Intermolecular and intramolecular pauson-khand reactions of functionalized Allenes

Article abstract of DOI:10.1002/ejoc.200701038

Pauson-Khand reactions of functionalized allenes with different alkynes give cyclopentenones with generally high regio-and stereoselectivities. The allenes react through their external double bonds, giving cyclopentenones with exocyclic double bond at their β positions and predominantly with E stereochemistry. Some intramolecular reactions with allenynes connected through aromatic rings are described. These give the corresponding heterocycles with moderate to good yields. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Full text of DOI:10.1002/ejoc.200701038

FULL PAPER
DOI: 10.1002/ejoc.200701038
Intermolecular and Intramolecular Pauson–Khand Reactions of Functionalized
Allenes
Álvaro González-Gómez,[a] Loreto Añorbe,[a] Amalia Poblador,[a] Gema Domínguez,[a] and
Javier Pérez-Castells*[a]
Keywords: Pauson–Khand reactions / Allenes / Cyclizations / Allenamides
Pauson–Khand reactions of functionalized allenes with dif-
ferent alkynes give cyclopentenones with generally high re-
gio- and stereoselectivities. The allenes react through their
external double bonds, giving cyclopentenones with exocy-
clic double bond at their β positions and predominantly with
E stereochemistry. Some intramolecular reactions with al-
lenynes connected through aromatic rings are described.
These give the corresponding heterocycles with moderate to
good yields.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
Introduction
The scope of the intermolecular Pauson–Khand[1] reac-
tion is still quite limited, as simple alkenes react poorly. The
reaction gives good results only with strained olefins such
as norbornene, some exocyclic alkenes, and certain all-
enes.[2] In addition, some vinyl ethers/esters[3] and vinyl sulf-
oxides[4] are also useful in the intermolecular PKR. Cyclo-
pentenones are structural features present in a large variety
of natural products, so an increase in the number of ef-
ficient methodologies for intramolecular PKRs would be
highly desirable. One strategy that circumvents the scope
problem consists of performing an intramolecular PKR
with an enyne bearing a traceless tether[5] or directing
groups such as pyridylsilyl moieties.[6] These methodologies
avoid the formation of regioisomeric mixtures. The inter-
molecular PKR is regioselective with regard to the alkyne
component, the bulkier substituent being situated adjacent
to the carbonyl in the final product. It has been demon-
strated that both steric and electronic effects may be respon-
sible for this regioselectivity.[7] Unsymmetrical olefins usu-
ally give mixtures of regioisomers (Scheme 1).
Scheme 1. Regioselectivity in the intermolecular PKR.
In a preliminary communication of this work, we ob-
served high regio- and stereoselectivities in the reactions be-
tween allenamides and alkynes.[11] There we used NMO for
promotion and reached yields varying from moderate to
good (45–85%). Here we present our complete work on all-
enes substituted with different heteroatoms and different
types of alkynes. We have developed new reaction condi-
tions that have improved on the preliminary results and we
include some novel examples of intramolecular reactions
with allenynes connected through aromatic rings.
Results and Discussion
The synthesis of starting allenes was effected by classical
strategies (Table 1). Starting from functionalized amides,
phenols or thiophenols 1, propargylation under basic or
Mitsunobu conditions gave the corresponding propargyl
derivatives 2 in good yields. These compounds were con-
verted into the corresponding allenes 3 by treatment with
tBuOK or NaH. In the synthesis of 3h some amounts of
allene were formed in the propargylation reaction but we
were unable to achieve good direct conversions from 1 into
3h that would improve the two-step process.[12] Some of
these allenes contained o-ethynyl or vinyl groups to allow
competence experiments to be performed or to serve as sub-
strates for intramolecular PKRs. The syntheses of (propa-
1,2-diene-1-sulfinyl)benzene (3k)[13] and (propa-1,2-diene-1-
sulfonyl)benzene (3l)[14] were carried out according to litera-
Allenes are important substrates in various metal-medi-
ated or catalyzed cyclizations.[8] With regard to the PKR,
there have been extensive studies in the intramolecular ver-
sion.[9] On the other hand, intermolecular PKRs have re-
ceived less attention. The main contributions have come
from Cazes’ group, who have carried out studies with all-
enic hydrocarbons.[10]
[a] Departamento de Química, Facultad de Farmacia, Universidad
San Pablo-CEU
Urb. Montepríncipe, 28668 Boadilla del Monte, Madrid, Spain
Fax: +34-913510496
E-mail: jpercas@ceu.es
Supporting information for this article is available on the
WWW under http://www.eurjoc.org/ or from the author.
1370
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 1370–1377

Pauson–Khand Reactions of Functionalized Allenes
ture procedures. The syntheses of allenamines were unsuc- in CH3CN (Entry 4) we obtained a 45% yield of the cyclo-
cessful, as we observed extensive decomposition of the pentenone 5a and a 7% yield of 4. Molecular sieves are
products in the reactions with the base.
known for acting as catalysts in the formation of enamines,
and it is thus possible that they accelerate the decomposi-
tion of our starting materials.[15] To avoid this we washed
the zeolites with Et3N and dried them prior to the PKR.
Under these conditions we achieved an 80% yield of 5a.
The only cyclopentenone isolated was assigned as 5a in
view of its NMR spectroscopic data and n.O.e. experi-
ments.[16] Additionally we tried to develop catalytic condi-
tions. Few efficient catalytic intermolecular PKRs have
been described to date. In this case we carried out two reac-
tions in the presence of 10% of cobalt under CO (1 atm) at
70 °C (Entries 6, 7). Both reactions gave poor yields of 5a,
reaching 25% when molecular sieves were used (Entry 7).
As in most of the examples described previously by
Cazes,[10] we only detected the products with the exocyclic
double bonds in the β positions. Other products, which we
assumed to be the Z isomers, could be detected in the crude
mixtures but not isolated. The conditions of Entry 4
(Table 1, procedure A) were used with the whole set of func-
tionalized allenes prepared, and the results are shown in
Table 3. With substrates 3i, 3k, and 3l the cobalt hexacar-
bonyl-alkyne complex was preformed and purified in DCM
prior to the PKR (procedure B). This procedure was neces-
sary to avoid decomposition of the allene in the presence of
cobalt species. The conditions of Entry 5 (procedure C)
were developed later, and were used with a selected group
of reactions.
In general the reactions were very selective. The allenes
reacted through their external double bonds independently
of the natures of the substituents, and gave the E isomers
as the major products. With allenamides 3a–3g, results were
similar regardless of the natures of the protecting groups
used. In the case of the reaction of trimethyl-pent-1-ynyl-
silane (Entry 9), a small amount of another isomer was iso-
lated. This compound, 13c, was the result of the reaction of
the alkyne with the other regioselectivity, due to the similar
bulkiness of the two constituents. Surprisingly, a small
amount of 15c was also observed in the reaction of pro-
tected propargyl alcohol (Entry 11). On the other hand,
small amounts of Z isomers could be isolated in the reac-
tions of Entries 10, 12 and 13. The reaction of Entry 5 was
planned in order to investigate the competition between the
allenic PKR vs. the possible reaction with the styrenic
double bond. The only reaction product observed in the
presence of hex-3-yne was 9a, showing the preference for
Table 1. Synthesis of starting allenes.
Product
R1
R2
X
% Yield[a]
3a
3b
3c
3d
3e
3f
MeO
F
H
MeO
MeO
H
H
Cl
Br
H
H
H
NAc
NAc
NAc
NTs
NCO2Et
NAc
NTs
S
55
69
82
70
45
78
86
60
72
74
H2C=CH
H
H
HCϵC
HCϵC
H
3g
3h
3i
H
HCϵC
O
O
3j
[a] Yields of pure product 3 from 1.
The PKR between compound 3a and p-tolylacetylene
was carried out under several sets of conditions, some of
them summarized in Table 2. Heat promotion and use of
molecular sieves as described by us previously were unsuc-
cessful, due to decomposition of the allenamide (Entries 1
and 2).[15] Under these conditions, the main reaction prod-
uct was acetanilide 4. We thus used trimethylamine N-oxide
(TMANO) and N-methylmorpholine N-oxide (NMO) as
promoters, testing several solvents. With the latter promoter
Table 2. PK reaction conditions for allenamide 3a.
No
Solvent
Metal complex/loading
T [°C]
Promoter
% Yield
5a
4
1
2
3
4
5
6
7
toluene
toluene
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
1.5 equiv. Co2(CO)8
1.5 equiv. Co2(CO)8
1.5 equiv. Co2(CO)8
1.5 equiv. Co2(CO)8
1.5 equiv. Co2(CO)8
0.1 equiv. Co2(CO)8/CO 1 atm
0.1 equiv. Co2(CO)8/CO 1 atm
∆
–
Ͻ5
10
32
45
75
28
8
room temp.
room temp.
room temp.
room temp.
