Enamine-functionalized oligopyridines as convenient intermediates for the synthesis of carbaldehyde derivatives

Article abstract of DOI:10.1055/s-2003-37658

A series of enamine-substituted bipyridine, biquinoline and o-phenanthroline chromophores has been synthesized and fully characterized. The para regioselectivity of the functionalization is discussed on the basis of 2D NOESY correlation and X-ray diffraction analysis. Absorption and emission spectroscopic studies allow a comparison of the acceptor strength of the heterocyclic core (biquinoline > phenanthroline > bipyridine). These enamine derivatives are key intermediates for a straightforward preparation of the corresponding dicarbaldehyde-bisimine compounds.

Full text of DOI:10.1055/s-2003-37658

PAPER
577
Enamine-Functionalized Oligopyridines as Convenient Intermediates for the
Synthesis of Carbaldehyde Derivatives
a
a
a
a
a
b
C
L
onvenient Inte
y
rmediates fo
d
r
the Synthe
s
i
is of
C
e
arbaldehyde
Deri
V
vatives iau, Katell Sénéchal, Olivier Maury, Jean-Paul Guégan, Philippe Dupau, Loïc Toupet,
a
Hubert Le Bozec*
a
Organométalliques et Catalyse : Chimie et Electrochimie Moléculaires, UMR 6509 CNRS-Université de Rennes 1, Institut de Chimie de
Rennes, Campus de Beaulieu, 35042 Rennes Cedex, France
Fax +33(2)99286939; E-mail: lebozec@univ-rennes1.fr
b
Groupe de la Matière Condensée et Matériau, UMR 6626 CNRS-Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex,
France
Received 27 September 2002; revised 23 December 2002
ries of methyl substituted bis-heterocyclic ligands such as
,4′-dimethyl[2,2′]bipyridine (1a), 4,4′,6,6′-tetrameth-
yl[2,2′]bipyridine (2a), 4,4′-dimethyl[3,3′]dimethylene-
(3a) and 3,4,7,8-tetramethyl-o-
Abstract: A series of enamine-substituted bipyridine, biquinoline
and o-phenanthroline chromophores has been synthesized and fully
characterized. The para regioselectivity of the functionalization is
4
discussed on the basis of 2D NOESY correlation and X-ray diffrac- biquinoline
tion analysis. Absorption and emission spectroscopic studies allow phenanthroline (4a). The 4,4′-dimethyl annelated biquin-
a comparison of the acceptor strength of the heterocyclic core
oline 3a was first prepared by using a Friedländer-type
condensation between 2-aminoacetophenone (2 equiv)
and cyclohexanedione in refluxing 2-methoxyethanol
(biquinoline > phenanthroline > bipyridine). These enamine deriv-
atives are key intermediates for a straightforward preparation of the
corresponding dicarbaldehyde-bisimine compounds.
(
Scheme 1). It is noteworthy that this reaction, generally
Key words: heterocycles, imines, ligands, aldehydes, chro-
mophores
11
carried out with aminobenzaldehyde, can be applied to
the corresponding acetophenone.
Heterocyclic bisimines are widely used ligands for metal
ion complexation and powerful building blocks for the
O
1
2-methoxyethanol
2
+
NH2
synthesis of molecular materials with a wide range of
∆, 48 h
O
O
N
N
2
physical properties, such as electron transfer, photovolta-
3a (79%)
3
4
5
6
ism, light-harvesting, magnetic or nonlinear optical
NLO) properties. In the latter field, we have demonstrat- Scheme 1
(
ed that 4,4′-functionalized-2,2′-bipyridines are efficient
chromophores for the design of dipolar and octupolar
NLO-phores. Carbaldehyde-substituted oligopyridines
can be considered as useful precursors for the elaboration
of these chromophores. To this end, we preliminarily re-
ported a convenient two-step method for the preparation
Treatment of 1a–4a with the commercially available
Bredereck's reagent’ (tert-butoxybisdimethylami-
nomethane) in refluxing DMF led to the formation of the
7
‘
enamines 1b–4b in good to excellent yields (84 and 95%)
(
Scheme 2). The same reaction was successfully applied
of 4,4′-dicarbaldehyde-2,2′-bipyridine via enamination of
to the 4-methyl-4′-alkenyl-2,2′-bipyridines 5a–6a which
gave rise to the corresponding mono-enamine derivatives
8
4
,4′-dimethyl-2,2′-bipyridine. We describe here the gen-
eralization of this methodology to different bisimine
ligands such as bipyridines, annelated biquinolines and o-
phenanthrolines. The regioselectivity of the enamination
is discussed on the basis of 2D NMR studies or X-ray dif-
fraction analysis. The absorption and emission spectro-
scopic properties of the enamine intermediates, which can
be regarded as simple push-pull chromophores in which
5
b–6b in 82–85% yields.
