Synthesis of N-bridgehead fused bicyclic β-lactams through organometal-mediated transformations of 1,2-dialkenylaziridines

Article abstract of DOI:10.3987/com-04-10166

N-Bridgehead fused bicyclic β-lactams have been synthesized through sequential organometal-mediated transformations of 1,2-dialkenylaziridines, namely Co₂(CO)₈-catalysed carbonylation and ring-closing metathesis (RCM). When firstly subjected to RCM conditions, either with Schrock-Hoveyda or Grubbs' catalyst, 1,2-dialkenylaziridines did not afford the expected bicyclic N-bridgehead products. In contrast, however, cis-1,2-dialkenylaziridines were amenable to carbonylative ring expansion, affording trans-1,4-dialkenyl-β-lactams which could be subsequently metathesized to the corresponding fused bicyclic compounds using Grubbs' catalyst. Unexpectedly, carbonylation of trans-1,2-dialkenylaziridines occurred with the unprecedented rearrangement to the 5,6-dihydro-4H-[1,3]oxazine skeleton.

Full text of DOI:10.3987/com-04-10166

HETEROCYCLES, Vol. 63, No. 11, 2004, pp. 2495 - 2514
Received, 5th July, 2004, Accepted, 16th September, 2004, Published online, 17th September, 2004
SYNTHESIS OF N-BRIDGEHEAD FUSED BICYCLIC β-LACTAMS
THROUGH ORGANOMETAL-MEDIATED TRANSFORMATIONS OF
1,2-DIALKENYLAZIRIDINES§
Paolo Davoli, Alberto Spaggiari, Elisa Ciamaroni, Arrigo Forni, Giovanni
Torre, and Fabio Prati*
Department of Chemistry, University of Modena and Reggio Emilia
via Campi 183, I–41100 Modena, Italy. E-mail: prati.fabio@unimore.it
Abstract – N-Bridgehead fused bicyclic β-lactams have been synthesized
through
sequential
organometal-mediated
transformations
of
1,2-dialkenylaziridines, namely Co2(CO)8-catalysed carbonylation and
ring-closing metathesis (RCM). When firstly subjected to RCM conditions, either
with Schrock-Hoveyda or Grubbs’ catalyst, 1,2-dialkenylaziridines did not afford
the expected bicyclic N-bridgehead products. In contrast, however,
cis-1,2-dialkenylaziridines were amenable to carbonylative ring expansion,
affording trans-1,4-dialkenyl-β-lactams which could be subsequently
metathesized to the corresponding fused bicyclic compounds using Grubbs’
catalyst. Unexpectedly, carbonylation of trans-1,2-dialkenylaziridines occurred
with the unprecedented rearrangement to the 5,6-dihydro-4H-[1,3]oxazine
skeleton.
INTRODUCTION
Aziridines represent a valuable class of useful and highly versatile synthetic intermediates.1 In fact, they
can be prepared by several stereoselective methods2,3 and, due to the intrinsic high strain of the aziridine
ring, they are capable of undergoing sterecontrolled nucleophilic ring opening reactions, leading to a
wide variety of nitrogen-containing compounds bearing the most different functionalities.4,5 By selecting
suitable substituents at the ring nitrogen or carbon atoms, aziridines can be also converted into less
strained heterocycles, often in a single-step sequence. For instance, N-acylaziridines are known to
rearrange to the corresponding oxazolines with retention of configuration,6 whilst low-temperature
rearrangement of vinyl aziridines has provided a stereoselective approach to pyrrolines,7
§ This paper is dedicated to Professor Irene Moretti on the occasion of her retirement.

tetrahydropyridines8 and seven-membered lactams.9
The relief of ring strain represents the driving force also in another ring expansion of fame, namely the
Co2(CO)8-catalysed carbonylation of aziridines,10 whereby the three-membered cycle is expanded to a
β-lactam ring with insertion of carbon monoxide into the C–N bond. This reaction has proved an
efficient tool for the stereoselective synthesis of substituted β-lactams11,12 and has been also successfully
applied in a formal synthesis of the carbapenem antibiotic PS-5.13
Despite the variety of synthetic approaches to bicyclic β-lactams,14 to the best of our knowledge only a
single example of carbonylative expansion on a 2,3-fused bicyclic aziridine has been reported in the
literature so far.10 In that case, however, the substrate that underwent carbonylation did not bear an
angular nitrogen atom and led therefore to a bicyclic β-lactam fused at the 3,4 position,10 i.e. the ‘wrong’
one if compared to β-lactam antibiotics, which normally feature a 1,4-condensation pattern instead.
Hence, we were prompted to investigate whether N-bridgehead fused β-lactams could be prepared by
carbonylation of appropriate bicyclic aziridines.
To this end, ring-closing metathesis (RCM) was envisaged as a desirable method for the formation of the
second fused ring. In fact such a reaction, which occurs in the presence of either Ru- or Mo-carbene
complexes as the catalyst, represents a powerful synthetic tool for the construction of nitrogen-containing
heterocycles from suitable non-conjugated acyclic dienes; furthermore, RCM reactions usually proceed
under mild conditions and with high functional group tolerance.15–19 Along this line, in the past few years
RCM has been successfully applied to the synthesis of a variety of bicyclic systems having the most
diverse ring sizes and substitutions.20–24 Recently, in particular, fused bicyclic β-lactams have been
accessed via RCM, whereby formation of a second 6- to 8-membered ring onto an appropriate β-lactam
scaffold acting as a conformational constraint could be attained.20–24
Accordingly, we reasoned that RCM onto a suitably functionalised aziridine ring could lead to a fused
bicyclic system bearing the nitrogen heteroatom at the angular position, which in turn would undergo
carbonylative expansion to afford the desired fused bicyclic β-lactam. To achieve this goal, two alkenyl
appendages in position 1 and 2 of the aziridine ring would be required for the RCM cyclisation.
Therefore, we describe herein the synthesis of a variety of 1,2-dialkenylaziridines and their conversion
into fused bicyclic β-lactams by means of sequential organometal-mediated transformations, namely
RCM cyclisation and Co2(CO)8-catalysed carbonylative expansion.
RESULTS AND DISCUSSION
Synthesis of 1,2-dialkenylaziridines. – 1,2-Dialkenylaziridines were prepared by addition of an
appropriate Grignard reagent to 1-allyl-2-formyl-3-phenylaziridine (4), which in turn was synthesized
from methyl cinnamate (1), as outlined in Scheme 1. In particular, addition of bromine to

α,β-unsaturated ester (1) in n-hexane at reflux smoothly provided dibromo derivative (2), which was
subjected to aminative cyclisation with allylamine in DMF at room temperature, affording
N-allylaziridinecarboxylate (3) as a 55:45 mixture of cis/trans isomers (3a and 3b, respectively) in 82%
overall yield. The two isomers were separated by column chromatography and the ring stereochemistry
1
was assigned on the basis of the J2,3 constant in the H NMR spectrum.11 Aziridines (3a) and (3b) were
subsequently reduced with DIBAL-H in CH2Cl2 at –78 ºC to the corresponding formyl derivatives (4a
and 4b) in 79 and 70% yields, respectively.25
Ph
R
Ph
R
Br
i.
ii.
Ph
Ph
N
N
COOMe
COOMe
Br
1
2
3a R = COOMe
4a R = CHO
3b R = COOMe
4b R = CHO
iii.
iii.
Scheme 1. i. Br2, n-hexane, reflux (88%); ii. allylamine, DMF, rt (93%); iii. DIBAL-H, CH2Cl2, –78 ºC.
2-Formylaziridines (4a) and (4b) were alkylated with different Grignard reagents (Scheme 2) in order to
introduce the second alkenyl appendage that was required for the subsequent ring-closing metathesis
reaction. In the case of cis-aziridine (4a), addition of vinylmagnesium bromide in THF at –40 ºC
provided derivative (5a) as a mixture of two diastereoisomers in a 77:23 ratio and 48% total yield (Table
1). When allylmagnesium bromide was used as the reagent, 1,2-dialkenylaziridine (6a) was obtained in
only 26% yield, whilst 3-butenylmagnesium bromide (at –78 ºC) afforded product (7a) as a 62:38
mixture of diastereoisomers in 52% overall yield. As far as trans-aziridine (4b) is concerned, the same
alkenylmagnesium reagents were used under similar conditions, affording the corresponding
1,2-dialkenyl derivatives (5b-7b), albeit in low to moderate yields (Table 1). In all cases, the two
diastereoisomers could be separated by means of column chromatography; although their relative
configuration could not be determined, only the first eluted diastereoisomer was selected and further
processed.
OH
OTBDMS
Ph
Ph
Ph
BrMg
O
TBDMSCl
n
n
n
N
N
N
DMAP, CH2Cl2, rt
4a,b
5a,b-7a,b
8a,b-9a,b
Scheme 2.

