2-(Azulen-1-yl)-4,6-diphenyl substituted six-membered heteroaromatics

Article abstract of DOI:10.1002/jhet.5570450431

(Chemical Equation Presented) 2-(Azulen-1-yl)-4,6-diphenyl substituted pyranylium salts, pyridinium salts and pyridines were efficiently synthesized and the new obtained compounds were completely characterized. Comparative structural analysis between thes

Full text of DOI:10.1002/jhet.5570450431

Jul-Aug 2008
1139
2-(Azulen-1-yl)-4,6-diphenyl Substituted Six-membered
Heteroaromatics
Alexandru C. Razus,* Liviu Birzan, Oana Zaharia and Cristian Enache
Romanian Academy, Institute of Organic Chemistry, Spl. Independentei, 202B, 060023 - Bucharest 35, P.O.
Box 108, Romania E-mail address: acrazus@cco.ro
Received December 4, 2007
4,6-Diphenylpyran-2-one (1)
1. POCl3; 2. AzH; 3. HClO4
Ph
Ph
Ph
R1NH2/
(C2H5)3N
AcONH4
N+
O+
Az
Ph
Az
Ph
Ph
N
Az
-
R
6-8
-
ClO4
ClO4
3-5
9-11
R = iPr, nBu, Bn, Ph;
Az = azulen-1-yl, 4,6,8-trimethylazulen-1-yl and guaiazulen-1-yl
2-(Azulen-1-yl)-4,6-diphenyl substituted pyranylium salts, pyridinium salts and pyridines were
efficiently synthesized and the new obtained compounds were completely characterized. Comparative
structural analysis between these compounds and their corresponding isomers that contain the azulen-1-yl
moiety in the 4-position of the heterocycle, were carried out. These studies are based on calculated dihedral
angles formed between central heterocycle and the aromatic substituents and on the obtained electronic and
NMR spectra. Due to the restriction in the rotation around azulenyl-pyridinium bond produced by the
quaternary nitrogen substituent, in the herein reported pyridinium salts, the substitution groups of the
quaternary nitrogen atom are prochiral. This property leads to the non-equivalence of gem-protons or gem–
methyl groups of N-substituents in the 1H nmr spectra of the synthesized pyridinium salts.
J. Heterocyclic Chem., 45, 1139 (2008).
and behavior of the synthesized compounds in order to
compare the obtained results with the reported data for
isomers with the azulen-1yl group in the 4-position of the
heterocycles.
INTRODUCTION
In recent years it has become apparent that the azulen-
1-yl moiety can serve as a stabilizing group for electron
deficient molecules as, for example, ionic or neutral
heterocycles. Our recent works has emphasized the
stabilizing influence of the azulen-1-yl group on
pyranylium [1] and pyridinium [2a] salts as well as on
pyridine [2b] when it is attached in the 4-position of these
heterocycles. Besides the interest for generation of these
compounds, which are valuable synthones in other
synthesis, the interdependence between molecular
structure and some of their properties represented another
interesting point of our research. Thus, for 4-(azulen-1-
yl)-2,6-dimethyl-pyridinium salts when the nitrogen was
quaternized by isopropyl we have observed a difference
between chemical shift of the methyl protons at C-2 and
C-6 positions. Moreover, different ꢀH for the heterocyclic
protons, 3-H and 5-H, have been also registered [3]. We
now turn our attention on the 2-(azulen-1-yl) substituted
heterocycles where the azulenyl group is placed in the
neighborhood of the heteroatom. We report herein the
synthesis of 2-(azulen-1-yl)-4,6-diphenyl substituted
pyranylium and pyridinium salts as well as of the
corresponding pyridines. There are several pathways for
the synthesis of azulenyl-substituted heterocycles either
by coupling of suitable substituted azulenes and
heterocycles [4] or starting from pyranones [1,2]. We also
focus our attention on the correlation between structure
RESULTS AND DISCUSSION
Synthesis. The synthesis of 2-(azulen-1-yl) substituted
pyranylium salts was carried out following a similar route
to that used for the generation of corresponding 4-
substituted isomers (Scheme 1) [1]. The first step of the
synthesis pathway consists in halogenation of 4,6-
diphenyl-pyran-2-one, 1 [5], using POCl3.
Table 1
Net charges at carbonyl group of diphenyl-pyranones
Compound
Atom
Net Charge
2-pyranone
C(2)
0.334
4-pyranone
C(4)
0.295
O
-0.301
O
-0.313
The calculated net charges [6] on the atoms of carbonyl
group in pyran-2 and 4-ones (Table 1) showed a smaller
polarization of this group in pyran-2-one, which is hence
less reactive. Therefore, in order to shift the equilibrium
toward the addition product, an excess of POCl3 must be
used. Nevertheless, this excess is limited (2:1 ratio was
used) by the sensitivity of azulenes to POCl3 and by the
difficult isolation of perchlorate in the final step of
reaction.

1140
A. C. Razus, L. Birzan, O. Zaharia, C. Enache
Vol 45
Scheme 1
Table 2.
Yields (ꢀ) for the synthesis of 2-(azulen-1-yl) substituted 4,6-
diphenyl-pyranylium and pyridinium perchlorates and of
corresponding pyridines
Ph
Pyranylium salt
Pyridinea
Pyridinium saltsb
Ph
O
O
1
ꢀ
(%)
ꢀ
(%)
ꢀ
(%)
Comp
Comp.
Comp.
POCl3
3
36
9
42
6iPr
6nBu
6Bn
6Ph
7nBu
7Bn
8nBu
8Bn
8Ph
100
100
69
26
79
57
70
70
34
Ph
Ph
-
PO2Cl2
Cl
OPOCl2
Cl
O+
Ph
4
5
44
45
10
11
43
23
O
Ph
2
1.AzH
2. HClO4
Ph
Ph
O+
Ph
b
aThe yields were calculated starting from pyranone. The yields
were calculated starting from pyranylium salts.
RNH2/
(C2H5)3N
AcONH4
N+
R
Ph
Ph
Az
Az
Ph
N
Az
-
-
ClO4
ClO4
corresponding compounds 12 with azulen-1-yl moiety in
4-position represented in Scheme 2. Therefore, we
consider it interesting to correlate the calculated [9]
dihedral angles with the electronic and NMR spectra of
these compounds.
6-8
9-11
3-5
3,6,9 Az = azulen-1-yl,
4,7,10 Az = 4,6,8-trimethylazulen-1-yl,
5,8,11Az = guaiazulen-1-il
R = iPr, nBu, Bn, Ph
Subsequently, 2-cloropyranylium salt, 2, reacts in situ
[7] with azulene in a nucleophilic reaction [8] followed by
anion exchange with perchloric acid. Unfortunately, the
reaction yields were severe diminished (35-45 %, Table 2)
at the purification of the products by column
chromatography due to the slight solubility of pyranylium
perchlorates 3-5.
Scheme 2
Dihedral angle, ꢀ
(Az-Het)
(2Ph-Het)
(6Ph-Het)
12 X = N
12 X = O+
39o
24o
29o
15o
20o
62o
4o
0o
62o
1'
4
12 X = N+-Me
2
6
The pyridinium salts were obtained generally in good
yields from the pyranylium salts in two-steps reaction
[2a]. The ring opening which requires a basic medium
was accomplished using equimolar amounts of RNH2 and
NEt3. The cyclization of the intermediate to form the
pyridinium ring, in the second step of reaction, has
occurred in the presence of 2 moles of acetic acid per
mole of amine. The reaction time was usually 1 hour for
the first step and two days for the second reaction step.
The yields were good in the case of n-butylamine,
isopropylamine and benzylamine whereas aniline reacted
more difficultly and in lower yields.
Pyridine derivatives are easily synthesized by reaction
of pyranylium salts with excess of ammonium acetate (10
equivalents) [2b]. Similar yields for synthesis of
pyranylium salts, 3 or 4, and for the corresponding
pyridines, 9 or 10, prove that, the reaction pyranylium
salts ꢀ pyridines occurs almost quantitatively.
Ph
X
Ph
[ClO4- for X = O+ or N+-R]
12 X = O+, N+-R or N
For the compounds 12, due to the negligible steric
interaction between the azulenic proton 2'-H and 8'-H and
the heterocycle protons, the dihedral angle ꢁ(Az-Het) is
decisively influenced by the push-pull interaction between
an efficient electron donor and a good acceptor group,
namely, azulene-1-yl and heterocycle moieties. Thus, it
can be concluded that a higher electron conjugation leads
to a smaller ꢁ(Az-Het). This assumption is supported by the
increase of ꢁ(Az-Het) values in series 12 (X = O+) ꢀ 12 (X =
N+-Me) << 12 (X = N) as it is outlined in Scheme 2.
