The synthesis of 2-trialkyIsilylaziridines from vinyltrialkylsilanes or the reaction of α-chloro-α-silyl carbanions with imines

Article abstract of DOI:10.1039/a905182a

Three methods have been employed in the synthesis of 2-trialkylsilylaziridines. Firstly, reacting α-chloroa-silyl carbanions with imines. Secondly, from the corresponding vinylsilane, via addition of bromoazide to give the l-bromo-2-azide, followed by red

Full text of DOI:10.1039/a905182a

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The synthesis of 2-trialkylsilylaziridines from vinyltrialkylsilanes
or the reaction of ꢀ-chloro-ꢀ-silyl carbanions with imines
Alan R. Bassindale,* Patricia A. Kyle, Marie-Claire Soobramanien and Peter G. Taylor*
The Chemistry Department, The Open University, Walton Hall, Milton Keynes, UK MK7 6AA
Received 28th June 1999, Accepted 3rd February 2000
1
Three methods have been employed in the synthesis of 2-trialkylsilylaziridines. Firstly, reacting α-chloro-
α-silyl carbanions with imines. Secondly, from the corresponding vinylsilane, via addition of bromoazide to
give the 1-bromo-2-azide, followed by reduction. Finally, by the addition of organoazides to vinylsilanes using
thermochemical and photochemical conditions. Using these three strategies a range of substitution patterns
have been achieved.
Introduction
2-Trialkylsilylepoxides are important synthetic intermediates
undergoing regiospecific and stereospecific transformations
to give vinyl halides,1 enol ethers2 and carbonyl compounds.3
Although much is known of the chemistry of 2-trialkyl-
silylepoexides, little is known of their 2-trialkylsilylaziridine
counterparts. We were interested in investigating the synthetic
versatility of these corresponding 2-trialkylsilylaziridines and in
Scheme 1
particular their ring opening reactions with electrophilic and
nucleophilic reagents. To achieve this, it was necessary to syn-
thesise 2-trialkylsilylaziridines, 1, with a range of substituents,
including hydrogen, on the ring nitrogen and ring carbons.
Despite the various 2-trialkylsilylaziridines that have been
made, it was necessary to reexamine existing methodologies and
develop new strategies, in order to generate a wide range of
2-trialkylsilylaziridines and hence enable us to examine method-
ically the effect of structure on the reactivity of these species.
Results and discussion
The synthesis of silylaziridines from imines
Cooke and Magnus have devised a route to α,β-epoxysilanes
based on the reaction of a carbonyl compound with the α-silyl
carbanion derived from α-chloromethyltrimethylsilane.12 We
have developed this reaction further to give silylaziridines from
the corresponding azomethines, as shown in Scheme 2.
In a typical procedure the α-silyl carbanion, 2, was formed
by the reaction of α-chloromethyltrimethylsilane in freshly dis-
tilled tetrahydrofuran with a solution of sec-butyllithium–
TMEDA in cyclohexane at Ϫ78 ЊC. The resultant carbanion
was treated with a solution of an azomethine in tetra-
hydrofuran at about Ϫ65 ЊC. The mixture was allowed to
stand for two hours at Ϫ50 ЊC, then quenched with aqueous
ammonium chloride at room temperature and worked up as
The first silicon containing aziridines were synthesised in
1964 by Adrianov et al.4 by the thermal reaction of arylazides
with vinylsilanes. This provides an effective route to 1-aryl-2-
trialkylsilylaziridines,5 but cannot be used to produce the
corresponding 1-alkylaziridines. Zanirato and co-workers have
used a similar methodology to prepare N-heteroaryltrimethyl-
silylaziridines.6 With these thermochemical reactions the azide
undergoes a 1,3-dipolar cycloaddition with the vinylsilane to
give the intermediate triazolines which then lose nitrogen to
give the corresponding 2-trialkylsilylaziridine. Addition of
nitrenes to alkenes has also been used extensively to make azirid-
ines. Lukevics et al. have generated nitrenes by α-elimination
of carbamates and reacted them with vinylsilanes to produce
1-ethoxycarbonyl-2-trialkylsilylaziridines.7 Atkinson and co-
workers have developed a high yielding and stereoselective
route to 2-trialkylsilylaziridines via a nitrene-like intermediate.8
Reaction of acetoxyaminoquinazolone with lead tetraacetate
(LTA) in the presence of alkenes leads to aziridines in good
yield, as shown in Scheme 1. The introduction of a chiral centre
at the 2 position of the quinazoline ring leads to asymmetric
induction in the aziridination of prochiral trialkylsilylalkenes
giving a ratio of diastereoisomers of 11:1.
2-Trialkylsilylaziridines have also been produced from
alkenes via the formation of 1-halo-2-amines.9–11 The stereo-
chemistry of the product is determined by that of the 1-halo-2-
amine which in turn is controlled by the manner in which the
reagent adds to the alkene.
Scheme 2
DOI: 10.1039/a905182a
J. Chem. Soc., Perkin Trans. 1, 2000, 1173–1180
This journal is © The Royal Society of Chemistry 2000
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Table 1 Yields of 2-trimethylsilylaziridines obtained via bromoazide addition
Reducing
agent
Overall
yield (%)
Alkene
Procedure
B
Aziridine
LiAlH4
3
33
A
B
LiAlH4
PPh3
4
5
6
66
54
51
A
LiAlH4
normal. N-Benzylidenepropylamine gave stereoselectively the
cis-1-propyl-2-trimethylsilyl-3-phenylaziridine in 53% yield.
N-Benzylideneaniline gave the corresponding aziridine in 77%
yield. However, rather than isolating only the cis compound a
1:1 mixture of cis- and trans-isomers was obtained which could
be separated using column chromatography although the
E-isomer did undergo some decomposition on the column.
Extension of this reaction to azomethines from ketones was
unsuccessful, as has been reported for the corresponding
epoxide synthesis of Cooke and Magnus. Reaction of the α-silyl
carbanion with N-(1-phenylethylidene)propylamine gave no
aziridine, but 1-phenyl-3-trimethylsilylpropan-1-one in 30%
yield. This β-trimethylsilyl ketone was presumably obtained via
deprotonation of the azomethine methyl group to give a metal-
loenamine which undergoes alkylation by the α-chloromethyl-
trimethylsilane. Unfortunately N-alkylidenealkylamines also
failed to give aziridines by this route. The NMR spectrum of
the reaction mixture obtained with N-hexylidenepropylamine
again suggested metalloenamine formation rather than addi-
tion of the carbanion.
usually explained in terms of a nucleophilic attack of the bro-
monium ion or stereospecific nucleophilic attack on the carbo-
cation resulting from ring opening. Applying these arguments
to our system suggests that the first step involves formation of
an intermediate bromonium ion, as shown in Scheme 3
(together with the corresponding enantiomer).14
Nucleophilic ring opening in a Markownikov fashion, that is
β to silicon and α to phenyl, gives the RR and SS product, 7.
Reduction of the azide function to an amine using lithium
aluminium hydride, followed by ring closure, then gives the
trans-aziridine. The cis-aziridine is formed via reduction and
cyclisation, from the (RS)- and (SR)-bromoazide, 9. This is
formed from attack of the azide ion, not on the cyclic bromo-
nium ion, but on the free carbocation, 8. Ring opening of the
bromonium ion followed by least motion rotation, so that the
carbon–silicon bond is in line with the empty p orbital, gives 8.