70
4-Å MS, 9 equiv. TMANO
9 equiv. TMANO
6 equiv. NMO
4-Å MS (Et3N), 6 equiv. NMO 80
–
7
Ͻ5
20
Ͻ5
10
25
70
4-Å MS (Et3N)
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J. Pérez-Castells et al.
FULL PAPER
Table 3. PKRs of functionalized allenes.
[a] Yields of pure products are given as obtained by Procedure A/Procedure C. [b] Yield of pure product obtained by Procedure A. [c]
Products 13a and 13c, 14a and 14b, and 16a and 16b were obtained by Procedure A as pure mixtures. Quantities of major products 13a
and 16a could be obtained pure and characterized; yields for 13c, 14a, 14b, and 16b are estimated from the ratios in the mixtures. [d]
Yields of pure products are given as obtained with Procedure B/Procedure C. [e] Yield of pure product obtained with Procedure B.
the reaction with the allene. Allenes bearing sulfur and oxy- of the reaction of 3f. We decided to switch the protecting
gen groups reacted with lower yields. Oxygen-containing al- group in the allene to tosyl and performed the intramolecu-
lene 3i gave a ca. 1:1 E/Z mixture of cyclopentenones when lar PKR with substrate 3g. Under these conditions we iso-
reacting with hex-3-yne (Entry 13). However, in the reac- lated product 23 in 43% yield. On the other hand, the intra-
tion with phenylacetylene (Entry 14) it gave low yields of molecular PKR of allene 3j gave product 24 in 22% yield
the products arising from the other regioselectivity with re- with Co2(CO)8. When we applied reaction conditions with
spect to the allene. In the case of the sulfoxide and the sul- Mo(CO)6, a mixture of 24 (25%) and 25 (38%) was ob-
fone (Entries 15, 16 and 17) the allene reacted partially or tained. This result follows previous observations by Brum-
only (Entry 16) with this latter regioselectivity.
Traditionally, electron-deficient olefins have been consid-
ered bad substrates for PK reactions, although Carretero
showed good results in intramolecular PKRs with olefins
substituted with EWGs including sulfoxides and sulfones.[17]
Our results show that these groups do not prevent the all-
enic PKR. In addition, no insertion or cyclotrimerization
products were detected. The reaction of Entry 17 was de-
scribed by Cazes previously,[10c] but gave a similar distribu-
tion of products and better yields with our Procedure C.
We extended this methodology to some intramolecular
examples (Scheme 2). The reaction between allene 3f and
Co2(CO)8 gave no intramolecular PK products under any
conditions. This starting product reacted with hex-3-yne to
give 22a in 15% yield under Procedure A conditions and in
45% yield under Procedure C conditions. Using molybde-
num as the metal, under previously described conditions,[18]
we detected the intramolecular PKR in the crude mixture Scheme 2. Intramolecular PKRs with allenynes.
1372
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 1370–1377

Pauson–Khand Reactions of Functionalized Allenes
General Procedure for the Intramolecular Pauson–Khand Reactions
with Co2(CO)8: A solution of the allenyne (1.00 mmol) in MeCN
(9 mL) and Co2(CO)8 (1.50 mmol) was stirred for 1 h at room temp.
4-Methylmorpholine N-oxide (6.00 mmol) was then added at 0 °C,
and the mixture was stirred until completion of the reaction (TLC).
The reaction was filtered through Celite and was washed with
MeCN (20 mL). The solvent was removed under vacuum, and the
residue was purified by silica gel flash chromatography (hexane/
AcOEt, mixtures).
mond, who was able to direct the PKR of allenes to either
the external or the internal double bond by tuning the reac-
tion conditions.[19]
Conclusions
We have shown that allenes with different functionalities
are good substrates for intermolecular Pauson–Khand reac-
tions with symmetric and unsymmetrical alkynes. The reac-
tion conditions have been tuned up and allow excellent
yields to be achieved in stoichiometric reactions. Catalytic
processes, however, did not give satisfactory results. Under
both sets of experimental conditions a positive effect of mo-
lecular sieves was observed. The PKRs gave, in general,
either single or major products arising from reactions
through the external bonds of the allenes. These products
present the exocyclic double bonds at the β-positions from
the ketones with E stereochemistry. As a result of this work,
new cyclopentenones with interesting functionalities have
been obtained. In addition we have shown some examples
of intramolecular PKRs with allenynes connected through
aromatic rings that give polycyclic heterocycles.
General Procedure for the Intramolecular Pauson–Khand Reactions
with Mo(CO)6: DMSO (0.86 mL, 10.00 mmol) and Mo(CO)6
(317 mg, 1.20 mmol) were added to a solution of the allenyne
(1.00 mmol) in toluene (10 mL). The resulting mixture was stirred
for 1h at 80 °C. The reaction mixture was filtered through Celite,
and the solvent was removed under vacuum. The residue was puri-
fied by silica gel flash chromatography (hexane/AcOEt, mixtures).
General Procedure for Intramolecular Pauson–Khand Reactions with
Mo(MeCN)3(CO)3: Mo(MeCN)3(CO)3 (0.34 mmol) was added at
0 °C to a solution of the allenyne (0.30 mmol) in toluene (15 mL).
The resulting mixture was stirred for 1h at room temp. The reaction
mixture was filtered through Celite and the solvent was removed
under vacuum. The residue was purified by silica gel flash
chromatography (hexane/AcOEt, mixtures).
N-(4-Methoxyphenyl)-N-{(E)-[3-(4-methylphenyl)-4-oxocyclopent-2-
en-1-ylidene]methyl}acetamide (5a): Treatment of 1-ethynyl-4-meth-
ylbenzene (0.21 g, 1.85 mmol) and N-(4-methoxyphenyl)-N-(propa-
1,2-dienyl)acetamide (0.25 g, 1.23 mmol) as described in Pro-
cedure A for Pauson–Khand intermolecular reactions afforded
pure 5a (0.19 g, 45%) as a colorless oil after flash chromatography
(hexane/AcOEt, 4:1). After treatment as described in Procedure C,
the reaction afforded 5a (0.34 g, 80%, from 0.25 g, 1.23 mmol of
allenamide 3a). 1H NMR (300 MHz, CDCl3): δ = 1.95 (s, 3 H),
2.20 (s, 2 H), 2.34 (s, 3 H), 3.87 (s, 3 H), 6.98 (d, J = 7.9 Hz, 2 H),
7.16 (d, J = 7.9 Hz, 4 H), 7.64 (d, J = 8.5 Hz, 2 H), 7.71 (s, 1 H),
7.96 (s, 1 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 21.3, 22.9,
38.8, 55.4, 115.1, 119.6, 125.3, 126.6, 128.7, 129.1, 130.0, 132.1,
Experimental Section
Procedure A for Pauson–Khand Intermolecular Reactions: A solu-
tion of the alkyne (1.50 mmol) in MeCN (9 mL) and Co2(CO)8
(1.50 mmol) was stirred for 1 h, and 4-methylmorpholine N-oxide
(6.00 mmol) was then added at 0 °C. The allene (1.00 mmol) in
MeCN (9 mL) was added dropwise, and the mixture was stirred at
0 °C until completion of the reaction (TLC). The reaction was fil-
tered through Celite and was washed with MeCN (20 mL). The
solvent was removed under vacuum and the residue was purified
by silica gel flash chromatography (hexane/AcOEt, mixtures).
138.0, 138.1, 156.0, 160.0, 170.4, 203.5 ppm. n.O.e (H7.96 Ǟ H7.71
,
6.4%). IR (film): ν = 1675, 1630 cm–1. C H NO (347.41): calcd.
˜
22 21
3
C 76.06, H 6.09, N 4.03; found C 76.30, H 6.12, N 3.84.
Procedure B for Pauson–Khand Intermolecular Reactions: A solu-
tion of the alkyne (1.50 mmol) in DCM (9 mL) and Co2(CO)8
(1.50 mmol) was stirred for 45 min at room temp. When the com-
plex had been formed (TLC), the solvent was eliminated under vac-
uum and the residue was purified by flash chromatography (hex-
ane). The complex (1.00 mmol) in MeCN (9 mL) was added at
–5 °C to a solution of the allene (1.00 mmol) in MeCN (9 mL) and
4-methylmorpholine N-oxide (6.00 mmol), and the mixture was
stirred at –5 °C until completion of the reaction (TLC). The reac-
tion mixture was filtered through Celite and was washed with
MeCN (20 mL). The solvent was removed under vacuum, and the
residue was purified by silica gel flash chromatography (hexane/
AcOEt, mixtures).
