Behaviour of monocomplexed 1,4-diynes in the Khand reaction and use of ethylene equivalent techniques in a convenient route to tritium-labelled methyl jasmonate

Article abstract of DOI:10.1016/S0022-328X(01)00890-7

1,2-Complexed hexacarbonyl(hepta-1,4-diyne)dicobalt, obtained from hexacarbonyl(propargyl acetate)dicobalt with tri-1-butynylaluminium, has been converted, by selective Khand annulation of the complexed triple bond with vinyl benzoate, to 2-pent-2-yn-1-ylcyclopent-2-en-1-one. By use of standard procedures this alkynyl cyclopentenone has been transformed into methyl jasmonate, allowing replacement of the final hydrogenation step by tritiation to produce the labelled analogue. Two alternative approaches to the intermediate pentynylcyclopentenone were examined and shown to be unsuccessful.

Full text of DOI:10.1016/S0022-328X(01)00890-7

Journal of Organometallic Chemistry 630 (2001) 118–124
www.elsevier.com/locate/jorganchem
Behaviour of monocomplexed 1,4-diynes in the Khand reaction
and use of ethylene equivalent techniques in a convenient route to
tritium-labelled methyl jasmonate
William J. Kerr *, Mark McLaughlin, Peter L. Pauson
Department of Pure and Applied Chemistry, Uni6ersity of Strathclyde, Thomas Graham Building, 295 Cathedral Street, Glasgow G1 1XL,
Scotland, UK
Received 18 January 2001; received in revised form 27 March 2001; accepted 27 March 2001
Abstract
1,2-Complexed hexacarbonyl(hepta-1,4-diyne)dicobalt, obtained from hexacarbonyl(propargyl acetate)dicobalt with tri-1-bu-
tynylaluminium, has been converted, by selective Khand annulation of the complexed triple bond with vinyl benzoate, to
2-pent-2-yn-1-ylcyclopent-2-en-1-one. By use of standard procedures this alkynyl cyclopentenone has been transformed into
methyl jasmonate, allowing replacement of the final hydrogenation step by tritiation to produce the labelled analogue. Two
alternative approaches to the intermediate pentynylcyclopentenone were examined and shown to be unsuccessful. © 2001 Elsevier
Science B.V. All rights reserved.
Keywords: Khand reaction; Methyl dehydrojasmonate; Methyl jasmonate; Tritium; Vinyl esters; Ethylene equivalent
1. Introduction
strating the effectiveness of the Khand reaction as the
key step in the synthesis of both jasmonate itself and a
range of analogues [1]. When, therefore, Pharmaceuti-
cal Biologists at the Universita¨t Mu¨nchen [2] and the
Universita¨t Bochum [3] enquired whether we could
extend this work to provide a source of tritium-labelled
jasmonate, we readily agreed to approach the synthesis
of the desired target as described herein.
The growing interest in the diverse biological effects
of methyl jasmonate, notably as a plant growth regula-
tor and phytoalexin, led to our earlier work demon-
2. Results and discussion
2.1. The diyne pathway
We argued that if we approached methyl jasmonate
1a, viz. its ditritiated form 1b, via the didehydro com-
pound 2a we would gain the advantage of (i) placing
the labels on sp2 carbons from which they would be less
likely to be lost by exchange, and (ii) adding the
radioactive label as late as possible in the synthetic
sequence. Moreover, we would have the opportunity of
studying a feature of the Khand reaction which had not
been previously examined: the behaviour of a diyne
complexed specifically on one triple bond. More specifi-
Scheme 1. Retrosynthetic analysis for the preparation of methyl
jasmonates.
* Corresponding author. Tel.: +44-141-5482959; fax: +44-141-
5484246.
E-mail address: cbas69@strath.ac.uk (W.J. Kerr).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)00890-7

W.J. Kerr et al. / Journal of Organometallic Chemistry 630 (2001) 118–124
119
equivalent technique [4,7]. Nevertheless, it should be
noted that this yield was again better than those ob-
tained when employing ethylene gas and trimethy-
lamine N-oxide dihydrate (TMANO·2H2O), either
under atmospheric (1% yield) or 25 atm. pressure (11%
yield). In order to further probe the reactivity of 4a, we
also tested the behaviour of this monocomplexed diyne
with a more reactive alkene, norbornene. The forma-
tion of the expected tricyclic product 6 in only 30%
yield from this alkene undoubtedly reflects the compli-
cations introduced by having a diyne system. These
were further emphasised when reaction of the complex
4a with ethylene gas was conducted under 30 atm.
pressure with dimethyl sulfoxide as promoter [8]. After
a 48 h reaction time at 25 °C, this gave the cyclopen-
tenone 3a in 10% yield together with its cobalt complex
7 (the product of a metal exchange process) in 12%
yield and unreacted complex 4a (53% recovery). Repeti-
tion at 40 °C for 60 h also gave 3a (12% yield) but now
accompanied by the diketone 8a (or its regioisomer 8b),
resulting from a second Khand reaction, as the major
product (23% yield). Therefore, following this series of
studies and despite the relatively low yield, it can be
seen that the new ethylene equivalent protocol with
vinyl benzoate provided the optimum Khand method
for the formation of the desired cyclopentenone 3a.
Scheme 2. Preparation of cyclopentenones 3b and 3a.