In addition, for aziridines (6a,b) and (7a,b) the side chain hydroxy group was protected as TBDMS ether
by treatment with TBDMSCl and DMAP in methylene chloride at room temperature,11 to afford
derivatives (8a,b) in 60 and 34% yields, and (9a,b) in 39 and 75% yields, respectively (Scheme 2).
diastereoisomeric
aziridine stereochemistry
n
solvent
product yield (%)
ratio
4a
4a
4a
4b
4b
4b
cis
cis
cis
trans
trans
trans
0
1
2
0
1
2
THF
THF
THF
THF
Et2O
Et2O
5a
6a
7a
5b
6b
7b
48
26
52
19
40
41
77:23
64:36
62:38
90:10
50:50
41:59
Table 1
Carbonylation and ring-closing metathesis of 1,2-dialkenylaziridines. – Aiming to explore the
feasibility of ring-closing metathesis on three-membered N-containing heterocycles bearing appropriate
alkenyl appendages, 1,2-dialkenylaziridines (5-6) were subjected to RCM conditions using
Schrock-Hoveyda complex (I) (Figure 1) as the catalyst. In fact, successful ring closures of amino dienes
have been reported in the presence of I to yield 2,5-dihydropyrroles.26,27 In contrast, Ru-based catalysts
such as II (Grubbs’ catalyst, Figure 1) are not effective with either secondary or tertiary amines, unless
masked as amides/carbamates or ammonium salts, respectively.28,29 On the other hand, in fact,
dialkenylamides are known to metathesize successfully to N-containing heterocycles of various ring sizes
in the presence of II.15–19
iPr
iPr
PCy3
Cl
Cl
Ph
N
Mo
O
Ru
CF3
Ph
F3C
PCy3
O
CF3
CF3
I
II
Figure 1. – Catalysts for ring-closing metathesis (RCM)
Since any attempt to convert aziridines (5a-7a) into the corresponding ammonium salts met with failure,
the possibility of exploiting the easy-to-use Grubbs’ catalyst II for the formation of the second fused ring
by RCM was ruled out. Therefore, we switched to Schrock-Hoveyda Mo-carbene I which, however,
requires strictly anhydrous and oxygen-free conditions. Nonetheless, treatment of aziridines (5-6) with 5

mol% I in either degassed CH2Cl2 or benzene at reflux did not afford the desired ring-closed product
(Scheme 3) under any of the reaction conditions employed, unfortunately.
OR
RO
Ph
i.
n
n
Ph
N
N
5-6
Scheme 3. i. Schrock-Hoveyda catalyst (I), CH2Cl2 or benzene, reflux.
Hence, the reaction sequence had to be reversed, and the RCM cyclisation was delayed after the
carbonylative expansion of the aziridine ring (Scheme 4). cis-1,2-Dialkenylaziridines (5a-9a) were
dissolved in 1,2-dimethoxyethane (DME) and treated with 500 psi carbon monoxide in the presence of
Co2(CO)8 as the catalyst in 1/12 ratio at 110 ºC to afford the corresponding trans-1,4-dialkenyl-β-lactams
(10a-14a) (Table 2). CO Insertion was confirmed by 13C NMR spectroscopy, whereas the trans
1
stereochemistry of the resulting β-lactam ring was assigned on the basis of the J3,4 constant in the H
NMR spectrum.11 Thereafter, β-lactams (10a-14a) were successfully metathesized with Grubbs’ complex
II (CH2Cl2, reflux) to the desired bicyclic compounds (15a-19a) in good to excellent yields (Scheme 4,
Table 2).
OR
RO
OR
Ph
Ph
Ph
i.
ii.
n
n
n
N
N
N
O
O
5a-9a
10a-14a
15a-19a
Scheme 4. i. Co2(CO)8, DME, CO (500 psi), 110 ºC; ii. Grubbs’ catalyst (II), CH2Cl2, reflux.
monocyclic
β-lactam
bicyclic
β-lactam
carbonylation
yield (%)
RCM
yield (%)
aziridine
n
R
5a
6a
7a
8a
9a
0
1
2
1
2
H
H
H
10a
11a
12a
13a
14a
66
42
53
63
21
15a
16a
17a
18a
19a
73
50
88
66
70
TBDMS
TBDMS
Table 2
Under the same reaction conditions, trans-aziridines (5b-7b) gave rise only to a complex mixture which

was not amenable to further purification. In contrast, when trans-aziridines (8b-9b) were treated with
dicobalt octacarbonyl and carbon monoxide in DME, using the same conditions reported above,
disappearance of the starting material occurred and, in both cases, a new product (20b-21b) was isolated
as a mixture of E/Z stereoisomers which could be separated by column chromatography, albeit in low
overall yield (17 and 37%, respectively). MS spectroscopy confirmed the successful insertion of a CO
unit, but examination of NMR spectra raised doubts as to the identity of the carbonylation products. In
particular, the lack of a diagnostic doublet at 4.0–4.3 ppm accounting for the H(3) proton suggested the
absence of the expected β-lactam framework and demanded for more extensive investigations by means
of 2D NMR spectroscopic techniques. Accordingly, COSY experiments were performed and allowed us
to assign unambiguously the 5,6-dihydro-4H-[1,3]oxazine structure (20b-21b) to the reaction products
(Scheme 5). In particular, the alkenyl appendage bearing the TBDMS-protected hydroxy group was
found unchanged, whilst the signals belonging to the allylic substituent at nitrogen were missing. A new
spin system consisting of three –CH2– units was revealed by COSY, and one of these multiplets
resonated at 3.29–3.42 ppm, suggesting the presence of a single carbon-oxygen bond, which would then
force the three methylene groups within a six-membered O-containing azacycle, namely a
5,6-dihydro-4H-[1,3]oxazine.
B-
OTBDMS
OTBDMS
Ph OTBDMS
H
Ph
Ph
O
n
i.
n
n
N
N
N
O
H_B
8b-9b
20b-21b
Scheme 5. i. Co2(CO)8, DME, CO (500 psi), 110 ºC.
The unexpected formation of the 5,6-dihydro-4H-[1,3]oxazine skeleton would suggest that trans
aziridines (8b-9b) did undergo carbonyl insertion and β-lactam formation which, however, was followed
by rearrangement to products (20b-21b) (Scheme 5). Such a rearrangement could be explained by
postulating first the formation of a cis β-lactam, according to a well-established mechanism.12 Most
likely, abstraction of the H(3) hydrogen, followed by cleavage of the N–C(4) bond and attack of the
carbonyl oxygen to the allylic double bond would result, ultimately, in the formation of the
5,6-dihydro-4H-[1,3]oxazine ring, as depicted in Scheme 5.
CONCLUSIONS
In the attempt to prepare fused bicyclic aziridines to be used for Co2(CO)8-catalysed carbonylation as an

alternative access to the N-bridgehead fused β-lactam motif that is normally encountered among β-lactam
antibiotics, ring-closing metathesis (RCM) was tested on suitable 1,2-dialkenylaziridines. Regrettably,
however, formation of a second 6- to 8-membered carbocycle onto either a cis- or trans-aziridine ring
playing as a conformational constraint has proved not feasible with Schrock-Hoveyda catalyst I, even
though no inherent functional group incompatibility in RCM with I was present, apparently.
In contrast, the corresponding trans-β-lactams, which were successfully synthesized by carbonylative
ring expansion of cis-1,2-dialkenylaziridines, were amenable to ring-closing metathesis with Grubbs’
catalyst II, affording N-bridgehead bicyclic fused systems of the [n.2.0] type (n = 4, 5, 6), in line with
literature data that describe fusion of 6–8-membered carbocycles onto a β-lactam ring by means of RCM
with either I or II.20–22
Surprisingly, carbonylation of trans 1,2-dialkenylaziridines in the presence of dicobalt octacarbonyl as
the catalyst occurred with rearrangement to the 5,6-dihydro-4H-[1,3]oxazine skeleton instead, a process
which is unprecedented.
EXPERIMENTAL
13
1H and C NMR were recorded in CDCl3 solution on a Bruker DPX 200 MHz spectrometer; chemical
shifts (δ) are reported in ppm downfield from TMS as internal standard; coupling constants (J) are given
in Hz. For MS spectral determinations, Finnigan MAT SSQ A and Hewlett-Packard HP5972 spectrometers
were used (EI, 70 eV). Elemental analyses were performed with a Carlo Erba Elemental Analyzer mod. 1110.
Gas-chromatographic analyses were performed on a HP5890A gas-chromatograph equipped with a DB-1
column (J&W Scientific, 30 m length, 0.53 mm i.d., 5 µm film thickness) using helium as carrier gas. All
organic solvents were dried and distilled by standard methods prior to use and all reactions requiring
anhydrous conditions were performed using oven-dried and argon-flushed glassware. Chromatographic
purification of compounds was carried out on silica gel (60–200 µm).
Methyl cinnamate was purchased from Aldrich. Schrock-Hoveyda (I) and Grubbs’ (II) catalysts, as well
as Co2(CO)8 were all from Strem Ltd. Grubbs’ catalyst (II) was maintained in a Schlenk tube under Ar
atmosphere, whilst Schrock-Hoveyda (I) catalyst was always handled using a dry-box under nitrogen
atmosphere. Co2(CO)8 was stored in a Schlenk flask under CO atmosphere.
Methyl 2,3-Dibromo-3-phenylpropanoate (2) – In a 250-mL two-necked flask equipped with a reflux
condenser and a dropping funnel, commercially available methyl cinnamate (1) (16.40 g, 101.12 mmol)
was dissolved in 45 mL of n-hexane under gentle heating, affording a clear colorless solution. Bromine
(5.7 mL, 111.23 mmol) was slowly added dropwise under magnetic stirring and the heating was
gradually increased. The solution started to fade only upon reflux and, at the same time, a white solid
began to crystallize. After refluxing for 30 min, the reaction mixture was cooled to rt and the precipitate

