Synthesis of highly substituted 2H-azirine-2-carboxylates via 3-azido-4-oxobut-2-enoates

Article abstract of DOI:10.1002/ejoc.200701072

Phenacyl azides have been transformed into ethyl 4-aryl-3-azido-2-methyl-4- oxobut-2-enoates by base-induced coupling of the starting α-azido ketone with ethyl pyruvate followed by elimination of methanesulfonic acid from the mesylate generated in situ fr

Full text of DOI:10.1002/ejoc.200701072

FULL PAPER
DOI: 10.1002/ejoc.200701072
Synthesis of Highly Substituted 2H-Azirine-2-carboxylates via
3-Azido-4-oxobut-2-enoates[‡]
Tamás Patonay,*[a] József Jeko˝,[b] and Éva Juhász-Tóth[a]
Dedicated to Professor Kálmán Medzihradszky on the occasion of his 80th birthday
Keywords: Azides / Azirines / C–C coupling / Nitrenes / Thermolysis
Phenacyl azides have been transformed into ethyl 4-aryl-3-
azido-2-methyl-4-oxobut-2-enoates by base-induced coup-
ling of the starting α-azido ketone with ethyl pyruvate fol-
lowed by elimination of methanesulfonic acid from the mes-
ylate generated in situ from the labile aldol-type inter-
mediates ethyl 4-aryl-3-azido-2-hydroxy-2-methyl-4-oxobut-
anoates. Thermolysis of ethyl 4-aryl-3-azido-2-methyl-4-
oxobut-2-enoates resulted in the formation of the hitherto un-
known 3-aroyl-2-ethoxycarbonyl-2-methyl-2H-azirines.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
azido-α,β-unsaturated ketones involve the Knoevenagel-
type condensation of phenacyl azides,[2a,9] iodine azide ad-
dition to an α,β-unsaturated ketone,[10] treatment of α,β-
dihalo ketones or the intermediate α-halo-α,β-unsaturated
ketones with sodium azide[8b,8d,11] and ammonium ce-
rium(IV) nitrate mediated oxidative addition of sodium az-
ide to α,β-unsaturated ketones followed by treatment with
sodium acetate.[12]
α-Azido ketones 1 are a synthetically valuable group of
azides that exhibit double reactivity in C–C bond forma-
tion. The electrophilic carbonyl function provides a target
for the attack of carbanions leading to adducts such as
compounds 2; this chemistry has been utilized by Langer
and co-workers[13] (Scheme 1). On the other hand, α-azido
ketones possessing an α-hydrogen show enhanced C–H
acidity due to the anion-stabilizing effect of the azido
group. The controlled generation of carbanions 3 followed
by trapping with various carbon electrophiles results in the
formation of aldol-type products 4 (Scheme 1).
Introduction
Vinyl azides are an important and synthetically useful
class of nitrogen-containing derivatives.[1] The strong inter-
est in this class of compounds is related to their high reac-
tivity in pyrolysis and cycloaddition reactions, and their
easy attack by both electrophiles and nucleophiles. The
chemistry of related allenyl azides has also been re-
viewed.[1e] 2-Azido-1,3-diaryl-2-propen-1-ones (α-azido-
chalcones) represent an interesting subclass of vinyl azides;
their transformations can give various products including
heterocycles depending on the reagents and the reaction
conditions used. Nitrenes generated by thermolysis have led
to the formation of various insertion products;[2] in some
cases azirines have also been obtained among other prod-
ucts in photolytic[3] or microwave-assisted reactions.[4] Cy-
cloadditions to the azide function,[5] aza-Wittig reactions[6]
and their electrolytical properties[7] have also been studied.
Ring-closure of 3-aryl-2-azido-1-(2-hydroxy- or 2-ami-
nophenyl)-2-propen-1-ones by intramolecular conjugate ad-
dition followed by various secondary reactions has led to
the formation of various 3-substituted chromones, flavones
or 4(1H)-quinolones.[8]
In our previous work[14] we have demonstrated that base-
induced reactions between α-azido ketones 1 and either
simple aldehydes or more complex carbonyl compounds
like α-oxo aldehydes provide an efficient method for the
preparation of valuable tri- and tetrafunctionalized syn-
thons. Our method has been successfully used by other re-
search groups. Thus, α-azido ketones have been coupled
with Michael acceptors,[15] aldehydes[16] and various in situ
generated imines.[17] This latter reaction was performed by
using a proline-based organocatalyst as base and gave enan-
tiomerically enriched 2-amino-3-azido-4-oxoalkanoates and
3-amino-2-azido ketones. This pathway represents a new
approach towards chiral, non-racemic 1,2-diamines.
Several methods describing the preparation of these un-
saturated azides have been published in the literature.[1] The
most important procedures for the synthesis of α- or β-
[‡] α-Azido Ketones, Part 5. Part 4: É. Juhász-Tóth, T. Patonay,
Eur. J. Org. Chem. 2002, 3055–3064.
[a] Department of Organic Chemistry, University of Debrecen,
Egyetem tér 1, 4032 Debrecen, Hungary
Fax: +36-52-453-836
E-mail: tpatonay@puma.unideb.hu
[b] Department of Chemistry, College of Nyíregyháza,
Sóstói út 31/b, 4400 Nyíregyháza, Hungary
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T. Patonay, J. Jeko, É. Juhász-Tóth
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FULL PAPER
syn configuration during C–C bond coupling is in accord-
ance with both our previous observations[14] and other re-
ported results.[16,17]
Figure 1. Crystal structure of anti-6b.
Scheme 1. Reactivity of α-azido ketones in C–C bond formation
reactions.
In a previous publication[14c] we reported on the reaction
of phenacyl azides and ethyl pyruvate in the presence of
1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) which afforded
the expected coupling products 3-azido-2-hydroxy-4-oxo-
1
alkanoates in high yield according to TLC and H NMR
studies. However, only one stable product, namely ethyl 3-
azido-2-hydroxy-4-(4-methoxyphenyl)-2-methyl-4-oxobut-
anoate (6b, see Scheme 2), was isolated in 69% yield. In the
other cases, all attempts to isolate the products by column
chromatography failed. The lability of the adducts was ex-
plained in terms of their increased ability to undergo a
retro-aldol reaction, probably due to the crowdedness
around the quaternary C-2 atom. In this contribution we
wish to demonstrate that these valuable but not isolable tet-
rafunctionalized synthons 6 can be simply transformed into
the corresponding stable 3-azido-4-oxoalk-2-enoates
7
which can then be converted into the hitherto unknown 2-
alkyl-3-aroyl-2H-azirine-2-carboxylates 9 (see Scheme 3).
