Grignard Reactions on Ortho Dicarboxylic Arene Derivatives. Synthesis of 1,3-Dithienylisothianaphthene Compounds

Article abstract of DOI:10.1021/jo9604402

1,3-Dithienylisothianaphthene (10a) is obtained through ring closure of 1,2-dithienoylbenzene (7a). The synthesis of 7a has been accomplished based on a Grignard reaction by adding 2-thiophene-magnesium bromide to 1,2-di(S-(2-pyridinyl)) benzenedithioate (6b) to obtain 7a in a yield of 95%. The use of 6b avoids the formation of the corresponding 3,3-dithienyl-3H-isobenzofuran-1(3H)-one (dithienylphthalide, 8). The same procedure is applied to obtain 1,3-dithienyl-4,5,6,7-tetradeuterioisothianaphthene (10b) and 1,3-dithienyl-4,5,6,7-tetrafluoroisothianaphthene (10c). The synthesis of the 2,3-dithienoylpyridine (12a), 3,4-dithienoylpyridine (12b), and 2,3-dithienoylpyrazine (12c) however fails. The presence of nitrogen in the central ring system influences the result of the Grignard reaction. Possibly the free electron pair of the nitrogen interferes with the formation of a stable six-membered ring intermediate which is essential for the diketone formation.

Full text of DOI:10.1021/jo9604402

J . Org. Chem. 1997, 62, 1473-1480
1473
Gr ign a r d Rea ction s on Or th o Dica r boxylic Ar en e Der iva tives.
Syn th esis of 1,3-Dith ien ylisoth ia n a p h th en e Com p ou n d s
Rafae¨l H. L. Kiebooms, Peter J . A. Adriaensens, Dirk J . M. Vanderzande,* and
J an M. J . V. Gelan
Institute for Materials Research (IMO), Division Chemistry, Limburg University, Universitaire Campus,
B-3590 Diepenbeek, Belgium
Received March 4, 1996X
1,3-Dithienylisothianaphthene (10a ) is obtained through ring closure of 1,2-dithienoylbenzene (7a ).
The synthesis of 7a has been accomplished based on a Grignard reaction by adding 2-thiophene-
magnesium bromide to 1,2-di(S-(2-pyridinyl)) benzenedithioate (6b) to obtain 7a in a yield of 95%.
The use of 6b avoids the formation of the corresponding 3,3-dithienyl-3H-isobenzofuran-1(3H)-one
(dithienylphthalide, 8). The same procedure is applied to obtain 1,3-dithienyl-4,5,6,7-tetradeuter-
ioisothianaphthene (10b) and 1,3-dithienyl-4,5,6,7-tetrafluoroisothianaphthene (10c). The synthesis
of the 2,3-dithienoylpyridine (12a ), 3,4-dithienoylpyridine (12b), and 2,3-dithienoylpyrazine (12c)
however fails. The presence of nitrogen in the central ring system influences the result of the
Grignard reaction. Possibly the free electron pair of the nitrogen interferes with the formation of
a stable six-membered ring intermediate which is essential for the diketone formation.
1. In tr od u ction
most promising results in this field were obtained by
McCullough et al.,12 who were able to synthesize soluble
alkyl-substituted and highly regioregular PT. Therefore,
it is worthwhile to develop a new class of materials in
which the already-demonstrated properties of PT are
combined with the promising electronic properties of
PITN. This class of polymers would consist of a well-
defined combination of thiophene and isothianaphthene
units. Moreover, since perfectly regioregular polymers12
show superior electronic properties and while tailoring
the bandgap is predicted to be easier in regular
copolymers,13-15 it is preferable to produce regular co-
polymers rather than random copolymers. In the case
where the regularity of the copolymer is a direct result
of the molecular structure of the monomer, we prefer to
classify these materials as formal copolymers. The most
obvious example of a formal copolymer is a polymer 1 in
which the monomeric compound combines ITN unit as
well as thiophene units. One interesting compound is
1,3-dithienylisothianaphthene (DTI, 10a ) in which two
thiophene rings are combined with one isothianaphthene
ring.16,17 The totally symmetric structure of the monomer
guarantees a high regularity in the copolymer structure.
The presence of thiophene rings on both sides of the
ITN unit will favor the aromatic over the quinoid ground-
state geometry. As far as the bandgap is concerned, a
value in between those of PT and aromatic PITN is thus
to be expected.13,15,18 Moreover, the thiophene ring
systems allows one to obtain easily processable polymers
Conducting polymers have been the subject of intensive
research for some time. The best known conducting
polymers are poly(aniline), poly(p-phenylenevinylene),
poly(pyrrole) (PP), and poly(thiophene) (PT). In the case
of these polymers techniques have been developed to
obtain good processability. Poly(isothianaphthene) (PITN)
is another conducting polymer with most intriguing
properties such as a low band gap of 1 eV and the ability
to become transparent upon doping. However PITN has
not yet found wide application in the development of
electronic devices due to the lack of a simple polymeri-
zation route, leading to a processable material. The main
problem should be attributed to the difficult accessibility
of monomeric isothianaphthene compounds. Extensive
work on isothianaphthene compounds has been ac-
complished by Cava et al.1-3 From their work it appears
that isothianaphthene monomers are relatively unstable
and their synthesis is laborious. Although progress has
been made on the development of a straightforward
polymerization route to PITN,4 it seems interesting to
develop on the other hand synthetic procedures which
lead to different types of monomeric isothianaphthene
derivatives. These compounds should combine the in-
teresting electronic properties of isothianaphthene with
the possibility of enhancing stability and processability
of the resulting polymer. The combination of the ITN
unit with other aromatic heterocycles is an approach
which is able to meet the requirements of enhanced
stability and processability. Indeed, the control of the
chemistry of for example PP and PT has made an
important step forward during the last decade.5-12 The
(8) Ba¨uerle, P.; Fischer, T.; Bidlingmeier, B.; Stabel, A.; Rabe, J . P.
Angew. Chem. 1995, 107, 335-339.
(9) Wang, C.; Schindler, J . L.; Kannewurf, C. R.; Kanatzidis, M. G.
Chem. Mater. 1995, 7, 58-68.
(10) Ba¨uerle, P.; Go¨tz, G.; Segelbacher, U.; Huttenlocher, D.; Me-
hring, M. Synth. Met. 1993, 55-57, 4768-4776.
(11) Miller, J . S. Adv. Mater. 1993, 5(9), 671-676.
(12) McCullough, R. D.; Lowe, R. D.; J ayaraman, M.; Anderson, D.
L. J . Org. Chem. 1993, 58, 904-912.
X Abstract published in Advance ACS Abstracts, February 1, 1997.
(1) Cava, M. P.; Pollack, N. M. J . Am. Chem. Soc. 1966, 88, 4112-
4113.
(2) Cava, M. P.; McGrady, J . J . Org. Chem. 1975, 40, 72-77.
(3) Cava, M. P.; Lakshmikantham, M. V. Phosphorus, Sulfur Silica
1989, 43(1-2), 95-109.
(13) Bakhshi, A. K.; Liegener, C. M.; Ladik, J . Synth. Met. 1989,
30, 79-85.
(4) Van Asselt, R. Synth. Met. 1995, 74(1), 65-70.
(5) Brooke, G. M.; Drury, C. J .; Bloor, D.; Swann, M. J . J . Mater.
Chem. 1995, 5(9), 1317-1320.
(14) Bakhshi, A. K. Asian J . Chem. 1990, 2(1), 1-10.
(15) Ku¨rti, J .; Surjan, P. R.; Kertesz, M. J . Am. Chem. Soc. 1991,
113, 9865-9867.