While in the compounds 12 both ortho positions
relative to azulen-1-yl are substituted by hydrogen atoms,
in the series 3-11 one position is substituted by hydrogen
the other represents the heteroatom. As shown in Scheme
3, for these compounds two arrangements of azulene-1-yl
and heterocycle moieties are possible, namely syn and
anti, each with their own steric requirements. Hence, for
comparison we have calculated the dihedral angles for
both series of isomers as is shown in Table 3.
Approach to molecular geometry calculation. The
value of dihedral angles ꢁ formed between the plane of
the heterocycle and the planes of its aromatic substituents,
mainly with the azulen-1-yl moiety, strongly influences
the charge distribution and the magnetic field anisotropy
in the obtained compounds 3-11 as well as in the

Jul-Aug 2008
2-(Azulen-1-yl)-4,6-Diphenyl Substituted Six-Membered Heteroaromatics
1141
and for the corresponding 2-(azulen-1-yl) isomers 9, 3 and
6nBu are outlined in Table 4. Both A and B bands are
intense and well structured for the majority of the
analyzed compounds.
Scheme 3
1"
While the wavelengths of A band are almost the same
for the similar compounds of the two series, the B-band
wavelength are higher shifted for compounds 12 by
comparison with the isomers with azulen-1-yl at C-2 of
heterocycle. Nevertheless, for both series of compounds,
the wavelengths decrease in order X = O+ > X = N+nBu >
X = N. This corresponds just to the decrease of push-pull
efficiency of the electronic system at the increase in
ꢀ(Az-Het) values. The slight hypsochromic shift observed in
the case of the compound 6nBu can be explained by the
highest values of ꢀ(Az-Het) and ꢀ(6Ph-Het) which diminish the
conjugation between the central heterocycle and 2- and 6-
substituents.
The presence of the alkyl groups at azulene moiety in
pyranylium salts causes an increase of ꢀ(Az-Het) value,
therefore on might anticipate a decrease in conjugation
between the two moieties followed by a hypsochromic
shift. However, the better stabilization of the positive
charge on the seven-membered azulene ring, due to the
inductive effect of alkyl groups, reduces the energy gap
between HOMO and LUMO of the entire molecule. As a
consequence, instead the attempted hypsochromic shift a
bathochromic effect on the band A [10] is observed which
increases in series 3 < 4 < 5 (Table 5). A bathochromic
shift in pyridinium salts was also observed at the nitrogen
quaternization with phenyl group instead of alkyl (Table
5). This is a consequence of the lower inductive effect of
phenyl and, at the same time, of the more extended
aromatic system.
1'
1'"
X
X
1
syn
anti
X = N: compound 9
X = O+: compound 3
X = N+-R: compounds 6
Table 3
Dihedral angles for 4-(azulen-1-yl)-4,6-diphenyl substituted pyridine
and pyranylium and pyridinium cations
ꢀ ( o)
Heterocycle
Az-Het
35
6Ph-Het
42
4Ph-Het
41
Pyridine 9 sin
9 anti
43
5
21
42
33
25
40
35
34
Pyranylium 3 sin
3 anti
1-nBu pyridinium
6Bu sin
51
42
54
51
20
29
6Bu anti
As a general rule, for pyranylium salts and pyridines the
isomer syn is preferred because a free space is offered by
the unsubstituted heteroatom to the seven-membered
azulenic ring. Interaction between the strong positive
charge of pyranylium oxygen with azulene-1-yl moiety
reduces the angle ꢀ(Az-Het) close to coplanarity. Strong
steric strain for azulene group appears at the nitrogen
quaternization in pyridinium salts. This is reflected in the
high values of ꢀ(Az-Het) as well as of ꢀ(6Ph-Het). In this case
the anti isomer is favored because the seven-membered
ring is removed from the occupied space by the nitrogen
substituent. Considerations on the influence of the
nitrogen substituent in pyridinium salts upon compounds
properties will be discussed in a special section.
The almost identical wavelengths recorded for the A
band of pyridinium salts 6 (R = iPr) and 6 (R = nBu) arise
from similar steric and inductive effects of the two
groups.
Table 5
Recorded A band in the UV-Vis spectra for 2-azulen-1-yl
substituted compounds 3-6
Electronic spectra. Correlations between the dihedral
angle ꢀ(Az-Het) and the A and B bands of the recorded UV-
Vis spectra for 4-(azulen-1-yl) substituted compounds 12
3
4
5
6iPr
6nBu
6Ph
525
(4.03)
541
(4.23)
557
417
419
435
ꢁmax
(logꢂ)
(4.10) (3.54) (3.55) (3.72)
Table 4
Calculated dihedral angles and the recorded A and B band in the
UV-Vis spectra
Proton NMR spectra. Aromatic protons. The
correlation between chemical shifts, ꢃ, and the structure
for 2,4,6-triarylpyridinium and triarylpyranylium salts
was extensively studied [11]. In our recent paper we have
also discussed some peculiarities observed in the NMR
spectra of compounds 12 [1,2]. During our investigations
we have shown that two main factors are determinant for
the chemical shifts of protons for compounds 12. These
factors are the electronic push-pull effect azulene ꢄ
12 X
O+
24
9
(syn)
35
3
6nBu
(anti)
42
N
39
313sh
N+Me
29
(syn)
ꢀ(o)
ꢁmax
5
B
387
333
306
348
301
(log ꢂ) band (4.32)
(4.17) (4.12) (4.22) (4.33) (4.39)
344
(4.10)
434
ꢁmax
A
370
530
373
525
419
(log ꢂ) band (3.93)
(4.36) (4.39) (3.92) (4.03) (3.55)
378
(3.93)

1142
A. C. Razus, L. Birzan, O. Zaharia, C. Enache
Vol 45
electron density on seven-membered ring expectedly
affects the protons substituted at this moiety, which are
more deshielded. At the same time, the steric interference
acts on 2'-H and to some extent on 8'-H. It is somehow
surprising that the chemical shifts of the last two protons
for the pyridinium salt 6 are placed close or even lower
heterocycle and the change in anisotropy of magnetic
field generated by aromatic substituents and heterocycle
moiety according to the dihedral angle formed by their
planes. Therefore, we consider useful to compare the
obtained 1H-NMR data for the compounds 12 and their 2-
(azulen-1-yl)-substituted isomers.
Table 6
Chemical shifts of the aromatic protons in azulen-1yl substituted heterocycles (ꢁH in ppm)
Compound
Azulenea
12 X = Na
12 X = N+-nBub
12 X = O+b
9a
3-H and or 5-H
2'-H 3'-H
7.81 7.30
8.18 7.53
8.59 7.66
8.92 7.77
8.45
4'-H 5'-H
8.23 7.05
8.44 7.28
8.74 7.68
8.89 8.03
6'-H 7'-H
7.45 7.05
7.72 7.29
8.03 7.68
8.31 8.14
8'-H
8.23
8.71
9.15
9.57
9.96
-
7.95
8.32
8.83
7.89 (5-H),
mc
mc
8.44
7.29
7.08
7.61
7.73
7.43
7.12
7.61
7.97 (3-H)
7.68 (5-H),
7.89 (3-H)
8.33 (5-H),
8.42 (3-H)
8.42 (5-H),
8.57 (3-H)
8.59 (5-H),
8.88 (3-H)
8.71 (5-H),
8.73 (3-H)
10a
7.82
-
8.70
-
-
8.02
-
-
8.78
-
6 nBub
7 nBub
3b
8.46
7.98
9.02
8.56
7.71
7.63
7.75
7.63
7.43d
(7.45)
8.07d
(8.17)
7.88d
7.45d
(7.43)
8.17d
(8.07)
7.89d
8.94
-
8.34
-
9.76
-
4b
(7.89)
(7.88)
b
c
d
aIn CDCl3. In acetone-d6. The signal is a part from a multiplet for more protons. The correct atribution for 5'- and 7'-H signals
failed.
The deshielding effect of 3-H, placed between phenyl
and azulen-1-yl groups is stronger by comparison with 5-
H, as it was expected. It is not surprising that by
alkylation of azulene-1-yl moiety the signals for 3-H and
5-H of all compounds 12 are upfield shifted as a
consequence of the increase in ꢀ(Az-Het). For isomers with
(azulen-1-yl) in 2-position, both protons of the pyridinium
ring are deshielded, whereas a shielding of the ring
protons results in the case of pyridines. The high ꢀ(Az-Het)
value reduces to some extent the conjugation between
pyridinium ring and azulene-1-yl moiety in position 2. As
a consequence, the electron density on the heterocycle is
lowered and determines the slight observed deshielding
effect of its two protons. It might be assumed that the
more intense deshielding of the pyranylium protons is due
to the enhanced positive charge on the ring and this is
really true for the proton at the 5-position. However, the
proton at 3-position is upfield shifted possibly because the
change in the direction of azulene magnetic field with the
increase in ꢀ(Az-Het) value.
than the values for pyridine 9 whereas the other azulene-
1-yl protons are deshielded. We believe that this is
consistent with the higher value of ꢀ(Az-Het) in pyridinium
salts which modifies the magnetic field mainly for 2'- and
8'-H located closely to the heterocycle ring.