N-[(E)-(3-Butyl-4-oxocyclopent-2-en-1-ylidene)methyl]-N-(4-meth-
oxyphenyl)acetamide (6a): Treatment of hex-1-yne (0.15 g,
1.85 mmol) and N-(4-methoxyphenyl)-N-(propa-1,2-dienyl)acet-
amide (0.25 g, 1.23 mmol) as described in Procedure A for Pauson–
Khand intermolecular reactions afforded pure 6a (0.18 g, 50%) as
a colorless oil after flash chromatography (hexane/AcOEt, 2:1). 1H
NMR (300 MHz, CDCl3): δ = 0.86 (t, J = 7.1 Hz, 3 H), 1.24–146
(m, 4 H), 1.91 (s, 3 H), 2.01 (s, 2 H), 2.15 (t, J = 7.1 Hz, 2 H), 3.84
(s, 3 H), 6.93 (d, J = 8.8 Hz, 2 H), 7.12 (d, J = 8.2 Hz, 2 H), 7.47
(s, 1 H), 7.53 (s, 1 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 13.7,
22.3, 22.8, 24.2, 29.9, 37.5, 55.4, 115.0, 120.3, 123.7, 129.9, 132.3,
143.0, 156.7, 159.9, 170.3, 205.6 ppm. n.O.e (H7.53 Ǟ H7.47, 6.0%).
IR (film): ν = 1680, 1640 cm–1. C19H23NO3 (313.39): calcd. C
˜
Procedure C for Pauson–Khand Intermolecular Reactions: A solu-
tion of the alkyne (1.50 mmol) in MeCN (9 mL) and Co2(CO)8
(1.50 mmol) was stirred for 1 h, and powdered molecular sieves
(previously washed with Et3N and dried, 4 g) and 4-methylmor-
pholine N-oxide (6.00 mmol) were then added at 0 °C. The allene
(1.00 mmol) in MeCN (9 mL) was added dropwise, and the mixture
was stirred at 0 °C until completion of the reaction (TLC). The
reaction mixture was filtered through Celite and was washed with
MeCN (20 mL). The solvent was removed under vacuum and the
residue was purified by silica gel flash chromatography (hexane/
AcOEt, mixtures).
72.82, H 7.40, N 4.47; found C 72.99, H 7.25, N 4.28.
N-[(E)-(2,3-Diethyl-4-oxocyclopent-2-en-1-ylidene)methyl]-N-(4-
methoxyphenyl)acetamide (7a): Treatment of hex-3-yne (0.15 g,
1.85 mmol) and N-(4-methoxyphenyl)-N-(propa-1,2-dienyl)acet-
amide (0.25 g, 1.23 mmol) as described in Procedure A for Pauson–
Khand intermolecular reactions afforded pure 7a (0.24 g, 65%) as
a brown oil after flash chromatography (hexane/AcOEt, 2:1). 1H
NMR (300 MHz, CDCl3): δ = 0.98 (t, J = 7.4 Hz, 3 H), 1.22 (t, J
= 7.7 Hz, 3 H), 1.95 (s, 3 H), 2.02 (s, 2 H), 2.21 (q, J = 7.5 Hz, 2
H), 2.60 (q, J = 7.7 Hz, 2H2), 3.87 (s, 3 H), 6.95 (d, J = 8.8 Hz, 2
Eur. J. Org. Chem. 2008, 1370–1377
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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1373

J. Pérez-Castells et al.
H), 7.14 (d, J = 8.8 Hz, 2 H), 7.65 (s, 1 H) ppm. 13C NMR son–Khand intermolecular reactions afforded pure 11a (0.17 g,
FULL PAPER
(75 MHz, CDCl3): δ = 13.0, 13.7, 16.2, 19.1, 22.6, 36.8, 55.1, 114.7,
119.5, 121.0, 129.7, 132.4, 140.3, 159.5, 169.9, 170.2, 204.3 ppm.
71%) as a yellow oil after flash chromatography (hexane/AcOEt,
4:1). H NMR (300 MHz, CDCl3): δ = 0.98 (t, J = 7.2 Hz, 3 H),
1
n.O.e (H7.65 Ǟ H2.60, 8.2%; Ǟ H1.22, 4.5%). IR (film): ν = 1670,
1.19–1.24 (m, 6 H), 2.03 (d, J = 1.1 Hz, 2 H), 2.21 (q, J = 7.7 Hz,
˜
1640 cm–1. C19H23NO3 (313.39): calcd. C 72.82, H 7.40, N 4.47; 2 H), 2.57 (q, J = 7.7 Hz, 2 H), 3.84 (s, 3 H), 4.23 (q, J = 7.1 Hz,
found C 72.54, H 7.67, N 4.40.
2 H), 6.88 (d, J = 6.6 Hz, 2 H), 7.10 (d, J = 6.6 Hz, 2 H), 7.34 (s,
1 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 13.3, 14.0, 14.3, 16.5,
19.5, 37.3, 55.3, 62.9, 114.3, 119.5, 122.8, 129.5, 131.6, 140.3, 154.7,
N-[(E)-(2,3-Diethyl-4-oxocyclopent-2-en-1-ylidene)methyl]-N-(4-
fluorophenyl)acetamide (8a): Treatment of hex-3-yne (0.16 g,
1.96 mmol) and N-(4-fluorophenyl)-N-(propa-1,2-dienyl)acetamide
(0.25 g, 1.31 mmol) as described in Procedure A for Pauson–Khand
intermolecular reactions afforded pure 8a (0.27 g, 61%) as a yellow
oil after flash chromatography (hexane/AcOEt, 4:1). 1H NMR
(300 MHz, CDCl3): δ = 0.95 (t, J = 7.7 Hz, 3 H), 1.19 (t, J =
7.7 Hz, 3 H), 1.92 (s, 3 H), 1.96 (s, 2 H), 2.19 (q, J = 7.5 Hz, 2 H),
2.57 (q, J = 7.7 Hz, 2 H), 7.15–7.22 (m, 4 H), 7.60 (s, 1 H) ppm.
13C NMR (75 MHz, CDCl3): δ = 13.2, 13.9, 16.5, 19.4, 22.9, 37.1,
117.1 (d, J = 22.5 Hz), 120.5, 121.1, 130.7 (d, J = 8.4 Hz), 136.3
(d, J = 3.1 Hz), 141.1, 162.4 (d, J = 249.5 Hz), 169.1, 170.0,
204.2 ppm. n.O.e (H7.60 Ǟ H2.57, 7.8%; Ǟ H1.19, 3.6%). IR (film):
159.1, 169.8, 204.8 ppm. n.O.e (H7.34 Ǟ H2.57, 4.8 %; Ǟ H1.22
,
2.6%). IR (film): ν = 1710, 1680, 1650 cm–1. C H NO (343.42):
˜
20 25
4
calcd. C 69.95, H 7.34, N 4.08; found C 70.24, H 7.55, N 3.86.
N-(4-Methoxyphenyl)-4-methyl-N-{(E)-[3-(4-methylphenyl)-4-oxo-
cyclopent-2-en-1-ylidene]methyl}benzenesulfonamide (12a): Treat-
ment of 1-ethynyl-4-methylbenzene (80 mg, 0.71 mmol) and N-(4-
methoxyphenyl)-4-methyl-N-(propa-1,2-dienyl)benzenesulfon-
amide (150 mg, 0.48 mmol) as described in Procedure A for Pau-
son–Khand intermolecular reactions afforded pure 12a (80 mg,
35%) as a brown oil after flash chromatography (hexane/AcOEt,
4:1). After treatment as described in Procedure C, the reaction af-
forded 12a (0.20 g, 55%) from allenamide 3d (0.25 g, 0.79 mmol).
1H NMR (300 MHz, CDCl3): δ = 2.18 (s, 2 H), 2.35 (s, 3 H), 2.46
(s, 3 H), 3.85 (s, 3 H), 6.84 (d, J = 9.4 Hz, 2 H), 6.93 (d, J = 8.8 Hz,
2 H), 7.17 (d, J = 7.7 Hz, 2 H), 7.31 (d, J = 8.2 Hz, 2 H), 7.34 (s,
1 H), 7.58 (d, J = 8.2 Hz, 2 H), 7.62 (d, J = 8.2 Hz, 2 H), 7.93 (s,
1 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 21.3, 21.7, 38.9, 55.4,
114.6, 118.2, 126.4, 126.6, 127.7, 128.6, 129.2, 129.5, 129.8, 131.6,
ν = 1675, 1640 cm–1. C H FNO (301.36): calcd. C 71.74, H 6.69,
˜
18 20
2
N 4.65; found C 71.40, H 6.39, N 4.70.
