Pyranylium Salts as Synthones in the Synthesis of Substituted Benzenes

Article abstract of DOI:10.1080/00397910902737130

Starting from 4-(azulen-1-yl)-pyranylium perchlorates, several azulenyl-substituted phenols as well as nitrobenzene and acetophenone derivatives were synthesized. The products were characterized, and the correlations between the compound structures and NM

Full text of DOI:10.1080/00397910902737130

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Pyranylium Salts as Synthones
in the Synthesis of Substituted
Benzenes
Alexandru C. Razus a , Simona Nica a & Eugenia
Andreea Dragu a
a Romanian Academy , Institute of Organic
Chemistry , Bucharest, Romania
Published online: 03 Aug 2009.
To cite this article: Alexandru C. Razus , Simona Nica & Eugenia Andreea Dragu
(2009) Pyranylium Salts as Synthones in the Synthesis of Substituted Benzenes,
Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 39:17, 3166-3183, DOI: 10.1080/00397910902737130
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Synthetic Communications1, 39: 3166–3183, 2009
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910902737130
Pyranylium Salts as Synthones in the
Synthesis of Substituted Benzenes
Alexandru C. Razus, Simona Nica, and Eugenia Andreea Dragu
Romanian Academy, Institute of Organic Chemistry, Bucharest, Romania
Abstract: Starting from 4-(azulen-1-yl)-pyranylium perchlorates, several azulenyl-
substituted phenols as well as nitrobenzene and acetophenone derivatives were
synthesized. The products were characterized, and the correlations between the
compound structures and NMR spectra were investigated.
Keywords: Acetophenone, azulene-1-yl-benzene, nitrobenzenes, phenols
INTRODUCTION
Recently, p-conjugated aromatic molecules have attracted much attention
as a result of their numerous applications in material science[1] for optical
data storage and optical switching and in biological fields as imaging
fluorescence agents.[2] Among the variety of molecules studied, azulene-
containing compounds have emerged as promising candidates for
constructing nonlinear optical materials.[3] Azulene is a stable nonalternant
aromatic hydrocarbon, which can serve either as electron donor or electron
acceptor depending on the nature of the substituent and the substituted
position.
In the course of our pursuit of novel azulene-based nonlinear optical
materials, we have started to study the azulene-substituted pyranylium
salts.[4] Pyranylium salts represent a nodal point for many synthetic
routes, functioning as versatile synthones for a large variety of organic
Received November 19, 2008.
Address correspondence to Alexandru C. Razus, Romanian Academy,
Institute of Organic Chemistry, Spl. Independentei, 202B, 060023 Bucharest,
35, P. O. Box 108, Romania. E-mail: acrazus@cco.ro
3166

Synthesis of Azulenyl-benzenes
3167
compounds.[5] On the other hand, pyranylium salts themselves are known
to possess interesting technical properties.[6] Hence, their association with
an azulene moiety may lead to organic molecules that possess valuable
properties. In this framework, we focused our attention on studying
the synthesis and the reactivity of azulene-substituted pyranylium salts.
Several syntheses starting from pyranylium salts have already been
accomplished and are described in Scheme 1 (routes a and b).[7]
An important target of our study regarding the use of pyranylium
salts as building blocks was the synthesis of azulene-substituted benzenes,
which are also important because of their technical properties.[8] The C–C
bond formation between azulene and phenyl was first reported by
Arnolds and Pahls and involved radical reaction of N-nitroso-acetanilide
Scheme 1. 4-Azulenylpyranylium salts as synthones for Az-Ar compounds
generation.

3168
A. C. Razus, S. Nica, and E. A. Dragu
with azulene (with 15% yield).[9] 1-Arylazulenes were also obtained with
good conversions and yields through photoarylation of azulene with aryl
iodides.[10] The metal-catalyzed coupling reaction is particularly suitable
for the C–C bond formation between two aryl moieties. Thus, when
palladium-catalyzed Suzuki reaction was performed using 1-azulene
triflate and aryl halides, arylazulenes were obtain with around 5%
yield.[11] Nevertheless, the 1-azulene triflate is unstable and decomposes
in the appropriate solvents for palladium-catalyzed reactions. An inter-
molecular palladium acetate–catalyzed arylation of the unfunctionalized
azulene with benzene was accomplished by Dyker and coworkers.[12]
After 3 days at 100ꢀC in the presence of Bu4NBr, the yield of 1-phenyla-
zulene was 13%. Further improvement of the reaction yields has been
achieved by using azulen-1-yl boronate as starting material in an
asymmetric Miyaura–Suzuki reaction using Pd(0) as catalysts.[13]
However, the metal-catalyzed coupling reaction is limited by the use of
substituted aromatic halides, which sometimes require excess synthetic
strategies and costly catalysts. Moreover, this reaction is not suitable
for all functionalized aromatic derivatives. The synthetic pathway
proposed herein for 1-arylazulenes starts from azulene-substituted pyra-
nylium salts with common reactants and mild conditions. The developed
synthesis was directed mainly for the preparation of azulenyl-substituted
phenols and nitrobenzene derivatives (routes c and d in Scheme 1) and
with rather modest yields for acetophenone 5 (route e). The attempts to
obtain azulene-substituted benzonitriles starting from acetonitrile failed.
The use of ethyl cyanoacetate might be a solution for their generation.
RESULTS AND DISCUSSION
Synthesis of Benzenes Substituted with Azulene-1-yl Moiety
Synthesis of Phenols
Conversion of azulene-substituted pyranylium salts to phenol derivatives
starts from (azulen-1-yl)-2,6-dimethylpyranylium perchlorate, 1, R¼Me,
and occurs in aqueous ethanol solution in the presence of sodium
hydroxide at reflux (route c in Scheme 1). The reaction takes place by
incorporating one carbon atom of the 2(6)-methyl group via intramole-
cular condensation of an intermediate pseudobase.[15] The pseudobase
is formed as a consequence of the nucleophilic attack of the OH– anion
on the a-position of pyranylium oxygen followed by ring opening.
The reaction yield is strongly influenced by the experimental
conditions. The solubility of the pyranylium salt, 1, is the determining