Results and Discussion
The reaction of 2-azido-4Ј-methoxyacetophenone (5b)
and ethyl pyruvate resulted in the formation of adduct 6b
as a mixture of syn and anti diastereomers in a ratio of
67:33. The low diastereoselectivity seems to be typical in
the coupling of α-azido ketones with carbon electro-
philes[14–17] and can be interpreted in terms of thermo-
dynamic control during the formation of the adducts. The
Figure 2. Crystal packing of anti-6b, view normal to (010).
We also demonstrated previously that treatment of a
diastereomers of ethyl 3-azido-2-hydroxy-4-(4-methoxy- mixture syn/anti-6b with mesyl chloride (MsCl) in pyridine
phenyl)-2-methyl-4-oxobutanoate (6b) were separated by resulted in the formation of the corresponding stable ethyl
column chromatography, and single-crystal X-ray analysis 3-azido-4-(4-methoxyphenyl)-2-methyl-4-oxo-2-butenoate
of the minor product revealed its anti relative configuration (7b) in diastereopure form and in moderate (50%) yield.[14c]
(Figure 1). Note that a strong hydrogen bond was observed When the reaction was repeated with pure diastereomers of
in the crystals of anti-6b; the crystal packing is shown in azido alcohol 6b (see Experimental Section), we found that
Figure 2. The observed preference for the formation of the both stereoisomers show similar reactivity and give the
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Synthesis of Substituted 2H-Azirine-2-carboxylates
same vinyl azide (E)-7b with complete diastereoselectivity 2-oxofurans 8a,e were obtained (Scheme 3). X-ray analysis
and in nearly the same yields (anti: 75% yield, 81% conver- of lactone 8e provided further support for the structure of
sion; syn: 63% yield, 75% conversion).
the products (Figure 3). Again, strong hydrogen bonds were
Since the stereochemical outcome of the elimination found between the hydroxy group and the carbonyl oxygen
from the in situ generated intermediates ethyl 3-azido-2- atom; the crystal packing is shown in Figure 4.
mesyloxy-4-(4-methoxyphenyl)-2-methyl-4-oxobutanoates
did not seem to depend on their relative configuration, we
decided to develop a direct methodology for the synthesis
of vinyl azides 7. Direct treatment of the crude mixture of
the coupling reaction of phenacyl azides 5a–f giving ad-
ducts 6a–f with mesyl chloride after removal of the solvent
and without isolation of the products 6 resulted in the for-
mation of diastereopure vinyl azides (E)-7a–f in good over-
all yields (36–51%, Scheme 2, Table 1). No marked substit-
uent effect was observed.
Scheme 3. Formation of lactones 8.
Figure 3. Crystal structure of lactone 8e.
Scheme 2. Synthesis of vinyl azides (E)-7.
The formation of lactones 8a,e can only be explained by
an internal attack by the carboxylate anions of β-aroyl-α,β-
unsaturated carboxylic acids having an (E) relative configu-
ration on the carbonyl unit: the appropriate β-aroyl-α,β-
unsaturated esters 7a,e should therefore also be (E) dia-
stereomers. This ring/chain tautomerism of β-aroyl-α,β-un-
saturated carboxylic acids is documented in the litera-
ture.[18]
Having the β-azido-α,β-unsaturated esters 7 in our
hands, we examined their thermolysis. After refluxing in
toluene for 1 h, the starting vinyl azides 7a–f were com-
pletely transformed, and 3-aroyl-2-ethoxycarbonyl-2H-azir-
ines 9a–f were isolated from the reaction mixtures in moder-
ate to good yields (33–70%, Scheme 4, Table 2). All the
azirines 9a–f are stable compounds and were identified by
Table 1. Results of the two-step synthesis of vinyl azides (E)-7.
Entry
Starting Product R1
material
R2 t[a] [h] Overall yield
[%]
1
2
3
5a
5b
5c
7a
7b
7c
H
OMe
F
H
H
H
5.5/40
27/47
6.5/
44
43
44
40.5
24/91
26.5/
90
4
5
5d
5e
7d
7e
Cl
Ph
H
H
36
49
6
5f
7f
H
OMe 5/41
51
[a] Reaction time for the C–C coupling (Step 1)/reaction time for
the formation of the vinyl azide (Step 2).
Determination of the relative configuration of the pre- their spectral characteristics. In the IR spectra, 2H-azirines
pared vinyl azides 7 was quite troublesome due to the lack 9 showed a strong C=N stretch in the region of 1739–
3
of JH,H coupling constants in the vinyl azide unit. The β- 1742 cm–1. Further diagnostic tools were the chemical shifts
azido-α,β-unsaturated esters 7 were isolated as oils which of the signals of the carbon atoms C-2 (δ = 38.6–39.0 ppm)
prevented us from using X-ray crystallography. To obtain and C-3 (δ = 164.4–166.0) in their 13C NMR spectra.[19]
crystallizable solids, azides 7a,e were treated with sodium
The synthesis of 2H-azirines by the thermal or photo-
hydroxide in dioxane/water solution. Structure elucidation chemical treatment of vinyl azides is well documented.[19,20]
of the products isolated in moderate yields (50–59%) re- However, the formation of 2H-azirines by thermolysis de-
vealed that no carboxylic acids but 2,5-dihydro-5-hydroxy- pends largely on the structure of the vinyl azide.[21] When a
Eur. J. Org. Chem. 2008, 1441–1448
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T. Patonay, J. Jeko, É. Juhász-Tóth
˝
FULL PAPER
Figure 4. Crystal packing for lactone 8e.
carbonyl group is present in the vinyl azide, isoxazoles, ox-
azoles or nitriles may be formed from the nitrene intermedi-
ate. In the presence of a β-aryl group, ring-closure leading
to indoles may also take place. The structure of the formed
product also depends on the relative configuration of the
acyl and the azido groups in the vinyl azide.[1a–1d,2–4,11a,21,22]
The thermolysis of 2-azidoalk-2-en-1-ones usually gives 2-
cyanoalkan-1-ones by rearrangement of the nitrene inter-
mediate; however, the formation of 3-acyl-2H-azirines in
low yields has also been reported in some cases.[4,21,23]
Changing the 3-aryl group to an alkyl unit tends to increase
the stability of the azirine.[23]
Our substrates 7 can be considered as either 2-azidoalk-
2-en-1-ones or 3-azidoalk-2-enoates, but their (E) stereo-
chemistry prevents the nitrene from attacking the electron-
rich carbonyl oxygen atom of the ester function. Thus, the
formation of an isoxazolone-type product is excluded.