This is then attacked by the azide ion from the least hindered
side, that opposite the bulky trimethylsilyl group, to give the
(RS)- and (SR)-bromoazide.
If such a rationale applies to the change in stereochemistry
observed in our system, it implies that nucleophilic attack occurs
on a bromonium ion with bromoazide formed from N-bromo-
succinimide in 1,4-dioxane and on an open chain carbocation
species with bromoazide formed from bromine in dichloro-
methane. Why a particular intermediate predominates under
one set of conditions is hard to understand and would require
a detailed analysis of the reaction mixtures from a wide
range of vinylsilanes, including the Z-isomers. Nevertheless, the
literature suggests that such a change is by no means without
precedent. For example, Chan and Kaumaglo observed a simi-
lar change in stereochemistry on addition of a Lewis acid in
their ‘tuneable’ stereoselective alkene synthesis based on iodo-
silylation of vinylsilanes.15 Interestingly, the other alkenes
which were examined gave exclusively the trans-aziridines, aris-
ing from bromonium ion formation, irrespective of the condi-
tions employed. In these cases there was not an adjacent phenyl
group to stabilise the open chain carbocation so the alternative
route was not viable.
Synthesis of silylaziridines via the addition of bromoazide to
vinylsilanes
To provide a route to N-unsubstituted silylaziridines we
examined the reaction between bromoazide and vinylsilanes.
Duboudin and Laporte first used this route11 and we have been
able to extend it to provide a wider range of compounds. In
particular we found that by altering the conditions it was pos-
sible to make either the cis- or trans-aziridine from the same
alkene. The results are shown in Table 1. Starting with (E)-2-
trimethylsilyl-1-phenylethene we have been able to obtain in
good yields cis-2-trimethylsilyl-2-phenylaziridine using bromo-
azide prepared in situ from bromine and sodium azide in a
mixture of dichloromethane and aqueous hydrochloric acid
(Procedure A). The corresponding trans-2-trimethylsilyl-1-
phenylaziridine is produced using N-bromosuccinimide and
sodium azide in aqueous 1,4-dioxane (Procedure B). The
stereochemistry of the aziridines was determined from their
characteristic ring proton coupling constants.
Reduction of the 1-bromo-2-azide to the 1-bromo-2-amine
followed by cyclisation did not always occur readily with
lithium aluminium hydride. In particular, 2-azido-1-bromo-1-
trimethylsilylhexane proved difficult to reduce. Lithium
aluminium hydride reduced the 1-bromo-2-azide to 2-amino-1-
Addition/elimination reactions of vinylsilanes can proceed
with either retention or inversion depending upon the condi-
tions and substrate structure.13 This difference of behaviour is
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Scheme 3
trimethylsilylhexane. K-Selectride led to the aziridine, but it was
difficult to remove the tri-sec-butylboron group which became
attached to the aziridine nitrogen. A range of hydrogenation
catalysts and solvents were examined, but in general the
outcome was the elimination of trimethylsilyl azide. For this
substrate the most effective reagent was triphenylphosphine.
Presumably an intermediate N-(triphenylphosphonio)aziridine
is formed which is then hydrolysed to triphenylphosphine oxide
and the free aziridine.
Scheme 5
vinylsilanes. Presumably, the presence of the ester group on the
ring carbon facilitated the loss of nitrogen. In none of the cases
was any enamine detected, as has been reported elsewhere.5
Methyl 2-triethylsilylpropenoate was prepared by the hydro-
silylation of methyl propynoate. The literature reports chloro-
platinic acid can be used to give a 70% yield of the product with
30% of the vicinal regioisomer.17 We found that with this
catalyst 70% of the vicinal isomer was obtained and only 30%
of the desired compound. However, use of 10% platinum on
carbon gave 70% of the geminal regioisomer. The two isomers
could be separated by column chromatography, but in most
cases a partially purified mixture of regioisomers was used since
addition of the phenyl azides only takes place with the geminal
compound. Hydrosilylation with dimethylphenylsilane and
platinum on carbon again gave mainly the geminal isomer,
which again reacts selectively with phenyl azide. However,
whilst reaction of methyl propynoate with diphenylmethyl-
silane gave predominantly the geminal isomer, in this case both
regioisomers underwent addition with phenyl azide, such that
isolation of the required aziridine was not possible.
Synthesis of silylaziridines by the reaction of organoazides with
vinylsilanes
The addition of an organoazide to an alkene has been used
extensively to make aziridines and the method has been applied
to the synthesis of 1-trimethylsilylaziridines. The reaction can
occur both photochemically or thermally. Photochemical addi-
tion of organoazides is thought to involve formation of a
nitrene. Table 2 gives the range of 2-trimethylsilylaziridines we
have prepared photochemically. The reactions were carried out
in the absence of solvent and were generally complete within
two to four days. In all cases retention of the configuration was
observed, suggesting reaction via the singlet nitrene.16 The
1-ethoxycarbonyl-2-trimethylsilylaziridines can be further func-
tionalised to give other 2-trimethylsilylaziridines. For example,
reduction with lithium aluminium hydride does not lead to ring
opening but to loss of the ethoxycarbonyl group to give the NH
aziridine, as shown in Scheme 4. This has provided an altern-
ative route to trans-3-butyl-2-trimethylsilylaziridine.
Our initial objective for this work was to devise routes to
2-trialkylsilylaziridines, 1, with a range of substituents, includ-
ing hydrogen, on the ring nitrogen and carbons. The various
approaches outlined in this paper provide routes to most of the
possible aziridine types. 1-Alkyl-2-trialkylsilylaziridines are best
prepared by reaction of an α-chloro-α-silyl carbanion with an
imine. Whilst 1-alkyl-3-aryl-2-trialkylsilylaziridines are readily
obtained, the corresponding 3-alkyl or disubstituted com-
pounds could not be prepared. A possible alternative route to
this type of compound is via the cyclic sulfate.18 These are pre-
pared by dihydroxylation of the alkene followed by treatment
with thionyl chloride and NaIO4–RuCl3.19 Reaction with an
appropriate amine, followed by treatment with butyllithium
leads to the corresponding aziridine. However, we have found
that this route is limited by the stability of the 1-trialkylsilyl
cyclic sulfate to the reaction conditions for its preparation and
we have been unable to extend it to alkyl substituted alkenes.
An alternative method of preparing the cyclic sulfate is via reac-
tion of phenyl iodosulfate with the vinylsilane and we shall be
investigating this route to 2-trimethylsilylaziridines in the
future.20 1-Aryl-2-trialkylsilylaziridines are best prepared by
the addition of aryl or heteroaryl azides to vinylsilanes via a
thermal route. They can also be formed by reaction of an
α-chloro-α-silyl carbanion with an N-arylimine. Aziridines con-
Scheme 4
Organoazides may also generate nitrenes by a thermal reac-
tion, however, we have observed that this thermal decom-
position often occurs at temperatures greater than is required
for the thermal addition of phenyl azide to alkenes, which has
been shown to give the corresponding aziridine via the triazo-
line, as shown in Scheme 5.5,6
We re-examined the addition of phenyl azide and found that
with trimethylsilylethene the highest yield was obtained when
no solvent was employed. As shown in Tables 2 and 3, the
thermal route to 1-phenyl-2-trimethylsilylaziridine leads to a
higher yield than the photochemical route. If the reactions
involving trimethylvinylsilane were stopped part way through,
it was found that most of the reactant had disappeared and the
solution contained mainly the intermediate triazoline. However,
the intermediate triazoline could not be observed with the other
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Table 2 Yields of 2-trimethylsilylaziridines prepared by the photochemical addition of organoazides to vinylsilanes
Organoazide Alkene Aziridine
Yield (%)
10
11
12
64
60
25
13
14
15
53
29
50
taining an electron withdrawing group attached to the nitrogen
can be prepared via photolysis of the corresponding organo-
azide. 2-Trialkylsilylaziridines without a substituent on the
nitrogen can be formed via a number of routes. Addition of
bromoazide to the alkene gives the 1-bromo-2-azide which
can be reduced to the alkene, however, we have found this
latter stage to be temperamental. An alternative route is via
reduction of the N-alkoxycarbonylaziridine, which is prepared
by photolysis of the alkyl azidoformates in the presence of the
vinylsilane.
on a JEOL FX 90Q or a JEOL EX 400 NMR spectrometer
(J values are given in Hz). Mass spectra were obtained using
a Cresta MS 30 instrument or a VG20-250 quadrupole
instrument.