(6) Ru¨he, J .; Berlin, A.; Wegner, G. Macromol. Chem. Phys. 1995,
196, 225-242.
(16) Ba¨uerle, P.; Go¨tz, G.; Emerle, P.; Port, H. Adv. Mater. 1992,
4(9), 564-567.
(7) Bouachrine, M.; Lereporte, J . P.; Moreau, J . J . E.; Man, M. W.
C. J . Mater. Chem. 1995, 5, 797-799.
(17) Lorcy, D.; Cava, M. P. Adv. Mater. 1992, 4(9), 562-564.
(18) Ku¨rti, J .; Surja´n, P. R. Synth. Met. 1992, 49-50, 537-542.
S0022-3263(96)00440-9 CCC: $14.00 © 1997 American Chemical Society

1474 J . Org. Chem., Vol. 62, No. 5, 1997
Kiebooms et al.
Sch em e 1
through, for instance, use of thiophenes with additional
side chains. Certainly in the case of PT the incorporation
of side chains is a technique which is now common use
in improving solubility and therefore processability prop-
erties. Furthermore, 10a can be used in the develop-
ment of oligomers with tailored electronic properties.
Recently19-22 it was shown that one does not always need
polymers to obtain electronic materials with outstanding
properties. Even oligomeric compounds can meet the
criteria for materials used in the preparation of advanced
electronic devices. In the case of organic semiconducting
materials based on oligomers, the solid-state properties
are directly connected with these of the individual
molecules and their spatial order. Recently it appeared
to be possible to obtain devices with anisotropic proper-
ties20,22 through control of the mesoscopic order of oligo-
mers. The control of mesoscopic order is to a considerable
extent influenced by the nature of substituents and end
groups, a feature which can in its turn be controlled by
a well-chosen synthetic route. Oligomeric compounds not
only allow the obtention of materials with high purity
but also allow easy control of the electronic properties.
Moreover the structure of these compounds can readily
be determined by a whole series a spectroscopic methods,
facilitating thereby the unravelling of the correlation
between the structure and the resulting electronic prop-
erties. Finally, oligomers present an additional advan-
tage of allowing calculations23 to be performed at a highly
sophisticated level.
The most straightforward way to synthesize 1,3-
diarylisothianaphthene derivatives 2 is through ring
closure of ortho diketones 3 (Scheme 1) by means of
P4S1024 or Lawesson’s reagent.17,25 From literature16,17 the
preparation of these ortho diketones 3 appeared to be the
major bottleneck to elaborate an efficient isothianaph-
thene synthesis. Although the use of Diels-Alder-type
reactions24,26,27 has been proposed, the use of this type of
reaction for synthesis of a wide series of ortho diketone
derivatives is rather limited. Since it is known that the
Friedel-Craft-type reaction with phthaloyl dichloride
5a 16,28 on thiophene results in the formation of 3,3-
dithienylisobenzofuran-1(3H)-one 8 (Scheme 2), the use
of Grignard-type reactions on ortho dicarboxylic arenes
4 to make ortho diketones is the only alternative.
In a Grignard reaction with 2-thienylmagnesium bro-
mide as the Grignard reagent one can use different
substrates. In literature the use of 5a ,16,29 phthalic
anhydride30,31 and thiophthalic anhydride32,33 has been
reported in the synthesis of ortho diketones. However,
the results of different authors appeared not to be
entirely consistent with one another. Due to the incon-
sistency in literature data, we decided to revise the
synthesis of ortho diketones in order to develop a
convenient route to ortho diketones. Therefore we tested
the results of Grignard reactions on the above series of
substrates as well as on two new but no less interesting
substrates, 1,2-di(S-phenyl)benzenedithioate (6a ) and
1,2-di(S-(2-pyridinyl))benzenedithioate (6b). The latter
compounds have a thioester functional group, which is
reported to yield selectively ketones34,35 from Grignard
reactions.
Once an appropriate route to ortho diketones and thus
10a had been developed, we investigated the application
of this route in the synthesis of DTI derivatives (Scheme
1). Besides the synthesis of 1,3-dithienyl-4,5,6,7-tetra-
deuterioisothianaphthene (10b) and 1,3-dithienyl-4,5,6,7-
tetrafluoroisothianaphthene (10c), the synthesis of dif-
ferent nitrogen-substituted derivatives 13a , 13b, and 13c
was attempted.
(19) Geiger, F.; Stoldt, M.; Schweizer, H.; Ba¨uerle, P.; Umbach, E.
Adv. Mater. 1993, 5(12), 922-925.
(20) Horowitz, G.; Delannoye, P.; Bouchriha, H.; Deloffre, F.; Fave,
J . L.; Garnier, F.; Hajlaoui, R.; Heyman, M.; Kouki, F.; Valat, P.;
Wintgens, V.; Yassar, A. Adv. Mater. 1994, 6(10), 752-755.
(21) Hotta, S.; Waragai, K. Adv. Mater. 1993, 5(12), 896-908.
(22) Garnier, F.; Yassar, A.; Hajlaoui, R.; Horowitz, G.; Deloffre, F.
Electrochim. Acta 1994, 39(8/ 9), 1339-1344.
2. Resu lts a n d Discu ssion
2.1 Syn th esis of Or th o Dik eton es. As mentioned
before, the bottleneck in the synthesis of 10a was the
preparation of the ortho diketone 7a . We therefore first
focused on the synthesis of this compound, as the
synthesis of 10a by ring closure with P4S1024 or Lawesson
reagent17,25 is rather straightforward. For the synthesis
of 7a we investigated successively the Grignard reaction
of 2-thienylmagnesiumbromide on 5a , phthalic anhy-
(23) Cornil, J .; Bre´das, J . L. Adv. Mater. 1995, 7(3), 295-297.
(24) Volz, W.; Voss, J . J . Prakt. Chem. 1991, 333(6), 889-893.
(25) Shridar, D. R.; J ogibhukta, M.; Shantan Rao, P.; Handa, V. K.
Synthesis 1982, 1061-1062.
(26) Zweig, A.; Metzler, G.; Maurer, A.; Roberts, B. G. J . Am. Chem.
Soc. 1967, 89, 4091-4098.
(27) White, J . D.; Mann, M. E.; Kirshenbaum, H. D.; Mitra, A. J .
Org. Chem. 1971, 36, 1048-1053.
(28) Haller, A.; Guyot, A. C.R. Acad. Sci. 1894, 119, 139-142.
(29) J ensen, J . R. J . Org. Chem. 1960, 25, 269.
(30) Howell, L. B. J . Am. Chem. Soc. 1920, 42, 2333-2337.
(31) Blicke, F. F.; Weinkauff, O. J . J . Am. Chem. Soc. 1932, 54,
1446-1453.
(32) Schlessinger, R. H.; Ponticello, I. S. J . Chem. Soc., Chem.
Commun. 1969, 1013-1014.
(33) Omram, S. M. A. R.; Harb, N. S. J . Prakt. Chem. 1973, 315,
353-561.
(34) Cardellicchio, C.; Fiandanese, V.; Marchese, G.; Ronzini, L.
Tetrahedron Lett. 1985, 26(30), 3595-3598.
(35) Araki, M. Bull. Chem. Soc. J ap. 1974, 47(7), 1777-1780.

Ortho Dicarboxylic Arene Derivatives
J . Org. Chem., Vol. 62, No. 5, 1997 1475
dride, thiophthalic anhydride and the two thioester
compounds 6a and 6b.
quaternary carbon nucleus at 99.1 ppm. Compound 8
and 7a were also carefully analyzed by means of 2D NMR
techniques. In addition the structure of 8 was confirmed
by the characteristic loss of CO2 in mass spectroscopic
studies.