These compounds were fully characterized by means of
NMR, high-resolution mass spectrometry, absorption and
emission spectroscopies. The E configuration of the
enamine double bond was unambiguously established by
1
H NMR, based on the determination of the coupling con-
3
stant J
= 14 Hz (Table 1).
CH=CH
the donor (NMe ) and the acceptor (pyridine) moieties are
2
connected through an alkenyl bridge, is also discussed.
It is worth noting that in the case of 2a and 4a containing
four methyl groups, the enamination regioselectively oc-
cured at the para position of the pyridine rings. Even un-
der more drastic conditions (large excess of Bredereck's
Reagent, longer reaction times) further functionalisation
of the other methyl groups could not be detected. The
highly selective nature of this reaction was clearly evi-
denced by 2D NOESY correlation and X-ray diffraction
analysis in the case of 2b, and 4b (vide supra) respective-
ly. The 2D NOESY correlation spectrum of 2b exhibits
The transformation of an activated methyl group into an
enamine by means of formamide acetals or aminals is well
9
established. This reaction has been first developed by
10
Bredereck with methyl-substituted heteroarenes. Based
on this results, we have extended the methodology to a se-
Synthesis 2003, No. 4, Print: 18 03 2003.
Art Id.1437-210X,E;2003,0,04,0577,0583,ftx,en;T10502SS.pdf.
©
Georg Thieme Verlag Stuttgart · New York
ISSN 0039-7881

5
78
L. Viau et al.
PAPER
Me
2
N
not observed
H7 NMe2
R
N
R
Me2N
H7
N
H3
CH3
H5
H3C
H5
H3
N
N
N
N
R
R
H5
H3C
H5
CH3
1a; R = H
1b; R = H (95%)
2b; R = Me (87%)
NMe
2
2
N
N
2a; R = Me
H3
H3
H7
NMe2
Me2N
H7
Me
2
N
NMe
2b
observed
NOE correlation
other possible regioisomer
N
N
N
N
Figure 1 Determination of the regioselectivity by means of the
NOE correlation.
3a
3b (84%)
tBuOCH(NMe
Me
2 2
)
2
N
NMe
2
DMF, 80 °C
unambiguously confirmed by the coupling of the remain-
ing methyl group with only H , and not with H .
N
N
N
N
4a
4b (94%)
5
3
2
Me N
Compounds 1b and 4b gave suitable crystals for X-ray
diffraction analysis. ORTEP drawings are depicted in
Figures 2 and 3, respectively. Crystal data and refinement
parameters are listed in Table 2. The bipyridine derivative
N
N
N
N
5
6
a; D = NMe
a; D =OOct
2
5b (85%)
b (82%)
1
b adopts a classical transoid arrangement due to the re-
6
pulsion of the nitrogen lone pairs with a symmetry centre
D
D
7c,12
in the middle of the C(1)–C(1_3) bond.
The E config-
uration of the enamine double bonds is clearly confirmed
for both compounds, as well as the selective para func-
tionalization in 4b. The C=C double bonds of the enamine
moieties in 1b and 4b adopt an s-cis conformation with re-
spect to C3–C4 and C7–C8/C4–C3 respectively. This
contrasts with the s-trans conformation recently reported
for 4,4′-dibutylaminostyryl[2,2′]bipyridine.7 In 1b, the
enamine double bonds lie perfectly in the plane of the py-
ridine ring, whereas the structure of 4b reveals a substan-
tial twist with dihedral angles between the double bonds
and the phenanthroline plane of ca. 25 and 50°, one enam-
ine group being more distorted than the other. These dis-
tortions could be explained by steric hindrance between
either the phenanthroline bridging protons (H , H ) or the
Scheme 2
Table 1 Selected NMR, UV-Visible and Fluorescence Data
–1
Ligand JCH=CH/Hz λmax/nm
ε/L⋅mol
⋅
λem/nm
Stokes
Shift/nm
c
cm-
1
1b
2b
3b
4b
13.6
13.7
13.8
13.8
345
340
385
38000
31000
14000
449
453
519
470
104
113
134
102
352 (368) 25500
5
6
methyl groups (C19, C20) with the enamine vinylic pro-
tons. For both compounds, classical bond lengths of about
through space correlation between the vinylic H proton 1.34 for the enamine double bonds (1b, C6–C7; 4b, C15–
7
and the pyridine H and H protons (Figure 1), strongly C16/C17–C18) and 1.46 for the C6–C3 (1b) and C15–
3
5
suggesting that the functionalization occurs selectively in C4/C17–C7 (4b) are observed.
the para position. Furthermore, this regioselectivity was
Figure 2 ORTEP drawing of compound 1b. Selected bond lengths (): N2–C7, 1.357(4); C7–C6, 1.339(4); C6–C3, 1.458(4); C1–C1_3,
1.493(6).
