2-Substituted (Azulen-1-yl)ethenes

Article abstract of DOI:10.1002/ejoc.200300346

An easy and efficient solvent-free synthesis of 1-(azulen-1-yl)-2-aryl- and heteroarylethenes is described. The reaction was performed simply by melting solid mixtures of azulenic Schiff bases and arylacetic acids, the crude products being purified by column chromatography. Limitations of the method were established by study of a large range of aryl and heteroarylacetic acids and also by examination of various azulenic Schiff bases. The same reaction was observed with other active methylene compounds, such as malonic acid and its derivatives or 1,3-diketones. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.

Full text of DOI:10.1002/ejoc.200300346

FULL PAPER
2-Substituted (Azulen-1-yl)ethenes
Alexandru C. Razus,*[a] Carmen Nitu,[a] Victorita Tecuceanu,[b] and Valentin Cimpeanu[b]
Keywords: CϪC coupling / Nitrogen heterocycles / Schiff bases / Solvent-free synthesis
An easy and efficient solvent-free synthesis of 1-(azulen-1-
yl)-2-aryl- and heteroarylethenes is described. The reaction
was performed simply by melting solid mixtures of azulenic
Schiff bases and arylacetic acids, the crude products being
purified by column chromatography. Limitations of the
method were established by study of a large range of aryl
and heteroarylacetic acids and also by examination of vari-
ous azulenic Schiff bases. The same reaction was observed
with other active methylene compounds, such as malonic
acid and its derivatives or 1,3-diketones.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2003)
Introduction
Previously employed methods for the generation of vinyl-
azulenes followed classical routes generally used for substi-
tuted alkenes.[8] The Wittig reaction (starting from azulene
carbaldehydes or azulene ylides, in the presence of strong
bases) seems to be the most widely used, and the obtained
yields are satisfactory to good.[7d,9,10] Reductive conden-
sation of azulenecarbaldehydes with low-valent titanium
(the McMurry reaction[9b]) also proceeds with good results
[yields between 40 and 70 %, with only (E) geometry]. Ap-
plication of this method, however, is limited by the exclusive
generation of symmetrically substituted ethenes, the lack of
reproducibility and the incompatibility of many substrates
with Ti0. The Siegrist condensation[11] and the Heck reac-
tion[12] have also been used for a few particular products.
Some examples of the construction of a CϭC bond start-
ing from aromatic azomethines (obtained mainly from ke-
tones) and from compounds with activated methylene
groups, such as malononitrile, cyanoacetic acid, cyanoacet-
amide and nitroalkanes, have also been described in the lit-
erature.[13,14] Usually the condensation is performed in solu-
tion and/or in the presence of strong bases or acids as cata-
lysts, but in most reported examples[14,15] only addition to
the double bond CϭN was observed, without subsequent
amine elimination. Interest in this method ceased and com-
pounds with CϭO groups were preferred for condensations.
During our continuing researches on 1-substituted azu-
lenes with double bonds, compounds 1, we have studied
the synthesis and the physicochemical, electrochemical and
optical properties of azo azulene 1 (X ϭ Y ϭ N)[1] and of
the corresponding Schiff bases 1 (X ϭ CH and Y ϭ N).[2]
From the synthetic point of view the reported compounds
are important because they are the building blocks for the
generation of complex molecular structures.[3] Recently,
azulene derivatives, especially compounds belonging to
these two classes, have been receiving increasing attention
because of their valuable optical and electrochemical
properties: as dyes,[4] for the elaboration of nonlinear op-
tical (NLO) materials[5] or for the generation of chemically
modified electrodes with polymeric films on their sur-
faces.[6] The results encouraged us to extend our investi-
gations on the corresponding alkenes 1 (X ϭ Y ϭ CH).
Although these conjugated systems exhibit high hyperpola-
rizability, offering candidates for NLO systems,[7] and al-
though they are also useful for synthetically purposes, no
simple and efficient synthesis for this class of compounds
has been mentioned in the literature until now.
Results and Discussion
The very simple availability of azulenic Schiff bases,[2]
their ease of handling and the difficulties occurring in the
synthetic procedures described above suggested that we
could attempt the development of a versatile route for the
generation of vinylazulenes through condensations between
these bases and compounds containing activated methylene
groups, starting from aryl- and heteroarylacetic acids.
[a]
Technical University Darmstadt, Institute of Organic
Chemistry,
Petersenstr. 22, 64287 Darmstadt, Germany
[b]
Romanian Academy, Institute of Organic Chemistry,
Spl. Independentei 202B, 060023 Bucuresti 15, P. O. Box 254,
Romania,
E-mail: acrazus@cco.ro
Supporting information for this article is available on the
WWW under http://www.eurjoc.org or from the author.
Eur. J. Org. Chem. 2003, 4601Ϫ4610
DOI: 10.1002/ejoc.200300346
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4601

A. C. Razus, C. Nitu, V. Tecuceanu, V. Cimpeanu
FULL PAPER
In attempts to carry out the condensation in solvents
such as xylene at reflux (6 h) or in acetic acid (heating for
5 h) we recovered the starting reagents 2 and 3 almost quan-
titatively.
The reaction was performed in a flask protected against
humidity. The temperature was maintained above 100 °C,
at which the mixture of reagents was liquid (under this tem-
perature the reaction either occurred slowly or failed). After
10 min of heating, CO2 began to evolve vigorously from
the melted reaction mixture. At the top of the flask, para-
anisidine sublimed progressively and at the end of the reac-
tion time, the sublimed anisidine could be washed and re-
moved with a small amount of solvent. The workup of the
reaction mixture consisted only of chromatographic separ-
ation. From the condensation conditions reported in
Table 1, it can be seen that the use of both a molar ratio of
2(OCH3)/3(H), 1:1 and a reaction time of 4 h (Table 1, En-
try 1) are satisfactory for a good conversion of Schiff base
and a high yield of 1-styrylazulene [9(H)] (above 80 % and
95 %, accordingly).
An attractive procedure currently widely used in modern
synthesis eliminates the use of the solvent as reaction me-
dium. We therefore studied the possibility of condensing the
two reagents by heating them in the absence of any solvent
or catalyst, and the results were very good. Preliminary
experiments were carried out in order to establish the most
favourable reaction conditions. For this purpose, the cheap
and commercially available phenylacetic acid 3(H) was con-
densed with different Schiff bases 2 (starting with 2(OCH3),
see Scheme 1).
The 1-styrylazulene [9(H)] proved to be formed exclus-
ively in the (E) geometry; this feature was generally encoun-
tered for the obtained ethenes. In certain cases the genera-
tion of dimers 15 or 16 (in yields 10Ϫ15 %) at longer reac-
tion condensation times is worth mentioning (Scheme 2).
We also investigated the limitations of the procedure, en-
larging the field of Schiff bases 2 and arylacetic acids used
and maintaining the reaction conditions described above.
The results, as listed in Table 2, show a dramatic decrease
in reactivity, correlated with electron-donating ability in the
series: OCH3 ഠ N(CH3)2 Ͼ CH3 Ͼ H Ͼ CN. The presence
of the CN group strongly lowers both the degree of conver-
sion and the yield, while that of NO2 completely hinders
the condensation and produces only tar. Syntheses of eth-
enes from Schiff bases with various substituents at the azu-
lene five- or seven-membered rings are currently under
investigation.
As would be expected, the structures of the arylacetic ac-
ids play an important role in the condensation, so a large
number of acetic acid derivatives (3Ϫ8) were condensed
with the Schiff base 2(OCH3)[16] (see Table 3).
The reactivities of the phenylacetic acids 3 increase with
the withdrawing strength of the para substituent in the or-
der Cl Ͻ H Ͻ NO2. The reaction occurred rapidly and al-
most quantitatively for the ortho- and para-nitrophe-
Scheme 1
Table 1. Condensations between Schiff base 2(OCH3) and phenylacetic acid 3(H)
Entry
Reaction conditions
Molar ratio 2/3 Time (h) Other conditions
Recovered 2(OCH3) (%) Yield in 9(H) (%)
1
2
3
4
5
6
7
8
9
1:1
1:1
1:1.5
1:1
1:1.5
1:2
1:1
1:1
1:1
4
4
4
6
6
6
4.5
7
4.5
120 °C[a] (melted mixture)
18
95[b]
95[b]
70[b]
79[b]
35[c]
37[c]
Ϫ
grinding the mixture of 2 and 3, then 120 °C (melt.) 20
135 °C (melted mixture)
120 °C (melted mixture)
120 °C (melted mixture)
120 °C (melted mixture)
toluene at reflux
xylene at reflux
acetic acid at reflux
12
20
25
18
100
100
100
Ϫ
Ϫ
[a]
[b]
[c]
Temperature in the oil bath. Together with alkene, its dimer 15 was separated in a yield of under 1%. The yield of dimer 15 was
between 10 and 15%; the rest of the obtained material remained at the start of the chromatographic column.