was filtered and recrystallized from n-hexane to afford 28.52 g of 2 as a white solid (mp 109–111 °C) in
88% yield. 1H NMR (200 MHz): δ 3.94 (3H, s, COOCH3), 4.88 (1H, d, J 11.7, BrCHCOO), 5.38 (1H, d,
J 11.7, CHBrPh), 7.34–7.47 (5H, m, arom). MS, m/z: 324-322-320 (Br pattern, M+, 4%), 293-291-289
(2), 265-263-261 (3), 243-241 (58), 184-182 (8), 171-169 (6), 161 (16), 131 (52), 121 (86), 103 (100), 77
(55), 59 (37). Anal. Calcd for C10H10O2Br2: C, 37.30; H, 3.13. Found C, 37.57; H, 3.44.
cis- and trans-1-Allyl-2-methoxycarbonyl-3-phenylaziridine (3a and 3b) – Dibromo derivative (2)
(10.5 g, 32.6 mmol) was dissolved in 40 mL of anhydrous DMF in a 250-mL two-necked flask equipped
with a reflux condenser and a dropping funnel, and cooled to 0–5 °C with a water–ice bath. A solution of
allylamine (8.56 mL, 114.1 mmol) in 10 mL of dry DMF was added dropwise and the mixture was
stirred for 24 h at rt. The orange solution was poured in 600 mL of water and extracted with light
petroleum (6 × 150 mL). The organic phases were combined, dried over MgSO4, filtered and rotary
evaporated, to provide a yellow residue. Purification by column chromatography (light petroleum/ether
70:30) afforded aziridines trans 3b (2.96 g) and cis 3a (3.61 g) as yellow oils in a total 93% yield.
3a: 1H NMR (200 MHz): δ 2.54 (1H, d, J 6.9, CHCOO), 2.93 (1H, d, J 6.9, PhCH), 3.04 (1H, ddt, J 14.1,
5.7, 1.3, NCH2), 3.30 (1H, dd, J 14.1, 5.4, NCH2), 3.44 (3H, s, COOCH3), 5.13 (1H, dq, J 10.4, 1.3, CH
=CH2), 5.28 (1H, dq, J 17.2, 1.7, CH=CH2), 5.85–6.10 (1H, m, CH=CH2), 7.14–7.43 (5H, m, arom). 13C
NMR: δ 178.8, 135.3, 134.4, 128.3, 128.0, 127.8, 117.8, 62.9, 52.0, 48.1, 46.2. MS, m/z: 217 (M+, 4%),
216 (13), 188 (1), 187 (2), 186 (9), 177 (5), 176 (62), 161 (3), 159 (2), 158 (19), 144 (16), 131 (12), 121
(12), 116 (100), 103 (7), 91 (20), 89 (25), 77 (18).30 Anal. Calcd for C13H15NO2: C, 71.87; H, 6.96; N,
6.45. Found C, 71.74; H, 6.71; N, 6.28.
3b: 1H NMR (200 MHz): δ 2.80 (1H, d, J 2.7, CHCOO), 3.22 (1H, br s, PhCH), 3.60 (1H, br s, NCH2),
3.70 (1H, br s, NCH2), 3.78 (3H, s, COOCH3), 5.12 (1H, d, J 10.4, CH=CH2), 5.26 (1H, d, J 17.1,
13
CH=CH2), 5.91–6.08 (1H, m, CH=CH2), 7.24–7.38 (5H, m, arom). C NMR: δ 169.1, 135.2, 133.9,
128.4, 127.9, 127.7, 127.5, 126.3, 117.5, 116.4, 62.5, 53.8, 52.1, 51.7, 48.1, 47.7, 45.7, 44.1. MS, m/z:
217 (M+, 4%), 216 (13), 188 (1), 187 (2), 186 (9), 177 (5), 176 (62), 161 (3), 159 (2), 158 (19), 144 (16),
131 (12), 121 (12), 116 (100), 103 (7), 91 (20), 89 (25), 77 (18).30 Anal. Calcd for C13H15NO2: C, 71.87;
H, 6.96; N, 6.45. Found C, 72.02; H, 7.15; N, 6.28.
cis-1-Allyl-2-formyl-3-phenylaziridine (4a) – Aziridine (3a) (2.00 g, 9.21 mmol) was dissolved in 22
mL of anhydrous dichloromethane in a 250-mL three-necked flask equipped with a reflux condenser and
a dropping funnel and cooled at –78 °C. A 1.2 M solution of DIBAL-H in toluene (11.5 mL, 13.8 mmol)
was then added under mechanical stirring and Ar atmosphere during a 30 min period; particular care was
taken in cooling the DIBAL-H solution before addition by letting it flow dropwise along the cold flask
surface before it came into contact with the reaction mixture. After 1 h, sodium fluoride (7.0 g, 167

mmol) was added under vigorous stirring, followed by water (4.8 mL). The solution became turbid and a
white precipitate formed. The cold bath was then removed and the mixture was allowed to warm to rt.
Ether (200 mL) was added and the light yellow gelatinous solid which precipitated was filtered off,
washing with abundant ether. The clear solution was dried (MgSO4), filtered and concentrated in vacuo
to give a crude residue that was chromatographed on silica gel (ether/light petroleum 70:30), affording
1
formylaziridine (4a) as a pale yellow oil (1.352 g, 79%) H NMR (200 MHz): δ 2.35 (1H, t, J 6.6,
CHCHO), 3.10 (1H, d, J 6.7, PhCH), 3.17 (1H, ddt, J 14.1, 5.7, 1.5, NCH2), 3.29 (1H, ddt, J 14.1, 5.7,
1.5, NCH2), 5.15–5.38 (2H, m, CH=CH2), 5.88–6.14 (1H, m, CH=CH2), 7.10–7.60 (5H, m, arom), 8.98
(1H, d, J 6.6, CHO). 13C NMR: δ 202.2, 136.4, 128.7, 128.5, 128.2, 118.0, 71.6, 51.5, 46.4 (quaternary C
not seen). MS, m/z: 186 ([M–1]+, 12%), 185 (77), 184 (14), 168 (10), 167 (12), 156 (11), 128 (6), 127 (3),
107 (4), 91 (100), 77 (7), 65 (32), 51 (16). Anal. Calcd for C12H13NO: C, 76.98; H, 7.00; N, 7.48. Found
C, 77.13; H, 6.86; N, 7.56.
trans-1-Allyl-2-formyl-3-phenylaziridine (4b) – By close analogy to the preparation of 4a,
trans-aziridinecarboxylate (3b) (504 mg, 2.32 mmol) dissolved in 6 mL of dry CH2Cl2 was reduced with
1.2 M DIBAL-H in toluene (4.1 mL, 4.87 mmol) at –78 °C. Similar workup as above, followed by
1
chromatography with the same eluant, afforded 4b as a yellow liquid (300 mg, 70%). H NMR
spectroscopy showed broad and poorly resolved signals, indicating the presence of two invertomers at
1
nitrogen. H NMR (200 MHz): δ 2.83 (1H, br s, CHCHO), 3.15–4.00 (3H, br m, PhCH and NCH2),
4.90–5.40 (2H, br m, CH=CH2), 5.75–6.10 (1H, br m, CH=CH2), 7.15–7.45 (5H, m, arom), 9.68 (1H, br
s, CHO). 13C NMR: δ 198.4, 136.0, 129.9, 129.4, 127.6, 118.3, 56.2, 52.5, 51.2 (quaternary C not seen).
MS, m/z: 188 ([M+1]+, 2%), 184 (100), 167 (19), 155 (11), 128 (7), 107 (4), 91 (67). Anal. Calcd for
C12H13NO: C, 76.98; H, 7.00; N, 7.48. Found C, 77.28; H, 7.18; N, 7.31.
Alkylation of formylaziridines (4a-4b). Typical procedure. – The formyl aziridine (2.36 mmol) was
dissolved in 20 mL of dry ether or THF in a 50-mL two-necked flask equipped with a reflux condenser
and a bubbler. The flask was cooled (see below under entries 5a,b-7a,b for the appropriate value) and the
appropriate Grignard reagent (1.0 M in ether or THF) was slowly added dropwise under Ar flow and
magnetic stirring. The mixture became turbid, and a pale yellow solid precipitated. After 40 min the cold
bath was replaced with ice and the reaction mixture was stirred for additional 50 min. When the flask
was removed from the ice bath, precipitation of a conspicuous yellow solid was observed. The mixture
was then diluted with ether (100 mL), poured in water (80 mL) and the aqueous phase was adjusted to
pH 9 with NH4Cl. After separation of the organic layer, the aqueous phase was extracted with ether (3 ×
60 mL). The organic layers were pooled, washed with brine (60 mL), dried (MgSO4) and evaporated in
vacuo to give a crude residue which was purified by silica gel chromatography using the solvents