From the alternative routes a and b (Scheme 4), the mi-
gration of the π-electrons of the double bond to the elec-
tron-deficient nitrene (route a) takes place instead of indol-
one formation (route b) which would require temporary
dearomatization. Since the similar 2,3-diacetyl-2H-azirine
was found to be unstable and gave 2-acetyl-5-methyloxazole
on irradiation,[3] the observed stability of our 2H-azirines
9a–f can be explained by the presence of the quaternary C-
2 atom and/or by the stabilizing effect of the methyl and
carboxylate groups. To the best of our knowledge, this is
the first general synthesis of 3-acyl-2H-azirine-2-carboxylic
Scheme 4. Synthesis of 2H-azirines 9.
Table 2. Synthesis of 2H-azirines 9 by the thermolysis of vinyl az-
ides 7.
Entry Starting material Product
R1
R2
Yield [%]
1
2
3
4
5
6
7a
7b
7c
7d
7e
7f
9a
9b
9c
9d
9e
9f
H
OMe
F
Cl
Ph
H
H
H
H
H
H
68
70
49
33
54
70
OMe
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Synthesis of Substituted 2H-Azirine-2-carboxylates
0 °C. After 43 h, the reaction mixture was concentrated in vacuo,
and the residue was purified by column chromatography (eluent:
toluene/ethyl acetate = 9:1, v/v) to give pure 6b (982 mg, conver-
sion: 88%, yield: 69%, normalized to 100% conversion) as a
colourless oil which was a 67:33 mixture of the syn/anti dia-
stereomers (based on 1H NMR). Repeated column chromatog-
raphy (eluent: toluene/ethyl acetate = 9:1, v/v) of the diastereomeric
mixture resulted in pure isomers.
acid derivatives. Up to now, only one compound, namely,
methyl 3-benzoyl-2-chloro-2H-azirine-2-carboxylate had
been synthesized in an independent way.[24]
Conclusions
We have presented a further example to demonstrate the
synthetic usefulness of our previously developed methodol-
ogy based on the trapping of carbanions generated in situ
from the reaction of α-azido ketones with carbon electro-
philes. It has been pointed out that the reaction of phenacyl
azides with an α-oxo carboxylate, ethyl pyruvate, resulted in
the formation of 4-aryl-3-azido-2-hydroxy-4-oxobutanoates
that are somewhat unstable due to their ability to undergo
an easy retro-aldol cleavage. A convenient method has been
developed for the conversion of these intermediates into
ethyl 4-aryl-3-azido-2-methyl-4-oxobut-2-enoates. Thermol-
ysis of these unique vinyl azides led to the rare 3-aroyl-2H-
azirine-2-carboxylic acid esters. The relative configurations
of the aldol-type adduct and the vinyl azide have been de-
termined by X-ray analysis.
syn-6b: Colourless oil. IR (neat): ν = 3500 (OH), 2100 (N ), 1746,
˜
3
1732, 1682, 1674, 1600, 1312, 1266, 1224, 1174, 1020 cm–1. 1H
NMR (200 MHz, CDCl3, 25 °C): δ = 1.13 (t, 3J = 7.2 Hz, 3 H,
3
OCH2CH3), 1.57 (s, 3 H, 2-Me), 3.86 (s, 3 H, 4Ј-OMe), 4.09 (q, J
= 7.2 Hz, 2 H, OCH2CH3), 4.55 (s, 1 H, 3-H), 6.95 (d, 3J = 9.1 Hz,
2 H, 3Ј,5Ј-H), 7.97 (d, J = 9.1 Hz, 2 H, 2Ј,6Ј-H) ppm. 13C NMR
3
(50 MHz, CDCl3, 25 °C): δ = 13.6 (OCH2CH3), 23.0 (2-Me), 55.3
(4Ј-OMe), 61.6 (OCH2CH3), 64.5 (C-3), 77.0 (C-2), 113.8 (C-3Ј,5Ј),
127.2 (C-1Ј), 131.4 (C-2Ј,6Ј), 164.4 (C-4Ј), 173.8 (C-1) 194.3 (C-4)
ppm. C14H17N3O5 (307.3): calcd. C 54.72, H 5.58, N 13.67; found
C 54.59, H 5.56, N 13.72.
anti-6b: White prisms, m.p. 87–90 °C. IR: ν = 3470 (OH), 2101
˜
(N3), 1723, 1672, 1600, 1264, 1180 cm–1. 1H NMR (200 MHz,
3
CDCl3, 25 °C): δ = 1.35 (t, J = 7.2 Hz, 3 H, OCH2CH3), 1.48 (s,
3
3 H, 2-Me), 3.88 (s, 3 H, 4Ј-OMe), 4.33 (dq, J = 7.2, 2.2 Hz, 2 H,
3
4
OCH2CH3), 4.67 (s, 1 H, 3-H), 6.96 (dd, J = 9.2, J = 2.1 Hz, 2
H, 3Ј,5Ј-H), 7.99 (dd, 3J = 9.2, 4J = 2.1 Hz, 2 H, 2Ј,6Ј-H) ppm. 13
C
Experimental Section
NMR (50 MHz, CDCl3, 25 °C): δ = 13.9 (OCH2CH3), 24.0 (2-Me),
55.5 (4Ј-OMe), 61.9 (OCH2CH3), 66.2 (C-3), 76.2 (C-2), 114.1 (C-
3Ј,5Ј), 128.6 (C-1Ј), 131.6 (C-2Ј,6Ј), 164.5 (C-4Ј), 174.3 (C-1) 192.7
(C-4) ppm. C14H17N3O5 (307.3): calcd. C 54.72, H 5.58, N 13.67;
found C 54.51, H 5.56, N 13.64.