2.1.3. 1,2-Di(S-p h en yl) Ben zen ed ith ioa te a n d 1,2-
Di(S-(2-p yr id in yl)) Ben zen ed ith ioa te. Since 5a is too
reactive toward Grignard reactions and since phthalic
anhydride and thiophthalic anhydride do not possess a
very good leaving group, we investigated the use of a
2.1.1. P h th a loyl Dich lor id e. The investigation of
the Grignard reaction on 5a was based on the method of
J ensen.29 The reaction was performed by adding the
thienylmagnesium bromide to a solution of 5a in ether
at a temperature of -78 °C. However, only a yield of
about 10% was obtained, and the material contained a
certain amount of colored matter which was very difficult
to remove. Even the slow addition of the Grignard
reagent to a solution of 5a in THF at -78 °C or the use
of a 1:2 toluene mixture31 resulted in a very poor yield of
the ortho diketone 7a besides the formation of alcohols
and many other side products. These results were later
confirmed by Ba¨uerle et al.,16 who did not succeed at all
in obtaining 7a . Apparently, two acid chlorides in the
ortho position are too reactive toward this kind of
nucleophilic substitution even at lower temperatures.
2.1.2. P h th a lic An h yd r id e a n d Th iop h th a lic An -
h yd r id e. Another possible starting product in this
reaction is phthalic anhydride. Since the reactivity
toward a second nucleophilic substitution is seriously
reduced after the opening of the anhydride ring system
we performed the Grignard reaction at somewhat higher
temperatures than usual. Therefore, we used refluxing
solvent mixtures of toluene/ether in a ratio of 1:2, 1:3,
and 4:1.31 According to qualitative TLC analysis of the
reaction mixtures, the best results were obtained in the
solvent mixture with a ratio of 1:2 (boiling temperature
of 58 °C). After purification by means of column chro-
matography a yield of 15% of the ortho diketone 7a was
obtained. However, a significant amount of 8 (29%) was
also obtained. Performing the reaction at lower temper-
atures did not improve the yield of the ortho diketone
7a .
As sulfur has better leaving group characteristics, we
performed analogous reactions on thiophthalic anhydride.
The synthesis of thiophthalic anhydride was carried out
following the method of Reissert et al.36 In analogy to
the previous Grignard reaction on phthalic anhydride,
the Grignard reaction was carried out in a refluxing 1:2
toluene/ether mixture. The work-up of the final reaction
mixture was accompanied by considerable evolution of
H2S. However, the main reaction product appeared to
be compound 8. From a solid probe MS analysis (+CI
mode) of the reaction products, obtained from a reaction
carried out in pure THF solution, it appeared that
monosubstituted thiocarboxylate is formed as an impor-
tant intermediate. When diethyl ether at 0 °C is used
as solvent a precipitate is formed during addition of the
Grignard reagent. The yield of ortho diketone 7a is
higher than in the other cases (40%). When the reaction
is carried out in diethyl ether at room temperature, one
obtains a yield of about 60%. Apparently, lower temper-
atures favor the formation of monosubstituted intermedi-
ates. This indicates that the thiocarboxylate formed after
the first attack by the Grignard reagent does not contain
a suitable leaving group.
more convenient functional group, i.e. a thioester.
A
dithioester compound has two functional groups with a
lower reactivity as compared to 5a . Cardellicchio et al.34
describe a highly efficient route to ketones through
reaction of Grignard reagents with S-phenyl thioesters
in the presence of iron catalysts. Another method for
efficient synthesis of ketones is reported by Araki et al.35
and is based on the use of S-(2-pyridinyl) thioesters.
Therefore we have to synthesize the corresponding S-
phenyl thioester 6a and S-(2-pyridinyl) thioester 6b.
Thus in a first approach for the synthesis of the
S-phenyl thioester 6a , 5a was added slowly to a solution
of thiophenol and triethylamine (TEA) in tetrahydrofuran
(THF) according to the method of Araki et al.35 (Scheme
2). This resulted however in the formation of two
reaction products. Since both products possess the same
molecular mass, we were dealing with two isomeric
compounds. The first product is characterized by an IR
absorption at 1670 cm-1 and the 1H NMR spectrum
shows a typical symmetric substitution of the benzene
ring. The other product possesses an IR-absorption at
1770 cm-1, a 1H NMR spectrum showing a typical
asymmetric substitution of the benzene ring, the presence
of an aliphatic quaternary carbon nucleus at 99.1 ppm
and the loss of CO2 in solid probe MS analysis (+CI
mode). From this spectroscopic data we can conclude
that the first product should be the desired thioester 6a .
The second product, however, should possess a 3,3-
bis(phenylthio)isobenzofuran-1(3H)-one structure 9. Care-
fully monitoring the reaction as a function of time
revealed that there occurs a conversion from 6a to 9. At
room temperature this process takes a few days but at
elevated temperatures the conversion is completed within
an hour. Moreover when the reaction is carried out in
the presence of an excess of thiophenol, 9 appeared to
transform into two other products. The first one could
be identified as being the phenyl disulfide based on mass
spectroscopy and melting point (61 °C). The second
product possesses an IR-absorption at 1770 cm-1, the 13
C
NMR spectrum indicates the presence of an aliphatic
quaternary carbon nucleus at 86.4 ppm, and the 1H NMR
spectrum still showed the asymmetric substitution on the
benzene ring. But at 6 ppm a new signal appeared with
an integration corresponding with one hydrogen nucleus.
All this spectroscopic data indicates the formation of
3-(phenylthio)isobenzofuran-1(3H)-one (11) in which one
of the thiophenol groups is replaced by a hydrogen
nucleus. The formation of disulfide in the presence of
an excess of the corresponding thiol indicates that radical
scavenging has taken place. Indeed it is known that
thiols act as radical scavengers37 with formation of the
corresponding disulfide. Since the radical scavenging is
accompanied with a proton transfer, a stable radical is
formed at the 3-position of the structure of 9. Indeed,
The specific structure of the isomer 8 was proved by
means of IR-spectroscopy, the carbonyl group of γ-lac-
tones absorbing at higher energy (ν ) 1750 cm-1) than
the one of the diketone 7a (ν ) 1630 cm-1). Moreover,
1H NMR spectroscopy shows a coupling pattern of an
asymmetric ortho-substituted benzene ring and the 13C
NMR spectra shows the chemical shift of an aliphatic
(37) Lowry, T. H.; Richardson, K. S. Mechanism and theory in
organic chemistry; Harper & Row Pbl.: New York, 1981; pp 701-703.
(36) Reissert, A.; Holle, H. Ber. Dtsch. Chem. Ges. 1911, 3027-3040.

1476 J . Org. Chem., Vol. 62, No. 5, 1997
Kiebooms et al.
Sch em e 2
the radical is not only stabilized by delocalization in the
aromatic ring system but it is also stabilized by delocal-
ization in the thiophenol group. This explains the
replacement of the thiophenol group by a proton in
presence of an excess of thiophenol. Starting from a
solution of 9 in THF and heating it up in the presence of
a large excess of thiophenol yielded an almost quantita-
tive conversion into 11 and the formation of an equimolar
amount of disulfide.
In order to obtain mainly the thioester 6a we need
therefore to work at lower temperatures with a slight
deficiency of thiophenol. Moreover, since the reaction
proceeds quite quickly one needs to stop this reaction at
an early stage. Therefore, 5a was added rapidly to a
vigorously stirred solution of thiophenol and TEA in THF
at 0 °C. When addition was completed, the reaction was
immediately quenched by addition of an HCl-solution
(1%). Since the lactone 9 is soluble in diethyl ether but
not the thioester 6a , purification can be done by simple
crystallization from dichloromethane/diethyl ether, giving
a yield of 77%. An alternative for this route is the
method of Sheenan et al.38 This method consists in
adding 5a dropwise at a temperature of 0 °C to thiophe-
nol in a methanolate solution. The thioester 6a precipi-
tates from solution therefore preventing any isomeriza-
tion to the lactone structure resulting in a yield of about
94%.