reported below.
cis-1-Allyl-2-(1-hydroxy-2-propenyl)-3-phenylaziridine (5a) – Alkylation of 4a with vinylmagnesium
bromide in THF at –40 °C, followed by work-up as above afforded the title compound (5a) in 48% yield
as a 77/23 mixture of two diastereoisomers which were separated by column chromatography using
Et2O/light petroleum 30:70 as the eluant.
1
1st eluted: orange oil; H NMR (200 MHz): δ 1.56 (1H, br s, OH), 1.87 (1H, dd, J 8.4, 6.4, PhCHCH),
2.78 (1H, d, J 6.4, PhCH), 3.07 (1H, ddt, J 13.8, 5.9, 1.4, NCH2), 3.26 (1H, ddt, J 13.8, 5.9, 1.4, NCH2),
3.66 (1H, t, J 6.7, CHOH), 5.12–5.39 (2H, m, CH=CH2), 5.89–6.14 (2 × 1H, m, CH=CH2), 7.22–7.49
(5H, m, arom). 13C NMR: δ 139.1, 137.2, 135.4, 128.6, 128.1, 127.4, 117.2, 115.3, 70.5, 63.3, 50.8, 46.0.
MS, m/z: 215 ([M]+, 3%), 214 (14), 198 (19), 186 (10), 175 (7), 174 (59), 158 (28), 146 (44), 144 (21),
129 (36), 118 (74), 117 (78), 104 (22), 99 (24), 98 (26), 91 (100), 77 (17), 68 (21), 55 (6).30 Anal. Calcd
for C14H17NO: C, 78.10; H, 7.96; N, 6.51. Found C, 78.26; H, 8.06; N, 6.41.
2nd eluted: yellowish oil; 1H NMR (200 MHz): δ 1.92 (1H, dd, J 8.3, 6.7, PhCHCH), 2.83 (1H, d, J 6.7,
PhCH), 2.68 (1H, br s, OH), 3.08 (1H, dd, J 13.8, 6.0, NCH2), 3.31 (1H, dd, J 13.8, 5.8, NCH2), 3.59 (1H,
ddt, J 8.3, 5.3, 1.4, CHOH), 4.97–5.39 (2 × 2H, m, CH=CH2), 5.63–5.83 (1H, m, CH=CH2), 5.94–6.17
(1H, m, CH=CH2), 7.18–7.47 (5H, m, arom). 13C NMR: δ 137.6, 135.3, 128.5, 127.9, 127.4, 117.6, 115.6,
70.8, 63.5, 51.2, 46.7 (quaternary C not seen). MS, m/z: 215 ([M]+, 3%), 214 (14), 198 (19), 186 (10),
175 (7), 174 (59), 158 (28), 146 (44), 144 (21), 129 (36), 118 (74), 117 (78), 104 (22), 99 (24), 98 (26),
91 (100), 77 (17), 68 (21), 55 (6).30 Anal. Calcd for C14H17NO: C, 78.10; H, 7.96; N, 6.51. Found C,
77.95; H, 8.15; N, 6.29.
trans-1-Allyl-2-(1-hydroxy-2-propenyl)-3-phenylaziridine (5b) – Alkylation of aziridine (4b) with
vinyl magnesium bromide in THF at –40 °C afforded 5b in 19% yield as a 90:10 mixture of
1
diastereoisomers, which were purified by column chromatography (ether/light petroleum 70:30). H
NMR spectroscopy showed broad and poorly resolved signals, indicating the presence of two
invertomers at nitrogen. Due to the paucity of material, the slow-eluting isomer could not be
characterized in full.
1
1st eluted: orange oil; H NMR (200 MHz): δ 2.20–2.40 (1H, br m, PhCHCH); 2.55–2.75 (1H, br m,
NCH2); 2.80–3.05 (1H, br m, NCH2); 3.28–3.33 (1H, br, PhCH); 3.50 (1H, br, OH); 4.25–4.40 (1H, br m,
CHOH); 4.80–5.50 (4H, br m, 2 × CH=CH2); 5.65–6.15 (2H, br m, 2 × CH=CH2); 7.00–7.65 (5H, m,
13
arom). C NMR: δ 137.0, 131.2, 130.6, 129.2, 128.5, 125.9, 116.8, 116.5, 70.2, 65.9, 30.7, 30.0. MS,
m/z: 215 ([M+1]+), 198, 186, 174, 170, 158, 146, 129, 117, 91 (base peak), 77, 68, 63, 55.30 Anal. Calcd
for C14H17NO: C, 78.10; H, 7.96; N, 6.51. Found C, 78.34; H, 7.81; N, 6.66.

cis-1-Allyl-2-(1-hydroxy-3-butenyl)-3-phenylaziridine (6a) – By close analogy to the preparation of 5a,
aziridine (4a) was alkylated with allylmagnesium bromide in diethyl ether at –20 °C. After work-up and
chromatography (ether/light petroleum 80:20), the two diastereoisomers were isolated in 26% overall
yield in 64:36 ratio.
1st eluted: orange thick oil; 1H NMR (200 MHz): δ 1.77 (1H, dd, J 8.0, 6.7, PhCHCH), 1.90–2.20 (2H, m,
CHOHCH2), 2.45 (1H, br s, OH), 2.66 (1H, d, J 6.7, PhCH), 2.96 (1H, ddt, J 14.0, 5.9, 1.4, NCH2),
2.99–3.08 (1H, m, CHOH), 3.17 (1H, ddt, J 13.8, 5.7, 1.4, NCH2), 4.80–4.95 (2H, m, CH=CH2), 5.05
(1H, dq, J 10.3, 1.3, CH=CH2), 5.18 (1H, dq, J 17.2, 1.6, CH=CH2), 5.54 (1H, ddt, J 16.5, 9.5, 6.5,
13
NCH2CH=), 5.92 (1H, ddt, J 17.2, 10.3, 5.9, CHOHCH2CH=), 7.09–7.34 (5H, m, arom). C NMR: δ
138.1, 136.3, 135.5, 129.5, 128.8, 128.3, 118.6, 118.5, 69.7, 64.6, 52.3, 48.0, 40.5. MS, m/z: 229 ([M+1]+,
2%), 228 (13), 212 (10), 188 (26), 158 (22), 118 (35), 91 (100), 77 (20), 55 (6). Anal. Calcd for
C15H19NO: C, 78.56; H, 8.35; N, 6.11. Found C, 78.78; H, 8.29; N, 6.19.
1
2nd eluted: orange oil; H NMR (200 MHz): δ 1.85 (1H, dd, J 8.5, 6.4, NCHPh); 1.95–2.15 (2H, m,
CHOHCH2); 2.50 (1H, br, OH); 2.72 (1H, d, J 6.4, PhCH); 3.04 (1H, ddt, J 13.9, 5.6, 1.5, NCH2); 3.19
(1H, ddt, J 13.9, 6.1, 1.4, NCH2); 3.26–3.32 (1H, m, CHOH); 4.98–5.09 (2H, m, CH=CH2); 5.12 (1H, dq,
J 10.1, 1.6, CH=CH2); 5.22 (1H, dq, J 17.6, 1.6, CH=CH2); 5.79 (1H, ddt, J 16.6, 10.4, 7.0, NCH2CH=);
5.96 (1H, ddt, J 17.6, 10.1, 6.3, CHCH2CH=); 7.15–7.48 (5H, m, arom). 13C NMR: δ 139.2, 136.8, 134.9,
128.3, 127.4, 127.0, 117.0, 116.3, 66.8, 63.0, 50.7, 45.8, 37.6. MS, m/z: 229 ([M+1]+, 2%), 228 (13), 212
(10), 188 (26), 158 (22), 118 (35), 91 (100), 77 (20), 55 (6). Anal. Calcd for C15H19NO: C, 78.56; H,
8.35; N, 6.11. Found C, 78.83; H, 8.18; N, 6.28.
trans-1-Allyl-2-(1-hydroxy-3-butenyl)-3-phenylaziridine (6b) – Similarly as above, alkylation of 4b
with allylmagnesium bromide gave the title compound in 40% total yield as a mixture of separable
diastereoisomers (ether/light petroleum 80:20) in 50:50 ratio.
1
1st eluted: yellow oil; H NMR (200 MHz): δ 2.26 (1H, t, J 3.6, PhCHCH), 2.40 (2H, t, J 5.5,
CHOHCH2), 2.61 (1H, dd, J 14.3, 5.9, NCH2), 2.93 (2H, J 14.3, 5.0, OH and NCH2), 3.34 (1H, d, J 3.5,
PhCH), 3.93 (1H, dt, J 3.8, 6.3, CHOH), 4.95–5.26 (2 × 2H, m, CH=CH2), 5.68–6.10 (2 × 1H, m,
13
CH=CH2), 7.15–7.45 (5H, m, arom). C NMR: δ 136.8, 135.7, 131.8, 129.5, 129.3, 119.0, 117.5, 69.5,
55.2, 47.1, 43.5, 40.8 (quaternary C not seen). MS, m/z: 229 ([M+1]+, 3%), 228 (9), 212 (8), 188 (35),
158 (18), 118 (39), 91 (100), 77 (25), 55 (10). Anal. Calcd for C15H19NO: C, 78.56; H, 8.35; N, 6.11.
Found C, 78.67; H, 8.43; N, 6.30.
1
2nd eluted: yellow oil; H NMR (200 MHz): δ 2.24 (1H, dd, J 6.0, 3.6, PhCHCH), 2.44 (2H, t, J 6.7,
CHOHCH2), 2.64 (1H, dd, J 14.0, 6.3, NCH2), 2.86 (1H, dd, J 14.0, 5.5, NCH2), 3.09 (1H, br s, OH),
3.26 (1H, d, J 3.3, PhCH), 3.59 (1H, q, J 5.5, CHOH), 4.96–5.21 (2 × 2H, m, CH=CH2), 5.68-6.10 (2 ×
1H, m, CH=CH2), 7.14–7.50 (5H, m, arom). 13C NMR: δ 136.9, 135.7, 131.7, 129.5, 129.3, 118.9, 118.1,

