Ester-functionalized phthalonitriles and zinc phthalocyanines via palladium-catalyzed cyanation of 4,5-dichlorophthalates

Article abstract of DOI:10.1016/j.tet.2008.03.004

Dicyanophthalates 3 were synthesized via Pd-catalyzed two-fold cyanation of the corresponding 4,5-dichlorophthalates with Zn(CN)₂. Appropriate modification of reaction conditions allowed one-pot synthesis of the corresponding zinc phthalocyanines 7 bearing eight peripheral alkyl ester groups. Powder X-ray diffraction study of a mesogenic zinc phthalocyanine bearing branched alkyl substituents revealed a rare case of a transition between two columnar rectangular liquid crystalline mesophases with different symmetry.

Full text of DOI:10.1016/j.tet.2008.03.004

Available online at www.sciencedirect.com
Tetrahedron 64 (2008) 4155e4161
www.elsevier.com/locate/tet
Ester-functionalized phthalonitriles and zinc phthalocyanines
via palladium-catalyzed cyanation of 4,5-dichlorophthalates
a
Benoıt Tylleman , Rafael Gomez-Aspe , Gabin Gbabode ,
b
a
ˆ
´
Yves Henry Geerts a, Sergey Sergeyev a,
*
a Universite´ Libre de Bruxelles (ULB), Laboratoire de Chimie des Polyme`res, CP 206/01, Boulevard du Triomphe, 1050 Bruxelles, Belgium
b Department of Organic Chemistry, Universidad Complutense de Madrid, Avda. Complutense, 28040 Madrid, Spain
Received 1 February 2008; received in revised form 29 February 2008; accepted 3 March 2008
Available online 7 March 2008
Abstract
Dicyanophthalates 3 were synthesized via Pd-catalyzed two-fold cyanation of the corresponding 4,5-dichlorophthalates with Zn(CN)2.
Appropriate modification of reaction conditions allowed one-pot synthesis of the corresponding zinc phthalocyanines 7 bearing eight peripheral
alkyl ester groups. Powder X-ray diffraction study of a mesogenic zinc phthalocyanine bearing branched alkyl substituents revealed a rare case of
a transition between two columnar rectangular liquid crystalline mesophases with different symmetry.
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords: Phthalocyanines; Phthalonitriles; Palladium; Cyanation
1. Introduction
Recently, we have reported5,6 the synthesis of octaester
derivatives of metal-free phthalocyanines (1, Scheme 1) via
the eight-fold esterification of octaacid 2. Major disadvan-
tages of this method are rather long reaction times due to
very limited solubility of the octaacid 2 in virtually all or-
ganic solvents and the necessity to perform conversion of
eight functional groups in one molecule. In addition, when
the resulting octaester was also only poorly soluble in the re-
action medium (what was the case for shorter alkyl substitu-
ents or for partially fluorinated alkyls), the yields of the
esterification dropped dramatically. Finally, the two-step syn-
thesis of the octaacid 2 from 1,2,4,5-tetracyanobenzene is
rather time-consuming.7 Therefore, we became interested in
designing an alternative synthetic pathway to phthalocya-
nines such as 1, starting from well-soluble precursors. Since
phthalocyanines are commonly prepared by the tetrameriza-
tion of suitably functionalized ortho-phthalonitriles, dialkyl
dicyanophthalates 3 appear as most obvious synthetic inter-
mediates for this approach. Here, we report on the efficient
synthesis of ester-functionalized phthalonitriles 3 via Pd-
catalyzed cyanation as well as on related studies on the syn-
thesis and characterization of metal-free phthalocyanines and
their zinc analogs.
Phthalocyanines have found a number of important indus-
trial applications as dyes and pigments due to their bright
blue or green colors combined with extraordinary thermal
and photochemical stability.1 In addition, they have been in-
vestigated for their potential use in many other fields, includ-
ing catalysis, chemical sensors, non-linear optical materials,
ink-jet printing, electrophotography, and photodynamic ther-
apy.2,3 Mesogenic phthalocyanines bearing flexible peripheral
substituents have been widely studied for applications in elec-
tronic devices and have demonstrated very efficient charge
transport.4 Combination of charge transport capacity with
very strong absorption of visible light makes them promising
candidates for photovoltaic applications. Our research is
focused around phthalocyanines for applications in organic
electronic devices, including photovoltaic cells. In particular,
we are interested in liquid crystalline, solution-processable
phthalocyanines bearing electron-withdrawing groups as ac-
ceptor components for bulk heterojunction photovoltaic cells.
* Corresponding author. Tel.: þ32 2 6505392; fax: þ32 2 6505410.
E-mail address: sserguee@ulb.ac.be (S. Sergeyev).