N-[(E)-(2,3-Diethyl-4-oxocyclopent-2-en-1-ylidene)methyl]-N-(2-eth-
enylphenyl)acetamide (9a): Treatment of hex-3-yne (0.10 g,
1.19 mmol) and N-(propa-1,2-dienyl)-N-(2-vinylphenyl)acetamide
(0.15 g, 0.75 mmol) as described in Procedure A for Pauson–Khand
intermolecular reactions afforded pure 9a (0.13 g, 58%) as a yellow
oil after flash chromatography (hexane/AcOEt, 4:1). After treat-
ment as described in Procedure C, the reaction afforded 9a (0.33 g,
85%) from allenamide 3c (0.25 g, 1.26 mmol). 1H NMR (300 MHz,
CDCl3): δ = 0.93 (t, J = 7.4 Hz, 3 H), 1.19 (t, J = 7.7 Hz, 3 H),
1.82 (d, J = 20.9 Hz, 1 H), 1.83 (s, 3 H), 1.93 (d, J = 20.9 Hz, 1
H), 2.16 (q, J = 7.5 Hz, 2 H), 2.57 (q, J = 7.5 Hz, 2 H), 5.36 (d, J
= 11.0 Hz, 1 H), 5.80 (d, J = 17.6 Hz, 1 H), 6.58 (dd, J1 = 17.6, J2
= 11.0 Hz, 1 H), 7.15 (d, J = 7.1 Hz, 1 H), 7.34 (t, J = 7.1 Hz, 1
H), 7.43 (t, J = 7.4 Hz, 1 H), 7.65 (d, J = 8.2 Hz, 1 H), 7.69 (s, 1
H) ppm. 13C NMR (75 MHz, CDCl3): δ = 13.2, 14.0, 16.4, 19.6,
22.6, 36.5, 118.2, 119.5, 120.4, 126.5, 129.2, 129.5, 129.8, 130.6,
136.3, 137.4, 140.8, 170.1, 204.7 ppm. n.O.e (H7.69 Ǟ H2.57, 4.3%;
134.6, 137.5, 138.1, 144.7, 155.2, 160.3, 203.2 ppm. n.O.e (H7.93
Ǟ
.
H7.34, 18.0 %). IR (film): ν = 1680, 1620, 1350, 1160 cm–1
˜
C27H25NO4S (459.56): calcd. C 70.57, H 5.48, N 3.05; found C
70.33, H 5.65, N 3.30.
(E)-N-(4-Methoxyphenyl)-4-methyl-N-[4-oxo-2-propyl-3-(trimethyl-
silanyl)cyclopent-2-enylidenemethyl]benzenesulfonamide (13a) and
(E)-N-(4-Methoxyphenyl)-4-methyl-N-[4-oxo-3-propyl-2-(trimethyl-
silanyl)cyclopent-2-enylidenemethyl]benzenesulfonamide (13c):
Treatment of trimethyl(pent-1-ynyl)silane (0.22 mL, 1.19 mmol)
and N-(4-methoxyphenyl)-4-methyl-N-(propa-1,2-dienyl)benzene-
sulfonamide (0.25 g, 0.79 mmol) as described in Procedure A for
Pauson–Khand intermolecular reactions afforded 13a and 13c
(0.33 g, 85%) as a mixture of isomers (4:1). After purification by
flash chromatography (hexane/AcOEt, 6:1), pure 13a (0.28 g, 73%)
was obtained as a brown oil.
Ǟ H1.19, 2.5 %). IR (film): ν = 1680, 1640 cm–1. C20H23NO2
˜
(309.40): calcd. C 77.64, H 7.49, N 4.53; found C 77.38, H 7.58, N
4.32.
1
Data for 13a: H NMR (300 MHz, CDCl3): δ = 0.18 (s, 9 H), 1.08
N-[(E)-(2,3-Diethyl-4-oxocyclopent-2-en-1-ylidene)methyl]-N-(4-
methoxyphenyl)-4-methylbenzenesulfonamide (10a): Treatment of
hex-3-yne (0.10 g, 1.19 mmol) and N-(4-methoxyphenyl)-4-methyl-
N-(propa-1,2-dienyl)benzenesulfonamide (0.25 g, 0.79 mmol) as de-
scribed in Procedure A for Pauson–Khand intermolecular reac-
tions afforded pure 10a (0.29 g, 85%) as a white solid after flash
(t, J = 7.4 Hz, 3 H), 1.54–1.67 (m, 2 H), 1.96 (br. s, 2 H), 2.44 (s,
3 H), 2.59–2.64 (m, 2 H), 3.81 (s, 3 H), 6.78–6.82 (m, 2 H), 6.85–
6.90 (m, 2 H), 7.29 (d, J = 8.2 Hz, 2 H), 7.30 (s, 1 H), 7.54 (d, J =
8.2 Hz, 2 H) ppm. 13C NMR (75 MHz, CDCl3): δ = –0.4, 14.5,
21.6, 24.3, 30.5, 38.4, 55.4, 114.4, 121.3, 123.3, 127.6, 128.9, 129.7,
1
131.4, 134.7, 138.1, 144.5, 160.0, 181.0, 209.0 ppm. n.O.e (H2.59 Ǟ
chromatography (hexane/AcOEt, 2:1 to 1:1). M.p. 122–124 °C. H
H
7.30, 12.0%; Ǟ H0.18, 5.4%). IR (film): ν = 1670, 1630, 1360,
˜
NMR (300 MHz, CDCl3): δ = 0.91 (t, J = 7.7 Hz, 3 H), 1.18 (t, J
= 7.7 Hz, 3 H), 1.96 (s, 2 H), 2.14 (q, J = 7.7 Hz, 2 H), 2.38 (s, 3
H), 2.53 (q, J = 7.7 Hz, 2 H), 3.75 (s, 3 H), 6.75 (d, J = 9.3 Hz, 2
H), 6.85 (d, J = 8.8 Hz, 2 H), 7.16 (s, 1 H), 7.24 (d, J = 8.2 Hz, 2
H), 7.50 (d, J = 8.2 Hz, 2 H) ppm. 13C NMR (75 MHz, CDCl3): δ
= 13.2, 13.8, 16.3, 19.3, 21.4, 37.0, 55.2, 114.3, 119.1, 122.0, 127.4,
129.2, 129.6, 131.2, 134.6, 140.4, 144.3, 159.8, 169.0, 204.2 ppm.
1170 cm–1. C26H33NO4SSi (483.70): calcd. C 64.56, H 6.88, N 2.90,
S 6.63; found C 67.31, H 6.65, N 3.08, S 6.49.
Data for 13c: Mixture of isomers 13c and 13a. 1H NMR (300 MHz,
CDCl3): δ = 0.44 (s, 9 H), 0.90 (t, J = 7.4 Hz, 3 H), 1.26–1.36 (m,
2 H), 2.06 (s, 2 H), 2.22–2.27 (m, 2 H), 2.45 (s, 3 H), 3.83 (s, 3 H),
6.79–6.82 (m, 2 H), 6.86–6.94 (m, 2 H), 7.23 (br. s, 1 H), 7.27–7.31
(m, 2 H), 7.50–7.56 (m, 2 H) ppm. 13C NMR (75 MHz, CDCl3): δ
= 0.9, 14.1, 23.4, 27.1, 29.6, 37.5, 55.3, 114.3, 124.9, 125.8, 129.5,
129.6, 130.0, 131.0, 134.6, 152.0, 154.4, 159.7, 166.8, 205.7 ppm.
n.O.e (H7.16 Ǟ H2.53, 5.8%; Ǟ H1.18, 3.0%). IR (KBr): ν = 1690,
˜
1630, 1350, 1180 cm–1. C24H27NO4S (425.54): calcd. C 67.74, H
6.40, N 3.29, S 7.54; found C 67.87, H 6.48, N 3.41, S 7.26.
Ethyl [(E)-(2,3-Diethyl-4-oxocyclopent-2-en-1-ylidene)methyl](4-
methoxyphenyl)carbamate (11a): Treatment of hex-3-yne (0.10 g,
1.19 mmol) and ethyl N-(4-methoxyphenyl)(propa-1,2-dienyl)car-
bamate (0.15 g, 0.75 mmol) as described in Procedure A for Pau-
(E)-N-[2-(tert-Butyldimethylsilanyl)oxymethyl-4-oxo-3-(trimethylsil-
anyl)cyclopent-2-enylidenemethyl]-N-(4-methoxyphenyl)-4-methyl-
benzenesulfonamide (14a), (Z)-N-[3-(tert-Butyldimethylsilanyl)oxy-
methyl-4-oxo-2-(trimethylsilanyl)cyclopent-2-enylidenemethyl]-N-(4-
1374
www.eurjoc.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 1370–1377

Pauson–Khand Reactions of Functionalized Allenes
methoxyphenyl)-4-methylbenzenesulfonamide (14b), (E)-N-[4-(tert-
Butyldimethylsilanyl)oxymethyl-2-oxo-3-(trimethylsilanyl)cyclopent-
3-enylidenemethyl]-N-(4-methoxyphenyl)-4-methylbenzenesulfon-
amide (14d), and (Z)-N-[4-(tert-Butyldimethylsilanyl)oxymethyl-2-
oxo-3-(trimethylsilanyl)cyclopent-3-enylidenemethyl]-N-(4-methoxy-
phenyl)-4-methylbenzenesulfonamide (14e): Treatment of 3-(tert-bu-
tyl-dimethyl-silanyloxy)-1-(trimethylsilanyl)propyne (0.29 g,
1.19 mmol) and N-(4-methoxyphenyl)-4-methyl-N-(propa-1,2-di-
enyl)benzenesulfonamide (0.25 g, 0.79 mmol) as described in Pro-
cedure A for Pauson–Khand intermolecular reactions afforded a
mixture of isomers 14a–14e (0.36 g, 78%). After purification by
flash chromatography (hexane/AcOEt, 9:1), 14a and 14b (0.33 g,
71%) were obtained as a mixture of Z,E isomers (7:1), while 14d
(14 mg, 3%) and 14e (18 mg, 4%) were obtained as yellow oils.