72.1, 55.7, 45.8, 41.8, 31.7 (quaternary C not seen). MS, m/z: 229 ([M+1]+, 3%), 228 (9), 212 (8), 188
(35), 158 (18), 118 (39), 91 (100), 77 (25), 55 (10). Anal. Calcd for C15H19NO: C, 78.56; H, 8.35; N,
6.11. Found C, 78.71 H, 8.60; N, 6.36.
cis-1-Allyl-2-(1-hydroxy-4-pentenyl)-3-phenylaziridine (7a) – Alkylation of aziridine (4a) with
but-3-enylmagnesium bromide (prepared from commercially available 4-bromo-1-butene) in ether at
–78 °C, followed by usual work-up provided the title aziridine (7a) in 52% overall yield as a mixture of
two diastereoisomers in 62:38 ratio, which were amenable to separation by chromatography (ether/light
petroleum 70:30).
1st eluted: yellow oil; 1H NMR (200 MHz): δ 1.55–1.80 (2H, m, CH2CH2CH=CH2), 1.81 (1H, dd, J 8.3,
6.5, PhCHCH), 1.98–2.36 (2H, m, CHOHCH2), 2.71 (1H, d, J 6.5, PhCH), 3.04 (1H, dd, J 13.8, 5.8,
NCH2), 3.17 (1H, dt, J 4.1, 8.3, CHOH), 3.22 (1H, dd, J 13.8, 6.0, NCH2), 4.90–5.35 (4H, m, CH=CH2),
5.73–6.10 (2H, m, CH=CH2), 7.17–7.50 (5H, m, arom). 13C NMR: δ 138.5, 137.0, 135.0, 128.3, 127.5,
126.9, 116.9, 114.6, 69.1, 63.1, 50.9, 45.5, 34.7, 29.7. MS, m/z: 243 ([M+1]+, 2%), 242 (14), 226 (13),
202 (27), 158 (19), 118 (30), 91 (100), 77 (23), 55 (7). Anal. Calcd for C16H21NO: C, 78.97; H, 8.70; N,
5.76. Found C, 79.11; H, 8.79; N, 5.62.
2nd eluted: yellow oil; 1H NMR (200 MHz): δ 1.33–1.65 (2H, m, CH2CH2CH=CH2), 1.84 (1H, dd, J 8.1,
6.7, PhCHCH), 1.90–2.02 (2H, m, CHOHCH2), 2.67 (1H, br s, OH), 2.76 (1H, d, J 6.7, PhCH),
2.98–3.10 (2H, m, NCH2 and CHOH), 3.29 (1H, dd, J 13.8, 5.7, NCH2), 4.74-5.40 (4H, m, CH=CH2),
5.56 (1H, ddt, J 16.7, 10.3, 6.5, CH=CH2), 6.15 (1H, ddt, J 17.2, 10.3, 5.8, CH=CH2), 7.10–7.52 (5H, m,
arom). 13C NMR: δ 138.1, 136.8, 135.0, 128.1, 127.4, 126.9, 117.1, 114.4, 68.3, 63.3, 51.7, 46.7, 33.7,
29.1. MS, m/z: 243 ([M+1]+, 2%), 242 (14), 226 (13), 202 (27), 158 (19), 118 (30), 91 (100), 77 (23), 55
(7). Anal. Calcd for C16H21NO: C, 78.97; H, 8.70; N, 5.76. Found C, 79.25; H, 8.83; N, 5.55.
trans-1-Allyl-2-(1-hydroxy-4-pentenyl)-3-phenylaziridine (7b) – trans-Aziridine (7b) was prepared by
close analogy to the procedure described above. Chromatography with ether/light petroleum 80:20 as the
eluant afforded the two diastereoisomers in 41:59 ratio in 41% yield. For the slow-eluting
diastereoisomer, 1H NMR spectroscopy showed the presence of two invertomers at nitrogen, due to slow
nitrogen inversion on the NMR scale.
1
1st eluted: yellowish oil; H NMR (200 MHz): δ 1.69 (2H, q, J 7.1, CH2), 2.12–2.45 (3H, m, CH2 and
PhCHCH), 2.61 (1H, dd, J 14.4, 5.9, NCH2), 2.92 (1H, dd, J 14.4, 5.1, NCH2), 3.22 (1H, br s, -OH), 3.32
(1H, d, J 3.5, PhCH), 3.88 (1H, dt, J 3.9, 6.2, CHOH), 4.94–5.14 (4H, m, CH=CH2), 5.70–5.99 (2H, m,
CH=CH2), 7.20–7.45 (5H, m, arom). 13C NMR: δ 138.4, 135.5, 133.5, 130.3, 128.2, 127.9, 116.0, 114.7,
68.0, 53.9, 46.3, 41.9, 34.0, 29.7. MS, m/z: 243 ([M+1]+, 4%), 242 (11), 226 (10), 202 (31), 158 (14), 118
(41), 91 (100), 77 (22), 55 (8). Anal. Calcd for C16H21NO: C, 78.97; H, 8.70; N, 5.76. Found C, 78.79; H,
8.59; N, 5.84.

1
2nd eluted: yellowish oil; H NMR (200 MHz): δ 1.59–1.89 (2H, m, CH2), 2.09–2.45 (4H, m, CH2,
PhCHCH and OH), 2.69 (1H, dd, J 14.1, 6.2, NCH2), 2.86 (1H, dd, J 14.1, 5.6, NCH2), 3.25 (1H, d, J 3.5,
PhCH), 3.40–3.70 (1H, m, CHOH), 4.92–5.21 (4H, m, CH=CH2), 5.71–6.97 (2H, m, CH=CH2),
7.20–7.51 (5H, m, arom). 13C NMR: δ 138.3, 135.4, 130.3, 128.1, 128.0, 127.0, 116.7, 114.8, 71.1, 54.4,
47.6, 44.7, 34.8, 29.8. MS, m/z: 243 ([M+1]+, 4%), 242 (11), 226 (10), 202 (31), 158 (14), 118 (41), 91
(100), 77 (22), 55 (8). Anal. Calcd for C16H21NO: C, 78.97; H, 8.70; N, 5.76. Found C, 79.21; H, 8.85; N,
5.89.
Protection of aziridines (6,7a-b). General procedure. – The aziridine (0.5 mmol) was dissolved in 2
mL anhydrous dichloromethane and DMAP (79 mg, 0.65 mmol) and TBDMSCl (90 mg, 0.6 mmol) were
added at rt under magnetic stirring. When TLC showed disappearance of the starting material, the
reaction mixture was diluted with 13 mL of CH2Cl2, washed with water (5 mL), dried and concentrated
in vacuo. Final purification was achieved by means of column chromatography, using the eluant
indicated below [in square brackets].
cis-1-Allyl-2-(1-tert-butyldimethylsilyloxy-3-butenyl)-3-phenylaziridine (8a) – After chromatography
1
[light petroleum/ether 90:10], the title compound was obtained as an oil in 60% yield. H NMR (200
MHz): δ 0.08 (3H, s, tBuMe2Si), 0.21 (3H, s, tBuMe2Si), 0.97 (9H, s, tBuMe2Si), 1.86 (1H, dd, J 8.8, 6.7,
PhCHCH), 1.93–2.05 (2H, m, SiOCHCH2), 2.59 (1H, d, J 6.7, PhCH), 2.72 (1H, ddt, J 14.1, 6.2, 1.4,
NCH2), 3.19 (1H, dt, J 8.8, 5.5, CHOSi), 3.57 (1H, ddt, J 14.1, 5.2, 1.5, NCH2), 4.81–4.98 (2H, m,
CH=CH2), 5.10 (1H, dq, J 10.5, 2.1, CH=CH2), 5.26 (1H, dq, J 17.2, 2.1, CH=CH2), 5.65 (1H, ddt, J
16.9, 10.3, 7.1, CH=CH2), 6.01 (1H, dddd, J 17.2, 10.5, 6.1, 5.2, CH=CH2), 7.19–7.45 (5H, m, arom).
13C NMR: δ 137.8, 135.6, 134.8, 127.9, 127.5, 126.6, 116.6, 116.1, 71.3, 63.3, 51.3, 45.5, 40.0, 26.0,
18.2, –4.0, –4.6. MS, m/z: 343 ([M]+, 11%), 302 (72), 286 (66), 216 (29), 204 (48), 185 (23), 175 (25),
131 (50), 115 (13), 73 (100). Anal. Calcd for C21H33NOSi: C, 73.41; H, 9.68; N, 4.08. Found C, 73.54; H,
9.79; N, 4.21.
trans-1-Allyl-2-(1-tert-butyldimethylsilyloxy-3-butenyl)-3-phenylaziridine (8b) – Chromatography
[light petroleum/diethyl ether 70:30] afforded the desired product (8b) as a yellow oil, albeit in low yield
(34%). 1H NMR spectroscopy showed broad and poorly resolved signals, indicating the presence of two
t
t
invertomers at nitrogen. 1H NMR (200 MHz): δ 0.13 (3H, br s, BuMe2Si), 0.16 (3H, s, BuMe2Si), 0.96
(9H, s, tBuMe2Si), 2.21 (1H, dd, J 7.2, 3.7, PhCHCH), 2.30–2.58 (2H, m, SiOCHCH2), 2.60–2.90 (2H, br
m, NCH2), 3.11 (1H, d, J 3.7, PhCH), 3.51 (1H, br q, J 6.2, CHOSi), 4.88–5.27 (4H, m, CH=CH2),
13
5.67–6.08 (2H, m, CH=CH2), 7.05–7.36 (5H, m, arom). C NMR: δ 137.5, 135.9, 131.8, 128.4, 129.1,
118.6, 117.5, 76.5, 56.3, 48.4, 45.9, 42.2, 27.3, 19.5, –2.8, –3.2. MS, m/z: 343 ([M]+, 11%), 302 (72), 286