0040-4020/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.03.004

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B. Tylleman et al. / Tetrahedron 64 (2008) 4155e4161
Scheme 1. Two possible synthetic approaches to octa(alkoxycarbonyl)phthalocyanines.
2. Results and discussion
With the necessary key intermediates in hands, we tried
next the condensation of phthalonitriles 3aed to the corre-
sponding octaester derivatives of phthalocyanines 1. Common
protocols for the synthesis of phthalocyanines from phthaloni-
triles involve lithium alcoholates and are clearly incompatible
with ester functions. However, milder procedures using a non-
nucleophilic base (DBU, 1,8-diazabicyclo[5.4.0]undec-7-
ene)12 or cerium-promoted condensation of phthalonitriles13
were unsuccessful either. Although some phthalocyanines
were obviously produced, as can be judged by the intense
green color of reaction mixtures, no individual compounds
were isolated. Finally, a recently reported mild procedure us-
ing propanone or butanone oximes14 as weak bases and at
the same time, as reducing agents (condensation of four mol-
ecules of a phthalonitrile to give a phthalocyanine molecule
formally requires donation of two electrons and two protons)
resulted largely in the recovery of the starting materials and
produced only traces of desired phthalocyanines. Thus, 3c
gave 5% of the corresponding metal-free phthalocyanine 1
(R¼n-C8H17). Spectral data of the latter were identical to
those of a material prepared by the esterification of the octa-
acid 2 with n-octanol.5 Since the original esterification method
gave much higher yields of the corresponding phthalocyanines
(60e64% from the octaacid 2), we decided to discontinue the
attempts to optimize the condensation of phthalonitriles 3.
However, in the above described Pd-catalyzed cyanation of
dichlorophthalates 5aed, we paid attention to the greenish
color of the reaction mixture. This clearly indicated an in
situ formation of trace amounts of phthalocyanines from the
initially formed phthalonitriles. At elevated temperatures and
longer reaction times, this pathway became a dominating
one. Thus, only a minute amount of dinitrile 3a was isolated
after 16 h from the reaction between diethyl dichlorophthalate
5a and Zn(CN)2 in DMA at 140 ꢁC. Instead, column chroma-
tography afforded 13% of the rather poorly soluble zinc
Neither the dicyanophthalates 3 nor the parent 4,5-dicya-
nophthalic acid is described in the chemical literature. We
have therefore developed a two-step synthesis of a series of
phthalonitriles 3aed starting from the commercially available
4,5-dichlorophthalic acid 4 (Scheme 2). First, the correspond-
ing 4,5-dichlorophthalates 5aed with linear alkyl radicals of
various lengths were prepared in 72e90% yield by a standard
acid-catalyzed esterification of 4 with alcohols 6aed upon
azeotropic removal of water with toluene. Diethyl ester 5a8
was purified by crystallization, while longer-chain homologs
5bed required chromatography on a short column to remove
the excess of alcohol.
The reaction of metal cyanides with aryl halides is a well-
known general methodology for the synthesis of aromatic
nitriles.9 Classically known as the Rosenmundevon Braun re-
action, it typically requires rather harsh conditions and allows
substitution of bromine or iodine, but not of chlorine. How-
ever, this useful transformation was greatly improved in recent
years by application of transition metal complexes as catalysts.
It allows, upon appropriate choice of a catalyst, to carry out
halogeneCN displacement in rather deactivated substrates.10
For the conversion of dichlorophthalates 5aed to the corre-
sponding dinitriles 3aed, we have adapted the Pd-catalyzed
cyanation protocol that proved efficient in various chlorinee
CN substitutions.11 Air-stable [Pd2(dba)3] and an activating
ligand, dppf (1,10-bis(diphenylphosphino)ferrocene), were
used as an efficient catalytic system. The combination of
Zn(CN)2 as a cyanide source with catalytic amounts of Zn al-
lows to avoid the CNꢀ-induced deactivation of the catalyst.
Starting from dichlorophthalates 5aed, the corresponding
ester-functionalized phthalonitriles 3aed were obtained in
72e83% yield after 2 h in N,N-dimethylacetamide (DMA) at
120 ꢁC.
Scheme 2. Synthesis of diesters 5aee and dinitriles 3aed; dba¼dibenzylideneacetone, dppf¼1,10-bis(diphenylphosphino)ferrocene, DMA¼N,N-
dimethylacetamide.

B. Tylleman et al. / Tetrahedron 64 (2008) 4155e4161
4157
phthalocyanine 7a (Scheme 3), structure of which was estab-
1
sorbent. We therefore assume that cleavage of ester groups
took place to give highly polar products with free carboxyl
groups.
lished by H NMR, MALDIMS, and UVevis spectroscopy.15
We thus observed an interesting and to the best of our knowl-
edge previously unknown one-pot transformation of an ortho-
dichlorobenzene derivative to a Zn-phthalocyanine. Also, this
is only the second reported example of a metallated phthalocy-
anine derivative bearing peripheral ester groups.16
The isolated ester-functionalized zinc phthalocyanine 7e
was characterized by various physicochemical methods.