After treatment as described in Procedure C, the reaction afforded
14a and 14b as a mixture of Z,E isomers (6:1, 0.37 g, 81%) from
allenamide 3d (0.25 g, 0.79 mmol).
tions afforded pure 15a (0.15 g, 37%) and 15c (28 mg, 7%) as col-
orless oils after flash chromatography (hexane/AcOEt, 4:1).
1
Data for 15a: H NMR (300 MHz, CDCl3): δ = 0.07 (s, 6 H), 0.93
(s, 9 H), 2.03 (d, J = 1.1 Hz, 2 H), 2.44 (s, 3 H), 3.82 (s, 3 H), 4.35
(br. s, 2 H), 6.81 (d, J = 8.8 Hz, 2 H), 6.89 (d, J = 8.8 Hz, 2 H),
7.30 (d, J = 8.2 Hz, 2 H), 7.57 (d, J = 8.2 Hz, 2 H), 7.65 (s, 1
H) ppm. 13C NMR (75 MHz, CDCl3): δ = –5.5, 18.3, 21.6, 25.7,
38.2, 55.4, 57.8, 114.5, 118.4, 125.9, 127.6, 128.7, 129.6, 129.7,
131.5, 134.7, 141.9, 144.5, 156.2, 160.2, 203.6 ppm. n.O.e. (H7.65 Ǟ
H7.30, 15 %). IR (film): ν = 1670, 1620, 1370, 1160 cm–1
.
˜
C27H35NO5SSi (513.72): calcd. C 63.13, H 6.87, N 2.73, S 6.24;
found C 63.38, H 6.45, N 2.83, S 5.88.
1
Data for 15c: H NMR (300 MHz, CDCl3): δ = 0.15 (s, 6 H), 0.95
(s, 9 H), 2.05 (s, 2 H), 2.45 (s, 3 H), 3.82 (s, 3 H), 4.69 (s, 2 H),
6.07 (s, 1 H), 6.81 (d, J = 7.1 Hz, 2 H), 6.89 (d, J = 6.6 Hz, 2 H),
7.22 (s, 1 H), 7.29 (d, J = 8.8 Hz, 2 H), 7.54 (d, J = 8.2 Hz, 2
H) ppm. n.O.e. (H7.22 Ǟ H7.54, 6.9%; Ǟ H4.69, 9.6%). IR (film): ν
˜
= 1670, 1620, 1370, 1160 cm–1. C27H35NO5SSi (513.72): calcd. C
63.13, H 6.87, N 2.73, S 6.24; found C 62.79, H 6.53, N 2.44, S
6.70.
Data for (E)-N-[2-(tert-Butyldimethylsilanyl)oxymethyl-4-oxo-3-(tri-
methylsilanyl)cyclopent-2-enylidenemethyl]-N-(4-methoxyphenyl)-4-
methylbenzenesulfonamide (14a), (Z)-N-[3-(tert-Butyldimethylsilan-
yloxy)methyl-4-oxo-2-(trimethylsilanyl)cyclopent-2-enylidene-
methyl]-N-(4-methoxyphenyl)-4-methylbenzenesulfonamide (14b):
1H NMR (300 MHz, CDCl3): δ = 0.20 (s, 9 H), 0.22 (s, 6 H), 0.99
(s, 9 H), 2.01 (s, 2 H), 2.43 (s, 3 H), 3.81 (s, 3 H), 4.26 (s, 2 H,
isomer 14b), 4.71 (s, 2 H, isomer 14a), 6.79 (d, J = 9.3 Hz, 2 H),
6.89 (d, J = 8.8 Hz, 2 H), 7.25 (d, J = 8.2 Hz, 2 H), 7.39 (br. s, 1
H, isomer 14b) 7.52 (d, J = 8.2 Hz, 2 H), 7.73 (t, J = 1.1 Hz, 1 H,
isomer 14a) ppm. 13C NMR (75 MHz, CDCl3): δ = –5.3, –5.2, –0.2,
0.6, 18.2, 18.3, 21.6, 25.9, 25.9, 37.6, 38.9, 53.7, 55.3, 55.4, 59.2,
114.4, 114.4, 120.0, 124.4, 125.7, 126.7, 127.7, 129.2, 129.4, 129.6,
129.7, 131.3, 131.6, 134.6, 134.8, 138.9, 144.3, 144.5, 148.6, 159.9,
(4E)-4-{[(4-Chlorophenyl)sulfanyl]methylidene}-2,3-diethylcyclopent-
2-en-1-one (16a) and (4Z)-4-{[(4-Chlorophenyl)sulfanyl]-
methylidene}-2,3-diethylcyclopent-2-en-1-one (16b): Treatment of
hex-3-yne (0.19 mL, 1.65 mmol) and 1-chloro-4-(propa-1,2-dienyl-
sulfanyl)benzene (0.20 g, 1.11 mmol) as described in Procedure A
for Pauson–Khand intermolecular reactions afforded pure 16a
(0.08 g, 25%) as a colorless oil and a mixture (1:1) of 16a and 16b
(25 mg, 8%) after flash chromatography (hexane/AcOEt, 4:1).
Data for 16a: 1H NMR (300 MHz, CDCl3): δ = 1.06 (t, J = 7.7 Hz,
3 H), 1.18 (t, J = 7.7 Hz, 3 H), 2.30 (q, J = 7.7 Hz, 2 H), 2.54 (q,
J = 7.7 Hz, 2 H), 2.99 (s, 2 H), 6.45 (s, 1 H), 7.34 (s, 4 H) ppm.
13C NMR (75 MHz, CDCl3): δ = 13.3, 13.8, 16.8, 19.2, 38.4, 118.2,
129.5, 130.9, 133.3, 133.6, 136.8, 144.4, 166.1, 203.4 ppm. n.O.e.
159.9, 172.8, 176.9, 204.4, 209.2 ppm. n.O.e. (H4.71 Ǟ H7.73
,
9.7%) ppm.
1
Data for 14d: H NMR (300 MHz, CDCl3): δ = 0.07 (s, 6 H), 0.19
(s, 9 H), 0.79 (s, 9 H), 2.32 (s, 2 H), 2.43 (s, 3 H), 3.82 (s, 3 H),
4.43 (s, 2 H), 6.83 (d, J = 9.3 Hz, 2 H), 6.93 (d, J = 8.8 Hz, 2 H),
7.27 (d, J = 8.2 Hz, 2 H), 7.58 (d, J = 8.2 Hz, 2 H), 7.94 (s, 1
H) ppm. 13C NMR (75 MHz, CDCl3): δ = –5.7, –0.5, 18.0, 21.6,
25.7, 33.8, 55.2, 62.2, 114.2, 115.3, 127.9, 129.0, 129.7, 131.4, 131.5,
(H6.45 Ǟ H7.34, 5.1%; Ǟ H2.54, 5.1%; Ǟ H1.18, 2.7%). IR (film): ν
˜
= 1680 cm–1. C16H17ClOS (292.82): calcd. C 65.63, H 5.85, S 10.95;
found C 65.87, H 5.59, S 11.27.
Data for 16b: (From the mixture of 16a and 16b): 1H NMR
(300 MHz, CDCl3): δ = 0.89 (t, J = 7.7 Hz, 3 H), 1.06 (t, J = 7.
7 Hz, 3 H), 2.30 (q, J = 7.7 Hz, 2 H), 2.84 (q, J = 7.7 Hz, 2 H),
3.06 (s, 2 H), 6.27 (s, 1 H), 7.32–7.36 (m, 4 H) ppm.
134.7, 138.6, 144.5, 160.1, 179.5, 201.1 ppm. n.O.e. (H2.32 Ǟ H4.43
,
2.0%; Ǟ H6.93, 5%), (H7.94 Ǟ H7.58, 7.0%). IR (film): ν = 1680,
˜
1620, 1370, 1160 cm–1. C30H43NO5SSi2 (585.90): calcd. C 61.50, H
7.40, N 2.39, S 5.47; found C 61.19, H 7.77, N 2.53, S 5.11.
(4E)-4-[(4-Bromophenoxy)methylene]-2,3-diethylcyclopent-2-en-1-
one (17a) and (4Z)-4-[(4-Bromophenoxy)methylene]-2,3-diethylcy-
clopent-2-en-1-one (17b): Treatment of hex-3-yne (0.12 mL,
1.07 mmol) and 1-bromo-4-(propa-1,2-dienyloxy)benzene (150 mg,
0.71 mmol) as described in Procedure B for Pauson–Khand inter-
molecular reactions afforded pure 17a (67 mg, 29%) as a white so-
lid (m.p. 110–112 °C) and 17b (44 mg, 20%) as a white solid (m.p.