Synthesis 2003, No. 4, 577–583 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Convenient Intermediates for the Synthesis of Carbaldehyde Derivatives
579
the acceptor strengths in the order biquinoline > phenan-
throline > bipyridine. Photoluminescence is observed for
the four compounds in dichloromethane solution at room
temperature (Table 1 and Figure 4). A substantial red shift
in the emission wavelength of the biquinoline derivative
3
b is also found when compared to those of 1b and 2b
(
∆λ = 70 nm) and 4b (∆λ = 50 nm).
Compounds 1b–5b were then converted to their carbalde-
hyde derivatives 1c–5c in good yield (60 to 80%) upon
15
oxidative cleavage of the enamine double bonds by so-
dium periodate in aqueous THF solution at 40 °C
(
Scheme 3). The overall yields of this two steps synthesis
from dimethyl-substituted bisimines are fairly good, from
0 to 70%. Classically, the formation of such 4,4′-dicar-
Figure 3 ORTEP drawing of compound 4b. Selected bond lengths
(
): N11–C16, 1.373(4); N12–C18, 1.347(4); C16–C15, 1.332(4);
C18–C17, 1.348(4); C15–C4, 1.474(4); C17–C7, 1.450(5); C11–C12,
.457(4)
5
badehyde oligopyridines from the corresponding dimeth-
yl precursors requires either: (i) a multistep procedure
involving oxidation of the methyl fragments to carboxylic
acids, esterification, reduction to alcohol and finally con-
trolled oxidation to aldehyde; or (ii) direct oxidation by
selenium dioxide17 or benzeneselenic anhydride. How-
ever, these two methods cannot be applied to the synthesis
of methylated derivatives such as 2c, due to the poor regi-
oselectivity of the oxidation processes. A comparison of
the different synthetic methods (Table 3) shows that our
alternative methodology is more efficient in the case of bi-
pyridines and gives comparable yields in the case of
biquinolines and o-phenanthrolines. Moreover, the use of
highly toxic selenium reagents is avoided. Finally, the
enamine formation step allows the regioselective synthe-
sis of derivatives 2c and 4c, without undesirable transfor-
mation of the other methyl substituents.
1
The UV-visible spectra of 1b–4b recorded in dichlo-
romethane (Table 1 and Figure 4) exhibit absorption
bands that are sensitive to the nature of the bisimine moi-
eties. The optical spectra of the push-pull bipyridines 1b
and 2b are characterized by an intense intraligand charge
transfer transition (ICT) at ca. 340 nm. The phenanthro-
line derivative 4b has a slightly red-shifted ICT band
when compared to 1b and 2b. Noteworthy is the substan-
tial bathochromic shift of the charge-transfer transition in
1
6
18
19
3
b centered at 385 nm, which is consistent with the lower
1
3
π* level in 2,2′-biquinolines. This very broad band
overlaps with another low-energy band assigned to the π–
π* biquinoline excitation (λ = 350 nm), a transition which
is also expected to occur in this region. The bathochro-
mic shift allows a rough estimate of the relative values of
1
4
H
Me2N
R
O
R
N
N
N
N
R
R
O
1
b; R = H
1
2
c; R = H (80%)
H
c; R = Me (60%)
NMe2
NMe2
2
b; R = Me
Me2N
H
H
O
O
N
N
N
N
3b
NaIO4/THF
NMe2
3c (58%)
Me2N
Me2N
H
H
O
O
N
N
N
N
N
N
4b
4c (65%)
H
O
N
N
5b
5c (64%)
NMe2
NMe2
Scheme 3
Synthesis 2003, No. 4, 577–583 ISSN 0039-7881 © Thieme Stuttgart · New York

5
80
L. Viau et al.
PAPER
Table 2 Selected Crystallographic Data and Collection Parameters
for Compounds 1b and 4b
Compounds
Formula
M/
1b
4b
C H N
C H N
4
18
22
4
22 26
294.4
346.47
Crystal size/mm
Color
0.45 × 0.25 × 0.21
Yellow
0.42 × 0.35 × 0.35
Yellow-green
Monoclinic
Crystal system
Space group
a/Å
Monoclinic
P2 /n
P2 /a
1
1
7.994(2)
8.610(4)
12.238(9)
100.46(4)
828.3(7)
2
8.819(2)
16.154(4)
13.830(3)
101.07(2)
1933.6(8)
4
b/Å
c/Å
β/°
V/Å3
Z
λ(MoKα)/
µ/cm–1
F(000)
T/K
0.71069
0.72
0.71069
1.19
316
744
Figure 4 UV-visible (top) and fluorescence (bottom) spectra of
compounds 1b–4b.
