Easy synthesis of heterocyclic carbene complexes by activation of chalcogenopyrones and benzopyrones to pyrylium salts and subsequent addition of carbanion of methoxy(methyl)pentacarbonyltungsten carbene complex

Article abstract of DOI:10.1016/j.jorganchem.2007.08.039

Methylenechalcogenopyran and benzopyran Fischer carbene complexes are easily obtained from commercially available chalcogenopyrones or benzopyrones and carbanion of methoxy(methyl)carbene tungsten complex. The key of the heterocyclic carbene formation is the activation of the carbonyl group by alkylation with alkyl trifluoromethanesulfonate reagent.

Full text of DOI:10.1016/j.jorganchem.2007.08.039

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 692 (2007) 5517–5522
www.elsevier.com/locate/jorganchem
Note
Easy synthesis of heterocyclic carbene complexes by activation
of chalcogenopyrones and benzopyrones to pyrylium salts
and subsequent addition of carbanion
q
of methoxy(methyl)pentacarbonyltungsten carbene complex
a
b
c,
c
c
J.-Y. Le Bihan , N. Faux , B. Caro *, F. Robin-Le Guen , P. Le Poul
a
I.U.T. Lannion, B.P. 30219, rue E. Branly, 22302 Lannion, France
Laboratoire de Chimie The´rapeutique EA 1043, Faculte´ des Sciences Pharmaceutiques et Biologiques de Lille,
b
3 rue du Professeur Laguesse, B.P. 83, 59006 Lille, France
U.M.R. Sciences Chimiques, CNRS 6226, I.U.T. Lannion, B.P. 30219, rue E. Branly, 22302 Lannion, France
c
Received 28 June 2007; received in revised form 30 August 2007; accepted 30 August 2007
Available online 6 September 2007
Abstract
Methylenechalcogenopyran and benzopyran Fischer carbene complexes are easily obtained from commercially available chalcogen-
opyrones or benzopyrones and carbanion of methoxy(methyl)carbene tungsten complex. The key of the heterocyclic carbene formation
is the activation of the carbonyl group by alkylation with alkyl trifluoromethanesulfonate reagent.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Methylenechalcogenopyran and benzopyran carbene complexes; Pyrylium salts; Chalcogenopyrone and benzopyrone
1. Introduction
cogenopyran and methylenebenzochalcogenopyran Fischer
carbene complexes (Scheme 1) [4]. Most of these com-
plexes, which are the key of the electron rich molecule for-
mation, are synthetized from a condensation reaction
between carbanions of Fischer-type carbene complexes [5]
and c-unsubstituted pyrylium salts (Scheme 1) [6].
The second step of this reaction, which implies a hydride
departure, requires the use of triphenyl carbenium salt as
an oxidant. As the pentacarbonylmetal fragment is sensi-
tive to oxidant reagents, the heterocyclic carbene com-
plexes are isolated in moderate to low yield [6].
Therefore, to tentatively improve the yield, and to
obtain carbene complexes with new methylenechalcogeno-
pyran and benzopyran heterocyclic nuclei, we wished to
develop an expedient route to these compounds, using
commercially available a and c-chalcogenopyrones and
benzopyrones. It is well established that methylation or
silylation of the nucleophilic carbonyl oxygen atom of these
substrates increases the reactivity towards nucleophile
As their tetrachalcogenofulvene isoelectronic analogues
[1], the bichalcogenopyrans form, with various acceptors
charge transfer complexes [2] possessing interesting electri-
cal and magnetic properties. However, in comparison with
the large studies about the TTF (Tetrathiafulvalene) and
related heterocyclic compound chemistry during the past
twenty years [1], few works were devoted to electron rich
bipyran molecules [3]. Some of us have recently reported
on the synthesis of electron rich extended bichalcogenopy-
rans and benzopyrans bearing methoxy groups in the
ethylenic spacer. These compounds were obtained from a
Pdꢁ catalytic coupling reaction of a and c-methylenechal-
q
To the memory of Dr. Pierre GUENOT, Director of the Centre
´
´
Regional de Mesures Physiques de l’Ouest – Universite de Rennes 1.