82–84 °C) after flash chromatography (hexane and hexane/AcOEt,
9:1).
1
Data for 14e: H NMR (300 MHz, CDCl3): δ = 0.02 (s, 9 H), 0.09
(s, 6 H), 0.93 (s, 9 H), 2.42 (s, 3 H), 3.32 (s, 2 H), 3.78 (s, 3 H),
4.54 (s, 2 H), 6.75 (d, J = 8.8 Hz, 2 H), 7.02 (s, 1 H), 7.03 (d, J =
9.3 Hz, 2 H), 7.24 (d, J = 8.2 Hz, 2 H), 7.46 (d, J = 8.2 Hz, 2
H) ppm. 13C NMR (75 MHz, CDCl3): δ = –5.4, –0.8, 18.3, 21.6,
25.7, 36.3, 55.4, 62.3, 113.4, 119.8, 127.9, 129.5, 129.6, 129.7, 133.2,
134.3, 142.0, 144.2, 158.6, 177.7, 195.1 ppm. n.O.e. (H3.32 Ǟ H4.54
,
1.9%; Ǟ H7.02, 9.4%). IR (film): ν = 1670, 1620, 1360, 1170 cm–1.
Data for 17a: 1H NMR (300 MHz, CDCl3): δ = 1.05 (t, J = 7.7 Hz,
3 H), 1.22 (t, J = 7.7 Hz, 3 H), 2.29 (q, J = 7.7 Hz, 2 H), 2.54 (q,
J = 7.7 Hz, 2 H), 3.07 (s, 2 H), 6.77 (s, 1 H), 6.94 (d, J = 8.8 Hz,
2 H), 7.46 (d, J = 8.8 Hz, 2 H) ppm. 13C NMR (75 MHz, CDCl3):
δ = 13.4, 14.0, 16.5, 19.7, 36.0, 115.9, 118.4, 121.5, 132.6, 135.3,
142.9, 156.1, 166.0, 203.9 ppm. n.O.e (H6.76 Ǟ H2.54, 3.7 %; Ǟ
˜
C30H43NO5SSi2 (585.90): calcd. C 61.50, H 7.40, N 2.39, S 5.47;
found C 61.37, H 7.66, N 2.01, S 5.19.
(E)-N-[3-(tert-Butyldimethylsilanyl)oxymethyl-4-oxocyclopent-2-en-
ylidenemethyl]-N-(4-methoxyphenyl)-4-methylbenzenesulfonamide
(15a) and (E)-N-[2-(tert-Butyldimethylsilanyl)oxymethyl-4-oxocy-
clopent-2-enylidenemethyl]-N-(4-methoxyphenyl)-4-methylbenzene-
sulfonamide (15c): Treatment of tert-butyl-(dimethylprop-2-ynyl-
oxy)silane (0.30 g, 2.79 mmol) and N-(4-methoxyphenyl)-4-methyl-
N-(propa-1,2-dienyl)benzenesulfonamide (0.25 g, 0.79 mmol) as de-
scribed in Procedure A for Pauson–Khand intermolecular reac-
H1.22, 2.3 %) ppm. IR (KBr): ν = 2960, 2920, 2860, 1670,
˜
1580 cm–1. C16H17BrO2 (321.21): calcd. C 59.83, H 5.33; found C
59.52, H 5.02.
Data for 17b: 1H NMR (300 MHz, CDCl3): δ = 1.05 (t, J = 7.7 Hz,
3 H), 1.19 (t, J = 7.7 Hz, 3 H), 2.30 (q, J = 7.7 Hz, 2 H), 2.76 (q,
Eur. J. Org. Chem. 2008, 1370–1377
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1375

J. Pérez-Castells et al.
FULL PAPER
J = 7.7 Hz, 2 H), 3.01 (s, 2 H), 6.53 (s, 1 H), 6.95 (d, J = 8.8 Hz, and (propa-1,2-diene-1-sulfinyl)benzene (0.65 g, 3.99 mmol) as de-
2 H), 7.47 (d, J = 9.3 Hz, 2 H) ppm. 13C NMR (75 MHz, CDCl3): scribed in Procedure B for Pauson–Khand intermolecular reactions
δ = 13.5, 13.6, 16.2, 22.4, 37.6, 115.9, 118.1, 118.9, 132.7, 135.3,
145.3, 156.0, 167.2, 204.4 ppm. n.O.e (H6.53 Ǟ H3.01, 4.1%) ppm.
afforded pure 20d (50 mg, 5%) as a yellow solid (m.p. 82–84 °C)
and 20e (53 mg, 5%), also as a yellow solid (m.p. 138–140 °C),
after flash chromatography (hexane and hexane/AcOEt, 1:1). After
treatment as described in Procedure C, the reaction afforded 20d
(68 mg, 15%) and 20e (62 mg, 14%) from sulfinylallene 3k (0.25 g,
1.52 mmol).
IR (KBr): ν = 2960, 2930, 2870, 1690, 1650, 1580 cm–1
.
˜
C16H17BrO2 (321.21): calcd. C 59.83, H 5.33; found C 59.52, H
5.62.
(5E)-5-[(4-Bromophenoxy)methylidene]-2-phenylcyclopent-2-en-1-
one (18d) and (5Z)-5-[(4-Bromophenoxy)methylidene]-2-phenylcy-
clopent-2-en-1-one, (18e): Treatment of ethynylbenzene (0.47 mL,
4.38 mmol) and 1-bromo-4-(propa-1,2-dienyloxy)benzene (0.90 g,
4.25 mmol) as described in Procedure B for Pauson–Khand inter-
molecular reactions afforded pure 18d (0.14 g, 10 %) and 18e
(28 mg, 2%) as yellow waxes after flash chromatography (hexane
and hexane/AcOEt, 2%).
Data for 20d: 1H NMR (300 MHz, CDCl3): δ = 3.28 (d, J = 2.2 Hz,
2 H), 7.35–7.44 (m, 6 H), 7.51–7.54 (m, 2 H), 7.66 (t, J = 2.2 Hz,
1 H), 7.68 (br. s, 1 H), 7.78 (d, J = 7.2 Hz, 2 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 30.9, 127.0, 128.2, 128.4, 128.4, 129.4, 130.8,
131.8, 133.1, 135.7, 141.0, 144.7, 149.1, 191.2 ppm. n.O.e (H7.68
Ǟ
H3.28, 3.7 %). IR (KBr): ν = 1670, 1620, 1590 cm–1. C18H14O2S
˜
(294.37): calcd. C 73.44, H 4.79, S 10.89; found C 73.22, H 5.12, S
10.57.
1
Data for 18d: H NMR (300 MHz, [D6]DMSO): δ = 3.41 (s, 2 H),
1
7.26–7.31 (m, 2 H), 7.36–7.45 (m, 3 H), 7.59–7.63 (m, 2 H), 7.70
(s, 1 H), 7.82–7.85 (m, 2 H), 7.98 (t, J = 2.8 Hz, 1 H) ppm. 13C
NMR (75 MHz, [D6]DMSO): δ = 28.6, 116.4, 118.4, 119.5, 126.8,
128.3, 128.4, 131.9, 132.9, 143.0, 147.0, 151.9, 155.4, 194.2 ppm.
Data for 20e: H NMR (300 MHz, [D6]DMSO): δ = 3.38 (s, 2 H),
7.35–7.46 (m, 7 H), 7.58 (d, J = 7.9 Hz, 2 H), 7.83 (d, J = 7.3 Hz,
2 H), 8.00 (br. s, 1 H) ppm. 13C NMR (75 MHz, [D6]DMSO): δ =
32.4, 126.6, 127.9, 128.3, 128.4, 129.5, 129.7, 129.9, 131.8, 135.7,
137.2, 143.1, 152.5, 193.1 ppm. n.O.e (H3.38 Ǟ H7.35–7.46, 3.1%; Ǟ
n.O.e (H3.41 Ǟ H7.98, 10.0%). IR (film): ν = 1690, 1640, 1580 cm–1.
˜
H8.00, 4.5%). IR (KBr): ν = 1650, 1580 cm–1. C H O S (294.37):
C18H13BrO2 (341.20): calcd. C 63.36, H 3.84; found C 63.75, H
3.56.
˜
18 14
2
calcd. C 73.44, H 4.79, S 10.89; found C 73.78, H 5.01, S 10.50.