General: All chemicals were used as purchased unless otherwise
stated. THF was distilled from benzophenone ketyl. α-Azido
ketones 5 were prepared according to the procedure reported pre-
viously.[14b] Column chromatography was performed on Kieselgel
60. Melting points: Boetius hot-stage apparatus, uncorrected val-
ues. IR: Perkin-Elmer 16 PC-FT-IR spectrometer; KBr pellets un-
less otherwise stated. NMR: Varian Gemini 200, Bruker WP 200
SY, Bruker AM 360, Bruker AM 400 spectrometers (200, 360 or
400 MHz for 1H; 50, 90 or 100 MHz for 13C). Spectra were re-
corded in CDCl3 solution, unless otherwise stated. Chemical shifts
are given in δ relative to an internal standard TMS (δ = 0 ppm) or
to the residual CHCl3 (δ = 7.26 ppm for 1H NMR and δ =
77.0 ppm for 13C NMR). Elemental analysis: Carlo Erba. X-ray
quality crystals of anti-6b or 8e were mounted onto a glass fibre
by using epoxy resin. Data were collected at 293(1) K with an En-
raf–Nonius MACH3 diffractometer using monochromated Mo-Kα
radiation (λ = 0.71073 Å), ω-motion. Absorption correction was
made using ψ-scans. The structure was solved by direct methods
using the SIR-92 software[25] and refined on F2 by full-matrix least-
squares methods using the SHELX-97 program.[26] All non-hydro-
gen atoms were refined anisotropically. Hydrogen atoms were in-
cluded at geometric positions using a riding model except for hy-
droxy protons which could be found on the difference electron-
density map, and their distance to the oxygen atom was con-
strained. Strong hydrogen bonds were observed between the hy-
droxy group and the carbonyl oxygen atom in both cases. Material
for publication was prepared with the WINGX-97 suite of pro-
grams.[27] CCDC-664649 (anti-6b) and -664650 (8e) contain the
supplementary crystallography data for this paper. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.au.uk/data_request/cif.
X-ray Crystallographic Data for anti-6b: Formula C14H17N3O5, M
¯
= 307.31, triclinic, space group P1, a = 7.915(2), b = 8.080(2), c =
12.595(2) Å, α = 81.76(2), β = 79.306(10), γ = 81.39(2)°, V =
777.1(3) Å3, Z = 2, ρcalcd. = 1.313, 2857 measured reflections of
which 2051 were unique with IϾ2σ(I), decay 4%, R1 = 0.057 and
wR2 = 0.167 for 2857 reflections and 203 parameters, GOF = 1.03.
Residual electron density: 0.29/–0.22 e/Å3. The configurations at
C2 and C3 are (R,R) and its enantiomer pair (S,S). Hydrogen-bond
geometries are shown in Table 3.
Table 3. Hydrogen-bond geometries in the crystals of anti-6b.
D–H···A
D–H [Å] H···A [Å] D···A [Å] D–H···A [°]
O3–H1O···O1
0.79(3)
0.79(3)
2.34(3)
2.12(3)
2.693(2)
2.862(3)
108(3)
157(3)
O3–H1O···O1[a]
[a] Symmetry codes: –x + 2, –y + 2, –z.
Ethyl 3-Azido-4-(4-methoxyphenyl)-2-methyl-4-oxobut-2-enoate (7b):
solution of azido alcohol 6b (syn/anti 67:33, 203 mg,
A
=
0.66 mmol) in dry pyridine (5 mL) was cooled to –15 °C, and mesyl
chloride (0.10 mL, 1.32 mmol) was added in one portion. The mix-
ture was warmed to room temperature and stirred for 25 h. Then
it was poured into water and extracted with CH2Cl2 (3ϫ30 mL).
The combined organic layers were washed with saturated NaHCO3
solution (25 mL) and water, dried (MgSO4), concentrated in vacuo
and purified by column chromatography (eluent: hexane/ethyl ace-
tate = 3:1, v/v) to give pure (E)-7b (66 mg, conversion: 69%, yield:
Ethyl 3-Azido-2-hydroxy-4-(4-methoxyphenyl)-2-methyl-4-oxobut-
anoate (6b): A solution of 2-azido-4Ј-methoxyacetophenone (5b)
(1.00 g, 5.25 mmol) in dry THF (50 mL) was cooled to 0 °C. Ethyl
50%, normalized to 100% conversion) as a yellow oil. IR (neat): ν
˜
= 2108 (N3), 1712 (ester), 1662 (C=O), 1598, 1290, 1264, 1244,
1172, 844 cm–1. 1H NMR (360 MHz, CDCl3, 25 °C): δ = 0.98 (t,
2-oxopropionate (1.73 mL, 15.75 mmol) and DBU (84 µL, 3J = 7.0 Hz, 3 H, OCH2CH3), 1.99 (s, 3 H, 2-Me), 3.89 (s, 3 H, 4Ј-
0.56 mmol) were added, and the mixture was allowed to stand at
OMe), 3.94 (q, 3J = 7.0 Hz, 2 H, OCH2CH3), 6.98 (d, 3J = 9.4 Hz,
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2 H, 3Ј,5Ј-H), 7.92 (d, J = 9.4 Hz, 2 H, 2Ј,6Ј-H) ppm. 13C NMR toluene). Yellow oil. IR (neat): ν = 2110 (N ), 1714 (ester), 1674
3
˜
3
(50 MHz, CDCl3, 25 °C): δ = 12.6, 13.5 (2-Me, OCH2CH3), 55.5
(C=O), 1588, 1290, 1234 cm–1. 1H NMR (200 MHz, CDCl3,
3
(4Ј-OMe), 61.0 (OCH2CH3), 114.3 (C-3Ј,5Ј), 116.5 (C-3), 127.9 (C- 25 °C): δ = 1.01 (t, J = 7.0 Hz, 3 H, OCH2CH3), 1.99 (s, 3 H, 2-
3
3
1Ј), 131.3 (C-2Ј,6Ј), 144.6 (C-2), 164.4 (C-4Ј), 166.0 (C-1), 188.6 (C- Me), 3.95 (q, J = 7.0 Hz, 2 H, OCH2CH3), 7.48 (d, J = 8.6 Hz,
3
4) ppm. C14H15N3O4 (289.3): calcd. C 58.13, H 5.23, N 14.53;
found C 57.91, H 5.20, N 14.49. The above procedure was extended
to the pure diastereomers of the azido alcohol 6b. With anti-6b
(60 mg, 0.195 mmol), 35 mg (conversion: 81%, yield: 75%, normal-
ized to 100% conversion) of vinyl azide (E)-7b was obtained. Reac-
tion of syn-6b (60 mg) yielded the vinyl azide (E)-7b as a yellow oil
(conversion: 75%, yield: 63%, normalized to 100% conversion).
2 H, 3Ј,5Ј-H), 7.88 (d, J = 8.6 Hz, 2 H, 2Ј,6Ј-H) ppm. 13C NMR
(100 MHz, CDCl3, 25 °C): δ = 12.6, 13.6 (2-Me, OCH2CH3), 61.3
(OCH2CH3), 117.3 (C-3), 129.5 (C-3Ј,5Ј), 130.1 (C-2Ј,6Ј), 133.4 (C-
1Ј), 140.8 (C-4Ј) 143.9 (C-2), 165.9 (C-1), 188.9 (C-4) ppm.
C13H12ClN3O3 (293.7): calcd. C 53.16, H 4.12, N 14.31; found C
53.18, H 4.11, N 14.35.