The synthesis of aziridines using ꢀ-chloromethyltrimethylsilane
and azomethines
These reactions were carried out according to the general
procedure described below.
In conclusion we have found that the synthesis of 2-trialkyl-
silylaziridines, 1, cannot be achieved by any one method but
requires a number of strategies to obtain the required range of
substitution patterns.
cis-3-Phenyl-1-propyl-2-trimethylsilylaziridine. Typically,
a
solution of sec-butyllithium (1.42 g, 22.20 mmol) was added to
a solution of α-chloromethyltrimethylsilane (2.50 g, 20.40
mmol) and TMEDA (2.37 g, 20.40 mmol) in THF under nitro-
gen at Ϫ78 ЊC. The yellow–orange solution was stirred at
Ϫ78 ЊC (1 h) and the temperature of the cold bath raised to ca.
Ϫ65 ЊC. To this was added a solution of N-benzylidenepropyl-
amine (3.00 g, 20.40 mmol) in THF (3 ml). The temperature
was raised to ca. Ϫ40 ЊC and the resultant orange solution was
stirred (1 h). The bath temperature was finally raised to room
temperature. The reaction mixture was stirred over 17 h under
nitrogen to give a deep reddish orange solution. This was
quenched with a saturated solution of ammonium chloride (20
Experimental
Melting points were determined on a Büchi 510 melting point
apparatus and are uncorrected. Infrared spectra were obtained
as Nujol mulls or thin films using sodium chloride plates or as
KBr discs on a Pye Unicam SP1050 or a Nicolet 205 FT-IR
spectrometer. NMR spectra were recorded as solutions in
deuteriochloroform with tetramethylsilane as internal standard
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Table 3 Yields of trimethylsilylaziridines prepared by the thermal
chloromethyltrimethylsilane (3.8 g, 31.06 mmol), TMEDA
addition of phenyl azide to vinylsilanes
(3.61 g, 30.98 mmol) and N-(methylbenzylidene)propylamine
(5.00 g, 31.20 mmol). The reaction mixture was analysed by
TLC and GLC. The chromatogram showed recovery of the
starting azomethine (65.9%). Three other components at higher
retention times were detected in the following respective yields:
1.5, 4.0 and 28.6% w/w. The reaction was further purified on
a silica column using hexane–diethyl ether as eluent (11:1).
The azomethine decomposed to give acetophenone (60%).
1-Phenyl-3-trimethylsilylpropan-1-one was obtained (30%) and
Alkene
Aziridine
Yield (%)
16
70
1
characterised by H NMR, δH(90 MHz, CDCl3, Me4Si) 0.00
(9H, s, SiMe3), 0.82 (2H, t, J 9.0, Si-CH2), 2.85 (2H, t, J 9.0,
CH2-CO) and 7.32–8.10 (5H, m, Ph). The product was con-
firmed by comparison with the spectrum of an authentic
sample.21
17
15
88
61
The synthesis of 1-bromo-2-azides via the addition of
bromoazide to vinylsilanes (Procedure A)
With the modifications given below, the following general
method, which is similar to that used by Duboudin and
Laporte,11 was applied to the synthesis of bromoazides from
trans-trimethylsilylstyrene and triphenylvinylsilane. The
method is described for trans-trimethylsilylstyrene.
(RS)/(SR)-2-Azido-1-bromo-2-phenyl-1-trimethylsilylethane.
Bromine (8.00 g 50 mmol) was added dropwise to an ice-cooled
mixture of sodium azide (32.5 g 500 mmol) in 100 ml of
dichloromethane containing 25 ml of 30% hydrochloric acid.
The mixture was stirred for 45 minutes. The organic layer con-
taining the bromoazide was decanted from the aqueous layer
and suspended solids, and added dropwise to a stirring, pre-
cooled (Ϫ5 ЊC) solution of trans-trimethylsilylstyrene (8.80 g 50
mmol) in dichloromethane. The mixture was stirred for 45 min-
utes at 0 ЊC. Washing with two 50 ml portions of dilute sodium
bicarbonate solution was followed by rotary evaporation at
roomtemperaturetogive(RS)/(SR)-2-azido-1-bromo-2-phenyl-
1-trimethylsilylethane as a pale pink oil, (12.5 g, 42 mmol,
84%). This was contaminated by a small amount (ca. 5% by
NMR spectroscopy) of the SS/RR adduct. Column chromato-
graphy failed to separate these isomers and so the product was
used in the next step as a mixture; νmax(neat)/cmϪ1 2100(str),
1490, 1450, 1310, 1430, 1240, 740 and 700; δH(90 MHz, CDCl3,
Me4Si) 0.09 (9H, s, SiMe3), 3.68 (1H, d, J 9.03, CBr), 4.84 (1H,
d, J 9.03, CN3) and 7.42 (5H, s, Ph); δC(90 MHz, CDCl3, Me4Si)
Ϫ1.55 (SiMe3), 47.45 (CSi), 6.91 (CPh), 127.93, 129.48, 129.66
and 129.37 (Ph).
ml), followed by extraction with diethyl ether (3 × 20 ml) and
the yellow organic layer was dried over anhydrous magnesium
sulfate. The filtrate was concentrated at 40 ЊC/15 mmHg and
was distilled under reduced pressure to give cis-3-phenyl-1-
propyl-2-trimethylsilylaziridine (2.5 g, 53%), bp 46–48 ЊC/0.02
mmHg; νmax(neat)/cmϪ1 3000, 2850, 1250, 850 and 700; δH(90
MHz, CDCl3, Me4Si) Ϫ0.23 (9H, s, SiMe3), 0.10 (1H, d, J 7.5,
CH), 1.00 (3H, t, CH2-CH3), 1.70 (2H, m, CH2-CH2-CH3), 2.60
(1H, d, J 7.5, CH), 3.6 (2H, t, N-CH2) and 6.80 (5H, m, Ph);
δC(22.5 MHz, CDCl3, Me4Si) Ϫ1.84 (SiMe3), 12.04 (CH2-CH3),
23.41 (CH2CH2CH3), 38.14 (C-SiMe3), 46.36 (CPh), 66.32 (N-
CH2), 126.36, 127.79, 128.60 and 140.26 (Ph) (Found: C, 72.1;
H, 10.0; N, 6.1. C14H23N requires C, 72.0; H, 9.9; N, 6.0%).
cis and trans-1,3-Diphenyl-2-trimethylsilylaziridines. The
reaction was carried out using sec-butyllithium (0.86 g, 13.50
mmol), chloromethyltrimethylsilane (1.50 g, 12.20 mmol),
TMEDA (1.42 g, 12.20 mmol) and N-benzylideneaniline (2.21
g, 12.20 mmol). A sample of the reaction mixture was separated
by chromatography on a silica column using diethyl ether–
hexane (1:11) to give cis- and trans-1,3-diphenyl-2-trimethyl-
silylaziridines in the ratio of 52:48 (2.52 g, overall yield 77.1%).
