Ring opening reactions of 2-trialkylsilylaziridines

Article abstract of DOI:10.1039/a906233e

2-Trialkytsilylaziridines do not readily undergo nucleophilic ring opening without electrophilic assistance. In the presence of strong acids protonation at the nitrogen is followed by nucleophitic attack α to the silicon. With non-nucleophilic counterions, the protonated aziridine can be obtained. N-Alkylation gives the aziridinium salt, which also undergoes α-cleavage. However, the presence of a 3-phenyl substituent gives a stable aziridinium salt that undergoes nucleophilic attack β to the silicon. Reaction of 2-trialkylsilylaziridines with trialkylsilyl halides usually leads to α-cleavage, however, desilylation to give the enamine is also observed. Fluorodesilylation of the 2-trialkylsilylaziridine is not straightforward and only occurred readily when a 2-ethoxycarbonyl group was present. Fluorodesilylation followed by attack on a carbonyl was only observed when very dry samples of fluoride ions were employed.

Full text of DOI:10.1039/a906233e

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Ring opening reactions of 2-trialkylsilylaziridines
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 (in Cambridge, UK) 2nd August 1999, Accepted 25th October 1999
1
2-Trialkylsilylaziridines do not readily undergo nucleophilic ring opening without electrophilic assistance. In
the presence of strong acids protonation at the nitrogen is followed by nucleophilic attack α to the silicon. With
non-nucleophilic counterions, the protonated aziridine can be obtained. N-Alkylation gives the aziridinium salt,
which also undergoes α-cleavage. However, the presence of a 3-phenyl substituent gives a stable aziridinium salt
that undergoes nucleophilic attack β to the silicon. Reaction of 2-trialkylsilylaziridines with trialkylsilyl halides
usually leads to α-cleavage, however, desilylation to give the enamine is also observed. Fluorodesilylation of the
2-trialkylsilylaziridine is not straightforward and only occurred readily when a 2-ethoxycarbonyl group was present.
Fluorodesilylation followed by attack on a carbonyl was only observed when very dry samples of fluoride ions were
employed.
Introduction
2-Trialkylsilylepoxides undergo regiospecific and stereo-
specific transformations to give vinyl halides,1 enol ethers2
and carbonyl compounds3 and are thus important synthetic
Scheme 1
intermediates. Although the ring opening reactions of 2-tri-
alkylsilylepoxides have been studied extensively, little is known
of the selectivity of ring opening of 2-trialkylsilylaziridines. We
hindered site).12 In such cases the regiochemistry depends upon
have recently published the synthesis of 2-trialkylsilylaziridines,
the reaction conditions and the nature of the nucleophile. The
1, with a range of substituents, including hydrogen, on the ring
ring opening of aziridines is enhanced if there is an electron
withdrawing group on the nitrogen. In such cases quaternis-
ation of the nitrogen is not necessary, however, the regiochemis-
try of ring opening still depends upon the substituents on the
ring carbons, the conditions and the nucleophile.13 Ring open-
ing reactions of aziridines have been recently reviewed by
Tanner.14
These observations suggest that the presence of a 2-trialkyl-
silyl substituent in an aziridine should favour attack α to the
nitrogen and carbons.4 In this paper we report our studies on
silicon if the reaction proceeds via an SN2 type route. However,
the synthetic versatility of silylaziridines and in particular their
attack β to the silicon will be favoured if an SN1 route with a
ring opening reactions with electrophilic and nucleophilic
late transition state is favoured, such that stabilisation involving
reagents.
the C–Si bond can be achieved.
Nozaki, Hudrlik, Whitham and their co-workers5–9 have
shown that nucleophilic attack on 2-trialkylsilylepoxides gener-
ally occurs at the carbon α to the silicon accompanied by
α-opening of the ring. The expected SN1 like β-opening involv-
ing stabilisation of the β-carbocation by the silicon is not
observed since the geometry of the ring prevents overlap of the
C–Si bond with the developing empty p orbital. However, other
substituents in the ring may overwhelm the influence of the
silicon leading to other ring opened products. For example, a
2-trialkylsilylepoxide with one phenyl group in the 3 position
still undergoes nucleophilic attack α to the silicon, however,
the presence of two phenyl groups at the 3 position leads to
formation of a carbocation α to the phenyl groups and β to the
silicon.10 Similarly, with conformationally rigid 2-trialkylsilyl-
epoxides, the bias towards trans diaxial ring opening results in
hydride attack leading to cleavage of either C–O bond.11 This
high regioselectivity of nucleophilic attack of 2-trialkylsilyl-
epoxides α to the silicon is maintained even when the oxygen is
protonated, as shown in Scheme 1, circumstances where SN1
ring opening may be thought to be predominant.
Results and discussion
Ring opening with nucleophilic reagents
Trialkylsilylepoxides do not undergo ring opening by direct
nucleophilic attack with ease. In many cases such reactions only
proceed with electrophilic assistance. For example, cis-1-
trimethylsilyloct-1-ene oxide undergoes ring opening α to the
silicon with pyrrolidine or morpholine in the presence of
alumina.15 However, trialkylsilylepoxides can be transformed
into the corresponding β-hydroxytrialkylsilanes using organo-
metallic reagents, such as organocuprates.16 We found that tri-
alkylsilylaziridines demonstrated a similar resistance to ring
opening. N-Alkyl- and N-phenyl-2-trimethylsilylaziridines, with
and without substituents in the 3 position did not react with
lithium aluminium hydride, sodium methoxide, lithium di-n-
butylcuprate (in the presence and absence of BF3) or pyrrol-
idine in the presence of alumina.
The presence of an ethoxycarbonyl group in the 2 position of
aziridines has been used by Baldwin and co-workers to activate
them towards ring opening with organometallic17 and Wittig18
reagents. Unfortunately, we found that 2-ethoxycarbonyl-1-
phenyl-2-trimethylsilylaziridine did not undergo ring opening
Simple aziridines undergo ring opening only if the nitrogen is
protonated or alkylated. Substitution on the ring carbons leads
to a more “SN1-susceptible” carbon atom (the more substituted
site) and a more “SN2-susceptible” carbon atom (the least
J. Chem. Soc., Perkin Trans. 1, 2000, 439–448
This journal is © The Royal Society of Chemistry 2000
439

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Table 1 Addition of hydrogen halides to a range of 2-trimethylsilylaziridines
Reactant
Hydrogen halide
HCl
Product
Method
A
Yield
46%
B
A
B
76%
83%
72%
a
HCl
HBr
HBr
HI
A
B
B
HCl
HBr
HCl
HBr
60%
76%
B
96%
B
65%
55%
HCl
HBr
A
B
52%
a Crude yield 74%, decomposed on purification.
with methylmagnesium iodide, lithium di-n-butylcuprate,
aniline, benzylamine or diethyl malonate anion. Any reaction
observed was usually the result of attack of the nucleophile at
the carbonyl group.
observe such attack may be due to an electronic effect of the
silicon, which destabilises the transition state of SN2 substitu-
tion in the β position.
Aziridines can be activated to nucleophilic ring opening by
placing an electron withdrawing group on the nitrogen. For
example, N-ethoxycarbonylaziridines undergo facile ring
opening with aniline.13 Again, 1-ethoxycarbonyl-2-trimethyl-
silylaziridine failed to undergo ring opening with the range
of nucleophiles previously mentioned. When reaction was
observed it usually involved loss of the ethoxycarbonyl group.
The inability of 2-trimethylsilylaziridines to undergo ring open-
ing reactions under conditions where non-silyl substituted
aziridines have been shown to react suggest the silicon is in
some way preventing attack at the aziridine ring. Attack at the 2
position, may be hindered by the bulky silicon atom, however,
this does not prevent attack at the 3 position. The failure to
Ring opening reactions with hydrogen halides
Whilst trialkylsilylaziridines are difficult to ring open by purely
nucleophilic means, prior protonation leads to facile ring open-
ing. Addition of hydrogen halides to 2-trialkylsilylaziridines
generally leads regiospecifically to the corresponding β-halo-
amine, as shown in Table 1. The same product was obtained
irrespective of whether a solution of the hydrogen halide in
water (Method A) was used or the pure hydrogen halide in
carbon tetrachloride (Method B). Presumably protonation of
the nitrogen is followed by attack of the nucleophile α to the
silicon. Depending upon the acid, the conditions and the nature
of the group attached to the nitrogen either the free amine or
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J. Chem. Soc., Perkin Trans. 1, 2000, 439–448

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the ammonium salt could be obtained. Treatment of the β-halo-
amine with base gave back the aziridine with retention of
configuration, confirming that the reaction is stereoselective.
Reaction of trans-1,3-diphenyl-2-trimethylsilylaziridine with
any hydrogen halide led to a polymeric product, even at Ϫ78 ЊC.
This is probably the result of nucleophilic attack of the product
amine on the protonated aziridine. Addition of hydrogen chlor-
ide and hydrogen bromide to 2-ethoxycarbonyl-1-phenyl-2-
trimethylsilylaziridine by either method gave only aniline
hydrochloride formed by cleavage of both C–N bonds.
more susceptible to side reactions such as ring opening
or desilylation. 1-Ethoxycarbonyl-2-trimethylsilylaziridine gave
the product of α ring opening with methyl trifluoromethane-
sulfonate, whereas methylation of cis-1,3-diphenyl-2-trimethyl-
silylaziridine led to desilylation.