Grignard reactions on compounds containing ortho car-
bonyl oxygen nuclei, as observed in the Grignard reaction
on phthalic anhydride and thiophthalic anhydride.
Since we had control of the thioester synthesis, the next
step consisted in performing the Grignard reaction in
presence of iron catalysts. Therefore the Grignard
reagent was slowly added at 0 °C to the thioester 6a in
a solution of THF in the presence of a catalytic amount
of tris(acetylacetonate) iron(III). However this reaction
did not result in the formation of the 1,2-dithienoylben-
zene and a significant amount of 9 was isolated.
Since the use of 6a did not yield 7a , we used instead
of 6a the S-(2-pyridinyl) thioester 6b.39 This thioester
was prepared according to the adapted method of Araki
et al.35 We did not succeed in preparing 6b according to
the method described by Sheehan et al.38
The high reactivity of S-(2-pyridinyl) thioesters toward
Grignard reagents with selective formation of ketones
was attributed to the formation of a stable six-membered
intermediate which would prevent further reaction. The
stable complex should in our case also prevent any
intramolecular isomerization by “freezing” the intermedi-
ate in an organometallic complex (Figure 1). The final
elimination occurs during acid work-up, causing the
organometallic complex to break up. Thus the Grignard
reagent was added slowly to 6b in a solution of THF at
0 °C (Scheme 2). No precipitate was formed during
reaction, allowing homogeneous mixing of the reaction
products throughout the addition process. The reaction
was finally quenched by addition of HCl (10%). After a
Since it appears that the process of lactone formation
is thermodynamically favored, one may also expect this
kind of intramolecular cyclization reaction to occur during
(38) Sheehan, J . C.; Holland, G. F. J . Am. Chem. Soc. 1956, 78,
5631-5633.
(39) Mukaiyama, T.; Araki, M.; Takei, H. J . Am. Chem. Soc. 1973,
95(14), 4763-4765.

Ortho Dicarboxylic Arene Derivatives
J . Org. Chem., Vol. 62, No. 5, 1997 1477
F igu r e 1. The formation of two six-membered complexes
during the Grignard reaction on 1,2-di(S-(2-pyridinyl)) ben-
zenedithioate.
F igu r e 2. Compounds 12 and 13.
0.27 and 0.18 eV, respectively, in their most stable
geometric structure. Therefore, aza and diaza derivatives
of ITN are the most interesting systems to be used in a
formal copolymer. Since we established a convenient
route toward the synthesis of ortho diketones, we inves-
tigated to what extent this method can be applied for the
synthesis of aza and diaza derivatives of PITN. On the
basis of our method we tried out the synthesis of
dithienylthieno[2,3-c]pyridine (13a ), dithienylthieno[3,4-
c]pyridine (13b), dithienylthieno[2,3-c]pyrazine (13c)
through the synthesis of the corresponding ortho dike-
tones 12a , 12b and 12c (Figure 2). An additional feature
is that these compounds can be used to get an ap-
proximation of the spectroscopic characteristics of the
corresponding aza and diaza ITN homopolymers.
2.2.1 Dith ien ylth ien o[2,3-c]p yr id in e. By using the
methods based on PCl5 and SOCl2 to synthesize the
corresponding phthaloyl dichloride, 2,3-pyridinoyl dichlo-
ride (14a ) was obtained in a yield of 90%. The synthesis
of the S-(2-pyridinyl) thioester 15a was performed using
the TEA method with a yield of 68%. It should be noticed
that 15a is not soluble in THF or other solvents suitable
for Grignard reactions. The only solvent appeared to be
pyridine, but this is not a good Grignard solvent since
the Grignard reagent readily decomposes.42
At first the Grignard reaction was carried out in the
usual way in a solution of THF at 0 °C. However, the
characteristic IR absorption at 1760 cm-1, the presence
of an aliphatic quaternary carbon signal at 86.8 ppm, and
the loss of CO2 in the mass spectra indicate the formation
of a compound with the 3,3-dithienylfuropyridin-1(3H)-
one 16a ,b structure in relatively high yield of 64%. Even
carrying out the reaction at higher temperatures to
enhance solubility did not solve the problem. Since we
obtained almost a single pure compound, the question
arises whether the pyridine nitrogen is situated at the
carbonyl side 16a or at the aliphatic side 16b of the 3,3-
dithienylfuropyridin-1(3H)-one compound (Scheme 3).
A detailed structure analysis based on the use of a
combination of 2D 1H-13C heteronuclear correlation NMR
experiments optimized for J ) 140 Hz and J ) 8 Hz helps
to elucidate the structure of the obtained compound. The
full chemical shift assignment has been carried out as
on the previous compounds and is included as Supporting
Information. The presence of a long-range correlation
signal between C1 and H7 and the absence of a correla-
tion signal between C3 and a pyridine proton indicate
the nitrogen to be situated at the aliphatic side of the
3,3-dithienylfuropyridin-1(3H)-one compound. The reac-
tion product therefore possesses structure 16b (3,3-
dithienylfuro[5,6-c]pyridin-1(3H)-one).
classical work-up a yield of 95% of the ortho diketone 7a
was obtained. Eventually the product can be used in the
next reaction without further purification.
From these results it is clear that the use of thioesters
in the synthesis of ortho diketones presents several
important advantages. This S-(2-pyridinyl) thioester
method is the first reported highly efficient and selective
synthesis of ortho diketones. Moreover the synthesis of
the thioester is straightforward and does not require
laborious and time-consuming purifications.
2.1.4. Syn th esis of Deu ter a ted a n d F lu or in a ted
Or th o Dik eton es. Since the deuterated 5b and fluori-
nated 5c phthaloyl dichloride derivatives are not com-
mercially available, we have to start with the synthesis
of the corresponding phthaloyl dichloride from the cor-
responding ortho dicarboxylic acid. Two methods were
tested. The method using PCl5 appeared to give better
results as compared to the SOCl2 method. The former
gives a yield of around 90% for most of the ortho
dicarboxylic compounds.
Next, the method as described in Scheme 2 was
followed for the synthesis of the deuterated 6c and
fluorinated 6d 1,2-dithienoyl benzene. The deuterated
compound does not show an important difference as far
as the chemical reactivity is concerned. Therefore it
could be synthesized in a straightforward way according
to the synthesis developed above.
Due to the high electronegativity of the fluorine
nucleus, the reactivity of the carbonyl group is enhanced.
For synthesis of the corresponding phthaloyl dichloride
5c this is not a problem, but for the synthesis of the S-(2-
pyridinyl) thioester 6d it is. Preparation of 6d based on
the use of TEA as a base appeared not to be successful.
6d could however be isolated through addition of 5c to a
sodium methanolate solution of 2-mercaptopyridine at
-78 °C. The best results were obtained in a dry, oxygen-
and moisture-free atmosphere as the product is much
more reactive than the protonated derivative. The tet-
rafluoro diketone 7c was obtained via the Grignard
reaction by adding 2-thienylmagnesium bromide to a
solution of 6d in THF at 0 °C. The yield of 87% is
comparable to the yield of 7a .