2-Azido-1-bromo-1-triphenylsilylethane. In a modification of
the general procedure A, this azide was prepared using an
increased proportion of sodium azide to bromine, in order to
preclude formation of the dibromo adduct. Also, the product
mixture was stirred at room temperature for an additional 7
hours prior to work up to ensure complete reaction. The reac-
tion was carried out using; vinyltriphenylsilane (7.5 g, 26
mmol), bromine (4.8 ml, 30 mmol), sodium azide (30 g, 462
mmol) and 20% hydrochloric acid (20 ml). Evaporation of the
organic layer yielded a pale orange solid. Recrystallization from
a mixture of chloroform–hexane (2:5) gave 2-azido-1-bromo-1-
triphenylsilylethane as a white solid (6.85 g, 16.8 mmol, 56%);
δH(400 MHz, CDCl3, Me4Si) 3.36 (1H, dd, J 10.4, 13.6, HCBr),
3.89 (1H, dd, J 2.8, 13.6, HaHbCN3), 4.10 (1H, dd, J 2.8, 10.4,
HaHbCN3), 7.46–7.69 and 7.75–7.95 (15H, m, 3 × Ph); δC(100
MHz, CDCl3, Me4Si) 37.0 (CSi), 54.8 (CN3), 127.6, 130.1, 131.2
and 135.8 (3 × Ph).
cis-1,3-Diphenyl-2-trimethylsilylaziridine. 1.30 g; νmax(neat)/
cmϪ1 3150, 2850, 1600, 1500, 1410, 1260, 850, 750 and 690;
δH(90 MHz, CDCl3, Me4Si) Ϫ0.12 (9H, s, SiMe3), 1.70 (1H, d,
J 8.0, CH), 3.45 (1H, d, J 8.0, CH) and 6.95–7.65 (10H,
m, 2 × Ph); δC(22.5 MHz, CDCl3, Me4Si) Ϫ1.95 (SiMe3), 38.37
(C-SiMe3), 46.07, 120.35, 122.25, 127.01, 127.59, 128.05,
129.91, 139.25 and 157.60 (2 × Ph) (Found: C, 76.2; H, 7.7; N,
5.2. C17H21NSi requires C, 76.3; H, 7.9; N, 5.2%).
trans-1,3-Diphenyl-2-trimethylsilylaziridine. Was obtained as
white crystals (1.22 g); νmax(Nujol)/cmϪ1 3063, 3033, 2954, 2923,
2856, 1702, 1598, 1492, 1456, 1401, 1318, 1253, 1218, 1178,
1146, 1095, 1969, 1026, 999, 932, 896, 844, 792, 760, 717, 697
and 669; δH(90 MHz, CDCl3, Me4Si) Ϫ0.04 (9H, s, SiMe3), 1.85
(1H, d, J 4.5, CH), 3.28 (1H, d, J 4.5, CH) and 6.85–7.48 (m,
10H, 2 × Ph); δC(22.5 MHz, CDCl3, Me4Si) Ϫ2.01 (SiMe3),
41.30 (C-SiMe3), 42.85 (C-Ph), 120.80, 121.90, 126.50, 127.10,
128.30, 128.70, 139.50 and 152.20 (2 × Ph) (Found: C, 76.1; H,
7.8; N, 5.1. C17H21NSi requires C, 76.3; H, 7.9; N, 5.2%).
The synthesis of 1-bromo-2-azides via the addition of bromoazide
to vinylsilanes (Method B)
1-Phenyl-3-trimethylsilylpropan-1-one. The reaction was
carried out using sec-butyllithium (2.19 g, 34.20 mmol),
This method was used to prepare the corresponding
bromoazides from trans-trimethylsilylstyrene and trans-1-tri-
J. Chem. Soc., Perkin Trans. 1, 2000, 1173–1180
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methylsilylhex-1-ene. The method is described for trans-
phenyl-2-trimethylsilylaziridine using (RR)/(SS)-2-azido-1-
trimethylsilylstyrene.
bromo-2-phenyl-1-trimethylsilylethane (3.6 g, 12.1 mmol) and
lithium aluminium hydride (1.38 g, 36.3 mmol). The product
was purified by column chromatography, on silica using hexane
as the eluent; δH(400 MHz, CDCl3, Me4Si) 0.03 (9H, s, SiMe3),
0.83 (1H, s, NH), 1.13 (1H, d, Jtrans 4, CHPh), 2.80 (1H, d, J 4,
CHPh) and 7.21 (5H, s, Ph); δC(400 MHz, CDCl3, Me4Si)
Ϫ0.40 (Me3Si), 32.28 (CHSi), 35.44 (CHPh), 126.15, 127.22,
128.2 and 141.20 (Ph).
(SS)/(RR)-2-Azido-1-bromo-2-phenyl-1-trimethylsilylethane.
N-Bromosuccinimide (24 g, 135 mmol) was added in small
portions to a pre-cooled (Ϫ6 ЊC), stirred mixture of aqueous
(100 ml) sodium azide (22.3 g, 343 mmol) in 1,4-dioxane (300
ml) containing the alkene trans-trimethylsilylstyrene (16.9 g,
96.2 mmol). The mixture was then stirred at 0 ЊC until the
orange colour of the bromoazide disappeared (30 min–1 h) and
a clear solution remained. This was washed several times with
brine and extracted with ether. Following concentration,
residual succinic acid was removed by precipitation in carbon
tetrachloride. The product oil, (SS)/(RR)-2-azido-1-bromo-2-
phenyl-1-(trimethylsilyl)ethane was recovered as a single dia-
stereoisomer and purified by flash column chromatography on
silica using neat hexane as the eluent (20.6 g, 69.1 mmol, 72%);
δH(400 MHz, CDCl3, Me4Si), 0.24 (9H, s, Me3Si), 3.64 (1H,
d, J 8.4, CHBr), 4.84 (1H, d, J 8.4, CHN3) and 7.32 (5H, s, Ph).
2-Triphenylsilyl aziridine 6. This was prepared using 2-azido-
1-bromo-1-triphenylsilylethane (3.0 g, 7.35 mmol) and lithium
aluminium hydride (0.75 g, 19.8 mmol). The white solid that
was obtained was recrystallised from 2:5 chloroform–hexane
yielding 1.98 g, (6.58 mmol, 89.5%) 2-triphenylsilylaziridine as
fine white plates, which decompose on heating; νmax(Nujol)/
cmϪ1 3045, 2900, 1590, 1485, 1430, 1115, 855, 800, 730 and 700;
δH(400 MHz, CDCl3, Me4Si) 1.42 (1H, d, J 7.2, CHaHbCHc),
1.64 (1H, d, J 6.4, CHaHbCHc), 1.88 (1H, d, J 6.8, CHaHbCHc),
7.22–7.29 (10H, m, Ph3Si) and 7.52–7.61 (5H, m, Ph3Si); δC(400
MHz, CDCl3, Me4Si), 15.23 (CSi), 22.02 (CN), 127.80, 129.48,
135.77 and 136.70 (Ph3Si); m/z (EI) 301 (Mϩ, 8.2%), 259 (SiPh3,
12.0), 182 (SiPh2, 17.3), 180 (24.3), 105 (SiPh, 12.3), 94
(PhNϩH3) and 73 (100.0) (Found: C, 79.4; H, 6.5. C20H19NSi
requires C, 79.7; H, 6.3%).