The cis-1-methyl-3-phenyl-1-propyl-2-trimethylsilylaziridin-
ium triflate was relatively stable, enabling us to examine its ring
opening reactions. Boiling the aziridinium salt in methanol
led to the β ring opened product of solvolysis, 8. Treatment
Ring opening reactions with other acids
Reaction of cis-3-phenyl-1-propyl-2-trimethylsilylaziridine with
trifluoroacetic acid gave the corresponding protonated aziridin-
ium salt. This could be achieved in a range of solvents at room
temperature without further nucleophilic attack of the tri-
fluoroacetate ion. Treatment of the product with base gave back
the free aziridine. However, if the aziridinium salt was refluxed
in methanol or hexane, nucleophilic attack of the anion α to
the silicon was observed. This was followed by acyl exchange
leading to the isolated product 7, as shown in Scheme 2.
with sodium methoxide in methanol led to the corresponding
desilylated product, 9.
Compound 8 arises from an SN1 like process involving an
intermediate/activated complex with substantial carbocation
character adjacent to the phenyl group and β to the silicon.
Such behaviour has been reported by Leonard for the solvolysis
of unsymmetrically carbon-substituted aziridinium ions.19
They found that treatment with methoxide ion led to the prod-
ucts expected for an SN2 type pathway. However, we found that
reaction of the 2-trimethylsilylaziridinium salt with methoxide
ion led to desilylation. This could occur before or after ring
opening, however, we would favour initial desilylation since no
silylated ring opened products were observed in the reaction
mixture during the reaction. We found no evidence of an SN2
type reaction, only an SN1 type ring opening of the desilylated
aziridine which leads to the expected product under the direc-
tion of the phenyl group.
Scheme 2
When 1-ethoxycarbonyl-2-trimethylsilylaziridine and 2-
ethoxycarbonyl-1-phenyl-2-trimethylsilylaziridine were treated
with trifluoroacetic acid, the protonated aziridine was not
observed, only the product of α-ring opening. In these cases
acyl exchange did not occur. Under identical conditions, cis- or
trans-1,3-diphenyl-2-trimethylsilylaziridine gave only a poly-
meric product.
A similar picture emerged with trifluoromethanesulfonic
The solvolysis of aziridinium salts is the only example of
nucleophilic attack β to the silicon atom that we have observed
with 2-trialkylsilylaziridines. We have been unable to find any
examples in the literature of a mechanistic difference between
N-methylated aziridinium salts and N-protonated aziridinium
salts. Indeed, we have found examples of protonated and
methylated 2,2-dialkylaziridines exhibiting attack at either
centre, depending upon the conditions.20 The delicate balance
between stabilisation of the incipient carbocation and attack at
the α carbon is illustrated by the reaction of 1-ethoxycarbonyl-
2-trimethylsilylaziridine with methyl trifluoromethylsulfonate,
which only gave the products of α addition. In this case, despite
potential β stabilisation by the silicon, the formation of a pri-
mary carbocation, leads to a preference for SN2 substitution.
The reaction of cis-1-methyl-3-phenyl-1-propyl-2-trimethylsilyl-
aziridinium triflate with other nucleophiles such as methylmag-
nesium bromide, halides and cyanide led to a complex mixture
of desilylated products. However, phenylacetaldehyde could be
detected in up to 34% yield. This is presumably formed by
desilylation to give the enamine followed by hydrolysis, as
shown in Scheme 4.
acid. cis-3-Phenyl-1-propyl-2-trimethylsilylaziridine gave
a
protonated aziridinium salt, whereas, 1-ethoxycarbonyl-2-
trimethylsilylaziridine gave the product of α addition. Reaction
of 2-methoxycarbonyl-2-dimethylphenylsilyl-1-phenylaziridine
with trifluoromethanesulfonic acid gave the enamine 6, arising
from attack of the nucleophile at the silicon atom, as shown in
Scheme 3.
Scheme 3
The reaction of aziridines with acid to give stable aziridinium
salts can be used to resolve chiral aziridines. Protonation
of cis-3-phenyl-1-propyl-2-trimethylsilylaziridine using the
homochiral acid (S)-(ϩ)-1,1Ј-binaphthyl-2,2Ј-diylhydrogen
phosphate gave a white solid that could be fractionally
recrystallised to give samples of the two diastereoisomeric salts.
Reaction with triethylamine gave the free aziridines as a pair of
optical isomers. The optical rotation was found to be 92Њ.
Ring opening reactions with methylating agents
Scheme 4
Methylation of 2-trialkylsilylaziridines using methyl iodide
was unsuccessful, however, the alkyl aziridinium salt of cis-3-
phenyl-1-propyl-2-trimethylsilylaziridine could be prepared
in moderate yield using methyl trifluoromethanesulfonate.
Methylation is much slower than protonation and thus is
Ring opening reactions with trialkylsilylhalides
The reaction of 1-ethoxycarbonyl-2-trimethylsilylaziridine and
1-phenyl-2-trimethylsilylaziridine with trialkylsilyl bromide,
J. Chem. Soc., Perkin Trans. 1, 2000, 439–448
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chloride and iodide gave the corresponding β-haloamines. This
was achieved using either stoichiometric or catalytic quantities
of the reagent. Presumably N-silylation to give the salt is fol-
lowed by attack of the iodide at the carbon α to the silicon.
However, cis-3-phenyl-1-propyl-2-trimethylsilylaziridine and
cis and trans-1,3-diphenyl-2-trimethylsilylaziridine reacted with
trialkylsilylhalides to give a trans-N-silylenamine, as shown in
Scheme 5.
Scheme 7
R2 = Ph, Pr or CO2Et) with subsequent trapping by a carbonyl
compound proved impossible, as was observed for the replace-
ment with a hydrogen. Whilst fluorodesilylation of 2-ethoxy-
carbonyl-1-phenyl-2-dimethylphenylsilylaziridine followed by
protonation was quite simple, subsequent trapping with a
carbonyl compound was not straightforward. This was because
of preferential protonation by water that was present in the
fluoride source. However, when very dry sources of tetrabutyl-
ammonium fluoride23–25 were employed, reaction with hexanal
or benzaldehyde could be observed. The product was a mixture
of the free alcohol and the corresponding silyl ether. In both
cases a 1:1 mixture of diastereoisomers was obtained. Reaction
was not observed with ketones, including cyclohexanone, which
led to aldol products. Presumably in such cases nucleophilic
attack at the carbonyl is hindered such that the aziridinyl
anion or fluoride ion preferentially acts as a base. Similarly, no
addition was observed with the hindered aldehyde 2,2-dimethyl-
ethanal or ethanal and propanal which underwent trimeriz-
ation.
Scheme 5
This difference in behaviour highlights again the directing
effect of the phenyl group in these systems. The aromatic group
stabilises the development of an adjacent positive charge, which
in turn, favours desilylation. No reaction was observed with
other trimethylsilyl halides, azides or cyanides.
The reaction of trimethylsilyltrifluoromethanesulfonate with
2-ethoxycarbonyl-1-phenyl-2-trimethylsilylaziridine did not
lead to ring opening but gave the silylated aziridinium salt 10.
Fluorodesilylation reactions of 2-trialkylsilylaziridines
Two mechanisms can be proposed for the desilylation and
concomitant reaction with the aldehyde or proton, as shown in
Scheme 8. Firstly fluoride ion could attack the silicon to form
trans-1,3-Diphenyl-2-trimethylsilylaziridine reacts with fluoride
ion to give the desilylated product rather than a ring opened
product, as shown in Scheme 6. Such behaviour is well
Scheme 6
documented for the corresponding 2-trialkylsilylepoxides.21
However, we found that fluorodesilylation of other 2-trialkyl-
silylaziridines was not an easy reaction to perform and this
was the only simple aziridine, 11, (R1 = H or Ph, R2 = Ph, Pr or
CO2Et) to undergo such a reaction. Alkali metal fluorides and
tetrabutylammonium fluoride were employed under a range of
conditions, including rigorous drying,22–25 however no reaction
was observed.
Desilylation of 2-ethoxycarbonyl-1-phenyl-2-trimethylsilyl-
aziridine potentially leads to a stabilised anion and thus might
be expected to occur more readily than with simple aziridines.
In fact fluorodesilylation of 2-ethoxycarbonyl-1-phenyl-2-
trimethylsilylaziridine took place easily and rigorous drying
was not necessary. Replacement of the trialkylsilyl group with a
dialkylphenylsilyl group has been shown to promote desilyl-
ation.26 We thus prepared 2-ethoxycarbonyl-2-dimethylphenyl-
silyl-1-phenylaziridine. This underwent fluorodesilylation even
more readily than the trimethylsilyl analogue.
Atkinson has desilylated the 2-trimethylsilylaziridine 12
using caesium fluoride.27 Under his conditions two products
were obtained, as shown in Scheme 7, the simple desilylation
product, 13, and a rearranged compound, 14, formed via
the intermediate azirine. This was confirmed by repeating the
reaction in the presence of benzaldehyde, which traps the
intermediate aziridinyl carbanion. We found that formation of
such carbanions from the simple aziridines, (11, R1 = H or Ph,
Scheme 8
trialkylsilyl fluoride and a free aziridinyl carbanion. This then
attacks the carbonyl compound. Alternatively, fluoride ion
could attack the silicon to generate a pentacoordinate silicon,
which subsequently attacks the carbonyl compound. Similar
free carbanion28 and pentacoordinate29 mechanisms have been
proposed for fluorodesilylation of allyltrialkylsilanes. A nucleo-
philic pentacoordinate silicon species has also been suggested
for group transfer polymerisation.30 Paquette et al. have shown
that fluorodesilylation of 1-trimethylsilylcyclopropane methyl
ketone in the presence of benzaldehyde leads to a mixture of 15
and 16. This suggests the formation of the free carbanion which
undergoes equilibration.31
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We found that both 2-ethoxycarbonyl-1-phenyl-2-dimethyl-
phenylsilylaziridine and 2-ethoxycarbonyl-1-phenyl-2-tri-
ring opened H’s) and 7.20–7.74 (7H, m, Ph, NH2ϩ, exchange-
able with D2O); δC (100 MHz, CDCl3, Me4Si) Ϫ2.47 (SiMe3),
11.03 (CH3/Pr), 18.79 (CH2CH3Pr), 42.62 (CBr), 47.16 (NCH2),
67.04 (PhCN), 129.48 (C-2 & C-6/Ph), 129.83 (C-4/Ph), 130.69
(C-3 & C-5/Ph) and 131.73 (C-1/Ph); m/z (EI) 298 (M Ϫ CH3 Ϫ
HBr, 0.41%), 255 (M Ϫ NHC3H7 Ϫ HBr, 0.46), 190 (C11H16-
NSi, 14.6), 160 (C11H14N, 13.6), 148 (PhCHNHPr, 100), 80
(HBr, 25) and 73 (SiMe3, 74) (Found: C, 42.5; H, 7.3; N, 3.6.