2.2. Syn th esis of Nitr ogen Der iva tives. From
theoretical calculations on polymers40,41 it appeared that
the replacement of carbon atoms in the ITN ring system
by nitrogen atoms influences the relative stabilities of
the aromatic and quinoid forms. From analysis of the
calculated electronic properties it appeared that there is
a dependence not only on the nature of the fused rings
but also on the positions of the nitrogens. The 4,5-diaza
and 4,7-diaza polymers appeared to be quite promising:
they present very small calculated energy gap values,
2.2.2 Dit h ien ylt h ien o[3,4-c]p yr id in e. Since the
synthesis of 12a was not successful, we tried to perform
the synthesis of the 3,4-pyridine derivative 12b. Al-
(40) Nayak, K.; Marynick, D. S. Macromolecules 1990, 23, 2237-
2245.
(41) Quattrocchi, C.; Lazzaroni, R.; Kiebooms, R.; Vanderzande, D.;
Gelan, J .; Bre´das, J . L. Synth.Met. 1995, 69, 691-692.
(42) Houben-Weyl; Nu¨tzel, K. Houben-Weyl 1993, Band 13/ 2a, 54-
75.

1478 J . Org. Chem., Vol. 62, No. 5, 1997
Kiebooms et al.
Sch em e 3
compared to the protonated 10a should be attributed to
the presence of the isotope effect.
3. Con clu sion
DTI derivatives could be of great interest for the
development of semiconducting materials with tailor-
made electronic properties as well as for spectroscopic
and theoretical evaluation of structure-property rela-
tionships. Therefore our aim was to develop an efficient
synthesis which makes it possible to prepare other DTI
derivatives. Since an efficient method for the synthesis
of 10a was not available previously, we developed a
highly specific and efficient synthesis route. In this
method, the synthesis of ortho aryldiketones is the major
bottleneck. A detailed evaluation of available starting
compounds to be used in Grignard reactions was es-
sential. For the synthesis of the 1,2-dithienoylbenzene
(7a ) we investigated successively the Grignard reaction
of 2-thienylmagnesium bromide on 5a , phthalic anhy-
dride, thiophthalic anhydride, 6a and 6b. On the one
hand 5a appeared to be too reactive toward the reaction
with 2-thienylmagnesium bromide, but on the other hand
the reaction on phthalic anhydride and thiophthalic
anhydride yielded, besides small to reasonable amounts
of the 7a , significant quantities of the isomeric 8. The
Grignard reaction on 6b yielded selectively almost pure
ortho diketone 7a . This result was attributed to the
formation of a stable six-membered organometallic com-
plex. In an analogous reaction on 6a according to the
method of Cardellicchio et al.34 the 3,3-di(S-phenyl-
)isobenzofuran-1(3H)-one (9) was formed.
The synthesis of the deuterated 10b and fluorinated
10c DTI derivatives was successfully carried out. How-
ever, attempts of synthesizing the 2,3-pyridine 13a , 3,4-
pyridine 13b, and 2,3-pyrazine 13c derivatives failed at
the level of Grignard reaction to obtain the 2,3-dithi-
enoylpyridine 12a , 3,4-dithienoyl pyridine 12b, and 2,3-
dithienoylpyrazine 12c. The introduction of nitrogens in
the aromatic ring system seemed to interfere with the
formation of a stabilized six membered intermediate. In
the case of the 2,3-pyridine the formation of the 3,3-
dithienylfuro[5,6-c]pyridin-1(3H)-one structure 16b is
favored due to the difference in reactivity of both carbonyl
functional groups caused by the inherent asymmetry of
the ring system as a consequence of the presence of only
one nitrogen.
F igu r e 3. Compounds 17 and 18.
though the 3,4-pyridinoyl dichloride (14b) could be
obtained in a yield of 91%, we were not able to isolate
15b. The reaction based on TEA resulted mainly in the
formation of the 2-pyridine disulfide.
2.2.3 Dith ien ylth ien o[3,4-c]p yr a zin e. In the syn-
thesis of the pyrazinoyl dichloride (14c) a yield of only
about 30% was obtained. This was mainly due to
decomposition at higher temperatures. Also for the S-(2-
pyridinyl) thioester 15c syntheses, lower yields of about
40% were obtained as compared to other thioester
syntheses. Again spectroscopic data indicated the forma-
tion of the lactone compound 3,3-dithienylfuro[2,3-
c]pyrazin-1(3H)-one (16c; IR 1765 cm-1 13C NMR 85.1
,
ppm) in the Grignard reaction. A possible solution for
this problem is to make use of the fact that the pyrazine
possesses two nitrogens. The idea was if one carries out
the Grignard reaction on the S-phenyl thioester 15d we
can use both nitrogens of the pyrazine ring system for
the formation of the organometallic complex. Unfortu-
nately no diketone was formed in the Grignard reaction.
Instead mainly two products 17 and 18 were isolated as
shown in Figure 3, besides some unreacted S-phenyl
thioester 15d . The structure of compound 17 and 18 was
confirmed by IR and mass spectroscopic data. Additional
evidence for the structure of compound 17 and 18 was
also obtained by a full chemical shift assignment based
on 1D and 2D NMR homo- and heteronuclear correlation
experiments.
2.3. Syn th esis of DTI Der iva tives by Rin g Clo-
su r e of Or th o Dik eton es. Finally the isothianaphthene
core is formed through ring closure of the ortho diketone
7a by means of P4S10 or Lawesson’s reagent.17 Both
24
procedures were performed but the procedure based on
the use of Lawesson’s reagent appeared to be more
efficient and easier to workup as compared to the use of
P4S10. In the latter case one also has to counter the
formation of important amounts of H2S. The overall yield
of 10a based on this reaction scheme is 51%. This is the
highest overall yield for the synthesis of 10a reported so
far. The overall yield of 10b and 10c are comparable to
that of the protonated DTI.
Exp er im en ta l Section
Syn th etic P r oced u r es. Solvents were dried and distilled
prior to use. THF was distilled over Na/benzophenone, CH3CN
was distilled from CaH2, and CH2Cl2 was distilled from P2O5.
All compounds were crystallized or distilled prior to use.
Products were purchased from Acros Chimica (previously
J anssen Chimica). 3,4,5,6-Tetradeuteriophthalic acid (99.4
atom %) was purchased from Icon Services Inc. 3,4,5,6-
Tetrafluorophthalic acid was purchased from Aldrich. All
The NMR data of 10b confirms our assignment of C4/
C7 and C5/C6 of the isothianaphthene ring. Indeed, the
signals of deuterated carbon nuclei show a triplet because
2H is a I ) 1 nucleus. The difference of 0.5 ppm as

Ortho Dicarboxylic Arene Derivatives
J . Org. Chem., Vol. 62, No. 5, 1997 1479
reaction mixtures were dried over MgSO4. All NMR spectra
were recorded in CDCl3, the shifts are reported in ppm relative
to TMS unless specified otherwise.
once. Immediately the reaction was then quenched by adding
200 mL of HCl (1%). After extraction with CHCl3 the
combined fractions were washed with 500 mL of NaOH (10%),
500 mL of NaHCO3 (1 M) and 500 mL of water and dried.
Crystallization from CH2Cl2/diethyl ether yielded 4.4 g (84%).
mp 109.7 °C; IR (KBr, ν, cm-1) 1680, 1655, 1420; MS (EI, m/ z)
242 (M+ - S - Ar), 214 (M+ - COS - Ar); 1H NMR 7.27, 7.61,
7.71, 7.74, 7.84, 8.59; 13C NMR 123.7, 128.5 , 130.4, 132.0,
136.8, 137.2, 150.4, 151.3, 190.2.
1,2-Di(S-(2-p yr id in yl)) 3,4,5,6-Tetr a d eu ter ioben zen e-
d ith ioa te (6c). The same procedure as for 6b was followed:
yield 77%; IR (KBr, ν, cm-1) 1680, 1650, 1570, 1560, 1535,
1450, 1420; MS (EI, m/ z) 356, 246, 108, 78.