Synthesis of Azulenyl-benzenes
3169
factor for the reaction yield. By performing the reaction with a suspen-
sion of pyranylium salt 1a, the corresponding 3-(azulen-1-yl)-5-
methyl-phenol, 2a, was obtained only in 5% yield. Instead, the complete
dissolution of the pyranylium salt increased the yield in phenol to about
39% when an excess of 5 equivalents of sodium hydroxide was used. The
amount of sodium hydroxide also played a very important role for the
final yield of the reaction. Thus, an excess of 7 equivalents reported to
the pyranylium salt proved to be the ideal amount (exp. 4 in Table 1),
whereas a larger excess (11 equivalents) leads to a severe decrease of
the reaction yield. At the same time, with the greater excess of sodium
hydroxide, a large number of unidentified compounds are formed.
With these optimum reaction conditions (exp. 4 in Table 1),
azulene-substituted phenols have been obtained. As was expected, the
influence of the azulenyl moiety substituents upon reaction yields is
obvious. For instance, the alkylated azulenyl from the 4-position in
the pyranylium salts favors the generation of the corresponding phenols
(Table 2). The possible explanation consists in the decrease in stabiliza-
tion of the starting pyranylium salts because of the deviation from
coplanarity of azulene and pyranylium moieties caused by the steric
requirement of the bulky alkyl groups. Thus, the presence of tert-butyl
in 2-position of the azulenyl group leads to the formation of the corre-
sponding phenol 2d in about 90% yield. Here, it is worth mentioning
that unsubstitued azulene ring was reported to be unstable in very
strong basic media[14] and this fact is reflected in the moderate yield
in phenol 2a.
It is interesting that the influence of the substituent from the
3-position of the azulenyl moiety is small. The presence of the
electron-donating group –NHCOCH3, 1e, as well as the electron-
withdrawing substituent –CO2Et, 1f, diminishes the yields of 2e and
2f, respectively.
Table 1. Influence of the experimental conditions on
the reaction of 4-(azulen-1-yl)-2,6-dimethyl-pyranylium
perchlorate, 1a, in the presence of NaOH
Starting
compound
Ethanol
(ml)
NaOH
(mmol)
Yield in
2 (%)
Exp.
1
2
3
4
5
1a (1 mmol)
7
14
30
43
43
5
5
5
7
12
5
12
39
55
34

3170
A. C. Razus, S. Nica, and E. A. Dragu
Table 2. Influence of the azulenyl substituents on
reaction c of pyranylium perchlorate, 1 (reaction
conditions used according to Table 1, exp. 4)
Reactions
Yield (%)
1a ! 2a
1b ! 2b
1c ! 2c
1d ! 2d
1e ! 2e
1f ! 2f
55
70
75
90
40
36
Synthesis of Nitrobenzene Derivatives
Another preparative conversion of the azulene-substituted pyranylium
perchlorates 1, namely to nitro-substituted benzenes, has also been
developed. Thus, otherwise difficult accessible azulene-substituted nitro-
benzenes could be easily generated. In this case, the pyranylium salt was
reacted with nitromethane in the presence of potassium tert-butoxide (3
equivalents), yielding the 2,6-disubstituted-4-(azulen-1-yl)-nitrobenzenes
3 or 4. The reaction took place by loss of one proton of the nitro-
methane followed by the attack of the generated carbanion on the
2(6) position of pyranylium salt. After the heterocyclic opening, the
methylene bound to nitro group was incorporated in the new aromatic
ring with the formation of nitrobenzene derivatives.[5] Contrary to the
synthesis of azulenyl-phenols, in the case of nitro-substituted benzenes,
2,6-diphenyl-4-(azulen-1-yl)-pyranylium perchlorates could be also used
as starting materials besides the corresponding 2,6-dimethyl compounds.
The reaction yields vary from satisfactory to very good, being greater
when 2,6-diphenyl-4-(azulen-1-yl)-pyranylium perchlorate has been
reacted with nitromethane (Table 3) despite the longer reaction time
needed for the reaction. In this case, the stabilizing effect of the two
phenyl groups on the obtained benzene could be the driving force for
the good yields obtained.
For the reaction with nitromethane, the influence of the azulenyl
substitution is not as evident as for the previously discussed phenol

Synthesis of Azulenyl-benzenes
3171
Table 3. Reaction of pyranylium salts 1 with nitromethane
(reaction d) in the presence of tBuOK and n-BuLi
Compound
3aa 3ba 3ca 3da 3fa 4ab 4bb
Yield (%) in tBuOK 52
Yield (%) in n-BuLi 41
53 43
42 33
83 37
56
87
—
89
—
—
aReaction time 2 h.
bReaction time 18 h.
synthesis. However, the presence of a tert-butyl group in the 2-position of
the azulenyl moiety enhanced the yield of compound 3d. However, when
the azulenyl moiety was substituted in the 3-position with CO2Et, the
yield of compound 3f decreased.
Replacement of potassium tert-butoxide with a stronger base such as
n-BuLi did not lead to an improvement of the reaction yield (Table 3).
The nitrobenzene derivatives were obtained in lesser yields because of
degradation of the reaction intermediates, as it has been observed by,
thin-layer chromotography (TLC) monitoring of the reaction.
Acetophenone Derivative Synthesis
The versatility of the pyranylium salts 1 to function as synthones in
organic synthesis was proven by isolation of 2,6-disubstituted-4-
(azulen-1-yl)-acetophenone derivatives 5 when these salts were reacted
with acetylacetone. The reaction occured in the presence of an excess
of potassium tert-butoxide.[15] Because the 2,6-diphenyl substitution of
the starting pyranilium salt was proven to have a favorable effect on the
reaction yield as has been described for nitrobenzene derivatives, the
reaction was performed for isolation of azulenyl-acetophenone 5 in
51% yield. Further investigations on the reaction mechanism as well
as the influence of the azulenyl-substitution are under way in our
laboratories.

