Ferrocenyl and pyridyl methylenepyrans as potential precursors of organometallic electron-rich extended bipyrans: Synthesis, characterization and crystal structure

Article abstract of DOI:10.1016/j.jorganchem.2009.10.006

Ferrocenyl and pyridyl methylenepyrans were obtained from a Wittig reaction between a pyran phosphorane and ferrocenyl or pyridyl-aldehydes. The nucleophilic nature of the exocyclic C-C bond allowed the formylation of these compounds by a Vilsmeier type reaction. All the new products were characterized by IR spectroscopy, ¹H and ¹³C NMR spectroscopy, mass spectroscopy and (or) elemental analysis. Electrochemistry of representative compounds 2, 10 and 13 was undertaken. In addition, a crystal structure of the ferrocenylpyranylidene aldehyde 5 was described, and the pyrylium character of this compound was specified.

Full text of DOI:10.1016/j.jorganchem.2009.10.006

Journal of Organometallic Chemistry 695 (2010) 235–243
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Ferrocenyl and pyridyl methylenepyrans as potential precursors
of organometallic electron-rich extended bipyrans: Synthesis,
characterization and crystal structure
a
a
b
Fatou Ba a, Francoise Robin-Le Guen a, , Nolwenn Cabon , Pascal Le Poul , Stéphane Golhen ,
*
Nicolas Le Poul c, Bertrand Caro a
a Sciences Chimiques U.M.R. CNRS 6226, I.U.T. de Lannion, B.P. 30219, rue Edouard Branly Lannion Cedex, France
b Sciences Chimiques U.M.R. CNRS 6226, Université de Rennes1, 263 Avenue du Général Leclerc CS 74205, 35042 Rennes Cedex, France
c Laboratoire de Chimie, Electrochimie Moléculaires et Chimie Analytique, U.M.R. CNRS 6521, Université de Bretagne Occidentale, 6 avenue Victor Le Gorgeu
CS 93837 29238 Brest Cedex 3, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Ferrocenyl and pyridyl methylenepyrans were obtained from a Wittig reaction between a pyran phos-
phorane and ferrocenyl or pyridyl-aldehydes. The nucleophilic nature of the exocyclic C–C bond allowed
the formylation of these compounds by a Vilsmeier type reaction. All the new products were character-
ized by IR spectroscopy, 1H and 13C NMR spectroscopy, mass spectroscopy and (or) elemental analysis.
Electrochemistry of representative compounds 2, 10 and 13 was undertaken.
Received 18 June 2009
Received in revised form 29 September
2009
Accepted 1 October 2009
Available online 12 October 2009
In addition, a crystal structure of the ferrocenylpyranylidene aldehyde 5 was described, and the pyry-
lium character of this compound was specified.
Keywords:
Ó 2009 Elsevier B.V. All rights reserved.
Ferrocenyl methylenepyrans
Pyridyl methylenepyrans
Formylation
Electron-rich molecules
1. Introduction
and proteins [9], we have explored the chemistry of unsaturated
chalcogenomethylenepyran Fischer-type carbene complexes
In comparison with their isoelectronic dithiafulvene analogs [1],
which have been extensively used as precursors of extended elec-
tron-rich tetrathiafulvenes [2], chalcogenomethylenepyrans of
type A (Fig. 1) have received relatively scant attention [3]. Never-
theless the chalcogenomethylenepyran core has been punctually
implicated as molecular framework in various domains such as
molecular material science [4], medicinal technology [5], liquid
crystal field [6], nonlinear optic [7], molecular machine [8]. Partic-
ular attention has been devoted to electron-rich tetraphenyldithia-
(R0 = (–CH@CH–)n–C(OCH3)W(CO)5 , X = O, S, Te, n = 1–3, Fig. 1A)
[10]. Simple and efficient routes to these complexes have been
opened using pyrylium salts [10] or methylenechalcogenopyrans
bearing an aldehyde function (R0 = CHO, Fig. 1A) [11]. These
push–pull organometallic molecules which have a noticeable pyry-
lium character have shown their efficiency as NLO phores [11].
They have been advantageously used as precursors of extended
electron-rich bischalcogenopyrans (Fig. 1C) with interesting redox
properties, because calculations have predicted molecular move-
ment upon electrochemical oxidation [12]. More recently, we have
shown that electro or chemical oxidative coupling of methylenepy-
ran substituted by a ferrocenyl group (Fig. 1A, R = Fc) allowed the
reversible formation of diferrocenylbispyrylium salt via a ferro-
cenylpyran radical intermediate. Subsequent reversible deprotona-
tion of this salt afforded an extended electron-rich diferrocenyl
bischalcogenopyran bearing metallocenic group (s) which gave
conjugated diferrocenyl bispyrylium salt by subsequent reversible
oxidation [13]. Having in mind the development of the solid-state
chemistry of extended electron-rich bichalcogenopyrans bearing
metallocenic group (s) or group (s) having a coordination site, we
chose to explore an access to various ferrocenyl methylenepyrans
pyranylidene
B (Fig. 1), a useful precursor of organic one-
dimensional conductor which displays interesting electrical and
magnetic properties [4g,4p].
Curiously, despite the great potential of this class of molecules,
organometallic chalcogenomethylenepyran compounds are rare
and their chemistry and physical properties remain to explore.
In addition to our interest in organometallic heterocyclic pyry-
lium salts as marker for biological molecules such as amino acids
* Corresponding author. Fax: +33 2 96 48 13 20.
E-mail addresses: francoise.le-guen@univ-rennes1.fr (F. Robin-Le Guen), ber-
trand.caro@univ-rennes1.fr (B. Caro).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.10.006

236
F. Ba et al. / Journal of Organometallic Chemistry 695 (2010) 235–243
R
O
R
Ph
Ph
S
Ph
S
R
X
R
α
O
R
O
R
R'
R'
Ph
β
α'
O
O
β'
R'
H
Ph
Ph
O
Fe
Fe
Fe
A
B
C
β'
α'
β'
α'
β'
α'
β
β
β
Ph
Fig. 1. Unsaturated chalcogenopyran compounds.
Ph
Ph
α
α
α
O
O
O
Ph
Ph
Ph
and pyridyl methylenepyrans. Herein, we reported on the forma-
tion and characterization of such compounds using a Wittig syn-
thetic methodology.
2
3
4
Fig. 2. New ferrocenylmethylenepyrans and bismethylenepyran.
2. Results and discussion: synthesis of the pyran compounds
electron-rich molecular structures bearing both pyran and 1,3-
dithiafulvene rings could also be reached from 4 and 1,3-dithiole
Horner–Wittig reagent [1d].
For similar goal, introduction of a formyl group in 1 was
achieved using a Vilsmeier-type formylation (oxalyl chloride–
DMF reagent). The ferrocenylpyranylidene aldehyde 5 was isolated
in good yield (70%) (Scheme 2).