R protons in pyridinium salts. As we have pointed out,
our early results indicated a slight anisotropy for 2- and 6-
methyl protons as well as for 3- and 5-H in the case of 4-
(azulene-1-yl)-2,6-dimethyl-1-isopropylpyranilium salt.
The last protons are however equivalent when R = nBu or
Bn. These findings are consistent with the high steric
interference between 2 and 6 methyl substituents and iPr
group which adopts an eclipsed conformation towards the
heterocycle plane [2a,3b]. It was somewhat surprising
that, for the similar 2,6-diphenyl-pyridinium salts 12 even
when R = iPr, the anisotropy disappears. On might
assume that the high dihedral angles (62°) between
phenyls and heterocycle planes minimize the steric
interference imposed to iPr group allowing its free
rotation.
The deshielding of heterocycle protons of both 2- and
4-(azulen-1-yl) substituted pyridinium salts follows the
same order for the significance of R, namely, iPr < Bu <
Bn < Ph, accordingly to the inductive effect of nitrogen
substituent (Table 7).
Substitution of azulene at C-1' with one of the studied
heterocycles (coupled in 2- or 4-position) deshields all
azulene protons according to the molecular charge
distribution and steric factors (Table 6). Thus, the lower
Table 7
The influence of nitrogen quaternization of 2- and 4-(azulen-1-yl)-
diphenyl pyridinium salts on 5- and 7-H (ꢁ in ppm)
Position of
azulen-1-yl
group
Nitrogen substituent
nBu
iPr
Bn
Ph
2
4
8.23/8.32
8.20
8.33/8.42
8.32
8.43/8.56
8.40
8.54/8.68
8.49

Jul-Aug 2008
2-(Azulen-1-yl)-4,6-Diphenyl Substituted Six-Membered Heteroaromatics
1143
For the compound 6iPr two conformers A1 and A2
are possible as it is represented in Scheme 4. High
values of both ꢀ(Az-Het) and ꢀ(6Ph-Het) for compounds 6-8
(Table 3) allow the free rotation around N+-alkyl bond
and explain the non-existence of these conformers.
Contrary to what is observed for the compound 12 N+-
iPr, where the methyls of the iPr group are equivalent,
CONCLUSIONS
We have obtained and characterized three classes of 2-
(azulen-1-yl)-4,6-diphenyl-heterocycles namely, pyranyl-
ium and pyridinium salts and pyridine, respectively. In
order to carry out a comparative structural analysis
between these compounds and their corresponding
isomers with azulen-1-yl moiety in the 4 position of the
heterocycle we have calculated dihedral angles between
the planes of the central heterocycle and the aromatic
substituents. The dihedral angle determines the intensity
of the push-pull effect between the heterocycle and the
aromatic groups as well as the direction of the magnetic
fields generated by the aromatic ring current. This fact is
for 6iPr a difference of 0.19 ppm in ꢁ values of the
H
methyl groups was observed.
While in salts 12 the heterocycle is symmetrically
substituted and around the azulene-pyridinium bond a free
rotation is allowed, in the compounds 6-8 the isopropyl
group is prochiral due to the molecular asymmetry
generated by the rotational restriction around the azulene -
pyridinium bond produced by the substituent at the
quaternary nitrogen. This explains the ꢀꢁH between the
methyl groups.
1
well reflected in the electronic and H-NMR spectra of
both isomer series. Perhaps the most interesting result
from this contribution can be associated to the behavior in
magnetic field of the substituents at nitrogen in
pyridinium salts with azulenyl group in 2-position,
compounds 6-8. In these compounds the substituent at
quaternary nitrogen is prochiral due to the molecular
asymmetry generated by the rotational restriction around
azulene-pyridinium bond produced just by the
neighborhood of nitrogen substituent. This property
generates the magnetically non-equivalence of geminal
The ꢀꢁH of 0.18 ppm between AB doublets of
methylene protons in salt 6Bn is consistent with the fact
that these protons are diastereotopic.
Scheme 4
Az
Ph
Ph
1
protons or methyl groups of R in the H-NMR spectra of
N+
iPr
N+
N+
Az
CH3
Ph
Ph
Ph
Ph
Az
H3C
salts 6-8. One may wonder how the above presented
structural conclusions, based mainly from spectral data,
are in accord with the structural compound features which
will be given by the crystal structure analysis. It is
expected that the crystallographic packing interactions
will change the compounds environment and will reduce
their freedom degrees comparatively to the behavior in
the NMR solution. This viewpoint of the research is in
progress.
H
H
CH3
CH3
12 X = N+iPr
6iPr (A1)
6iPr (A2)
6iPr: 2 d, ꢀꢁ 1.25 and 1.44 ppm, 3J = 7.2 Hz, each for 3H, 2CH3
and hept, ꢀꢁ 5.26, 3J = 7.2 Hz, for 1H, (CH3)2CH
12 X = N+iPr: d, ꢀꢁ 1.44 ppm, 3J = 7.2 Hz, 6H, 2CH3 and hept,
ꢀꢁ 5.18 ppm, J = 7.2 Hz, for 1H, (CH3)2CH
Prochirality of butyl group in 6nBu made also
diastereotopic the protons of methylene linked to
nitrogen, (CH2) ꢁ. They couple each other with a high
gem-coupling constant and are also coupled with their
neighboring methylene protons. These last protons are, in
turn, magnetically non-equivalent therefore the
multiplicity of (CH2)ꢁ signal becomes dABdd with 2J = 13.6
Hz, J = 10.8 Hz, J = 5.6 Hz [12]. It is interesting to
observe that the last two values indicate a rather rigid
conformation for the (CH2)ꢂ-(CH2)ꢁ fragment. The rule
that the effect of prochirality decreases with the distance
from the center of asymmetry [13] is true also for the n-
butyl chain of compounds 6-8nBu. In this case ꢀꢁH for
pairs of diastereotopic methylene protons decrease with
the distance to heterocycle (for 6nBu, ꢀꢁH in ppm: (CH2)ꢁ
= 0.20; (CH2)ꢂ = 0.09; (CH2)ꢃ = 0.01). It is important to
note that for all pyridinium salts, the value of ꢀꢁH
decrease with the increase of temperature until signals
coalescence [14].
EXPERIMENTAL
Melting points: Kofler apparatus (Reichert Austria).
Elemental analyses: Perkin Elmer CHN 240B. UV-Vis spectra
in methanol: Varian Cary 100 spectrophotometer. H and 13C
1
nmr: Bruker Avance DRX4 (1H nmr: 400 MHz, 13C nmr: 100.62
MHz), ꢁ are expressed in ppm J in Hz, TMS was used as internal
standard in acetone-d6 and CDCl3 at the room temperature;
COSY and HETCOR correlation experiments were used for the
structure assignment (the numbering for the compounds is
indicated in the Schemes). Mass spectra: JEOL JMS-DX303
spectrometer coupled to analytical gas-chromatograph Shimadzu
GC-14B with a DB-1 capillary column and C-R6A integrator
and Finnigan MAT 311-A/100 MS. Column chromatography:
silica gel [70-230 mesh (ASTM)]. Dichloromethane (DCM) was
distilled over CaH2, and diethyl ether was conserved on NaOH
and freshly distilled on LiAlH4.
3
3
General Procedures for Synthesis.
Synthesis of 4,6-diphenyl-pyranylium salts substituted in
2-position with (azulen-1-yl) moieties. 4,6-Diphenyl-pyran-2-

1144
A. C. Razus, L. Birzan, O. Zaharia, C. Enache
Vol 45
one [4] (0.1 mmol) and freshly distilled POCl3 (0.2 mmol) were
dissolved in nitromethane (~ 2 mL). The stirred reaction mixture
was heated at 60 °C for 6 hour. Then, it was cooled at room
temperature and azulenic compound (0.2 mmol) was added to
the mixture. The stirring was continued over night. Finally, an
excess of perchloric acid 70 % was added and the temperature
was raised to 70-80 °C when an evolvement of HCl was
observed. After cooling down, the pyranylium salts were
precipitated in ether and separated by filtration. The solid was
chromatographed on silica gel column with benzene-acetone
(from 0 % to 100 % acetone) as eluent. If unreacted azulene
derivatives are present in the reaction mixture, they were eluted
first. Then, a brown material, mainly pyranone, was separated
and finally the pyranylium salt was collected (the yields are
reported in Table 2).