4602
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2-Substituted (Azulen-1-yl)ethenes
FULL PAPER
nylacetic acids 3(oNO2) and 3(pNO2) and for thienylacetic
acid 5, and good results were also obtained from the con-
densation of 4-pyridineacetic acid hydrochloride 6·HCl.
The described condensation provides a convenient method
for the preparation of compounds 9(oNO2), 9(pNO2) or 10,
as well as for other 1-(azulen-1-yl)-2-arylethenes Ϫ which
are difficult or even impossible to obtain in other ways. The
reaction between 1-azuleneacetic acid (7) and 2(OCH3)
occurs in good yield, although the availability of the acid
limits the importance of this method in comparison with
other syntheses of 1,2-diazulenylethene (13).[9b] The stereo-
controlled pathway of the reaction may explain the better
results in the condensation of β-naphthaleneacetic acid 4β
in comparison with its α isomer 4α. Steric hindrance is
strong in the condensation between phenylacetic acid and
the Schiff base with the 4,6,8-trimethylazulene moiety; in
this case only azulenic hydrocarbon could be separated
from the reaction mixture.
In the condensation of acid 8, together with the ‘‘nor-
mal’’ condensation product 14, another product, 17 Ϫ un-
expectedly condensed at the indene methylene Ϫ was gener-
ated (Scheme 2).
Attempts to perform the condensation of Schiff bases
with chloroacetic or diphenylacetic acid failed, as did treat-
ment of phenylacetic acids with the bases obtained from the
ketones such as 1-acetylazulene.
Scheme 2
Since the proposed condensation procedure is straight-
forward and high-yielding, we used it for the synthesis of
polycyclic linear or cyclic compounds containing alternat-
ing benzenoid moieties, azulene moieties and double bonds.
As starting reagents we considered compounds with at least
two reacting groups (CH2CO2H or CHϭNar).
Table 2. Condensations between Schiff bases 2(R) and phenylacetic
acid 3(H)
[b]
R[a]
OCH3 N(CH3)2 CH3
H
CN NO2
Recovered 2(R) (%) 18
15
95
21
95
39 45
85 50
30
Thus, by condensation of 1,2- and 1,4-phenylenediacetic
acids or 1,3-azulenediacetic acid with two equivalents of
Schiff base 2(OCH3), we obtained the polycyclic com-
pounds 18, 20 or 21(Az) with highly extended electronic
conjugation (Scheme 3).
Yield in 9(H) (%)
95
0[c]
[a]
The reactions were carried out at 120 °C in the melted mixture,
[b]
the ratio 2(R):3(H) ϭ 1:1 and the reaction time was 4 h.
After
heating for 6.5 h. [c] Only unchanged reagent and tar were obtained.
Table 3. Condensations between Schiff base 2(OCH3) and arylacetic acids 3(Ar)-8
Acid[a]
Obtained ethylene[b]
Reaction conditions
Recovered 2(OCH3), (%)
Yield (%)
3(H)
3(pNO2)
3(oNO2)
3(pCl)
4α
9(H)
9(pNO2)
9(oNO2)
9(pCl)
10α
240 min
30 min
120 min
240 min
240 min
60 min
15 min
18
3
17
13
32
15
9
32
26
40
62
95
95
90[c]
94
76
86
4β
10β
5
11
12
98
6[d]
5 min, ratio 2(OCH3)/6 (1:1)
25[e]
82
60 min, ratio 2(OCH3)/6 (1:2), 100 °C
7
8
13[f]
14
240 min
8 h
81
[g]
[a]
The reactions were carried out at 120 °C in the melted mixture, the molar ratio 2(OCH3)/3Ϫ8 ϭ 1:1. [b] The structures of the resulting
[c]
ethylene and of the starting arylacetic acids are presented in Scheme 1. Together with alkene, its dimer 16 was separated in a yield of
[d]
[e]
about 7%. 6·HCl was used. 4-Picoline was detected in the reaction mixture; the tendency for decarboxylation to 4-picoline became
important when the reaction temperature was high (Ͼ120 °C) or when the reaction time was prolonged.[f] Reported yields of 13[9b] are
55% and 68% for Wittig and for McMurry approaches, respectively.[g] The yield of product 14 was under 6% and of the double conden-
sation product 17, about 20% (the structures of these products are shown in Scheme 2).
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A. C. Razus, C. Nitu, V. Tecuceanu, V. Cimpeanu
FULL PAPER
Scheme 3
Although the condensation of 1,4-phenylenediacetic acid
to provide compound 20 occurred in good yield based on
reacted Schiff base, a large amount of starting compounds
remained unchanged even after a long reaction time (in-
creasing amount of para-xylene was detected in the reaction
mixture), probably due to the very high melting point of
the acid. The low condensation yield of the 1,2-phenylene-
diacetic acid can be attributed to the steric and chemical in-
teractions between the ortho groups in the starting acid or
Scheme 4
These results obtained from the condensation of aryl- or
in the resulting dialkene. The product 18 (as the trans-trans heteroarylacetic acids encouraged us to extend the solvent-
isomer)[17] was thus obtained in 10 % yield after 2 h at 148 free condensation of azulenic Schiff bases to other active
°C [recovered 2(OCH3), 30 %], together with an interesting methylene compounds. The few results reported until
cyclic compound, 19(A), separated in 7 % yield (Scheme 3). now[13,15,19] relating to the condensation of aromatic imines
When starting from 1,3-azulenediacetic acid[18] and with various methylene compounds are rather ambiguous
2(OCH3), the compound 21(Az) with three azulene moiet- and generally refer to the reaction in solution.
ies, separated by two double bonds, was generated in about
40 % yield [recovered 2(OCH3) 35 %].
The methylenic compounds 27Ϫ32 considered
(Scheme 5), with different hydrogen mobility,[20,21] reacted
Condensations between the azulenic 1,3-bis(imino) com- with Schiff base 2(OCH3) under conditions similar to those
pound 22 and two mol of arylacetic acids occurred with used for arylacetic acids; the results are reported in Table 4.
satisfactory results.
A mixture of 1,3-distyrylazulene With increasing hydrogen mobility in the series Ϫ indene
[21(C6H5)][9d] (43 %), the monocondensation product 23 (14 32, arylacetic acids, malonic acid 27, cyanoacetic acid 28
%) and its hydrolysis derivative, compound 24 (Ͻ 5 %), was and malononitrile 29 Ϫ an augmentation in reactivity can
obtained (Scheme 4) and was separated without difficulties be observed. The unexpectedly slow condensation of ethyl
on an alumina column. The 3,3Ј-bis(imino)-1,1Ј-biazulene[2] acetoacetate (30) and especially acetylacetone (31), and the
showed the same behaviour and the distyryl-substituted moderate yields obtained can be explained by the high enol-
product 25 (Scheme 3) was obtained together with the hy- ization tendencies of the reagents. Another interesting fea-
drolysed monocondensed product 26.
ture of the condensation lies in the difference between the
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2-Substituted (Azulen-1-yl)ethenes
FULL PAPER
Product Characterisation[23,24]
The structural assignment of 1-azulene-2-arylethenes
does not give rise to any major problems.[25] For these com-
pounds the presence of the AB group with coupling con-
stants of about 16 Hz [characteristic of two ethylene pro-
tons in (E) geometry] at low field must be signalled. How-
ever, the structure peculiarities of the by-products 15, 16,
17 and 19 produced together with the ethenes is described
more thoroughly.
For the dimers 15 and 16 (Scheme 2) the problem lies
in the position of the second azulene moiety in the ethane
skeleton. The gem relationship of the two azulenes was con-
firmed by the NOE responses of 8Ј-H and 8ЈЈ-H on the
irradiation of 1-H. Another interesting feature of com-
pounds 15 or 16 is represented by the nonequivalence of
the two protons at C-2; bulk substituents at C-1 are likely
to hinder the free rotation about the (C-1)Ϫ(C-2) bond.
A NOE experiment between 2-CH3 and Hexo was also
used to establish the methylene geometry at C-1 in com-
pound 17.