Incorporation of hydroxyl group in electron-rich TTF have at-
tracted considerable interest with the aim of increasing the dimen-
sionality of cation radical salts or charge transfer complexes by
establishment of intermolecular hydrogen bond [18], therefore
alcohol 6 was also synthesized in good yield by reduction of 4
using NaBH4 in ethanol (74% yield) (Scheme 3).
To synthesize new metallocenic heterocyclic compounds, we
have chosen in first to exploit the reactivity in basic medium of
the easy accessible 2,6-diphenyl-4H-pyran-4-yl triphenylphospho-
nium tetrafluoroborate salt [14] with ferrocenecarboxaldehyde
and ferrocene-1,10-dicarboxaldehyde [15]. At ꢀ78 °C, addition of
formylferrocene to a THF solution of the heterocyclic phosphorane,
generated in situ by reaction of the phosphonium salt with n-BuLi
(2.5 M solution in hexane), afforded the ferrocenyl methylenepy-
ran 1 in good yield. A careful control of the temperature is required,
since above ꢀ40 °C (Scheme 1), the phosphorane reacted with the
phosphonium salt and led to a bipyran [14c].
The analogous reaction involving ferrocene-1,10-dicarboxalde-
hyde and two equivalents of the phosphorane have provided
the metallocenic bispyran 2 (Fig. 2) in low yield (20%). Similarly,
the ferrocenylmethylenepyran 3 (Fig. 2) was obtained from the
mono-protected ferrocene-1,10-dicarboxaldehyde [16] (39% yield).
Subsequent acid hydrolysis of the acetal function led to the ferro-
cenylpyran aldehyde 4 in 57% yield (Fig. 2). A more expedient and
efficient route to 4 consisted in using a 1/1 phosphonium salt/fer-
rocene-1,10-dicarboxaldehyde ratio. Under these experimental
conditions, small quantities of the bispyran 2 (Fig. 2) were also
formed (<10%) and 4 was isolated upon chromatographic workup
in an overall improved yield (45%).
Access to more extended
p systems and systems having more
than one ferrocenyl group, was achieved by a reaction between
aldehyde D or E and the pyran phosphorane derivative, respec-
tively (Schemes 4 and 5).
In the first case (aldehyde D), an unseparable mixture of the
ferrocenylmethylenepyran 7 and aldehyde D was obtained. To cir-
cumvent this experimental difficulty, Co2(CO)8 was added to the
mixture to give the expected Co2(CO)6–acetylenic complexes of 7
and D [19], which are easily separated by chromatographic work-
up. By this way, the trinuclear complex 8 was obtained in 74% yield
(Scheme 4).
On the other hand, aldehyde E (mixture of stereoisomers) [20]
gave the diferrocenyl unsaturated pyran 9 in low yield (20%) as
one isomer (Scheme 5).
Unsaturated Fischer-type carbene complexes would be accessi-
ble from a reaction involving the carbanion of Me(OMe)C@W(CO)5
carbene and the formyl group of 4 [11]. Therefore, a route to elec-
tron-rich extended diferrocenyl bispyrans seems open, as it is well
established that unsaturated Fischer carbenes undergo a self-
dimerization reaction under Pd° catalysis [17]. In addition, hybrid
Oxidative coupling of 8 and 9 followed in the later case by a
decomplexation of the dicobalt carbonyl fragment could open a
route to a new class of dendralenes. These cross-conjugated mole-
cules should have possible applications as soliton valves and
switches in molecular electronic devices [21]. Finally, the pyri-
dine–pyran complex 10 was obtained similarly from pyridine car-
boxaldehyde and the phosphorane derivative (85% isolated yield).
Subsequent formylation using Vilsmeier-type reaction afforded
11 in 55% yield (Scheme 6).
Ph
O
Ph
O
H
CH3CN
-
BF4-
PPh3
BF4
+
+
+
PPh3
Ph
Ph
Moreover, to test the coordinative propensity of the pyridine
ring [22], compound 10 was added to a W(CO)5(THF), generated
photochemically from W(CO)6 and THF, to yield the expected
pentacarbonyl complex 12 (57% yield).
O
n-BuLi
THF
-78°C
H
Fe
3. Characterization
Ph
O
α'
β'
3.1. Spectroscopic studies
H
The new ferrocenylpyrans 1, 3, 4, 5, 6, 8, 9 and ferrocenylbispy-
ran 2 were fully characterized by IR, 1H and 13C NMR spectroscopy,
mass spectroscopy, elemental analysis (for 6 and 10) and X-ray
analysis for 5.
The solid-state IR spectra (KBr plates) of the ferrocenylpyran
compounds 1–6, 8, 9 exhibit the typical features previously
α
β
Ph
Fe
1
Scheme 1. Synthesis of ferrocenylmethylenepyran complex.

F. Ba et al. / Journal of Organometallic Chemistry 695 (2010) 235–243
237
-O
Fc
Ph
Ph
Ph
O
O
α'
α'
β'
β'
(COCl)2
DMF
H
H
H
O
O
+
γ
γ
Fc
Fc
α
α
β
β
Ph
Ph
Ph
5
1
Fc = Ferrocenyl group
Scheme 2. Formylation of 1 by (COCl)2DMF reagent.
In addition to the pyran absorption band, supplementary bands
appear at 2819 cmꢀ1 (weak) and 1682 cmꢀ1 (sharp intense) for
aldehyde 4 and at 2755 cmꢀ1 (weak) and 1627 cmꢀ1 (sharp in-
tense) for aldehyde 5 assigned to the C–H and C@O aldehyde
stretching modes, respectively. The difference found between the
OH
O
O
NaBH4
EtOH
H
Fe
Fe
β'
α'
β'
α'
m(C@O) values of 4 and 5 suggests a contribution of the pyrylium res-
β
β
α
Ph
Ph
Ph
α
onance form to the ground state structure of 5, in agreement with
the findings of NMR studies (see below).
O
Ph
The IR spectra of the pyridine methylenepyran compounds 10–
12 display several intense bands in the 1660–1500 cmꢀ1 region,
attributable to the vibration of the C@N of pyridine ring and to
the C@C of the pyran ring. In addition, compound 11 displays the
stretching modes characteristic of the aldehyde function
(2742 cmꢀ1 weak and 1666 cmꢀ1 intense). Finally, consistent with
the presence of a W(CO)5 groups, the IR spectrum of complex 12
exhibits expected intense bands for the carbonyl linked to the
4
6
Scheme 3. Reduction of 4 by NaBH4.
observed for related methylenepyran complexes [10,11]. In partic-
ular, the IR spectra show a medium sharp band in the 1620–
1667 cmꢀ1 region assigned to the C@C stretching mode of the
pyran ring. As expected, supplementary broad band appears at
3331 cmꢀ1 for alcohol 6, which is characteristic of OH intermolec-
ular hydrogen bond. The IR spectrum of the cobalt carbonyl com-
plex 8 displays three intense bands at 2073, 2042 and 2006 cmꢀ1
attributed to the metal carbonyl stretching mode.
tungsten atom at 2069, 1969, 1914, 1913, 1866 cmꢀ1
.