MALDIMS measurements confirmed the absence of the
metal-free phthalocyanine 1e and of the corresponding palla-
dium phthalocyanine (formation of the latter cannot a priori
be excluded in the Pd-catalyzed reaction). The exact molecular
mass of 7e is in excellent agreement with the calculated value.
The UV spectrum of 7e in CH2Cl2 is typical for a metalated
phthalocyanine and features a single intense low-frequency
absorption band (termed Q-band) due to a degenerate first
excited state of a D4h-symmetrical molecule (cf. a split of
Q-band due to the loss of degeneracy in the metal-free phtha-
locyanine 1e with lower D2h symmetry, Fig. 1).
1H NMR spectrum of zinc phthalocyanine 7e in CDCl3 in-
dicates strong aggregation, as evidenced by very broad signals.
This is due to the propensity of the central Zn2þ ion for
pentacoordination, which results in efficient interaction with
nitrogen atoms of neighboring phthalocyanine molecules.
However, when an excess of deuterated pyridine (C5D5N) is
added to a solution, it acts as a competing ligand and well-
resolved 1H and 13C NMR spectra are obtained due to greatly
diminished aggregation (see Supplementary data).
Another property of phthalocyanines that is well known to
be significantly affected by cofacial inter-disk interactions and
therefore, by the nature of the central metal ion is the thermal
stability of columnar LC mesophases. Indeed, according to po-
larized optical microscopy (POM) data, 7e forms LC meso-
phases between room temperature and ca. 250 ꢁC (clearing
point determined by POM; more precise measurement of iso-
tropization temperature by differential scanning calorimetry
(DSC) was not possible because of slow decomposition
of 7e at high temperatures). Thus, the isotropization tempera-
ture of 7e is ca. 100 ꢁC higher than that of the corresponding
metal-free analog 1e bearing identical peripheral groups.5 A
similar effect of the central zinc atom on the stability of
Scheme 3. One-pot conversion of dichlorophthalates 5 into zinc phthalocyanines
7; dba¼dibenzylideneacetone, dppf¼1,10-bis(diphenylphosphino)ferrocene,
DMA¼N,N-dimethylacetamide, DBU¼1,8-diazabicyclo[5.4.0]undec-7-ene.
We speculated that the rather low yield of the ester-func-
tionalized zinc phthalocyanine 7a might be due to its poor sol-
ubility in organic solvents. We have therefore attempted to
apply this method to the synthesis of zinc phthalocyanine 7e
bearing eight branched alkyl substituents. This target molecule
was chosen since branched alkyl substituents are well known
to reduce intermolecular cofacial interactions between flat
phthalocyanine cores both in solution and in the solid state
much more efficiently compared to the linear homologs.
This results in greatly improved solubility in common organic
solvents and in the formation of liquid crystalline (LC) colum-
nar mesophases over broad temperature range. Both features
are highly relevant for materials intended for the use in organic
electronic devices.17
Thus, we have synthesized bis(2-butyloctyl)-4,5-dichloro-
phthalate 5e by the same esterification procedure as described
above for the linear homologs 5aed. However, starting from
5e, only 6% of Zn-phthalocyanine 7e was isolated after 16 h
in DMA at 140 ꢁC. We reasoned that addition of a non-nucle-
ophilic base such as DBU may increase the yield of 7e. How-
ever, only marginal improvement (10% of 5e from 7e) was
achieved and the yield thus remained rather low. We noticed
that a considerable amount of (presumably) phthalocyanine
derivatives remained non-isolable during workup and purifica-
tion, as was judged by the very intense green color of the
aqueous phases after extraction and of the chromatography
Figure 1. UVevis absorption spectra of metal-free phthalocyanine 1e (gray
line) and zinc phthalocyanine 7e (black line) bearing identical peripheral sub-
stituents; spectra recorded in CH2Cl2.

4158
B. Tylleman et al. / Tetrahedron 64 (2008) 4155e4161
columnar LC mesophases was reported earlier for
octaalkylphthalocyanines.2,18
liquid-like disordered aliphatic chains, characteristic for LC
phases. No reflection in the q range 1.7e1.8 Aꢀ1, which would
˚
A typical dendritic structure observed by POM after cool-
ing of 7e between two glass slides from isotropic melt below
clearing point suggests a columnar LC phase. Upon further
cooling down to room temperature no significant change in
the POM texture was observed. However, DSC measurements
revealed one more reversible transition at lower temperatures
(heating: 44 ꢁC [1.1 kJ molꢀ1], cooling: 30 ꢁC [1.0 kJ molꢀ1]).