293
293
D /g⋅cm–3
1.180
1.190
c
Table 3 Comparison of the Different Synthetic Methods
θ range/°
2.83 to 26.96
0 to 10, 0 to 10,
1.50 to 27.00
Entry
1
Compound
Previous synthesis
yield (%)
This work
yield (%)
hkl ranges
0 to 11, 0 to 20,
–17 to 17
–
15 to 15
22, 3416a (i),
1
6b
76
Dmbpy (1a)
17a
Variables
101
237
13 (ii)
4316c (i)
4017c (ii)
6818 (ii)
6517b (ii)
–
Reflections
measured
1919
4213
2
3
4
4
5
Tmbpy (2a)
Dmabiq (3a)
Dmbiq
52
66
Reflections
874
2124
[
I>2σ(I)]
R1[I>2σ(I)]/R1
0.0774/0.1435
0.2305/0.2526
0.0614/0.1519
0.2229/0.2675
Dmphen
(
all data)
Tmphen (4a)
61
wR2[I>2σ(I)]/wR2
(
all data)
Sw
1.012
1.034
regioselectivities. The synthetic procedure reported in this
paper offers the opportunity to build more extended push-
pull chromophores via the versatile dialdehyde precur-
sors.
Largest diff
0.292/–0.333
0.252/–0.239
peak/hole/e⋅Å–3
All reactions were routinely performed under argon using Schlenk
1
13
In summary, we have demonstrated a successful, high
techniques. NMR spectra ( H, C) were recorded at r.t. on a Bruker
1
13
yield, approach for the design of new bis-enamine biden- DPX 200 (operating at 200.12 MHz for H and 50.33 MHz for C).
tate chromophores and fluorophores. These compounds NMR data are listed in parts per million (ppm) and are reported rel-
1
13
ative to tetramethylsilane ( H, C). UV/Vis spectra were recorded
on a Kontron UVIKON 941 spectrophotometer in diluted CH Cl
are good synthons for the synthesis of the corresponding
carbaldehyde derivatives. This route represents a good al-
ternative to the other methods, since it allows the genera-
tion of these aldehydes in better overall yields and high
2
2
–
5
–1
solution (ca. 10 mol.L ). Fluorescence experiments were per-
formed in dilute CH Cl solution (ca. 10 mol.L ) using a PTI
–5
–1
2
2
spectrometer. IR spectra were recorded in KBr pellets using a Nico-
Synthesis 2003, No. 4, 577–583 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Convenient Intermediates for the Synthesis of Carbaldehyde Derivatives
581
+
let 205 FTIR. HRMS spectrometry measurements (FAB, EI) were
performed at the Centre Regional de Mesures Physiques de l’Ouest
HRMS (FAB): m/z calcd for C H N [M + H] : 321.2157; found:
321.2149.
2
0
25
4
(Rennes, France).
–1
–1
UV/Vis (CH Cl ): λ (εmax) = 340 nm (31000 Lmol cm ).
2
2
max
Emission (CH Cl ): λ = 450 nm.
Crystal Structure Analysis
2
2
em
The samples were studied on an automatic diffractometer CAD4
NONIUS with graphite monochromatized MoKα radiation. The
2
0
4,4′-Bis(N,N-dimethylaminovinyl)-3,3′-dimethylene-2,2′-
biquinoline (3b)
Using the same procedure described for 2a, compound 3b was iso-
lated from 3a (1.40 g, 4.5 mmol).
cell parameters are obtained by fitting a set of 25 high-theta reflec-
2
1
tions. After Lorenz and polarization corrections, the structure was
solved with SIR-97,22 which reveals the non-hydrogen atoms of the
structure. After anisotropic refinement, all the hydrogen atoms are
Yield: 1.59 g (84%); red brown powder.
found with a Fourier Difference. The whole structure was refined
1
3
4
with SHELXL9723 by the full-matrix least-square techniques (use
H NMR (CDCl ): δ = 8.34 (dd, J = 8.3, J = 1.1 Hz, 2 H, H10),
3
3
4
3
4
8
.16 (dd, J = 8.3, J = 1.1 Hz, 2 H, H ), 7.56 (td, J = 8.3, J = 1.5
7
of F magnitude; x, y, z, (ij for C, N and O atoms, x, y, z in riding
3
4
2
4
Hz, 2 H, H
9
), 7.43 (td, J = 8.3, J = 1.4 Hz, 2 H, H
8
), 6.54 (d,
mode for H atoms). ORTEP views realized with PLATON98. All
the calculations were performed on a Silicon Graphics Indy com-
puter. Crystallographic data for the structural analysis has been de-
posited with the Cambridge Crystallographic Data Centre, CCDC
no 189533 and 189534 for compounds 1b and 4b, respectively.
3
J = 13.8 Hz, 2 H, H ), 5.43 (d, J = 13.8 Hz, 2 H, H ), 3.20 (s, 4 H,
1
3
12
CH ), 2.91 (s, 12 H, NCH ).
2
3
13C NMR (CDCl
): δ = 153.4, 148.3, 147.5, 143.3, 131.8, 128.2,
3
127.9, 127.6, 126.1, 125.2, 90.5, 41.0, 27.3.