*
Corresponding author. Tel.: +33 2 96485748; fax: +33 2 96485797.
E-mail address: bertrand.caro@univ-rennes1.fr (B. Caro).
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.08.039

5518
J.-Y. Le Bihan et al. / Journal of Organometallic Chemistry 692 (2007) 5517–5522
(OC)5W
OCH3
H
R1
R2
R1
-
BF4
W(CO)5C(OCH3)CH2Li
+
R3
O
R2
O
R3
Ph3C+ BF4
-
(OC)5W
OCH3
R1
R2
R1
R2
O
O
R3
Pd˚
R3
H3CO
2
Scheme 1. Access to extended bipyrans from pyrylium salts and carbene complex.
addition, due to the formation of highly electrophilic a or
c-alkoxychalcogenopyrylium and benzopyrylium salts [7].
In this particular case the presence of the leaving alkoxy
group should allow the formation of the methylenechalco-
genopyran and benzopyran carbene complexes without the
oxidation step. Recently, following a similar experimental
procedure, we successfully obtained good yield of dithiaful-
vene carbene complexes from dithiolium salts bearing a
leaving thiomethyl group [8].
yellow to blue. After hydrolysis, extraction with ether,
and chromatography (silicagel, eluent: ether/petroleum
ether) the telluromethylenepyran carbene complex 2a was
isolated (81% yield). The same two-step process was then
applied to commercially available 2,6-diphenylthiopyrone
1b. Unfortunately, isolation of the corresponding 4-meth-
oxythiopyrylium salt was unsuccessful because of the great
sensitivity of this compound towards moisture. To over-
come this difficulty, a one pot procedure was then
attempted. Pyrone 1b and excess of methyl trifluorome-
thane sulfonate were heated at 60 ꢁC for 1 h. Excess of
the alkylating reagent was removed under vacuum and
the solid residue was dissolved in dry THF. The meth-
oxy(methyl)carbene complex and NEt3 were then added
successively. The solution turned blue. After hydrolysis,
extraction with ether, and chromatography (silicagel, elu-
ent: ether/petroleum ether), the blue methylenethiopyran
carbene complex 2b was isolated (32% yield).
2. Results and discussion
To test this synthetic methodology in the chalcogenopy-
rone and chalcogenobenzopyrone series, we first chose to
consider the case of 2,6-diphenyltelluropyrone (Scheme
2). Mixing the telluropyrone 1a, with an excess of methyl
trifluoromethanesulfonate in boiling CH2Cl2, afforded the
2,6-diphenyl-4-methoxytelluropyran trifluoromethanesulf-
onate salt 10a in 57% yield (white powder). Adding NEt3
to a THF solution of 10a and methoxy(methyl)carbene
tungsten complex instantly produced a color change from
For comparison purposes, we performed a reaction in
THF at ꢀ78 ꢁC with the air sensitive 2,6-diphenylthiopyry-
lium tetrafluoroborate and the carbanion formed by BuLi
W(CO)5
H3C
O
O
X
OCH3
δ
1) CH3(OCH3)CW(CO)5
2) NEt3
R2
R3
R2
R3
R2
R3
+
O
SO2CF3
γ
β
β'
α'
H3C
X
R1
R1
α
X
R1
-
OSO2CF3
1'a
2a
2b
2c
1a R1 = R3 = Ph, R2 = H, X = Te
1b R1 = R3 = Ph, R2 = H, X = S
1c R1 = Ph, R2 = R3 = (CH)4, X = S
Scheme 2. Chalcogenomethylenepyran and benzomethylenepyran carbene complex formation.