Relatively small enthalpy suggests only a minor change in the
structure of the material, that is, a transition between two dif-
ferent LC phases. This assumption has been confirmed by
powder X-ray diffraction of 7e at different temperatures.
X-ray diagrams at 30 and 100 ꢁC are shown in Figure 2; for
the detailed evolution of the X-ray diffraction patterns as
a function of temperature, see Supplementary data.
correspond to the pep stacking distance was observed, thus
indicating a poor order along the columnar axis. Thus, similar
to the metal-free analog 1e, zinc phthalocyanine 7e forms
relatively disordered Colr phases.5
The cell parameters of low temperature and high temperature
LC mesophases (Colr1 and Colr2, respectively) are very close to
each other (see Supplementary data). However, some clear dif-
ferences between the X-ray diffraction patterns of Colr1 and
Colr2 were observed. Firstly, the positions of the (20) reflection
are slightly different and the gradual change of this position was
clearly observed on heating or cooling across the transition tem-
perature between Colr1 and Colr2 (see Supplementary data).
Secondly, a broadening of the peak in the q range 0.6e
0.7 Aꢀ1 upon transition from Colr1 to Colr2 is due to the appear-
˚
X-ray diffraction patterns of 7e at 30 and 100 ꢁC are very
similar. They both exhibit two sharp, intense diffraction peaks
together with less intense higher order peaks in the small angle
ance of the (32) reflection. Therefore, on the basis of higher
order reflections two different planar symmetry groups C2mm
and P2gg can be assigned to mesophases Colr1 and Colr2, re-
spectively. Indeed, for P2gg symmetry the reflections h0 and
0k should satisfy the conditions h¼2n and k¼2n. In addition,
in C2mm symmetry group reflections with hþk¼2nþ1 are for-
bidden. Hence, the (32) reflection observed for Colr2 is only
possible for P2gg plane group, whereas the base-centered
C2mm plane group has been assigned to Colr1. A similar tran-
sition between two Colr LC phases of different symmetry has
been reported for some mesogenic disc-like metaleligand com-
plexes,19 but to the best of our knowledge, it is unprecedented
for phthalocyanine derivatives.
region (q<1.2 Aꢀ1), thus suggesting 2D rectangular lattices
˚
ꢀ1
˚
(Colr). A broad diffuse halo at q>1.2 A originates from
Taking advantage of its enhanced solubility, zinc phthalo-
cyanine 7e was chosen for electrochemical studies, which
were performed by cyclic voltammetry (CV) using a platinum
wire as working and counter electrode and a reference Ag/
AgCl electrode. Unlike the metal-free phthalocyanine 1e,5
zinc phthalocyanine 7e showed poorly resolved voltammo-
grams in THF with peak currents approaching zero. How-
ever, in CH2Cl2 well-resolved quasi-reversible reduction
Figure 3. Cyclic voltammogram of 7e in CH2Cl2 using Pt disk and wire as
working and counter electrode, Ag/Agþ as reference electrode and Bu4NClO4
(0.1 M) as supporting electrolyte. Measurements were carried out at room
temperature with a scan rate of 50 mV sꢀ1
.
Figure 2. X-ray diffraction patterns of 7e at 30 ꢁC (Colr1; top) and 100 ꢁC
(Colr2; bottom).

B. Tylleman et al. / Tetrahedron 64 (2008) 4155e4161
4159
waves were observed at E1/2¼ꢀ1.16 and ꢀ1.44 V (Fig. 3).
These waves can be assigned to the characteristic ring-based
electrochemistry of phthalocyanines.20 The position of the re-
duction waves and the absence of clear oxidation signals in
the electrochemical window of the solvent are consistent
with the electron-poor nature of the phthalocyanine core
due to the presence of eight electron-withdrawing alkoxycar-
bonyl groups (see our earlier studies of metal-free phthalocy-
anine 1e and also a communication by Torres, Guldi and
co-workers on a palladium phthalocyanine bearing alkylsul-
fonyl substituents).5,21 Finally, no measurable difference in
reduction potentials was observed upon titration of the solu-
tion with metal-competing amine ligands (pyridine or Et3N),
thus not giving any evidence of the influence of aggregation
on the redox potentials within the investigated concentration
range.