1H and 13C NMR spectra were recorded after recrystallization of
the compounds and their analysis confirms the proposed structures.
For the ferrocenyl complexes, comparison of the 1H and 13C
chemical shift values is in accordance with the electronic influence
Ph
Ph
CHO
C
H
O
O
PPh3
+ D
+
Fe
Fe
Ph
Ph
D
7
Co2(CO)8
Ph
α'
O
Co(CO)3
CHO
(CO)3Co
Fe
Co(CO)3
(CO)3Co
Fe
β'
+
C
H
β
α
Ph
8
Scheme 4. Synthesis of the Co2(CO)6 acetylenic complex 8.
PPh3
Fe
Fe
+
Fe
Fe
H
Ph
O
Ph
H
O
β'
α'
Ph
β
α
E
Ph
O
9
Scheme 5. Access to diferrocenylmethylenepyran 9.

238
F. Ba et al. / Journal of Organometallic Chemistry 695 (2010) 235–243
Ph
H
β'
α'
O
O
(COCl)2
DMF
α
β
Ph
Ph
O
Ph
O
N
α'
β'
O
H
H
11
+
PPh3
N
α
β
Ph
Ph
N
W(CO)5(THF)
Ph
10
β'
α'
H
O
β
α
Ph
N
W(CO)5
12
Scheme 6. Access to pyridylmethylenepyran compounds.
Table 1
Selected chemical shift values for pyran compounds (d ppm, solvent CDCl3).
0
0
Compounds
dC
a
dC
a
dHb
dHb
1
2
3
4
5
6
8
9
149.0
149.0
149.1
150.0
156.1
149.6
151.6
149.6
152.2
157.8
154.1
151.0
151.1
151.6
152.1
157.1
151.8
153.0
151.5
154.1
158.3
156.4
6.30
6.22
6.31
6.32
8.70
6.32
6.26
6.21
6.45
8.45
6.83
6.92
6.82
6.88
6.79
7.23
6.87
6.59
6.84
7.04
6.71
7.31
10
11
12
of the aldehyde function in 5. As stated previously, one can expect
0
0
a deshielding effect for the Hb proton (H ) and the C atom (Ca ) as
a
b
the pyrylium resonance form contributes more to the ground state
structure of the molecule [11c].
0
0
As exemplified in Table 1, the C (Ca ) and Hb (Hb ) atoms of 5
a
resonate at lower field than the analogous atoms in 1, 2, 3, 4, 6,
Fig. 3. ORTEP diagram of compound 5.
0
8, and 9. However the (Hb ) atom is clearly under the anisotropic
influence of the aldehyde function and therefore cannot be taken
into account for comparison. Moreover, it can be noted that a part
of the deshielding effect found for 5 should be the consequence of
the inductive effect of the carbonyl group.
On the other hand, the presence of the aldehyde function on the
sandwich fragment in complex 4 has no detectable influence on
the pyran ring chemical shift values. This observation emphasizes
the lack of electronic communication via the iron atom between
the two cyclopentadienyl rings. Concerning the 1H and 13C chemi-
cal shift values of the pyridyl pyrans 10, 11 and 12 (Table 1), one
can take note of the low deshielding effect of the pyridyl ring (com-
parison with analogous complexes 1 and 5).
Table 2
Selected bond lengths (Å) and angles (°) for compound 5.
C1–C10
1.486(4)
1.384(4)
1.461(4)
1.219(4)
1.338(4)
122.1(3)
120.8(2)
116.1(2)
C3–C4
1.445(4)
1.440(4)
1.341(4)
1.375(3)
1.365(3)
122.8(3)
128.6(3)
C4–C10
C4–C5
C5–C6
C2–O1
C10–C20
C20–O2
C2–C3
C6–O1
C4–C10–C20
C10–C20–O2
C10–C4-C5
C4–C10–C1
C20–C10–C1
the solvent at low temperature. The structure of the organometal-
lic moiety, along with the atom labelling, is presented in Fig. 3. Se-
lected bond lengths and angles are listed in Table 2. Details of the
data collection and refinement are provided in Section 5.
The main feature of the solid-state structure is the low devia-
tion from planarity between the pyran ring and the carbonyl group
(C4–C10–C20–O2 = 10.4(5°), a situation which should allow conju-
gation between the two parts of the molecules. On the other hand,
in order to minimize the steric strain with the pyran ring and the
carbonyl group, the ferrocenyl group deviates from the plane
formed by the methylenepyran moiety. An angle of 53.64(9)° is ob-
served between the mean planes of the pyran and cyclopentadi-
enyl rings. As in other 2,6-diphenylmethylenepyran, the phenyl
0
Again, we observe the deshielding of the C (Ca ) atoms due to
a
0
the presence of an aldehyde function in 11. As in 5, the Hb atom
resonates at low field. Curiously, the electron withdrawing ability
of the carbonyl group has no influence on the chemical shift of
the Hb atom.
Consequently, X-ray analysis was performed in order to gain
more information on the electronic of 5.
3.2. X-ray crystal structure
Crystals suitable for structure determination were grown from
dichloromethane/diethylether solution by slow evaporation of

F. Ba et al. / Journal of Organometallic Chemistry 695 (2010) 235–243
239
rings deviate slightly from the pyran ring (C5–C6–C13–
Ph
Ph
R
R
.
-2e-
C14 = 15.2(5)° and C3–C2–C7–C8 = ꢀ19.5(5°). The iron distances
to the Cp rings and the C–C distances and angles of the Cp lie in
the expected range. On the methylenepyran side, we observe that
the exocyclic bond C4–C10 is 1.384(4) Å long, suggesting a weak
pyrylium character. In fact, exocyclic C–C bond lengths lying in
the range of 1.39–1.40 Å have been found for push–pull methylene
pyran Fischer-type carbene complexes for which, due to the elec-
tron withdrawing effect of the carbene fragment, the ground state
structure are closed to cyanin limit.[10a,10b,10d] On the other
hand, lower values 1.375(5) and 1.352(6) Å) were found for low
conjugated symmetrical bis-methylenepyrans [23,13]. Finally, the
C02–O2 distance (1.219(4) Å) confirmed the low intermolecular
charge transfer between the intracyclic pyran oxygen atom and
the aldehyde carbonyl group.
2
O
2
O
+
Ph
Ph
R= Fc 1
R= pyridyl 10
Ph
Ph
O
R
R
2 e-
O
+
(further oxidations)
Ph
Ph
R= Fc 14
R= pyridyl 15
Scheme 7. Electrochemical behaviour of pyran compounds 1 and 10.
3.3. Electrochemical studies
for tuning the oxidation potential (820 mV), and allowing a dimer-
ization process. Probably, delocalisation of the positive charge
through the phenyl network inhibits this specific reaction.