J.-Y. Le Bihan et al. / Journal of Organometallic Chemistry 692 (2007) 5517–5522
5519
action on the CH3(OCH3)CW(CO)5 complex [6]. Subse-
quent addition of Ph3C+BF4ꢀ salt gave 2b in very low yield
(5%) (Scheme 1). This result emphasized on the efficiency
of the pyrone and benzopyrone route.
characteristic of the presence of the 2-phenyl-4-methoxy-
naphthopyrylium salt [9]. However, subsequent addition
of the methyl(methoxy)carbene tungsten complex and
NEt3 did not give the expected heterocyclic carbene com-
plex 2e (Fig. 1). It seems that the presence of a benzenic
nucleus near the reactive carbon atom prevents, for steric
reasons, the carbanion addition. Such limitation of reactiv-
ity is not unprecedented [6]. It was previously observed for
a c-unsubstituted pyrylium salt bearing fused saturated car-
bon rings. The steric influence on the course of the reaction
is also exemplified by the chromone case 1f (Scheme 3). The
lack of substituent in the a position dramatically changed
the regioselectivity of the carbanion addition. The unsatu-
rated carbene complex 2f, obtained from carbanion addi-
tion onto the heterocyclic a carbon, followed by a ring
opening elimination step, was isolated in low yield (28%).
In that case, an uncharacterized insoluble precipitate was
also formed.
The 1H NMR spectra (500 MHz, THF-d8) of 2a, 2b dis-
0
played three singlets, characterizing Hb, Hb and Hd. As
previously reported for the analogous pyran complex
(Scheme 2, R1 = Ph, R2 = H, R3 = Ph, X = O) [6], the
0
Hb is more deshielded than the Hb due to the presence
of the carbene fragment. (dHb: 8.13 ppm, X = O [6]; 2b:
0
8.55 ppm, X = S; 2a: 8.61 ppm, X = Te; dHb : 8.09 ppm,
X = O [6]; 2b: 7.34 ppm, X = S; 2a: 7.34, X = Te).
The reaction was extended to the commercially available
2-phenylthiobenzopyrone 1c (Scheme 2) and to 2-phenyl
a-naphthopyrone 1d (Fig. 1) without any experimental
modification. The expected complexes 2c (Scheme 2) and
2d (Fig. 1), in which the carbene fragment is opposite to
the fused benzene ring, were obtained in moderate to good
yield (2c: 43%, 2d: 61%). The 1H NMR spectra of 2c and 2d
confirmed the stereochemistry assignment. The Hb
resonates at 8.52 ppm for 2c and 8.37 ppm for 2d in accor-
dance with the carbene fragment influence [6]. Adding
excess of methyl trifluoromethanesulfonate to the b naph-
thopyrone 1e after heating, led to a fluorescent solution
1
The structure of carbene 2f was confirmed by the H
NMR spectrum, which showed a phenolic proton signal
at 8.47 ppm (THFd8) and quadruplet–triplet signals charac-
teristic of the ethoxy group [10]. In addition, the alkene
hydrogen chemical shift sequence was different from that
found for the benzomethylenepyran carbene complexes 2c
0
and 2d. In addition, the coupling constant between Ha
0
and Hb (14.3 Hz) confirms the trans stereochemistry
0
0
around the Ca Cb double bond. On the other hand, the
presence of an aldehyde function in the b position of the
benzopyrone 1g (Scheme 2) seemed to prevent alkylation
of the ketone function. Under a prolonged heating influ-
ence, a black powder, insoluble in CH2Cl2, was only iso-
lated. However, using trimethylsilylchloride (TMSCl) and
NEt3 allowed the formation of the condensation product
2g, as the result of a reaction between the aldehyde func-
tion in 1g and the carbene carbanion [11]. Finally, we suc-
cessfully applied the one-pot methylation-carbanion
sequences to the coumarin case (Scheme 4). The expected
condensation product was isolated as a mixture of isomers
H
Y
Y
H
H
β
β
α
O
Ph
α
O
Ph
1e, Y = O
2e, Y = CH-C(OCH3)W(CO)5
1d, Y = O
2d, Y = CH-C(OCH3)W(CO)5
Fig. 1. a and b naphthopyrones and related carbenes.