2-Azido-1-bromo-1-trimethylsilylhexane. This was prepared
in 71% yield, as a colourless oil by the general procedure B
using: N-bromosuccinimide (24.0 g, 135 mmol), sodium azide
(22.3 g, 343 mmol) and trans-1-trimethylsilylhex-1-ene (15.5 g,
96.2 mmol); νmax(neat)/cmϪ1 2960, 2100, 1250 and 840; δH(400
MHz, CDCl3, Me4Si), 0.21 (9H, s, Me3Si), 0.80–1.05 (3H, m,
CH3), 1.10–2.80 (6H, m, CH2CH2CH2), 3.39 (1H, d, J 5.1,
CHBr) and 3.49–3.95 (1H, m, CHN3); δC(100 MHz, CDCl3,
Me4Si) 0.574 (SiMe3), 14.4 (CH3), 24.59 (CH2CH3), 30.79
(CH2CH2CH3), 35.44 (CH2CHN), 47.80 (CSi) and 67.73 (CN)
(Found: C, 39.0; H, 7.5. C9H20N3BrSi requires C, 38.8; H, 7.2%).
The synthesis of trans-2-trimethylsilyl-3-butylaziridine 5 by
reaction of 2-azido-1-bromo-1-trimethylsilylhexane with
triphenylphosphine
To a solution of 2-azido-1-bromo-1-trimethylsilylhexane (0.28
g, 1.01 mmol) in THF (4 ml) was added triphenylphosphine
(0.22 g, 1.10 mmol). The resulting yellow mixture was heated to
50 ЊC and stirred rapidly for 1.5 h. On cooling to room temper-
ature, 5 ml of 2 M sodium hydroxide were added followed by
stirring for 1 h. The mixture was extracted with ether, dried and
concentrated. On addition of hexane a white solid precipitated,
leaving a yellow oil. The oil was separated from the solid and
purified by flash column chromatography to give trans-3-butyl-
2-trimethylsilylaziridine as a colourless oil (0.13 g, 0.765
mmol, 76%); νmax(neat)/cmϪ1 3000–2850, 1710, 1455, 1245, 1100
and 870–820; δH(400 MHz, CDCl3, Me4Si) Ϫ0.05 (9H, s,
Me3Si), 0.63 (1H, d, J 4.6, CHSi), 0.69–1.57 (9H, m, CH3CH2-
CH2CH2) and 2.61–2.85 (1H, m, NCH2CH2); δC(100 MHz,
CDCl3, Me4Si) 3.27 (Me3Si), 14.13 (CH3), 22.69 (CH3CH2),
26.54 (CHSi), 30.16 (CH3CH2CH2), 34.58 (NCHCH2) and
37.521 (NCHCH2); m/z (EI) 172 ([M ϩ H]ϩ, 100.0%), 128 (5),
100 (12) and 98 (Mϩ Ϫ SiCH3, 6) (Found: (M ϩ H)ϩ, 172.1524
(EI). C9H22NSi requires M 172.1443).
The synthesis of trimethylsilylaziridines by reduction of 1-bromo-
2-azides with lithium aluminium hydride
Lithium aluminium hydride reduction of the corresponding
1-bromo-2-azide was used to form cis-3-phenyl-2-trimethyl-
silylaziridine, trans-3-phenyl-2-trimethylsilylaziridine and 2-tri-
phenylsilylaziridine. The method is described for preparation of
cis-3-phenyl-2-trimethylsilylaziridine.
cis-3-Phenyl-2-trimethylsilylaziridine, 4. A slurry of lithium
aluminium hydride (1.7 g, 44.8 mmol) in dry ether (30 ml) was
cooled (ice-salt bath) with stirring under nitrogen. (RS)/(SR)-2-
Azido-1-bromo-2-phenyl-1-trimethylsilylethane (95%, 4.61 g,
14.7 mmol) in dry ether (5 ml) was added dropwise over 10 min
carefully maintaining the temperature below 0 ЊC. Slight effer-
vescence was accompanied by the production of a pale olive
green colour. The mixture was stirred for a further 45 minutes at
0 ЊC and then allowed to warm to room temperature. Stirring
was continued for a further 17 hours. Recooling to 0 ЊC was
followed by slow hydrolysis with 9 ml of a 20% sodium
hydroxide solution, added dropwise with stirring over a period
of 15 minutes. After warming to room temperature, the solu-
tion was stirred rapidly for 45 minutes. The resulting fine white
granular solid was washed well with ether and the mother
liquor and washings were carefully dried with magnesium
sulfate over several hours. Concentration gave 2.6 g of a
colourless, oily product. Purification of this by flash column
chromatography on silica gel, using pentane as the eluant
was accompanied by substantial decomposition giving 1.1 g
(5.76 mmol, 39%) of cis-3-phenyl-2-trimethylsilylaziridine as a
colourless, pungent smelling oil; δH(400 MHz, CDCl3, Me4Si)
Ϫ8.22 (9H, s, SiMe3), 1.11 (1H, s, NH), 1.34 (1H, d, J 7.3,
CHSiMe3), 3.40 (1H, d, J 7.3, CHPh) and 7.16–7.32 (5H, C’s
Ph); δC(100 MHz, CDCl3, Me4Si) Ϫ2.12 (SiMe3), 27.69 (C-Si),
37.11 (C-Ph), 126.50, 127.42, 127.65 and 139.42 (Ph); m/z (EI)
190 (Mϩ Ϫ H, 26.8%), 176 (Mϩ Ϫ CH3, 5.8), 161 (Mϩ Ϫ 2 ×
CH3, 161), 117 (10.5), 105 (40.5), 91 (16.9), 77 (23.3) and 73
(SiMe3, 100).
Synthesis of 2-trimethylsilylaziridines by the photochemical
reaction of organoazides with vinylsilanes
1-Ethoxycarbonyl-2-trimethylsilylaziridine,
10.7
Ethyl
azidoformate (3.4 g, 30 mmol) and vinyltrimethylsilane (1.5 g,
15 mmol) were placed in a quartz tube and irradiated at 254 nm
for 48 hours using a medium pressure arc carousel (rayonet).
The tube was then recharged with vinyltrimethylsilane (1.5 g, 15
mmol) and irradiated for a further 48 hours. The resultant
yellow oil was purified by chromatography on a silica-gel
column, using ether–pentane (1:20) as the eluent. Fractions
were collected and analysed by TLC. The pure aziridine (3.6 g,
19.3 mmol, 64%) was obtained in the first fraction as a sweet
smelling colourless oil; δH(400 MHz, CDCl3, Me4Si) 0.07 (9H, s,
Me3Si), 1.27 (3H, t, J 7.2, CH3), 1.65 (1H, dd, J 5.1, 7.3, SiCH),
2.04 (1H, dd, J 5.1, 1.2, CHaCHb), 2.38 (1H, dd, J 7.2, 1.2,
CHaHb) and 4.13 (2H, q, J 7.2, OCH2); δC(100 MHz, CDCl3,
Me4Si) 14.3 (CH2CH3), 28.1 (CHSi), 28.4 (CH2N), 62.2
(CH CH ) and 164.2 (C᎐O).