C14H25Br2NSi requires C, 42.2; H, 7.3; N, 3.5%).
methylsilylaziridine underwent desilylation in the presence of a
proton donor, although the latter reaction occurred more
slowly. However whilst 2-ethoxycarbonyl-1-phenyl-2-dimethyl-
phenylsilylaziridine underwent desilylation with attack on a
carbonyl compound, no such reaction was observed with
2-ethoxycarbonyl-1-phenyl-2-trimethylsilylaziridine. If reaction
occurred via a free carbanion, the same intermediate aziridinyl
anion would be formed in each case so the absence of reaction
with the carbonyl is hard to explain. This suggests reaction
occurs via a pentacoordinate species.
1-Bromo-2-phenyl-2-propylamino-1-trimethylsilylethane
hydrobromide. Method B; gaseous hydrogen bromide was
sparged very slowly through a solution of cis-3-phenyl-1-
propyl-2-trimethylsilylaziridine (0.30 g, 1.29 mmol) in carbon
tetrachloride (5 ml). The reaction was monitored by 1H
NMR analysis. After sparging for 5 min, the reaction mixture
Experimental
Melting points were determined on a Buchi 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 deu-
terochloroform with tetramethylsilane as internal standard 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.
afforded
1-bromo-2-phenyl-2-propylamino-1-trimethylsilyl-
ethane hydrobromide (0.4 g, 72%) on filtration and washing
with hexane. The product was confirmed by comparison of its
spectra with those of an authentic sample.
1-Iodo-2-phenyl-2-propylamino-1-trimethylsilylethane.
An
aqueous solution of hydrogen iodide (57% w/v) (2.2 ml, 9.59
mmol) was added dropwise to cis-3-phenyl-1-propyl-2-
trimethylsilylaziridine (0.75 g, 3.20 mmol) in a 25 ml, 3-necked
flask. The solution was stirred at room temperature (3¹ h).
¯
²
Dichloromethane (10 ml) was added and the solution was
washed with a saturated solution of sodium hydrogen carbon-
ate. The organic layer was extracted with dichloromethane and
again washed with sodium hydrogen carbonate solution. A
brown viscous semi-solid was obtained after drying over
anhydrous magnesium sulfate and removal of the solvent.
Attempts to purify the product, 1-iodo-2-phenyl-2-propyl-
amino-1-trimethylsilylethane, using a silica column failed due
to its decomposition; νmax(neat)/cmϪ1 3390, 1625, 1510–1400,
1340, 1270, 1200–1050, 1075, 1030, 900–850, 770, 760 and 710–
670; δH (400 MHz, CDCl3, Me4Si) Ϫ0.12 (9H, s, SiMe3), 0.90
(3H, t, CH3/Pr), 1.95 (2H, sextet, CH2CH3/Pr), 2.80 (2H, m,
CH2N), 4.39 (1H, d, JAB 12.0, CH), 4.75 (1H, d, JAB 12.0, CH)
and 7.43–8.00 (6H, m, Ph & 1H from NH exchangeable with
D2O); δC (100 MHz, CDCl3, Me4Si) Ϫ1.09 (SiMe3), 11.03 (CH3/
Pr), 19.30 (NCH2CH2CH3), 23.32 (CI), 47.97 (NCH2), 68.13
(Ph–CN), 129.54 (C-2 & C-3/Ph), 130.06 (C-4/Ph), 130.98 (C-3
& C-5/Ph) and 131.38 (C-1/Ph).
Ring opening with hydrogen halides
1-Chloro-2-phenyl-2-propylamino-1-trimethylsilylethane
hydrochloride. Method A; the reaction was carried out using
aqueous hydrogen chloride (36% w/v) (0.60 ml, 5.66 mmol) and
cis-3-pheny1-1-propyl-2-trimethylsilylaziridine (0.44 g, 1.89
mmol) in dichloromethane (10 ml). The reaction mixture
afforded
1-chloro-2-phenyl-2-propylamino-1-trimethylsilyl-
ethane hydrochloride on filtration and washing with hexane
(0.23 g, 45.7%), mp 196–198 ЊC; νmax (Nujol)/cmϪ1 2540–2270,
1590, 1250, 850, 740 and 700; δH (400 MHz, CDCl3, Me4Si)
Ϫ0.26 (9H, s, SiMe3), 0.79 (3H, t, CH3/Pr), 1.82 (2H, m,
CH2CH3/Pr), 2.60 (12H, m, CH2N/Pr), 4.27 (2H, d, J 4.7, ring
H’s) and 7.26–7.68 (7H, m, Ph, NH2ϩ exchangeable with D2O);
δC (100 MHz, CDCl3, Me4Si) Ϫ3.20 (SiMe3), 11.20 (CH3/Pr),
18.84 (CH2CH2CH3), 46.99 (N–CH2), 50.50 (CCl), 66.87
(Ph–CN), 128.97 (C-2 & C-6/Ph), 129.54 (C-4/Ph), 129.83
(C-3 & C-5/Ph) and 130.58 (C-1/Ph); m/z (EI) 254 (M Ϫ HCl Ϫ
CH3, 0.27%), 211 (M Ϫ NHC3H7 Ϫ HCl, 0.28), 190 (C11H16-
NSi, 2.46), 160 (C11H14N, 2.36), 148 (PhCHNHPr, 100), 73
(SiMe3, 21), 36 (HCl, 13) and 28 (Si, 22) (Found: C, 54.0; H, 9.3;
N, 4.6. C14H25Cl2NSi requires C, 54.2; H, 9.4; N, 4.5%).
2-Anilino-1-chloro-2-phenyl-1-trimethylsilylethane. The reac-
tion was carried out using gaseous hydrogen chloride and cis-
l,3-diphenyl-2-trimethylsilylaziridine (0.25 g, 0.93 mmol) in
carbon tetrachloride (5 ml). After 3 min, the reaction mixture
gave solid white 2-anilino-l-chloro-2-phenyl-l-trimethylsilyl-
ethane hydrochloride on filtration and washing with hexane
(0.l5 g, 38%), mp 179–181 ЊC; νmax (Nujol)/cmϪ1 2750–2400,
1610–1590, 1500, 1250, 860, 830, 800 and 700; δH (400 MHz,
CDCl3, Me4Si) Ϫ0.20 (9H, s, SiMe3), 4.50 (2H, s, ring-opened
H’s) and 7.00–7.60 (12H, m, Ph–NH2, exchangeable with D2O);
δC (100 MHz, CDCl3, Me4Si) Ϫ2.99 (SiMe3), 49.40 (C–SiMe3),
73.65 (CPh), 124.95 (C-2 & C-6/Ph), 128.39 (C-2 & C-6/NPh),
128.91 (C-4/Ph), 129.54 (C-4/NPh), 130.00 (C-3 & C-5/Ph),
131.09 (C-3 & C-5/NPh), 131.67 (C-1/Ph) and 133.97 (C-1/NPh);
m/z (EI) 303 (C17H23Cl2NSi, 4.2%), 267 (C17H21NSi, 1.2), 194
1-Chloro-2-phenyl-2-propylamino-1-trimethylsilylethane
hydrochloride. Method B; the reaction was carried out using
excess gaseous hydrogen chloride and cis-3-phenyl-1-propyl-
2-trimethylsilylaziridine (0.30 g, 1.29 mmol) in carbon tetra-
chloride (5 ml). On filtration and washing with hexane, the
reaction mixture gave white l-chloro-2-phenyl-2-propylamino-
1-trimethylsilylethane hydrochloride (0.3 g, 76%). The product
was confirmed by comparison of spectra with those of an
authentic sample.
1-Bromo-2-phenyl-2-propylamino-1-trimethylsilylethane
hydrobromide. Method A; the reaction was carried out using
an aqueous solution of hydrogen bromide (46% w/v) (1.3 ml,
7.46 mmol), cis-3-phenyl-1-propy1-2-trimethylsilylaziridine
(0.58 g, 2.49 mmol) in dichloromethane (10 ml). The reaction
afforded white l-bromo-2-phenyl-2-propylamino-1-trimethyl-
silylethane hydrobromide on filtration and thorough washing
with hexane (0.65 g, 83%), mp 198–200 ЊC; νmax (Nujol)/cmϪ1
2520–2270, 1580, 1220, 1100, 850, 765 and 700; δH (400 MHz,
CDCl3, Me4Si) Ϫ0.20 (9H, s, SiMe3), 0.75 (3H, t, CH3/Pr), 1.70
(2H, sextet, CH2CH3/Pr), 2.65 (2H, m, CH2N/Pr), 4.30 (2H, s,
(C H NSi–SiMe or C H N, 5.2), 182 (PhCH᎐NHPh, 100),
᎐
17 21
3
14 12
77 (Ph, 9.8) and 73 (SiMe3, 20.9) (Found: C, 67.0; H, 7.5; N, 4.5.
C17H23Cl2NSi requires C, 67.0; H, 7.6; N, 4.6%).