OCH2CH3
H3CH2C
δ'
O
γ
'
O
O
R
β'
1) CH3(OCH3)CW(CO)5
R
CF3SO2OC2H5
R = H
α'
OH
2) NEt3
O
W(CO)5
H3CO
W(CO)5
-
OSO2CF3
R = CHO
2f
O
OCH3
1) CH3(OCH3)CW(CO)5
1f R = H
1g R = CHO
3) NEt3
2) TMSCl
β
α
O
2g
Scheme 3. Reactivity of a-unsubstituted benzopyranones.

5520
J.-Y. Le Bihan et al. / Journal of Organometallic Chemistry 692 (2007) 5517–5522
γ
β
OCH3
α
W(CO)5
O
CF3SO2OCH3
1) CH3(OCH3)CW(CO)5
2h
γ
+
2) NEt3
OCH3
β
O
O
O
α
-
OSO2CF3
1h
O
H3CO
W(CO)5
2h'
Scheme 4. Reactivity of coumarin 1 h.
1
2h, 2h0, (60:40%, from H NMR spectum, 53% yield). The
1H NMR spectrum of the isomer mixture showed that the
alkene b hydrogen is more deshielded for the major isomer
(7.69 ppm) than for the minor isomer (6.15 ppm). As exem-
plified in Scheme 4, in 2h the b hydrogen is closed to the
carbene fragment, which induces a pronounced deshielding
effect [6]. It is hardly to be expected that the b hydrogen in
2h resonates at low field. Consequently structure 2h was
assigned to the major isomer.
Regional de Mesures Physiques de l’Ouest (Universite de
Rennes 1). Mass spectra were obtained on a high Resolu-
tion MS/MS Zab spec Tof micromass (Centre Regional
´
´
de Mesures Physiques universite de Rennes 1). a and c-
pyrones and benzopyrones are commercial products avail-
able from Aldrich (except the telluropyrone 1a [12]).
4.1. General procedure for the preparation of the complexes
by activation of the ketone function
3. Conclusion
Pyrones or benzopyrones were dissolved in an excess of
methyl or ethyl trifluoromethanesulfonate (10 equiv.) at
90 ꢁC (water bath). The solution was then heated at
60 ꢁC for 1 h. The excess of the alkylating reagent was
removed under vacuum and the obtained solid residue
was dissolved in dry THF (10 mL). The methoxy(methyl)
carbene complex (1 equiv.) and NEt3 (2 equiv.) were suc-
cessively added. The solution turned blue-purple or red.
The reaction was monitored by TLC. Cold water was
poured into the reaction mixture and the product was
extracted with diethyl ether. The extract was dried over
magnesium sulfate and the solvent was removed under
reduced pressure. After a chromatography on silicagel
plates (eluant: petroleum ether/diethylether), the heterocy-
clic carbene complexes were isolated. For the telluropyryli-
um 1a case, the telluropyrylium salt was isolated by adding
diethylether in the reaction mixture [9]. In a second step,
the telluropyran salt and the carbene were dissolved in
THF, followed by NEt3 addition.
To summarize, we have described an unprecedented easy
access to new heterocyclic methylenechalcogenopyran and
methylenechalcogenobenzopyran carbene complexes based
on the activation of the commercially available heterocyclic
ketones by alkylating reagents and the high reactivity of the
intermediate pyrylium salts towards the carbanion of meth-
oxy(methyl)pentacarbonyltungsten carbene. The organo-
metallic carbanion addition was sensitive to the steric
strain. For a-substituted heterocycles, c-addition is
observed. After an elimination step, the expected heterocy-
clic carbene complexes were obtained in moderate to good
yield. With unsubstituted benzopyrone 1f, an a-addition
followed by a ring opening step was observed. Finally, this
synthetic methodology was successfully applied to the cou-
marin case.
Pdꢁ self-dimerization of these carbenes should open the
route to new extended a and c-bichalcogenopyrans and
benzopyrans.