Th iop h th a lic An h yd r id e. Phthalic anhydride (40 g, 0.27
mol) was thoroughly mixed with 80 g (0.33 mol) of NaS2‚9H2O.
The resulting liquid was stirred for 5 h. Addition of 100 mL
of water gave a yellow solution which was added slowly to 2 L
of HCl (5%). When the addition was complete, the mixture
was stirred for 1 h and filtered. The residue was dissolved in
CHCl3, washed with NaHCO3 (1 M) and H2O, and dried. After
crystallization from CHCl3/n-hexane, 35 g of white thiophthalic
anhydride crystals was obtained (yield 78%): mp 105.5 °C;
FTIR (KBr, ν, cm-1) 1780, 1690, 1655; MS (EI, m/ z) 164 (M+),
1
104 (M+ - COS), 76 (M+ - (CO)2S); H NMR 7.82 (dd, 2, J )
1,2-Di(S-(2-pyr idin yl)) 3,4,5,6-Tetr aflu or oben zen edith io-
a te (6d ). The reaction was carried out in a glovebox under
nitrogen atmosphere at an ambient temperature of 10 °C due
to the reactivity of the thioester and its sensitivity toward
moisture. A sodium methanolate solution was prepared by
adding at 0 °C 0.015 mol (0.35 g) Na to 50 mL of methanol
and 0.0168 mol (1.86 g) of 2-mercaptopyridine and subse-
quently cooled down to -78 °C. A solution of 0.0084 mol (2.3
g) of 5c in 25 mL of toluene was added dropwise under vigorous
stirring. The precipitate was filtered off and rapidly washed
with cold methanol (-78 °C) yield 1.53 g (43%); mp 71.5 °C
decomposition; IR (KBr, ν, cm-1) 1690, 1655, 1560, 1490; MS
2.9/5.1 Hz), 7.97 (dd, 2, J ) 2.9/5.1 Hz); 13C NMR 123.7 (CH),
135.0 (CH), 138.7 (C), 189.8 (C0).
o-Ar yld ica r bon yl Ch lor id es. A. o-Aryldicarboxylic acid
(0.0084 mol) and 0.0252 mol (5.25 g) of PCl5 were slowly heated
until 180 °C was reached (caution: HCl evolution at
a
temperature of about 60 °C). The mixture was kept for 2 h at
180 °C under vigorous stirring and then cooled to rt. The
remaining PCl5 was removed by filtration of the liquid into a
vacuum distillation apparatus. The reaction flask was washed
with 10 mL of toluene, and the solvent was filtered into the
apparatus. Vacuum distillation yielded a liquid which was
further used in the thioester synthesis.
1
(EI, m/ z) 424 (M+), 333; H NMR 7.30, 7.73, 8.60; 13C NMR
B. A mixture of 18 mL of toluene and 0.1 mol of distilled
SOCl2 and 0.0084 mol of o-aryldicarboxylic acid were refluxed
for 1.5 h. The solvent and remaining SOCl2 were distilled off,
and the product was further purified by vacuum distillation.
3,4,5,6-Tetr a d eu ter iop h th a loyl d ich lor id e (5b): yield
1.46 g (84%); bp 204 °C (5 mmHg); IR (NaCl, ν, cm-1) 1780,
1750, 1550.
3,4,5,6-Tetr a flu or op h th a loyl d ich lor id e (5c): yield 2.2
g (94%); bp 180 °C (5 mmHg); IR (NaCl, ν, cm-1) 1770, 1490;
MS (CI, m/ e) 275 (MH+), 239; 13C NMR 120.0, 143.6, 145.5,
161.5; 19F NMR (fluorobenzene, 400 MHz, in ppm relative to
CFCl3) -134.56, -144.82.
2,3-P yr id in oyl d ich lor id e (14a ): yield 1.56 g (91%); bp
140 °C (4 mmHg); IR (NaCl, ν, cm-1) 3500, 3080, 1780, 1740,
1550; MS (CI, m/ z) 204 (MH+), 168 (MH+ - Cl); 1H NMR 7.72,
8.32, 8.84; 13C NMR 127.0, 129.0, 138.6, 149.45, 153.0, 166.2,
167.4.
121.7, 124.3, 130.2, 137.5, 142.2, 144.9, 149.7, 150.6, 184.0;
19F NMR (fluorobenzene, 400 MHz, in ppm relative to CFCl3)
-135.81, -147.31.
1,2-Dith ien oylben zen e (7a ). 2-Bromothiophene (4.5 mL,
46 mmol) in 50 mL of THF was added to 1.2 g (46 mmol) of
Mg in 50 mL of THF. After stirring for 3.5 h, this solution
was slowly added to 7.95 g (23 mmol) of 6b in 150 mL of THF
at 0 °C. After this solution was stirred for 30 min, 200 mL of
HCl (10%) was added. The mixture was extracted with diethyl
ether, and the combined fractions were washed with 500 mL
of NaOH (10%), 500 mL of NaHCO3 (1 M), and H2O, and finally
dried. A light brown product was obtained in a yield of 95%.
This product can be used as such in further reactions.
Crystallization from CHCl3/n-hexane resulted in white crys-
tals: mp 148-149 °C; IR (KBr, ν, cm-1) 1620, 1585, 1570, 1510,
1410; MS (EI, m/ z) 298 (M+), 215 (M+ - COAr), 187 (M+
-
1
COAr), 111 (COAr), 104, 76; H NMR 7.03, 7.44, 7.60, 7.63,
7.70; 13C NMR 128.0, 129.2, 130.6, 134.9, 135.1, 139.3, 144.0,
188.2. Anal. Calcd for C16H10O2S2: C, 64.4; H, 3.4. Found:
C, 64.17; H, 3.28.
3,4-P yr id in oyl d ich lor id e (14b): yield 1.56 g (91%); bp
145 °C (4 mmHg); IR (NaCl, ν, cm-1) 3500, 2940, 2840, 1780,
1660, 1560; MS (EI, m/ z) 205 (M+), 169 (M+ - Cl), 140 (M+
-
CO), 113 (M+ - COCl - CO), 106 (M+ - COCl - Cl), 78 (M+
- 2COCl); 1H NMR 7.62, 8.83, 8.97; 13C NMR 121.9, 125.8,
141.7, 150.1, 153.0, 166.8, 168.0.
1,2-Dith ien oyl-3,4,5,6-tetr a d eu ter ioben zen e (7b): yield
88%; IR (KBr, ν, cm-1) 1620, 1545, 1510, 1410, 1350, 1330,
1280; MS (EI, m/ z) 302, 273, 257, 219, 203, 191, 119, 111, 83.
2,3-P yr a zin oyl d ich lor id e (14c): yield 0.5 g (29%); bp 125
°C (4 mmHg); IR (NaCl, ν, cm-1) 3500, 3040, 1780, 1730, 1550,
1530; MS (EI, m/ z) 205 (M+), 169 (M+ - Cl),113 (M+ - COCl
- CO), 106 (M+ - COCl - Cl), 78 (M+ - 2COCl);1H NMR 8.91;
13C NMR 144.4, 146.8, 166.8.
1,2-(S-P h en yl)ben zen ed ith ioa te (6a ). A. A solution of
5 mL of TEA, 15 mL of THF, and 1.5 mL (0.0146 mol, 1.609 g)
thiophenol was stirred for 15 min at 0 °C. A solution of 1 mL
(0.0069 mol, 1.409 g) 5a in 10 mL of THF was added.
Immediately the reaction mixture was then worked up by
adding 200 mL of HCl (1%). After extraction with CHCl3 the
combined fractions were washed with a NaOH (10%) solution
and H2O and finally dried. Crystallization from CH2Cl2/diethyl
ether yielded 1.8 g (77%).