Synthesis of 4,6-diphenyl-pyridines substituted in 2-
position with (azulen-1-yl) moieties. Pyranylium perchlorate
(without purification) was refluxed in ethanol with ammonium
acetate (molar ratio perchlorate:acetate = 1:10) for one hour. The
solvent was evaporated under vacuum and the residue dissolved
in a small amount of DCM and washed with water. The organic
layer was dried (over Na2SO4) and the solvent was removed
under vacuum. The chromatography on silica-gel using n-
pentane-DCM (from 0 % to 100 % DCM) as eluent afforded the
pure pyridines (the yields are reported in Table 2) as blue or
green solutions.
Synthesis of 4,6-diphenyl-pyridinium salts substituted in
2-position with (azulen-1-yl) moieties. Under inert atmosphere
(for avoiding air moisture), pure pyranylium perchlorate (1
mmol), amine, RNH2, (1 mmol) and triethylamine (1 mmol)
were dissolved in DCM (40 mL) with magnetically stirring, at
room temperature. The stirring was continued for 30-60 minutes.
Then, acetic acid (2 mmol) was added and the reaction mixture
was stirred for 48 hours at room temperature. The solvent was
evaporated under vacuum and the products were separated from
the obtained tar on silica gel with DCM and ethanol (from 0 %
to 5% ethanol). The separated salts (the yields are reported in
Table 2) are usually brown in solution.
2.97 (s, 3H, Az-Me), 3.07 (s, 3H, Az-Me), 7.63 (d, J = 4.8 Hz,
1H, 3'-H), 7.73-7.87 (m, 6H, 3"-H, 4"-H, 5"-H 3"'-H, 4'"-H, 5"'-
H), 7.88 (s, 1H, 5'-H or 7'-H) 7.89 (s, 1H, 7'-H or 5'-H), 8.38
(dd, J = 7.6, 1.4 Hz, 2H, 2"-H, 6"-H), 8.44 (dd, J = 7.2, 1.4 Hz,
2H, 2"'-H, 6"'-H), 8.56 (d, J = 4.8 Hz, 1H, 2'-H), 8.71 (d, J = 1.2
Hz, 1H, 5-H), 8.73 (s, 1H, 3-H) ppm; 13C nmr (acetone-d6): ꢀ
25.89 (Az-Me), 28.28 (Az-Me), 29.27 (Az-Me), 118.0 (C3),
112.0 (C5), 124.9 (C3'), 128.4 (C2", C6"), 129.8 (C2"', C6"'),
130.7 (CH), 130.9 (CH), 134.7 (CH), 134.9 (CH), 135.2 (Cq),
135.5 (Cq), 136.6 (CH), 136.8 (CH), 137.8 (Cq), 140.3 (C2'),
146.6 (Cq), 150.5 (Cq), 151.3 (Cq), 162.3 (C4), 169.0 (C6),
171.0 (C2) ppm; ms (ESI): 401 (M+, 100%). Anal. Calcd. for
C30H25O5Cl: C, 71.93; H, 5.03;. Found: C, 71.95; H, 5.06.
2-(5-Isopropyl-3,8-dimethyl-azulen-1-yl)-4,6-diphenyl-
pyranylium perchlorate, 5. Dark brown crystals (blue in
solution), mp 164 °C; uv (MeOH), ꢀmax (log ꢁ): 217 (4.34), 238
(4.36), 332 (4.31), 351 (4.25), 394 (3.98), 557 (4.10). 1H nmr
(acetone-d6): ꢀ 1.49 (d, J = 6.8 Hz, 6H, Me2CH), 2.73 (s, 3H,
Me(3')), 2.99 (s, 3H, Me(8')), 3.43 (hept, J = 6.8 Hz, 1H,
Me2CH), 7.72-7.86 (m, 6H, 3"-H, 4"-H, 5"-H, 3"'-H, 4"'-H, 5"'-
H), 7.96 (dAB, J = 10.8 Hz, 2H, 7'-H), 8.16 (dABd, J = 10.8, 2.0
Hz, 1H, 6'-H), 8.38 (dt, J = 8.0, 1.2 Hz, 2H, 2"-H, 6"-H), 8.44
(dt, J = 8.0, 1.2 Hz, 2H, 2"'-H, 6"'-H), 8.57 (s, 1H, 2'-H), 8.63 (s,
2H, 3-H, 5-H), 8.67 (d, J = 2.0 Hz, 1H, 4'-H) ppm; 13C nmr
(acetone-d6): ꢀ 13.6 (Az-Me(3')), 25.5 (CHMe2), 29.0 (Az-
Me(8')), 39.6 (CH(CH3)2), 111.3 (C5), 118.8 (C3'), 128.6 (C2",
C6"), 130.8 (C2"', C6"'), 131.2 (CH), 131.3 (CH), 131.6 (C3),
135.0 (CH), 135.2 (CH), 135.5 (Cq), 135.8 (Cq), 137.3 (C7'),
137.8 (C4'), 140.0 (C6'), 142.6 (C2'), 143.0 (Cq), 146.3 (Cq),
151.0 (Cq), 154.5 (Cq), 162.0 (C4), 168.3 (C6), 170.5 (C2) ppm;
ms (ESI): 429 (M+, 100%). Anal. Calcd. for C32H29O5Cl: C,
72.65; H, 5.53. Found: C, 72.60; H, 5.63.
2-(Azulen-1-yl)-1-isopropyl-4,6-diphenyl-pyridinium per-
chlorate, 6iPr. Brown crystals, mp 108 °C; uv (MeOH), ꢀmax
(log ꢁ):232 (4.26), 282 (4.41), 301 (4.29), 417 (3.54); 1H nmr
(acetone-d6): ꢀ 1.25 (d, J = 7.2 Hz, 3H, CH3CH), 1.44 (d, J = 7.2
Hz, 3H, CH3CH), 5.26 (hept, J = 7.2 Hz, 2H, (CH3)2CH), 7.52 (t,
J = 9.9 Hz, 1H, 5'-H or 7')-H), 7.55 (t, J = 9.6 Hz, 1H, 7'-H or 5'-
H), 7.56-7.61 (m, 3H, 3"'-H, 4"'-H, 5"'-H), 7.66 (d, J = 4.0 Hz,
1H, 3'-H), 7.68-7.73 (m, 3H, 3"-H, 4"-H, 5"-H), 7.86-7.92 (m,
2H, 2"-H, 6"-H), 7.96 (t, J = 9.9 Hz, 1H, 6'-H), 8.09 (d, J = 7.0
Hz, 2H, 2"'-H, 6"'-H), 8.23 (d, J = 2.3 Hz, 1H, 5-H), 8.31 (d, J =
2.4 Hz, 1H, 3-H), 8.32 (d, J = 4.2 Hz, 1H, 2'-H), 8.60 (d, J = 9.8
Hz, 1H, 4'-H), 8.75 (d, J = 9.5 Hz, 1H, 8'-H) ppm; 13C nmr
(acetone-d6): ꢀ 23.02 (CHMe), 23.99 (CHMe), 63.56 (Me2CH),
118.6 (C3'), 121.5 (C1'), 127.1 (C5', C7'), 128.1 (C5), 129.2
(C2"', C6"'), 130.2 (C3), 130.3 (CH), 130.4 (C2", C6"), 130.5
(CH), 131.5 (CH), 132.8 (CH), 134.6 (Cq), 135.2 (Cq), 137.4
(C8'), 139.4 (Cq), 139.6 (C2'), 140.1 (C4'), 140.8 (C6'), 142.9
(Cq), 154.3 (C2), 155.2 (C4), 158.8 (C6) ppm; ms (ESI): 402
(M+, 100%). Anal. Calcd. for C30H26ClNO4: C, 72.12; H, 5.25;
N, 2.81. Found: C, 72.21; H, 5.34; N, 2.72.
Product Characterization.
2-(Azulen-1-yl)-4,6-diphenyl-pyranylium perchlorate, 3.