4.2. Synthesis of thiopyran carbene complex 2b from
2,6-diphenylthiopyrylium tetrafluoroborate salt
4. Experimental
General: All preparations involving organometallic
methylenepyrans and benzopyrans were carried out in an
atmosphere of dry nitrogen. Solvents were dried and dis-
At ꢀ78 ꢁC, 0.70 mL of a 2.5 M solution of n-BuLi
(1.7 · 10ꢀ3 mol) were added to a solution of meth-
oxy(methyl)carbene complex (500 mg, 1.3 · 10ꢀ3 mol), in
dry THF (10 mL), under a N2 atmosphere. Thiopyrylium
salt (1.1 g, 3.3 · 10ꢀ3 mol) was then added. The solution
was stirred for 1 h at room temperature. Removal of
THF, at low pressure, left a dark residue, which was
diluted in 20 mL of CH2Cl2. Triphenyl carbenium tetra-
1
tilled according to standard procedure. H and 13C NMR
spectra were recorded in CDCl or in THF-d on a Brucker
¨
3
8
spectrometer (500 MHz). Infrared spectra were recorded
on a Perkin Elmer spectrometer FTIR-1000 using KBr
plates. Elemental Analyses were performed by the Centre

J.-Y. Le Bihan et al. / Journal of Organometallic Chemistry 692 (2007) 5517–5522
5521
fluoroborate (324 mg, 9.8 · 10ꢀ4 mol) was then added.
Removal of the solvent left a residue, which was subse-
quently subjected to column chromatography on silicagel
using 80/20 v/v petroleum ether/diethyl ether as eluent.
Complex 2b was isolated as purple crystals (44 mg, 5%
yield).
1H NMR (THF-d8, d (ppm)): 8.54 (s, 1H, Hb), 8.25
(m, 1H, Hbenzo), 8.14 (s, 1H, Hd), 7.76 (m, 2H, HPh), 7.71
(m, 1H, Hbenzo), 7.60 (m, 2H, Hbenzo), 7.52 (m, 3H, HPh),
1
4.68 (s, 3H, OCH3). 13C NMR (2D Correlation H/13C:
HMBC, HMQC) (THF-d8, d (ppm)): 295.0 (C(carbene)),
204.7 (CO), 199.5 (CO), 148.8 (CPh), 138.5 (Ca), 137.1
(Cbenzo), 135.7 (Cbenzo), 135.2 (Cd), 131.4 (CPh), 131.0
(CPh), 130.2 (Cbenzo), 130.1 (Cbenzo), 129.0 (Cc), 128.4
(Cbenzo), 127.7 (CPh), 127.2 (Cbenzo), 122.8 (Cb), 69.6
4.3. Synthesis of pyran carbene complex 2g from
3-formylchromone
(OCH3). IR (KBr plate) t (cmꢀ1): 2052, 1970, 1566, 1531,
ꢀ
A THF solution made of 3-formyl chromone (454 mg,
2.6 · 10ꢀ3 mol), methoxy(methyl)pentacarbonyltungsten
carbene complex (1 g, 2.6 · 10ꢀ3 mol), trimethylsilylchlo-
ride (7.8 · 10ꢀ3 mol), and triethylamine (7.8 · 10ꢀ3 mol),
was stirred at room temperature. The reaction controlled
by TLC showed that carbene complex quickly disappeared.
Cold water was poured into the orange reaction mixture
and the product was extracted with diethylether. The
extract was dried over magnesium sulfate and the solvent
was removed under reduced pressure. The residue was
chromatographied on silicagel column (Petroleum ether/
diethylether 80/20), and 2g was isolated as red crystals
(850 mg, 61% yield).
1487, 1438, 1211. Anal. Calc. for C23H14O6SW: C, 45.87;
H, 2.34; S, 5.32. Found: C, 45.89; H, 2.33; S, 5.35%.
Compound 2d (Fig. 1): 630 mg are obtained from
408 mg of 1d (yield 66%, purple crystals).