1,2-Dith ien oyl-3,4,5,6-tetr aflu or oben zen e (7c). The same
procedure as for 7a was followed using the following con-
centrations: 2 mL (20 mmol) 2-bromothiophene in 50 mL of
THF was added to 0.5 g (20 mmol) of Mg in 50 mL of THF.
This solution was added to 4.2 g (10 mmol) of crude 6d in 150
mL of THF at 0 °C. Purification was performed by crystal-
lization from CHCl3/n-hexane or by column chromatography
(silica, CHCl3/n-hexane): yield 3.5 g (95%); mp 118 °C; IR
(KBr, ν, cm-1) 1620, 1510, 1470, 1410, 1375; MS (EI, m/ z) 370
(M+), 325, 287, 111, 83; 1H NMR 7.09, 7.51, 7.74; 13C NMR
123.5, 128.6, 136.2, 136.9, 141.6, 143.1, 144.8, 180.5; 19F NMR
(fluorobenzene, 400 MHz, in ppm relative to CFCl3) -136.68,
-150.35. Anal. Calcd for C16H6O2F4S2: C, 51.9; H, 1.6.
Found: C, 51.39; H, 1.53.
3,3-Dith ien ylisoben zofu r a n -1(3H)-on e (8). 5a (0.6 mL,
4 mmol) and 1.276 g of AlCl3 were mixed thoroughly for 5 min
at 0 °C. Slowly 1 mL (12 mmol) of thiophene in 20 mL of
CH2Cl2 was added. The mixture was allowed to warm up to
rt and was stirred for another 30 min. The mixture was
poured in 100 mL of ice with 10 mL of HCl (37%). The product
was extracted with ether, dried, and purified by column
chromatography (n-hexane/CHCl3). Crystallization resulted
in white crystals with a yield of 0.76 g (64%): mp 99.6 °C; IR
(KBr, ν, cm-1) 1760, 1590, 1450, 1415; MS (EI, m/ z) 298 (M+),
253 (M - CO2), 221, 111; 1H NMR 6.94, 7.06, 7.29, 7.56, 7.66,
7.71, 7.90; 13C NMR 86.3, 123.5, 124.8, 125.9, 126.8, 127.1,
B. 5a (5.8 mL 0.04 mol) was added dropwise at 0 °C to 8.2
mL (0.08 mol) of thiophenol in a methanolate solution prepared
by adding 1.74 g of Na to 50 mL of methanol. The precipitate
was filtered off and washed with H2O and ice-cold methanol:
yield 13.2 g (94%); mp 130.3-130.5 °C; IR (KBr, ν, cm-1) 1670
(νCOS), 1570, 1210 (νCOSAr), 1190 (νCOSAr), 745(doublet); MS (EI,
m/ z) 351 (M+1), 241 (M+ - SAr), 213 (M+ - COSAr), 109
1
(SAr), 104 (ArCO+), 76 (Ar+); H NMR 7.42, 7.52, 7.60, 7.82;
13C NMR 191.6 , 137.1, 134.6, 131.6, 129.6, 129.2, 128.3, 127.4.
1,2-Di(S-(2-p yr id in yl)) Ben zen ed ith ioa te (6b). A solu-
tion of 5 mL of TEA, 50 mL of THF, and 3.3 g (0.030 mol)
2-mercaptopyridine was stirred for 15 min at 0 °C. A solution
of 2.2 mL (0.015 mol) of 5a in 50 mL of THF was added all at

1480 J . Org. Chem., Vol. 62, No. 5, 1997
Kiebooms et al.
127.3, 130.0, 134.6, 143.9, 151.9, 168.7. Anal. Calcd for
C16H10O2S2: C, 64.4; H, 3.4. Found: C, 64.16; H, 3.29.
3,3-Di(S-p h en yl)isoben zofu r a n -1(3H)-on e (9). A solu-
tion of 5 mL of TEA, 15 mL of THF, and 1.5 mL (0.0146 mol,
1.609 g) of thiophenol was stirred for 15 min at room temper-
ature. A solution of 1 mL (0.0069 mol, 1.409 g) of 5a in 10
mL of THF was added. The mixture was stirred for another
2 h. HCl (200 mL, 1%) was then added. After extraction with
CHCl3 the combined fractions were washed with a NaOH
(10%) solution and H2O and finally dried. The product was
purified by column chromatography (silica, CHCl3/n-hexane)
and crystallization from hexane to yield 1.9 g (79%): mp
101.9-102.3 °C; IR (KBr, ν, cm-1) 1770, 1465, 1440; MS (CI
and EI, m/ z) 351 (M + 1), 306 (M - CO2), 241 (M - SAr), 197
(M-CO2 - SAr), 109 (SAr), 104 (ArCO+), 76 (Ar+); 1H NMR
7.16, 7.26, 7.32, 7.38, 7.44, 7.64, 7.71; 13C NMR 99.1, 123.3,
124.5, 125.8, 128.3, 128.7, 129.78, 129.82, 134.2, 136.4, 148.7,
167.1.
1,3-Dith ien ylisoth ia n a p h th en e (10a ). A. To a solution
of 0.58 g (2 mmol) of 7a in 40 mL of dried CH3CN was added
1.7 g (6.1 mmol) of P4S10 and 2.0 g (24 mmol) of NaHCO3. After
stirring for 4 h at a 30 °C, 50 mL of H2O was added. The
precipitate formed was filtered and dissolved in diethyl ether.
After extraction of the remaining water solution with diethyl
ether, the combined fractions were dried. Further fast puri-
fication was done through repeated crystallizations by adding
n-hexane to a saturated CHCl3 solution and combining the
fractions containing 10a . A final purification was performed
through column chromatography (silica, n-hexane/CHCl3) and
crystallization from n-hexane/CHCl3 resulting in fluorescent
orange crystals (52%).
103.5-103.8 °C; IR (KBr, ν, cm-1) 1750 (νCOO lactone), 1590,
1450, 1420; MS (EI, m/ z) 242 (M+), 133 (M+ - SAr), 109 (SAr),
1
76 (Ar+); H NMR 6.71, 7.47-7.51, 7.69, 7.64, 7.77; 13C NMR
86.4 , 123.4, 125.3, 126.1, 128.8, 129.0, 129.9, 130.2, 133.6,
134.2, 146.0, 169.0.
2,3-Di(S-(2-p yr id in yl)) P yr id in ed ith ioa te (15a ). A solu-
tion of 5 mL of TEA, 15 mL of THF, and 1.1 g (10 mmol) of
2-mercaptopyridine was stirred for 15 min at 0 °C. A solution
of 5 mmol of 14a in 10 mL of diethyl ether was added.
Immediately the reaction mixture was then worked up by
adding 200 mL of HCl (1%). After extraction with CHCl3, the
combined fractions were washed with 500 mL of NaOH (10%)
and 500 mL of H2O and finally dried. The product was purified
by crystallization from CH2Cl2/diethyl ether to yield 1.2g
(68%): mp 145 °C; IR (KBr, ν, cm-1) 1675, 1560, 1550, 1440,
1410; MS (EI, m/ z) 353 (M+), 243 (M+ - Spyr), 215 (M+
-
Spyr - CO), 187 (M+ - Spyr - 2CO), 105 (M+ - 2Spyr - CO),
78 (M+ - 2Spyr - 2CO); 1H NMR 7.24-7.31, 7.61, 7.67-7.79,
7.91, 8.57, 8.65, 8.80; 13C NMR 123.6, 123.9, 127.2, 130.3,
130.7, 133.6, 135.8, 137.1, 137.4, 147.6, 150.4, 150.4, 150.5,
150.8, 151.7, 189.9, 189.9.