Pd-catalyzed reactions were performed in oven-dry glass-
ware under dry Ar atmosphere. Dry N,N-dimethylacetamide
˚
was kept over 4 A molecular sieves. Column chromatogra-
phy: SiO2 Kieselgel 60 (Macherey-Nagel, particle size
0.04e0.063 mm). TLC: precoated SiO2 plates Kieselgel
60F254 (Merck). 1H NMR (300 MHz) and 13C NMR
(75 MHz) spectra were recorded on a Brucker Avance 300
spectrometer at 25 ꢁC; chemical shifts (d) are given in parts
per million relative to Me4Si; coupling constants (J) are
given in hertz. Electron impact mass spectra (EIMS) were re-
corded on a Waters AutoSpec 6F instrument and matrix-
assisted laser desoprtion/ionization mass spectra (MALDIMS)
on a Waters QToF 2 instrument; m/z with the lowest isotopic
mass are reported. IR spectra were recorded on a Shimadzu
IR-470 instrument. Phase transition temperatures were deter-
mined by differential scanning calorimetry (PerkineElmer
Diamond DSC) from the onsets of the second heating and
the second cooling curves. Optical textures were observed
with a polarizing microscope (Nikon Eclipse 80i). UVevis
spectra were recorded on a HewlettePackard 8453 spectro-
photometer.
3. Conclusion
We have described an efficient synthesis of ester-function-
alized phthalonitriles via Pd-catalyzed two-fold cyanation of
the corresponding dialkyl dichlorophthalates with Zn(CN)2
as a source of cyanide. Since phthalonitriles are used in the
synthesis of some otherwise hardly accessible heterocyclic
systems,22 reported by us, method for the preparation of func-
tionalized dinitriles may serve as a convenient entry to such
intermediates.
In addition, we have reported the one-pot synthesis of ester-
functionalized zinc phthalocyanines from dichlorophthalates
by Pd-catalyzed cyanation followed by in situ macrocycliza-
tion. To the best of our knowledge, this is the only example
of such synthesis of Zn-phthalocyanine derivatives. Unfortu-
nately, the yield of zinc phthalocyanines remained relatively
low. Nevertheless, this method is of certain interest since it
gives rapid access to functionalized metalated phthalocyanines
in only two steps starting from commercial materials. This ap-
proach could be useful in the synthesis of other substituted
zinc phthalocyanines from the corresponding ortho-dihaloben-
zenes, and one may expect that other type of functional groups
will give better yields.
Due to large electron density of the central metal atom, liq-
uid crystalline phthalocyanine 7e is an interesting and useful
object for the X-ray diffraction studies. Unlike for the metal-
free analog bearing identical peripheral substituents, a number
of higher order reflections are observed in the powder X-ray
diffraction pattern of 7e. This made possible the identification
of slightly different LC mesophases. We plan to investigate by
powder X-ray diffraction the miscibility of 7e with other
phthalocyanine materials and the morphology of such binary
blends.
Powder X-ray diffraction measurements were performed
on a Bruker D8 Advance diffractometer using Cu Ka radia-
˚
tion (l¼1.5418 A). All samples were prepared on thin pre-
cleaned aluminum plates. Diffraction patterns were collected
in the scattered angular range between 1.5ꢁ and 30ꢁ with the
angular resolution of 0.02ꢁ per step and a typical counting
time of 10 s per step, using the BraggeBrentano geometry
(q/2q set-up). X-ray spectra are represented as the scattering
intensity versus the wave-vector transfer q¼4p sin(q) lꢀ1
[Aꢀ1]. The sample temperature was controlled within
˚
0.1 ꢁC accuracy. To ensure reproducibility of results, several
heating and cooling cycles were performed using the same
sample.
Cyclic voltammetry experiments were performed with a
computer controlled EG&G PAR 273 potentiostat in a
three-electrode single-compartment cell (2 mL) under inert
atmosphere. The platinum working electrode consisted of
a platinum wire sealed in a soft glass tube with a surface of
A¼0.785 mm2, which was polished down to 0.5 mm with
Buehler polishing paste prior to use in order to obtain repro-
ducible surfaces. The counter electrode consisted of a platinum
wire and the reference electrode was an Ag/AgCl secondary
electrode. All potentials were internally referenced to the fer-
roceneeferrocinium (Fc/Fcþ) couple. All solutions were pre-
pared in freshly distilled anhydrous and deaerated CH2Cl2 or
THF containing 0.1 M [Bu4N][PF6] (TBAPF6, Fluka), which
was recrystallized twice from ethanol and dried in vacuum
prior to use.
4. Experimental section
4.2. Synthesis of diesters 5aee
4.1. General
Diethyl 4,5-dichlorophthalate 5a has been prepared from
the acid 4 according to the published procedure and its analyt-
ical data were identical to those published earlier.8 For homo-
logs 5bee, we slightly modified the same method.