In the condensation of 1,2-phenylenediacetic acid, two
structures 19(A) or 19(B) may be generated by the intramol-
1
ecular cyclization of 18.[26] The H NMR spectrum of 19
shows one doublet at δ ϭ 7.87 ppm (J ϭ 1.8 Hz) for a vi-
nylic proton coupled with an allylic proton and one dd at
δ ϭ 3.03 ppm (J ϭ 16.0, 1.8 Hz), one dd at δ ϭ 3.75 ppm
Scheme 5
exclusive generation of (E) isomers for the arylacetic acids (J ϭ 16.0 and 8.4 Hz) and one dt at δ ϭ 5.23 ppm (J ϭ 8.6
and isomer mixtures for other methylenic compounds. and 1.8 Hz) for the sequence ϪCH2ϪCH(azulenyl)-. The
Although low yields are obtained in some cases for the coupling constants show that the aliphatic sequence belongs
condensations of methylenic derivatives, the above pro- to a rigid five- or six-membered cyclic structure, 19(A) or
cedure represents a valuable method for the syntheses of 19(B), respectively (see Scheme 3). From a 2D-long-range
various functionalized vinylazulenes and, sometimes, a un- correlation experiment (HMBC) showing a three-bond dis-
ique way to generate them.
tance between the vinylic hydrogen and C-2 in azulene,
It is more difficult to establish the solvent-free reaction structure (A) was proposed. No NOE was observed be-
mechanism than in the case of reactions occurring in solu- tween the Hexo protons and 2-H, indicating a possible syn
tion because very often only spectral measurements (when relationship of the Hexo and phenyl.
possible), together with the structures of starting materials
Of products 33Ϫ40, only for 34 and 35 does the struc-
and of products, are the sole arguments for the proposal of tural assignment seem to be more difficult (most of the ana-
a reaction route.[22] We consider that our results are far lytical data for these compounds are reported in the ESI).
from allowing us to propose a coherent reaction pathway.
Other attempts are in progress and may eventually support C4HazϪ and the cis relationship of the azulene moieties is
a mechanism suggestion. attested to by the chemical shifts of the protons (four dis-
For compound 34, the sequence ϪAzC2HϪC3H2Ϫ
Table 4. Condensation reactions between azulene Schiff bases 2(OCH3) and methylene compounds
ZϪCH2ϪW (starting reagent)
Product
Reaction conditions: time, molar ratio[a]
2(OCH3)/CH2ZW
Recovered
2(OCH3) (%)
Yield
(%)
Z
W
CO2H
CO2H
CN
CH3CO
CH3CO
Indene (32)
CO2H (27)
CN (28)
33
35
37
38
39
40
60 min, 1
30 min, 1
10 min, 1
4 h, 0.5
4 h, 0.5
30 h, 1
10
0
0
24
77
87
47[b]
68[c]
100[d]
57[e]
32
CN (29)
CO2C2H5 (30)
CH3CO (31)
54
[a]
[b]
The reaction temperature was 120 °C.
The first eluted fraction on column separation, blue-green coloured, probably contains 1-
[c]
vinylazulene that polymerises before analysis; tetrahydroquinoline derivative 34 (Scheme 5) was also obtained in moderate yield. (E)
and (Z)-35, (E)-and (Z)-36 also resulted in 12.5% and 6% yield, respectively. Asato[7a] reported the synthesis of compound 37 charac-
[d]
1
[e]
terized by H NMR spectroscopy without a preparation procedure or yield. A mixture of (E) and (Z) isomers was obtained.
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A. C. Razus, C. Nitu, V. Tecuceanu, V. Cimpeanu
FULL PAPER
The elemental analyses and the physical characteristics of com-
pounds 2[N(CH3)2], 2(CN), 9(H), 9(oNO2), 9(pCl), 10Ϫ12, 14, 16,
17, 21(C6H5)Ϫ24, 26, 33, 34, 36 and 38 [(E) and (Z)], 39 and 40
are described in the electronic supplementary information (ESI).
The nomenclature was obtained by use of the ACD/I-Lab Web
service (ACD/IUPAC Name Free 7.06).
tinct protons), the signal multiplicity and the values of the
gem, cis and trans coupling constants.
For the correct geometry assignment of compound 35,
1
we recorded H NMR spectra in the presence of increasing
concentrations of [Eu(fod)3] and we noted the displacement
of the chemical shift belonging to the olefinic protons
towards low field. This attests to the (Z) geometry of hydro- Synthesis of Schiff Bases: All the Schiff bases have been described
by us,[2] except for the compounds 2[N(CH3)2], 2(CN) and 22, syn-
gen and CO2H.
thesized by the known procedure[2] (the results are reported in
Table 5).
Conclusions
Table 5. Schiff base synthesis[2]
M.p.[a] (°C)
This study has two main points of interest. The former
concerns the smooth, efficient and reproducible synthesis
Schiff base
Yield (%)
of 2-substituted 1-(azulen-1-yl)ethenes. Condensations be- 2[N(CH3)2]
85Ϫ87
129Ϫ130
125Ϫ127
100
83
78
2(CN)
tween the Schiff bases and the methylenic compounds were
22
accomplished without catalyst or solvent; this means sim-
plicity in process and handling, reduced pollution and lower
[a]
From ethanol and after good drying on P2O5.
costs. The lack of any requirement for a catalyst, the high
or almost quantitative conversion of starting reagents and
the good product yields allow a very simple workup of the
reaction mixture with the separation of the pure products.
The generality of the proposed syntheses, enabling access
General Procedure for Condensation of Schiff Bases and Arylacetic
Acids: A mixture of equimolar amounts of the arylacetic acid and
the Schiff base, in a flask protected against air humidity, was heated
at 120 °C (oil bath temperature), for the time indicated in Table 2
to various interesting azulene compounds, represents the se- and 3. In all cases, the arylacetic acid dissolved in the melted Schiff
base, although at the end of the reaction time most of the reaction
mixture became solid. After cooling, the resulting amine, con-
densed on the top wall of the flask, was carefully recovered by
washing with DCM. The reaction mixture was then dissolved in
DCM. Before the workup, the mixture was analysed by TLC and
if the degree of conversion was low, the organic solution was
washed with a 5 % cold solution of NaOH, then with ice water,
and dried (Na2SO4). The mixture of compounds was separated by
column chromatography on silica gel or alumina. All fractions were
filtered, and the solvents were evaporated at reduced pressure. In
cond point of interest. Thus, a very large range of substitu-
ents (such as benzenoid aryls, non-benzenoid aryls, het-
eroaryls and other similar groups) can be attached to the
double bond of vinylazulene. Investigations into the hyper-
polarizabilities of these compounds and into their electro-
chemical properties are in progress. The procedure also al-
lows the synthesis of derivatives with two or more double
bonds in the molecule in alternation with azulene and/or
aryl moieties, with the potential for use in other syntheses.
The obtained hydrocarbons can subsequently be activated almost all cases the first fraction was the generated alkene, followed
by the starting Schiff base and some amide obtained from the elim-
inated amine and the arylacetic acid. A small amount of aldehyde
and amine corresponding to the Schiff base may be formed during
chromatography. The degree of conversion of the starting material
was calculated from the integrals of the characteristic proton sig-
nals (with the same multiplicity, mainly singlets) in the 1H NMR
spectra of the fractions collected after the alkene. The yields are
reported to the reacted Schiff base. Tables 1Ϫ3 report both the de-
grees of conversion of the starting materials and the product yields.
For analytical purposes the products were additionally separated
by column chromatography and washed with boiling hexane.
by substitution (e.g., Vilsmeier carbonylation) and the ob-
tained compounds can be used as synthons in other reac-
tions. Research in this area is in progress and the results
will be reported. 3-Azulenylacrylic acid and its derivatives
are also obtained in good yields by the proposed synthetic
method.
Experimental Section
Melting points: Kofler apparatus (Reichert, Austria). Elemental
analyses: PerkinϪElmer CHN 240B. 1H and 13C NMR: Bruker
ARX 500 (1H: 500 MHz, 13C: 125.75 MHz), Bruker Avance DRX4
(1H: 400 MHz, 13C: 100.62 MHz) Bruker WM 300, AC 300 and
Gemini 300 (1H: 300 MHz, 13C: 75.47 MHz), J values are given in
Hz, TMS was used as internal standard in CDCl3 or [D6]DMSO as
solvent; signals were assigned on the basis of COSY and HETCOR
correlation spectra (the numbering for the compounds is indicated
in the Schemes). Mass spectra: Finnigan MAT 311-A/100MS or
Carlo Erba QMD 1000 (EIϩ, 70 eV); for compounds of low vola-
tility the MS were recorded in the solid state. Column chromatogra-
phy: basic alumina [activity BII-III (Brockmann)] or silica gel
The particular reaction conditions or separation procedures are
discussed below for each alkene. A typical example for the proper-
ties of the obtained alkenes is described for 9(p-NO2).