1H NMR (THF-d8, d (ppm)): 8.66 (m, 1H, Hnaphtho),
8.37 (s, 1H, Hb), 8.17 (m, 2H, HPh), 8.06 (d, 1H, Hnaphtho),
8.02 (m, 1H, Hnaphtho), 7.97 (s, 1H, Hd), 7.93 (d,
1H,3J = 9.14 Hz), 7.62 (m, 3H, HPh), 7.52 (m, 2H, HPh),
1
4.69 (s, 3H, OCH3). 13C NMR (2D Correlation H/13C:
HMBC, HMQC) (THF-d8, d (ppm)): 291.0 (C(carbene)),
204.6 (CO), 199.8 (CO), 160.1 (Ca), 152.0 (Cnaphtho),
139.3 (CPh), 136.2 (Cnaphtho), 134.6 (Cnaphtho), 132.3
(CPh), 130.2 (Cnaphtho); 130.1 (CPh), 129.7 (Cnaphtho),
129.2 (Cd), 129.0 (Cnaphtho), 128.6 (Cnaphtho), 127.6 (CPh),
125.2 (Cnaphtho), 122.9 (Cnaphtho), 120.4 (Cnaphtho) 106.9
4.4. Spectroscopic data of carbene complexes
(Cb), 67.5 (OCH3). IR (KBr plate) t (cmꢀ1): 2053, 1892,
ꢀ
Compound 2a (Scheme 2): 1028 mg (2 · 10ꢀ3 mol) of
4-methoxy-2,6-diphenyltelluropyrylium trifluoromethane-
sulfonate and 500 mg of methoxy(methyl)pentacarbonyl-
carbene tungsten complex gave 766 mg of 2a (yield 81%,
purple crystals).
1607, 1556, 1498, 1224. Anal. Calc. for C27H16O7W: C,
50.96; H, 2.53. Found: C, 49.74; H, 2.64%.
Compound 2f (Scheme 3): 191 mg are obtained from
292 mg of 1f (yield 28%, red crystals). In this case ethyl
trifluoromethanesulfonate was used.
1H NMR (THF-d8, d (ppm)): 8.61 (s, 1H, Hb), 7.62
(s, 1H, Hd), 7.61 (m, 4H, HPh), 7.49 (m, 6H, HPh), 7.34
1H NMR (THF-d8, d (ppm)): 8.47 (s, 1H, OH), 7.32
3
(dd, 1H, 3J = 14.3 Hz, J = 11.6 Hz, Hb ), 7.27 (m, 1H,
0
(s, 1H, Hb ), 4.58 (s, 3H, OCH3). 13C NMR (2D Correla-
HPh), 7.15 (m, 2H, Ha (3J = 14.3 Hz) and HPh), 6.86
0
0
1
tion H/13C: HMBC, HMQC) (THF-d8, d (ppm)): 292.2
(m, 1H, HPh), 6.84 (m, 1H, HPh), 5.98 (d, 1H,
3
0
(C(carbene)), 204.9 (CO), 199.4 (CO), 149.6 (Ca), 146.0
J = 11.6 Hz, Hc ), 4.36 (s, 3H, OCH3), 4.11 (q, 2H,
(Ca ), 144.2 (Cd), 143.7 (CPh), 143.1 (CPh), 142.0 (Cc),
OCH2), 1.27 (t, 3H, CH3). 13C NMR (2D Correlation
0
139.9 (CPh), 130.4 (CPh), 130.3 (CPh), 127.7 (CPh), 127.6
1H/13C: HMBC, HMQC) (THF-d8, d (ppm)): 292.8 (C(car-
0
0
(CPh), 133.2 (Cb ), 131.3 (Cb), 69.3 (OCH3). IR (KBr plate)
ꢀ
bene)), 204.4 (CO), 199.1 (CO), 172.1 (Cd ), 156.2 (CPh),
t (cmꢀ1): 2053, 1979, 1893, 1582, 1570. Anal. Calc. for
147 (Cb ), 141.4 (Ca ), 119.0 (CPh), 116.9 (CPh), 105.0
0
0
0
C25H16O6TeW: C, 41.48; H, 2.23. Found: C, 41.84; H,
2.54%.