All chemicals were purchased from Aldrich or Acros and
used without further purification unless stated otherwise. All

4160
B. Tylleman et al. / Tetrahedron 64 (2008) 4155e4161
4.2.1. Dipentyl 4,5-dichlorophthalate (5b)
the organic layer was separated, and the aqueous layer was ex-
tracted with AcOEt (50 mL). The combined organic extracts
were washed with H2O (50 mL), dried over MgSO4, and con-
centrated in vacuum. Column chromatography on SiO2
(CH2Cl2) afforded 330 mg (81%) of 3a. Colorless solid; mp
124e125 ꢁC; IR (KBr) (nmax/cmꢀ1): 3150 m, 3030 s, 2970 s,
2238 m (C^N), 1735 s (CO), 1462 m, 1367 s, 1211 s, 1134 s,
A mixture of acid 4 (20 mmol, 4.70 g), n-pentanol (6b,
10 mL, 90 mmol), H2SO4 (0.5 mL), and toluene (30 mL)
was placed in a 100-mL round-bottom flask equipped with
a Dean-Stark apparatus and heated to vigorous reflux for
15 h. The resulting mixture was cooled to room temperature,
washed with H2O (50 mL), 10% aqueous NaHCO3 (20 mL),
again H2O (50 mL), and dried over MgSO4. After evaporation
of solvents, the residue was purified by chromatography on
a short column of SiO2, eluent hexane/CH2Cl2 1:1. Yield
6.75 g (90%). Colorless oil; 1H NMR (300 MHz, CDCl3):
1
1026 s, 932 m, 938 m, 854 m, 787 m; H NMR (300 MHz,
3
3
CDCl3): d 1.40 (t, JH,H¼7.1 Hz, 6H), 4.42 (q, JH,H¼7.1 Hz,
4H), 8.13 (s, 2H); 13C NMR (75 MHz, CDCl3): d 13.9, 63.1,
114.0, 118.0, 133.8, 136.4, 164.0; HREIMS: m/z calcd for
C14H12N2O4 ([M]þ): 272.0797; found: 272.0801.
3
d 0.92 (t, JH,H¼7.1 Hz, 6H), 1.30e1.40 (m, 8H), 1.68e1.78
3
(m, 4H), 4.29 (t, JH,H¼7.0 Hz, 4H), 7.88 (s, 2H); 13C NMR
(75 MHz, CDCl3): d 13.9, 22.2, 27.9, 28.1, 66.3, 130.8,
131.7, 135.5, 165.6.
4.3.2. Dipentyl 4,5-dicyanophthalate (3b)
Prepared similarly to 3a from 5b (563 mg, 1.5 mmol). Col-
umn chromatography on SiO2 (CH2Cl2) afforded 442 mg
4.2.2. Dioctyl 4,5-dichlorophthalate (5c)
(83%) of 3b. Colorless solid; mp 67e71 ꢁC; IR (KBr) (nmax
/
Prepared similarly to 5b from n-octanol (6c, 7.8 mL,
50 mmol). Yield 75%. Colorless oil; 1H NMR (300 MHz,
cmꢀ1): 3040 m, 2950 s, 2845 s, 2239 m (C^N), 1733 s (CO),
1462 m, 1396 m, 1379 m, 1299 s, 1247 s, 1211 s, 1137 s, 1008
3
1
m, 948 s, 898 m; H NMR (300 MHz, CDCl3): d 0.92 (t,
CDCl3): d 0.88 (t, JH,H¼6.9 Hz, 6H), 1.20e1.45 (m, 20H),
3
1.68e1.78 (m, 4H), 4.29 (t, JH,H¼7.0 Hz, 4H), 7.79 (s, 2H);
3JH,H¼7.0 Hz, 6H), 1.30e1.42 (m, 8H), 1.68e1.80 (m, 4H),
13C NMR (75 MHz, CDCl3): d 14.1, 22.6, 25.9, 28.4, 29.1,
29.2, 31.8, 66.4, 130.8, 131.8, 135.5, 165.6.
4.35 (t, JH,H¼6.6 Hz, 4H), 8.12 (s, 2H); 13C NMR (75 MHz,
3
CDCl3): d 13.8, 22.2, 27.9, 28.0, 67.2, 114.0, 118.0, 133.8,
136.5, 164.1; HREIMS: m/z calcd for C20H24N2O4 ([M]þ):
356.1736; found: 356.1733.
4.2.3. Didodecyl 4,5-dichlorophthalate (5d)
Prepared similarly to 5b from n-dodecanol (6c, 9.3 g,
50 mmol). Yield 72%. Colorless oil; 1H NMR (300 MHz,
4.3.3. Dioctyl 4,5-dicyanophthalate (3c)
3
CDCl3): d 0.88 (t, JH,H¼6.7 Hz, 6H), 1.20e1.45 (m, 36H),
Prepared similarly to 3a from 5c (690 mg, 1.5 mmol). Col-
umn chromatography on SiO2 (hexane/AcOEt 10:1) afforded
493 mg (74%) of 3c. Colorless solid; mp 44e46.5 ꢁC; IR
(KBr) (nmax/cmꢀ1): 3035 w, 2945 s, 2905 s, 2835 s, 2237 m
(C^N), 1734 s (C]O), 1458 m, 1390 m, 1313 s, 1260 s,
3
1.66e1.78 (m, 4H), 4.29 (t, JH,H¼6.8 Hz, 4H), 7.79 (s, 2H);
13C NMR (75 MHz, CDCl3): d 14.0, 22.6, 25.8, 28.4, 29.2,
29.3, 29.45, 29.52, 29.57, 29.59, 31.9, 66.3, 130.8, 131.7,
135.4, 165.5.