2
5
+·
NaIO (99.8% A.C.S. reagent) was purchased from Aldrich. THF
HRMS (EI): m/z calcd for C28H N [M] : 420.231; found
28 4
4
was distilled over Na/benzophenone, DMF was distilled prior used
420.2283.
and CH Cl was distilled over P O . 4,4′,6,6′-tetramethyl[2,2′]bipy-
ridine (2a) was prepared by sodium coupling of the corresponding
lutidine and purified by sublimation. 4,4′-Dimethyl[2,2′]bipyridine
–1
–1
2
2
2
5
UV/Vis (CH Cl ): λ (εmax) = 385 nm (14000Lmol cm ).
2
2
max
Emission (CH Cl ) : λ = 519 nm.
2
2
em
(
1a) and 3,4,7,8-tetramethyl-o-phenanthroline (4a) were purchased
4
,7-Bis(N,N-dimethylaminovinyl)-3,8-dimethyl-1,10-phenan-
from Aldrich and used as received.
throline (4b)
Using the same procedure described for 2a, compound 4b was iso-
lated from 4a (0.50 g, 2.12 mmol).
4
,4′-Dimethyl-3,3′-dimethylene-2,2′-biquinoline (3a)
In a Schlenk flask, 1,2-cyclohexanedione (1.16 g, 10 mmol) and 2′-
aminoacetophenone hydrochloride (3.55 g, 20 mmol) were mixed
with 2-methoxyethanol (30 mL) and the mixture was heated under
reflux for 48 h. After cooling to r.t., the solvent was removed under
vacuum and the residue dissolved in CH Cl . The organic layer was
washed with sat. aq NaHCO , and with H O (50 mL). The solution
was dried (MgSO ), filtered and the solvent was removed under
vacuum. After precipitation from a THF–pentane mixture (1:10),
the desired compound was obtained.
Yield: 0.69 g (94%); green powder.
1
H NMR (CDCl ): δ = 8.79 (s, 2 H, H , H ), 8.08 (s, 2 H, H , H ),
3
2
9
3
5
6
3
6
2
.70 (d, J = 13.8 Hz, 2 H, H ), 5.27 (d, J = 13.8 Hz, 2 H, H ),
1
6
15
2
2
.78 (s, 12 H, NCH ), 2.37 (s, 6 H, Me).
3
3
2
13C NMR (CDCl
): δ = 151.2, 146.9, 146.0, 143.4, 127.1, 125.2,
4
3
122.7, 91.2, 40.6, 18.6.
+
HRMS (FAB): m/z calcd for [M + H] (C H N ): 347.2236; found:
2
2
27
4
Yield: 2.55 g (79%); pale-brown powder.
347.2251.
1
3
4
–1
–1
H NMR (CDCl ): δ = 8.42 (dd, J = 8.2, J = 1.0 Hz, 2 H, H ),
UV/Vis (CH Cl ): λmax (εmax) = 352 nm (25500 Lmol cm ).
2 2
3
10
3
4
3
4
7
.99 (dd, J = 8.3, J = 1.0 Hz, 2 H, H ), 7.66 (td, J = 8.2, J = 1.4
7
Emission (CH Cl ) : λ = 470 nm.
2 2 em
3
4
Hz, 2 H, H ), 7.54 (td, J = 8.3, J = 1.4 Hz, 2 H, H ), 3.20 (s, 4 H,
9
8
CH ), 2.70 (s, 6 H, CH ).
2
3
4-[p-(N,N-Dimethylamino)styryl]-4′- (N,N-dimethylaminovi-
nyl)-2,2′-bipyridine (5b)
1
3
C NMR (CDCl ): δ = 152.0, 147.3, 140.4, 131.8, 130.2, 128.4,
3
1
28.1, 126.9, 123.4, 24.9, 14.1.
To a solution of 4-[p-(N,N-dimethylamino)styryl]-4′-methyl-2,2′-
bipyridine (5a) (0.50 g, 1.60 mmol) in DMF (10 mL) was added un-
der argon the Bredereck’s reagent [tert-butoxybis(dimethylami-
no)methane] (0.56 g, 3.2 mmol). The mixture was refluxed for 18 h.
After cooling down to r.t., the pale orange mixture was hydrolyzed
by addition of H O (20 mL) and extracted with CH Cl (4 × 10 mL).
+
HRMS (EI): m/z calcd for C H N [M] ·: 310.1470; found:
3
2
2
18
2
10.1528.
4
,4′-Bis(N,N-dimethylaminovinyl)-6,6′-dimethyl-2,2′-bipyri-
2
2
2
dine (2b)
The organic phase was dried (MgSO ) and the solvent removed un-
4
To a solution of 4,4′,6,6′-tetramethyl[2,2′]bipyridine (0.50 g, 2.3
mmol) in DMF (15 mL) was added under argon the Bredereck's re-
agent [tert-butoxybis(dimethylamino)methane] (2.09 g, 12 mmol).
The mixture was refluxed for 18 h. After cooling down to r.t., the
der vacuum. The resulting orange solid was recrystallized from
CH Cl –Et O to give the desired product.