Data for 18e: 1H NMR (300 MHz, CDCl3): δ = 3.35 (d, J = 2.7 Hz,
2 H), 6.88 (s, 1 H), 7.07 (d, J = 8.8 Hz, 2 H), 7.35–7.44 (m, 4 H),
7.47–7.52 (m, 2 H), 7.65 (t, J = 2.7 Hz, 1 H), 7.82 (d, J = 8.2 Hz,
1 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 28.8, 117.2, 117.3,
118.4, 118.9, 127.1, 128.4, 131.9, 132.3, 132.9, 147.2, 149.8, 155.7,
195.0 ppm. n.O.e (H3.34 Ǟ H6.88, 4.3%; Ǟ H7.65, 7.0%). IR (film):
(4E)-2,3-Diethyl-4-[(phenylsulfonyl)methylidene]cyclopent-2-en-1-
one (21a) and (5E)-2,3-Diethyl-5-[(phenylsulfonyl)methylene]cy-
clopent-2-en-1-one (21d): Treatment of hex-3-yne (0.08 mL,
0.70 mmol) and (propa-1,2-diene-1-sulfonyl)benzene (124 mg,
0.68 mmol) as described in Procedure B for Pauson–Khand inter-
molecular reactions afforded pure 21a (37 mg, 19 %) and 21d
(27 mg, 14%), as brown waxes after flash chromatography (hexane
and hexane/AcOEt, 25 %). After treatment as described in Pro-
cedure C, the reaction afforded 21a (0.14 g, 35%) and 21d (97 mg,
24%) from sulfonylallene 3l (0.25 g, 1.39 mmol).
ν = 1690, 1640, 1580 cm–1. C H BrO (341.20): calcd. C 63.36, H
˜
18 13
2
3.84; found C 62.88, H 4.20.
(4E)-2,3-Diethyl-4-[(phenylsulfinyl)methylene]cyclopent-2-en-1-one
(19a) and (5E)-2,3-Diethyl-5-[(phenylsulfinyl)methylene]cyclopent-2-
en-1-one (19d): Treatment of hex-3-yne (0.10 mL, 0.90 mmol) and
(propa-1,2-diene-1-sulfinyl)benzene (100 mg, 0.60 mmol) as de-
scribed in Procedure B for Pauson–Khand intermolecular reactions
afforded pure 19a (40 mg, 24%) as a brown solid (m.p. 101–103 °C)
and 19d (23 mg, 14%) as a yellow oil after flash chromatography
(hexane and hexane/AcOEt, 1:1). After treatment as described in
Procedure C, the reaction afforded 19a (0.17 g, 40 %) and 19d
(83 mg, 20%) from sulfinylallene 3k (0.25 g, 1.52 mmol).
Data for 21a: 1H NMR (300 MHz, CDCl3): δ = 1.05 (t, J = 7.7 Hz,
3 H), 1.12 (t, J = 7.7 Hz, 3 H), 2.34 (q, J = 7.7 Hz, 2 H), 2.48 (q,
J = 7.7 Hz, 2 H), 3.39 (d, J = 1.6 Hz, 2 H), 6.45 (t, J = 1.6 Hz, 1 H),
7.55–7.69 (m, 3 H), 7.93–7.96 (m, 2 H) ppm. 13C NMR (75 MHz,
CDCl3): δ = 12.8, 13.2, 17.2, 19.1, 37.6, 120.9, 127.4, 129.4, 133.6,
141.3, 149.8, 150.9, 164.0, 202.1 ppm. n.O.e. (H6.45 Ǟ H2.47, 5.9%;
Ǟ H1.18, 3.0%; Ǟ H7.95, 2.4%), (H3.40 Ǟ H7.95, 2.8%). IR (film):
ν = 2980, 2960, 2890, 1710, 1600 cm–1. C H O S (290.38): calcd.
˜
16 18
3
Data for 19a: 1H NMR (300 MHz, CDCl3): δ = 0.99–1.08 (m, 6
H), 2.27–2.34 (m, 2 H), 2.41–2.46 (m, 2 H), 3.21 (d, J = 20.9 Hz,
1 H), 3.43 (d, J = 20.9 Hz, 1 H), 6.39 (s, 1 H), 7.48–7.51 (m, 3 H),
7.60–7.62 (m, 2 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 12.8,
13.2, 17.0, 19.0, 37.5, 124.0, 127.1, 129.4, 131.0, 143.8, 145.8, 150.0,
164.6, 201.8 ppm. n.O.e (H6.43 Ǟ H2.49, 5.7%; Ǟ H1.10, 2.6%). IR
C 66.18, H 6.25, S 11.04; found C 65.95, H 6.02, S 11.32.
Data for 21d: 1H NMR (300 MHz, CDCl3): δ = 0.99 (t, J = 7.7 Hz,
3 H), 1.21 (t, J = 7.7 Hz, 3 H), 2.28 (q, J = 7.7 Hz, 2 H), 2.55 (q,
J = 7.7 Hz, 2 H), 3.62 (s, 2 H), 6.94 (s, 1 H), 7.56–7.69 (m, 3 H),
7.94 (d, J = 7.7 Hz, 2 H) ppm. 13C NMR (75 MHz, CDCl3): δ =
11.8, 12.9, 16.5, 23.8, 33.0, 127.7, 127.8, 129.4, 134.0, 140.2, 142.5,
(KBr): ν = 2960, 2920, 2860, 1700, 1600 cm–1. C H O S (274.38):
˜
16 18
2
143.4, 171.8, 194.6 ppm. n.O.e (H3.62 Ǟ H2.56, 1.9 %; Ǟ H1.20
,
calcd. C 70.04, H 6.61, S 11.69; found C 70.23, H 6.94, S 11.44.
2.1 %). IR (film): ν = 2980, 2920, 2880, 1700 cm–1. C16H18O3S
˜
Data for 19d: 1H NMR (300 MHz, CDCl3): δ = 1.00 (t, J = 7.7 Hz,
3 H), 1.20 (t, J = 7.7 Hz, 3 H), 2.27 (q, J = 7.7 Hz, 2 H), 2.54 (q,
J = 7.7 Hz, 2 H), 3.49 (d, J = 22.0 Hz, 1 H), 3.69 (d, J = 22.0 Hz,
1 H), 6.93 (d, J = 1.6 Hz, 1 H), 7.52–7.54 (m, 3 H), 7.65–7.69 (m,
2 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 11.9, 13.0, 16.5, 23.7,
32.4, 124.5, 128.2, 129.6, 131.5, 134.3, 140.3, 142.5, 170.8,
(290.38): calcd. C 66.18, H 6.25, S 11.04; found C 65.98, H 5.96, S
10.69.
N-[(E)-(2,3-Diethyl-4-oxocyclopent-2-en-1-ylidene)methyl]-N-(2-eth-
ynylphenyl)acetamide (22a): Treatment of hex-3-yne (0.12 g,
1.52 mmol) and N-(2-ethynylphenyl)-N-propadienylacetamide
(0.20 g, 1.01 mmol) as described in Procedure B for Pauson–Khand
intermolecular reactions afforded pure 22a (46 mg, 15%) as a yel-
low oil after flash chromatography (hexane/AcOEt, 4:1). After
treatment as described in Procedure C, the reaction afforded 22a
(0.17 g, 45%) from allenamide 3f (0.25 g, 1.27 mmol). 1H NMR
194.4 ppm. IR (film): ν = 2960, 2920, 2880, 1770, 1690, 1610 cm–1.
˜
C16H18O2S (274.38): calcd. C 70.04, H 6.61, S 11.69; found C 69.81,
H 6.72, S 11.32.
(5E)-2-Phenyl-5-[(phenylsulfinyl)methylene]cyclopent-2-en-1-one
(20d) and (5Z)-2-Phenyl-5-[(phenylsulfinyl)methylidene]cyclopent-2- (300 MHz, CDCl3): δ = 0.97 (t, J = 7.3 Hz, 3 H), 1.21 (t, J =
en-1-one (20e): Treatment of ethynylbenzene (0.47 mL, 4.38 mmol) 7.3 Hz, 3 H), 1.84 (d, J = 20.7 Hz, 1 H), 1.95 (s, 3 H), 2.10 (d, J =
1376
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 1370–1377

Pauson–Khand Reactions of Functionalized Allenes
20.7 Hz, 1 H), 2.20 (q, J = 7.3 Hz, 2 H), 2.59 (q, J = 7.3 Hz, 2 H),
3.26 (s, 1 H), 7.26–7.29 (m, 1 H), 7.43–7.47 (m, 2 H), 7.61 (s, 1 H), [1]
7.62–7.64 (m, 1 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 13.3,
14.0, 16.5, 19.5, 22.4, 36.6, 78.8, 83.7, 120.3, 121.0, 123.0, 129.3,
Recent reviews on the Pauson–Khand reaction: a) J. Blanco-
Urgoiti, L. Anorbe, L. Perez-Serrano, G. Dominguez, J. Perez-
Castells, Chem. Soc. Rev. 2004, 33, 32–42; b) T. Sugihara, M.
Yamaguchi, M. Nishizawa, Chem. Eur. J. 2001, 7, 1589–1595;
c) K. M. Brummond, J. L. Kent, Tetrahedron 2000, 56, 3263–
3283.