1
1248 m, 1213 m, 1138 m, 935 m, 770 w, 720 w, 530 w; H
3
4.2.4. Bis(2-butyloctyl)-4,5-dichlorophthalate (5e)
NMR (300 MHz, CDCl3): d 0.88 (t, JH,H¼6.9 Hz, 6H),
Prepared similarly to 5b from alcohol 6e (11.2 mL,
50 mmol) with the following amendment; after purification
by chromatography the product, still containing the starting al-
cohol 6e was partitioned between hexane (100 mL) and MeOH
(100 mL). The upper hexane layer was separated and concen-
1.20e1.45 (m, 20H), 1.68e1.80 (m, 4H), 4.35 (t,
3JH,H¼6.8 Hz, 4H), 8.12 (s, 2H); 13C NMR (75 MHz,
CDCl3): d 14.0, 22.6, 25.8, 28.4, 29.11, 29.14, 31.7, 67.3,
114.0, 118.0, 133.8, 136.5, 164.1; HREIMS: m/z calcd for
C26H36N2O4 ([M]þ): 440.2675; found: 440.2671.
1
trated to give pure 5e. Yield 78%. Colorless oil; H NMR
(300 MHz, CDCl3): d 0.82e0.94 (m, 12H), 1.20e1.40 (m,
4.3.4. Didodecyl 4,5-dicyanophthalate (3d)
3
32H), 1.64e1.80 (m, 2H, CH), 4.20 (d, JH,H¼5.9 Hz, 4H),
Prepared similarly to 3a from 5d (857 mg, 1.5 mmol). Col-
umn chromatography on SiO2 (hexane/AcOEt 10:1) afforded
596 mg (72%) of 3d. Colorless solid; mp 65e65.5 ꢁC; IR
(KBr) (nmax/cmꢀ1): 2900 s, 2830 s, 2238 m (C^N), 1734 s
(C]O), 1453 m, 1306 m, 1258 m, 1199 m, 1133 m; 1H
7.77 (s, 2H); 13C NMR (75 MHz, CDCl3): d 13.98, 14.02, 22.6,
22.9, 26.6, 28.9, 29.6, 30.9, 31.2, 31.8, 37.2, 69.1, 130.8, 131.9,
135.4, 165.6.
3
4.3. Synthesis of dinitriles 3aed
NMR (300 MHz, CDCl3): d 0.88 (t, JH,H¼6.7 Hz, 6H),
3
1.20e1.45 (m, 36H), 1.68e1.80 (m, 4H), 4.35 (t, JH,H
¼
4.3.1. Diethyl 4,5-dicyanophthalate (3a)
6.8 Hz, 4H), 8.12 (s, 2H); 13C NMR (75 MHz, CDCl3):
d 14.1, 22.7, 25.8, 28.4, 29.2, 29.3, 29.47, 29.55, 29.59,
29.61, 31.9, 67.3, 114.0, 118.0, 133.8, 136.5, 164.1; HREIMS:
m/z calcd for C34H52N2O4 ([M]þ): 552.3927; found: 552.3916.
Diester 5a (436 mg, 1.5 mmol), Pd2(dba)3 (55 mg,
0.06 mmol), dppf (66 mg, 0.09 mmol), Zn powder (20 mg,
0.3 mmol), and Zn(CN)2 (210 mg, 1.8 mmol) were placed in
a dry flask flushed with argon. Dry N,N-dimethylacetamide
(6 mL) was added via syringe. The resulting mixture was
heated at 120 ꢁC for 2 h, then cooled to room temperature,
and partitioned between H2O (50 mL) and AcOEt (50 mL).
The resulting biphasic system was filtered through Celite,
4.3.5. 2,3,9,10,16,17,23,24-Octakis(ethoxycarbonyl)-
phthalocyanatozinc(II) (7a)
The same procedure as for the synthesis of 3a from 5a was
used with the following amendment; the reaction mixture was

B. Tylleman et al. / Tetrahedron 64 (2008) 4155e4161
4161
heated at 140 ꢁC for 16 h. The same workup followed by col-
umn chromatography on SiO2 (gradient from CH2Cl2 to
CH2Cl2/AcOEt 1:1) afforded 59 mg (13%) of 7a. Dark blue-
Supplementary data associated with this article can be found
in the online version, at doi:10.1016/j.tet.2008.03.004.