3172
A. C. Razus, S. Nica, and E. A. Dragu
NMR and Electronic Spectra
During our early investigations, we outlined the interdependence between
structure and NMR or electronic spectra for several (azulene-1-yl)-aryl or
heteroaryl compounds. Two main factors are determinant for the
chemical shifts of the protons, namely the electron-donating effect of
the azulene-1-yl group and the change in anisotropy of the magnetic field
with the variation of the dihedral angle formed by the two coupled
moieties. The first factor is important for the azulenyl-heteroaryl mole-
cules with an electron acceptor heteroatom as the pyranylium salt 1a.
The coplanarity of the coupled moieties allows the electron transfer from
azulenyl to heterocycle. The loss in electron density results in the strong
deshielding of azulenyl protons as compared to the parent azulene
(Table 4). For such compounds, the deviation from coplanarity causes
a decrease in proton deshielding. This decrease is also accentuated by
the inductive effect exerted by the alkyl substituents to the azulenyl
moiety. The tendency of the phenyl group to polarize is very low. There-
fore the substitution of 1-position of azulene with phenyl occurs without
a dramatic change in the shift of the azulenic protons (Table 4).[4a] As
expected, the presence of the hydroxyl group in the 3-position of the
phenyl has no influence on the azulenyl protons as can be observed by
comparison of the proton shifts of 1-phenylazulene with the chemical
shifts of compound 2a. Some tendency for shielding of these protons
can be observed for the alkylated azulene, despite some increase of the
dihedral angle formed by the coupled moieties by this substitution.
We have expected that when the 4-position of the phenyl moiety is
occupied by NO2 or COCH3, which are good electron-acceptor groups,
as in compounds 3–5, a greater polarization of the molecule takes place
with consequences in the azulenyl protons shifts. However, very similar
values for the proton shifts of 1-phenylazulene and for these compounds
Table 4. Chemical shifts for azulenyl protons in compounds 2 and 3
Compound
H-20 H-30
H-40 H-50
H-60 H-70
H-80 H-3(5)
AzH
1a (R ¼ Me)[6]
7.81 7.30
8.55 7.78
8.02 7.43
7.99 7.41
8.23 7.05
8.86 7.88
8.34 7.14
8.33 7.15
8.38 7.21
8.41 7.24
8.36 7.18
7.45 7.05
8.20 7.93
7.58 7.14
7.58 7.15
7.64 7.21
7.60 7.24
7.61 7.18
8.23
9.03
8.55
8.57
8.52
8.60
8.62
—
—
—
—
7.34
7.62
7.63
PhAz[4a]
2a
3a
4a
5
7.97 7.43
a
8.07
8.08
—
—
a
aThe signal is included in a multiplet.

Synthesis of Azulenyl-benzenes
3173
Scheme 2. Donor (azulenyl)-p spacer-acceptor structures.
can be observed. That means that structures 3 (II) or 5 (II) in Scheme 2
contribute to a small extent to the real electron density in the ground state
of the molecule. The possible explanation for the reduced contribution of
these structures consists in the difficulty of nitro or acetyl group to
adopt a coplanar structure with the rest of the molecule because of the
neighboring groups situated in 2 and 6 positions.
The shift of the two phenyl protons that are near the azulene moiety
in both compound series is not influenced by the azulenyl substitution.
However, the replacement of methyl groups in 2 and 6 positions by
phenyls cause a deshielding of these protons.
The low tendency toward molecular polarization is also in agreement
with the small differences observed between the absorption maxima of
the low-energy charge-transfer transitions for the studied compounds.
As expected, a small bathochromism took place in compound series
2, 3, 4, and 5.
Studies to extend the use of pyranylium salts as starting compounds
for generating other azulenyl-substituted benzenes are in progress in our
laboratory.
EXPERIMENTAL
General Procedures
Melting points were measured on a Kofler apparatus (Reichert Austria).
Elemental analyses used a Perkin-Elmer CHN 240B. Ultraviolet (UV)=Vis
spectra were recorded in methanol and dichloromethane (DCM) using a
Varian Cary 100 Bio spectrophotometer. 1H and 13C NMR spectra were
recorded on Gemini 300 (1H NMR: 300 MHz; 13C NMR: 75.45 MHz),
Bruker Avance DRX4 (1H NMR: 400 MHz; 13C NMR: 100.62 MHz),