Scheme 3. Completion of methyl jasmonate synthesis.
cally, retrosynthesis from 2a leads back to the alkyne
3a, the expected product of a Khand reaction between
1,2-complexed hepta-1,4-diyne 4a and ethene (Scheme
1). Furthermore, this strategy would thus also allow us
to compare another ethene reaction with the use of our
novel vinyl ester ethylene equivalent technique as de-
scribed in the preceding paper [4].
Diyne complexes of the required class had previously
been synthesised by Padmanabhan and Nicholas [5]
from the propynyl acetate complex 5a by reaction with
a trialkynylaluminium. Since 1-butyne, required in our
case, is not widely available, we first tested the reaction
sequence using 1-heptyne (Scheme 2). This was treated
successively with n-butyllithium and aluminium chlo-
ride to generate tri-1-heptynylaluminium and then with
hexacarbonyl(propargyl acetate)dicobalt 5a (as an in
situ source of the corresponding propargyl cation) to
give the mono-complexed diyne 4b in 85% yield. In due
course, N-methylmorpholine N-oxide monohydrate
(NMO·H2O) promoted reaction of this complex with
vinyl benzoate then produced the desired cyclopen-
tenone 3b, albeit in a low 27% yield. In turn, this
sequence of reactions was then repeated with 1-butyne
[6] to give first the diyne complex 4a, in a good 75%
yield, and then the cyclopentenone 3a, required for the
jasmonate synthesis, in 20% yield.
For the final steps of our route towards the methyl
jasmonates (Scheme 3), the Michael-type addition of
the ketene acetal, Me3SiCHꢀC(OMe)OSiMe3 [9] to cy-
clopentenone 3a followed precedent [1] and gave the
silyl-substituted ester 2b efficiently (90%) [10]. Desilyla-
tion of this intermediate to yield methyl dehydrojas-
monate 2a occurred nearly quantitatively on treatment
with a catalytic quantity of potassium carbonate in
methanol. This method, which had previously been
used with silylalkynes [11], seems more convenient and
even more efficient than the previously used fluoride
treatment [1,9,10]. Finally, hydrogenation of this
product 2a over a Lindlar-type catalyst with either
dihydrogen (1H2) or ditritium (3H2) [12] gave cis-methyl
jasmonate 1a, viz. 1b, again almost quantitatively.
2.2. Alternati6e approaches to the jasmonate skeleton
The yield using vinyl benzoate with the monocom-
plexed diyne 4a was disappointing, especially based on
the efficiency normally achieved with the ethylene
The lower efficiency of the Khand reaction step when
using the diyne complex 4a led us to consider two

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W.J. Kerr et al. / Journal of Organometallic Chemistry 630 (2001) 118–124
alternative approaches to the pent-2-yn-1-ylcyclopen-
tenone (3a). The chemistry completed along each of the
routes will now be described briefly. In the first of these
it was planned to utilise the alcohol 9a [4a] and, follow-
ing oxidation to the corresponding aldehyde 9b, trans-
formation into the alkyne 9c would require alkylation
as a final step on the way to intermediate 3a. In the
second route, the hydroxyl functionality of the lower
homologous alcohol 9d (obtained from Khand cyclisa-
tion of 5b followed by deprotection [4a]) would be
converted to a better leaving group with a view to
displacement by the anion of 1-butyne.
this new procedure and has been shown to provide a
short and simple method allowing rapid access to the
(labelled) jasmone skeleton.
4. Experimental
4.1. General remarks
See the preceding paper [4a].
4.2. Hexacarbonyl[v-[(2,3-p:2,3-p)prop-2-yn-
1-acetate]]dicobalt-(CoꢁCo) (5a) [5]
Acetic anhydride (0.18 g, 1.80 mmol) was added to a
solution of hexacarbonyl[m-[(2,3-h:2,3-h)prop-2-yn-1-
ol]]dicobalt-(CoꢁCo) [16] (0.56 g, 1.64 mmol), Et3N
(0.18 g, 1.80 mmol) and N,N-dimethylaminopyridine
(0.01 g, 0.08 mmol) in CH2Cl2 (20 ml) at 25 °C. The
mixture was stirred for 30 min before it was filtered
through a pad of silica using 10% Et2O in light
petroleum as the eluent. The filtrate was evaporated
under reduced pressure to give hexacarbonyl[m-[(2,3-
The alcohol 9a was readily formed from but-1-yn-4-
ol via its complex 5c or in better overall yield via the
corresponding tetrahydropyranyl ethers 5d and 9e [4a].
The tetrahydropyranyl-protected cyclopentenone 9e
was readily deprotected by treatment with catalytic
pyridinium para-toluenesulfonate (PPTS) in methanol
to afford the alcohol 9a in 95% yield [4a]. In turn,
alcohol 9a could be oxidised to the rather unstable
aldehyde 9b in 50% yield by treatment with the Dess–
Martin periodinane [13]. However, attempts to alkyny-
late this aldehyde under both Ramirez–Corey [14] and
Ohira–Bestmann [15] conditions failed.
As detailed in the preceding paper [4a], the alcohol
9d was readily formed by PPTS-mediated deprotection
of the tetrahydropyranyl derivative 9f in 99% yield. In
order to prepare for the planned nucleophilic displace-
ment by 1-lithiobut-1-yne, the alcohol 9d was converted
into unstable mesylate 9g (90% yield), which could be
further transformed into the equally difficult to handle
iodide 9h (90% yield). Attempts to react either of these
intermediates with the aforementioned nucleophile re-
sulted in decomposition. At this stage, work on these
two alternative routes to intermediate 3a was discontin-
ued since neither offered any potential increase in effi-
ciency over our established pathway (vide supra) to the
desired methyl jasmonates.
h:2,3-h)prop-2-yn-1-acetate]]dicobalt-(CoꢁCo)
(5a)
(0.63 g, 99%) as a red oil. 1H-NMR (400 MHz, CDCl3):
l=2.14 (3H, s, CH3CO), 5.28 (2H, s, CH2), 6.06 (1H,
s, ꢂCH). wmax (cm−1, CH2Cl2): 2096, 2060, 2013, 1724.