1-[(E)-2-Phenylvinyl]azulene [9(H)]: The reaction mixture was sepa-
rated on silica gel. The first fraction, compound 9(H), was eluted
with benzene and the second with DCM/ethyl acetate (1:1). The
second fraction contained a mixture of Schiff base, p-anisyl-phenyl-
acetamide and p-anisidine, molar ratio 3.4:3.7:1.0. A very small
amount (under 1 %) of the dimer 15 was always eluted, after the
alkene [the amount of the 15 increased with increasing of the excess
of 3(H)].
[70Ϫ230 mesh (ASTM)]. Dichloromethane (DCM) was distilled 1-(1-Azulen-1-yl-2-phenylethyl)-3-[(E)-2-phenylvinyl]azulene
(15):
from over calcium hydride and ethyl acetate over anhydrous so-
dium carbonate.
Green crystals, m.p. 70Ϫ75 °C. C36H28: calcd. C 93.87, H 6.13;
found C 93.79, H 6.15. H NMR (500 MHz, CDCl3, 25 °C): δ ϭ
1
4606
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 4601Ϫ4610

2-Substituted (Azulen-1-yl)ethenes
FULL PAPER
1-[(E)-2-(1-Naphthyl)vinyl]azulene and 1-[(E)-2-(2-naphthyl)vinyl]-
azulene (10α and 10β): The reaction mixture was separated on alu-
2
3
3.66 [dd, JH,H ϭ 14.5, JH,H ϭ 7.5 Hz, 1 H, C(2)-HA], 3.69 [dd,
2JH,H ϭ 14.5, JH,H ϭ 7.5 Hz, 1 H, C(2)-HB], 5.48 [t, JH,H
7.5 Hz, 1 H, C(1)-H], 6.79 [t, JH,H ϭ 10.0 Hz, 1 H, C(7Ј)- or mina with benzene/n-pentane (1:1), and the alkene was eluted as
C(7ЈЈ)-H], 6.90 [t, JH,H ϭ 10.0 Hz, 1 H, C(7Ј)- or C(7ЈЈ)-H], 6.94 the first fraction, followed by unchanged 2(OCH3).
ϭ
3
3
3
3
3
3
[t, JH,H ϭ 10.0 Hz, 1 H, C(5Ј)- or C(5ЈЈ)-H], 6.97 [d, JH,H
ϭ
2-[(E)-2-Azulen-1-ylvinyl]thiophene (11): The reaction mixture was
separated on silica gel with benzene and the alkene was separated
as the first fraction, followed by a fraction containing unchanged
2(OCH3).
7.3 Hz, 2 H, C(2V)-, C(6V)-H], 7.01 [t, 3JH,H ϭ 10.0 Hz, 1 H, C(5Ј)-
or C(5ЈЈ)-H], 7.04Ϫ7.08 [m, 3 H, C(3V)-, C(4V)-, C(5V)-H], 7.12 [d,
3JH,H ϭ 16.0 Hz, 1 H, C(2ЈЈЈ)-H], 7.20 [t, JH,H ϭ 7.4 Hz, 1 H,
3
C(4IV)-H], 7.33Ϫ7.37 [m, 4 H, C(3Ј)-, C(6Ј or 6ЈЈ)-, C(3IV)-, C(5IV)-
3
4-[(E)-2-Azulen-1-ylvinyl]pyridine (12): The mixture of Schiff base
and 4-pyridylacetic acid hydrochloride was heated for 1 h at 100
°C. The solution in DCM was washed with a solution of NaOH (2
) to obtain the free base. The mixture was separated on alumina
with DCM/n-pentane (2:1) and three fractions were collected: frac-
tion 1 contained 4-picoline, resulting from decarboxylation of 4-
pyridylacetic acid, fraction 2 a mixture of unchanged 2(OCH3) and
1-azulenecarboxaldehyde, molar ratio 5.2:1, and fraction 3 the
product 12.
H], 7.43 [t, JH,H ϭ 10.0 Hz, 1 H, C(6Ј)- or C(6ЈЈ)-H], 7.55 [d,
3JH,H ϭ 7.3 Hz, 2 H, C(2IV)-, C(6IV)-H], 7.65 [d, JH,H ϭ 16.0 Hz,
3
3
1 H, C(1ЈЈЈ)-H], 7.92 [d, JH,H ϭ 4.0 Hz, 1 H, C(2Ј)-H], 8.00 [d,
3JH,H ϭ 9.3 Hz, 1 H, C(8Ј)- or C(8ЈЈ)-H], 8.11 [d, JH,H ϭ 9.8 Hz,
3
3
1 H, C(8Ј)- or C(8ЈЈ)-H], 8.22 [d, JH,H ϭ 9.4 Hz, 1 H, C(4Ј)- or
C(4ЈЈ)-H], 8.24 [s, 1 H, C(2ЈЈ)-H], 8.36 [d, JH,H ϭ 10.0 Hz, 1 H,
3
C(4Ј)- or C(4ЈЈ)-H] ppm. 13C NMR (125.75 MHz, CDCl3, 25 °C):
δ ϭ 38.48 (C-1), 44.90 (C-2), 116.94 (C-3Ј), 120.53 (C-1ЈЈЈ), 121.72
(C-7Ј or -7ЈЈ), 122.19 (C-5Ј or -5ЈЈ), 122.31 (C-5Ј or -5ЈЈ), 122.81
(C-7Ј or -7ЈЈ), 125.82 [(C-3V, -5V) or C-4V], 125.88 (q), 125.98 (C-
2IV, -6IV), 126.32 (C-2ЈЈЈ), 126.73 (C-4IV), 128.02 [(C-3V, -5V) or
C-4V], 128.64 (C-3IV,-5IV), 128.96 (C-2V, -6V), 132.24 (C-2ЈЈ), 133.11
(C-8Ј or -8ЈЈ), 133.25 (C-8Ј or -8ЈЈ), 133.34 (q), 133.37 (C-4Ј or
-4ЈЈ), 134.96 (q), 135.00 (q), 135.04 (q), 136.09 (q), 136.16 (C-2Ј),
136.57 (C-4Ј or -4ЈЈ), 137.23 (C-6Ј or -6ЈЈ), 138.12 (C-6Ј or -6ЈЈ),
138.45 (q), 138.46 (q), 140.79 (q) ppm. EI MS: m/z (%) ϭ 460 (2%)
[Mϩ], 369 (25), 269 (2), 268 (33), 267 (100), 266 (12), 265 (33), 252
(17), 230 (27), 202 (6), 189 (2), 152 (6), 97 (8), 69 (10), 57 (17) FD
MS: m/z (%) ϭ 463 (1) [Mϩ ϩ 3], 462 (54) [Mϩ ϩ 2], 461 (38) [Mϩ
ϩ 1], 460 (100) [Mϩ].
1-[(E)-2-Azulen-1-ylvinyl]azulene (13): The reaction mixture was
separated on alumina with DCM/n-pentane (1:5). Alkene 13 (with
the same characteristics as described in the ref.[9b]) was separated
as the first fraction, followed by a fraction containing a mixture of
2(OCH3) and azulenecarbaldehyde.
Condensation between (5-Methoxy-2-methyl-1H-inden-3-yl)acetic
Acid[27] (8) and 2(OCH3): The reaction mixture obtained from 1.5
mmols of reagents was separated after workup on alumina with
benzene/n-pentane (1:1). Three fractions were collected: fraction 1,
1-[(E)-2-(5-methoxy-2-methyl-1H-indene-3-yl)vinyl]azulene
(14,
10 mg, 0.032 mmol, yield 5.6 %), fraction 2, (1Z)-1-(azulen-1-ylme-
thylene)-3-[(E)-2-(azulen-1-yl)vinyl]-2-methyl-1H-inden-5-yl methyl
ether (17, 56 mg, 0.124 mmol, yield 44 %), and fraction 3 (256 mg),
a mixture of unchanged 2(OCH3), 1-azulenecarbaldehyde and p-
anisidine, molar ratio 4.0:1:1.4, conversion of 2(OCH3) 38 %.
1-[(E)-2-(2-Nitrophenyl)vinyl]azulene and 1-[(E)-2-(4-Nitrophenyl)-
vinyl]azulene [9(oNO2) and 9(pNO2)]: The reaction mixture was di-
rectly separated on alumina with DCM/n-pentane (1:2) and the
alkene was eluted as the first fraction, followed by a fraction con-
taining the alkene dimer 16 and finally by a fraction containing
azulenecarbaldehyde from the hydrolysis of the Schiff base
2(OCH3). The generation of dimer for the para-nitro derivative
failed even with an excess of acid.