3174
A. C. Razus, S. Nica, and E. A. Dragu
and Bruker ARX 500 (1H NMR: 500MHz; 13C NMR: 127.75MHz)
instruments; d are expressed in parts per million (ppm) and J in hertz. Tetra-
methylsilane (TMS) was used as internal standard in CDCl3 at room tem-
1
1
perature; H-1H and H-13C COSY correlation spectroscopy experiments
were used for the structure assignment. Mass spectra (MS) were recorded
on a Varian 1200 L Quadrupole=MS=MS spectrometer using direct injection
in electrospray ionization (ESI) or atmospheric pressure chemical ionization
(APCI) mode. Infrared (IR) spectrum was recorded on a Bruker Vertex 70
instrument. Column chromatography used alumina [activity BII–III (Brock-
mann)] and silica gel [70–230 mesh (ASTM)]. DCM was distilled over CaH2,
and ethyl acetate was distilled over anhydrous sodium carbonate. Pyrany-
lium perchlorates are obtained as described in the literature.[4]
General Procedure for the Synthesis of Compounds 2
A solution of NaOH (196 mg, 4.9 mmol) in 20 mL of H2O was added to a
solution of pyranylium perchlorate 1 (0.7 mmol) in ethanol (the amount
of ethanol used for the salt dissolution is shown in Table 1). The resulting
mixture was stirred under reflux for a period of 2 h. After cooling at room
temperature, concentrated HCl was added for neutralization, followed by
extraction of the mixture with DCM (3 ꢁ 50 mL) for 2a, 2b, 2c, and 2d
and AcOEt (3 ꢁ 25 mL) for 2e and 2f. The combined organic phases were
washed with water and dried over anhydrous Na2SO4, and the solvent
was removed under reduced pressure. The crude product was purified
by column chromatography on the supports and elution mixture
indicated in Table 5. After the first fraction containing unidentified
compounds, the desired phenol was eluted.
General Procedure for the Synthesis of Compounds 3 and 4
by Reaction of the Pyranylium Perchlorates with Nitromethane
In the Presence of Potassium tert-Butoxide
Under an inert atmosphere (N2), a solution of potassium tert-butoxide
(157 mg, 1.4 mmol) in tert-butyl alcohol (2.5 mL) was added to a solution
of pyranylium perchlorate 1 (0.7 mmol) in nitromethane (the amount of
nitromethane used for the salt dissolution is shown in Table 6), and the
resulting mixture was stirred under reflux for 1 h. An additional quantity
of potassium tert-butoxide (78 mg, 0.7 mmol) in tert-butyl alcohol (1 g)
was than used, and the stirring and reflux were continued for the time
reported in Table 6. After cooling to room temperature, the reaction

Synthesis of Azulenyl-benzenes
3175
Table 5. Amount of ethanol used as solvent in the reactions and the conditions
for products separation
EtOH
used in
Conditions for columns chromatography
Elution mixture
Obtained
compound reaction (mL)a Support
2a
2b
2c
2d
2e
2f
30
30
20
30
35
40
Alumina DCM=petroleum ether=EtOH ¼ 2:1:0.2
Alumina DCM=petroleum ether=EtOH ¼ 2:1:0.2
Silica gel DCM=petroleum ether ¼ 2:1
Silica gel DCM=petroleum ether=EtOH ¼ 2:1:0.2
Silica gel AcOEt=cyclohexane ¼ 2:1
Silica gel DCM=petroleum ether ¼ 2:1
aFor 0.7 mmol of reacted salts.
mixture was diluted with water and repeatedly extracted with DCM
(4 ꢁ 50 mL). The combined organic layers were washed with water and
dried over anhydrous Na2SO4, and the solvent was removed under
reduced pressure. The crude product was purified by column chromato-
graphy as indicated in Table 6. After the first fraction containing
unidentified compounds, the desired nitroderivative was eluted.
In the Presence of n-Butyllithium
n-Butyllithium (0.44 mL, 1.4 mmol) was slowly added to 0.5 mL nitro-
methane at 0ꢀC under an inert atmosphere (N2). After 5 min of stirring,
a solution of pyranylium perchlorate (0.7 mmol) in nitromethane was
Table 6. Amount of nitromethane used as solvent in the reactions and the
conditions for product separation
Conditions for column
chromatography
CH3NO2
used in
Obtained
Reaction
compound reaction (mL)a time (h) Support
Elution mixture
3a
3b
3c
3d
3e
4a
4b
4
3
4
3
5
4
4
2
Alumina DCM petroleum ether ¼ 1:5
DCM=petroleum ether ¼ 1:5
DCM=petroleum ether ¼ 1:4
DCM=petroleum ether ¼ 1:5
Silica gel DCM=petroleum ether ¼ 1:7
Alumina DCM=petroleum ether ¼ 1:7
DCM=petroleum ether ¼ 1:7
18
aFor 0.7 mmol reacted salt.

3176
A. C. Razus, S. Nica, and E. A. Dragu
added. The reaction mixture was stirred for 15 min at room temperature
and then refluxed for 2 h. After cooling to room temperature, water
(50 mL) was added, and the formed mixture was worked up as described
previously.
Procedure for the Synthesis of Compound 5
Under an inert atmosphere (N2), a mixture of potassium tert-butoxide
(68 mg, 0.6 mmol), pentane-2,4-dione (80 mg, 0.8 mmol), and tert-butyl
alcohol (5mL) was added to a suspension of pyranylium perchlorate 1
(92 mg, 0.2 mmol) in 5 mL of tert-butyl alcohol, and the resulting mixture
was stirred under reflux for 1.5 h. After cooling to room temperature, the
reaction mixture was diluted with water and repeatedly extracted with
DCM (4ꢁ 50mL). The combined organic layers were washed with water
and dried over anhydrous Na2SO4, and the solvent was removed under
reduced pressure. The resulted crude product was purified by column chro-
matography on silica gel using a mixture of petroleum ether-DCM 2:1.
Data
3-(Azulen-1-yl)-5-methylphenol 2a
Blue oil; UV=VIS (MeOH), kmax (log e): 294 (4.59), 358 (3.81), 600
(broad). 1H NMR (CDCl3, 500 MHz, d ppm): 2.39–2.40 (m, 3H,
5-CH3), 4.73 (s, 1H, OH), 6.64–6.67 (m, 1H, 6-H), 6.88–6.91 (m, 1H,
3
2-H), 7.01–7.03 (m, 1H, 4-H), 7.15 (t, J ¼ 9.7 Hz, 2H, 50-H, 70-H), 7.41
3
3
(dAB, J ¼ 3.9 Hz, 1H, 30-H), 7.58 (t, J ¼ 9.8 Hz, 1H, 60-H), 7.99 (dAB
,
3J ¼ 3.8 Hz, 1H, 20-H), 8.33 (d, J ¼ 9.5 Hz, 1H, 40-H), 8.57 (d,
3J ¼ 9.8 Hz, 1H, 80-H). 13C NMR (CDCl3, 125.7 MHz, d ppm): 21.52
(5-CH3), 113.6 (C2), 114.07 (C6), 117.39 (C30), 123.08 (C4), 123.28 and
123.30 (C50 and C70), 130.93 (Cq), 135.29 (Cq), 135.67 (C80), 137.09
and 137.26 (C20 and C40), 138.18 (C60), 138.97 (Cq), 139.94 (Cq),
141.77 (Cq), 155.64 (C–OH). MS-ESI positive (m=z, %, 20 eV): 235
([M þ 1]þ, 75), 217 ([M þ 1]þ-H2O, 68), 202 ([M þ 1]þ-H2O–CH3, 100).
Anal. calcd. for C17H14O: C, 87.15; H, 6.02. Found: C, 87.22; H, 6.10.
3
3-(4,6,8-Trimethyl-azulen-1-yl)-5-methylphenol 2b
Violet oil; UV=VIS (MeOH), kmax (log e): 97 (4.39), 368 (3.20), 565
1
(broad). H NMR (CDCl3, 400 MHz, d ppm): 2.35 (s, 3H, 5-CH3), 2.50