The supernatant was concentrated to dryness to give solid
light-brown 2-anilino-1-chloro-2-phenyl-1-trimethylsilylethane
on washing with hexane (0.12 g, 60%), mp 75–76 ЊC; νmax
(Nujol)/cmϪ1 3420, 3100–3020, 2960–2840, 1600, 1510, 1450,
1430, 1320, 1250, 920–700 and 800–700; δH (400 MHz, CDCl3,
Me4Si) 0.04 (9H, s, SiMe3), 3.60 (1H, d, J 3.9, ring-opened H’s),
4.70 (1H, d, J 3.9, ring opened H’s) and 6.40–7.30 (11H, m,
J. Chem. Soc., Perkin Trans. 1, 2000, 439–448
443

View Online
PhNH2ϩ, exchangeable with D2O); δC (100 MHz, CDCl3,
Me4Si) Ϫ2.64 (SiMe3), 57.19 (C–SiMe3), 58.83 (CPh), 113.63
(C-2 & C-6/Ph), 117.94 (C-2 & C-6/NPh), 126.96 (C-4/Ph),
127.48 (C-4/ NPh), 128.40 (C-3 & C-5/Ph), 129.20 (C-3 & C-5/
NPh) and 140.98 (C-1/Ph) (Found: C, 67.1; H, 7.3; N, 4.6.
C17H22ClNSi requires C, 67.2; H, 7.3; N, 4.6%).
55%); δH (100 MHz, CDCl3, Me4Si) Ϫ0.008 (9H, s, SiMe3), 1.08
(3H, CH3), 3.10–3.96 (3H, m, CH2CH) and 5.02 (2H, br s, NH2);
δC (400 MHz, CDCl3, Me4Si) Ϫ3.5 (SiMe3), 14.6 (CH3), 44.3
(CSi), 51.4 (CN), 60.9 (CH O) and 156.4 (C᎐O) (Found: C,
᎐
2
36.8; H, 6.9; N, 5.3. C8H19NO2SiCl2 requires C, 36.9; H, 7.3; N
5.4%).
2-Anilino-1-bromo-2-phenyl-1-trimethylsilylethane. The reac-
tion was carried out using gaseous hydrogen bromide and cis-3-
phenyl-1-propyl-2-trimethylsilylaziridine (0.20 g, 0.75 mmol) in
carbon tetrachloride (5 ml). After 8 min, the pale yellow solu-
tion was concentrated to dryness and washed with hexane to
afford a cream-coloured solid, 2-anilino-l-bromo-2-phenyl-1-
trimethylsilylethane (0.20 g, 76%), mp 101–102 ЊC; νmax (Nujol)/
cmϪ1 3400, 1600, 1580, 1250 and 915-680; δH (400 MHz, CDCl3,
Me4Si) 0.20 (9H, s, SiMe3) 3.70 (1H, d, J 3.0, ring-opened H’s),
4.70 (1H, d, J 3.0, ring-opened H’s) and 6.50–7.30 (11H, m, Ph–
NH); δC (100 MHz, CDCl3, Me4Si) Ϫ2.07 (SiMe3), 52.27
(CSiMe3), 58.36 (C-Ph), 113.80 (C-2 & C-6/Ph), 118.11 (C-2
& C-6/NPh), 126.85 (C-4/Ph), 127.43 (C-4/NPh), 128.39 (C-3
& C-5/Ph), 129.25 (C-3 & C-5/NPh), 141.26 (C-1/Ph) and 145.45
(C-1/NPh); m/z (EI) 347 (C17H22BrNSi, 3.8%), 267 (M Ϫ HBr
or C17H21NSi, 2.2), 194 (C17H21NSi Ϫ SiMe3 or C14H21N, 6.7),
Ethyl N-(2-bromo-2-trimethylsilylethyl)carbamate. This reac-
tion was carried out using the same procedure as for the ring
opening reaction of 1-ethoxycarbonyl-2-trimethylsilylaziridine
with hydrogen chloride to give the ring opened carbamate
product in 52% yield; δH (400 MHz, CDCl3, Me4Si) 0.11 (9H, s,
SiMe3), 1.21 (3H, t, CH3), 3.24–3.80 (3H, m, CH2CHSi), 4.09
(2H, q, CH2O) and 7.12 (1H, br s, NH); δC (400 MHz, CDCl3,
Me4Si) Ϫ3.2 (SiMe3), 14.4 (CH3), 43.7 (CSi), 44.0 (CH2N), 60.8
(CH O) and 156.2 (C᎐O) (Found: C, 35.9; H, 6.8; N, 5.2.
᎐
2
C8H18NO2SiBr requires C, 35.8; H, 6.8; N, 5.2%).
Reaction of 2-ethoxycarbonyl-1-phenyl-2-triethylsilylaziridine
with hydrogen chloride and hydrogen bromide. 2-Ethoxy-
carbonyl-1-phenyl-2-triethylsilylaziridine (0.1 g, 0.00343 mmol)
was dissolved in 1 ml dry ether and hydrogen chloride or hydro-
gen bromide was passed through the solution for a few seconds.
The mixture was evaporated leaving a brown oil. This was puri-
fied by column chromatography using 10:1 pentane–ether as
the eluent. The only product which could be recovered was a
white solid which could be identified as aniline hydrochloride
by NMR spectroscopy.
182 (PhCH᎐NHPh, 100), 77 (Ph, 8.6) and 73 (SiMe , 22.3)
᎐
3
(Found: C, 58.5; H, 6.3; N, 4.0. C17H22BrNSi requires C, 58.6;
H, 6.4; N, 4.0%).
2-Amino-1-chloro-2-phenyl-1-trimethylsilylethane
hydro-
chloride. cis-3-Phenyl-2-trimethylsilylaziridine (0.1 g, 0.524
mmol) was placed in a 5 ml NMR tube with 1 ml CDCl3 and
hydrogen chloride was passed through the solution. After 1
second of purging, the NMR spectrum of the reaction mixture
indicated the presence of an aziridinium salt and also that of a
ring opened product. After several seconds of purging with the
gas, the product consisted entirely of the ring opened derivative.
The solvent was evaporated and the remaining off-white solid
was recrystallized from 50:50, ether–chloroform to give white
crystals of 2-amino-1-chloro-2-phenyl-1-trimethylsilylethane
hydrochloride (0.133 g, 0.504 mmol, 96.2%). The solid
decomposed without melting on heating; δH (400 MHz, CDCl3,
Me4Si) Ϫ0.18 (9H, s, SiMe3), 3.85 (1H, d, J 10.5, CHSi), 4.28
(1H, d, J 10.5, CHPh), 6.33 (3H, s, NH3, exchangeable with
H2O) and 7.25–7.40 (5H, m, Ph); δC (100 MHz, CDCl3, Me4Si)
Ϫ3.0 (SiMe3), 51.2 (CSiMe3), 61.0 (CPh), 128.8, 129.4, 130.0
and 133.9 (Ph).
Ring opening reactions with other acids
cis-3-Phenyl-1-propyl-2-trimethylsilylaziridinium
trifluoro-
acetate. A solution of trifluoroacetic acid (0.25 g, 2.10 mmol) in
diethyl ether (2 ml) was cooled in an ice–methanol bath at
Ϫ11 ЊC. A pre-cooled solution of cis-3-phenyl-1-propyl-2-
trimethylsilylaziridine (0.50 g, 2.10 mmol) in diethyl ether (5 ml)
was added dropwise to the trifluoroacetic acid solution. The
mixture was stirred under nitrogen at Ϫ11 ЊC (¹ h). The reaction
¯
²
mixture was allowed to warm up to room temperature and
stirred for another ¹ h at this temperature. The reaction mixture
¯
²
was concentrated to dryness to give cis-3-phenyl-1-propyl-2-
trimethylsilylaziridinium trifluoroacetate as a yellow oil (98%
1
based on H NMR); νmax(neat)/cmϪ1 3300–2800, 1700, 1210–
1130, 850, 730 and 700; δH (400 MHz, CDCl3, Me4Si) 0.21 (9H,
s, SiMe3), 1.22 (3H, t, CH3/Pr), 2.13 (2H, m, CH2CH3/Pr),
2.52 (1H, d, J 9.5, ring H), 3.49 (2H, m, CH2N), 4.48 (1H, d,
J 9.5, ring H), 7.65 (5H, m, Ph) and 8.40 (1H, broad singlet, NH
exchangeable with D2O); δC (100 MHz, CDCl3, Me4Si) Ϫ3.62
(SiMe3), 9.71 (CH3/Pr), 20.16 (CH2CH3/Pr), 43.74 (CHSiMe3),
50.71 (CHPh), 58.65 (CH2N), 126.15, 127.91, 128.91 and 129.48
(C’s/Ph), 157.87, 159.65, 161.43 and 163.20 (CF3COO) (Found:
C, 55.1; H, 6.8; N, 3.8. C16H24F3NO2Si requires C, 55.3; H, 7.0;
N, 4.0%).
2-Amino-1-bromo-1-trimethylsilylhexane hydrobromide. The
reaction was carried out as before, using 0.2 g of trans-3-butyl-
2-trimethylsilylaziridine and gaseous hydrogen bromide. The
proton NMR spectrum of the product obtained from the reac-
tion is consistent with 2-amino-1-bromo-1-trimethylsilylhexane
hydrobromide. An attempt to purify this product further
resulted in decomposition; δH (400 MHz, CDCl3, Me4Si) 0.24
(9H, s, SiMe3), 1.62–1.95 (9H, m, CH3CH2CH2CH2), 4.00 (1H,
d, J 2.0, CHBr), 4.36 (1H, dt, J 2.0 and 6, CHN) and 7.92 (3H, s,
NH3).