Condensation between 1,2-Phenylenediacetic Acid and 2(OCH3): A
mixture of Schiff base and 1,2-phenylenediacetic acid
(2 mmol:1 mmol) was heated at 147Ϫ149 °C for 2 h. After workup
the reaction mixture was separated on alumina with n-pentane/ben-
zene (5:1) and three fractions were collected: fraction 1 compound
18 (19 mg, 0.049 mmol, yield 7 %), fraction 2 compound 19 (27 mg,
0.07 mmol, yield 10 %), and fraction 3 unchanged 2(OCH3)
(156 mg, 0.59 mmol, 30 %, eluted with benzene).
1-[(E)-2-(4-Nitrophenyl)vinyl]azulene 9(pNO2): Brown crystals, m.p.
191Ϫ192 °C. C18H13NO2: calcd. C 78.53, H 4.76, N 5.09; found C
78.12, H 4.69, N 5.15. 1H NMR (400 MHz, CDCl3, 25 °C): δ ϭ
3
3
7.18 [t, JH,H ϭ 10.0 Hz, 1 H, C(5Ј)-H], 7.19 [d, JH,H ϭ 16.0 Hz,
1,2-Bis[(E)-2-(azulen-1-yl)vinyl]benzene (18): Green crystals, m.p.
3
1 H, C(2)-H], 7.23 [t, JH,H ϭ 10.0 Hz, 1 H, C(7Ј)-H], 7.43 [d,
195Ϫ197 °C. C30H22: calcd. C 94.20, H 5.80: found C 94.01, H
3JH,H ϭ 4.0 Hz, 1 H, C(3Ј)-H], 7.61 [t, 3JH,H ϭ 10.0 Hz, 1 H, C(6Ј)-
H], 7.65 [d, 3JH,H ϭ 8.9 Hz, 2 H, C(2ЈЈ)-, C(6ЈЈ)-H], 7.87 [d, 3JH,H ϭ
16.0 Hz, 1 H, C(1)-H], 8.21 [d, 3JH,H ϭ 8.9 Hz, 2 H, C(3ЈЈ)-, C(5ЈЈ)-
3
5.82. 1H NMR (500 MHz, CDCl3, 25 °C): δ ϭ 7.07 [t, JH,H
ϭ
10.0 Hz, 4 H, C(5ЈЈ)-, C(7ЈЈ)-H], 7.30 [m, 2 H, C(4)-, C(5)-H], 7.41
3
3
[d, JH,H ϭ 4.1 Hz, 2 H, C(3ЈЈ)-H], 7.51 [t, JH,H ϭ 10.0 Hz, 2 H,
C(6ЈЈ)-H], 7.61 [d, 3JH,H ϭ 16.0 Hz, 2 H, C(1Ј)-H], 7.64 [d, 3JH,H ϭ
16.0 Hz, 2 H, C(2Ј)-H], 7.72 [m, 2 H, C(3)-, C(6)-H], 8.21 [d,
3
3
H], 8.27 [d, JH,H ϭ 4.0 Hz, 1 H, C(2Ј)-H], 8.27 [d, JH,H
ϭ
3
10.0 Hz, 1 H, C(4Ј)-H], 8.53 [d, JH,H ϭ 10.0 Hz, 1 H, C(8Ј)-H]
ppm. 13C NMR (100.62 MHz, CDCl3, 25 °C): δ ϭ 119.71 (C-3Ј),
123.61 (C-7Ј), 123.83 (C-5Ј), 124.24 (C-2), 124.91 (C-3ЈЈ,-5ЈЈ),
125.09 (C-1), 126.02 (C-2ЈЈ, -6ЈЈ), 126.35 (q), 133.59 (C-8Ј), 133.64
(C-2Ј), 136.80 (q), 137.26 (C-4Ј), 138.71 (C-6Ј), 143.69 (q), 145.13
(q), 145.88 (q) ppm. EI MS (in the solid state): m/z (%) ϭ 277 (6)
[Mϩ ϩ 2], 276 (17) [Mϩ ϩ 1], 275 (23) [Mϩ], 274 (13) [Mϩ Ϫ 1],
245 (7), 230 (12), 229 (21), 228 (20), 227 (20), 226 (20), 215 (18.5),
202 (20), 189 (20), 176 (20), 163 (18), 153 (24), 152 (24), 128 (24),
126 (25), 113 (100), 108 (16), 101 (85), 95 (24), 88 (31), 76 (27), 75
(27), 63 (24.5).
3
3JH,H ϭ 9.2 Hz, 2 H, C(4ЈЈ)-H], 8.29 [d, JH,H ϭ 4.2 Hz, 2 H,
C(2ЈЈ)-H], 8.47 [d, 3JH,H ϭ 10.0 Hz, 2 H, C(8ЈЈ)-H] ppm. 13C NMR
(125.75 MHz, CDCl3, 25 °C): δ ϭ 119.02 (C-3ЈЈ), 122.80 (C-5ЈЈ or
-7ЈЈ), 123.17 (C-2Ј), 123.88 (C-5ЈЈ or -7ЈЈ), 93 (C-1Ј), 126.43 (C-3,
-6), 127.06 (C-4, -5), 129.17 (q), 133.64 (C-2ЈЈ), 133.71 (C-8ЈЈ),
136.77 (C-4ЈЈ), 136.90 (q), 137.73 (q), 138.25 (C-6ЈЈ), 144.31 (q)
ppm. EI MS: m/z (%) ϭ 384 (6) [Mϩ ϩ 2], 383 (35) [Mϩ ϩ 1], 382
(100) [Mϩ], 381 (31) [Mϩ Ϫ 1], 365 (17), 352 (10), 339 (6), 303 (7),
289 (14), 267 (59), 265 (27), 254 (87), 253 (75), 252 (65), 239 (39),
228 (33), 215 (10), 202 (6), 191 (14), 176 (10), 165 (7), 152 (16), 141
(92), 130 (30), 115 (20). FD MS: m/z (%) ϭ 383 (32) [Mϩ ϩ 1], 382
(100) [Mϩ], 78 (50), 261 (3).
1-[(E)-2-(4-Chlorophenyl)vinyl]azulene [9(pCl)]: The reaction mix-
ture was separated on silica gel with benzene and the alkene 9(pCl)
was eluted as the first fraction, followed by a fraction containing a 1-[(E)-(2-(Azulen-1-yl)-2,3-dihydro-1H-inden-1-ylidene)methyl]-
mixture of 1-azulenecarbaldehyde and Schiff base. azulene (19): (Structure A Ϫ Scheme 3). Green crystals, m.p.
Eur. J. Org. Chem. 2003, 4601Ϫ4610
www.eurjoc.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4607

A. C. Razus, C. Nitu, V. Tecuceanu, V. Cimpeanu
FULL PAPER
177Ϫ178 °C. C30H22: calcd. C, 94.20, H 5.80; found C 94.10, H
purified. The structure of 23 was assigned on the basis of 1H NMR
and MS data for the fraction 2. The characteristic 1H NMR signals
for aldehyde 24 were obtained from the mixture of 23 and 24 (the
1
3
5.85. H NMR (500 MHz, CDCl3, 25 °C): δ ϭ 3.03 [dd, JH,H
ϭ
3
16.0, 1.8 Hz, 1 H, C(3)-H], 3.75 [dd, JH,H ϭ 16.0, 8.4 Hz, 1 H,
3
C(3)-H], 5.23 [dt, JH,H ϭ 16.0, 1.8 Hz, 1 H, C(2)-H], 6.98 [t, results are reported in the ESI). No starting material was obtained
3JH,H ϭ 10.0 Hz, 1 H, C(5Ј)-H], 6.99 [d, 3JH,H ϭ 4.0 Hz, 1 H, C(3Ј)-
H], 7.07Ϫ7.12 [m, 3 H, C(7ЈЈ)-, C(5ЈЈ)-, C(3ЈЈ)-H], 7.16Ϫ7.21 [m, 3
by chromatographic separation.