129.5, 130.4, 134.0, 141.0, 142.4, 170.0, 202.3 ppm. n.O.e (H7.61
Ǟ
.
H1.84, 0.0 %; Ǟ H2.10, 0.0 %). IR (KBr): ν = 1690, 1630 cm–1
˜
C20H21NO2 (307.39): calcd. C 78.15, H 6.89, N 4.56; found C
77.98, H 7.18, N 4.40.
[2] Review on the intermolecular PKR: S. E. Gibson, N. Mainolfi,
Angew. Chem. Int. Ed. 2005, 44, 3022–3037.
[3] W. J. Kerr, M. McLaughlin, P. L. Pauson, S. M. Robertson, J.
Organomet. Chem. 2001, 630, 104–117.
[4] M. Rodriguez-Rivero, J. C. de la Rosa, J. C. Carretero, J. Am.
Chem. Soc. 2003, 125, 14992–14993.
[5] J. F. Reichwein, S. T. Iacono, B. L. Pagenkopf, Tetrahedron
2002, 58, 3813–3822.
5-[(4-Methylphenyl)sulfonyl]-3,5-dihydro-2H-cyclopenta[c]quinolin-
2-one (23): Treatment of N-(2-ethynylphenyl)-4-methyl-N-(propa-
1,2-dienyl)benzenesulfonamide (100 mg, 0.32 mmol) with Mo-
(MeCN)3(CO)3 by the general procedure for intramolecular Pau-
son–Khand reactions afforded pure 23 (46 mg, 43%) as a yellow
solid (dec. 248 °C) after flash chromatography (hexane/AcOEt,
[6] K. Itami, K. Mitsudo, J. Yoshida, Angew. Chem. Int. Ed. 2002,
1
1:1). H NMR (300 MHz, CDCl3): δ = 2.40 (s, 3 H), 3.24 (s, 2 H),
41, 3481–3484.
6.16 (s, 1 H), 7.28–7.34 (m, 3 H), 7.48 (t, J = 7.3 Hz, 1 H), 7.71–
7.75 (m, 4 H), 8.18 (d, J = 8.5 Hz, 1 H) ppm. 13C NMR (75 MHz,
CDCl3): δ = 21.7, 38.3, 114.2, 119.1, 119.2, 120.6, 121.8, 125.7,
127.3, 127.5, 130.2, 132.0, 134.2, 134.7, 145.8, 160.3, 203.3 ppm.
[7] F. Robert, A. Milet, Y. Gimbert, D. Konya, A. E. Greene, J.
Am. Chem. Soc. 2001, 123, 5396–5400.
[8] a) Modern Allene Chemistry (Eds.: N. Krause, A. S. K.
Hashmi), Wiley-VCH, Weinheim, 2004; b) R. Zimmer, C. U.
Dinesh, E. Nandanan, F. A. Khan, Chem. Rev. 2000, 100,
3067–3126; c) J. A. Marshall, Chem. Rev. 2000, 100, 3163–3186;
d) A. Hoffmann-Röder, N. Krause, Angew. Chem. Int. Ed.
2002, 41, 2933–2935; Angew. Chem. 2002, 114, 3057–3059; e)
A. Hoffmann-Röder, N. Krause, Angew. Chem. Int. Ed. 2004,
43, 1196–1216; Angew. Chem. 2004, 116, 1216–1236; f) N.
Krause, A. Hoffmann-Röder, Tetrahedron 2004, 60, 11671–
11694; g) S. Ma, Chem. Rev. 2005, 105, 2829–2871.
[9] Review on the allenic PKR: B. Alcaide, P. Almendros, Eur. J.
Org. Chem. 2004, 3377–3383.
[10] a) F. Antras, M. Ahmar, B. Cazes, Tetrahedron Lett. 2001, 42,
8153–8156; b) F. Antras, M. Ahmar, B. Cazes, Tetrahedron
Lett. 2001, 42, 8157–8160; c) M. Ahmar, O. Chabanis, J.
Gauthier, B. Cazes, Tetrahedron Lett. 1997, 38, 5277–5280; d)
M. Ahmar, F. Antras, B. Cazes, Tetrahedron Lett. 1995, 36,
4417–4420.
IR (KBr): ν = 3080, 2940, 1630, 1600, 1580 cm–1. C H NO S
˜
19 15
3
(337.39): calcd. C 67.64, H 4.48, N 4.15, S 9.50; found C 67.29, H
4.75, N 3.88, S 9.78.
3H-Cyclopenta[c]chromen-2-one (24) and 1-Methylene-1,8a-dihydro-
8-oxacyclopenta[a]inden-2-one (25): Treatment of 1-ethynyl-2-
(propa-1,2-dien-1-yloxy)benzene (156 mg) with Mo(CO)6 by the
general procedure for intramolecular Pauson–Khand reactions af-
forded pure 24 (45 mg, 25%) as a colorless oil and 25 (77 mg, 38%)
as a yellow solid (m.p. 79–81 °C) after flash chromatography (hex-
ane/AcOEt, 1:1).
1
Data for 24: H NMR (300 MHz, CDCl3): δ = 3.16 (s, 2 H), 6.14
(s, 1 H), 7.13 (s, 1 H), 7.32 (t, J = 7.7 Hz, 1 H), 7.56 (t, J = 7.1 Hz,
1 H), 7.72 (d, J = 7.7 Hz, 2 H) ppm. 13C NMR (75 MHz, CDCl3):
δ = 36.5, 113.1, 116.9, 118.2, 119.9, 124.9, 126.5, 132.8, 136.8,
[11] L. Añorbe, A. Poblador, G. Domínguez, J. Pérez-Castells, Tet-
rahedron Lett. 2004, 45, 4441–4444.
152.5, 159.1, 203.2 ppm. IR (film): ν = 1680, 1650, 1610, 1550 cm–1.
˜
[12] This behavior of tosylamides has been described earlier: L. J.
van Boxtel, S. Körbe, M. Noltemeyer, A. de Meijere, Eur. J.
Org. Chem. 2001, 2283–2292.
[13] a) P. Hamel, J. Org. Chem. 2002, 67, 2854–2858; b) S. Ma, H.
Ren, Q. Wei, J. Am. Chem. Soc. 2003, 125, 4817–4830.
[14] A. Padwa, M. Meske, S. S. Murphree, S. H. Watterson, Z. Ni,
J. Am. Chem. Soc. 1995, 117, 7071–7080.
[15] L. Pérez-Serrano, J. Blanco-Urgoiti, L. Casarrubios, G.
Domínguez, J. Pérez-Castells, J. Org. Chem. 2000, 65, 3513–
3519, and references therein.
[16] The signal of the CH2 in the cyclopentenone appears at δ =
38 ppm, which agrees with calculated values for compound 5a.
See experimental for n. O. e. data.
[17] Review on PKRs of electron-deficient alkenes: M. R. Rivero,
J. Adrio, J. C. Carretero, Eur. J. Org. Chem. 2002, 2881–2889.
[18] J. Adrio, J. C. Carretero, J. Am. Chem. Soc. 2007, 129, 778–
779.
[19] a) K. M. Brummond, H. Wan, Tetrahedron Lett. 1998, 39, 931–
934; b) J. L. Kent, H. Wan, K. M. Brummond, Tetrahedron
Lett. 1995, 36, 2407–2410; c) K. M. Brummond, H. Wan, J. L.
Kent, J. Org. Chem. 1998, 63, 6535–6545.
C12H8O2 (184.19): calcd. C 78.25, H 4.38; found C 78.69, H 4.15.
Data for 25: 1H NMR (300 MHz, CDCl3): δ = 5.73 (d, J = 1.6 Hz,
1 H), 5.93–5.95 (m, 1 H), 6.18 (d, J = 1.6 Hz, 1 H), 6.38 (d, J =
2.7 Hz, 1 H), 7.03–7.11 (m, 2 H), 7.46 (td, J1 = 1.6, J2 = 7.2 Hz, 1
H), 7.60 (dd, J1 = 1.1, J2 = 7.7 Hz, 1 H) ppm. 13C NMR (75 MHz,
CDCl3): δ = 87.1, 112.6, 116.0, 121.4, 122.6, 122.6, 125.2, 134.9,
144.0, 165.5, 173.4, 193.4 ppm. IR (KBr): ν = 3080, 1690, 1610,
˜
1570 cm–1. C12H8O2 (184.19): calcd. C 78.25, H 4.38; found C
77.89, H 4.65.
Supporting Information (see also the footnote on the first page of
this article): Experimental procedures and data for the synthesis of
starting materials.
Acknowledgments
This work was supported by the Spanish Ministerio de Educación
y Ciencia (MEC) (grant No. CTQ2006/00601). A. P. and A. G.-
G. acknowledge fellowships from the Fundación Universitaria San
Pablo-CEU.
Received: November 5, 2007
Published Online: January 15, 2008
Eur. J. Org. Chem. 2008, 1370–1377
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1377