The reaction was carried out using deuterated chloroform,
dimethoxyethane, methanol and hexane–diethyl ether (11:1).
All systems gave cis-3-phenyl-1-propyl-2-trimethylsilylaziridin-
ium trifluoroacetate.
Ethyl N-(2-chloro-2-trimethylsilylethyl)carbamate hydro-
chloride. 1-Ethoxycarbonyl-2-trimethylsilylaziridine (0.3 g,
1.60 mmol) was placed in a 5 mm NMR tube with 1 ml of
deuterochloroform and the tube cooled in an ice bath. Hydro-
gen chloride was passed through the solution until all of the
aziridine had been consumed, the reaction being followed by
proton NMR spectroscopy. On evaporation of the solvent, a
brown oil was obtained which was purified by column chrom-
atography on silica using 3:10 ether–hexane as the eluent. A
colourless oil was obtained which was insoluble in hexane. This
yielded, after several recrystallization steps, pure, well defined
crystals of the ring opened product, ethyl N-(2-chloro-2-tri-
methylsilylethyl)carbamate hydrochloride (0.23 g, 0.885 mmol,
2-(N-Propyltrifluoroacetamido)-2-phenyl-1-trimethylsilyl-
ethanol. A solution of trifluoroacetic acid (0.25 g, 2.10 mmol) in
diethyl ether (2 ml) was added to a solution of cis-3-phenyl-1-
propyl-2-trimethylsilylaziridine (0.25 g, 2.10 mmol) in diethyl
ether (5 ml). The reaction mixture was heated under reflux at
60 ЊC (1 h) and was concentrated to dryness to yield white 2-(N-
propyltrifluoroacetamido)-2-phenyl-1-trimethylsilylethanol
(13.5%), mp 115–116 ЊC; νmax (Nujol)/cmϪ1 3150, 1675, 1640,
1140, 850, 765 and 720; δH (400 MHz, CDCl3, Me4Si) Ϫ0.27
(9H, s, SiMe3), 0.84 (3H, t, CH3/Pr), 1.70 (2H, m, CH2CH3/Pr),
2.50 (2H, m, CH2N), 3.84 (1H, d, J 12.0, ring opened H’s),
4.20 (1H, d, J 12.0, ring opened H’s) and 7.47 (6H, broad
444
J. Chem. Soc., Perkin Trans. 1, 2000, 439–448

View Online
singlet, Ph & OH, exchangeable with D2O); δC (100 MHz,
CDCl3, Me4Si) Ϫ3.79 (SiMe3), 10.86 (CH3/Pr), 19.24 (CH2-
CH3/Pr), 46.82 (C-Ph), 66.12 (NCH2), 67.33 (CF3), 128.85
(C-2 & C-6/Ph), 129.60 (C-4/Ph), 130.17 (C-3 & C-5/Ph), 131.95
firmed by comparison of its spectra with those of an authentic
sample.
cis-3-Phenyl-1-propyl-2-trimethylsilylaziridiniun (S)-(؉)-1,1Ј-
(C-1/Ph) and 161.00 (C᎐O); δ (400 MHz, CDCl3) Ϫ76.39
binaphthyl-2,2Ј-diyl phosphate. A solution of cis-3-pheny1-1-
propyl-2-trimethylsilylaziridine (0.20 g, 0.86 mmol) in meth-
anol (0.5 ml) was added to a suspension of (S)-(ϩ)-1,1Ј-
binaphthyl-2,2Ј-diyl hydrogen phosphate ((ϩ)-BNPA) (0.30 g,
0.86 mmol) in methanol (2 ml) under nitrogen. The pale
reaction mixture was allowed to stir at room temperature (2 h).
The solution was concentrated to dryness to give a white
crystalline solid (0.40 g, 44%). Fractional crystallisation from
absolute ethanol afforded enantiomeric cis-3-phenyl-1-propyl-
᎐
F
(s); m/z (EI) 177 (PhCH–CHSiMe3, 12%), 148 (PhCHNHPr,
100), 77 (Ph), 73 (SiMe3, 40), 28 (Si, 47) (Found: C, 55.1;
H, 7.4; N, 4.2. C16H24F3NO2Si requires C, 55.3; H, 7.0; N,
4.0%).
Ethyl
N-(2-trifluoroacetyl-2-trimethylsilylethyl)carbamate.
The reaction was carried out using 1-ethoxycarbonyl-2-
trimethylsilylaziridine (0.1 g, 0.535 mmol) and trifluoroacetic
acid (0.6 g, 0.04 ml, 0.535 mmol) leading quantitatively
(by NMR spectroscopy) to the ring opened product, ethyl
N-(2-trifluoroacetyl-2-trimethylsilyl)carbamate; δH (400 MHz,
CDCl3, Me4Si) 0.07 (9H, s, Me3Si), 1.23 (2H, t, CH3), 3.41 (1H,
d, J 8.30, NCHaHb), 3.49 (1H, d, J 4.88, NCHaHb), 4.06 (2H, t,
CH2CH3), 4.99 (1H, dd, J 8.30 and 4.88, CHSiMe3) and 5.90
(1H, br s, NH); δC (100 MHz, CDCl3, Me4Si) Ϫ4.2 (Me3Si),
14.2 (CH3), 41.7 (NCH2), 61.1 (CH2CH3), 74.2 (CSi) 119.4 (q,
CF ) and 156.8 (C᎐O); m/z (EI) 301 (Mϩ, 0.2%) 229 (2.9%)/230/
2-trimethylsilylaziridiniun
(S)-(ϩ)-1,1Ј-binaphthyl-2,2Ј-diyl
phosphate; δH (400 MHz, CDCl3, Me4Si) Ϫ0.30 (9H, s, SiMe3),
0.60 (3H, t, CH3/Pr), 1.20–1.90 (3H, m (including one d at 1.70,
J 9.0), CH2/Pr and ring opened H’s), 2.50–2.90 (2H, m, CH2N),
3.80 (1H, d, J 9.0, ring opened H’s), 7.00–8.00 (18H, m, Ph
(5H), BNPA (12H) and NϩH (1H)); δC (100 MHz, CDCl3,
Me4Si) Ϫ2.41 (SiMe3), 10.63 (CH3/Pr), 20.34 (CH2CH3/Pr),
40.90 (N–CH2), 49.00 (CSiMe3), 59.34 (CPh), 121.96, 124.54,
125.87, 127.01, 127.24, 128.39, 129.94, 130.98, 132.53, 149.19
and 149.53 (C’s/aromatic rings).
᎐
3
231 (9:2:1, Mϩ Ϫ SiMe3 or CO2Et), 188 (Mϩ Ϫ O2CCF3,
1.9%), 116 (44.9%)/117/118 (9:2:1), 101 (83.2%)/l02/l03
(77:11:7), 73 (SiMe3 or CO2Et, 86.8%), 69 (55.6%)/70/71
(88:6:5, CF3), 59 (38.6) and 29 (Et, 100.0%).
(؉)-cis-3-Phenyl-1-propyl-2-trimethylsilylaziridine.
A solu-
tion of cis-3-phenyl-1-propyl-2-trimethylsilylaziridiniun (S)-
(ϩ)-1,1Ј-binaphthyl-2,2Ј-diyl phosphate (0.10 g, 0.17 mmol) in
Methyl 2-anilino-1-trifluoroacetyl-1-triethylsilylpropanoate.
The reaction was carried out using 2-methoxycarbonyl-l-
phenyl-2-triethylsilylaziridine (0.11 g, 0.378 mmol) and tri-
fluoroacetic acid (0.043 g, 0.378 mmol). The major product
from this reaction was the ring opened species, methyl 2-
anilino-1-trifluoroacetyl-1-triethylsilylpropanoate which began
to decompose within a few hours; δH (400 MHz, CDCl3, Me4Si)
0.56–0.62 (6H, m) and 0.9–1.0 (9H, m), (SiEt3), 2.49 (1H, s,
NCHaHb), 2.84 (1H, s, NCHaHb), 3.45 (3H, s, CH3) and 6.85–
7.29 (5H, m, Ph); δC (100 MHz, CDCl3, Me4Si) 3.2 (3 × SiCH2-
CH3), 7.9 (3 × SiCH2CH3), 35.9 (NCH2), 52.7 (CH3), 73.4
(COCOCF3), 120.9, 123.6, 128.7 and 148.1 (Ph) and 171.2
dichloromethane (3 ml) was shaken with triethylamine (3 ml).
The mixture was left to stand (4 h). On addition of hexane
1
–
(5 ml), the reaction mixture afforded a white precipitate, which
was removed by filtration. The filtrate was concentrated to
dryness to give (ϩ)-cis-1-propyl-2-trimethylsilyl-3-phenylazir-
idine (0.038 g, 0.16 mmol). The product was confirmed by
comparison of its spectra with those of an authentic sample.
The angular rotation at 19 ЊC and path length, 1 dm, (sodium
D line as reference) for a solution of 0.76 g of (ϩ)-cis-1-propyl-
2-trimethylsilyl-3-phenylaziridine in 100 ml ethanol was
19
measured as [α] = ϩ92.5Њ.
589
(C᎐O).