2
2
2
Yield: 0.50 g (85%); brown powder.
pale orange mixture was hydrolyzed by addition of H O (30 mL)
1
3
2
H NMR (CD Cl ): δ = 8.56 (d, J = 5.3 Hz, 1 H, H ), 8.43 (d,
2 2 6
and extracted with CH Cl (4 × 30 mL). The organic phase was
4
3
4
2
2
J = 1.2 Hz, 1 H, H ), 8.37 (d, J = 5.3 Hz, 1 H, H ), 8.13 (d, J = 1.8
3
6
′
dried (MgSO ) and the solvent removed under vacuum. The result-
3
3
4
Hz, 1 H, H ), 7.44 (d, J = 8.8 Hz, 2 H, C H ), 7.38 (d, J = 16.1 Hz,
3′ 6 4
1 H, = CHstyryl), 7.30 (dd, J = 5.3, J = 1.2 Hz, 1 H, H ), 7.20 (d,
J = 13.6 Hz, 1 H, H ), 6.97 (dd, J = 5.3, J = 1.8 Hz, 1 H, H ), 6.89
(d, J = 16.1 Hz, 1 H, =CHstyryl), 6.70 (d, J = 8.8 Hz, 2 H, C
5.08 (d, J = 13.6 Hz, 1 H, H
NCH ).
ing orange solid was recrystallized from CH Cl –pentane to give
3
4
2
2
5
the desired product as a saffron-yellow powder (0.66 g., 87% yield).
3
4
8
5′
1
4
3
3
H NMR (CDCl ): δ = 7.87 (d, J = 1.5 Hz, 2 H, H ), 7.15 (d,
6
H
4
),
), 2.98 (s, 6 H, NCH ), 2.87 (s, 6 H,
3
3
3
4
J = 13.7 Hz, 2 H, H ), 6.84 (d, J = 1.5 Hz, 2 H, H ), 5.06 (d,
7
8
5
J = 13.7 Hz, 2 H, H ), 2.86 (s, 12 H, NCH ); 2.52 (s, 6 H, Me ).
3
7
3
6
1
3
+
C NMR (CDCl ): δ = 157.2, 156.3, 148.6, 143.1, 117.1, 112.7,
HRMS (FAB): m/z calcd for C24
370.2175.
H
26
N
4
[M] : 370.2157; found:
3
9
5.0, 40.6, 24.8.
Synthesis 2003, No. 4, 577–583 ISSN 0039-7881 © Thieme Stuttgart · New York

5
82
L. Viau et al.
PAPER
–
1
–1
13
UV/Vis (CH Cl ): λ (εmax) = 388 nm (31000 Lmol cm ), 350
C NMR (CDCl ): δ = 193.0, 154.2, 145.4, 134.4, 134.3, 124.6,
2
2
max
3
nm (sh).
124.3, 16.7.
+
HRMS (FAB): m/z calcd for [M + H] : (C H N ): 265.0977;
1
6
13
2
4
-[p-(Octyloxy)styryl]-4′-(N,N-dimethylaminovinyl)-2,2′-bipy-
found: 265.0975.
ridine (6b)
To a solution of 4-[p-(octyloxy)styryl]-4′-methyl-2,2′-bipyridine
4
-[p-(N,N-Dimethylamino)styryl]-4′-(carbaldehyde)-2,2′-bipy-
(
6a) (0.30 g, 0.75 mmol) in DMF (3 mL) was added under argon the
ridine (5c)
Bredereck’s reagent [tert-butoxybis(dimethylamino)methane] (0.56
g, 3.2 mmol). The mixture was refluxed for 18 h. After cooling
down to r.t., the pale orange mixture was hydrolyzed by addition of
H O (20 mL) and extracted with CH Cl (4 × 5 mL). The organic
Using the same procedure described for 2c, compound 6c was iso-
lated from 6b (0.20 g, 0.54 mmol) and NaIO (0.46 g, 2.15 mmol).
4
Yield: 0.11 g (64%); orange powder.
IR (KBr): = 1716 (C=O) cm–1.
2
2
2
phase was dried (MgSO ) and the solvent removed under vacuum.
4
The resulting orange solid was recrystallized from CH Cl – Et O to
2
2
2
1
3
H NMR (DMSO-d ): δ = 10.21 (s, 1 H, CHO), 8.89 (d, J = 5.0 Hz,
6
give the desired product.
3
1
H, H ), 8.84 (s, 1 H, H ), 8.62 (d, J = 5.0 Hz, 1 H, H ), 8.50 (s, 1
6
3
6′
Yield: 0.28 g (82%); yellow-brown powder.
3
3
H, H ), 7.88 (d, J = 5.0 Hz, 1 H, H ), 7.60 (d, J = 5.0 Hz, 1 H, H ),
7.55 (d, J = 8.3 Hz, 2 H, C H ), 7.52 (d, J = 16.7 Hz, 1
H, =CHstyryl), 7.11 (d, J = 16.7 Hz, 1 H, =CH ), 6.75 (d, J = 8.3
Hz, 2 H, C H ), 2.97 (s, 6 H, NCH ), 2.87.