4.3. Hexacarbonyl[v-[(1,2-p:1,2-p)deca-1,4-diyne]]-
dicobalt-(CoꢁCo) (4b)
A solution of n-butyllithium in hexanes (2.5 M, 5.20
ml, 13.0 mmol) was added dropwise to a stirred solu-
tion of hept-1-yne (1.20 g, 12.5 mmol) in dry hexanes
(50 ml) at 0 °C. An immediate precipitation of the
lithium acetylide was observed. This white slurry was
stirred for 30 min before aluminium trichloride (0.55 g,
4.17 mmol) was added as a finely ground solid. The
resulting brown slurry was stirred for a further 1 h
before the solvent was evaporated under reduced pres-
sure and replaced with CH2Cl2 (60 ml). This mixture
was then transferred via cannula to a stirred solution of
hexacarbonyl[m-[(2,3-h:2,3-h)prop-2-yn-1-acetate]]-
dicobalt-(CoꢁCo) (5a) (0.50 g, 1.30 mmol) in CH2Cl2
(80 ml) at 0 °C. The mixture was stirred for 1 h before
sodium sulfate (10.0 g) was added and the slurry was
then filtered through a pad of kieselguhr. The filtrate
was evaporated under reduced pressure to leave a dark
oil, which was purified by repeated (×3) chromatogra-
phy through short plugs of silica using light petroleum
as the eluent to give hexacarbonyl[v-[(1,2-p:1,2-p)deca-
1,4-diyne]]dicobalt-(CoꢁCo) (4b) (0.46 g, 85%) as a red
oil. 1H-NMR (400 MHz, CDCl3): l=0.92 (3H, t,
J=10.6 Hz, CH3), 1.23–1.42 (4H, m, CH2CH2CH3),
1.50 (2H, m, ꢂCCH2CH2), 2.16 (2H, m, ꢂCCH2CH2)
3.71 (2H, s, ꢂCCH2Cꢂ), 6.06 (1H, s, HCꢂ). 13C-NMR
3. Conclusions
We have now shown that complexation of one triple
bond of a diyne allows selective Khand reactions to be
preformed on that bond. On the other hand, the Khand
cyclisation yields which have been obtained are low
and, in some cases, the reactions are not clean.
Nonetheless, with these monocomplexed diynes our
novel vinyl ester ethylene equivalent technique [4] pro-
vides the optimum method for the key Khand annula-
tions. This further illustrates the practical advantage of

W.J. Kerr et al. / Journal of Organometallic Chemistry 630 (2001) 118–124
121
4.6. Reactions of hexacarbonyl[v-[(1,2-p:1,2-p)-
hepta-1,4-diyne]]dicobalt-(CoꢁCo) (4a)
(100 MHz, CDCl3): l=14.1, 18.8, 22.4, 24.7, 28.4,
31.3, 72.9 (uncomplexed alkyne-C), 82.8 (uncomplexed
alkyne-C), 94.6 (complexed alkyne-C), 130.5 (com-
plexed alkyne-C) and 199.8 (CO). wmax (cm−1, CH2Cl2):
2097, 2053, and 2002.
4.6.1. Reaction with 6inyl benzoate; formation of
2-(pent-2-yn-1-yl)cyclopent-2-en-1-one (3a) [17]
A solution of N-methylmorpholine N-oxide monohy-
drate (18.0 g, 0.13 mol) in CH2Cl2 (500 ml) was added
over a 2 h period (dropping funnel) to a stirred solution
of hexacarbonyl[m-[(1,2-h:1,2-h)hepta-1,4-diyne]]dico-
balt-(CoꢁCo) (4a) (5.00 g, 13.2 mmol) in vinyl benzoate
(70 ml) at 0 °C. The mixture was stirred for 16 h before
it was filtered through a pad of silica using CH2Cl2 as
the eluent. The filtrate was evaporated under reduced
pressure to leave a crude residue, which was purified by
column chromatography on silica using 10% Et2O in
light petroleum as the eluent to give 2-(pent-2-yn-1-
yl)cyclopent-2-en-1-one (3a) (0.39 g, 20%) as a pale
4.4. 2-(Oct-2-yn-1-yl)cyclopent-2-en-1-one (3b)
A solution of N-methylmorpholine N-oxide monohy-
drate (0.93 g, 6.89 mmol) in CH2Cl2 (10 ml) was added
over a 2 h period (syringe pump) to a stirred solution of
hexacarbonyl[m - [(1,2 - h:1,2 - h)deca - 1,4 - diyne]]dico-
balt-(CoꢁCo) (4b) (0.29 g, 0.69 mmol) in vinyl benzoate
(15 ml) at 0 °C. The mixture was stirred for 16 h before
it was filtered through a pad of silica using CH2Cl2 as
the eluent. The filtrate was evaporated under reduced
pressure to leave a crude residue, which was purified by
column chromatography on silica using 10% Et2O in
light petroleum as the eluent to give 2-(oct-2-yn-1-
yl)cyclopent-2-en-1-one (3b) (35.0 mg, 27%) as a pale
1
yellow oil. H-NMR (400 MHz, CDCl3): l=1.14 (3H,
t, J=7.5 Hz, CH3), 2.19 (2H, m, CH2CH3), 2.44 (2H,
m, CH2CO), 2.60 (2H, m, CH2CHꢀ), 3.02 (2H, m,
CH2Cꢂ), 7.60 (1H, m, CHꢀ). 13C-NMR (100 MHz,
CDCl3): l=12.6, 14.4, 15.8, 26.6, 35.1, 75.3 (alkyne-C),
84.2 (alkyne-C), 142.8 (ꢀC), 159.3 (HCꢀ), 208.4 (CO).