᎐
cis-1-Methyl-3-phenyl-1-propyl-2-trimethylsilylaziridinium
trifluoromethanesulfonate. Methyl trifluoromethanesulfonate
(0.46 g, 2.80 mmol) was syringed dropwise into a solution of
cis-3-phenyl-1-propyl-2-trimethylsilylaziridine (0.65 g, 2.80
mmol) in carbon tetrachloride (1.5 ml) at room temper-
ature under nitrogen. The solution was vigorously stirred
and a white precipitate was formed instantaneously. The
slurry was allowed to stand (16 h) and the white solid was
filtered off and washed with cold carbon tetrachloride and
hexane successively. This gave cis-1-methyl-3-phenyl-1-propyl-
2-trimethylsilylaziridinium trifluoromethanesulfonate (0.70 g,
58%), mp 122–124 ЊC; νmax (Nujol)/cmϪ1 1280, 1160, 1040, 850,
750 and 700; δH (400 MHz, CDCl3, Me4Si) 0.30 (9H, s, SiMe3),
1.00 (3H, t, CH3/Pr), 1.90 (2H, sextet, CH2CH3/Pr), 2.27 (3H, s,
CH3/CF3OSO2CH3), 3.10 (1H, d, J 10.5, ring H), 3.50 (2H, m,
CH2N), 4.70 (1H, d, J 10.5, ring H) and 7.43 (5H, m, Ph);
δC (100 MHz, CDCl3, Me4Si) Ϫ0.75 (SiMe3), 10.17 (CH3/Pr),
19.01 (CH2CH3/Pr), 40.44 (NCH3), 49.01 (CHSiMe3), 58.65
(CH–Ph), 67.67 (NCH2), 100.24, 114.49, 128.68 and 142.92
(CF3SO3Ϫ), 127.24 (C-2 & C-6/Ph), 129.31 (C-4/Ph), 129.71
(C-3 & C-5/Ph) and 130.58 (C-1/Ph); m/z (EI) 175 (M Ϫ
SiMe3 Ϫ CF3OSO2, 53%), 146 (M Ϫ SiMe3 Ϫ CF3OSO2 Ϫ
C2H5, 68), 91 (PhCH2, 24), 77 (Ph, 100) and 73 (SiMe3, 59)
(Found: C, 47.9; H, 6.6; N, 3.5; C16H26F3NO3SSi requires C,
48.3; H, 6.6; N, 3.5%).
cis-3-Phenyl-1-propyl-2-trimethylsilylaziridinium
trifluoro-
methanesulfonate. Trifluoromethanesulfonic acid (0.13 g, 0.86
mmol) was syringed dropwise into a solution of cis-3-phenyl-1-
propyl-2-trimethylsilylaziridine (0.20 g, 0.86 mmol) in meth-
anol (1 ml). A yellow solution was obtained after heating under
reflux at 65 ЊC (2 h). The product was confirmed by comparison
of its spectra with those of an authentic sample.
Ethyl
N-(2-trifluoromethanesulfonyl-2-trimethylsilylethyl)-
carbamate. The reaction was carried out using 1-ethoxy-
carbonyl-2-trimethylsilylaziridine (0.1 g, 0.535 mmol) and
trifluoromethanesulfonic acid (0.047 ml, 0.535 mmol). NMR
spectroscopy indicated immediate and quantitative conversion
to ethyl N-(2-trifluoromethanesulfonyl-2-trimethylsilylethyl)-
carbamate; δH (400 MHz, CDCl3, Me4Si) 0.12 (9H, s, Me3Si),
1.39 (3H, t, CH3), 3.78 (1H, dd, J 19.76 and 12.21, NHaHb), 4.16
(1H, dd, J 19.67 and 10.74, NHaHb), 4.57 (2H, q, CH2CH3),
5.01 (1H, dd, J 12.21 and 10.74, CHSi) and 9.96 (1H, s, NH);
δC (100 MHz, CDCl3, Me4Si) Ϫ5.2 (Me3Si), 13.7 (CH3), 45.2
(NCH2), 72.9 (CH2CH3), 81.9 (CSi), 119.6 (q, CF3) and 165.7
(C᎐O).
᎐
Methyl 2-anilinopropenoate. 2-Methoxycarbonyl-2-dimethyl-
phenylsilyl-1-phenylaziridine, (0.05 g, 0.161 mmol) was dis-
solved under nitrogen in 0.5 ml of deuterochloroform, in a 5
mm NMR tube, and cooled in an ice–methanol bath. Trifluoro-
methanesulfonic acid (0.0241 g, 0.161 mmol) was syringed
slowly into the tube. The reaction was followed by NMR
spectroscopy and complete conversion to methyl 2-anilino-
propenoate was observed after 2 hours. The product was con-
The specific conductance of a solution of the product (0.0387
g) in ethanol (10 ml) was measured using a stainless steel cell
and gave a k value of 3.96 × 10Ϫ2 ΩϪ1 cmϪ1 at 298.4 K.
Ethyl N-(2-triflato-2-trimethylsilylethyl)-N-methylcarbamate.
This was prepared using 1-ethoxycarbonyl-2-trimethylsilyl-
J. Chem. Soc., Perkin Trans. 1, 2000, 439–448
445

View Online
aziridine (0.13 g, 0.695 mmol) and methyl trifluoromethane-
sulfonic acid (0.115 g, 0.079 ml, 0.695 mmol). The ring opened
product was formed in almost quantitative yield by NMR
spectroscopy; δH (400 MHz, CDCl3, Me4Si) 0.42 (9H, s, Me3Si),
1.49 (3H, t, CH3), 2.90 (3H, s, NMe), 3.37 (1H, d, J 10.2, NCHa-
CHb), 3.39 (1H, d, J 7.1, NCHaHb), 4.31 (2H, q, CH2CH3), 4.91
(2H, dd, J 7.1 and 10.2, CHSi). The geminal coupling constant
is observed to be zero; δC (100 MHz, CDCl3, Me4Si) Ϫ5.1
(Me3Si), 13.7 (CH3), 31.2 (MeN), 50.8 (NCH2), 72.7 (CH2CH3),
Ethyl N-(2-bromo-2-trimethylsilylethyl)-N-trimethylsilylcarb-
amate. 1-Ethoxycarbonyl-2-trimethylsilylaziridine (0.1 g, 0.535
mmol) was placed in a 5 mm NMR tube with dry deutero-
chloroform, under nitrogen and the tube was cooled in an ice
bath. Trimethylsilyl bromide (0.082 g, 0.0707 ml, 0.535 mmol)
was syringed slowly into the sealed tube. An attempt to purify
the product resulted in decomposition, however, NMR spectra
indicated that almost complete conversion to the ring opened
product, ethyl N-(2-bromo-2-trimethylsilylethyl)-N-trimethyl-
silylcarbamate had been achieved. The product was confirmed
by comparison of its spectra with those of an authentic sample.
79.6 (CSi), 120 (q, CF ), 162.9 (C᎐O).
᎐
3
2-Methoxy-N-methyl-2-phenyl-N-propyl-2-trimethylsilylethyl-
amine. A solution of cis-1-propyl-2-trimethylsilyl-3-phenyl-N-
methylaziridinium trifluoromethanesulfonate (0.59 g, 1.49
mmol) in methanol (5 ml) was heated under reflux at 65 ЊC,
using a condenser fitted with a calcium chloride tube. After 4¹ h,
Ethyl
N-(2-iodo-2-trimethylsilylethyl)-N-trimethysilylcarb-
amate. This reaction was carried out as before using l-ethoxy-
carbonyl-2-trimethylsilylaziridine (0.1 g, 0.535 mmol) and
trimethylsilyl iodide (0.107 g, 0.0761 ml, 0.535 mmol). Again,
almost complete conversion to the ring opened product, ethyl
N-(2-iodo-2-trimethylsilylethyl)-N-trimethylsilylcarbamate
was achieved, but this could not be purified further; δH (400
MHz, CDCl3, Me4Si) 0.26 (9H, s, Me3SiC), 0.41 (9H s,
Me3SiN), 1.36 (3H, t, CH3), 3.05–3.40 (2H, m, CH2N) and 4.02
(2H, q, CH2O); δC (100 MHz, CDCl3, Me4Si) Ϫ2.3 (Me3SiC),
0.7 (Me3SiN), 14.2 (CH3CH2), 21.8 (CI), 47.4 (NCH2), 60.7
¯
²
water (10 ml) was added to the cooled mixture and extracted
with diethyl ether (3 × 10 ml). The ethereal solution was dried
over anhydrous magnesium sulfate. The filtered solution
was concentrated to dryness to afford a pale yellow liquid,
2-methoxy-N-methyl-2-phenyl-N-propyl-2-trimethylsilylethyl-
amine (0.21 g, 51%); one spot obtained by TLC using hexane as
eluent; νmax (neat)/cmϪ1 3100–2800, 1490, 1450, 1250, 1085, 950,
835 and 760–700; δH (400 MHz, CDCl3, Me4Si) Ϫ0.19 (9H, s,
SiMe3), 0.85 (3H, t, CH3/Pr), 1.17–1.87 (2H, m, CH2CH3/Pr),
2.47–2.87 (3H, s, N–CH3), (2H, m ϩ obscured d, NCH2 and
CHSiMe3), 3.07 (3H, s, OCH3), 3.39 (1H, d, J 10.0, CH(OMe))
and 7.30 (5H, s, Ph); δC (100 MHz, CDCl3, Me4Si) Ϫ0.63
(SiMe3), 11.50 (CH3/Pr), 21.37 (CH2CH3/Pr), 40.50 (N–CH3),
55.44 (OCH3), 66.61 (NCH2), 62.85 (CN(SiMe3)), 84.10 (CPh),
126.32 (C-2 & C-6/Ph), 127.76 (C-4/Ph), 128.28 (C-3 & C-5/Ph)
and 139.77 (C-1/Ph); m/z (EI) 247 (M Ϫ CH3OH, 4.0%), 206
(OCH ) and 157.2 (C᎐O).
᎐
2
Ethyl N-(2-chloro-2-trimethylsilylethyl)carbamate hydro-
chloride. This reaction was carried out as before using 1-ethoxy-
carbonyl-2-trimethylsilylaziridine (0.1 g, 0.535 mmol) and
trimethylsilyl chloride (0.058 g, 0.068 ml, 0.535 mmol). How-
ever, the reaction was much slower. Treatment of 1-ethoxy-
carbonyl-2-trimethylsilylaziridine with trimethylsilyl chloride
for several months eventually led to the formation of the hydro-
gen chloride ring opened product as determined by comparison
of the NMR spectra with those of an authentic sample.