(Cc ), 67.0 (OCH3), 66.0 (OCH2), 25.3 (CH3). IR (KBr
plate) t (cmꢀ1): 3497, 2945, 2063, 1938, 1616, 1588, 1282,
ꢀ
Compound 2b (Scheme 2): 140 mg are obtained from
198 mg of pyrone1b (32% yield, purple crystals).
1H NMR (THF-d8, d (ppm)): 8.55 (s, 1H, Hb), 7.76
(m, 4H, HPh), 7.53 (m, 6H, HPh), 7.35 (s, 1H, Hd), 7.34
1195, 986. Anal. Calc. for C19H16OSW: C, 40.59; H,
2.82. Found: C, 41.03; H, 2.89%.
Compound 2g (Scheme 3): 850 mg are obtained from
1
454 mg of 1g (yield 61%, blue crystals). H NMR (CDCl3,
3
(s, 1H, Hb ), 4.55 (s, 3H, OCH3). 13C NMR (2D Correla-
d (ppm)): 8.59 (d, 1H, J = 15.2 Hz, @CH), 8.30 (d, 1H,
0
1
tion H/13C: HMBC, HMQC) (THF-d8, d (ppm)): 287.1
Hbenzo), 8.21 (s, 1H, Ha), 7.71 (t, 1H, Hbenzo), 7.48
(C(carbene)), 204.6 (CO), 199.8 (CO), 152.8 (Ca), 150.3
(m, 2H, Hbenzo), 6.99 (d, 1H, J = 15.2 Hz @CH) 4.64 (s,
1
(Ca ), 139.7 (Cc), 138.2 (Cph), 137.6 (CPh), 137.5 (Cd),
3H, OCH3). 13C NMR (2D Correlation H/13C: HMBC,
0
131.6 (CPh), 131.4 (CPh), 130.4 (CPh), 127.4 (CPh), 127.5
HMQC) (CDCl3, d (ppm)): 308.3 (C(carbene)), 204.0
(CO), 197.5 (CO), 175.8 (C@O), 157.9 (Ca), 155.2 (Cbenzo),
145.9 (–CH@), 134.2 (Cbenzo), 126.5 (Cbenzo), 126.1
(Cbenzo), 124.9 (–CH@), 124.1 (Cbenzo), 119.7 (Cb), 118.2
(Cbenzo), 69.0 (OCH3). IR (KBr plate) ꢀt (cmꢀ1): 2066,
1981, 1902, 1643, 1225, 961, 753. MS (LISMS): m/z (Calc.)
(M+Å) = 537.9885; m/z (Found) (M+Å) = 537.9894.
(Cb ), 125.0 (Cb), 68.7 (OCH3). IR (KBr plate) t (cmꢀ1):
0
ꢀ
2054, 1978, 1938, 1895, 1593, 1518. MS (FAB+, CHCl3/
CH3OH, 90/10): m/z (Calc.) (M+Å) = 629.0255; m/z
(Found) (M+Å) = 629.0221.
Compound 2c (Scheme 2): 130 mg are obtained from
180 mg of benzopyrone 1c (yield 43%, purple crystals).

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J.-Y. Le Bihan et al. / Journal of Organometallic Chemistry 692 (2007) 5517–5522
(h) K. Nakasuji, K. Takatoh, M. Nakatsuka, I. Murata, J. Chem.