wmax (cm−1, CH2Cl2) 1702, 1638. HRMS: m/z: Found:
147.08003. Calc. for C10H11O [M+−1]: 147.08099.
1
yellow oil. H-NMR (400 MHz, CDCl3): l=0.92 (3H,
t, J=7.1 Hz, CH3), 1.21–1.39 (4H, m, CH2CH2), 1.53
(2H, m, CH2), 2.19 (2H, m, ꢂCCH2), 2.46 (2H, m,
CH2CO), 2.61 (2H, m, CH2CHꢀ), 3.04 (2H, m,
ꢀCCH2Cꢂ), 7.60 (1H, m, CHꢀ). 13C-NMR (100 MHz,
CDCl3): l=14.2, 15.9, 18.9, 22.4, 26.6, 28.9, 31.3, 35.2,
75.9 (alkyne-C), 83.0 (alkyne-C), 143.0 (ꢀC), 159.3
(HCꢀ), 208.4 (CO). wmax (cm−1, CH2Cl2): 2206, 1702,
1612. HRMS: m/z: Found: 190.13652. Calc. for
C13H18O [M+]: 190.13577.
4.6.2. Reaction with 6inyl acetate; formation of
5-acetoxy-2-(pent-2-yn-1-yl)cyclopent-2-en-1-one
A solution of N-methylmorpholine N-oxide monohy-
drate (1.40 g, 10.4 mmol) in CH2Cl2 (20 ml) was added
over a 4 h period to a stirred solution of hexa-
carbonyl[m - [(1,2 - h:1,2 - h)hepta - 1,4 - diyne]]dicobalt-
(CoꢁCo) (4a) (0.38 g, 1.00 mmol) in vinyl acetate (20
ml) at −40 °C. The mixture was stirred for a further
16 h before it was filtered through a pad of silica using
CH2Cl2 as the eluent. The filtrate was evaporated under
reduced pressure to leave a crude residue, which was
purified by column chromatography on silica using a
10–40% Et2O in light petroleum gradient as the eluent
to give 5-acetoxy-2-(pent-2-yn-1-yl)cyclopent-2-en-1-
4.5. Hexacarbonyl[v-[(1,2-p:1,2-p)hepta-1,4-diyne]]-
dicobalt-(CoꢁCo) (4a)
The procedure detailed at Experiment 4.3 was fol-
lowed with the exception that, at the outset, 1-butyne
gas (15.0 g) was slowly bubbled into a stirred solution
of n-butyllithium (2.5 M (in hexanes), 100 ml, 0.25 mol)
in hexanes (250 ml) at −70 °C. The mixture was then
allowed to warm to 0 °C after precipitation of the
lithium acetylide was observed. Aluminium trichloride
(11.1 g, 83.4 mmol), hexacarbonyl[m-[(2,3-h:2,3-h)prop-
2-yn-1-acetate]]dicobalt-(CoꢁCo) (5a) (15.0 g, 39.1
mmol), and CH2Cl2 (250 ml and 300 ml) were used to
give, after purification, hexacarbonyl[v-[(1,2-p:1,2-
p)hepta-1,4-diyne]]dicobalt-(CoꢁCo) (4a) (11.0 g, 75%)
as a red oil. 1H-NMR (400 MHz, CDCl3): l=1.14
(3H, t, J=7.5 Hz, CH3), 2.18 (2H, q, J=7.5 Hz,
CH2CH3), 3.71 (2H, s, ꢂCCH2Cꢂ), 6.02 (1H, s, HCꢂ).
13C-NMR (100 MHz, CDCl3): l=12.5, 13.8, 24.7, 72.9
(uncomplexed alkyne-C), 84.0 (uncomplexed alkyne-C),
94.5 (complexed alkyne-C), 125.0 (complexed alkyne-
C), 199.3 (CO). wmax (cm−1, CH2Cl2): 2098, 2047, 2028.
HRMS: m/z: Found: 349.90357. Calc. for C12H8Co2O5
[M+−CO]: 349.90507.
1
one (0.03 g, 13%) as a pale yellow oil. H-NMR (400
MHz, CDCl3): l=1.16 (3H, t, J=7.5 Hz, CH3CH2),
2.14 (3H, s, CH3CO), 2.23 (2H, m, CH3CH2), 2.52 (1H,
m, CH2CHꢀ), 3.09 (2H, m, ꢂCCH2Cꢀ), 3.14 (1H, m,
CH2CHꢀ), 5.18 (1H, m, CHO), 7.54 (1H, m, HCꢀ).