The redox behaviour of representative compounds ferrocenyl
bispyran 2, pyridyl pyran 10 and phenylpyran 13 [24] (Fig. 1,
R = R0 = Ph) was investigated by cyclic voltammetry in CH2Cl2 in
the presence of Bu4NPF6 as supporting electrolyte, to determine
parameters which lead to the formation of extended bipyran via
a radical cation, as observed for compound 1. The data are collated
in Table 3. For comparison, values obtained for 1 are also reported
[13]. Voltammetric curves are displayed in Supplementary
information.
To pursue the comparison with compound 1, a voltammetric
study of the ferrocenyl bispyran 2 was also performed. On the ano-
dic scan, compound 2 exhibits a chemically reversible (but kineti-
cally slow) system at E1/2(2) = ꢀ0.24 V, followed by irreversible
anodic peaks (Table 3). As for compounds 1 and 10, an irreversible
cathodic peak appears on the reverse scan (ꢀ0.81 V). Interestingly,
this peak appears only if the potential is raised above the second
anodic peak. Also, maintaining the potential at ꢀ0.03 V for few sec-
onds leads to an increase of the cathodic peak suggesting that a
chemical reaction occurred after the second oxidation. The quanti-
tative electrolysis of compound 2 at ꢀ0.20 V shows that the elec-
tron transfer is monoelectronic (n = 1eꢀ) with the formation of a
stable oxidized compound. On the basis of previous work on com-
pound 1 [13], it appears likely that the reversible system at ꢀ0.24 V
peak corresponds to the oxidation of the ferrocenyl moiety of the
bispyran. This allows us to make three remarks by comparison
with compound 1: (i) the reversibility of the first oxidation and
the stability of the oxidized bispyran indicates that dimerization
does not occur at this stage, (ii) the first oxidation potential which
is observed at lower potential than for 1 is consistent with the for-
The compound 1 displays on the anodic scan an irreversible peak
at Epa(1) = ꢀ0.15 V (vs. FeCpþ/FeCp2) followed by two reversible sys-
2
tems (E1/2(2) = 0.12 V and E1/2(3) = 0.28 V). On the reverse scan, an
irreversible peak appears at ꢀ0.76 V. This peak is absent when start-
ing the scan cathodically from E 6 0.20 V. As previously discussed
[13], these observations are consistent with the formation of a ferr-
ocenyl radical cation 1+ꢁ [25], which evolves by dimerization to form
a diferrocenylbispyrylium salt 14 (Scheme 7). This was confirmed by
electrochemical studies performed on compound 14, obtained by
chemical oxidation using ferricinium salt. Indeed, the reduction of
the diferrocenylbispyrylium salt 14 occurs at Epc = ꢀ0.76 V to give
compound 1 by a subsequent C–C bond breaking.
A similar behaviour was observed with the pyridyl pyran com-
pound 10 for which irreversible oxidation at Epa (1) = 0.50 V leads
to the formation of a species irreversibly reduced at ꢀ0.77 V. As de-
scribed for compound 1, it seems likely that the chemical reaction
which follows electrochemical oxidation is the dimerization of
pyrylium radical cation to form a bispyrylium compound 15. The
main difference between 1 and 10 originates from the nature of
the oxidized site which seems to be the ferrocenyl for 1 and the
pyran for 10.
Substituting the pyridyl moiety by a phenyl group gives a differ-
ent situation: the compound 13 shows a reversible system at
E1/2(2) = ꢀ0.32 V. This redox behaviour suggest the absence of
any dimerization from phenylpyrylium radical cation (no EC mech-
anism), in contrast to the pyridyl derivative 10. The oxidized form
of 13, namely 13+, is thus stable. Such behaviour highlights the
importance of the electronic properties of the substituting group
mation of a highly delocalised d–p electron system (iii) the appear-
ance, after the first irreversible oxidation peak, of a reduction peak
(on the reverse scan) suggests that the dioxidized species evolves
by a dimerization process to ferrocenyl pyrylium salts in a similar
way than 1 [26].
This electrochemical study highlights the specificity of ferroce-
nyl-susbstituted pyrans by comparison with dithiafulvene analo-
gous compounds to undergo oxidative dimerization via radical
cation coupling. Interestingly, a deep contrast appears between
the ferrocenylpyran 1 and its isoelectronic ferrocenyl-1,4-substi-
tuted dithiafulvene analog reported by Bryce’s group [27]. What-
ever substituent borne by the dithiole ring (R = H, Me, SMe,
CO2Me), voltammograms of these compounds display two well
separated reversible oxidation waves. The radical cation coupling
is only feasible for the dithiafulvene derivative when using acid,
suggesting that the deprotonation of the dithiolium salt to ex-
tended TTF is the key step for allowing dimerization. This contrasts
with the ferrocenylpyran 1 for which deprotonation is not neces-
sary to undergo dimerization after oxidation [13]. The case of
non-ferrocenyl susbstituted pyran, such as aryl, is also different.
Voltammetric studies of aryl dithiafulvene derivatives reported
few years ago by Lorcy’s group, showed an irreversible oxidation
peak [2d–g,i–k,o]. In this case, the dimerization of the radical cat-
ion gives a dithiolium salt, which leads to a vinylogous TTF by a
deprotonation process. This compound is reversibly oxidized at a
lower potential than the starting 1,4-dithiafulvene.
Table 3
Electrochemical data for pyran and bispyran compounds, (E vs. FeCp2+/FeCp2) in
CH2Cl2 with Bu4NPF6 as supporting electrolyte at 0.1 V sꢀ1 (a) on the reverse cathodic
scan (b) irreversible peak.
(b)
Epc
Epa (1)
ꢀ0.15
E1/2 (2)
E1/2 (3)
1
2
10
13
ꢀ0.76(a)
ꢀ0.81(a)
ꢀ0.77(a)
0.12
0.28
ꢀ0.24
0.85(b)
ꢀ0.32
0.05(b)
0.50

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F. Ba et al. / Journal of Organometallic Chemistry 695 (2010) 235–243
For the ferrocenyl dithiafulvene analogous to compound 2 [27],
the two reversible oxidation waves are followed by an irreversible
peak.
4-yl triphenylphosphonium tetrafluoroborate salt was obtained
from the method previously described [14].
In conclusion, it appears from these electrochemical studies
that the behaviour is fully dependent, but not only, on the substi-
tuting group which can tune (or not) the delocalisation of the cat-
ionic charge on the molecule, thus allowing formation of dimers.
5.2. Crystallographic data
Crystals of 5 suitable for X Ray analysis were obtained by slow
evaporation of a CH2Cl2/Et2O solution at 4 °C. Single crystal was
mounted on a Nonius four-circle diffractometer equipped with a
CCD camera and a graphite monochromated Mo K
source (k = 0.71073 Å) from the Centre de Diffractométrie (CDFIX),
a radiation
4. Concluding remarks
Université de Rennes 1, France.