(N Ϫ SiMe , 6.7), 158 (C H Ϫ Nϩ(CH )᎐CHSiMe , 100), 130
᎐
3
3
7
3
3
(CH Nϩ(CH )᎐CHSiMe , 16.0), 77 (Ph, 1.0), 73 (SiMe , 4.0)
᎐
3
3
3
3
and 28 (Si, 2.0) (Found: C, 68.8; H, 10.3; N, 4.4. C16H29ONSi
requires C, 68.8; H, 10.5; N, 5.0%).
trans-(N-Trimethylsilyl-N-propylamino)phenylstyrene.
A
solution of cis-1-propyl-2-trimethylsilyl-3-phenylaziridine (0.10
g, 0.43 mmol) in deuterated chloroform (3 ml) was syringed in a
5 mm NMR tube under nitrogen. A solution of trimethylsilyl
iodide (0.08 g, 0.43 mmol) in deuterated chloroform (0.2 ml)
was added dropwise to the solution of aziridine under nitrogen.
The NMR tube was shaken thoroughly and left to stand at
room temperature to give a yellowish-brown solution of
trans-(N-trimethylsilyl-N-propylamino)phenylstyrene (95% as
2-Methoxy-N-methyl-2-phenyl-N-propylethylamine. A solu-
tion of sodium methoxide (0.07 g, 1.28 mmol) in methanol (0.5
ml) was added dropwise to a solution of cis-1-propyl-2-
trimethylsilyl-3-phenyl-N-methylaziridinium trifluoromethane-
sulfonate (0.51 g, 1.28 mmol) in methanol (5 ml). The reaction
1
–
mixture was heated under reflux at 65 ЊC (1 h) using a
condenser fitted with a calcium chloride tube. Th4e yellow reac-
tion mixture was washed with distilled water (10 ml) and
extracted with diethyl ether (3 × 10 ml). The organic extracts
were again washed with distilled water (2 × 30 ml) and dried
over anhydrous magnesium sulfate. The filtered solution was
concentrated to dryness to afford a yellow liquid containing
unreacted aziridinium salt. The residual aziridinium salt was
precipitated using hexane, was filtered off and washed with
hexane (0.02 g). The filtrate and washings were concentrated
to dryness to afford a yellow liquid, 2-methoxy-N-methyl-2-
phenyl-N-propylethylamine (0.14 g, 53%); νmax (neat)/cmϪ1
3100–3025, 2960–2900, 2870–2800, 1490–1450, 1105, 755 and
700; δH (400 MHz, CDCl3, Me4Si) 0.90 (3H, t, CH3/Pr), 1.20–
1.80 (2H, m, CH2CH3/Pr), 2.30–2.90 (4H, m, ring-opened CH2
and CH2N/Pr), 3.1 (3H, s, N–CH3), 3.20 (3H, s, OCH3), 4.20–
4.40 (1H, dd, OCH) and 7.30 (5H, s, Ph); δC (100 MHz, CDCl3,
Me4Si) 11.84 (CH3/Pr), 20.10 (CH2CH3/Pr), 43.08 (N–CH3),
56.76 (OCH3), 60.26 (N–CH2/Pr), 64.57 (–C(OMe)–CH2N–),
82.15 (CH(OMe)), 126.73 (C-2 & C-6/Ph), 127.65 (C-4/Ph),
128.39 (C-3 & C-5/Ph) and 141.09 (C-1/Ph); m/z (EI) 176
(M Ϫ OCH3, 1.4%), 175 (M Ϫ CH3OH, 2.7), 162 (M Ϫ OCH3
Ϫ C2H4, 6.2), 146 (M Ϫ CH3OH, 4.4), 121 (PhCHOCH3, 3.5),
1
determined by H NMR); δH (400 MHz, CDCl3, Me4Si) 0.23
(9H, s, SiMe3), 0.70 (3H, t, CH3/Pr), 1.60 (2H, sextet, CH2CH3/
Pr), 3.10 (2H, t, CH2N), 5.30 (1H, d, J 14.0, ring opened H’s),
6.90 (1H, d, J 14.0, ring opened H’s) and 7.15 (5H, s, Ph);
δC (100 MHz, CDCl3, Me4Si) 5.50 (N–SiMe3), 11.66 (CH3/Pr),
21.14 (CH /Pr), 46.76 (CH –N), 99.67 (᎐CHPh), 123.22 (C-4/
᎐
2
2
Ph), 123.45 (C-2 & C-6/Ph), 128.34 (C-3 & C-5/Ph), 135.57
(CHNSiMe3) and 139.88 (C-1/Ph).
Attempted purification by column chromatography and dis-
tillation on a bigger scale using a Kugelrohr apparatus only
gave products of decomposition.
The reaction was also carried out using cis-1-propyl-2-tri-
methylsilyl-3-phenylaziridine (0.10 g, 0.43 mmol) and catalytic
quantities of trimethylsilyl iodide (0.02 g, 0.06 mmol). The reac-
tion mixture was analysed by 1H NMR spectroscopy at regular
1
–
intervals (every h). After 1 h, the reaction mixture afforded
4
trans-(N-trimethylsilyl-N-propylamino)-1-phenylstyrene (96%
1
as determined by H NMR). The product was confirmed by
comparison of spectra with those of an authentic sample.
trans-(N-Trimethylsilyl-N-phenylamino)phenylstyrene. The
reaction was carried out using cis-1,3-diphenyl-2-trimethylsilyl-
aziridine (0.12 g, 0.44 mmol) and trimethylsilyl iodide (0.09 g,
105 (PhCHOH, 5.1), 104 (PhCH᎐CH , 5.3), 91 (PhCH , 11), 86
᎐
3
2
(CH N(CH )Pr, 85.3), 77 (Ph, 9.9), 73 (CH OCH –CH᎐N, 3.7),
᎐
2
3
3
2
1
44 (C H or CH N᎐ϩCH , 40.2) and 43 (C H , 5.0) (Found: C,
0.44 mmol). The reaction mixture was analysed by H NMR
᎐
3
8
3
3
3
7
1
–
75.2; H, 10.5; N 6.7. C13H21ON requires C, 75.3; H, 10.2; N,
6.8%).
spectroscopy at h intervals. After 1¹ h, the reaction mixture
4
¯
²
afforded a yellowish-brown solution containing trans-(N-
446
J. Chem. Soc., Perkin Trans. 1, 2000, 439–448

View Online
trimethylsilyl-N-phenylamino)phenylstyrene (75% as deter-
mined by 1H NMR); δH (400 MHz, CDCl3, Me4Si) 0.20 (9H, s,
SiMe3), 5.10 (1H, d, J 14.0) and 6.50–8.00 (1H, d, J 14.0 and,
10H, m, Ph); δC (100 MHz, CDCl3, Me4Si) 5.51 (NSiMe3),
partially filled with 4 Å molecular sieves which had been dried
by heating for 1 day in an oven at 200 ЊC and then in a vacuum
oven at 90 ЊC for three days. The vial was then filled with the
tetrabutylammonium fluoride solution. After several hours of
shaking the liquid was quickly transferred into a second vial
containing fresh, activated molecular sieves and shaken for 24
hours. The preparation was used within the next 24 hours.
When used, the material was removed by syringe and trans-
ferred to the reaction vial.
113.34 (᎐CHPh), 126.38, 127.34, 128.34, 128.85, 129.03 and
᎐
129.25 (Ph C’s), 130.12 (᎐CHN), 142.81 and 145.86 (C-1/Ph’s).
᎐
Attempted purification by chromatography using a silica
column and distillation on a bigger scale using a Kugelrohr
apparatus only gave products of decomposition.
The reaction was also carried out using trans-1,3-diphenyl-2-
trimethylsilylaziridine (0.09 g, 0.33 mmol) and trimethylsilyl
iodide (0.07 g, 0.33 mmol). After 3 min, the reaction mixture
afforded a yellowish-brown solution containing trans-(N-tri-
methylsilyl-N-phenylamino)phenylstyrene (98% as determined
by 1H NMR). The product was characterised by comparison of
spectra with those of an authentic sample.
2-Methoxycarbonyl-2-deutero-1-phenylaziridine. 2-Methoxy-
carbonyl-2-dimethylphenylsilyl-1-phenylaziridine (0.05 g, 0.161
mmol) was placed in a 5 mm NMR tube with 0.5 ml dry
deuterochloroform under nitrogen. Dried acetone (0.023 ml,
0.318 mmol) was introduced by syringe and the tube shaken to
mix the reagents. A volume of dried tetrabutylammonium
fluoride corresponding to 0.1 mol equivalents was then added.