13C-NMR (100 MHz, CDCl3): l=12.6, 14.3, 16.1,
20.9, 33.8, 72.6 (CHO), 74.3 (alkyne-C), 84.9 (alkyne-
C), 141.3 (CH2Cꢀ), 155.8 (HCꢀ), 170.5 (CO2), 202.0
(CO). wmax (cm−1, CH2Cl2): 2190, 1740, 1710. HRMS:
m/z: Found: 206.09486. Calc. for C12H14O3 [M+]:
206.09429.
4.6.3. Reaction with ethylene gas at atmospheric pressure
A solution of trimethylamine N-oxide dihydrate (1.60
g, 14.4 mmol) in MeOH (9 ml) was added over a 90

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W.J. Kerr et al. / Journal of Organometallic Chemistry 630 (2001) 118–124
4.6.6. Reaction with ethylene gas at 30 atm pressure
and with Me2SO as promoter
min period to a stirred solution of hexacarbonyl[m-[(1,2-
h:1,2-h)hepta-1,4-diyne]]dicobalt-(CoꢁCo) (4a) (0.60 g,
1.59 mmol) in toluene (9 ml), all under 1 atm of
ethylene at 25 °C. The mixture was stirred for 16 h
before it was filtered through a pad of silica using
CH2Cl2 as the eluent. The filtrate was evaporated under
reduced pressure to leave a crude residue, which was
purified by column chromatography on silica using 10%
Et2O in light petroleum as the eluent to give 2-(pent-2-
yn-1-yl)cyclopent-2-en-1-one (3a) (3.0 mg, 1%) as a pale
yellow oil. Analytical data were as given above.
4.6.6.1. Room temperature reaction. A mixture of
dimethyl sulfoxide (1 ml), hexacarbonyl[m-[(1,2-h:1,2-
h)hepta-1,4-diyne]]dicobalt-(CoꢁCo) (4a) (0.79 g, 2.09
mmol) and benzene (30 ml) in a 50 ml autoclave vessel
was placed under 30 atm. pressure of ethylene gas and
agitated for 48 h at 25 °C. The mixture was then
filtered through a pad of silica using Et2O as the eluent.
The filtrate was evaporated under reduced pressure to
leave a crude residue, which was purified by column
chromatography on silica using a 10–50% Et2O in light
petroleum gradient as the eluent to give hexacar-
bonyl[v-[(2,3-p:2,3-p)-1-[5-oxocyclopent-1-en-1-yl]-
pent-2-yne]]dicobalt-(CoꢁCo) (7) (0.11 g, 12%) as a red
oil. 1H-NMR (400 MHz, CDCl3): l=1.28 (3H, t,
J=7.3 Hz, CH3), 2.42 (2H, m, CH2CO), 2.62 (2H, m,
CH2CHꢀ), 2.81 (2H, q, J=7.3 Hz, CH2CH3), 3.72 (2H,
s, ꢀCCH2Cꢂ), 7.51 (1H, t, J=2.7 Hz, HCꢀ). 13C-NMR
(100 MHz, CDCl3): l=15.7, 26.6, 26.9, 28.8, 34.2, 97.0
(alkyne-C), 102.2 (alkyne-C), 144.6 (ꢀCCH2), 160.2
4.6.4. Reaction with ethylene gas at 25 atm pressure
A solution of hexacarbonyl[m-[(1,2-h:1,2-h)hepta-1,4-
diyne]]dicobalt-(CoꢁCo) (4a) (0.46 g, 1.20 mmol) in
toluene (7 ml) was added to a 50 ml autoclave vessel. A
test tube that contained a solution of trimethylamine
N-oxide dihydrate (1.20 g, 10.8 mmol) in MeOH (7 ml)
was then placed inside the autoclave vessel and care
was taken to avoid mixing these reactants before the
system was placed under 25 atm of ethylene. The
mixture was then agitated for 60 h at 25 °C before it
was filtered through a pad of silica using CH2Cl2 as the
eluent. The filtrate was evaporated under reduced pres-
sure to leave a crude residue, which was purified by
column chromatography on silica using 10% Et2O in
light petroleum as the eluent to give 2-(pent-2-yn-1-
yl)cyclopent-2-en-1-one (3a) (0.02 g, 11%) as a pale
yellow oil. Analytical data were as given above.
(HCꢀ), 200.0 (Co(CO)), 208.7 (CꢀO). wmax (cm−1
,
CH2Cl2) 2091, 2040, 2008, 1708, 1638. HRMS: m/z:
Found: 377.93811. Calc. for C14H12Co2O5 [M+−2CO]:
377.93633. Also isolated from this reaction were start-
ing complex 4a (0.42 g, 53%) and the cyclopentenone 3a
(0.03 g, 10%).
