ϫ1
1
3
13
ν˜ ϭ 3320, 2950, 2920, 2170, 840 cm
.
H NMR (CDCl
3
,
4.22 (d, J ϭ 4.1 Hz, 1 H trans), 7.28Ϫ8.04 (m, 10 H). C NMR
(CDCl , 50.3 MHz): δ ϭ 0.0 (cis), 0.29 (trans), 46.4, 51.2, 65.8,
91.6, 97.2, 127.9, 129.2, 131.7, 133.9.
4
00 MHz) for the mixture of the two invertomers: δ ϭ 0.17 (s, 9
3
1
3
H), 1.02 (m, 6 H), 1.18 (m, 1 H), 1.73 (m, 1 H), 2.09 (m, 2 H).
C
NMR (CDCl
3
, 100.6 MHz) for the mixture of the two invertomers:
(
2R*,3R*)-N-[2-Chloro-1-phenyl-4-(trimethylsilyl)but-3-enyl]-
benzenesulfonamide (6): Under nitrogen, a solution of sulfonylimine
c (1.22 g, 4.98 mmol) in anhydrous THF (5 mL) was added drop-
wise at Ϫ60 °C to a solution of allenylzinc compound 1
δ ϭ Ϫ0.2 (min), 0.0 (maj), 17.7 (min), 19.7 (min), 20.0 (maj), 24.7
(
(
maj), 31.0 (min), 31.9 (maj), 46.9 (maj), 52.3 (min), 79.2 (min), 84.6
maj), 99.8 (min), 106.2 (maj).
4
(
2R*,3R*)-3-(2-Methylprop-1-enyl)-2-[(trimethysilyl)ethynyl]- (5.00 mmol). After stirring for 6 h at Ϫ60 °C, the solution was
quenched with a saturated aqueous NH Cl solution and the aque-
ous layer was extracted with Et O (2 ϫ 25 mL). The combined
organic layers were washed with water (twice) and brine, dried with
anhydrous MgSO and then concentrated in vacuo to dryness. The
crude product was dissolved in CH Cl to precipitate remaining
aziridine (3h): This compound was prepared by General Procedure
, from crotonaldehyde (0.41 mL, 4.90 mmol) in 79% yield
691 mg, 3.86 mmol) as a mixture of two invertomers maj/min ϭ
4
5
(
2
Ϫ1
6
6:34. IR (NaCl, film): ν˜ ϭ 3320, 2950, 2880, 2180, 1640, 840 cm
.
4
1
H
NMR (CDCl
3
,
400 MHz) for the mixture of the two
2
2
invertomers: δ ϭ 0.15 (s, 9 H), 0.65 (m, 1 H min), 0.86 (m, 1 H sulfonylimine 4c. Filtration and removal of the solvent afforded
3
maj), 1.68 (d, J ϭ 5.6 Hz, 3 H), 2.16 (m, 1 H maj), 2.38 (m, 1 H starting sulfonylimine 4c in 76% yield (0.92 g, 3.76 mmol) as a
min), 2.58 (m, 1 H min), 2.76 (m, 1 H maj), 4.98Ϫ5.08 (m, 1 H), white solid and chloroamine 6 in 11% yield (0.21 g, 0.54) as a yel-
1
5
.81 (m, 1 H). 13C NMR (CDCl
3
, 100.6 MHz) for the mixture of low oil; anti/syn ϭ 10:90. H NMR (C
6
D
6
/TMS, 400 MHz): δ ϭ
3
the two invertomers: δ ϭ 0.0, 17.9, 27.3, 40.9 (maj), 42.1 (min), 0.09 (s, 9 H anti), 0.18 (s, 9 H syn), 4.65 (d, J ϭ 5.5 Hz, 1 H syn),
3
4
6.9 (maj), 79.2 (min), 85.0 (min), 85.6 (maj), 104.6 (min), 105.3
4.70 (d, J ϭ 4.2 Hz, 1 H anti), 4.98 (m, 1 H), 5.60 (m, 1 H syn),
1
3
(maj), 129.4.
5.83 (m, 1 H anti), 6.84Ϫ7.78 (m, 10 H). C NMR (CDCl
0.3 MHz): δ ϭ 0.0, 52.4 (syn), 53.0 (anti), 62.3, 95.7 (syn), 96.6
anti), 98.7 (anti), 99.5 (syn), 127.5, 128.4, 128.6, 129.1, 129.4,
33.1, 135.9, 140.5.