Dark brown crystals, (red in solution), mp 280 °C; uv (MeOH),
ꢀmax (log ꢁ): 216 (4.33), 247 (4.35), 285 (4.30), 327 (4.31), 348
(4.33), 525 (4.03); 1H nmr (acetone-d6): ꢀ 7.72-7.80 (m, 2H, 3"-
H, 5"-H), 7.75 (d, J = 5.0, 1H, 3'-H), 7.80-7.89 (m, 4H, 4"-H,
3"'-H, 4"'-H, 5"'-H), 8.07 (t, J = 10.0 Hz, 1H, 5'(or 7')-H), 8.17 (t,
J = 10.0 Hz, 1H, 7'(or 5')-H), 8.34 (t, J = 10.0 Hz, 1H, 6'-H) 8.43
(d, J = 7.6 Hz, 2H, 2"-H, 6"-H), 8.50 (dd, J = 8.0, 1.6 Hz, 2H,
2'"-H, 6'"), 8.59 (d, J = 1.6 Hz, 1H, 5-H), 8.88 (d, J = 1.6 Hz,
1H, 3-H), 8.94 (d, J = 10.0 Hz, 1H, 4'-H), 9.02 (d, J = 4.4 Hz,
1H, 2'-H), 9.76 (d, J = 10.0 Hz, 1H, 8'-H) ppm; 13C nmr
(acetone-d6): ꢀ 113.1 (C5), 118.0 (C3), 124.9 (C3'), 129.3 (C2"',
C6"'), 130.4 (C2", C6"), 131.4 (C3"', C5"'), 131.6 (C3", C5"),
134.6 (C5'), 134.8 (C7'), 135.2 (C1"', C1'), 135.3 (C4"'), 135.4
(C4"), 135.7 (C1"), 140.2 (C8'), 142.0 (C2'), 142.1 (C3a'), 142.5
(C4'), 144.4 (C6'), 151.9 (C8a'), 162.4 (C4), 169.5 (C6), 171.5
(C2) ppm; ms (ESI): 359 (M+, 100%). Anal. Calcd. for
C27H19O5Cl: C, 70.67; H, 4.17. Found: C, 70.53; H, 4.35.
2-(Azulen-1-yl)-1-(but-1-yl)-4,6-diphenyl-pyridinium per-
chlorate, 6nBu. Brown crystals, mp 101 °C, uv (MeOH), ꢀmax
(log ꢁ): 231 (4.26), 281 (4.38), 301 (4.29), 419 (3.55); 1H nmr
(acetone-d6): ꢀ 0.29 (t, 3J = 7.2 Hz, 3H, Bu-CH3), 0.73 (sext, J =
7.2 Hz, 1H, Buꢁ(CH2)ꢂ), 0.74 (sext, J = 7.2 Hz, 1H, Buꢁ(CH2)ꢂ),
1.27-1.39 (m, 1H, Buꢁ(CH2)ꢃ), 1.46-1.58 (m, 1H, Buꢁ(CH2)ꢃ),
4.46-4.54 (m, 1H, Buꢁ(CH2) ꢄ), 4.76-4.84 (m, 1H, Buꢁ(CH2) ꢄ),
7.59-7.69 (m, 3H, 4"-H, 3"'-H, 5"'-H), 7.61 (t, J = 6.8 Hz, 1H, 5'-
H or 7'-H), 7.64 (t, J = 9.6 Hz, 1H, 7'-H or 5'-H), 7.71 (d, J = 4.4
Hz, 1H, 3'-H), 7.73-7.77 (m, 3H, 4"'-H, 3"-H, 5"-H), 7.97-8.01
4,6-Diphenyl-2-(4,6,8-trimethyl-azulen-1-yl)-pyranylium
perchlorate, 4. Dark brown crystals (violet in solution), mp 185
°C; uv (MeOH), ꢀmax (log ꢁ): 216 (4.33), 244 (4.47), 333 (4.47),
385 (3.88), 541(4.23). 1H nmr (acetone-d6): 2.85 (s, 3H, Az-Me),

Jul-Aug 2008
2-(Azulen-1-yl)-4,6-Diphenyl Substituted Six-Membered Heteroaromatics
1145
(m, 2H, 2"-H, 6"-H), 8.02 (t, J = 9.6 Hz, 1H, 6'-H), 8.16 (dd, J =
8.0, 1.2 Hz, 2H, 2"'-H, 6"'-H), 8.33 (d, J = 2.4 Hz, 1H, 5-H),
8.42 (d, J = 2.4 Hz, 1H, 3-H), 8.46 (d, J = 4.8 Hz, 1H, 2'-H),
8.70 (d, J = 9.6 Hz, 1H, 4'-H), 8.78 (d, J = 9.6 Hz, 1H, 8'-H)
ppm; 13C nmr (acetone-d6): ꢀ 13.57 (Bu-CH3), 20.38
(Buꢁ(CH2)ꢂ), 32.92 (Buꢁ(CH2)ꢃ), 56.52 (Buꢁ(CH2) ꢄ), 120.0
(C3'), 121.2 (C1'), 127.4 (C3), 128.1 (C5' or 7'), 128.3 (C7'or 5'),
129.7 (C5), 129.9 (C2"', C6"'), 130.7 (C3"', C5"'), 130.8 (C2",
C6"), 131.2 (C3", C5"), 132.4 (C4"'), 133.6 (C4"), 135.1 (Cq),
135.6 (Cq), 137.5 (C4'), 139.5 (C2'), 139.8 (Cq), 140.8 (C8'),
141.7 (C6'), 144.1 (Cq), 155.0 (C2), 156.0 (C6), 158.5 (C4) ppm;
ms (ESI): 414 (M+, 100%). Anal. Calcd. for C31H28ClNO4: C,
72.49; H, 5.50; N, 2.73. Found: C, 72.35; H, 5.78; N, 2.61.
2-(Azulen-1-yl)-1-benzyl-4,6-diphenyl-pyridinium per-
chlorate, 6Bn. Brown crystals, mp 98 °C; uv (MeOH), ꢀmax (log
(t, J = 7.2 Hz, 2H, 3"'-H, 5"'-H), 7.69 (t, J = 7.2 Hz, 1H, 4"'-H),
7.72-7.78 (m, 2H, 3"-H, 5"-H), 7.89-7.94 (m, 2H, 2"-H, 6"-H),
7.98 (d, J = 4.0 Hz, 1H, 2'-H), 8.23 (dd, J = 7.6, 1.4 Hz, 2H, 2"'-
H, 6"'-H), 8.42 (d, J = 2.0 Hz, 1H, 5-H), 8.57 (d, J = 2.4 Hz, 1H,
3-H) ppm; 13C nmr (acetone-d6): ꢀ 13.48 (Bu-CH3), 20.59
(Buꢁ(CH2)ꢂ), 26.58 (Az-Me(6')), 28.82 (Az-Me(8')), 29.27 (Az-
Me(4')), 32.42 (Buꢁ(CH2)ꢃ), 56.20 (Buꢁ(CH2) ꢄ), 118.0 (C3'),
120.7 (C1'), 127.6 (C5), 129.5 (C3), 130.0 (C2"', C6"'), 130.6
(C4"), 130.8 (C2", C6"), 130.9 (C3", C5"), 131.3 (C3"', C5"'),
131.6 (C4"'), 132.6 (C5'), 132.9 (C7'), 134.5 (Cq), 134.6 (Cq),
134.7 (Cq), 137.7 (C2'), 140.3 (Cq), 148.6 (C8'), 150.2 (C4'),
151.0 (C6'), 155.5 (C6), 157.6 (C4), 159.3 (C2) ppm; ms (ESI,
m/z, %): 456 (M+, 100). Anal. Calcd. for C34H34ClNO4: C, 73.44;
H, 6.16; N, 2.52. Found: C, 73.35; H, 6.13; N, 2.50.