(66), 216 (29), 204 (48), 185 (23), 175 (25), 131 (50), 115 (13), 73 (100). Anal. Calcd for C21H33NOSi: C,
73.41; H, 9.68; N, 4.08. Found C, 73.49; H, 9.73; N, 4.25.
cis-1-Allyl-2-(1-tert-butyldimethylsilyloxy-4-pentenyl)-3-phenylaziridine (9a) – Purification by
column chromatography using the same eluant as above provided the title compound as a yellow oil in
1
t
t
39% yield. H NMR (200 MHz): δ –0.41 (6H, s, BuMe2Si), 0.79 (9H, s, BuMe2Si), 1.68–1.84 (2H, m,
CH2), 1.85 (1H, dd, J 8.1, 6.3, PhCHCH), 2.09–2.29 (2H, m, CH2), 2.63 (1H, d, J 6.3, PhCH), 2.99 (1H,
ddt, J 14.1, 5.6, 1.3, NCH2), 3.22-3.31 (2H, m, NCH2 and CHOSi), 4.90–5.30 (4H, m, CH=CH2),
13
5.75–6.08 (2H, m, CH=CH2), 7.22–7.32 (5H, m, arom). C NMR: δ 140.4, 138.2, 136.6, 129.3, 129.2,
128.1, 118.0, 115.6, 68.7, 64.9, 53.3, 47.9, 36.9, 30.3, 27.2, 19.3, –3.5, –3.9. MS, m/z: 357 ([M]+, 9%),
342 (2), 316 (13), 300 (32), 226 (6), 216 (20), 198 (64), 184 (44), 175 (16), 144 (17), 115 (16), 106 (20),
104 (20), 91 (25). Anal. Calcd for C22H35NOSi: C, 73.89; H, 9.87; N, 3.92. Found C, 74.04; H, 9.91; N,
3.86.
trans-1-Allyl-2-(1-tert-butyldimethylsilyloxy-4-pentenyl)-3-phenylaziridine
(9b)
–
After
chromatography [light petroleum/ether 50:50] the title compound was isolated as a yellow oil in 75%
1
t
t
t
yield. H NMR (200 MHz): δ 0.00 (3H, s, BuMe2Si), 0.06 (3H, s, BuMe2Si), 0.89 (9H, s, BuMe2Si),
1.63–1.95 (2H, m, CH2), 2.05–2.43 (3H, m, CH2 and PhCHCH), 2.56 (1H, dd, J 13.5, 6.7, NCH2), 2.84
(1H, dd, J 13.5, 5.2, NCH2), 3.18 (1H, d, J 2.5, PhCH), 3.32–3.48 (1H, m, CHOSi), 4.90–5.15 (4H, m,
13
CH=CH2), 5.75–6.00 (2H, m, CH=CH2), 7.25-–7.40 (5H, m, arom). C NMR: δ 138.8, 135.7, 130.3,
128.0, 127.6, 125.9, 116.5, 114.3, 74.3, 55.0, 47.6, 46.8, 35.5, 29.3, 25.8, 18.0, –4.0, –4.8. MS, m/z: 357
([M]+, 9%), 342 (2), 316 (13), 300 (32), 226 (6), 216 (20), 198 (64), 184 (44), 175 (16), 144 (17), 115
(16), 106 (20), 104 (20), 91 (25). Calcd for C22H35NOSi: C, 73.89; H, 9.87; N, 3.92. Found C, 74.15; H,
9.99; N, 3.79.
Carbonylation of 1,2-dialkenylaziridines (5a-9a, 8b-9b). Typical procedure. – The aziridine (0.2–0.5
mmol) was dissolved in anhydrous and oxygen-free 1,2-dimethoxyethane (5–10 mL) in a stainless steel
pressure vessel equipped with a glass liner and a stirring bar. Dicobalt octacarbonyl was then added (1/12
ratio with the aziridine), the autoclave was purged with carbon monoxide and finally charged with 500
psi CO. After 20 h at 110 °C in an oil bath, the system was cooled to rt and CO was slowly released. The
brown clear solution was left to stir in contact with the air and ether (10 mL) was added to favor catalyst
decomposition. The cloudy violet suspension thus obtained was filtered on a short Celite® pad, the clear
solution was rotary evaporated and purified by column chromatography using the eluant indicated below
[in square brackets] to afford the ring-expanded product in pure form.

trans-1-Allyl-4-(1-hydroxy-2-propenyl)-3-phenylazetidin-2-one (10a) – From cis-aziridine (5a),
1
β-lactam (10a) [ether/light petroleum 70:30] was obtained as a yellow oil in 66% yield. H NMR (200
MHz): δ 1.44 (1H, s, CHOH), 3.68 (1H, dd, J 3.2, 2.4, PhCHCH), 3.78 (1H, ddq, J 15.4, 7.0, 1.5, NCH2),
4.15 (1H, ddt, J 15. 8, 5.7, 1.5, NCH2), 4.31 (1H, d, J 2.5, PhCH), 4.48 (1H, m, CHOH), 5.27 (1H, dq, J
10.0, 1.5, NCH2CH=CH2), 5.32 (1H, dq, J 18.0, 1.5, NCH2CH=CH2), 5.32 (1H, dt, J 10.0, 1.4,
CHOHCH=CH2), 5.47 (1H, dt, J 18.0, 1.4, CHOHCH=CH2), 5.77–6.03 (2H, m, CH=CH2), 7.17–7.40
(5H, m, arom). 13C NMR: δ 167.0, 136,.4, 129.2, 127.9, 127.7, 119.3, 118.4, 71.1, 63.8, 55.5, 44.0, 30.7.
MS, m/z: 244 ([M+1]+, 2%), 186 (5), 160 (100), 145 (23), 117 (53), 105 (80), 91 (57), 82 (21), 77 (25),
69 (17). Anal. Calcd for C15H17NO2: C, 74.05; H, 7.04; N, 5.76. Found C, 74.17; H, 7.20; N, 5.81.
trans-1-Allyl-4-(1-hydroxy-3-butenyl)-3-phenylazetidin-2-one (11a) – The title β-lactam was obtained
1
as a yellow oil in 42% yield from carbonylation of cis-aziridine (6a) [ether/light petroleum 70:30]. H
NMR (200 MHz): δ 2.10–2.50 (3H, m, OH and CHOHCH2), 3.61 (1H, dd, J 7.5, 2.4, PhCHCH),
3.76–3.90 (1H, m, CHOH), 3.94 (1H, dd, J 15.5, 6.6, NCH2), 3.98 (1H, d, J 2.5, PhCH), 4.17 (1H, ddt, J
15.5, 5.5, 1.5, NCH2), 5.05–5.37 (4H, m, CH=CH2), 5.68–6.02 (2H, m, CH=CH2), 7.22–7.39 (5H, m,
arom). 13C NMR: δ 167.9, 134.8, 133.1, 132.8, 128.9, 127.6, 127.5, 119.3, 118.3, 73.3, 64.2, 57.1, 44.6,
38.8. MS, m/z: 258 ([M+1]+, 11%), 216 (8), 174 (83), 158 (33), 143 (13), 133 (100), 115 (11), 55 (13).
Anal. Calcd for C16H19NO2: C, 74.68; H, 7.44; N, 5.44. Found C, 74.55; H, 7.29; N, 5.54.
trans-1-Allyl-4-(1-hydroxy-4-pentenyl)-3-phenylazetidin-2-one (12a) – From cis-aziridine (7a), the
title compound [ether/light petroleum 70:30] was obtained as a yellow liquid in 53% yield. 1H NMR (200
MHz): δ 1.46–1.70 (2H, m, CH2), 2.04–2.37 (2H, m, CH2), 2.49 (1H, d, J 4.9, OH), 3.58 (1H, dd, J 7.0,
2.4, PhCHCH), 3.76–3.85 (1H, m, CHOH), 3.85–4.01 (2H, m, NCH2 and PhCH), 4.15 (1H, ddt, J 15.6,
5.5, 1.4, NCH2), 4.96–5.11 (2H, m, CH=CH2), 5.20–5.36 (2H, m, CH=CH2), 5.69–6.00 (2H, m,
CH=CH2), 7.21–7.42 (5H, m, arom). 13C NMR: δ 168.2, 137.7, 134.9, 132.9, 128.9, 127.5, 127.4, 118.4,
115.6, 73.5, 64.8, 57.0, 44.6, 33.3, 29.7. MS, m/z: 272 ([M+1]+, 30%), 188 (16), 170 (18), 146 (14), 133
(100), 115 (23), 105 (63), 91 (35), 83 (14). Anal. Calcd for C17H21NO2: C, 75.25; H, 7.80; N, 5.16. Found
C, 75.38; H, 7.92; N, 5.04.
trans-1-Allyl-4-(1-tert-butyldimethylsilyloxy-3-butenyl)-3-phenylazetidin-2-one (13a)
–
From
cis-aziridine (8a), β-lactam (13a) [ether/light petroleum 50:50] was obtained as a yellow oil in 63% yield.
1H NMR (200 MHz): δ 0.10 (3H, s, tBuMe2Si), 0.13 (3H, s, tBuMe2Si), 0.92 (9H, s, tBuMe2Si), 2.39 (2H,
m, SiOCHCH2CH=), 3.72 (1H, dd, J 4.3, 2.4, PhCHCH), 3.73 (1H, ddq, J 15.7, 6.8, 1.0, NCH2), 4.00
(1H, dt, J 4.6, 5.9, CHOSi), 4.09 (1H, d, J 2.4, PhCH), 4.26 (1H, ddt, J 15.7, 5.2, 1.6, NCH2), 4.93–5.09
(2H, m, CH=CH2), 5.21–5.35 (2H, m, CH=CH2), 5.66–5.99 (2H, m, CH=CH2), 7.20–7.39 (5H, m, arom).