3
,
5
(
1
(
2R*,3R*)-3-Cyclohexyl-N-(4-methylphenyl)sulfonyl-2-[(trimethyl-
silyl)ethynyl]aziridine (5a): This compound was prepared by Gen-
eral Procedure 4, from N-(4-methylphenyl)sulfonamide 4a (1.33 g,
5.02 mmol) in 39% yield (0.74 g, 1.97 mmol) after flash chromato-
(2R*,3S*)-2-Ethynyl-3-phenyl-N-(phenylsulfonyl)aziridine (7):
A
graphy, eluting with 20% ethyl acetate/cyclohexane; trans/cis ϭ suspension of chloroamine 6 (200 mg, 0.51 mmol) and KF (42 mg,
Ϫ1
1
7
0:30. IR (NaCl, film): ν˜ ϭ 2930, 2860, 2180, 1600, 810 cm . H 0.72 mmol) in a 50:50 DMF/water mixture (20 mL) was stirred
NMR (CDCl , 400 MHz): δ ϭ 0.13 (s, 9 H cis), 0.33 (s, 9 H trans), overnight at room temperature and then quenched with 1.0  HCl.
.80Ϫ1.80 (m, 11 H), 1.86 (s, 3 H cis), 1.93 (s, 3 H trans), 2.80 (dd, The aqueous layer was extracted with Et O (2 ϫ 40 mL) and the
J ϭ 6.8, 9.6 Hz, 1 H cis), 2.90 (d, J ϭ 4.3 Hz, 1 H trans), 3.21 combined organic layers were treated with 10% aqueous NaOH
3
0
2
3
3
3
3
(
6
(
dd, J ϭ 4.3, 7.4 Hz, 1 H trans), 3.57 (d, J ϭ 6.8 Hz, 1 H cis),
with stirring for 1 h. The aqueous layer was then extracted with
Et O (1 ϫ 40 mL) washed with brine, dried with anhydrous
, and concentrated in vacuo to give N-(phenylsulfonyl)aziri-
, 100.6 MHz): δ ϭ 0.0, 21.4, 25.8 (cis), 25.9, 26.33 (trans), dine in 69% yield (100 mg, 0.35 mmol) as a yellow oil; trans/cis ϭ
3
3
.75 (d, J ϭ 8.3 Hz, 2 H cis), 6.90 (d, J ϭ 8.2 Hz, 2 H trans), 7.95
2
3
3
13
d, J ϭ 8.3 Hz, 2 H cis) 8.20 (d, J ϭ 8.2 Hz, 2 H trans). C NMR MgSO
CDCl
4
(
2
3
Ϫ1
9.7 (cis), 30.4 (trans), 39.6, 50.1, 52.9, 92.5, 101.2, 128.1, 129.7, 10:90. IR (NaCl, film): ν˜ ϭ 3280, 3030, 2920, 2120, 1580, 730 cm
.
1390 Eur. J. Org. Chem. 2002, 1385Ϫ1391

A Stereoselective Synthesis of Alkynylaziridines
FULL PAPER
F. Chemla, V. Hebbe, J. F. Normant, Tetrahedron Lett. 1999,
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and α-Acetylenic Carbanions’’, in: Comprehensive Carbanion
Chemistry (Eds. E. Buncel, T. Durst), Elsevier, Amsterdam,
1
4
[18]
H NMR (CDCl
3
, 400 MHz): δ ϭ 2.10 (d, J ϭ 2.1 Hz, 1 H cis),
4
4
3
2
4
.65 (d, J ϭ 2.1 Hz, 1 H trans), 3.22 (dd, J ϭ 2.1 Hz, and J ϭ
.1 Hz, 1 H trans), 3.70 (dd, J ϭ 2.1 Hz, and J ϭ 7.0 Hz, 1 H
[19]
4
3
3
3
cis), 4.05 (d, J ϭ 7.0 Hz, 1 H cis), 4.20 (d, J ϭ 4.1 Hz, 1 H trans),
7
3
.19Ϫ8.00 (m, 10 H). 13C NMR (CDCl
7.9, 46.3, 48.9, 74.2, 76.2, 128.1, 129.7, 134.4, 137.9.
3
, 50.3 MHz): δ ϭ 35.8,
1
984, vol. B, pp. 107Ϫ175.
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