3
′
5
5′
3
3
1
3
H NMR (CD Cl ): δ = 8.53 (d, J = 5.1 Hz, 1 H, H ), 8.40 (s, 1 H,
6 4
2
3
2
6
3
3
H ), 8.32 (d, J = 5.3 Hz, 1 H, H ), 8.09 (s, 1 H, H ), 7.42 (d,
styryl
3
6′
3′
3
3
J = 8.7 Hz, 2 H, C H ), 7.34 (d, J = 16.4 Hz, 1 H, =CHstyryl), 7.25
6
4
3
6
4
3
4
(
6
dd, J = 5.1, J = 1.4 Hz, 1 H, H ), 7.14 (d, J = 13.6 Hz, 1 H, H ),
.92 (dd, J = 5.3, J = 1.5 Hz, 1 H, H ), 6.90 (d, J = 16.4 Hz, 1
+
5
8
HRMS (FAB): m/z calcd for [M] : (C H N O): 329.1528; found:
21 19 3
329.1458.
3
4
3
5′
3
H, =CHstyryl), 6.84 (d, J = 8.7 Hz, 2 H, C H ), 5.04 (d, J = 13.6 Hz,
6
4
–1
–1
UV/Vis (CH Cl ): λ (εmax) = 382 nm (30000 Lmol cm ).
2
2
max
2
H, H ), 3.95 (t, J = 6.5 Hz, 2 H, OCH ), 2.86 (s, 6 H, NCH ), 1.73
7
2
3
(
m, 2 H, CH ), 1.24 (m, 10 H, 5 CH ), 0.82 (m, 3 H, Me).
2
2
1
3
C NMR (CDCl ): δ = 159.7, 157.1, 155.6, 149.3, 148.9, 148.8, Acknowledgments
3
1
(
45.9, 143.4, 132.8, 128.9, 128.4, 123.9, 120.5, 118.2, 117.9, 114.8
2 C), 94.5, 68.1, 40.6, 31.8, 29.4, 29.3 (2 C), 26.0, 22.7, 14.1.
The authors would like to thank the Region Bretagne for financial
support. LV and KS are grateful to CNRS-Région Bretagne and
MENRT respectively for their grants.
+
HRMS (FAB): m/z calcd for C H N O [M] : 455.2937; found:
4
3
0
37
3
55.2913.
–
1
–1
UV/Vis (CH Cl ): λ (εmax) = 332 nm (17000 L.mol .cm ).
2
2
max
References
4
,4′-Dicarbaldehyde-6,6′-dimethyl-2,2′-bipyridine (2c)
(
(
(
1) Kaes, C.; Katz, A.; Hosseini, M. W. Chem. Rev. 2000, 100,
In a Schlenk flask, 4,4′-bis(N,N-dimethylaminovinyl)[6,6′]dimeth-
yl[2,2′]bipyridine (0.32 g, 1 mmol) was dissolved in THF (180 mL)
and an aq solution of NaIO (1 M; 8 g, 37 mmol) was added drop-
wise. The orange mixture turned white when stirred at 40 °C for 18
h. After cooling to r.t., the solvent was removed under vacuum. The
product was dissolved in CH Cl (40 mL) and washed with H O
3553.
2) Balzani, V.; Juris, A.; Venturi, M.; Campagna, S.; Serroni,
S. Chem. Rev. 1996, 96, 759.
3) Kalyanasundaram, K.; Grätzel, M. Coord. Chem. Rev. 1998,
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77, 347.
2
2
2
(4) (a) Zhou, X.; Tyson, D. S.; Castellano, F. N. Angew. Chem.
Int. Ed. 2000, 39, 4301. (b) Serroni, S.; Campagna, S.;
Puntoriero, F.; Di Pietro, C.; McClenaghan, N. D.; Loiseau,
F. Chem. Soc. Rev. 2001, 30, 367.
(
2 × 50 mL). The organic phase was dried (MgSO ), filtered, and
4
the solvent then removed under vacuum. After precipitation from
CH Cl –pentane, the desired compound was finally obtained as a
pale-yellow microcrystalline powder (0.14 g, 60% yield).
2
2
(
5) Ziessel, R.; Ulrich, G.; Lawson, R. C.; Echegoyen, L. J.
Mater. Chem. 1999, 9, 1435.
–
1
IR (KBr): 1731 (C=O) cm .
(
(
6) Le Bozec, H.; Renouard, T. Eur. J. Inorg. Chem. 2000, 229.
7) (a) Hilton, A.; Renouard, T.; Maury, O.; Le Bozec, H.;
Ledoux, I.; Zyss, J. Chem. Commun. 1999, 2521.