2,3-Di(S-(2-p yr id in yl)) P yr a zin ed ith ioa te (15c). Syn-
thesis was as described for 15a : yield 0.8 g (46%); mp 137.6
°C; IR (KBr, ν, cm-1) 1675, 1570, 1440, 1410, 1255; MS (EI,
m/ z) 244 (M - Spyr), 216 (M - COSpyr), 188, 156, 111, 78;
1H NMR 7.26-7.32, 7.72-7.75, 8.60, 8.80; 13C NMR 123.8,
130.4, 137.3, 145.8, 146.0, 150.6, 150.8, 188.7.
2,3-Di(S-P h en yl) P yr a zin ed ith ioa te (15d ). Synthesis
was as described for 15a : yield 0.98 g (57%); mp 151.2-151.8
°C; IR (KBr, ν, cm-1) 1670, 1525, 1450, 1420, 1370, 1250; MS
(EI, m/ z) 243, 215, 187, 160, 133, 109, 77, 65; 1H NMR 7.40-
7.45, 7.52-7.55, 8.76; 13C NMR 126.4, 129.4, 129.9, 134.8,
145.7, 146.4, 189.6.
B. A mixture of 0.42 g (1.4 mmol) of 7a , 0.4 g (1.4 mmol) of
Lawesson reagent, and 50 mL of CH2Cl2 were stirred for 30
min at 30 °C. After evaporation of the CH2Cl2, 50 mL of
ethanol was added and the mixture was refluxed for 20 min.
Finally 100 mL of H2O was added, and the product was
extracted with diethyl ether. The combined diethyl ether
fractions were washed with 500 mL of NaOH (10%) and 500
mL of H2O and dried. The ether was evaporated, and the
remaining solid was taken up in a minimum quantity of CHCl3
and precipitated by adding a large quantity of n-hexane. The
solid was filtered, and this procedure was repeated several
times. All fractions containing almost pure product were then
combined and subjected to final column chromatography
(silica, n-hexane) (64%): mp 96-97 °C; IR (KBr, ν, cm-1) 1520,
3,3-Dith ien ylfu r o[5,6-c]p yr id in -1(3H)-on e (16b). Syn-
thesis was as described for 7a using 15a : yield 4.4 g (64%);
mp 142 °C; IR (KBr, ν, cm-1) 3090, 3050, 1760, 1500, 1580,
1475, 1420, 1350, 1300, 1280; MS (EI, m/ z) 299, 255, 222; 1H
NMR 6.96, 7.20, 7.32, 7.53, 8.22, 8.94; 13C NMR 86.8, 118.8,
124.8, 126.9, 127.3, 127.5, 134.7, 142.0, 155.9, 166.9, 169.4.
3,3-Dith ien ylfu r o[2,3-c]p yr a zin -1(3H)-on e (16c). Syn-
thesis as described for 7a using 15c: yield 5.0 g (73%); mp
101.3 °C; IR (KBr, ν, cm-1) 1765, 1530, 1460, 1415, 1370, 1335,
1
1280; MS (EI, m/ z) 300, 256, 223; H NMR 6.95, 7.17, 7.33,
8.88, 8.93; 13C NMR: 85.1, 127.0, 127.6, 137.4, 140.8, 148.2,
149.1, 163.3, 164.4.
1215, 1180; MS (EI, m/ z) 298 (M+), 253, 221, 149, 132 (M+
2Ar); 1H NMR 7.13, 7.14, 7.34, 7.36, 7.94; 13C NMR 121.5,
-
Gr ign a r d Rea ction on 15d . Synthesis was as described
for 7a using 15d .
124.8, 125.5, 125.6, 126.5, 127.9, 135.4, 135.7; UV-vis (λmax
ꢀ) in n-hexane 426 (14 440), 283 (16 819), 220 (19 909).
,
Com p ou n d 17: yield 0.85 g (8.6%); mp 164.1-164.8 °C;
IR (KBr, ν, cm-1) 1680, 1540, 1500, 1470, 1430, 1410, 1370,
1350; MS (EI, m/ z) 434, 325, 297, 133, 109; 1H NMR 7.11,
7.45-7.50, 7.53-7.59, 7.62, 7.98, 9.14; 13C NMR 127.0, 127.7,
128.9, 129.40, 129.44, 129.8, 129.9, 132.8, 133.5, 134.93,
134.97, 139.5, 141.0, 141.3, 142.9, 148.7, 189.6, 191.7.
Com p ou n d 18: yield 2.7 g (31%); mp 143.1-143.7 °C; IR
(KBr, ν, cm-1) 3200, 1440, 1420, 1370, 1350, 1280, 1250; MS
(EI, m/ z) 384, 285, 256, 162, 111.
1,3-Dit h ien yl-4,5,6,7-t et r a d eu t er ioisot h ia n a p h t h en e
(10b): yield 64%; mp 95.6-96.0 °C; IR (KBr, ν, cm-1) 1525,
1425, 1405, 1245; MS (EI, m/ z) 302, 268, 257, 225, 151; 1H
NMR 7.14, 7.34, 7.37; 2H NMR (CHCl3, 400 MHz, in ppm
relative to CDCl3 at 7.24 ppm) 7.99, 7.18; 13C NMR 121.1,
124.3, 125.5, 125.5, 126.4, 127.9, 135.2, 135.6.
1,3-Dith ien yl-4,5,6,7-tetr aflu or oisoth ian aph th en e (10c).
A mixture of 0.5 g (1.4 mmol) of 7c, 0.4 g (1.4 mmol) of
Lawesson’s reagent, and 50 mL of CH2Cl2 were stirred for a
maximum of 1 h at 45 °C. Working up was as for 10a .
Column chromatography (silica, n-hexane) yielded 0.48 g
(95%): mp 184.6 °C; IR (KBr, ν, cm-1) 2920, 1660, 1560, 1470,
Ack n ow led gm en t. The authors are indebted to
DSM (Geleen), the Instituut tot Aanmoediging van
Wetenschappelijk Onderzoek in Nijverheid en Land-
bouw (IWONL) and the Vlaams Instituut voor de
Bevordering van het Wetenschappelijk-Technologisch
Onderzoek in de Industrie (IWT) for a predoctoral
fellowship to R. K. Also the assistance of Ing. F.Genne´
in the synthesis of some compounds is gratefully ac-
knowledged.
1
1415; MS (EI, m/ z) 370 (M+), 203 (M+ - 2Ar); H NMR 7.11,
7.43; 13C NMR 121.8, 127.8, 127.8, 127.9, 129.2, 132.7, 137.1,
139.1; 19F NMR (fluorobenzene, 400 MHz, in ppm relative to
CFCl3) -145.68, -161.70; UV-vis (λmax, ꢀ) in n-hexane: 400
(12 656), 269 (16 372), 227 (23 159).
3-(S-P h en yl)isoben zofu r a n -1(3H)-on e (11). A solution
of 100 mL of TEA and 18 mL (263 mmol) of thiophenol was
stirred for 15 min at room temperature. A solution of 6 mL
(41.4 mmol) of 5a in 50 mL of THF was added. The reaction
mixture was stirred for 48 h at rt or 10 h at 60 °C and was
then worked up by adding 200 mL of HCl (1%). After
extraction with CHCl3, the combined fractions were washed
with NaOH (10%) and H2O and finally dried. The product was
purified by column chromatography (silica, CHCl3/n-hexane)
and crystallization from hexane to yield 8.7 g (87%): mp
Su p p or tin g In for m a tion Ava ila ble: NMR spectra and
structure analysis and detailed NMR-data (58 pages). This
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