1-Benzyl-4,6-diphenyl-2-(4,6,8-trimethyl-azulen-1-yl)-pyr-
idinium perchlorate, 7Bn. brown crystals, mp 105 °C; uv
(MeOH), ꢀmax (log ꢁ): 227 (4.35), 241 (4.36), 296 (4.44), 342sh
1
ꢁ): 233 (4.36), 285 (4.30), 305 (4.21), 430 (3.58); H nmr
(acetone-d6): ꢀ 5.84 (dAB, J = 16.0 Hz, 1H, Ph-CH2), 6.02 (dAB, J
= 16.0 Hz, 1H, Ph-CH2), 6.56 (dd, J = 8.0, 2.0 Hz, 2H, 2IV-H,
6IV-H), 6.92-7.01 (m, 3H, 3IV-H, 4IV-H, 5IV-H), 7.48 (t, J = 9.6
Hz, 1H, 5'(or 7')-H), 7.55-7.73 (m, 8H, 3'-H, 7'(or 5')-H, 3"'-H,
1
(3.86), 439 (3.68); H nmr (acetone-d6): ꢀ 2.60 (s, 3H, Me(8')),
2.73 (s, 3H, Me(6')), 2.99 (s, 3H, Me(4')), 5.75 (dAB, J = 16.0 Hz,
1H, Ph-CH), 5.93 (dAB, J = 15.6 Hz, 1H, PhꢁCH), 6.56 (d, J =
7.6 Hz, 2H, 2IV-H, 6IV-H), 7.08 (t, J = 7.6 Hz, 2H, 3IV-H, 5IV-H),
7.18 (t, J = 7.6 Hz, 1H, 4IV-H), 7.44 (s, 1H, 5'-H or 7'-H), 7.49
(d, J = 4.4 Hz, 1H, 3'-H), 7.52 (s, 1H, 7'-H or 5'-H), 7.60-7.78
(m, 8H, 5H for 4-Ph and 3"'-H, 4"'-H, 5"'-H), 7.87 (d, J = 4.4 Hz,
1H, 2'-H), 8.28 (dd, J = 7.8, 1.4 Hz, 2H, 2"'-H, 6"'-H), 8.50 (d, J
= 2.4 Hz, 1H, 5-H), 8.65 (d, J = 2.4 Hz, 1H, 3-H) ppm; 13C nmr
(acetone-d6) [16]: ꢀ 26.56 (Az-Me(6')), 28.82 (Az-Me(8')), 29.24
(Az-Me(4')), 50.19 (PhCH2), 118.1 (CH), 120.9 (Cq), 127.7
(C5), 128.1 (CH), 129.5 (C3), 129.7 (CH), 130.1 (CH), 130.5
(CH), 130.7 (CH), 130.8 (CH), 131.3 (CH), 131.8 (CH), 133.1
(CH), 132.5 (CH), 134.1 (Cq), 134.6 (Cq), 134.9 (Cq), 135.5
(CH), 137.8 (C2'), 140.8 (Cq), 148.7(C8'), 150.3 (C4'), 151.1
(C6'), 153.3 (Cq), 158.2 (Cq), 159.6 (Cq) ppm; ms (ESI, m/z,
%): 490 (M+, 100). Anal. Calcd. for C37H32ClNO4: C, 75.31; H,
5.47; N, 2.37. Found: C, 75.40; H, 5.64; N, 2.45.
4
4"'-H, 5"'-H, 3"-H, 4"-H, 5"-H), 7.78 (dd, J = 7.2 Hz, J = 1.2
Hz, 2H, 2"-H, 6"-H), 7.93 (t, J = 9.8 Hz, 1H, 6'-H), 8.23 (dd, J =
8.0, 1.2 Hz, 2H, 2"'-H, 6"'-H), 8.32 (d, J = 4.0 Hz, 1H, 2'-H),
8.43 (d, J = 2.4 Hz, 1H, 5-H ), 8.51 (d, J = 9.2 Hz, 1H, 4'-H),
8.56 (d, J = 2.4 Hz, 1H, 3-H), 8.68 (d, J = 9.6 Hz, 1H, 8'-H)
ppm; 13C nmr (acetone-d6): ꢀ 59.65 (PhCH2), 119.5 (C3'), 120.6
(C1'), 126.6 (C4IV), 126.9 (C2IV, C6IV), 127.6 (C5), 127.7 (C5'),
128.7 (C3), 129.0 (C7'), 129.3 (C2"', C6"'), 129.4 (C2", C6"),
130.0 (C3", C5", C3"', C5"'), 130.6 (C3IV, C5IV), 131.8 (C4"'),
133.2 (C4"), 134.4 (Cq), 134.8 (Cq), 135.3 (Cq), 136.6 (C8'),
138.5 (C2'), 139.1 (Cq), 140.1 (C4'), 141.0 (C6'), 143.8 (Cq),
155.2 (C2), 156.2 (C6), 158.8 (C4) ppm; ms (ESI): 448 (M+,
100%). Anal. Calcd. for C34H26ClNO4: C, 74.52; H, 4.78; N,
2.56. Found: C, 74.43; H, 4,85; N, 2.48.
2-(Azulen-1-yl)-1,4,6-triphenyl-pyridinium perchlorate,
6Ph. Brown crystals, mp 123 °C; uv (MeOH), ꢀmax (log ꢁ): 233
(4.36), 284 (4.41), 311 (4.34), 435 (3.72); 1H nmr (acetone-d6): ꢂ
7.15-7.26 (m, 3H, aromatics), 7.31 (d, J = 4.0 Hz, 1H, 3'-H),
7.38-7.47 (m, 4H, aromatics), 7.52-7.61 (m, 5'-H, 7'-H and 3H
aromatics), 7.62 (d, J = 4.4 Hz, 1H, 2'-H), 7.71 (tt, 1H, J = 7.2,
1.4 Hz, 4"'-H) 7.72 (t, 2H, J = 8.0 Hz, 3"'-H, 5"'-H), 7.97 (t, J =
9.8 Hz, 1H, 6'-H), 8.30 (dt, J = 8.0, 1.4 Hz, 2H, 2'"-H, 6"'-H),
8.54 (d, J = 2.0 Hz, 1H, 5-H), 8.58 (d, J = 9.6 Hz, 1H, 4'-H),
8.68 (d, J = 2.0 Hz, 1H, 3-H), 8.84 (d, J = 10.0 Hz, 1H, 8'-H)
ppm; 13C nmr (acetone-d6) [15]: ꢂ 118.9 (CH), 120.8 (Cq), 125.6
(C5), 127.4 (CH), 127.5 (CH), 128.1 (C3), 129.1 (CH), 129.4
(CH), 129.6 (CH), 130.6 (CH), 130.7 (CH), 130.9 (CH), 134.5
(Cq), 135.1 (Cq), 136.9 (CH), 139.4 (CH), 139.7 (CH), 140.7
(CH), 140.8 (Cq), 143.3 (Cq), 154.7 (Cq), 156.6 (Cq), 158.1
(Cq) ppm; ms (ESI): 434 (M+, 100%). Anal. Calcd. for
C33H24ClNO4: C, 74.22; H, 4.53; N, 2.62. Found: C, 74.35; H,
4.62; N, 2.70.
1-(But-1-yl)-2-(5-isopropyl-3,8-dimethyl-azulen-1-yl)-4,6-
diphenyl-pyridinium perchlorate, 8nBu. Brown crystals, mp
118 °C; uv (MeOH), ꢀmax (log ꢁ): 225 (4.31), 242 (4.36), 294
1
(4.42), 356 sh (3.73), 455 (3.46); H nmr (acetone-d6): ꢀ 0.33 (t,
J = 7.4 Hz, 3H, Bu-CH3), 0.75 (sext, J = 7.2 Hz, 2H,
Buꢁ(CH2)ꢂ), 1.44 (d, J = 6.8 Hz, 6H, Me2CH), 1.47-1.59 (m, 2H,
Buꢁ(CH2)ꢃ), 2.64 (s, 3H, Az-Me8), 2.76 (s, 3H, Az-Me3), 3.29
(hept, J = 6.8 Hz, 1H, Me2CH), 4.41 (dABdd, J = 13.6, 10.8, 5.6
Hz, 1H, Buꢁ(CH2)ꢄ), 4.69 (dABdd, J = 13.6, 10.8, 5.6 Hz, 1H,
Buꢁ(CH2)ꢄ), 7.43 (d, J = 10.4 Hz, 1H, 7'-H), 7.66 (t, J = 6.8 Hz,
2H, 3"'-H, 5"'-H), 7.69 (t, J = 6.8 Hz, 1H, 4"'-H), 7.73-7.78 (m,
3H, 3"-H, 4"-H, 5"-H), 7.82 (dd, J = 10.8, 2.0 Hz, 1H, 6'-H),
7.92-7.94 (m, 2H, 2"-H, 6"-H), 8.01 (s, 1H, 2'-H), 8.23 (dt, J =
8.0, 1.6 Hz 2H, 2"'-H, 6"'-H), 8.42 (d, J= 2.0 Hz, 1H, 5-H), 8.55
(d, J = 2.4 Hz, 1H, 3-H), 8.58 (d, J = 2.4 Hz, 1H, 4'-H) ppm; 13
C
nmr (acetone-d6) [13]: ꢀ 13.50 (Bu-CH3), 13.60 (Az-Me(3')),
20.58 (Buꢁ(CH2)ꢂ), 25.48 (Me2CH), 27.98 (Az-Me(8')), 32.41
(Buꢁ(CH2)ꢃ), 39.40 (Me2CH), 56.20 (Buꢁ(CH2) ꢄ), 127.6 (Cq),
117.8 (C1'), 127.5 (C5), 129.8 (C3), 130.0 (C2"', C6"'), 130.8
(C2", C6"), 130.9 (C3", C5"), 131.3 (C3"', C5"'), 131.6 (C4"'),
132.6 (C7'), 133.9 (C4"), 134.8 (Cq), 134.8 (Cq), 136.0 (Cq),
137.4 (C4'), 138.7 (C6'), 140.6 (C2'), 140.8 (Cq), 145.7 (Cq),
147.2 (Cq), 155.1 (C6), 157.6 (C4), 159.3 (C2) ppm; ms (ESI,
m/z, %): 484 (M+, 100). Anal. Calcd. for C36H38ClNO4: C, 74.02;
H, 6.56; N, 2.40. Found: C, 74,06; H, 6,63; N, 2.35.