Synthesis of Azulenyl-benzenes
3177
(s, 3H, 60-CH3), 2.61 (s, 3H, 40-CH3), 2.91 (s, 3H, 80-CH3), 4.90 (bs, 1H,
OH), 6.61–6.64 (m, 1H, 6-H), 6.64–6.67 (m, 1H, 2-H), 6.78–6.80 (m, 1H,
4-H), 6.96 (s, 1H, 50-H or 70-H), 7.05 (s, 1H, 70-H or 50-H), 7.35 (dAB
,
3J ¼ 4.0 Hz, 1H, 30-H), 7.55 (dAB
,
3J ¼ 4.0 Hz, 1H, 20-H). 13C NMR
(CDCl3, 100.57 MHz, d ppm): 21.50 (5-CH3), 25.62 (40-CH3), 28.59
(60-CH3 and 80-CH3), 113.83 (CH), 114.78 (CH), 114.94 (CH), 124.55 (CH),
127.05 (CH), 128.92 (CH), 131.36 (Cq), 132.46 (Cq), 136.21 (CH), 137.24
(Cq), 138.57 (Cq), 143.68 (Cq), 145.86 (Cq), 146.27 (Cq), 147.64 (Cq),
154.71 (C-OH). MS-ESI positive (m=z, %): 277 ([M þ 1]þ, 100). Anal.
calcd. for C20H20O: C, 86.92; H, 7.29. Found: C, 86.88; H, 7.24.
3-(5-Isopropyl-3,8-dimethyl-azulen-1-yl)-5-methylphenol 2c
Blue oil; UV=VIS (MeOH), kmax (log e): 293 (4.59), 369 (3.86), 606
1
(broad). H NMR (CDCl3, 300 MHz, d ppm): 1.37 (d, J ¼ 6.9 Hz, 6H,
CH3-iPr), 2.33 (s, 3H, 5-CH3), 2.45 (s, 3H, 60-CH3), 2.66 (s, 3H,
80-CH3), 3.07 (hept, 3J ¼ 6.9 Hz, 1H, CH-iPr), 4.90 (bs, 1H, OH),
6.60–6.62 (m, 1H, 6-H), 6.63–6.65 (m, 1H, 2-H), 6.76 (bs, 1H, 4-H),
3
3
4
6.89 (dAB, J ¼ 10.7 Hz, 1H, 70-H), 7.36 (dABd, J ¼ 10.7 Hz, J ¼ 2.2 Hz,
Hz, 1H, 60-H), 7.52 (s, 1H, 20-H), 8.19 (d, J ¼ 2.2 Hz, 1H, 40-H). 13C
4
NMR (CDCl3, 75.47 MHz, d ppm): 13.11 (30-CH3), 21.67 (5-CH3),
24.96 (CH3-iPr), 27.69 (80-CH3), 38.17 (CH-iPr), 114.01 (CH), 115.16
(CH), 124.30 (Cq), 124.92 (CH), 127.06 (CH), 129.03 (Cq), 134.00
(CH), 135.12 (CH), 138.59 (Cq), 139.98 (Cq), 140.22 (CH), 143.25
(Cq), 146.37 (Cq), 154.77 (C–OH). MS-ESI positive (m=z, %): 305
([M þ 1]þ, 100). Anal. calcd. for C22H24O: C, 86.80; H, 7.95. Found: C,
86.83; H, 7.98.
3-(2-tert-Butyl-6-methylazulen-1-yl)-5-methyphenol 2d
Violet oil; UV=VIS (MeOH), kmax (log e): 292 (4.66), 353 (3.60), 563
1
(broad). H NMR (CDCl3, 400 MHz, d ppm): 1.38 (s, 9H, CH3-tBu),
2.37 (s, 3H, 5-CH3), 2.59 (s, 3H, 60-CH3), 6.62–6.65 (m, 1H, 6-H),
3
6.70–6.73 (m, 1H, 2-H), 6.77–6.80 (m, 1H, 4-H), 6.90 (dAB, J ¼ 9.8 Hz,
3
Hz, 1H, 50-H), 7.03 (dAB, J ¼ 9.8 Hz, 1H, 70-H), 7.31 (s, 1H, 30-H), 7.62
(dAB
,
3J ¼ 10.2 Hz, 1H, 40-H), 8.13 (dAB
,
3J ¼ 9.9 Hz, 1H, 80-H). 13C
NMR (CDCl3, 100.57 MHz, d ppm): 21.52 (5-CH3), 28.01 (60-CH3),
31.90 (CH3-t-Bu), 34.81 (C-tBu), 113.25 (CH), 114.51 (CH), 114.75
(CH), 124.31 (CH), 125.85 (CH), 129.50 (Cq), 133.72 (CH), 134.52
(CH), 137.43 (Cq), 138.24 (Cq), 138.65 (Cq), 140.98 (Cq), 147.55
(Cq), 154.72 (Cq), 159.49 (C-OH). MS-ESI positive (m=z, %): 305