3
H, C(4)-, C(5)-, C(7Ј)-H], 7.34 [t, JH,H ϭ 7.6 Hz, 1 H, C(6)-H],
Condensation between N-({3Ј-[(4-Methoxyphenylimino)methyl]-1,1Ј-
biazulen-3-yl}methylene)-4-methoxyaniline and Phenylacetic Acid
[3(H)]: A mixture of the 3,3Ј-bis(Schiff base) of 1,1Ј-bis(azulene)[2]
and phenylacetic acid 3(H) (1 mmol:3 mmol) was heated for 4 h at
140 °C and worked up as described. The mixture was separated
on alumina with DCM/n-pentane (1:4) and three fractions were
separated: fraction 1, 3,3Ј-bis[(E)-2-phenylvinyl)-1,1Ј-biazulene (25,
84 mg, 0.18 mmol, yield 19 %), fraction 2, 3Ј-[(E)-2-phenylvinyl]-
1,1Ј-biazulene-3-carbaldehyde (26, 98 mg, 0.26 mmol, yield 28 %),
and fraction 3, containing the starting material with one hydrolysed
azomethine group (22 mg, 0.053 mmol). All attempts to obtain an
analytical sample of compound 26 failed because of contamination
by the half-hydrolysed starting material (1H NMR spectrum of the
compound 26 is reported in ESI).
3
3
7.44 [d, JH,H ϭ 4.0 Hz, 1 H, C(2Ј)-H], 7.51 [t, JH,H ϭ 10.0 Hz, 1
3
H, C(6ЈЈ)-H], 7.61 [d, JH,H ϭ 3.6 Hz, 1 H, C(2ЈЈ)-H], 7.62 [t,
3JH,H ϭ 10.0 Hz, 1 H, C(6Ј)-H], 7.87 (d, 3JH,H ϭ 1.8 Hz, 1 H, Hexo),
3
3
7.91 [d, JH,H ϭ 7.6 Hz, 1 H, C(7)-H], 8.07 [d, JH,H ϭ 9.2 Hz, 1
3
H, C(4Ј)-H], 8.22 [d, JH,H ϭ 9.6 Hz, 1 H, C(4ЈЈ)-H], 8.54 [d,
3JH,H ϭ 10.0 Hz, 1 H, C(8Ј)-H], 8.58 [d, JH,H ϭ 10.0 Hz, 1 H,
3
C(8ЈЈ)-H] ppm. 13C NMR (125.75 MHz, CDCl3, 25 °C): δ ϭ 41.43
(C-2), 42.34 (C-3), 112.94 (CHexo), 116.90 (C-3ЈЈ), 119.01 (C-3Ј),
119.93 (C-7), 121.59 (C-7Ј), 122.27 (C-7ЈЈ or -5ЈЈ), 122.33 (C-7ЈЈ
or -5ЈЈ), 123.38 (C-5Ј), 125.60 (C-4 or -5), 126.10 (q), 126.84 (C-6),
127.71 (C-5 or -4), 133.07 (C-8Ј), 133.51 (C-8ЈЈ), 133.94 (q), 135.40
(q), 136.16 (C-2Ј, -2ЈЈ), 136.20 (C-4ЈЈ), 136.44 (C-4Ј), 136.65 (q),
137.15 (C-6Ј), 137.98 (C-6ЈЈ), 141.85 (q), 141.39 (q), 143.29 (q),
143.65 (q), 143.70 (q) ppm. EI MS: m/z (%) ϭ 384 (7) [Mϩ ϩ 2],
383 (43) [Mϩ ϩ 1], 382 (100) [Mϩ], 381 (17) [Mϩ Ϫ 1], 365 (17),
352 (6), 253 (51), 254 (32), 252 (35), 241 (17), 191 (8), 141 (64), 128
(10). FD MS: m/z (%) ϭ 384 (5) [Mϩ ϩ 2], 383 (24) [Mϩ ϩ 1], 382
(100) [Mϩ].
3,3Ј-Bis[(E)-2-phenylvinyl]-1,1Ј-biazulene (25): Dark yellow crystals,
m.p. 176Ϫ177 °C. (C36H26: calcd. C 94.28, H 5.71; found C 94.18,
1
3
H 5.75). H NMR (400 MHz, CDCl3, 25 °C): δ ϭ 6.99 [t, JH,H ϭ
3
10.0 Hz, 2 H, C(5)-, C(5Ј)-H], 7.10 [t, JH,H ϭ 10.0 Hz, 2 H,
3
C(7)-, C(7Ј)-H], 7.23 [t, JH,H ϭ 7.5 Hz, 2 H, C(4ЈЈЈ)-H], 7.26 [d,
Condensation between 1,4-Phenylenediacetic Acid and 2(OCH3):
The 1,4-phenylenediacetic acid (1 mmol) was added to an excess of
melted 2(OCH3) (2.5 mmol) and the mixture was then maintained
at 120 °C (oil bath) for 10 h. The solubility of the product 20 was
very low, so the resulting mixture was triturated with DCM and
filtered. The solution contained unchanged 2(OCH3); only 0.50
mmols had reacted. The precipitate was dissolved in a large excess
of ethyl acetate and filtered through a pad of alumina. After sol-
vent removal, the product 20 proved to be analytical pure in 91
% yield.
3JH,H ϭ 15.8 Hz, 2 H, C(2ЈЈ)-H], 7.38 [t, JH,H ϭ 7.5 Hz, 4 H,
3
3
C(3ЈЈЈ)-, C(5ЈЈЈ)-H], 7.51 [t, JH,H ϭ 9.8 Hz, 2 H, C(6)-, C(6Ј)-H],
3
3
7.60 [d, JH,H ϭ 7.5 Hz, 4 H, C(2ЈЈЈ)-, C(6ЈЈЈ)-H], 7.78 [d, JH,H
ϭ
16.0 Hz, 2 H, C(1ЈЈ)-H], 8.20 [d, 3JH,H ϭ 9.4 Hz, 2 H, C(4)-, C(4Ј)-
H], 8.39 [s, 2 H, C(2)-, C(2Ј)-H], 8.52 [d, 3JH,H ϭ 9.8 Hz, 2 H, C(8)-,
C(8Ј)-H] ppm. 13C NMR (100.62 MHz, CDCl3, 25 °C): δ ϭ
120.38 (C-1ЈЈ), 122.88 (C-7, -7Ј), 124.02 (C-5, -5Ј), 126.09 (C-2ЈЈЈ,
-6ЈЈЈ), 126.58 (q, C-1, -1Ј), 126.66 (q, C-3, -3Ј), 126.92 (C-2ЈЈ),
126.97 (C-4ЈЈЈ), 128.69 (C-3ЈЈЈ, -5ЈЈЈ), 133.95 (C-8, -8Ј), 134.64 (C-
2, -2Ј), 136.38 (C-4, -4Ј), 136.66 (q, C-8a, -8aЈ), 138.34 (q, C-1ЈЈЈ),
139.06 (C-6, -6Ј), 140.13 (q, C-3a, -3aЈ) ppm.
1,4-Bis[(E)-2-(azulen-1-yl)vinyl]benzene (20): Brown crystals, very
slightly soluble in most solvents. The compound did not melt until
260 °C. (C30H22: calcd. C 94.20, H 5.80; found C 93.89, H 5.90).
Condensation between 1,3-Azulenediacetic Acid and 2(OCH3): The
3
1H NMR (400 MHz, [D6]DMSO, 25 °C): δ ϭ 7.16 [t, JH,H
ϭ
mixture
of
2(OCH3)
and
1,3-azulenediacetic
acid[18]
9.4 Hz, 2 H, C(5ЈЈ)-H], 7.19 [t, 3JH,H ϭ 9.4 Hz, 2 H, C(7ЈЈ)-H], 7.30
(2 mmol:1 mmol) was maintained at 120 °C for 6 h and worked
up as described. The reaction mixture was separated by column
chromatography on silica, eluent DCM/n-pentane (1:1), and the
alkene 21(Az) was separated as the first fraction (275 mg,
3
3
[d, JH,H ϭ 16.0 Hz, 2 H, C(1Ј)-H], 7.48 [d, JH,H ϭ 4.2 Hz, 2 H,
3
C(3ЈЈ)-H], 7.64 [t, JH,H ϭ 10.0 Hz, 2 H, C(6ЈЈ)-H], 7.72 [s, 4 H,
3
C(2)-, C(3)-, C(5)-, C(6)-H], 7.94 [d, JH,H ϭ 16.0 Hz, 1 H, C(2Ј)-
H], 8.30 [d, 3JH,H ϭ 9.4 Hz, 2 H, C(4ЈЈ)-H], 8.38 [d, 3JH,H ϭ 4.4 Hz,
0.636 mmol, yield 48 %), followed by
a fraction (110 mg,
3
2 H, C(2ЈЈ)-H], 8.79 [d, JH,H ϭ 9.6 Hz, 2 H, C(8ЈЈ)-H] ppm. EI
0.705 mmol), eluted with DCM/ethyl acetate (1:1), containing 1-
azulenecarbaldehyde [from hydrolyse of 2(OCH3)], degree of con-
version of starting material, 65 %.