4.6.6.2. Reaction at 40 °C. A mixture of dimethyl sulf-
oxide (1 ml), hexacarbonyl[m-[(1,2-h:1,2-h)hepta-1,4-
diyne]]dicobalt-(CoꢁCo) (4a) (0.32 g, 0.85 mmol) and
benzene (30 ml) in a 50 ml autoclave vessel was placed
under 30 atm pressure of ethylene gas and agitated for
60 h at 40 °C. The mixture was then filtered through a
pad of silica using Et2O as the eluent. The filtrate was
evaporated under reduced pressure to leave a crude
residue, which was purified by column chromatography
on silica using a 10–50% Et2O in light petroleum
gradient as the eluent to give 2-ethyl-3-[(5-oxocy-
clopent-1-enyl)methyl]cyclopent-2-en-1-one (8a) or 3-
ethyl-2-[(5-oxocyclopent-1-enyl)methyl]cyclopent-2-en-
4.6.5. Reaction with norbornene; formation of
3a,4,5,6,7,7a-hexahydro-4,7-methano-2-
(pent-2-yn-1-yl)-1H-inden-1-one (6)
A solution of N-methylmorpholine N-oxide monohy-
drate (1.20 g, 8.89 mmol) in CH2Cl2 (20 ml) was added
over a 2 h period (syringe pump) to a stirred solution of
hexacarbonyl[m - [(1,2 - h:1,2 - h)hepta - 1,4 - diyne]]dico-
balt-(CoꢁCo) (4a) (0.33 g, 0.87 mmol) and norbornene
(0.50 g, 5.32 mmol) in CH2Cl2 (20 ml) at 25 °C. The
mixture was stirred for a further 1 h before it was
filtered through a pad of silica using CH2Cl2 as the
eluent. The filtrate was evaporated under reduced pres-
sure to leave a crude residue, which was purified by
column chromatography on silica using a 10–40% Et2O
in light petroleum gradient as the eluent to give
3a,4,5,6,7,7a-hexahydro-4,7-methano-2-(pent-2-yn-1-
yl)-1H-inden-1-one (6) (0.06 g, 30%) as a pale yellow
1
1-one (8b) (0.04 g, 23%) as a red oil. H-NMR (400
MHz, CDCl3): l=1.08 (3H, t, J=7.6 Hz), 2.34 (4H,
m), 2.47 (4H, m), 2.48 (2H, m), 3.01 (2H, s), 7.21 (1H,
m). 13C-NMR (100 MHz, CDCl3): l=12.0, 18.7, 24.5,
26.6, 28.9, 34.3, 34.6, 136.9, 143.4, 159.0, 177.3, 209.2,
209.6. wmax (cm−1, CH2Cl2): 1689, 1638. HRMS: m/z:
Found: 204.11591. Calc. for C13H16O2 [M+]: 204.11503.
The cyclopentenone 3a (0.02 g, 12%) was also isolated
from this reaction.
1
oil. H-NMR (400 MHz, CDCl3): l=0.86–1.31 (7H,
m), 1.65 (2H, m), 2.20 (4H, m), 2.42 (1H, m), 2.61 (1H,
m), 3.07 (2H, s, ꢀCCH2Cꢂ), 7.40 (1H, s, CHꢀ). 13C-
NMR (100 MHz, CDCl3): l=13.0, 14.7, 16.1, 28.9,
29.6, 31.7, 38.6, 39.5, 48.7, 55.0, 75.4 (alkyne-C), 82.7
(alkyne-C), 145.3 (ꢀCCH2), 160.9 (HCꢀ), 205.5 (CO).
wmax (cm−1, CH2Cl2): 2206, 1695. HRMS: m/z: Found:
214.13570. Calc. for C15H18O [M+]: 214.13577.
4.7. (3-Oxo-2-(pent-2-yn-1-yl)cyclopentyl)-
trimethylsilylacetic acid methyl ester (2b) [10]
Titanium tetrachloride (0.22 g, 2.00 mmol) was
added to a stirred solution of 2-(pent-2-yn-1-yl)cyclo-

W.J. Kerr et al. / Journal of Organometallic Chemistry 630 (2001) 118–124
123
pent-2-en-1-one (3a) (0.27 g, 1.82 mmol) in CH2Cl2 (10
ml) at −70 °C. An immediate dark red colour was
system was evacuated and refilled with hydrogen gas
via a balloon attached to the flask. The mixture was
stirred under this hydrogen atmosphere for 3 h at room
temperature before it was filtered through a short plug
of kieselguhr which was then washed thoroughly with
Et2O. The filtrate was evaporated under reduced pres-
sure to give cis-methyl jasmonate (1a) (0.10 g, 99%) as
a pale yellow oil. This sample was indistinguishable in
produced. After
2 min [[1-methoxy-2-(trimethylsi-
lyl)ethenyl]oxy]trimethylsilane (0.44 g, 2.00 mmol) was
added dropwise over a 5 min period and the mixture
was stirred for a further 1 h before saturated aqueous
potassium carbonate (4 ml) was added. The mixture
was allowed to warm to room temperature and was
then partitioned between CH2Cl2 (75 ml) and saturated
aqueous potassium carbonate (75 ml). The organic
phase was dried and evaporated under reduced pressure
to leave a crude residue, which was purified by column
chromatography on silica using a 10–20% Et2O in light
petroleum gradient as the eluent to give (3-oxo-2-(pent-
2-yn-1-yl)cyclopentyl)trimethylsilylacetic acid methyl
1
its IR- and H-NMR spectra from a redistilled com-
1
mercial sample [19]. H-NMR (400 MHz, CDCl3): l=
0.94 (3H, t, J=7.2 Hz, CH3CH2), 1.51 (1H, m), 1.89
(1H, m), 2.00–2.39 (9H, overlapping m), 2.70 (1H, m),
3.69 (3H, s, OCH3), 5.25 (1H, m, olefinic-H), 5.46 (1H,
m, olefinic-H). 13C-NMR (100 MHz, CDCl3): l=14.6,
21.0, 25.8, 27.6, 38.1, 38.4, 39.2, 52.0, 54.4, 125.3
(olefinic-C), 134.4 (olefinic-C), 172.9 (CO2), 219.4 (CO).
wmax (cm−1, CH2Cl2): 1740. T2-cis-methyl jasmonate
1
ester 2b (0.48 g, 90%) as a pale yellow oil. H-NMR
(400 MHz, CDCl3): l=0.17 (9H, s, Si(CH3)3), 1.08
(3H, t, J=4.8 Hz, CH2CH3), 2.02–2.56 (11H, mm),
3.62 (3H, s, OCH3). 13C-NMR (100 MHz, CDCl3):
l= −0.9 (Si(CH3)3), 12.7, 14.6, 17.5, 24.5, 37.9, 38.2,
40.2, 51.2, 51.8, 76.1 (alkyne-C), 84.2 (alkyne-C), 174.6
(CO2), 218.2 (CO). wmax (cm−1, CH2Cl2) 1746, 1708.