Ethyl 3-Azido-4-(biphenyl-4-yl)-2-methyl-4-oxobut-2-enoate (7e):
From the α-azido ketone 5e (530 mg, 2.23 mmol), after the coup-
ling reaction (26.5 h) and the elimination (2ϫ0.35 mL of MsCl,
90 h), 365 mg (overall yield: 49%) of (E)-7e was obtained (eluent:
General Procedure for the Synthesis of Ethyl 4-Aryl-3-azido-2-
methyl-4-oxobut-2-enoates 7: A solution of α-azido ketone 5
(4.96 mmol) in dry THF (40 mL) was cooled to 0 °C. Ethyl 2-oxop-
ropionate (1.63 mL, 14.90 mmol) and DBU (81 µL, 0.55 mmol)
were added, and the mixture was allowed to stand at 0 °C. After
completion of the reaction, the mixture was concentrated in vacuo,
and the residue was dissolved in dry pyridine (20 mL). The solution
was cooled to –15 °C, and mesyl chloride (MsCl, 0.40 mL,
5.07 mmol) was added in one portion. The mixture was stirred at
room temperature and monitored by TLC. New batches of mesyl
chloride were added until completion of the reaction. Then it was
poured into water and extracted with CH2Cl2 (4ϫ50 mL), and the
organic layer was dried (MgSO4), concentrated in vacuo and puri-
fied by column chromatography.
toluene). Yellow oil. IR (neat): ν = 2110 (N ), 1712 (ester), 1668
˜
3
(C=O), 1602, 1288, 1238, 1178, 748 cm–1. 1H NMR (200 MHz,
3
CDCl3, 25 °C): δ = 1.00 (t, J = 7.2 Hz, 3 H, OCH2CH3), 2.02 (s,
3
3 H, 2-Me), 3.96 (q, J = 7.2 Hz, 2 H, OCH2CH3), 7.41–7.53 (m,
3 H, 3ЈЈ,4ЈЈ,5ЈЈ-H), 7.61–7.66 (m, 2 H, 2ЈЈ,6ЈЈ-H), 7.73 (d, 3J =
8.3 Hz, 2 H, 3Ј,5Ј-H), 8.02 (d, J = 8.3 Hz, 2 H, 2Ј,6Ј-H) ppm. 13C
3
NMR (100 MHz, CDCl3, 25 °C): δ = 12.6, 13.5 (2-Me, OCH2CH3),
61.1 (OCH2CH3), 116.9 (C-3), 127.2, 127.6, 128.4, 128.9, 129.3 (Ph,
C-2Ј,3Ј,5Ј,6Ј), 133.6 (C-1Ј), 139.4 (C-4Ј) 144.3 (C-2), 146.8 (C-1ЈЈ),
165.9 (C-1), 189.6 (C-4) ppm. C19H17N3O3 (335.3): calcd. C 68.05,
H 5.11, N 12.53; found C 68.06, H 5.10, N 12.56.
Ethyl 3-Azido-4-(3-methoxyphenyl)-2-methyl-4-oxobut-2-enoate (7f):
From the α-azido ketone 5f (427 mg, 2.23 mmol), after the coupling
reaction (5 h) and the elimination (3ϫ0.35 mL of MsCl, 41 h),
328 mg (overall yield: 51%) of (E)-7f was obtained (eluent: toluene/
Ethyl 3-Azido-2-methyl-4-oxo-4-phenylbut-2-enoate (7a): From the
α-azido ketone 5a (800 mg, 4.96 mmol), after the coupling reaction
(5.5 h) and the elimination (2ϫ0.40 mL of MsCl, 40 h), 289 mg
(overall yield: 44%) of (E)-7a was obtained (eluent: toluene/ethyl
ethyl acetate = 10:1, v/v). Brownish oil. IR (neat): ν = 2110 (N ),
˜
3
acetate = 10:1, v/v). Yellow oil. IR (neat): ν = 2112 (N ), 1716
˜
3
1714 (ester), 1674 (C=O), 1596, 1486, 1290, 1262 cm–1. H NMR
1
(ester), 1674 (C=O), 1596, 1450, 1288, 1234, 1184, 892 cm–1. 1H
NMR (200 MHz, CDCl3, 25 °C): δ = 0.94 (t, 3J = 7.4 Hz, 3 H,
OCH2CH3), 2.00 (s, 3 H, 2-Me), 3.90 (q, 3J = 7.4 Hz, 2 H,
OCH2CH3), 7.45–7.59 (m, 2 H, 3Ј,5Ј-H), 7.64 (m, 1 H, 4Ј-H), 7.93
(dd, 3J = 6.9, 4J = 1.8 Hz, 2 H, 2Ј,6Ј-H) ppm. 13C NMR (50 MHz,
CDCl3, 25 °C): δ = 12.6, 13.5 (2-Me, OCH2CH3), 61.1 (OCH2CH3),
117.1 (C-3), 128.8, 129.0 (C-2Ј,3Ј,5Ј,6Ј), 134.2 (C-4Ј), 135.0 (C-1Ј),
144.3 (C-2), 166.0 (C-1), 190.1 (C-4) ppm. C13H13N3O3 (259.3):
calcd. C 60.23, H 5.05, N 16.21; found C 60.20, H 5.04, N 16.22.
(200 MHz, CDCl3, 25 °C): δ = 1.00 (t, 3J = 7.1 Hz, 3 H,
OCH2CH3), 2.02 (s, 3 H, 2-Me), 3.87 (s, 3 H, 3Ј-OMe), 3.94 (q, J
3
= 7.1 Hz, 2 H, OCH2CH3), 7.17 (m, 1 H, 4Ј-H), 7.36–7.52 (m, 3
H, 2Ј,5Ј,6Ј-H) ppm. 13C NMR (90 MHz, CDCl3, 25 °C): δ = 12.5,
13.5 (2-Me, OCH2CH3), 55.4 (3Ј-OMe), 61.1 (OCH2CH3), 112.3
(C-2Ј), 117.0 (C-3), 120.8 (C-4Ј), 121.6 (C-6Ј), 130.0 (C-5Ј), 136.2
(C-1Ј), 144.2 (C-2), 160.1 (C-3Ј), 165.9 (C-1), 189.8 (C-4) ppm.
C14H15N3O4 (289.3): calcd. C 58.13, H 5.23, N 14.53; found C
57.91, H 5.20, N 14.49.
Ethyl 3-Azido-4-(4-methoxyphenyl)-2-methyl-4-oxobut-2-enoate (7b):
From the α-azido ketone 5b (427 mg, 2.23 mmol), after the
coupling reaction (27 h) and the elimination (3ϫ0.35 mL of MsCl,
47 h), 279 mg (overall yield: 43%) of (E)-7b was obtained (eluent:
hexane/ethyl acetate = 3:1, v/v).