In summary, new electron-rich ferrocenyl methylenepyrans and
pyridyl methylenepyrans have been prepared from Wittig reaction
of 2,6-diphenyl-4H-pyran-4-yl triphenylphosphonium tetrafluoro-
borate salt with ferrocenyl aldehydes and pyridylcarboxaldehyde.
Similarly, the same reaction performed with ferrocenyldicarbalde-
hyde afforded the first bispyran known today.
The presence of the sandwich fragment should favour the oxi-
dative coupling of these molecules while incorporation of a pyridyl
group into the pyranylidene framework should open a route to a
coordination chemistry of this type of compounds as exemplified
by the complexation of the nitrogen atom of 10 with the pentacar-
bonyl tungsten group.
The electron-rich nature of complexes 1 and 10 allowed the
formylation of the exocyclic C@C bond using a Vilsmeier-type reac-
tion to give aldehydes 5 and 11. The red/ox behaviour of methyle-
nepyrans 1, 2, 10 and 13 was studied by cyclic voltammetry. This
first approach showed that these compounds are readily oxidized
to radical cation or dication, which evolves by dimerization. At-
tempts to isolate the bispyrylium salts and electron-rich extended
bispyrans isoelectronic of vinylogous TTF are underway in our
laboratory.
5.2.1. X-ray crystal data for 5
Data collection was performed at 293(2)K. C29H22FeO2,
M = 458.32, monoclinic, space group P21 /a, a = 7.2729(2) Å,
b = 25.0694(7) Å, c = 11.8922(4) Å, b = 94.613(1)°, V = 2161.25(11)
Å3, T = 293(2) K, Z = 4, dcalcd = 1.409, 7808 structure factors were
collected before merging gave 4408 unique intensities
(Rint = 0.0343). Structure was solved with SHELXS-97 [29]. The refine-
ment of 289 parameters against F2 of unique intensities [2971 ob-
served intensities I > 2r(I)] was performed with SHELXL-97 [29] with
anisotropic thermal parameters for all non-hydrogen atoms.
Hydrogen atoms were added to the structure model on calculated
positions. Final residues R = 0.0474, wR = 0.1177.
5.3. Electrochemical studies
All experiments were performed under an atmosphere of nitro-
gen (in a glovebox) at ambient temperature using a 0.1 M solution
of [NBu4][PF6] in extra-dry CH2Cl2 ([H2O] < 30 ppm, Acros). A three
electrode system was used with a platinum disk, a platinum wire
auxiliary electrode and a platinum wire dipping in a 10 mM elec-
trolytic solution (with supporting electrolyte) of equimolar FcPF6
and Fc as reference electrode. Cyclic voltammetry experiments
5. Experimental
were performed with a
l-AUTOLAB III potentiostat or with an
AUTOLAB PGSTAT 100 potentiostat, monitored by a computer. All
the potential are quoted against the ferrocene–ferricinium couple.
5.1. General procedures
All manipulations were carried out under a nitrogen atmo-
sphere using standard Schlenk techniques. IR spectra were re-
corded on a Perkin–Elmer spectrum1000 FTIR using KBr plates.
All NMR data are reported in ppm (d) relative to tetramethylsil-
ane as external reference. Coupling constants are reported in Hz.
1H and 13C NMR chemical shift assignments are supported by data
obtained from 1H–1H cosy, 1H–13C HMQC and 1H–13C HMBC exper-
iments. Spectra were recorded at room temperature in CDCl3 on a
Bruker DRX 500 spectrometer and a Bruker Advance 400 spectrom-
eter at the ‘‘Service Commun de Recherche de Résonance Magné-
tique Nucléaire et de Résonance Paramagnétique Electronique de
l’Université de Bretagne Occidentale”. Mass spectra or elemental
analyses were performed at the ‘‘Centre Régional de Mesures Phy-
siques de l’Ouest” (CRMPO, University of Rennes). Microanalytical
data were obtained with a Thermo-Finnigan Flasch EA 1112
CHNS/0 analyzer. Mass spectra were obtained with a high resolu-
tion MS/MS Zab spectra Tof micromass.
5.4. General procedure for the Wittig reaction: SYNTHESIS of
methylenepyrans 1, 2, 3, 9, 10
Small excess of n-butyllithium (1.1 equiv.; 2.5 M in hexanes)
was added dropwise at ꢀ78 °C, under a nitrogen atmosphere, to
a degassed solution of 2,6-diphenyl-4H-pyran-4-yl triphenylphos-
phonium tetrafluoroborate salt (1 equiv.) in dry THF. After 5 min,
the suitable metallocenyl aldehyde or pyridine carboxaldehyde
(1 equiv.) was added. The solution was stirred at room tempera-
ture for 1 h and poured into cold water. Extraction with ether
(3 ꢂ 50 mL), drying over MgSO4 and evaporation of the solution
under vacuum gave a solid residue. The residue was purified by
chromatography on silica gel (eluent ether–petroleum ether) to
give the expected pyrans.
5.4.1. Synthesis of ferrocenylpyran 1 (Scheme 1)
1.200 g of tetrafluoroborate phosphonium salt (2.0 mmol),
0.9 mL of n-butyllithium (2.2 mmol) and 0.428 g of ferrocenecarb-
oxaldehyde (2.0 mmol) gave after chromatography on silica gel
(eluant: perolum ether–diethylether 40/60 v/v) 0.556 g of 1 as a
red-orange solid.Yield: 65%, red-orange solid. 1H NMR (500 MHz,
CDCl3): d = 4.16 (s, 5H, C5H5), 4.26 (s, 2H, C5H4), 4.40 (s, 2H,
5.1.1. Materials
Solvents were dried and distilled under dinitrogen by standard
methods prior to use. Reagents were purchased from commercial
suppliers and used without purification. Ferrocene-1,10-dicarbox-
aldehyde was obtained from Ref. [15] and mono-protected ferro-
cene-1,10-dicarboxaldehyde was synthesized as described
previously by Balavoine and coll. [16]. Ferrocenyl acetylene and
the corresponding aldehyde D were prepared according to Ref.
[28]. Diferrocenylcarboxaldehyde E was synthesized using the
method described by Peris and coll. [20]. 2,6-Diphenyl-4H-pyran-
0
C5H4), 5.59 (s, 1H, CH), 6.30 (s, 1H, Hb ), 6.92 (s, 1H, Hb), 7.43 (m,
6H, HPh(meta and para)), 7.75 (d, J = 7.5 Hz, 2H, HPh(ortho)), 7.80 (d, J =
8.0 Hz, 2H, HPh(ortho)) ppm. 13C NMR (125 MHz, CDCl3): d = 68.2;
0
68.8 (C5H4), 69.1 (C5H5), 84.0 (CFc(quat)), 103.0 (Cb ), 108.4 (Cb),
111.6 (CH), 124.3;124.7 (CPh(ortho)), 128.5;128.9 (CPh(meta and para)),
0
134.2 (C ), 139.2 (CPh(quat)), 149.0 (Ca ), 151.0 (C ) ppm. IR (KBr):
c
a

F. Ba et al. / Journal of Organometallic Chemistry 695 (2010) 235–243
241
= 1658, 1493, 1445, 1278, 809, 760, 689 cmꢀ1. HRMS (ESI): calcd.
for C28H22FeO: 430.1020; found: 430.1007.