᎐
2
3
trans-3-Phenyl-2-trimethylsilylaziridine, 3.6 This compound
was prepared (91%) according to the procedure for cis-3-
trans-3-Butyl-1-ethoxycarbonyl-2-trimethylsilylaziridine, 11.
trans-1-Trimethylsilylhex-l-ene (6.24 g, 40 mmol) was placed in
1178
J. Chem. Soc., Perkin Trans. 1, 2000, 1173–1180

View Article Online
a quartz tube for irradiation. Ethyl azidoformate was added
over eight days in four equal portions of 1.15 g (10 mmol),
during the irradiation process. Hexane (10 ml) was added to the
resultant yellow oil effecting precipitation of a white solid. The
mixture was filtered and the mother liquor concentrated to give
a pale yellow oil. This was purified by chromatography on silica
gel, using hexane as the eluent. The fractions were analysed by
NMR spectroscopy. Residual alkene was collected in the early
fractions. Later fractions yielded the pure aziridine as a colour-
less, faintly sweet smelling oil (4.1 g, 24.0 mmol, 60%); δH(400
MHz, CDCl3, Me4Si) 0.06 (9H, s, Me3Si), 0.91 (3H, t, CH2-
CH2CH3), 0.77 (1H, d, J 6.3, CHSi), 1.12–1.53 (9H, m,
CH2CH2CH2 and CH3CH2O), 2.04–2.34 (1H, m, CH2CHN)
and 4.12 (2H, q, OCH2); δC(100 MHz, CDCl3, Me4Si) Ϫ2.9
(Me3Si), 14.0 (CH3), 14.4 (CH3), 22.4 (CH3CH2CH2), 29.4
(CH3CH2CH2), 33.2 (NCHCH2), 35.2 (CHSi), 40.3 (CHCH2),
61.9 (CH O) and 163.0 (C᎐O); m/z (EI) 244 ([M ϩ H]ϩ, 13.7%),
CDCl3, Me4Si) 0.00 (Me2Si), 14.03 (2 × CH2CH3), 25.74 and
26.02 (CHSiMe2), 28.49 (CH2N), 62.50 (CH2O) and 164.12
(C᎐O); m/z (EI) 287 ([M ϩ H]ϩ, 17.9%), 271 (Mϩ Ϫ Me, 4.7),
᎐
246 (15.4), 172 ([M Ϫ EtO2CNCH2CH2]ϩ, 100.0), 103 (22.6),
100 (60.1), 85 (17.1), 75 (23.7) 59 (28.4) and 29 (81, Et)
(Found: Mϩ Ϫ CH3, 271.1114 (EI). C11H19NO4Si requires M,
271.1111).
1-Phenyl-2-trimethylsilylaziridine, 15, with solvent. Phenyl
azide (3.2 g, 26.9 mmol) and vinyltrimethylsilane (5.4 g,
53.8 mmol) in 10 ml hexane were placed in a 20 ml quartz
tube and mounted in a Rayonet photochemical reactor. The
solution was irradiated using a medium pressure arc (ca.
5.5 W) for 5 h. The product was analysed by NMR spectro-
scopy which indicated the presence of product and intermediate
triazoline δH(CDCl3) 0.14 (SiMe3), 3.10–4.20 (complex pattern,
non-aromatic H’s), 6.40–7.50 (phenyl H’s) in a 1:1 ratio. Fur-
ther irradiation or recharging with vinylsilane failed to improve
the ratio. Overall yields were low due to evaporation of the
vinylsilane within the cell which was known to reach 40 ЊC.
Heating the aziridine–triazoline mixtures had no effect.
᎐
2
228 (Mϩ Ϫ CH3, 26.6), 214 (Mϩ Ϫ Et, 22.2), 198 (Mϩ Ϫ OEt,
12.1), 170 (Mϩ Ϫ CO2Et or SiMe3, 89.7), 156 (13.4), 142 (24.1),
128 (11.2), 114 (15.8), 103 (21.2), 73 (SiMe3 or CO2Et, 100.0)
and 59 (44.4) (Found: C, 59.2; H, 10.4; N, 5.3. C12H25NO2Si
requires: C, 59.2; H, 10.4; N, 5.7%).
1-Phenyl-2-trimethylsilylaziridine, 15, without solvent. A mix-
ture of phenyl azide (0.50 g, 4.20 mmol) and vinyltrimethyl-
silane (0.80 g, 8.00 mmol) was placed in a quartz UV cuvette
and mounted in a Rayonet photochemical reactor. The solution
was irradiated using a medium pressure arc (ca. 5.5 W) for 1 h.
1-Methoxycarbonyl-2-trimethylsilylaziridine, 12.9 Vinyl-
trimethylsilane (1.0 g, 10.0 mmol) and methyl azidoformate
(1.01 g, 10 mmol) were irradiated continuously for 24 hours
in a quartz tube. The resultant mixture was evaporated and
purified by chromatography on silica with pentane as the eluent.
The product, l-methoxycarbonyl-2-trimethylsilylaziridine was
obtained as a colourless oil (0.55 g, 2.49 mmol, 24.9%); δH(400
MHz, CDCl3, Me4Si) Ϫ0.062 (9H, s, Me3Si), 1.55 (1H, dd,
J 7.33, 5.12, CHSi), 1.93 (1H, dd, J 1.22, 3.9, CHaHb), 2.27 (1H,
dd, J 1.22, 7.33, CHaHb) and 3.73 (3H, 5, OCH3); δC(100 MHz,
CDCl3, Me4Si) Ϫ3.3 (Me3Si), 28.3 (CSi), 28.6 (CH2), 53.4
1
A brown–orange solution was obtained and analysed by H
NMR. The mixture afforded 1-phenyl-2-trimethylsilyl-1,2,3-
triazoline (70%) and 1-phenyl-2-trimethylsilylaziridine (30%).
After 3 h irradiation, the reaction mixture afforded 1-phenyl-2-
trimethylsilylaziridine (50%).
General procedure for the synthesis of aziridines by the
thermolysis of phenyl azide in the presence of vinylsilanes
(OCH ) and 164.8 (C᎐O).
᎐
3
Aziridines were synthesized by the thermolysis of phenyl azide
in the presence of vinyltrimethylsilane, methyl 2-(triethylsilyl)-
propenoate and methyl 2-(dimethylphenylsilyl)propenoate
under an identical set of conditions. A general method is
described for the synthesis of 2-methoxycarbonyl-1-phenyl-2-
(triethylsilyl)aziridine.
1-Ethoxycarbonyl-2-(dimethylvinylsilyl)aziridine, 13. Divi-
nyldimethylsilane (2.0 g, 17.9 mmol) and ethyl azidoformate
(2.1 g, 18.3 mmol) were irradiated continuously for 4 days in a
quartz tube. The resultant mixture was evaporated and purified
by chromatography on silica with pentane as the eluent. The
product, 1-ethoxycarbonyl-2-(dimethylvinylsilyl)aziridine was
obtained as a clear oil (1.9 g, 9.55 mmol, 53%). NMR spectro-
scopy shows that the product is a mixture of diastereoisomers
which are present in roughly equal amounts; δH(400 MHz,
CDCl3, Me4Si) Ϫ0.021 and 0.010 (6H, 2 × s, Me2Si), 1.11 (3H,
t, CH2CH3), 1.55 (1H, dd, J 7.33, 5.13, Hc), 1.92 (1H, dd, J 1.22,
5.13, Ha), 2.23 (1H, dd, J 1.22, 7.08, Hb), 3.97 (2H, q, CH2) and
Methyl 2-(dimethylphenylsilyl)propenoate.