3178
A. C. Razus, S. Nica, and E. A. Dragu
([M þ 1]þ, 100). Anal. calcd. for C22H24O: C, 86.80; H, 7.95. Found: C,
86.85; H, 8.01.
N-(3-(3-Hydroxy-5-methylphenyl)azulen-1-yl)acetamide 2e
Green oil; UV=VIS (MeOH), kmax (log e): 297 (4.32), 377 (3.61), 613
1
(broad). H NMR (acetone-D6, 400 MHz, d ppm): 2.27 (s, 3H, 5-CH3),
2.37 (s, 3H, COCH3), 6.68–6.73 (m, 1H, 6-H), 6.90–6.95 (m, 2H, 2-H,
3
3
4-H), 6.98 (t, J ¼ 9.7 Hz, 1H, 70-H), 7.03 (t, J ¼ 9.7 Hz, 1H, 50-H),
3
3
7.55 (t, J ¼ 9.9 Hz, 1H, 60-H), 8.40 (d, J ¼ 9.70 Hz, 1H, 40-H), 8.48 (d,
3J ¼ 9.53 Hz, 1H, 80-H), 8.55 (bs, 1H, 20-H). Because of the small amounts
of compounds 2e and 3e obtained, the 13C NMR spectra were not
recorded. MS-ESI positive (m=z, %): 292 ([M þ 1]þ, 100). Anal. calcd.
for C19H17NO2: C, 78.33; H, 5.88, N, 4.81. Found: C, 78.30; H, 5.92,
N, 4.74.
Ethyl 3-(3-Hydroxy-5-methylphenyl)-6-methylazulene-1-carboxylate 2f
Violet oil; UV=VIS (MeOH), kmax (log e): 309 (4.49), 394 (3.77), 551
(2.23). 1H NMR (CDCl3, 400 MHz, d ppm): 1.45 (t, 3J ¼ 7.2 Hz, 3H,
CH3CH2), 2.39 (s, 3H, 5-CH3), 2.65 (s, 3H, 60-CH3), 4.43 (q, 2H,
CH3CH2), 6.71 (bs, 1H, 6-H), 6.87 (bs, 1H, 2-H), 6.95 (bs, 1H, 4-H),
3
3
7.23 (dAB, 1H, J ¼ 10.4 Hz, 50-H) 7.34 (dAB, J ¼ 10.4 Hz, 1H, 70-H),
8.32 (s, 1H, 20-H), 8.48 (dAB
,
3J ¼ 10.3 Hz, 1H, 80-H), 9.47 (dAB
,
3J ¼ 10.4 Hz, 1H, 40-H). 13C NMR (CDCl3, 100.6 MHz, d ppm): 14.73
(CH3CH2), 21.62 (5-CH3), 28.03 (60-CH3), 60.02 (CH2CH3), 113.76,
114.69, 115.86, 123.09, 128.68, 129.28, 130.54, 136.26, 137.33, 138.10,
138.69, 138.87, 140.13, 140.37, 152.07, 156.05 (C-OH), 165.95 (CO).
MS-ESI positive (m=z, %, 20 eV): 321 ([M þ 1]þ, 52), 275 ([M þ 1]þ,
H-EtO, 100). Anal. calcd. for C21H20O3: C, 78.73; H, 6.29. Found: C,
78.68; H, 6.25.
1-(3,5-Dimethyl-4-nitrophenyl)azulene 3a
Green powder, mp 115–116ꢀC; UV=VIS (CH2Cl2), kmax (log e): 237
(4.41), 293 (4.52), 375 (3.96), 585 (broad). H NMR (CDCl3, 300 MHz,
1
3
d ppm): 2.42 (s, 6H, 3-CH3, 5-CH3), 7.21 (t, J ¼ 9.5 Hz, 2H, 50-H,
3
70-H), 7.34 (s, 2H, 2-H, 6-H), 7.43 (dAB, J ¼ 4.0 Hz, 1H, 30-H), 7.64 (t,
3J ¼ 9.8 Hz, 1H, 60-H), 7.97 (dAB
,
3J ¼ 4.0 Hz, 1H, 20-H), 8.38 (d,
3J ¼ 9.7 Hz, 1H, 40-H), 8.52 (d, 3J ¼ 9.8 Hz, 1H, 80-H). 13C NMR (CDCl3,
75.47 MHz, d ppm): 18.1 (CH3), 118.0 (CH), 124.0 (CH), 124.2 (CH),