1-(But-1-yl)-4,6-diphenyl-2-(4,6,8-trimethyl-azulen-1-yl)-
pyridinium perchlorate, 7nBu. Brown crystals, mp 144 °C; uv
(MeOH), ꢀmax (log ꢁ): 221 (4.38), 242 (4.41), 294 (4.48), 357
1
(3.80), 451 (3.59); H nmr (acetone-d6): ꢀ 0.32 (t, J = 7.2 Hz,
3H, Bu-CH3), 0.72 (sext, J = 7.2 Hz, 2H, Buꢁ(CH2)ꢂ), 1.49-1.55
(m, 2H, Buꢁ(CH2)ꢃ), 2.65 (s, 3H, Az-Me(8')), 2.73 (s, 3H, Az-
Me(6')), 3.03 (s, 3H, Az-Me(4')), 4.34 (dABdd, J = 13.4, 10.5, 5.8
Hz, 1H, Buꢁ(CH2)ꢄ), 4.63 (dABdd, J = 13.4, 10.5, 6.0 Hz, 1H,
Buꢁ(CH2)ꢄ), 7.43 (s, 1H, 5'-H or 7'-H), 7.45 (s, 1H, 7'-H or 5'-
H), 7.56-7.60 (m, 1H, 4"-H), 7.63 (d, J = 4.0 Hz, 1H, 3'-H), 7.67
1-Benzyl-2-(5-isopropyl-3,8-dimethyl-azulen-1-yl)-4,6-di-
phenyl-pyridinium perchlorate, 8Bn. Brown crystals, mp 121

1146
A. C. Razus, L. Birzan, O. Zaharia, C. Enache
Vol 45
°C; uv (MeOH), ꢀmax (log ꢁ): 219 (4.35), 243 (4.36), 294 (4.39),
347sh (3.85), 467 (3.44). 1H nmr (acetone-d6): ꢂ 1.43 (d, J = 6.8
Hz, 6H, Me2CH), 2.55 (s, 3H, Me(8')), 2.65 (s, 3H, Me(3')),
3.25-3.35 (m, 1H, Me2CH), 5.77 (dAB, J = 15.6 Hz, 1H, PhꢀCH),
5.97 (dAB, J = 15.6 Hz, 1H, PhꢀCH), 6.54 (d, J = 7.6 Hz, 2H, 2IV-
H, 6IV-H), 7.07 (t, J = 7.6 Hz, 2H, 3IV-H, 5IV-H), 7.17 (t, J = 7.6
Hz, 1H, 4IV-H), 7.40 (d, J = 10.4 Hz, 2H, 7'-H), 7.61-7.73 (m,
6H, 3"-H, 4"-H, 5"-H, 3"'-H, 4"'-H, 5"'-H), 7.68 (dt, J = 6.8, 2.0
Hz, 2H, 2"-H, 6"-H), 7.81 (dd, J = 10.8, 2.0 Hz, 1H, 6'-H), 7.86
(s, 1H, 2'-H), 8.27 (dt, J = 8.0, 1.6 Hz, 2H, 2"'-H, 6"'-H), 8.48 (d,
J = 2.2 Hz, 1H, 5-H), 8.53 (d, J = 2.0 Hz, 1H, 4'-H), 8.61 (d, J =
2.4 Hz, 1H, 3-H) ppm; 13C nmr (acetone-d6) [14]: ꢁ 13.54
(Me)3')), 25.42 (Me2CH), 27.96 (Me(8')), 39.45 (Me2CH), 60.00
(PhCH2), 118.3 (CH), 127.4 (C5), 127.7 (Cq), 128.3 (C2IV,
C6IV), 129.7 (C4IV), 129.8 (C3), 130.0 (C3IV, C5IV), 130.1 (CH),
130.8 (CH), 130.9 (CH), 131.3 (CH), 131.9 (CH), 132.1 (C7'),
134.1 (CH), 134.9 (CH), 135.3 (Cq), 136.5 (Cq), 137.3 (C4'),
138.7 (C6'), 140.7 (C2'), 140.8 (Cq), 146.2 (Cq), 147.8 (C8'),
158.2 (C6), 158.6 (C4), 159.3 (C2) ppm; ms (ESI, m/z, %): 518
(M+, 100). Anal. Calcd. for C39H36ClNO4: C, 75.78; H, 5.87; N,
2.27. Found: C, 75.86; H, 5.66; N, 2.32.
d6): ꢁ 28.10 (Az-Me(6')), 28.29 (Az-Me(8')), 29.71 (Az-Me(4')),
116.0 (C3), 120.2 (C5), 127.2 (C2", C6"), 127.3 (C2"', C6"'),
128.7 (CH), 128.9 (CH), 129.0 (C5'), 129.1 (CH), 129.2 (CH),
129.3 (C7'), 131.5 (Cq), 131.8 (Cq), 137.8 (C2'), 138.3 (Cq),
138.8 (Cq), 147.6 (C8'), 148.5 (C4'), 148.7 (C6'), 149.2 (C4),
156.8 (C6), 159.7 (C2) ppm; ms (ESI): 400 (M++1, 100%). Anal.
Calcd. for C30H25N: C, 90.19; H, 6.31; N 3.51, found C, 90.14;
H, 6.36; N 3.51.
2-(5-Isopropyl-3,8-dimethyl-azulen-1-yl)-4,6-diphenyl-pyr-
idine, 11. Viscous dark brown oil (green in solution); uv
(MeOH), ꢀmax (log ꢁ): 217 (4.26), 253 (4.49), 305 (4.16), 372
(3.70), 379 (3.70); 1H nmr (CDCl3): ꢁ 1.49 (d, J = 6.8 Hz, 6H,
Me2CH), 2.60 (s, 3H, Me(3')), 2.69 (s, 3H, Me(8')), 3.11 (heptet,
J = 6.8 Hz, 1H, Me2CH), 7.04 (d, J = 10.8 Hz, 2H, 7'-H), 7.37-
7.55 (m, 7H, 6'-H, 3"-H, 4"-H, 5"-H, 3"'-H, 4"'-H, 5"'-H), 7.66
(d, J = 1.2 Hz, 1H, 5-H), 7.76 (d, J = 8.0 Hz, 2H, 2"-H, 6"-H),
7.83 (s, 1H, 2'-H), 7.88 (d, J = 1.2 Hz, 1H, 3-H), 8.18 (d, J = 8.0
Hz, 2H, 2"'-H, 6"'-H), 8.25 (d, J = 1.4 Hz, 1H, 4'-H) ppm; 13
C
nmr (CDCl3): ꢁ 12.90 (Az-Me(3')), 24.67 (Me2CH), 28.17 (Az-
Me(8')), 37.93 (Me2CH), 115.4 (C3), 122.2 (C5), 124.4 (CH),
127.0 (Cq), 127.1 (C2", C6"), 127.2 (C2"', C6"'), 127.6 (C7'),
128.6 (CH), 128.8 (CH), 128.9 (CH), 129.1 (CH)), 132.7 (Cq),
135.0 (C6'), 138.7 (Cq), 138.9 (Cq), 140.2 (Cq), 140.5 (C2'),
140.7 (C5'), 148.1 (C4'), 148.2 (C8'), 148.4 (C4), 156.4 (C6),
159.8 (C2) ppm; ms (ESI): 428 (M++1, 100%). Anal. Calcd. for
C32H29N: C, 89.89; H, 6.84; N 3.28, found C, 89.85; H, 6.86; N
3.29.