5.4.5. Formylation of 1: synthesis of the ferrocenyl formyl
methylenepyran 5 (Scheme 2)
ꢀ
m
(0.06 mL, 0.70 mmol) of (COCl)2 was added under nitrogen
dropwise to 5 mL of cooled DMF (0 °C). The mixture was stirred
5.4.2. Synthesis of ferrocenylbispyran 2 (Fig. 2)
for 15 min. Methylenepyran
1
was then added (0.200 g,
1.200 g of tetrafluoroborate phosphonium salt (2.0 mmol),
0.9 mL of n-butyllithium (2.2 mmol) and 0.242 g of ferrocene-
1,10-dicarboxaldehyde (1.0 mmol) gave after chromatography (elu-
ent: petroleum ether–diethylether 65/35 v/v) 0.134 g of an orange
solid in low yield.Yield: 20%, red-orange solid. 1H NMR (500 MHz,
CDCl3): d = 4.28 (s, 4H, C5H4), 4.46 (s, 4H, C5H4), 5.46 (s, 2H, CH),
0.46 mmol) and the mixture warmed to room temperature and
stirred for 1 h. The solution was poured into water and extracted
with diethylether (3 ꢂ 50 mL). The organic phase was washed with
Na2CO3 solution in water, dried over MgSO4 and evaporated under
vacuum. The solid was then dissolved in petroleum ether/diethyl-
ether mixture and the obtained solution was cooled. Compound 5
was isolated as an orange microcrystalline solid (0.165 g, 77%
yield).1H NMR (500 MHz, CDCl3): d = 4.16 (s, 5H, C5H5), 4.23 (s,
2H, C5H4), 4.37 (s, 2H, C5H4), 7.23 (d, J = 1.7 Hz, 1H, Hb), 7.48 (m,
6H, HPh(meta and para)), 7.77 (m, 2H, HPh(ortho)), 7.92 (m, 2H, HPh(ortho)),
0
6.22 (s, 2H, Hb ), 6.82 (s, 2H, Hb), 7.29 (m, 8H, HPh(meta)), 7.34 (t,
J = 7.0 Hz, 4H, HPh(para)), 7.50 (d, J = 6.1 Hz, 4H, HPh(ortho)), 7.65 (d,
J = 7.0 Hz, 4H, HPh(ortho)
)
ppm. 13C NMR (125 MHz, CDCl3):
0
d = 69.0;69.1 (C5H4), 85.1 (CFc(quat)), 103.0 (Cb ), 108.5 (Cb), 110.8
(CH), 124.1; 124.5 (CPh(ortho)), 128.3; 128.4 (CPh(meta)), 127.5;128.7
8.70 (d, J = 1.7 Hz, 1H, Hb ), 10.25 (s, 1H, CHO) ppm. 13C NMR
0
0
(CPh(para)), 133.3; 133.7 (CPh(quat)), 149.0 (Ca ), 151.1 (C ) ppm. IR
a
(KBr):
= 1654, 1495, 1446, 1281, 946, 758, 689 cmꢀ1. HRMS
(125 MHz, CDCl3): d = 67.5 (C5H4), 69.0 (C5H5), 70.0 (C5H4), 86.0
ꢀ
m
0
(CFc(quat)), 105.3 (Cb ), 106.3 (Cb), 126.0; 126.1 (CPh(ortho)), 129.7
(ESI): calcd. for C46H34FeO2: 674.1908; found: 674.1899.
(CPh(meta)), 130.9; 131.0 (CPh(para)), 134.1 (CPh(quat)), 140.2(C ),
c
ꢀ
m = 2755,
0
156.1 (Ca ), 157.1 (C ), 191.6 (CHO) ppm. IR (KBr):
a
1663, 1627, 1577, 1522, 1103, 938, 765, 680 cmꢀ1. HRMS (ESI):
calcd. for C29H22FeO2: 458.0969; found: 458.0969. C29H22FeO2
(458.15): calcd. C, 76.00; H, 4.84; found: C, 76.57; H 4.85.
5.4.3. Synthesis of ferrocenylpyran 3 (Fig. 2)
1.200 g of tetrafluoroborate phosphonium salt (2.0 mmol),
0.9 mL of n-butyllithium (2.2 mmol) and 0.572 g of ferrocene-1-
formyl-1,3-dioxolane (2.0 mmol) afforded after chromatography
on silica gel (eluant: petroleum ether–diethylether 55/45 v/v)
0.450 g of a red-orange solid.
5.4.6. NaBH4 reduction of aldehyde 4: synthesis of the alcohol 6
(Scheme 3)
Yield: 45%, red-orange solid. 1H NMR (500 MHz, CDCl3): d = 3.92
(t, J = 3.0 Hz, 2H, CH2), 4.02 (t, J = 3.0 Hz, 2H, CH2), 4.17 (t, J = 1.5 Hz,
2H, C5H4), 4.29 (t, J = 1.5 Hz, 2H, C5H4), 4.31 (t, J = 1.5 Hz, 2H, C5H4),
4.44 (t, J = 1.5 Hz, 2H, C5H4), 5.59 (s, 1H, CH), 5.75 (s, 1H, CH), 6.31
NaBH4 (0.049 g, 1.31 mmol) was added to a solution of alde-
hyde 4 (0.500 g, 1.09 mmol) in 15 mL of ethanol. The solution
was stirred until the starting material had disappeared as indicated
by TLC. The mixture was poured into water and extracted with
diethylether. After drying over MgSO4 concentration of the solu-
tion under vacuum, chromatographic work up (silica gel; eluant:
petroleum–ether–diethylether 70/30 v/v) afforded an orange solid
(0.370 g, yield: 74%).1H NMR (500 MHz, CDCl3): d = 1.75 (t,
J = 5.2 Hz, 1H, CH2OH), 4.17 (s, 2H, C5H4), 4.24 (s, 2H, C5H4), 4.29
(s, 2H, C5H4), 4.35 (d, J = 5.2 Hz, 2H, CH2OH), 4.42 (s, 2H, C5H4),
0
(d, J = 1.5 Hz, 1H, Hb ), 6.88 (d, J = 1.5 Hz, 1H, Hb), 7.43 (m, 6H,
HPh(meta
J = 7.0 Hz, 2H, HPh(ortho)
para)), 7.75 (d, J = 7.5 Hz, 2H, HPh(ortho)), 7.80 (d,
and
)
ppm. 13C NMR (125 MHz, CDCl3):
d = 65.2 (CH2), 65.3 (CH2), 67.8; 69.2 (C5H4), 84.4 (CFc(quat)), 84.6
0
(CFc(quat)), 102.8 (CH), 103.0 (Cb ), 108.5 (Cb), 111.3 (CH), 124.3;
124.7 (CPh(ortho)), 128.6–129.0 (CPh(meta
para)), 133.8 (CPh(quat)),
and
0
149.1 (Ca ), 151.6 (C ) ppm. HRMS (ESI): calcd. for C31H26FeO3:
a
0
5.55 (s, 1H, CH), 6.32 (s, J = 1.8 Hz, 1H, Hb ), 6.87 (s, J = 1.6 Hz, 1H,
502.1231; found: 502.1192, calcd. for [MꢀCH2CH2O+]: 458.0969;
.