Synthesis of Azulenyl-benzenes
3179
129.4 (Cq), 130.1 (CH), 130.4 (Cq), 135.6 (CH), 135.9 (Cq), 137.3 (CH),
137.9 (CH), 138.7 (CH), 139.9 (Cq), 142.4 (Cq), 150.4 (C4). MS-APCI
positive (m=z, %): 278 ([M þ 1]þ, 100). Anal. calcd. for C18H15NO2: C,
77.96; H, 5.45; N, 5.05. Found: C, 77.95; H, 5.47; N, 4.93.
1-(3,5-Dimethyl-4-nitrophenyl)-4,6,8-trimethylazulene 3b
Brown-reddish powder, mp 197–198ꢀC; UV=VIS (CH2Cl2), kmax (log e):
247 (4.44), 299 (4.56), 348 (3.90), 378 (3.68), 572 (1.88). 1H NMR (CDCl3,
300 MHz, d ppm): 2.29 (s, 6H, 3-CH3, 5-CH3), 2.40 (s, 3H, 60-CH3), 2.54
(s, 3H, 40-CH3), 2.83 (s, 3H, 80-CH3), 6.93 (s, 1H, 50-H), 7.01 (s, 1H, 70-H),
7.06 (s, 1H, 2-H, 6-H), 7.27 (dAB
,
3J ¼ 4.1 Hz, 1H, 30-H), 7.44 (dAB
,
3J ¼ 4.1 Hz, 1H, 20-H). 13C NMR (CDCl3, 75.47 MHz, d ppm): 17.8
(3-CH3, 5-CH3), 25.6 (40-CH3), 28.6 (60-CH3), 29.2 (80-CH3), 115.1
(Cq), 115.3 (CH), 127.6 (Cq), 127.6 (CH), 128.9 (Cq), 129.3 (CH),
130.2 (CH), 130.9 (Cq), 135.7 (Cq), 136.3 (CH), 136.4 (Cq), 146.3 (Cq),
146.7 (Cq), 147.3 (Cq), 150.1 (C4). MS-APCI positive (m=z, %): 320
([M þ 1]þ, 100). Anal. calcd. for C21H21NO2: C, 78.97; H, 6.63; N,
4.39. Found: C, 79.02; H, 6.61; N, 4.28.
3-(3,5-Dimethyl-4-nitrophenyl)-7-isopropyl-1,4-dimethylazulene 3c
Green powder, mp 125–126ꢀC; UV=VIS (CH2Cl2), kmax (log e): 248
(4.48), 293 (4.53), 382 (3.85), 600 (1.92). H NMR (CDCl3, 300 MHz,
1
3
d ppm): 1.30 (d, J ¼ 6.9 Hz, 6H, CH3–iPr), 2.28 (s, 6H, 3-CH3, 5-CH3),
2.36 (s, 3H, 30-CH3), 2.58 (s, 3H, 80-CH3), 3.03 (hept, 1H, CH-iPr),
3
6.86 (d, J ¼ 10.7 Hz, 1H, 70-H), 7.05 (s, 2H, 2-H, 6-H), 7.32 (dd,
4
3J ¼ 10.7 Hz, J ¼ 2.0 Hz, 1H, 60-H), 7.42 (s, 1H, 20-H), 8.14 (d,
13
4J ¼ 2.0 Hz, 1H, 40-H). C NMR (CDCl3, 75.47 MHz, d ppm): 12.9 (30-
CH3), 17.9 (3-CH3, 5-CH3), 24.8 (CH3-iPr), 28.1 (80-CH3), 30.1 (CH-iPr),
124.6 (Cq), 127.2 (Cq), 127.5 (Cq), 128.8 (Cq), 131.0 (CH), 134.2 (CH),
135.3 (CH), 135.3 (Cq), 138.4 (Cq), 139.9 (CH), 140.7 (Cq), 143.8 (Cq),
145.9 (CH), 150.7 (C4). MS-APCI positive (m=z, %): 348 ([M þ 1]þ,
100). Anal. calcd. for C23H25NO2: C, 79.51; H, 7.25; N, 4.03. Found:
C, 79.54; H, 7.28; N, 3.98.
2-tert-Butyl-1-(3,5-dimethyl-4-nitrophenyl)-6-methylazulene 3d
Violet powder, mp 106–107ꢀC; UV=VIS (CH2Cl2), kmax (log e): 236
(4.31), 287 (4.75), 294 (4.80), 338 (3.56), 354 (3.82), 569 (broad). 1H NMR
(CDCl3, 400 MHz, d ppm): 1.25 (s, 9H, CH3–tBu), 2.30 (s, 6H, 3-CH3,