References and notes
1
green solid; H NMR (300 MHz, CDCl3þC5D5N): d 1.67 (t,
3
3JH,H¼7.2 Hz, 24H, CH3), 4.74 (d, JH,H¼7.2 Hz, 16H,
1. Gregory, P. J. Porphyrins Phthalocyanines 2000, 4, 432e437.
2. McKeown, N. B. Phthalocyanine Materials: Synthesis, Structure and
Function; Cambridge University Press: Cambridge, 1998.
3. Ali, H.; Van Lier, J. E. Chem. Rev. 1999, 99, 2379e2450; de la Torre, G.;
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M. J. Appl. Phys. Lett. 2005, 87, 132102.
CH2COO), 9.90 (s, 8H, CHarom); lmax (CH2Cl2): 352, 617,
687. HRMALDIMS: m/z calcd for C56H48N8O16Zn ([M]þ):
1152.2480; found: 1152.2500. IR (KBr) (nmax/cmꢀ1): 2960
m, 1734 s (C]O), 1358 m, 1262 s, 1180 m, 1097 s, 1078 s,
1016 m, 750 m.
5. Sergeyev, S.; Pouzet, E.; Debever, O.; Levin, J.; Gierschner, J.; Cornil, J.;
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Vol. 1, pp 657e672.
4.3.6. 2,3,9,10,16,17,23,24-Octakis(2-butyloctyl-1-oxy-
carbonyl)phthalocyanatozinc(II), mixture of
diastereoisomers (7e)
The same procedure as for the synthesis of 7a from 5a was
used with the following amendment; after the reaction mixture
was heated at 120 ꢁC for 2 h, DBU (0.30 mL, 2 mmol) was
added, the temperature was increased to 140 ꢁC, and the heat-
ing was continued for 16 h. The same workup followed by col-
umn chromatography on SiO2 (gradient from CH2Cl2 to
CH2Cl2/AcOEt 10:1) afforded 85 mg (10%) of 7e. Dark-green
11. Jin, F.; Confalone, P. N. Tetrahedron Lett. 2000, 41, 3271e3273; Didier,
D.; Sergeyev, S. Tetrahedron 2007, 63, 3864e3869.
1
waxy solid; H NMR (300 MHz, CDCl3þC5D5N): d 0.87 (t,
3
3JH,H¼7.0 Hz, 24H, CH3), 1.02 (t, JH,H¼7.0 Hz, 24H, CH3),
12. Woehrle, D.; Eskes, M.; Shigehara, K.; Yamada, A. Synthesis 1993, 194e
196.
1.25e1.70 (m, 128H), 2.00e2.10 (m, 8H, CHCH2COO),
13. Lee, C.-H.; Ng, D. K. P. Tetrahedron Lett. 2002, 43, 4211e4214.
14. Kopylovich, M. N.; Kukushkin, V. Y.; Haukka, M.; Luzyanin, K. V.;
Pombeiro, A. J. L. J. Am. Chem. Soc. 2004, 126, 15040e15041.
15. Poor solubility of this phthalocyanine derivative did not allow the mea-
surement of 13C NMR spectra as well as the determination of the molar
absorption coefficient from the UVevis spectrum.
3
4.55 (d, JH,H¼5.9 Hz, 16H, CH2COO), 9.89 (s, 8H, CHarom);
13C NMR (75 MHz, CDCl3þC5D5N): d 14.1, 14.2, 22.7, 23.2,
26.8, 29.1, 29.8, 31.2, 31.5, 31.9, 37.5, 69.4, 124.1, 133.9,
139.8, 154.1, 168.1; lmax (3, L cmꢀ1 molꢀ1, CH2Cl2): 352
(8.81ꢂ104), 617 (4.65ꢂ104), 687 (2.79ꢂ105). HRMALDIMS:
m/z calcd for C136H208N8O16Zn ([M]þ): 2273.5000; found:
2273.5037. IR (KBr) (nmax/cmꢀ1): 2905 s, 2840 s, 1734 s
(C]O), 1452 m, 1371 m, 1314 s, 1256 s, 1169 m, 1098 s,
1073 s, 1000 m, 746 m, 675 m.
16. Kobayashi, N.; Koshiyama, M.; Ishikawa, Y.; Osa, T.; Shirai, H.; Hojo, N.
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Acknowledgements
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This work has been financially supported by the European
Union (FP6-NAIMO integrated project NMP4-CT-2004-
500355), by FNRS (grant no. 2.4613.07), and by the Belgian
Federal Science Policy Office (PAI FS2). We thank Prof. R.
Flammang and co-workers (University of Mons) for the mea-
surement of mass spectra. R.G. is indebted to ‘Programa
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Ramon y Cajal’ for support. B.T. is a FRIA research fellow.
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