13C NMR: δ 169.7, 136.7, 134.9, 133.8, 130.1, 128.9, 128.7, 119.7, 119.6, 74.0,64.0, 58.1, 45.6, 40.1,
27.2, 1.4, –2.7, –3.2. MS, m/z: 370 ([M–1]+, 2%), 330 (3), 314 (2), 286 (2), 248 (23), 247 (100), 231 (6),
196 (45), 155 (7), 115 (13), 75 (21), 73 (44). Anal. Calcd for C22H33NO2Si: C, 71.11; H, 8.95; N, 3.77.
Found C, 71.25; H, 9.12; N, 3.69.
trans-1-Allyl-4-(1-tert-butyldimethylsilyloxy-4-pentenyl)-3-phenylazetidin-2-one
(14a)
–
Carbonylation of cis-aziridine (9a) afforded the title β-lactam [light petroleum/ether 70:30] as a yellow
1
t
t
oil in 21% yield. H NMR (200 MHz): δ 0.11 (3H, s, BuMe2Si), 0.13 (3H, s, BuMe2Si), 0.94 (9H, s,
tBuMe2Si), 1.48–1.74 (2H, m, CH2), 2.01–2.18 (2H, m, CH2), 3.47 (1H, ddq, J 15.6, 6.4, 1.0, NCH2),
3.67 (1H, t, J 2.1, PhCHCH), 4.01 (1H, td, J 5.9, 1.7, CHOSi), 4.25–4.40 (2H, m, NCH2 and PhCH),
4.90–5.03 (2H, m, CH=CH2), 5.20–5.32 (2H, m, CH=CH2), 5.63–5.96 (2H, m, CH=CH2), 7.24–7.42 (5H,
m, arom). 13C NMR: δ 168.1, 137.6, 132.1, 128.8, 127.6, 127.3, 118.6, 115.2, 68.7, 63.2, 54.9, 43.2, 33.9,
29.7, 29.4, 25.8, –4.8, –5.0. MS, m/z: 385 (M+, 1%), 302 (9), 247 (54), 245 (76), 210 (100), 167 (16), 168
(20), 129 (27), 115 (23), 75 (91), 73 (59). Anal. Calcd for C23H35NO2Si: C, 71.64; H, 9.15; N, 3.63.
Found C, 71.71; H, 9.30; N, 3.86.
Ring-closing metathesis (RCM) cyclizations. Typical procedure – The 1,4-dialkenyl-β-lactam (0.284
mmol) was dissolved in 10 mL of anhydrous and degassed dichloromethane in a 50-mL Schlenk flask.
Grubbs’ catalyst I (0.028 mmol) was added under argon flow and the brownish-violet solution was
stirred at room temperature under inert atmosphere. After 21 h, the flask was opened and the mixture
exposed to air under vigorous stirring for a couple of hours to favour catalyst decomposition. The
mixture was then evaporated to dryness under reduced pressure and purified by column chromatography
using the eluant indicated below [in square brackets].
trans-5-Hydroxy-7-phenyl-1-azabicyclo[4.2.0]oct-3-en-8-one (15a) – Ring-closing metathesis of 10a
afforded bicyclic product (15a) [ether/light petroleum 70:30] as a yellow oil in 73% yield. 1H NMR (200
MHz): δ 1.44 (1H, s, CHOH), 3.31 (1H, dd, J 7.5, 1.1, PhCHCH), 3.55 (1H, dd, J 19.0, 1.5, NCH2), 4.08
(1H, br d, J 19.0, NCH2), 4.16 (1H, br s, PhCH), 4.32 (1H, t, J 6.7, CHOH), 5.70–5.90 (2H, m, CH=CH),
13
7.20–7.42 (5H, m, arom). C NMR: δ 168.4, 135.6, 133.0, 131.2, 129.5, 128.0, 124.2, 69.2, 63.2, 38.8,
31.3. MS, m/z: 215 ([M]+, 4%), 198 (5), 196 (1),172 (100), 159 (12), 143 (9), 128 (14), 124 (24), 105
(25), 91 (69), 77 (25), 68 (16), 55 (10). Anal. Calcd for C13H13NO2: C, 72.54; H, 6.09; N, 6.51. Found C,
72.73; H, 5.98; N, 6.63.
trans-6-Hydroxy-8-phenyl-1-azabicyclo[5.2.0]non-3-en-9-one (16a)
–
After chromatographic
purification [ether/light petroleum 90:10], the title compound was obtained from trans-β-lactam (11a) as