1
H NMR (CDCl ): δ = 10.16 (s, 2 H, CHO), 8.67 (s, 2 H), 7.60 (s, 2
3
1
6c
H), 2.74 (s, 6 H). (Lit. 10.15, 8.66, 7.59, 2.74).
(
b) Sénéchal, K.; Maury, O.; Le Bozec, H.; Ledoux, I.; Zyss,
4
,4′-Dicarbaldehyde-3,3′-dimethylene-2,2′-biquinoline (3c)
J. J. Am. Chem. Soc. 2002, 124, 4561. (c) Maury, O.;
Guégan, J. P.; Renouard, T.; Hilton, A.; Dupan, P.; Sandon,
N.; Toupet, L.; Le Bozec, H. New J. Chem. 2001, 25, 1553.
8) For a preliminary communication, see: Dupau, P.;
Renouard, T.; Le Bozec, H. Tetrahedron Lett. 1996, 42,
7503.
Using the same procedure described for 2c, compound 3c was iso-
lated from 3b (0.75g, 1.78 mmol) after precipitation from THF–
pentane.
(
(
Yield: 0.41 g (66%); pink solid.
–
1
IR (KBr): 1695 (C=O) cm .
9) For a review, see: Abdulla, R.; Brinkmeyer, R. F.
Tetrahedron 1979, 35, 1675.
1
H NMR (CDCl ): δ = 11.12 (s, 2 H, CHO), 8.5 (m, 4 H), 7.8 (m, 4
3
1
7c
H), 3.59 (s, 4 H, CH ). (Lit. 11.06, 8.50, 7.75, 7.64, 3.45).
2
(10) Bredereck, H.; Simchen, G.; Wahl, R. Chem. Ber. 1968, 101,
048.
4
4
,7-Dicarbaldehyde-3,8-dimethyl-1,10-phenanthroline (4c)
(
(
11) Thummel, R. P.; Lefoulon, F. J. Org. Chem. 1985, 50, 666.
12) (a) Chisholm, M. H.; Huffman, J. C.; Rothwell, I. P.;
Bradley, P. G.; Kress, N.; Woodruff, W. H. J. Am. Chem.
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Can. J. Chem. 1991, 69, 1117. (c) Bolm, C.; Ewald, M.;
Zehnder, M.; Neuburger, M. A. Chem. Ber. 1992, 125, 453.
Using the same procedure described for 2c, compound 4c was iso-
lated from 4b (1.26 g, 3.63 mmol).
Yield: 0.63 g (65%); pale yellow powder.
–
1
IR (KBr): 1730 (C=O) cm .
1
H NMR (CDCl ): δ = 10.98 (s, 2 H, H ), 9.13 (s, 2 H, H ), 7.96 (s,
(13) Wrighton, M.; Morse, D. L. J. Am. Chem. Soc. 1974, 96,
3
15
9
2
H, H H ), 2.83 (s, 6 H, H ).
6 5 14
998.
Synthesis 2003, No. 4, 577–583 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Convenient Intermediates for the Synthesis of Carbaldehyde Derivatives
583
(
14) Moya, S. A.; Guerrero, J.; Pastene, R.; Schmidt, R.; Sariego,
R.; Sartori, R.; Sanz-Aparicio, J.; Fonseca, I.; Martinez-
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(19) An alternative multistep procedure involving the prior
synthesis of 6,6′-dimethyl[4,4′]dicarboxylate[2,2′]-
bipyridine via a nickel mediated coupling of halopyridines
has been reported: Alpha, B.; Anklam, E.; Lehn, J.-M.;
Pietraskiewicz, M. Helv. Chim. Acta 1988, 71, 1043.
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Crystal Structure, Analysis, User Manual; Enraf-Nonius:
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(
(
(
c) Harding, M. M.; Koert, U.; Lehn, J.-M.; Marquis-
Rigault, A.; Piguet, C.; Siegel, J. Helv. Chim. Acta 1991, 74,
94. (d) For an alternative synthesis of polypyridine-ester
5
precursors by palladium-promoted carboalkoxylation, see:
El-Gahyoury, A.; Ziessel, R. J. Org. Chem. 2000, 65, 7757.
17) (a) McCafferty, D. G.; Bishop, B. M.; Wall, C. G.; Hughes,
S. G.; Mecklenberg, S. L.; Meyer, T. J.; Erickson, B. W.
Tetrahedron 1995, 51, 1093. (b) Yanagida, M.; Sigh, L. P.;
Sayama, K.; Hara, K.; Katoh, R.; Islam, A.; Sugihara, H.;
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(22) Altomare, A.; Burla, M. C.; Camalli, M.; Carscarano, G.;
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(24) Spek, A. L. PLATON, A Multipurpose Crystallographic
Tool; Utrecht University: Utrecht, The Netherlands, 1998.
(
(25) Other sources of NaIO gave only poor yield.
4
Synthesis 2003, No. 4, 577–583 ISSN 0039-7881 © Thieme Stuttgart · New York