3180
A. C. Razus, S. Nica, and E. A. Dragu
3
5-CH3), 2.52 (s, 3H, 60-CH3), 6.86 (dAB, J ¼ 10.2 Hz, 1H, 50-H), 6.99
(dAB,3J ¼ 9.9 Hz, 1H, 70-H), 7.02 (s, 2H, 2-H, 6-H), 7.16 (s, 1H, 30-H),
3
3
7.40 (dAB, J ¼ 10.2 Hz, 1H, 40-H), 8.05 (dAB, J ¼ 9.8, 1H, 80-H). 13C
NMR (CDCl3, 100.62 MHz, d ppm): 17.8 (3-CH3, 5-CH3), 28.0
(60-CH3), 31.2 (CH3–tBu), 34.8 (Cq–tBu), 115.0 (Cq), 124.8 (CH), 124.8
(CH), 127.4 (Cq), 128.9 (CH), 132.5 (CH), 133.4 (CH), 134.9 (CH),
137.6 (Cq), 138.24 (Cq), 142.0 (Cq), 148.0 (Cq), 150.5 (Cq), 159.5 (C4).
MS-APCI positive (m=z, %): 348 ([M þ 1]þ, 100). Anal. calcd. for
C23H25NO2: C, 79.51; H, 7.25; N, 4.03. Found: C, 79.48; H, 7.29; N, 3.92.
Ethyl 3-(3,5-Dimethyl-4-nitrophenyl)-6-methylazulene-1-carboxylate 3e
Brown-reddish powder; 1H NMR (CDCl3, 300 MHz, d ppm): 1.46 (t, 3H,
CH3CH2), 2.41 (s, 6H, 3-CH3, 5-CH3), 2.73 (s, 3H, 60-CH3), 4.43 (q,
3
3J ¼ 7.1 Hz, 2H, CH3CH2), 7.31 (s, 2H, 2-H, 6-H), 7.35 (d, J ¼ 10.6 Hz,
Hz, 1H, 50-H), 7.45 (d, 3J ¼ 10.4 Hz, 1H, 70-H), 8.31 (s, 1H, 20-H), 8.41 (d,
3
3J ¼ 10.2 Hz, 1H, 40-H), 9.53 (d, J ¼ 10.4 Hz, 1H, 80-H)18. MS-APCI
positive (m=z, %, 20 eV): 364 ([M þ 1]þ, 17), 318 ([M þ 1]þ-NO2, 91),
291 ([M þ 1]þ-CO2Et, 17), 246 ([M þ 1]þ-NO2-CO2Et, 100).
1-(3,5-Diphenyl-4-nitrophenyl)-azulene 4a
Brown powder, mp 219–221ꢀC; UV=VIS (CH2Cl2), kmax (log e): 243
(4.65), 299 (4.64), 352 (3.50), 382 (3.85), 572 (2.00); H NMR (CDCl3,
1
3
400 MHz, d ppm): 7.24 (t, J ¼ 9.8 Hz, 2H, 50-H, 70-H), 7.43–7.52 [m,
3
11H, 30-H, phenyl (3), phenyl (5)], 7.60 (t, J ¼ 9.8 Hz, 1H, 60-H), 7.62
3
3
(s, 2H, 2-H, 6-H), 8.07 (d, J ¼ 4.0 Hz, 1H, 20-H), 8.41 (d, J ¼ 9.6 Hz,
1H, 40-H), 8.60 (d, 3J ¼ 10 Hz, 1H, 80-H). 13C NMR (CDCl3,
100.62 MHz, d ppm): 118.0 (CH), 124.0 (CH), 124.4 (CH), 128.2 (CH),
128.4 (Cq), 128.5 (CH), 128.8 (CH), 130.8 (CH), 135.0 (Cq), 135.3
(Cq), 135.7 (Cq), 136.8 (CH), 137.2 (CH), 138.7 (CH), 139.7 (CH),
139.7 (Cq), 142.3 (Cq), 147.8 (C4). MS-APCI positive (m=z, %): 402
([M þ 1]þ, 15), 359 ([M þ 1]þ-NO2, 100). Anal. calcd. for C28H19NO2:
C, 83.77; H, 4.77; N, 3.49. Found: C, 83.81; H, 4.80; N, 3.52.
1-(3,5-Diphenyl-4-nitrophenyl)-4,6,8-trimethylazulene 4b
Brown powder, mp 227–228ꢀC; UV=VIS (CH2Cl2), kmax (log e): 243
(4.70), 299 (4.60), 352 (3.52), 382 (3.83), 572 (2.02). H NMR (CDCl3,
1
300 MHz, d ppm): 2.53 (s, 6H, 40-CH3, 80-CH3), 2.82 (s, 3H, 60-CH3),
6.95 (s, 1H, 50-H), 7.02 (s, 1H, 70-H), 7.27–7.39 [m, 11H, 30-H, phenyl

Synthesis of Azulenyl-benzenes
3181
3
(3), phenyl (5)], 7.38 (s, 2H, 2-H, 6-H), 7.55 (d, J ¼ 4,1 Hz, 1H, 20-H).
13C-NMR (CDCl3, 75.47 MHz, d ppm): 25.4 (40-CH3), 28.3 (60-CH3),
29.2 (80-CH3), 115.2 (CH), 127.8 (Cq), 128.1 (CH), 128.3 (CH), 128.6
(CH), 129.4 (Cq), 131.6 (CH), 133.7 (Cq), 136.3 (CH), 136.7 (Cq),
144.1 (Cq), 146.2 (Cq), 146.9 (Cq), 151.1 (C4). MS-APCI positive
(m=z, %): 444 ([M þ 1]þ, 9), 398 ([M þ 1]þ-NO2, 100). Anal. calcd. for
C31H25NO2: C, 83.95; H, 5.68; N, 3.16. Found: C, 83.98; H, 5.71; N, 3.21.
1-(50-Azulen-1-yl-[1,10;3,100]terphenyl-20-yl)-ethanone 5
Violet powder; mp 190–192ꢀC; UV=VIS (CH2Cl2), kmax (log e): 241
(4.31), 277 (4.19), 302(4.19), 373 (3.74), 582 (broad). H NMR (CDCl3,
1
3
400 MHz, d ppm): 1.95 (s, 3H, CH3), 7.18 (t, J ¼ 9.8 Hz, 2H, 50-H,
70-H), 7.35–7.51 (m, 11H, 30-H and H-phenyls), 7.61 (t, 3J ¼ 9.8 Hz,
3
1H, 60-H), 7.63 (s, 2H, 2-H, 6-H), 8.08 (d, J ¼ 3.9 Hz, 1H, 20-H), 8.36
3
3
(d, J ¼ 9.8 Hz, 1H, 40-H), 8.62 (d, J ¼ 9.8 Hz, 1H, 80-H). 13C NMR
(CDCl3, 100.62 MHz, d ppm): 28.7 (CH3), 116.7 (CH), 122.5 (CH),
122.9 (CH), 126.6 (CH), 127.4 (CH), 128.1 (CH), 128.7 (Cq), 129.2
(CH), 134.5 (CH), 136.2 (CH), 136.5 (CH), 137.1 (Cq), 137.4 (CH),
138.6 (Cq), 139.5 (Cq), 141.0 (Cq), 205.3 (C¼O). IR (solid): selected
stretching vibrations: 2957.5, 2923.7 (nCH3), 1691 (nCO). MS-ESI
positive (m=z, %): 399 ([M þ 1]þ, 100), 381 ([M-H2O]þ, 95). Anal. calcd.
for C30H22O: C, 90.42; H, 5.56. Found: C, 90.38; H, 5.60.
ACKNOWLEDGMENT
The Ministry of Education and Research, Romania, provided part of
the financial support under the framework of Excellency in Research
Program No. CEx 05-D11-20=2005.
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