MS (solid state): m/z (%) ϭ 384 (5) [Mϩ ϩ 2], 383 (31) [Mϩ ϩ 1],
382 (53) [Mϩ], 365 (7), 252 (33), 239 (15), 228 (39), 215 (12), 202
(27), 191 (1/2 Mϩ, 100), 183 (45), 176 (36), 153 (57), 152 (50), 141
(42), 128 (40), 115 (26), 102 (13), 77 (13), 63 (6), 49 (19), 39 (10).
1,3-Bis[(E)-2-(azulen-1-yl)vinyl)azulene [21(Az)]: Brown crystals;
the compound did not melt until 260 °C. (C34H24: calcd. C 94.41,
Condensation between N-({3-[(4-Methoxyphenylimino)methyl]azu-
lene-1-yl}methylene)-4-methoxyaniline (22) and Phenylacetic Acid H 5.59; found C 94.52, H 5.41). 1H NMR (500 MHz, CDCl3, 25
[3(H)]: A mixture of 22 and 3(H) (1 mmol:2 mmol) was heated for °C): δ ϭ 6.85Ϫ7.14 [m, 6 H, C(5)-, C(7)-, C(5ЈЈ)-, C(7ЈЈ)-H], 7.38
3
3
6 h at 120 °C and after workup the reaction mixture was separated
on silica with benzene/n-pentane (1:1). Three fractions were col-
lected: fraction 1, 1,3-distyrylazulene, 21(C6H5) (144 mg,
0.432 mmol, yield 43.2 %), fraction 2, the product of reaction only
at one imino group (23, 15 mg, 0.041 mmol), and fraction 3, con-
[t, JH,H ϭ 10.0 Hz, 1 H, C(6)-H], 7.43 [d, JH,H ϭ 4.0 Hz, 2 H,
3
C(3ЈЈ)-H], 7.49 [t, JH,H ϭ 10.0 Hz, 2 H, C(6ЈЈ)-H], 7.70 [2 H, d,
3JH,H ϭ 16.0, C(1Ј)-H], 7.85Ϫ7.89 [2 H, m, C(2Ј)-H], 8.17 [d,
3JH,H ϭ 10.0 Hz, 2 H, C(4ЈЈ)-H], 8.31 [d, JH,H ϭ 10.0 Hz, 2 H,
3
3
C(4)-, C(8)-H], 8.36 [d, JH,H ϭ 4.0 Hz, 2 H, C(2ЈЈ)-H], 8.56 [d,
taining a mixture of 23 and its hydrolysis product, the aldehyde 24, 3JH,H ϭ 10.0 Hz, 2 H, C(8ЈЈ)-H], 8.74 [s, 1 H, C(2)-H] ppm. EI
in a molar ratio 1.85:1 (the ratio between the two compounds was
MS: m/z (%) ϭ 434 (8) [Mϩ ϩ 2], 433 (37) [Mϩ ϩ 1], 432 (100)
calculated from the signal integrals of -CHO and -CHϭN-protons
[Mϩ], 303 (37), 302 (60), 276 (44), 265 (24), 252 (22), 213 (27), 207
in 1H NMR spectrum, 49 mg). The yields of 23 and in 24 were 14 % (45), 200 (36), 165 (28), 153 (52), 152 (92), 151 (53), 141 (90), 139
and 5 %, respectively. The products 23 and 24 were not analytically
(43), 128 (99), 127 (35), 115 (50), 102 (24), 77 (30), 44 (49).
4608
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Eur. J. Org. Chem. 2003, 4601Ϫ4610

2-Substituted (Azulen-1-yl)ethenes
FULL PAPER
Condensation between Acetylacetone (31) and 2(OCH3): The reac-
tion and the workup were performed as for the condensation be-
tween 30 and 2(OCH3). The reaction mixture was separated on
alumina: fraction 1, eluent benzene, a mixture of Schiff base and
the corresponding aldehyde (molar ratio 2:1), and fraction 2, eluent
DCM, alkene 39 and traces of acetylacetone (the separation of a
pure analytical sample of 39 from the mixture failed).
Condensations between Schiff Bases and other Compounds with Ac-
tive Methylene: The molar ratios between the reagents and the reac-
tion conditions are reported in Table 4. The workup and the separ-
ation procedures are discussed for each condensation.
Condensation between Malonic Acid (27) and 2(OCH3): After con-
densation between 1 mmol of each reagent, the resulting para-anisi-
dine was removed as already described and the reaction mixture
was treated with NaOH solution (2 ). The aqueous layer was ex-
tracted with DCM. The solvent was evaporated, and the resulting
mixture contained, together with the product 34, traces of anisi-
dine, unchanged 2(OCH3) and 1-azulenecarbaldehyde.[28] The tetra-
hydroquinoline 34 was separated from the aldehyde by filtration
through an alumina bed (eluent n-pentane/DCM). All attempts to
separate traces of anisidine from the product failed, so the product
was not completely characterised (only mass and NMR spectra
were recorded). After neutralisation with HCl solution (2 ), the
aqueous layer was extracted with DCM (2 ϫ 50 mL), the organic
Condensation between 1-H-Indene (32) and 2(OCH3): The reaction
and the workup were performed as for the condensation between
30 and 2(OCH3). The reaction mixture was separated on silica with
benzene (1:4) and the alkene 40 was separated as the first fraction
followed by a mixture of Schiff base and aldehyde. The compound
40 is stable over time only in solution, so the NMR and mass spec-
tra were recorded for structure assignment.
layer was dried (Na2SO4), and the solvent was removed in vacuo Acknowledgments
to afford pure (E)-3-(azulen-1-yl)acrylic acid (33, 93 mg,
0.47 mmol, yield 47 %).
A. C. R. and C. N. gratefully acknowledge the Alexander von
Humboldt Foundation for their fellowship granted by the Stability
Pact for Southeast Europe, which allowed this work to be ac-
complished. The project was carried out in the working group of
Prof. Klaus Hafner (T. U. Darmstadt, Germany), whom the
authors A. C. R. and C. N. wish to thank for valuable discussions
and helpful suggestions and for partial financial support. The Min-
istry of Education and Research, Romania, provided a part of the
financial support.
Condensation between Cyanoacetic Acid (28) and 2(OCH3): The
workup of the reaction mixture obtained after condensation of
1 mmol of each reagent followed the same procedure as for malonic
condensation. The residue from the organic layer was separated on
silica with DCM/n-pentane (1:2) and two fractions were collected:
fraction 1, (2Z)-3-(azulen-1-yl)acrylonitrile [(Z)-36, 10 mg,
0.06 mmol, yield 6 %] and fraction 2, (E)- 36, (22 mg, 0.12 mmol,
yield 12.5 %). From the aqueous layer, (2E)-3-(azulen-1-yl)-2-cy-
anoacrylic acid (35), was obtained in 68 % yield (152 mg,
0.68 mmol). No starting material was recovered.
[1] [1a]
A. C. Razus, L. Birzan, S. A. Razus, V. Horga, Rev. Roum.
(2E)-3-(Azulen-1-yl)-2-cyanoacrylic Acid (35): Dark red crystals,
m.p. Ͼ 350 °C. (C14H9NO2: calcd. C 75.33, H 4.06, N 6.28; found
C 75.18, H 4.00, N 6.31). 1H NMR (500 MHz, [D6]DMSO, 25 °C):
Chim. 1999, 44, 235Ϫ248. [1b] A. C. Razus, J. Chem. Soc., Per-
kin Trans. 1 2000, 981Ϫ988. [1c] A. C. Razus, L. Birzan, S. Nae,
S. A. Razus, V. Cimpeanu, C. Stanciu, Synth. Commun. 2001,
32, 825Ϫ837.
3
3
δ ϭ 7.70 [d, JH,H ϭ 4.0 Hz, 1 H, C(3Ј)-H], 7.73 [1 H, t, JH,H
ϭ
3
[2]
10.0, C(5Ј)-H], 7.76 [1 H, t, JH,H ϭ 10.0, C(7Ј)-H], 8.10 [1 H, d,
A. C. Razus, C. Nitu, S. Carvaci, L. Birzan, S. A. Razus, M.
3JH,H ϭ 10.0, C(6Ј)-H], 8.72 [d, JH,H ϭ 10.0 Hz, 1 H, C(4Ј)-H],
Pop, L. Tarko, J. Chem. Soc., Perkin Trans. 1 2001, 1227Ϫ1233.