A
catalytic
amount (0.2 g) of 10% platinum on carbon (or hexachloro-
platinic acid) was added to a stirring solution of dimethyl-
phenylsilane (3.10 g, 22.8 mmol) and methyl propynoate (1.92
g, 22.8 mmol). A mildly exothermic reaction was accompanied
with weak effervescence. After 0.5 hours a substantial exotherm
ensued accompanied by the development of a dark brown
colour. The catalyst was removed by precipitation in hexane.
The crude product comprised methyl 2-(dimethylphenylsilyl)-
propenoate (70%) the remainder being the vicinal adduct,
methyl (E)-3-(dimethylphenylsilyl)propenoate. Pure methyl
2-(dimethylphenylsilyl)propenoate (3.2 g, 14.6 mmol, 64.2%)
was obtained by chromatography on silica, with hexane as the
eluent. The product appeared in the later fractions; δH(400
MHz, CDCl3, Me4Si) 0.41 (Me2Si), 3.61 (3H, s, OCH3), 5.92
(1H, d, J 2.93, H H C᎐), 6.80 (1H, d, J 2.93, H H C᎐), 6.796–
5.74–6.04 (3H, m, HC᎐CH ); δ (100 MHz, CDCl , Me Si) Ϫ5.3
᎐
2
C
3
4
and Ϫ5.0 (Me2Si), 14.3 (CH3), 26.9 (CSi), 28.2 (NCH2), 62.0
(CH CH ), 133.8 (HC᎐CH ), 135.7 (H C᎐CH) and 163.8
᎐
᎐
2
2
3
2
(C=O); m/z (EI) 200 ([M ϩ H]ϩ, 18.6%), 173 ([M ϩ H]ϩ Ϫ
H C᎐CH, 15.2), 172 (Mϩ Ϫ H C᎐CH, 35.9), 126 (Mϩ Ϫ
᎐
᎐
2
2
CO2Et, 42.7), 112 (25.9), 103 (44.2), 100 (Mϩ Ϫ CH2CHSiMe3,
70.0), 87 (19.7), 86 (CH2CHSiHMe2ϩ, 42.1), 85 (CH2CH-
SiMe2ϩ, 69.7), 75 (41.1), 73 (CO2Etϩ, 26.6), 71 (27.2) and 59
(100.0) (Found: Mϩ Ϫ CH3, 184.0708 (EI). C8H14NO2Si
requires M, 184.0794; Found: Mϩ Ϫ CO2Et, 126.0352. C6H12-
NSi requires M, 126.0375).
᎐
᎐
b
a
b
a
6.803 and 7.29–7.50 (5H, m, Ph); δC(100 MHz, CDCl3, Me4Si)
Ϫ2.2 (MeSi), 1.5 (MeSi), 52.2 (OMe), 128.4, 129.9 and 141.9
Bis(1-ethoxycarbonylaziridin-2-yl)dimethylsilane,
14.
1-
(Ph), 134.2 and 134.6 (H C᎐ and SiC᎐), 170.0 (C᎐O) (Found:
᎐
᎐
᎐
2
Ethoxycarbonyl-2-(dimethylvinylsilyl)aziridine (1.2 g, 6.0
mmol) and ethyl azidoformate (0.69 g, 6.0 mmol) were irradi-
ated in a quartz tube for 48 hours. The product oil was purified
by chromatography on silica. The column was eluted with neat
hexane until all of the residual alkene had been collected before
increasing the polarity gradually (up to 20% diethyl ether).
Bis(1-ethoxycarbonylaziridin-2-yl)dimethylsilane was obtained
in the later fractions as a colourless oil (0.5 g, 0.174 mmol,
28.9%). The product was present as a mixture of diastereo-
isomers as indicated by the 13C NMR spectrum; δC(400 MHz,
C, 66.3; H, 7.5. C12H16O2Si requires C, 66.4; H, 7.3%).
Methyl 2-(diphenylmethylsilyl)propenoate. This was prepared
by the same method as for methyl 2-(dimethylphenylsilyl)-
propenoate. The product mixture consisted of 60% of the
geminal isomer (methyl 2-(diphenylmethylsilyl)propenoate) and
40% of the vicinal isomer (methyl (E)-3-(diphenylmethylsilyl)-
propenoate). A hexane solution yielded a yellow solid such that
almost pure methyl 2-(diphenylmethylsilyl)propenoate was
recovered from the mother liquor. Successive cooling of the
J. Chem. Soc., Perkin Trans. 1, 2000, 1173–1180
1179

View Article Online
mother liquor in stages yielded a yellow oil which was further
purified by flash column chromatography; δH(400 MHz, CDCl3,
Me4Si) 0.46 (3H, 5, MeSi), 3.19 (3H, s, OCH3), 5.53 (1H, d,
trans-3-Butyl-2-trimethylsilylaziridine, 5, by the reduction of
trans-3-butyl-1-ethoxycarbonyl-2-trimethylsilylaziridine. A solu-
tion of trans-3-butyl-1-ethoxycarbonyl-2-trimethylsilylaziridine
(0.28 g, 1.07 mmol) in dry ether (3 ml) was added dropwise over
a 10 minute period to a stirring slurry of lithium aluminium
hydride (0.13 g, 3.42 mmol) in ether (20 ml) at 0 ЊC. The mixture
was stirred for a further 1 h at 0 ЊC and allowed to warm to
room temperature and stirred overnight. The grey coloured
reaction mixture was again cooled to 0 ЊC and hydrolysed by
dropwise addition of water (3 ml). The mixture was stirred
rapidly for 30 minutes. The resultant white solid was washed
with small portions of ether and the ethereal solution dried.
The solvent was distilled from the product to give a pungent,
pale yellow oil. This was further purified by flash column
chromatography on silica, using pentane as the eluant, to give
trans-3-butyl-2-trimethylsilylaziridine as a clear oil (0.139 g,
0.628 mmol, 59%).
J 1.20, H H C᎐), 6.48 (1H, d, J 1.20, H H C᎐) and 6.70–7.20
᎐
᎐
b
a
b
a
(10H, m, Ph2Si) (Found C, 72.0; H, 6.5. C17H18O2Si requires C,
72.3; H, 6.4%).
2-Methoxycarbonyl-1-phenyl-2-triethylsilylaziridine, 16.
A
60:40 mixture of methyl 2-(triethylsilyl)propenoate (15 g, 45
mmol) and methyl (E)-3-(triethylsilyl)propenoate8 was heated
to 110–120 ЊC in the presence of phenyl azide (5.35 g, 45
mmol). Heating was continued until evolution of nitrogen had
subsided (ca. 2 hours). All of the methyl 2-(triethylsilyl)propen-
oate reacted to give 2-methoxycarbonyl-1-phenyl-2-triethylsilyl-
aziridine and the vicinal alkene remained mostly unreacted.