Hb), 7.36 (m, 2H, HPh(para)), 7.43 (m, 4H, HPh(meta)), 7.75 (d,
J = 7.2 Hz, 2H, HPh(ortho)), 7.79 (d, J = 7.1 Hz, 2H, HPh(ortho)) ppm.
13C NMR (125 MHz, CDCl3): d = 60.7 (CH2OH), 68.3;68.5 (C5H4),
found: 458.0949.
0
5.4.4. Synthesis of the aldehyde ferrocenylpyran 4 (Fig. 2)
68.6;69.2 (C5H4), 84.2 (CFc(quat)), 89.2 (CFc(quat)), 102.6 (Cb ), 108.2
From compound 3:
A
solution of
3
in CH2Cl2 (0.500 g,
(Cb), 110.1 (CH), 124.3; 124.7 (CPh(ortho)), 128.6; 128.8 (CPh(meta)),
9.96 ꢂ 10ꢀ4 mol) is warmed at 60 °C. 0.171 g of paratoluenesulfon-
ic acid was then added and stirred until the starting material had
disappeared as indicated by TLC. The mixture was poured on cold
water. After extraction with ether (3 ꢂ 50 mL) drying over MgSO4,
evaporation of the solution under vacuum gave a solid residue. The
residue was purified by chromatography on silica gel (petroleum
ether–diethylether 40/60 v/v) to afford 0.270 g of 4 (yield 60%).
From ferrocene-1,10-dicarboxaldehyde: 1.200 g of tetrafluoro-
borate phosphonium salt (2.0 mmol), 0.9 mL of n-butyllithium
(2.2 mmol) and 0.484 g of ferrocene-1,10-dicarboxaldehyde
(2.0 mmol) gave 0.129 g of 2 (yield: 10 %) and 0.412 g of the ex-
128.0; 129.1 (CPh(para)), 133.4;133.6 (CPh(quat)), 149.6 (C ), 151.8
a
ꢀ
(C ) ppm. IR (KBr):
m
= 3331, 1663, 1493, 1446, 1285, 1234, 1075,
a
1026, 946, 927, 818, 691 cmꢀ1. HRMS (ESI): calcd. for C28H22FeO:
460.1125; found: 460.1115. C28H22FeO2 (460.30) calcd: C, 75.66,
H ,5.25; found: C, 75.66, H, 5.86.
5.4.7. Synthesis of the ferrocenyl methylenepyran acetylenic Co2(CO)6
complex 8 (Scheme 4)
A schlenk tube was charged with 2,6-diphenyl-4H-pyran-4-yl
triphenylphosphonium tetrafluoroborate salt (1.200 g, 2.0 mmol)
and 20 mL of degassed THF at ꢀ78 °C. n-Butyllithium was added
(0.9 mL, 2.2 mmol) and the solution was stirred for 5 min. The
aldehyde D (0.476 g, 2.0 mmol) was added and the solution was
warmed to room temperature and stirred for 1 h. 0.683 g of
Co2(CO)8 (2.0 mmol) was added to the reaction mixture. After
1 h, the mixture was poured into water. Extraction with diethyl-
ether, drying over MgSO4 and evaporation of the solvent under
vacuum afforded a solid residue. Chromatographic work up on sil-
ica gel yield complex 8 as a green solid (eluent: petroleum ether–
diethylether 90/10 v/v, 1.090 g yield: 74%). A blue solid was also
isolated (0.073 g yield 7%). 1H NMR spectrum confirms the com-
plexation of aldehyde D with Co2(CO)6.1H NMR (500 MHz, CDCl3):
d = 4.26 (s, 5H, C5H5), 4.40–4.49 (s, 4H, C5H4), 6.26 (s, 1H, CH), 6.59
(s, 1H, Hb), 7.08 (s, 1H, Hb), 7.48 (m, 6H, HPh(meta and para)), 7.83 (s,
pected compound
d = 4.36 (t, J = 1.5 Hz, 2H, C5H4), 4.50 (t, J = 1.5 Hz, 2H, C5H4), 4.58
(t, J = 1.5 Hz, 2H, C5H4), 4.78 (t, J = 2.0 Hz, 2H, C5H4), 5.46 (s, 1H,
4
(yield: 45%).1H NMR (500 MHz, CDCl3):
0
CH), 6.32 (d, J = 1.5 Hz, 1H, Hb ), 6.79 (d, J = 1.5 Hz, 1H, Hb), 7.45
(m, 6H, HPh(meta
para)), 7.74 (d, J = 7.0 Hz, 2H, HPh(ortho)), 7.76
and
(d, J = 7.0 Hz, 2H, HPh(ortho)), 9.93 (s, 1H, CHO) ppm. 13C NMR
(125 MHz, CDCl3): d = 69.2;74.5 (C5H4), 85.2; 86.5 (CFc(quat)), 102.5
0
(Cb ), 108.2 (Cb), 109.5 (CH), 124.4; 124.8 (CPh(ortho)), 128.6;128.7
0
(CPh(meta)), 128.9;129.3 (CPh(para)), 133.3 (CPh(quat)), 150.0 (Ca ),
ꢀ
152.1 (C ), 193.7 (CHO) ppm. IR (KBr):
m
= 2819, 1681, 1661,
a
1494, 1457, 1282, 1241, 767, 693 cmꢀ1. HRMS (ESI): calcd. for
C28H22FeO2: 458.0969; found: 458.1012, calcd. for [MꢀCO+]:
430.1020; found: 430.1040. C29H22FeO2: (458.15).

242
F. Ba et al. / Journal of Organometallic Chemistry 695 (2010) 235–243
4H, HPh(ortho)) ppm. 13C NMR (125 MHz, CDCl3): d = 68.4;68.5
schlenk tube charged with 0.995 g of 11. The solution was stirred
over 12 h. Concentration of the solvent under vacuum afforded an
orange solid which was recrystallized in CH2Cl2 (1.100 g, yellow
solid, yield: 57%).1H NMR (500 MHz, CDCl3): d = 5.90 (s, 1H, CH),
0
(C5H4), 69.6 (C5H5), 86.9 (CFc(quat)), 87.6 (CPh(quat)), 106.6 (Cb ),
109.1 (Cb), 111.4 (CH), 125.0 (CPh(meta
para)), 133.0 (CPh(quat)),
and
0
137.5 (C ), 151.6 (Ca ), 153.0 (C ), 184.2;200.4 (CO) ppm. IR
c
a
ꢀ
0
(KBr):
m
= 2073, 2042, 2006, 1652, 1597, 1578, 1543, 1493, 1448,
6.83 (s, 1H, Hb ), 7.31 (s, 1H, Hb), 7.37 (d, J = 5.9 Hz, 2H, Hpyrid),
1106, 935, 763 cmꢀ1
.