1
a yellow oil in 50% yield. H NMR (200 MHz): δ 2.20 (1H, br s, OH), 2.32–2.50 (1H, m,
CHOHCH2CH=), 2.80 (1H, dt, J 16.7, 6.6, CHOHCH2CH=), 3.65 (1H, m, NCH2), 3.84 (1H, t, J 2.4,
PhCHCH), 4.22 (1H, br s, CHOH), 4.48 (1H, d, J 2.4, PhCH), 4.52 (1H, dd, J 17.2, 5.4, NCH2),
5.56–5.82 (2H, m, CH=CH), 7.21–7.40 (5H, m, arom). 13C NMR: δ 168.1, 128.8, 128.0, 127.5, 127.4,
125.1, 67.3, 66.2, 56.7, 40.9, 33.5. MS, m/z: 229 (M+, 2%), 134 (10), 133 (100), 118 (3), 115 (16), 105
(7), 91 (8), 77 (7), 55 (18). Anal. Calcd for C14H15NO2: C, 73.34; H, 6.59; N, 6.11. Found C, 73.21; H,
6.71; N, 6.31.
trans-7-Hydroxy-9-phenyl-1-azabicyclo[6.2.0]dec-3-en-10-one (17a) – RCM of 12a provided fused
1
β-lactam (17a) [ether/light petroleum 90:10] in 88% yield. H NMR (200 MHz): δ 1.45–2.50 (4H, m,
CH2), 2.98 (1H, br s, -OH), 3.80–4.23 (4H, m, NCH2, PhCHCH and CHOH), 3.66 (1H, d, J 2.2, PhCH),
5.64–5.83 (1H, m, CH=), 6.11 (1H, q, J 8.8, CH=), 7.18–7.38 (5H, m, arom). 13C NMR: δ 167.7, 138.0,
128.9, 128.8, 127.4, 127.3, 123.2, 68.7, 64.1, 55.8, 36.8, 35.2, 31.9. MS, m/z: 244 ([M+1]+, 2%), 243 (7),
215 (2), 133 (100), 115 (33), 105 (56), 104 (48), 91 (42), 77 (24), 68 (25), 55 (27). Anal. Calcd for
C15H17NO2: C, 74.05; H, 7.04; N, 5.76. Found C, 74.21; H, 7.11; N, 5.66.
trans-6-tert-Butyldimethylsilyloxy-8-phenyl-1-azabicyclo[5.2.0]non-3-en-9-one (18a) – The title
compound was obtained as a dark oil from trans-β-lactam (13a) in 66% yield after chromatographic
t
purification [diethyl ether/light petroleum 70:30]. 1H NMR (200 MHz): δ 0.04 (3H, s, BuMe2Si), 0.09
t
t
(3H, s, BuMe2Si), 0.89 (9H, s, BuMe2Si), 2.21 (1H, ddd, J 16.2, 6.6, 2.2, SiOCHCH2CH=), 2.58–2.78
(1H, m, SiOCHCH2CH=), 3.50–3.65 (1H, m, NCH2), 3.83 (1H, dd, J 4.5, 2.0, PhCHCH), 4.27 (1H, ddd,
J 9.5, 4.6, 2.3, CHOSi), 4.35 (1H, d, J 2.0, PhCH), 4.41–4.56 (1H, m, NCH2), 5.47–5.72 (2H, m, CH=),
7.19–7.35 (5H, m, arom). 13 C NMR: δ 169.3, 137.0, 130.0, 129.1, 128.6, 128.2, 126.4, 71.5, 66.3, 57.4,
42.8, 33.9, 27.1, 19.4, –3.4, –3.5. MS, m/z: 286 ([M–15]+, 2%), 287 (3), 286 (15), 248 (19), 247 (100),
232 (9), 210 (2), 189 (5), 168 (20), 166 (9), 115 (9), 100 (6), 91 (8), 73 (36). Anal. Calcd for
C20H29NO2Si: C, 69.92; H, 8.51; N, 4.08. Found C, 70.09; H, 8.62; N, 4.20.
trans-7-tert-Butyldimethylsilyloxy-9-phenyl-1-azabicyclo[6.2.0]dec-3-en-10-one (19a) – RCM of 14a
gave the title bicyclic β-lactam [ether/light petroleum 70:30] as a dark oil in 70% yield. 1H NMR (200
t
t
t
MHz): δ 0.10 (3H, s, BuMe2Si), 0.11 (3H, s, BuMe2Si), 0.89 (9H, s, BuMe2Si), 1.50–2.50 (4H, m,
CH2), 3.66 (1H, dd, J 8.9, 2.1, PhCHCH), 3.71–3.83 (1H, m, CHOSi), 3.86 (1H, dd, J 14.5, 7.1, NCH2),
4.03 (1H, dd, J 14.5, 7.6, NCH2), 4.10 (1H, d, J 2.1, PhCH), 5.73 (1H, dt, J 10.2, 7.2, CH=), 5.95 (1H, dt,
J 10.2, 7.9, CH=), 7.23–7.43 (5H, m, arom). 13C NMR: δ 165.5, 135.8, 128.4, 127.6, 127.0, 123.1, 75.3,
65.6, 57.1, 36.3, 36.0, 25.8, 22.5, –4.2, –4.4. MS, m/z: 357 (M+, 2%), 301 (23), 300 (100), 257 (29), 247
(49), 183 (30), 155 (38), 141 (60), 129 (50), 117 (48), 115 (49), 91 (70), 75 (71), 73 (83), 57 (83). Anal.
Calcd for C21H31NO2Si: C, 70.54; H, 8.74; N, 3.92. Found C, 70.71; H, 8.65; N, 3.98.

2-[3-(tert-Butyldimethylsilyloxy)-1-phenylhexa-1,5-dienyl]-5,6-dihydro-4H-[1,3]oxazine (20b)
–
Carbonylation of trans-aziridine (8b) afforded the title compound in 17% total yield as a mixture of E/Z
stereoisomers in 70:30 ratio, which were separated by chromatography [ether/light petroleum 70:30].
1
t
t
1st eluted: oil; H NMR (200 MHz): δ 0.13 (3H, s, BuMe2Si), 0.14 (3H, s, BuMe2Si), 0.95 (9H, s,
tBuMe2Si), 1.85–2.10 (2H, m, CH2CH2CH2), 2.18–2.50 (4H, m, CH2CH=CH2 and NCH2), 3.33 (2H, dt, J
7.1, 3.0, CH2O), 4.71 (1H, ddd, J 6.1, 4.6, 1.2, CHOSi), 4.98–5.15 (2H, m, CH2=CH), 5.78–6.01 (1H, m,
CH2=CH), 6.67 (1H, s, PhC=CH), 7.20–7.40 (5H, m, arom). Anal. Calcd for C22H33NO2Si: C, 71.11; H,
8.95; N, 3.77. Found C, 71.02; H, 9.05; N, 3.81.
1
t
t
2nd eluted: oil; H NMR (200 MHz): δ –0.21 (3H, s, BuMe2Si), –0.18 (3H, s, BuMe2Si), 0.81 (9H, s,
tBuMe2Si), 1.55–1.85 (2H, m, CH2CHOSi), 1.95–2.20 (2H, m, CH2CH2CH2), 2.35–2.55 (2H, m, NCH2),
3.64 (1H, dt, J 10.3, 6.9, CH2O), 4.02 (1H, dt, J 10.3, 6.9, CH2O), 4.88 (1H, t, J 6.3, CHOSi), 5.03–5.18
(2H, m, CH2=CH), 5.85 (1H, ddt, J 17.8, 10.3, 7.0, CH2=CH), 6.66 (1H, s, PhC=CH), 7.20–7.45 (5H, m,
arom). Anal. Calcd for C22H33NO2Si: C, 71.11; H, 8.95; N, 3.77. Found C, 71.27; H, 9.11; N, 3.89.
2-[3-(tert-Butyldimethylsilyloxy)-1-phenylhepta-1,6-dienyl]-5,6-dihydro-4H-[1,3]oxazine (21b) –
Similarly as above, carbonylation of trans-aziridine (9b) provided the title oxazine in 38% overall yield
as a 60:40 mixture of E/Z stereoisomers which were amenable to separation by column chromatography
[ether/light petroleum 50:50].
1
t
t
1st eluted: oil; H NMR (200 MHz): δ 0.14 (3H, s, BuMe2Si), 0.15 (3H, s, BuMe2Si), 0.96 (9H, s,
tBuMe2Si), 1.48–1.83 (2H, m, CH2CHOSi), 1.88–2.11 (2H, m, CH2CH2CH2), 2.12–2.26 (2H, m,
CH2=CHCH2), 2.32–2.45 (2H, m, NCH2), 3.29–3.42 (2H, m, CH2O), 4.64 (1H, ddd, J 6.7, 4.3, 1.1,
CHOSi), 4.92–5.09 (2H, m, CH2=CH), 5.85 (1H, ddt, J 17.1, 10.2, 6.5, CH2=CH), 6.65 (1H, s, PhC=CH),
7.18–7.38 (5H, m, arom). 13C NMR: δ 175.0, 138.6, 128.4, 127.9, 127.4, 124.6, 114.5, 72.0, 48.8, 35.2,
31.2, 29.3, 25.9, 19.4, –4.4, –5.0. MS, m/z: 384 ([M–1]+, 1%), 370 (3), 344 (3), 330 (9), 329 (23), 328
(100), 302 (7), 272 (5), 212 (7), 142 (20), 128 (10), 115 (12), 75 (23), 73 (29). Anal. Calcd for
C23H35NO2Si: C, 71.64; H, 9.15; N, 3.63. Found C, 71.59; H, 9.21; N, 3.72.
1
t
t
2nd eluted: oil; H NMR (200 MHz): δ –0.20 (3H, s, BuMe2Si), –0.12 (3H, s, BuMe2Si), 0.84 (9H, s,
tBuMe2Si), 1.64-1.80 (2H, m, CH2CHOSi), 1.97–2.22 (4H, m, CH2CH2CH2 and CH2=CHCH2),
2.38–2.55 (2H, m, NCH2), 3.63 (1H, dt, J 10.5, 6.9, OCH2), 4.01 (1H, dt, J 10.5, 6.9, OCH2), 4.85 (1H, t,
J 6.7, CHOSi), 4.90–5.06 (2H, m, CH2=CH), 5.85 (1H, ddt, J 17.0, 10.3, 6.5, CH2=CH), 6.66 (1H, s,
PhC=CH), 7.20–7.45 (5H, m, arom). 13C NMR: δ 138.2, 129.0, 128.8, 128.1, 127.2, 114.7, 69.0, 51.2,
35.2, 31.4, 29.8, 25.7, 18.8, –4.6, –5.4. MS, m/z: 384 ([M–1]+, 1%), 370 (2), 344 (2), 330 (10), 329 (18),
328 (82), 302 (5), 272 (4), 212 (12), 142 (39), 128 (26), 115 (30), 75 (63), 73 (100). Anal. Calcd for
C23H35NO2Si: C, 71.64; H, 9.15; N, 3.63. Found C, 71.85; H, 9.32; N, 3.79.

ACKNOWLEDGEMENTS
We thank Ministero dell’Istruzione, dell’Università e della Ricerca (MIUR) for financial support
(COFIN 2001). A.S. thanks MIUR for a doctoral fellowship. Spectroscopical assistance from Centro
Interdipartimentale Grandi Strumenti (Università di Modena e Reggio Emilia) has been greatly
appreciated. We are grateful to Prof. A.C. Fabretti (Dipartimento di Chimica) for kindly providing
dry-box facilities. Thanks are due to Professor Irene Moretti, to whom this paper is dedicated, for her
continuous encouragement and committment throughout the years in the field of heterocyclic chemistry.
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