HRMS: m/z: Found: 294.16302. Calc. for C16H25O3Si
[M+−1]: 294.16512.
3
(1b): H-NMR (320 MHz, CDCl3): l=5.30 (olefinic-
T), 5.48 (olefinic-T).
4.10. (5-Oxocyclopent-1-en-1-yl)acetaldehyde
[2-( formylmethyl)cyclopent-2-en-1-one] (9b) [20]
The Dess–Martin periodinane [13] (6.30 g, 14.8
mmol) was added to a solution of 2-(2-hydroxyethyl)-
cyclopent-2-en-1-one (9a) [4a] (1.60 g, 13.0 mmol) in
10% MeCN in CH2Cl2 (50 ml) at 25 °C. The mixture
was stirred for 1 h before aqueous sodium thiosulfate
solution (14.9 g in 30 ml) and saturated aqueous
sodium hydrogen carbonate solution (50 ml) was
added. The mixture was stirred vigorously for a further
30 min before the organic phase was separated, dried,
and concentrated under reduced pressure to leave a
crude residue, which was purified by column chro-
matography on silica using 50% Et2O in light petroleum
as the eluent to give (5-oxocyclopent-1-en-1-yl)-
acetaldehyde (9b) (0.80 g, 50%) as a pale yellow oil.
1H-NMR (400 MHz, CDCl3): l=2.42 (2H, m,
CH2CH2CO), 2.66 (2H, m, CH2CH2CO), 3.33 (2H, s,
ꢀCCH2CHO), 7.58 (1H, m, HCꢀ), 9.68 (1H, s, CHO).
wmax (cm−1, CH2Cl2): 2927, 2844, 2736, 1727, 1695.
4.8. Methyl dehydrojasmonate or (3-oxo-2-
(pent-2-yn-1-yl)cyclopentyl)acetic acid methyl ester
(2a) [10,18]
Potassium carbonate (0.01 g, 0.07 mmol) was added
to a stirred solution of (3-oxo-2-(pent-2-yn-1-yl)cyclo-
pentyl)trimethylsilylacetic acid methyl ester (2b) (0.35 g,
1.19 mmol) in MeOH (20 ml) at 25 °C. The mixture
was stirred for 4 h before it was diluted with Et2O and
filtered through a pad of silica using Et2O as the eluent.
The filtrate was evaporated under reduced pressure to
leave a crude residue, which was purified by silica
chromatography using
a 10–30% Et2O in light
petroleum gradient as the eluent to give methyl dehy-
drojasmonate or (3-oxo-2-(pent-2-yn-1-yl)cyclopentyl)-
acetic acid methyl ester (2a) (0.25 g, 95%) as a clear oil.
1H-NMR (400 MHz, CDCl3): l=1.04 (3H, t, J=4.8
Hz, CH3CH2), 1.49 (1H, m), 1.89 (1H, m), 2.09 (3H,
m), 2.22–2.53 (6H, m), 2.79 (1H, dd, J=15.4, 4.4 Hz),
3.67 (3H, s, OCH3). 13C-NMR (100 MHz, CDCl3):
l=12.7, 14.5, 17.9, 27.6, 38.1 (CH2Cꢂ), 38.3, 39.0
(CH2Cꢂ), 52.0 (OCCHCH2), 53.3 (OCH3), 76.2
(alkyne-C), 84.1 (alkyne-C), 172.9 (CO2), 217.8 (CO).
wmax (cm−1, CH2Cl2): 1740, 1631. HRMS: m/z: Found:
222.12554. Calc. for C13H18O3 [M+]: 222.12559.
4.11. 2-(Methanesulfonyloxymethyl)cyclopent-
2-en-1-one (9g)
A solution of methanesulfonyl chloride (0.69 g, 6.03
mmol) in CH2Cl2 (10 ml) was added over a 5 min
period to a stirred solution of 2-(hydroxymethyl)-
cyclopent-2-en-1-one (9d) [4a] (0.52 g, 4.64 mmol) and
Et3N (1.00 g, 9.90 mmol) in CH2Cl2 (10 ml) at −5 °C.
The mixture was then stirred for 1 h before it was
filtered through a pad of silica using CH2Cl2 as the
eluent. The filtrate was evaporated under reduced pres-
sure to leave a crude residue, which was purified by
column chromatography on silica using Et2O as the
eluent to give 2-(methanesulfonyloxymethyl)cyclopent-
4.9. cis-Methyl jasmonate (1a) [1a,10,17]
Lindlar catalyst (5.0 mg) was added to a solution of
(3-oxo-2-(pent-2-yn-1-yl)cyclopentyl)acetic acid methyl
ester (2a) (0.10 g, 0.4 mmol) in toluene (10 ml). The

124
W.J. Kerr et al. / Journal of Organometallic Chemistry 630 (2001) 118–124
1
(martin.mueller@lrz.uni-muenchen.de), Pharmazeutische Biolo-
gie, Universita¨t Mu¨nchen, Karlstrasse 29, 80333 Mu¨nchen, Ger-
many, fax: +49-89-590-2611.