4-Azido-5-hydroxy-3-methyl-2-oxo-5-phenyl-2,5-dihydrofuran (8a):
An 8% sodium hydroxide solution (0.43 mL, 0.89 mmol) was
added to
a stirred solution of vinyl azide (E)-7a (231 mg,
0.89 mmol) in a mixture of dioxane (13 mL) and water (6.5 mL) at
room temperature. Two further batches of sodium hydroxide solu-
tion (0.41 mmol) were added to the reaction mixture after 2 and
21 h. When the reaction was complete (25 h) the reaction mixture
was acidified with 10% hydrochloric acid and diluted with water
(50 mL). Then it was extracted with CH2Cl2 (3ϫ30 mL), dried
(Na2SO4) and concentrated in vacuo. The residue was purified as
follows: it was dissolved in a mixture of water (21 mL) and 8%
sodium hydroxide solution (2.0 mL), and the alkaline phase was
extracted with CH2Cl2 (2ϫ20 mL). The basic solution was acidi-
fied with 10% hydrochloric acid. White crystals precipitated and
were filtered off to give pure 8a (104 mg, yield: 50%). M.p. 95–
Ethyl 3-Azido-4-(4-fluorophenyl)-2-methyl-4-oxobut-2-enoate (7c):
From the α-azido ketone 5c (400 mg, 2.23 mmol), after the coup-
ling reaction (6.5 h) and the elimination (3ϫ0.35 mL of MsCl,
40.5 h), 274 mg (overall yield: 44%) of (E)-7c was obtained (eluent:
toluene). Yellow oil. IR (neat): ν = 2112 (N ), 1714 (ester), 1674
˜
3
(C=O), 1598, 1288, 1236, 1154 cm–1. H NMR (360 MHz, CDCl3,
1
3
25 °C): δ = 1.00 (t, J = 7.2 Hz, 3 H, OCH2CH3), 1.99 (s, 3 H, 2-
Me), 3.95 (q, 3J = 7.2 Hz, 2 H, OCH2CH3), 7.16–7.20 (m, 2 H,
3Ј,5Ј-H), 7.95–7.99 (m, 2 H, 2Ј,6Ј-H) ppm. 13C NMR (50 MHz,
CDCl3, 25 °C): δ = 12.6, 13.6 (2-Me, OCH2CH3), 61.2 (OCH2CH3),
116.3 (d, JC,F = 22.2 Hz, C-3Ј,5Ј), 116.9 (C-3), 131.6 (d, JC,F
=
105 °C. IR: ν = 3298 (OH), 2124 (N ), 1730 (C=O), 1662,
˜
3
1336 cm–1. H NMR (360 MHz, [D6]DMSO, 25 °C): δ = 1.76 (s, 3
1
9.8 Hz, C-2Ј,6Ј), 144.1 (C-1Ј,2), 166.4 (d, JC,F = 255 Hz, C-4Ј),
166.0 (C-1), 188.6 (C-4) ppm. C13H12FN3O3 (277.3): calcd. C
56.32, H 4.36, N 15.16; found C 56.28, H 4.38, N 15.15.
H, 2-Me), 7.47–7.51 (m, 5 H, Ph), 8.87 (br. s, 1 H, 5-OH) ppm.
13C NMR (90 MHz, [D6]DMSO, 25 °C): δ = 7.3 (2-Me), 102.0 (C-
5), 110.5 (C-3), 125.9 (C-2Ј,6Ј), 128.9 (C-3Ј,5Ј), 130.0 (C-4Ј), 135.8
(C-1Ј), 155.0 (C-4), 169.9 (C-2) ppm.
Ethyl 3-Azido-4-(4-chlorophenyl)-2-methyl-4-oxobut-2-enoate (7d):
From the α-azido ketone 5d (437 mg, 2.23 mmol), after the coup-
ling reaction (24 h) and the elimination (2ϫ0.35 mL of MsCl,
91 h), 238 mg (overall yield: 36%) of (E)-7d was obtained (eluent:
4-Azido-5-(biphenyl-4-yl)-5-hydroxy-3-methyl-2-oxo-2,5-dihydrofu-
ran (8e): An 8% sodium hydroxide solution (0.43 mL, 0.89 mmol)
1446
www.eurjoc.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 1441–1448

Synthesis of Substituted 2H-Azirine-2-carboxylates
was added to a stirred solution of vinyl azide (E)-7e (300 mg,
0.89 mmol) in a mixture of dioxane (13 mL) and water (6.5 mL) at
room temperature. Another batch of sodium hydroxide solution
(0.89 mmol) was added to the reaction mixture after 2 h. When the
reaction was complete (4 h), the mixture was acidified with 10%
hydrochloric acid and diluted with water (50 mL). Then it was ex-
tracted with CH2Cl2 (3ϫ30 mL), dried (Na2SO4) and concentrated
in vacuo. The residue was purified by column chromatography (elu-
ent: hexane/ethyl acetate = 2:1, v/v) to give pure 8e (162 mg, yield:
59%) as a yellow crystalline solid. M.p. 214 °C (recrystallization at
C13H13NO3 (231.3): calcd. C 67.52, H 5.67, N 6.06; found C 66.95,
H 5.49, N 6.14.
2-(Ethoxycarbonyl)-3-(4-methoxybenzoyl)-2-methyl-2H-azirine (9b):
From the vinyl azide (E)-7b (200 mg, 0.69 mmol), 127 mg (70%) of
9b was obtained. Yellow oil. IR (neat): ν = 1740 (C=N), 1717 (es-
˜
ter), 1650 (C=O), 1600, 1511, 1269, 1171, 668 cm–1. 1H NMR
(200 MHz, CDCl3, 25 °C): δ = 1.24 (t, 3J = 7.2 Hz, 3 H,
3
OCH2CH3), 1.67 (s, 3 H, 2-Me), 3.92 (s, 3 H, 4Ј-OMe), 4.18 (q, J
= 7.2 Hz, 2 H, OCH2CH3), 7.04 (d, 3J = 8.8 Hz, 2 H, 3Ј,5Ј-H), 8.26
(d, 3J = 8.8 Hz, 2 H, 2Ј,6Ј-H) ppm. 13C NMR (90 MHz, CDCl3,
25 °C): δ = 13.9 (OCH2CH3), 17.6 (2-Me), 38.6 (C-2), 55.6 (OCH3),
61.7 (OCH2CH3), 114.7 (C-3Ј,5Ј), 127.7 (C-1Ј), 132.5 (C-2Ј,6Ј),
164.6 (C-4Ј), 166.0 (C-3), 171.8 (CO2Et), 180.1 (C=O) ppm. MS
(EI, 70 eV): m/z (%) = 188 (5.4) [M – CO2Et]+·, 135 (100)
[ArCO]+, 107 (4.8) [Ar]+, 92 (12) [Ar – Me]+, 77 (17) [Ph]+, 64 (7.3).