2-(5-Isopropyl-3,8-dimethyl-azulen-1-yl)-1,4,6-triphenyl-
pyridinium perchlorate, 8Ph. Brown crystals, mp 122 °C; uv
(MeOH), ꢀmax (log ꢁ): 218 (4.40), 255 (4.36), 285 (4.44), 342
1
(3.70), 472 (3.55); H nmr (acetone-d6): ꢁ 1.38 (d, J = 6.8 Hz,
6H, Me2CH), 2.48 (s, 3H, Me(8')), 2.83 (s, 3H, Me(3')), 3.27-
3.39 (m, 1H, Me2CH), 7.40 (m, 5H, Ph(4)), 7.41 (d, J = 10.4 Hz,
2H, 7'-H), 7.76 (t, J = 6.8 Hz, 1H, 4"-H), 7.71 (t, J = 6.8 Hz, 2H,
3"'-H, 5"'-H), 7.71 (t, J = 6.8 Hz, 1H, 4"'-H), 7.62-7.72 (m, 3H,
3"-H, 4"-H, 5"-H), 7.62 (dd, J =6.8, 2.0 Hz, 2H, 2"-H, 6"-H),
7.74 (dd, J = 10.8, 2.0 Hz, 1H, 6'-H), 8.14 (s, 1H, 2'-H), 8.31
(dd, J = 8.0, 1.6 Hz, 2H, 2"'-H, 6"'-H), 8.33 (d, J = 2.4 Hz, 1H,
4'-H), 8.57 (dAB, J = 2.0 Hz, 1H, 5-H), 8.60 (dAB, J = 2.4 Hz, 1H,
3-H); ms (ESI, m/z, %): 504 (M+, 100) [17]. Anal. Calcd. for
C38H34ClNO4: C, 75.55; H, 5.67; N, 2.32. Found: C, 75.48; H,
5.78; N, 2.28.
Acknowledgements. The A. C. R. is indebted to Prof. Klaus
Hafner for his thoughtful discussion and comments on this work
during the author stage in Darmstadt at the Technical University
in May 2007. The support of this research by the Ministry of
Education and Research, Romania, (CEx 05–D11–20
/05.10.2005) is gratefully acknowledged.
REFERENCES
2-(Azulen-1-yl)-4,6-diphenyl-pyridine, 9: blue crystals, mp
131 °C; uv (MeOH), ꢀmax (log ꢁ): 217 (4.26), 246 (4.40), 305
(4.30), 373 (3.92), 378 (3.93); 1H nmr (CDCl3): ꢁ 7.29 (t, J = 9.6
Hz, 1H, 5'-H), 7.43 (t, J = 9.6 Hz, 1H, 7'-H), 7.51 (d, J = 4.0 Hz,
1H, 3'-H), 7.43-7.63 (m, 7H, 3'-H, 3"-H, 4"-H, 5"-H, 3"'-H, 4"'-
H, 5"'-H), 7.73 (t, J = 9.8 Hz, 1H, 6'-H), 7.83 (d, J = 8.0 Hz, 2H,
2"'-H, 6"'-H), 7.89 (s, 1H, 5-H), 7.97 (s, 1H, 3-H), 8.31 (d, J =
7.6 Hz, 2H, 2"-H, 6"-H), 8.45 (d, J = 4.8 Hz, 1H, 2'-H), 8.44 (d,
J = 10.0 Hz, 1H, 4'-H), 9.96 (d, J = 10.0 Hz, 1H, 8'-H) ppm; 13C
nmr (CDCl3): ꢁ 115.3 (C3), 117.9 (CH), 119.6 (C5), 124.2 (C5'),
125.2 (C7'), 127.0 (C2", C6"), 127.1 (C2"', C6"'), 128.1 (Cq),
128.7 (CH), 128.8 (CH), 129.0 (CH), 136.6 (C´q), 137.0 (C2'),
137.5 (C4'), 138.2 (C8'), 138.6 (C6'), 139.3 (Cq), 140.0 (Cq),
143.4 (Cq), 149.7 (C4), 156.8 (C2), 157.2 (C6) ppm; ms (ESI):
358 (M++1, 100%). Anal. Calcd for C27H19N: C, 90.72; H, 5.36;
N 3.92. Found C, 90.64; H, 5.40; N 3.94.
[1] Razus A. C., Birzan L., Pavel C., Lehadus O., Corbu A.,
Enache C. J. Heterocyclic Chem. 2006, 43, 963.
[2] (a) Razus A. C., Birzan L., Pavel C., Lehadus O., Corbu A.,
Chiraleu F., Enache C., J. Heterocyclic Chem. 2007, 44, 251. (b) Razus
A. C., Birzan L., Pavel C., Lehadus O., Corbu A., Chiraleu F., Enache
C., J. Heterocyclic Chem. 2007, 44, 245.
[3] (a) Roussel C., Balaban A.T., Berg U., Chanon M., Gallo R.,
Sanders P., Tetrahedron 1983, 39, and the reference therein. (b)
Ghiviriga I., Czerwinski E. W., Balaban A. T., Croatica Chim. Acta
2004, 77, 391, and the reference therein.
[4] Shoji T., Kikuchi S., Ito S., Morita N., Heterocycles 2005,
66, 91-4. Crombie A. L., Kane J. L., Shea K. M., Danheiser R. L., J.
Org. Chem. 2004, 69, 8652-67. Salman H., Abraham Y., Tal S.,
Meltzman S., Kapou M., Tessler N., Speiser S., Eichen Y., Eur, J.
Org. Chem. 2005, 2207-12. Wakabayashi S., Kato Y., Mochizuki K.,
Suzuki R., Matsumoto M., Sugihara Y., Shimizu M., J. Org. Chem.
2006, 744-9.
2,4-Diphenyl-6-(4,6,8-trimethyl-azulen-1-yl)-pyridine, 10.
Viscous dark brown oil (violet in solution). uv (MeOH), ꢀmax
(log ꢁ): 217 (4.26), 227 (4.49), 299 (4.23), 372 (3.57), 378
[5] The 4,6-diphenyl-2-pyranone is not commercially available
therefore we have obtained these compounds by treating methyl
benzoylacetate with sulfuric acid at room temperature for 2 weeks.
Arndt F., Eistert B., Chem. Ber. 1925, 58, 2318.
[6] The MOPAC 7.0 package and AM1 approach were used; key
words: PULAY GNORM = 0.01 SHIFT = 50 GEO-OK CAMP-KING
CHARGE = 1.
[7] Krivun and Porshnev reported that 2-chloropyranylium salts
are unstable at the handle: Krivun S. V., Baranov S. N., Buryiak A. I.,
Andronova N. A., Misin V. M. Tserkashin M. I., Dokl. Akad. Nauk
SSSR, ser. Khim., 1981, 256, 881.
1
(3.54); H nmr (CDCl3): ꢁ 2.63 (s, 3H, Me(6')), 2.64 (s, 3H,
Me(4')), 2.94 (s, 3H, Me(8')), 7.08 (s, 1H, 5'-H), 7.12 (s, 1H, 7'-
H), 7.40 (d, J = 4.0 Hz, 1H, 3'-H) 7.42 (t, J = 6.8 Hz, 1H, 4"'-H),
7.46-7.48 (m, 5H, 3"-H, 4"-H, 5"-H, 3"'-H, 5"'-H), 7.68 (d, J =
1.2 Hz, 1H, 5-H ), 7.77 (dt, J = 8.0, 1.2 Hz, 2H, 2"-H, 6"-H),
7.82 (d, J = 4.0 Hz, 1H, 2'-H),7.89 (d, J = 1.2 Hz, 1H, 3-H), 8.16
(dt, J = 8.0, 1.2 Hz, 2H, 2"'-H, 6"'-H) ppm; 13C nmr (acetone-

Jul-Aug 2008
2-(Azulen-1-yl)-4,6-Diphenyl Substituted Six-Membered Heteroaromatics
1147
[8] Some reaction of 4,6-diphenyl-2-pyranone with nucleophile
[12] Multiplicity of protons belonging to (CH2)ꢀ group is good
resolved mainly for the compound 8nBu.
[13] Jennings W. B., Chem. Rev. 1975, 75, 307.
reagents in the presence of mixture of POCl3 and PCl5 or only in excess
of POCl3 were reported: Wizinger R., Grune A., Jacobi E., Helv. Chim.
Acta, 1956, 39, 1. Krivun S. V, Buryak A. I., Baranov S. N., Khim.
Geterotsikl. Soedin., 1973, 1199.
[9] The results obtained using MOPAC 7.0/AM1 are convergent
mainly for neutral pyridines. The presence of azulene moiety in the salt
cation produced some trouble in the reproducibility of calculation
results. Therefore, the order of the calculated values reflects better the
reality than the absolute obtained values.
[14] A careful study about the correlation between the recording
temperature and the ꢁꢀH of diastereotopic protons is in progress. Our
preliminary data show that the temperature of chemical shifts coalescence
for the pyridinium salts is placed between 60° C and 70° C (in DMSO-d6).
[15] Correct attribution for 13C chemical shifts was hindered by
the close values of aromatic signals both in 1H- and 13C-NMR spectra.
[16] The correct signal attributions for all 13C failed due to the
small solubility of salts in NMR solvents.
[10] The effect on band B is not so obvious.
[11] Rasala D., Bak T., Kolehmainen E., Styrcz S., Gawinecki R.,
J. Phys. Org. Chem. 1996, 9, 631 and ref. therein.
[17] The small amount of obtained compound hindered the 13
nmr recording.
C