2-en-1-one (9g) (0.79 g, 90%) as a clear oil. H-NMR
(400 MHz, CDCl3): l=2.42 (2H, m, CH2CO), 2.66
(2H, m, CH2CHꢀ), 3.03 (3H, s, CH3SO3), 4.81 (2H, m,
CH2O), 7.74 (1H, s, CHꢀ). 13C-NMR (100 MHz,
CDCl3): l=27.3, 34.7, 37.7, 63.1 (CH2O), 139.4
[3] Dr E.W. Weiler, Lehrstuhl fu¨r Planzenphysiologie, Fakulta¨t fu¨r
Biologie, Ruhr-Universita¨t Bochum, Geba¨ude ND 3/30, Posfach
10 21 48, Universita¨tsstrasse, 150, D-44801 Bochum, Germany,
Tel.: +49-2-34-700-4291; fax: +49-2-34-709-4187.
[4] (a) W.J. Kerr, M. McLaughlin, P.L. Pauson, S.M. Robertson, J.
Organomet. Chem. 630 (2001) 104–117;
(b) W.J. Kerr, M. McLaughlin, P.L. Pauson, S.M. Robertson,
Chem. Commun. (1999) 2171.
[5] S. Padmanabhan, K.M. Nicholas, Tetrahedron Lett. 24 (1983)
2239.
(OCCꢀ), 163.5 (HCꢀ), 207.2 (CꢀO). wmax (cm−1
CH2Cl2): 1734, 1695, 1625. Compound instability pre-
vented any further characterisation.
,
4.12. 2-(Iodomethyl)cyclopent-2-en-1-one (9h)
[6] We are grateful to Dr R. Colman of Lancaster Synthesis Ltd,
Newgate, White Lund, Morcambe, Lancashire, LA3 3DY, UK,
for supplying us with this reagent.
[7] Surprisingly, the use of vinyl acetate, in place of the benzoate,
with complex 4a afforded the unreduced cyclopentenone, 5-ace-
toxy-2-(pent-2-yn-1-yl)cyclopent-2-en-1-one (13% yield), as the
main isolable product; see Section 4.
[8] Y.K. Chung, B.Y. Lee, N. Jeong, M. Hudecek, P.L. Pauson,
Organometallics 12 (1993) 220.
[9] I. Matsuda, S. Murata, Y. Izumi, J. Org. Chem. 45 (1980) 237.
[10] H. Nishiyama, K. Sakuta, K. Itoh, Tetrahedron Lett. 25 (1984)
2487.
A solution of 2-(methanesulfonyloxymethyl)cyclo-
pent-2-en-1-one (9g) (1.00 g, 5.26 mmol) and sodium
iodide (1.30 g, 8.67 mmol) in acetone (50 ml) was
heated under reflux for 4 h. The mixture was filtered
and the filtrate was concentrated under reduced pres-
sure to give 2-(iodomethy)cyclopent-2-en-1-one (9h)
(1.05 g, 90%) as a yellow oil. 1H-NMR (400 MHz,
CDCl3): l=2.41 (2H, m, CH2CO), 2.52 (2H, m,
CH2CHꢀ), 3.88 (2H, s, CH2I), 7.96 (1H, s, HCꢀ).
13C-NMR (100 MHz, CDCl3): l= −8.1 (CH2I), 26.9,
35.0, 144.0 (OCCꢀ), 161.2 (HCꢀ), 206.7 (CꢀO). wmax
(cm−1, CH2Cl2): 1701, 1631. HRMS: m/z: Found:
221.95327. Calc. for C6H7IO [M+]: 221.95417.
[11] (a) R. Eastmond, D.R.M. Walton, Tetrahedron 28 (1972) 4591;
(b) R. Eastmond, T.R. Johnson, D.R.M. Walton, Tetrahedron
28 (1972) 4601;
(c) C. Eaborn, R. Eastmond, D.R.M. Walton, J. Chem. Soc. (B)
(1971) 127;
(d) C. Eaborn, R. Eastmond, D.R.M. Walton, J. Chem. Soc. (B)
(1970) 752.
Acknowledgements
[12] The radiolabelling step was performed in the laboratory of
Professor J.R. Jones, Department of Chemistry, University of
Surrey, Guilford, Surrey, GU2 7XH, UK, Tel.: +44-1483-
259313, e-mail: j.r.jones@surrey.ac.uk. We thank Professor
Jones and his co-workers for their assistance.
[13] D.B. Dess, J.C. Martin, J. Org. Chem. 48 (1983) 4155.
[14] (a) F. Ramirez, N.B. Desai, N. McKelvie, J. Am. Chem. Soc. 84
(1962) 1745;
We are grateful to the Carnegie Trust for the Univer-
sities of Scotland for the award of a postgraduate
scholarship to M.M. We also wish to thank Astra-
Zeneca Pharmaceuticals, Alderley Park for generous
funding of our research endeavours via Strategic Re-
search Funding, and the EPSRC Mass Spectrometry
Service, University of Wales, Swansea for analyses.
(b) E.J. Corey, P.L. Fuchs, Tetrahedron Lett. (1972) 3769;
(c) H.J. Bestmann, K. Li, Chem. Ber. 115 (1982) 828;
(d) H.J. Bestmann, H. Frey, Justus Liebigs, Ann. Chem. (1980)
2061.
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