A. C. Razus, L. Birzan, S. Nae, C. Nitu, V. Tecuceanu, V. Cim-
3
[3]
3
8.80 [s, 1 H, C(1)-H], 8.85 [d, JH,H ϭ 4.0 Hz, 1 H, C(2Ј)-H], 9.00
[d, JH,H ϭ 10.0 Hz, 1 H, C(8Ј)-H] ppm. 13H NMR (125.75 MHz,
3
peanu, Arkivoc 2002, 142Ϫ153.
A. C. Razus, L. Birzan, S. Nae, L. Cristian, F. Chiraleu, V.
[4]
[D6]DMSO, 25 °C): δ ϭ 94.32 (q), 118.47 (q), 120.53 (q), 122.14
(t), 128.96 (t), 129.69 (t), 135.29 (t), 135.57 (t), 139.54 (t), 141.22
(t), 142.58 (q), 143.39 (t), 145.27 (q), 165.00 (q) ppm. EI MS: m/z
(%) ϭ 224 (11) [Mϩ ϩ 1], 223 (100) [Mϩ], 222 (5) [Mϩ Ϫ 1], 206
(4), 179 (15), 178 (25), 177 (20), 151 (20), 150 (15), 126 (3), 108 (2),
89 (1), 76 (5), 63 (4). FD MS: m/z (%) ϭ 226 (2) [Mϩ ϩ 3], 225 (4)
[Mϩ ϩ 2], 224 (18) [Mϩ ϩ 1], 223 (100) [Mϩ], 113 (4).
Cimpeanu, Dyes Pigm. 2003, 57, 223Ϫ233.
P. G. Lacroix, I. Malfant, G. Iftime, A. C. Razus, K. Nakatani,
[5]
J. A. Delaire, Chem. Eur. J. 2000, 6, 2599Ϫ2608.
N. D. Totir, A. C. Razus, C. Lete, C. Nitu, S. Lupu, 81st
[6]
Bunsen-Kolloquium, Dresden (Germany), September 2002.
[7]
[7a] A. E. Asato, R. S. H. Liu, V. P. Rao, Y. M. Cai, Tetrahedron
[7b]
Lett. 1996, 37, 419Ϫ422.
P. Wang, P. Zhu, C. Ye, A. E.
[7c]
Asato, R. S. H. Liu, J. Phys. Chem. 1999, 103, 7076Ϫ7082.
R. Herrmann, B. Pedersen, G. Wagner, J.-H. Youn, J. Or-
ganomet. Chem. 1998, 571, 261Ϫ266.
roix, K. Nakatani, A. C. Razus, Tetrahedron Lett. 1998, 39,
Condensation between Malononitrile (29) and 2(OCH3): The ob-
tained reaction mixture was triturated with a small amount of
warm n-pentane and after drying in vacuo, pure (azulen-1-ylmethy-
lene)malononitrile (37[7a]) was obtained in 100 % yield. No starting
material was recovered.
[7d]
G. Iftime, P. G. Lac-
6853Ϫ6856.
[8]
A short review of the syntheses of different vinylazulenes was
presented by: K.-P. Zeller, in Methoden der Organischen Chemie
(Houben-Weyl), B. V/2c, Georg Thieme Verlag, Stuttgart, New
York, 1985.
Condensation between Ethyl Acetoacetate (30) and 2(OCH3): The
reagents were allowed to react in a flask under a reflux condenser,
under inert atmosphere. At the end, the resulting para-anisidine
and a quantity of unchanged ethyl acetoacetate were removed from
the top wall of the flask. The reaction mixture was separated on
silica with ethyl acetate/n-pentane (1:4) and the ethyl 2-acetyl-3-
(azulen-1-yl)acrylate [38, a mixture of (E) and (Z) isomers with
unassigned structures, in molar ratio 3.6:1] was separated as the
first fraction (115 mg, 0.429 mmol, yield 57 %), followed by a frac-
tion of 105 mg, containing a mixture of 30 and 1-azulenecarbal-
dehyde, molar ratio 2:1.
[9] [9a]
R. N. McDonald, W. S. Stewart, J. Org. Chem. 1965, 30,
[9b]
270Ϫ273.
1905Ϫ1935.
Chem. Soc. Jpn. 1988, 61, 155Ϫ163.
LaBar, R. D. Breazeale, A. G. Anderson, Org. Prep. & Proced.
1976, 8, 169Ϫ177.
Lett. 1974, 289Ϫ292.
Chem. Soc. Jpn. 1980, 53, 3276Ϫ3278.
S. Hunig, B. Ort, Liebigs Ann. Chem. 1984,
[9c]
K. Hafner, G. L. Knaup, H. J. Lindner, Bull.
[9d]
J. O. Currie, R. A.
[9e]
M. Saito, T. Morita, K. Takase, Chem.
M. Saito, T. Morita, K. Takase, Bull.
[9f]
[10]
For the synthesis of 1-(azulen-1-yl)-2-phenylethene [9(H)] we
applied a Wittig procedure in the presence of n-butyllithium
Eur. J. Org. Chem. 2003, 4601Ϫ4610
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 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4609

A. C. Razus, C. Nitu, V. Tecuceanu, V. Cimpeanu
FULL PAPER
[18]
[19]
[20]
This resulted in, together with unchanged 1-azulenecarbal-
dehyde (20 %), a mixture of (Z)- and (E)-9(H) (in yields of 44.5
% and 7.5 %, respectively).
V. A. Nefedov, L. K. Tarygina, Zh. Org. Khim. 1994, 30,
1639Ϫ1643.
V. M. Rodionov, E. V. Yavorskaya, Zh. Obschei. Khim. 1953,
23, 983Ϫ986; Zh. Obschei. Khim. 1955, 25, 2147Ϫ2150.
R. G. Pearson, R. L. Dillon, J. Am. Chem. Soc. 1953, 75,
2439Ϫ2443.
[11]
A. E. Siegrist, Helv. Chim. Acta 1967, 50, 907Ϫ957; A. E. Si-
egrist, H. R. Meyer, Helv. Chim. Acta 1969, 52, 1282Ϫ1323; A.
E. Siegrist, P. Liechti, H. R. Meyer, K. Weber, Helv. Chim. Acta
1969, 52, 2521Ϫ2553; A. E. Siegrist, Helv. Chim. Acta 1981,
64, 662Ϫ685.
[21]
[22]
[23]
S. Patay, J. Zabicky, J. Chem. Soc. 1960, 2030Ϫ2038.
K. Tanaka, F. Toda, Chem. Rev. 2000, 100, 1025Ϫ1074.
[12]
H. Horino, T. Asao, N. Inoue, Bull. Chem. Soc. Jpn. 1991,
64, 183Ϫ190.
G. Charles, Bull. Soc. Chim. France 1963, 1559Ϫ1565;
1566Ϫ1572; 1573Ϫ1578; 1578Ϫ1583.
K. Harada, in The Chemistry of CϭN bond (Ed.: S. Patay),
Interscience Publisher Wiley & Sons, London, New York, Sid-
Of the previously reported alkenes Ϫ
9(H),[9a] 13,[9b]
21(C6H5),[9d] and 37[7a] Ϫ only 13 was completely charac-
terized.
[13]
[24]
[25]
The UV/Vis spectra will be reported and commented on in
another paper in preparation.
In Exp. Sect. we report the NMR spectra only for the com-
pound 9(p-NO2); other spectra are reported in the electronic
Supporting Information; for details see also the footnote on
the first page of this article.
[14]
ney, 1970, p. 262 and following.
[15]
T. I. Bieber, R. Sites, Y. Chiang, J. Org. Chem. 1958, 23,
300Ϫ301.
[16]
[26]
For synthetic purposes, of the two Schiff bases with the highest
reactivity, we preferred 2(OCH3) obtained from para-anisidine,
an amine that is more stable and less harmful.
The diethene 18 and the compound 19 have the same molecular
ion signal in their mass spectra.
[27]
[28]
Compound 8 was a gift from Prof. Klaus Hafner.
[17]
1
An alternative synthesis of the compound 18 was performed
The ratio of these components, established from the H NMR
by the authors by use of a Wittig reaction between ortho-phen-
ylenediylide and two equivalents of azulenecarbaldehyde. A
complex mixture of trans-trans, cis-cis and cis-trans isomers of
18, together with internal cyclization compounds, was ob-
tained. The results will be published.
spectrum of the mixture, showed that about 10 % of 2(OCH3)
remained unchanged and the compound 34 was produced in
about 20 % yield.
Received June 10, 2003
4610
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Eur. J. Org. Chem. 2003, 4601Ϫ4610