NMR spectroscopy indicated immediate and complete conver-
sion to 2-methoxycarbonyl-2-deutero-1-phenylaziridine. The
sample was taken up in ether, washed with brine, dried, evapor-
ated and purified by column chromatography on silica, using
pentane as the eluent; δH (400 MHz, CDCl3, Me4Si) 2.24 (1H, s,
CHaHb), 2.60 (1H, s, CHaHb), 3.76 (3H, s, OCH3), 6.79–7.55
(5H, m, Ph); δC (100 MHz, CDCl3, Me4Si) 34.4 (CH2), 38.1
(CD), 53.1 (OCH3), 121.6, 124.0, 129.5 and 152.5 (Ph) and
2-Methoxycarbonyl-2-dimethylphenylsilyl-1-phenyl-1-tri-
methylsilylaziridinium trifluoromethanesulfonate. This reaction
was carried out using 0.05 g (0.161 mmol) 2-methoxycarbonyl-
2-dimethylphenylsilyl-1-phenylaziridine and 0.036 g (0.031 ml,
0.161 mmol) trimethylsilyltrifluoromethanesulfonic acid. Com-
plete conversion to 2-methoxycarbonyl-2-dimethylphenylsilyl-
1-phenyl-1-trimethylsilylaziridinium trifluoromethanesulfonate
was observed. The product could not be isolated owing to
decomposition on exposure to air; δH (400 MHz, CDCl3, Me4Si)
0.12 and 0.44 (6H, 2 × s, Me2Si), 0.52 (9H, s, Me3SiN), 2.53
(1H, s, NCHaHb), 2.94 (1H, s, NCHaHb), 3.51 (3H, t, CH3) and
6.84–7.59 (10H, m, NPh and SiPh); δC (100 MHz, CDCl3,
Me4Si) Ϫ3.6 and Ϫ3.4 (Me2Si), 0.9 (Me3SiN), 36.5 (CH2), 39.8
(CSi), 50.6 (CH3O), 121.3, 123.9, 128.4, 129.5, 130.1, 130.2,
170.1 (C᎐O) (Found Mϩ, 178.0731 (EI), C H DNO requires
᎐
10 10
2
Mr 178.0853).
2-Methoxycarbonyl-1-phenyl-2-(1-dimethylphenylsiloxy-
hexyl)aziridine. 2-Methoxycarbonyl-2-dimethylphenylsilyl-1-
phenylaziridine (0.3 g, 0.965 mmol) was placed in a 2 ml Teflon
sealed vial which had been dried by heating. Freshly distilled
hexanal (0.17 ml, 1.447 mmol) was injected into the vial. The
resultant mixture was then warmed and agitated, in order to
ensure thorough mixing, and then cooled to Ϫ78 ЊC. Dry
tetrabutylammonium fluoride (3 drops, ca. 5%) was added to
the vial over a 5 minute period resulting in the formation of a
yellow mixture. This was allowed to warm to 0 ЊC and then 0.5
ml dry THF was added. After a further 17 hours at this tem-
perature the mixture was diluted with ether, washed well with
brine, dried and evaporated to give mostly the fully desilylated
material and the silylether adduct (2-methoxycarbonyl-1-
phenyl-2-(1-dimethylphenylsiloxyhexyl)aziridine) as a minor
product, along with some of the free alcohol and polymerized
aldehyde. The product mixture was purified by column chrom-
atography on silica, using pentane as the eluent to give the
product silylether as a colourless viscous oil (0.020 g, 0.0487
mmol, 5.0%). None of the free alcohol could be isolated from
the column owing to decomposition. Proton NMR data show
that the product is present as a mixture of diastereoisomers
which are denoted here as x and y; δH (400 MHz, CDCl3, Me4Si)
0.313, 0.335, 0.339 and 0.358 (4 × 3H, 4 × s, Me2Si), 0.78–0.82
(3H, 2 overlapping triplets, CH2Mex and CH2Mey), 1.20–1.66
(8H, m, CH2CH2CH2CH2), 2.28 and 2.57 (1H, 2 × d, J 1.6, Hxa
and Hxb), 2.51 and 2.64 (1H, 2 × d, J 2.0, Hya and Hyb), 3.18
and 3.28 (3H, 2 × s, OMey and OMex), 4.14 and 4.38
(1H, 2 × dd, JIx 5.8, J2x 8.4, J1y 3.2, J2y 8.0, HCOSi) and 6.62–
7.58 (10H, m, PhN and PhSi); δC (100 MHz, CDCl3, Me4Si)
Ϫ0.6, Ϫ0.2 (SiMe2), 14.7 (CH3), 23.3 (CH3CH2), 26.3 (CH3-
CH2CH2), 32.4 (CH3CH2CH2CH2), 34.1 (SiOCHCH2), 35.2
(NCH2), 51.2 (CH3O), 52.3 (CCO2Me) and 72.2 (COSi) (Found
Mϩ Ϫ CH3, 396.2006 (EI), C24H33NO3Si requires Mϩ Ϫ CH3,
396.1995).
135.0 and 149.4 (NPh and CPh) and 170.9 (C᎐O).
᎐
1,2-Diphenylaziridine. A solution of 1.0 M tetra-n-butyl-
ammonium fluoride (2.0 ml, 1.97 mmol) in THF was added
dropwise to a stirred solution of trans-1,3-diphenyl-2-tri-
methylsilylaziridine (0.48 g, 1.79 mmol) in acetonitrile (3 ml)
under nitrogen. The orange–brown solution was heated under
reflux at 70 ЊC (18 h). The reaction mixture was quenched with
distilled water (4 ml), extracted with diethyl ether (2 × 10 ml)
and dried over anhydrous magnesium sulfate. The ethereal solu-
tion was concentrated to dryness to afford impure red–brown
liquid l,2-diphenylaziridine (0.24 g, 69.2%). The product was
confirmed by comparison of spectra with those of an authentic
sample.32
2-Methoxycarbonyl-1-phenylaziridine. This product was
obtained under various conditions when 2-methoxycarbonyl-
1-phenyl-2-triethylsilylaziridine
or
2-methoxycarbonyl-2-
dimethylphenylsilyl-1-phenylaziridine was reacted with
tetrabutylammonium fluoride or caesium fluoride in the pres-
ence and absence of other reagents such as silica gel or 18-
crown-6. Isolation of the product was carried out in the follow-
ing manner. The reaction mixture was diluted with ether and
the solution washed with several portions of brine, in order to
remove the fluoride source. The resultant solution was then
dried and evaporated prior to purification by column chrom-
atography on silica, using hexane or pentane as the eluent. Pure
aziridine was recovered in the later fractions; νmax (neat)/cmϪ1
3090–2835, 1745, 1595, 1490, 1300–1250, 1200, 1120, 1195,
1005, 910, 840, 795 and 700; δH (400 MHz, CDCl3, Me4Si) 2.26
(1H, dd, J 1.46 and 6.34, CHCO2Me), 2.63 (1H, dd, J 1.46 and
2.91, NCHaHb), 2.76 (1H, dd, J 6.34 and 2.91, NCHaHb), 3.74
(OCH3), 6.88–7.55 (5H, m, Ph); δC (100 MHz, CDCl3, Me4Si)
33.7 (CH2), 37.5 (CH), 52.1 (OCH3), 120.7, 123.4, 129.1 and
2-Methoxycarbonyl-1-phenyl-2-(1-dimethylphenylsiloxy-
benzyl)aziridine. 2-Methoxycarbonyl-2-dimethylphenylsilyl-1-
phenylaziridine (0.2 g, 0.643 mmol) was placed in a 2 ml teflon
sealed vial which had been dried by heating. Benzaldehyde (0.13
ml, 1.28 mmol) which had been washed with sodium sulfite and
sodium bicarbonate solutions then dried and distilled, was
152.5 (Ph) and 170.5 (C᎐O).
᎐
Dried tetrabutylammonium fluoride. This method was used to
dry samples of commercial 1 M tetrabutylammonium fluoride
in THF containing 5 wt% water. A 10 cm3 teflon sealed vial was
J. Chem. Soc., Perkin Trans. 1, 2000, 439–448
447

View Online
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Thomas and G. H. Whitham, J. Chem. Soc., Perkin Trans. 1, 1981,
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17 J. E. Baldwin, R. M. Adlington and N. G. Robinson, J. Chem. Soc.,
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injected into the vial. The resultant mixture was then warmed
in order to ensure thorough mixing and then cooled in an
ice–salt bath. Dry tetrabutylammonium fluoride (2 drops, ca.
5%) was added resulting in the formation of a brown mix-
ture. This was maintained at 0 ЊC for 15 minutes and then
0.5 ml dry THF was added. After a further 0.5 hours the
mixture was diluted with ether washed well with brine, dried
and concentrated to give again, a silylether adduct, as the
major product (ca. 80% by NMR) along with some of the
free alcohol and fully desilylated material. The product mixture
was purified by column chromatography on silica using pen-
tane as the eluent to give the product as a colourless viscous
oil (0.150 g, 0.360 mmol, 56%). None of the free alcohol
could be isolated from the column owing to decomposition.
Again, preliminary investigations indicated that the product is
stable to treatment with fluoride ion; δH (400 MHz, CDCl3,
Me4Si) 0.29 and 0.32 (2 × 3H, 2 × s, Me2Si), 2.49 and 2.73
(2H, 2 × s, H2Cx and H2Cy), 3.28 and 3.31 (3H, 2 × s, OMex
and OMey), 5.34 and 5.60 (1H, 2 × s, PhCHx and PhCHy) and
6.64–7.91 (15H, m, NPh, CPh, SiPh); δC (400 MHz, CDCl3,
Me4Si) Ϫ0.85, Ϫ0.33, Ϫ0.32, 1.7 (4 × CH3, SiMe), 34.5
(H2Cy), 34.7 (H2Cx), 51.7, 51.8, 52.2 and 52.3 (OMex&y
and MeOCOCx&y), 120.2–141.7 (14 resonances, NPh, CPh,
SiPh), 150.2 and 150.7 (2 × ipso C from NPh), 168.7 and 169.1
(MeOCOx&y); m/z (EI) 417 (Mϩ, 16.3%), 402 (Mϩ Ϫ Me, 7.4),
241, (PhC(H)OSiMe2Ph, 46.8), 167 (32.9), 135 (SiMe2Ph,
100.0), 77 (18.5) (Found: C, 71.5; H, 6.5; N, 2.9%. C25H27NO3Si
requires: C, 71.9; H, 6.5; N, 3.3%).
18 J. E. Baldwin, R. M. Adlington, I. A. O’Neil, C. Schofield, A. C.
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