C14H15NO4 (261.3): calcd. C 64.36, H 5.79, N 5.36; found C 64.25,
H 5.73, N 5.32.
ca. 120 °C). IR: ν = 3278 (OH), 2118 (N ), 1738 (C=O), 1662,
˜
3
1336 cm–1. H NMR (360 MHz, [D6]DMSO, 25 °C): δ = 1.79 (s, 3
1
H, 2-Me), 7.40 (m, 1 H, 4ЈЈ-H), 7.47–7.51 (m, 2 H, 3ЈЈ,5ЈЈ-H), 7.60
(d, 3J = 8.4 Hz, 2 H, 2Ј,6Ј-H), 7.71 (d, 3J = 7.6 Hz, 2 H, 2ЈЈ,6ЈЈ-
H), 7.78 (d, 3J = 8.4 Hz, 2 H, 3Ј,5Ј-H), 8.93 (br. s, 1 H, 5-OH) ppm.
13C NMR (90 MHz, [D6]DMSO, 25 °C): δ = 7.2 (2-Me), 101.9 (C-
5), 110.6 (C-3), 126.5, 126.8, 127.1, 127.9, 129.0 (C-2Ј,6Ј, C-3Ј,5Ј,
C-2ЈЈ,6ЈЈ, C-3ЈЈ,5ЈЈ, C-4ЈЈ), 134.8 (C-4Ј), 139.2 (C-1ЈЈ), 141.6 (C-1Ј),
155.0 (C-4), 169.8 (C-2) ppm.
2-(Ethoxycarbonyl)-3-(4-fluorobenzoyl)-2-methyl-2H-azirine
(9c):
X-ray Crystallographic Data for 8e: Formula C17H13N3O3, M = From the vinyl azide (E)-7c (200 mg, 0.72 mmol), 88 mg (49%) of
307.3, monoclinic, space group P21, a = 14.140(2), b = 7.351(2), c
9c was obtained. Yellow oil. IR (neat): ν˜ = 1743 (C=N), 1717 (es-
ter), 1674 (C=O), 1599, 1507, 1241, 1158, 851 cm–1. 1H NMR
(200 MHz, CDCl3, 25 °C): δ = 1.26 (t, 3J = 7.2 Hz, 3 H,
OCH2CH3), 1.68 (s, 3 H, 2-Me), 4.20 (q, 3J = 7.2 Hz, 2 H,
OCH2CH3), 7.23–7.31 (m, 2 H, 3Ј,5Ј-H), 8.31–8.38 (m, 2 H, 2Ј,6Ј-
H) ppm. 13C NMR (90 MHz, CDCl3, 25 °C): δ = 13.9 (OCH2CH3),
17.5 (2-Me), 38.9 (C-2), 61.9 (OCH2CH3), 116.8 (d, JC,F = 22.1 Hz,
C-3Ј,5Ј), 131.0 (C-1Ј), 132.9 (d, JC,F = 10.0 Hz C-2Ј,6Ј), 164.8 (C-
3), 167.7 (d, JC,F = 259 Hz, C-4Ј), 171.5 (CO2Et), 180.5 (C=O)
ppm. MS (EI, 70 eV): m/z (%) = 176 (2.8) [M – CO2Et]+·, 123 (100)
[ArCO]+, 95 (35) [Ar]+, 75 (9.3). C13H12FNO3 (249.2): calcd. C
62.65, H 4.85, N 5.62; found C 62.58, H 4.85, N 5.63.
= 15.864(2) Å, β = 108.117(10)°, V = 1567.1(5) Å3, Z = 4, ρcalcd.
=
1.302, 3295 measured reflections of which 1312 were unique with
IϾ2σ(I), decay 8%, R1 = 0.078 and wR2 = 0.184 for 3295 reflec-
tions and 423 parameters, GOF = 0.96. Residual electron density:
0.18/–0.18 e/Å3. The structure shows pseudosymmetry. However,
when the structure was solved in the centrosymmetric space group
P21/c there was a disorder of the phenyl rings with an occupancy
of 50:50 and with a significantly higher R factor. In a non-centro-
symmetric space group this was perfectly solved. For this reason
P21 was chosen as the symmetry group. The angle between the
mean-square planes of the C11–C16 and C21–C26 rings and that
of the pseudosymmetric related rings C51–C56 and C61–C66 were
33 and 20°, respectively. The crystal was a rather weakly diffracting
one, and the absolute configuration could not be assigned. Hydro-
gen-bond geometries are shown in Table 4.
3-(4-Chlorobenzoyl)-2-(ethoxycarbonyl)-2-methyl-2H-azirine (9d):
From the vinyl azide (E)-7d (150 mg, 0.51 mmol), 45 mg (33%) of
9d was obtained. Yellow oil. IR (neat): ν = 1739 (C=N), 1723 (es-
˜
ter), 1673 (C=O), 1588, 1403, 1280, 1135, 1014, 748 cm–1. 1H NMR
(200 MHz, CDCl3, 25 °C): δ = 1.25 (t, 3J = 7.1 Hz, 3 H,
OCH2CH3), 1.67 (s, 3 H, 2-Me), 4.19 (q, 3J = 7.1 Hz, 2 H,
OCH2CH3), 7.56 (d, 3J = 8.9 Hz, 2 H, 3Ј,5Ј-H), 8.24 (d, 3J =
8.9 Hz, 2 H, 2Ј,6Ј-H) ppm. 13C NMR (90 MHz, CDCl3, 25 °C): δ
= 13.9 (OCH2CH3), 17.5 (2-Me), 39.0 (C-2), 62.0 (OCH2CH3),
129.9 (C-3Ј,5Ј), 131.3 (C-2Ј,6Ј), 132.8 (C-1Ј), 142.9 (C-4Ј), 164.8 (C-
3), 171.4 (CO2Et), 180.9 (C=O) ppm. MS (EI, 70 eV): m/z (%) =
192 (2.4) [M – CO2Et]+·, 139 (100) [ArCO]+, 111 (27) [Ar]+, 75 (19)
[Ar – HCl]+, 50 (6.9). C13H12ClNO3 (265.7): calcd. C 58.77, H 4.55,
N 5.27; found C 58.63, H 4.58, N 5.30.