Compound 2h, 2h0 mixture of isomers (60/40) (Scheme
Soc., Chem. Commun. (1981) 717;
4): 540 mg are obtained from 292 mg of coumarin 1h (yield
53%, red crystals). 1H NMR (THF-d8, Scheme 3, 2h,
d (ppm)): 7.74 (d, 1H, 3J = 10.0 Hz, Hc), 7.69 (d, 1H,
3J = 10.0 Hz, Hb), 7.59 (m, 1H, HPh), 7.53 (m, 1H, HPh),
7.39 (d, 1H, HPh), 7.26 (s, 1H, CH–Ccarb), 4.53 (s, 3H,
OCH3). 13C NMR (2D Correlation 1H/13C: HMBC,
HMQC) (THF-d8, 2h, d (ppm)): 287.0 (C(carbene)), 204.6
(CO), 199.6 (CO), 156.0 (Ca), 140.2 (Cc), 133.9 (CPh),
128.7 (CPh), 126.1 (CPh), 124.9 (CH–Ccarb), 122.6 (CPh),
122.4 (CPh), 121.1 (Cb), 117.8 (CPh), 69.0 (OCH3).
(i) C.H. Chen, J.J. Doney, G.A. Reynolds, J. Org. Chem. 47 (1982)
680;
(j) M.R. Detty, B.J. Murray, J. Org. Chem. 47 (1982) 1148;
(k) C.H. Chen, J.J. Doney, G.A. Reynolds, F.D. Saeva, J. Org.
Chem. 48 (1983) 2757;
(l) M.R. Detty, J.W. Hasset, B.J. Murray, G.A. Reynolds, Tetrahe-
dron 41 (1985) 4853.
[4] (a) F. Robin-Le Guen, P. Le Poul, B. Caro, N. Faux, N. Le Poul,
S.J. Green, Tetrahedron Lett. 43 (2002) 3967;
(b) N. Faux, F. Robin-Le Guen, P. Le Poul, B. Caro, N. Le Poul, Y.
le Mest, S.J. Green, S. Le Roux, S. Kahlal, J.Y. Saillard, Tetrahedron
63 (2007) 7142.
[5] For selected reviews on the chemistry of Fischer-type carbene
complexes see (a) K.H. Do¨tz, Angew. Chem., Int. Ed. Engl. 23
(1984) 587;
1H NMR (THF-d8, 2h0, d (ppm)): 7.69 (d, 1H,3J =
10.0 Hz, Hc), 7.59 (m, 1H, HPh), 7.53 (m, 1H, HPh), 7.43
(d, 1H, HPh), 7.32 (m, 1H, HPh), 6.77 (s, 1H, CH–Ccarb),
6.75 (d, 1H,3J = 10.0 Hz, Hb), 4.50 (s, 3H, OCH3).
(b) W.D. Wulff, in: E.W. Abel, F.G.A. Stone, G. Wilkinson (Eds.),
Comprehensive Organometallic Chemistry, vol. II, Pergamon,
Oxford, 1995, p. 470;
(c) L.S. Hegedus, in: E.W. Abel, F.G.A. Stone, Wilkinson (Eds.),
Comprehensive Organometallic Chemistry, vol. II, Pergamon,
Oxford, 1995, p. 549;
IR (KBr plate) t (cmꢀ1): 2057, 1894, 1621, 1604, 1555,
ꢀ
1522, 1476. Anal. Calc. for C17H10O7W: C, 40.03; H,
1.98. Found: C, 40.30; H, 2.52%.
Acknowledgement
(d) J.W. Herndon, Tetrahedron 56 (2000) 1257;
(e) J. Barluenga, F.J. Fananas, Tetrahedron 56 (2000) 4597;
(f) R. Aumann, Eur. J. Org. Chem. (2000) 17;
´ ´
Financial support by CNRS and by ‘Le Conseil General
des Coˆtes d’Armor et la communaute dagglomeration
`
(g) J. Barluenga, J. Santamaria, M. Tomas, Chem. Rev. 104 (2004)
´
´
4597;
´
Lannion Tregor’ are gratefully acknowledged.
(h) A. de Meijere, H. Schirmer, M. Duetsch, Angew. Chem., Int. Ed.
Engl. 39 (2000) 3964;
`
(i) J. Barluenga, M. Fernandez-Rodriguez, E. Aguilar, J. Organomet.
Chem. 690 (2005) 539.
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