HRMS (ESI): calcd. for C36H22FeO7Co2:
7.53 (m, 6H, HPh(meta
7.96 (d, J = 7.6 Hz, 2H, HPh(ortho)), 8.68 (d, J = 5.9 Hz, 2H, Hpyrid)
para)), 7.90 (d, J = 7.6 Hz, 2H, HPh(ortho)),
and
739.9378; found: 739.9398, calcd. for [M+H+]: 740.9457; found:
740.9449.
13
0
ppm.
C NMR (125 MHz, CDCl3): d = 102.6 (Cb ), 109.6 (Cb),
110.2 (CH), 124.0 (Cpyrid), 125.7; 126.2 (CPh(ortho)), 129.6–132.8
(CPh(meta para)), 133.4; 133.6 (CPh(quat)), 148.5 (Cpyrid), 154.1
5.4.8. Synthesis of ferrocenylpyran 9 (Scheme 5)
and
0.274 g of tetrafluoroborate phosphonium salt (4.7 mmol),
0.9 mL of n-butyllithium (5.6 mmol) and 0.200 g of diferrocenecar-
boxaldehyde (4.7 mmol) gave after chromatography (eluant:
petroleum ether–diethylether 70/30 v/v) 0.077 g of a red-orange
solid (yield: 25%).1H NMR (500 MHz, CDCl3): d = 4.03 (s, 2H,
C5H4), 4.08 (s, 5H, C5H5), 4.10 (s, 2H, C5H4), 4.22 (s, 2H, C5H4),
4.32 (s, 2H, C5H4), 4.35 (s, 2H, C5H4), 4.36 (s, 2H, C5H4), 5.46 (s,
(C ), 156.4 (C ), 156.6 (Cpyrid), 199.8; 202.6 (CO) ppm. IR (KBr):
a a
ꢀ
m
= 2069, 1969, 1914, 1913, 1866, 1654, 1578, 1560, 768,
692 cmꢀ1. HRMS (ESI): calcd. for C28H17NO6W: 647.0565; found:
647.0570.
Acknowledgments
0
1H, CH), 6.21 (s, 1H, Hb ), 6.36 (d, J = 6.0 Hz, 2H, CH@CH), 6.84 (s,
The authors thank the CNRS and the University of Rennes 1 for
financial support. We are grateful to N. Kervarec, S. Cerantola and
G. Simon for recording NMR spectra (Service commun de recherche
de RMN et de RPE, Université de Bretagne Occidentale).
1H, Hb), 7.37–7.43 (m, 6H, HPh(meta and para)), 7.67 (m, 2H, HPh(ortho)),
7.77 (m, 2H, HPh(ortho)) ppm. 13C NMR (125 MHz, CDCl3): d = 68.2;
68.8 (C5H4), 69.0 (C5H4), 69.1 (C5H5), 69.2;69.4 (C5H4), 84.1
0
(CFc(quat)), 85.1 (CFc(quat)), 86.0 (CFc(quat)), 103.0 (Cb ), 108.6 (Cb),
111.3 (CH), 124.5; 124.6 (CPh(ortho)), 128.0; 129.0 (CPh(meta and para)),
Appendix A. Supplementary data
ꢀ
), 149.6 (Ca ), 151.5 (C ) ppm. IR (KBr): m = 1660, 1495,
a
0
134.0 (C
Ph(quat)
1440, 1269, 811, 754, 679 cmꢀ1. HRMS (ESI): calcd. for C40H32Fe2O:
CCDC 732060 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via http://www.ccdc.ca-
m.ac.uk/data_request/cif. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/
j.jorganchem.2009.10.006.
640.1151; found: 640.1179.
5.4.9. Synthesis of pyridyl pyran 10 (Scheme 6)
1.200 g of tetrafluoroborate phosphonium salt (2.0 mmol),
0.9 mL of n-butyllithium (2.2 mmol) and 0.19 mL of pyridinecar-
boxaldehyde (2.0 mmol) gave 0.549 g of a yellow solid (yield:
85%).1H NMR (500 MHz, CDCl3): d = 5.78 (s, 1H, CH), 6.45 (d,
0
J = 1.7 Hz, 1H, Hb ), 7.04 (d, J = 1.7 Hz, 1H, Hb), 7.24 (d, J = 4.7 Hz,
References
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and
c
0
a
ꢀ
ppm. IR (KBr):
m
= 1663, 1658, 1579, 1489, 1445, 1281, 1075,
916, 761, 687 cmꢀ1. HRMS (ESI): calcd. for C23H17NO: 323.1310;
found: 323.1304. C23H17NO (323.05): calcd: C, 85.42; H, 5.30; N,
4.33; found: C, 85.02; H, 5.18; N, 3.91.
5.4.10. Formylation of 10 – synthesis of the pyridyl-methylenepyran
aldehyde 11 (Scheme 6)
As described above, 0.06 mL (0.75 mmol) of oxalyl chloride,
5 mL of DMF and 0.161 g of 10 afforded the expected compound
11 as a brown solid (0.122 g, 70% yield).1H NMR (500 MHz,
CDCl3): 6.71 (s, 1H, Hb), 7.28 (d, J = 4.9 Hz, 2H, Hpyrid), 7.40 (m,
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and
0
J = 7.0 Hz, 2H, HPh(ortho)), 8.45 (s, 1H, Hb ), 8.70 (d, J = 4.9 Hz, 2H,
Hpyrid), 9.91 (s, 1H, CHO) ppm. 13C NMR (125 MHz, CDCl3):
0
d = 103.3 (Cb ), 104.9 (Cb), 118.7 (Cquat), 125.4 (CPh(ortho)), 125.8
(CPh(ortho)), 128.5 (CPh(meta
para)), 131.6;132.0 (CPh(quat)), 145.6
and
(Cpyrid), 150.4 (Cpyrid), 157.8 (C0 ), 158.3 (C ), 187.5 (CHO) ppm.
a
a
ꢀ
m = 2742, 1666, 1622, 1589, 1445, 1228, 1078, 916,
IR (KBr):
763, 689 cmꢀ1. HRMS (ESI): calcd. for C24H17NO2: 351.1259;
found: 351.1259, calcd. for [MꢀH+]: 350.1180; found: 350.1196;
calcd. for [MꢀCO+]: 323.1310 ; found: 323.1305.
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