Table 4. Hydrogen bond geometry in the crystals of 8e.
D–H···A
D–H [Å] H···A [Å] D···A [Å] D–H···A [°]
O5–H5···O2[a]
0.86(2)
1.99(6)
2.12(3)
2.726(9)
2.862(3)
142(8)
157(3)
O45–H45···O42[b] 0.79(3)
[a] Symmetry codes: –x + 2, –y + ½, –z + 2. [b] Symmetry codes:
–x, y – ½, –z + 1.
General Procedure for the Synthesis of 3-Acyl-2-(ethoxycarbonyl)-2-
methyl-2H-azirines 9: A solution of ethyl 4-aryl-3-azido-2-methyl-
4-oxobut-2-enoate (E)-7 (0.70 mmol) in toluene (10 mL) was re-
fluxed for 1 h. The solvent was evaporated under reduced pressure,
and the residue was purified by column chromatography (eluent:
hexane/acetone = 5:1, v/v).
2-(Ethoxycarbonyl)-2-methyl-3-(4-phenylbenzoyl)-2H-azirine (9e):
From the vinyl azide (E)-7e (224 mg, 0.67 mmol), 110 mg (54%) of
9e were obtained. Yellow oil. IR (neat): ν = 1739 (C=N), 1722
˜
(ester), 1669 (C=O), 1602, 1449, 1280, 1134, 743 cm–1. 1H NMR
3-Benzoyl-2-(ethoxycarbonyl)-2-methyl-2H-azirine (9a): From the (200 MHz, CDCl3, 25 °C): δ = 1.26 (t, 3J = 7.1 Hz, 3 H,
vinyl azide (E)-7a (300 mg, 1.16 mmol), 182 mg (68%) of 9a was
OCH2CH3), 1.70 (s, 3 H, 2-Me), 4.20 (q, 3J = 7.1 Hz, 2 H,
OCH2CH3), 7.42–7.53 (m, 3 H, 3ЈЈ,4ЈЈ,5ЈЈ-H), 7.63–7.67 (m, 2 H,
obtained. Yellow liquid. IR (neat): ν = 1742 (C=N), 1722 (ester),
˜
1668 (C=O), 1276, 1132, 706 cm–1. 1H NMR (360 MHz, CDCl3, 2ЈЈ,6ЈЈ-H), 7.79 (d, 3J = 8.5 Hz, 2 H, 3Ј,5Ј-H), 8.35 (d, 3J = 8.5 Hz,
3
25 °C): δ = 1.25 (t, J = 7.2 Hz, 3 H, OCH2CH3), 1.68 (s, 3 H, 2-
2 H, 2Ј,6Ј-H) ppm. 13C NMR (90 MHz, CDCl3, 25 °C): δ = 13.9
Me) 4.19 (q, 3J = 7.2 Hz, 2 H, OCH2CH3), 7.56–7.60 (m, 2 H, (OCH2CH3), 17.6 (2-Me), 38.8 (C-2), 61.9 (OCH2CH3), 127.4 (C-
3Ј,5Ј-H), 7.72–7.75 (m, 1 H, 4Ј-H), 8.28 (d, 3J = 8.1 Hz, 2 H, 2Ј,6Ј- 4ЈЈ), 127.5, 128.0, 129.0, 129.2, 130.5 (C-2Ј,6Ј, C-3Ј,5Ј, C-2ЈЈ,6ЈЈ, C-
H) ppm. 13C NMR (90 MHz, CDCl3, 25 °C):
(OCH2CH3), 17.7 (2-Me), 38.9 (C-2), 61.8 (OCH2CH3), 129.2,
δ
=
14.01
3ЈЈ,5ЈЈ), 133.2 (C-1Ј), 139.4 (C-1ЈЈ), 148.7 (C-4Ј), 164.8 (C-3), 171.6
(CO2Et), 181.5 (C=O) ppm. MS (EI, 70 eV): m/z (%) = 207 (4)
129.7 (C-2Ј,3Ј,5Ј,6Ј), 134.2 (C-1Ј), 135.6 (C-4Ј), 164.4 (C-3), 171.2 [ArCOCN]+, 196 (42), 181 (100) [ArCO]+, 152 (63), 129 (40), 101
(CO2Et), 181.7 (C=O) ppm. MS (EI, 70 eV): m/z (%) = 158 (2.4) (21), 73 (52), 57 (47), 43 (98). C19H17NO3 (307.3): calcd. C 74.25,
[M – CO2Et]+·, 105 (100) [PhCO]+, 77 (47) [Ph]+, 51 (17).
H 5.58, N 4.56; found C 74.11, H 5.57, N 4.57.
Eur. J. Org. Chem. 2008, 1441–1448
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1447

T. Patonay, J. Jeko, É. Juhász-Tóth
˝
FULL PAPER
[10] a) F. W. Fowler, A. Hassner, L. A. Levy, J. Am. Chem. Soc.
1967, 89, 2077–2082; b) G. L’abbé, A. Hassner, J. Org. Chem.
1971, 36, 258–260.
2-(Ethoxycarbonyl)-3-(3-methoxybenzoyl)-2-methyl-2H-azirine (9f):
From the vinyl azide (E)-7f (203 mg, 0.70 mmol), 127 mg (70%) of
9f was obtained. Yellow oil. IR (neat): ν = 1741 (C=N), 1722 (es-
˜
[11] a) A. Hassner, G. L’abbé, M. J. Miller, J. Am. Chem. Soc. 1971,
93, 981–985; b) V. A. Reznikov, G. I. Roschupkina, T. V. Ryba-
lova, Yu. V. Gatilov, Russ. Chem. Bull. 2001, 50, 874–881; c)
G. I. Roschupkina, Yu. V. Gatilov, T. V. Rybalova, V. A. Rezni-
kov, Eur. J. Org. Chem. 2004, 1765–1773.
ter), 1669 (C=O), 1597, 1487, 1268, 1134, 1035, 744 cm–1. 1H NMR
(200 MHz, CDCl3, 25 °C): δ = 1.26 (t, 3J = 7.1 Hz, 3 H,
3
OCH2CH3), 1.68 (s, 3 H, 2-Me), 3.90 (s, 3 H, 3Ј-OMe), 4.19 (q, J
= 7.1 Hz, 2 H, OCH2CH3), 7.28 (m, 1 H, 4Ј-H), 7.47 (m, 1 H, 5Ј-
H), 7.73 (m, 1 H, 2Ј-H), 7.92 (m, 1 H, 6Ј-H) ppm. 13C NMR
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Received: November 12, 2007
Published Online: January 17, 2008
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