The residual alkene was removed by chromatography on silica,
and the product aziridine purified by distillation (bp, 110–
117 ЊC, 0.1 mmHg) to give pure 2-methoxycarbonyl-1-phenyl-
2-triethylsilylaziridine (9.8 g, 31.5 mmol, 70%); δH(400 MHz,
CDCl3, Me4Si) 0.68–0.84 (6H, m), 0.90–1.54 (9H, m), Et3Si,
2.40 (1H, d, J 1.60, NCHaHb), 2.76 (1H, d, J 1.60, NCHaHb),
3.44 (3H, s, OMe) and 6.83–7.16 (5H, m, Ph); δC(100 MHz,
CDCl3, Me4Si) 2.3 (3 × CH2Si), 7.9 (3 × CH3CH2Si), 35.6
(NCSi), 36.9 (CH2N), 51.5 (CH3O), 120.6, 123.1, 128.5
References
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and 150.7 (Ph) and 172.0 (C᎐O) (Found: Mϩ, 291.1699
᎐
(EI). C16H25NO2Si requires M, 291.1655) (Found: C, 65.7; H,
8.8; N, 4.5. C16H25NO2Si requires C, 65.9; H, 8.7; N, 4.8%).
2-Methoxycarbonyl-2-dimethylphenylsilyl-1-phenylaziridine,
17. This was prepared using methyl 2-(dimethylphenylsilyl)-
propenoate (2.0 g, 80%, 7.27 mmol) and phenyl azide (0.87 g,
7.31 mmol) to give, after purification by column chromato-
graphy, pure 2-methoxycarbonyl-2-dimethylphenylsilyl-1-phen-
ylaziridine as a colourless viscous oil (2.0 g, 6.43 mmol, 88%);
νmax(neat)/cmϪ1 3100, 2810, 1740, 1710, 1595, 1490, 1430, 1240,
1110, 835, 815 and 700; δH(400 MHz, CDCl3, Me4Si) 0.30 and
0.38 (2 × 3H, 2 × s, Me2Si), 2.22 (1H, s, NCHaHb), 2.67 (1H, s,
NCHaHb), 3.21 (3H, s, OCH3) and 6.66–7.49 (10H, m, NPh and
SiPh); δC(100 MHz, CDCl3, Me4Si) Ϫ4.0 and Ϫ3.7 (Me2Si),
35.9 (CSi), 38.1 (CH2), 51.8 (CH3), 120.8, 123.0, 128.4, 129.2,
7 E. Lukevics, V. V. Dirnens, Y. S. Goldberg and E. E. Liepinsh,
J. Organomet. Chem., 1986, 316, 249.
8 R. S. Atkinson and B. J. Kelly, J. Chem. Soc., Perkin Trans. 1, 1986,
1657; R. S. Atkinson and B. J. Kelly, J. Chem. Soc., Chem.
Commun., 1989, 836; R. S. Atkinson and B. J. Kelly, Tetrahedron
Lett., 1989, 30, 2703; R. S. Atkinson, M. P. Coogan and I. S. T.
Lochrie, Chem. Commun., 1996, 789; R. S. Atkinson, M. P. Coogan
and I. S. T. Lochrie, J. Chem. Soc., Perkin Trans. 1, 1997, 897.
9 E. Lukevics, V. V. Dirnens, Y. S. Goldberg, E. E. Liepinsh, I. Y.
Kalvinsh and M. V. Shymanska, J. Organomet. Chem., 1984, 268,
C29.
129.7, 134.8, 136.6 and 150.8 (CPh and NPh), 170.6 (C᎐O)
᎐
(Found: C, 69.4; H, 6.9; N; 4.0. C18H21NO2Si requires C, 69.4;
H, 6.8; N, 4.5%).
1-Phenyl-2-trimethylsilylaziridine, 15, with solvent. The mix-
ture of phenyl azide (1.0 g, 8.39 mmol) and vinyltrimethylsilane
(3.30 g, 33.0 mmol) in hexane (5 ml) was heated under reflux at
60 ЊC under nitrogen (3 h). The orange–yellow reaction mixture
was concentrated to dryness. TLC, using hexane as an eluent,
showed the presence of phenyl azide, aziridine and a new prod-
uct. GLC showed the presence of three major components. A
sample (0.73 g) was purified on a silica column using hexane–
diethyl ether (11:1) as eluent. Separation afforded 1-phenyl-2-
trimethylsilylaziridine (0.15 g, 19%); νmax/(neat) cmϪ1 3100–2896,
1595, 1490, 1335, 1155, 925, 840, 750 and 690; δH(400 MHz,
CDCl3, Me4Si) 0.10 (9H, s, SiMe3), 1.30 (1H, dd, CH), 2.10
(2H, m, J 7.5, 5.0, 1.7, CH2) and 6.70–7.40 (5H, m, Ph); δC(100
MHz, CDCl3, Me4Si) Ϫ3.16 (SiMe3), 29.36 (CHSiMe3), 31.14
10 E. J. Thomas and G. H. Witham, J. Chem. Soc., Chem.
Commun., 1979, 212.
11 F. Duboudin and O. Laporte, J. Organomet. Chem., 1978, 156, C25;
F. Duboudin and O. Laporte, J. Organomet. Chem., 1979, 174,
C18.
12 F. Cooke and P. Magnus, J. Chem. Soc., Chem. Commun., 1977,
513.
13 A. R. Bassindale, S. J. Glynn and P. G. Taylor, in The Chemistry of
Organic Silicon Compounds, eds. Z. Rappoport and Y. Apeloig,
Wiley, New York, 1998, Vol. 1, p. 355.
14 R. C. Cambie, R. C. Hayward, P. S. Rutledge, T. Smith-Palmer,
B. E. Swedlund and P. D. Woodgate, J. Chem. Soc., Perkin Trans. 1,
1977, 180; A. Hassner, Acc. Chem. Res., 1971, 4, 9.
15 T. H. Chan and K. Koumaglo, Tetrahedron Lett., 1986, 27,
883.
16 W. Lwowski and J. S. McGonaghy Jr., J. Am. Chem. Soc., 1965, 87,
(᎐CH ), 121.04, 122.02, 128.68 and 156.43 (Ph) (Found: C,
᎐
2
5490.
69.0; H, 8.9; N, 7.3. C11H17NSi requires C, 69.0; H, 9.0; N,
7.3%).
17 E. Lukevics, in Frontiers of Organosilicon Chemistry, eds. A. R.
Bassindale and P. P. Gaspar, The Royal Society of Chemistry,
Cambridge, 1991, p. 383.
1-Phenyl-2-trimethylsilylaziridine, 15, without solvent. Phenyl
azide (2.93 g, 17.1 mmol) and vinyltrimethylsilane (3.42 g, 34.2
mmol) were placed in a round bottomed flask and stirred under
reflux at 55 ЊC for 8 h, and then stirred for a further 48 h at
room temperature. The dark yellow solution was washed in
brine, extracted with ether, dried and evaporated. The product
was distilled under reduced pressure (bp 70–75 ЊC/0.1 mmHg)
to give as a deep yellow oil 1-phenyl-2-trimethylsilylaziridine
(2.00 g, 61.2%).
18 A. R. Bassindale, P. G. Taylor and Y. Xu, J. Chem. Soc., Perkin
Trans. 1, 1994, 1061.
19 B. B. Lohray, Y. Gao and K. B. Sharpless, Tetrahedron Lett., 1989,
30, 2623.
20 A. R. Bassindale, I. Katampe and P. G. Taylor, in the press.
21 W. S. Trahanovsky and A. L. Himstedt, J. Am. Chem. Soc., 1974, 96,
7974.
Paper a905182a
1180
J. Chem. Soc., Perkin Trans. 1, 2000, 1173–1180