High Stabilities of Di(1-azulenyl)(4-hydroxyphenyl)methyl Hexafluorophosphates and Polarized Properties of α,α-Di(1-azulenyl)-1,4-benzoquinone Methides

Article abstract of DOI:10.1021/jo961820q

Acid-catalyzed condensation of azulenes 8a-c with 4-hydroxy- and 3,5-di-tert-butyl-4-hydroxy-benzaldehyde leads to substituted di(1-azulenyl)(4-hydroxy- and 3,5-di-tert-butyl-4-hydroxyphenyl)-methanes 7a-f, which are easily converted into substituted di(1-azulenyl)(4-hydroxy- and 3,5-di-tert-butyl-4-hydroxyphenyl)methyl cations 5a-f by oxidation with DDQ. The spectroscopic data are consistent with the protonated cationic structures of 5a-f. The electrochemical reduction of 5a-f showed a reversible wave at -0.74 to -0.86 V (V vs Ag/Ag⁺) upon cyclic voltammetry (CV), although 5d and 5e showed an irreversible wave at -0.79 V. The relatively high reduction potentials of 5a-f, compared with those of di(1-azulenyl)phenylmethyl cations 2a-c, exhibit the stabilization by 4-hydroxy substituents on the phenyl groups. These salts (5a-f·PF₆^-) bearing 4-hydroxyl groups on the phenyl rings have been converted by treatment with bases to α,α-di(1-azulenyl)-1,4-benzoquinone methides 6a-f, which revert to 5a-f·PF₆^- upon reprotonation with HPF₆. These quinone methides (6a-f) are highly polarized by the extreme-electrodonating properties of 1-azulenyl groups. The highly polarized properties of 6a-f reflected to the high pK_a values of their conjugate acids (5a-c, 6.5-7.1, and 5d-f, 3.4-3.8). The strong solvatochromic effects also provide strong evidence of a large contribution of dipolar forms (6′) in the ground state. The relatively low oxidation potentials of 6a-f (+0.35 to +0.47 V vs Ag/Ag⁺) reflected facile formation of phenoxy radical cations, stabilized by two 1-azulenyl groups.

Full text of DOI:10.1021/jo961820q

J . Org. Chem. 1997, 62, 2423-2431
2423
High Sta bilities of Di(1-a zu len yl)(4-h yd r oxyp h en yl)m eth yl
Hexa flu or op h osp h a tes a n d P ola r ized P r op er ties of
r,r-Di(1-a zu len yl)-1,4-ben zoqu in on e Meth id es
Shunji Ito,* Shigeru Kikuchi, Hiroki Kobayashi, Noboru Morita, and Toyonobu Asao*,†
Department of Chemistry, Faculty of Science, Tohoku University, Kawauchi, Aoba-ku,
Sendai 980-77, J apan, and Faculty of Education, Iwate University, Ueda, Morioka 020, J apan
Received September 24, 1996X
Acid-catalyzed condensation of azulenes 8a -c with 4-hydroxy- and 3,5-di-tert-butyl-4-hydroxy-
benzaldehyde leads to substituted di(1-azulenyl)(4-hydroxy- and 3,5-di-tert-butyl-4-hydroxyphenyl)-
methanes 7a - f, which are easily converted into substituted di(1-azulenyl)(4-hydroxy- and 3,5-di-
tert-butyl-4-hydroxyphenyl)methyl cations 5a -f by oxidation with DDQ. The spectroscopic data
are consistent with the protonated cationic structures of 5a -f. The electrochemical reduction of
5a -f showed a reversible wave at -0.74 to -0.86 V (V vs Ag/Ag+) upon cyclic voltammetry (CV),
although 5d and 5e showed an irreversible wave at -0.79 V. The relatively high reduction
potentials of 5a -f, compared with those of di(1-azulenyl)phenylmethyl cations 2a -c, exhibit the
stabilization by 4-hydroxy substituents on the phenyl groups. These salts (5a -f‚PF6-) bearing
4-hydroxyl groups on the phenyl rings have been converted by treatment with bases to R,R-di(1-
-
azulenyl)-1,4-benzoquinone methides 6a -f, which revert to 5a -f‚PF6 upon reprotonation with
HPF6. These quinone methides (6a -f) are highly polarized by the extreme-electrodonating
properties of 1-azulenyl groups. The highly polarized properties of 6a -f reflected to the high pKa
values of their conjugate acids (5a -c, 6.5-7.1, and 5d -f, 3.4-3.8). The strong solvatochromic
effects also provide strong evidence of a large contribution of dipolar forms (6′) in the ground state.
The relatively low oxidation potentials of 6a -f (+0.35 to +0.47 V vs Ag/Ag+) reflected facile
formation of phenoxy radical cations, stabilized by two 1-azulenyl groups.
Ch a r t 1
In tr od u ction
We have recently reported the synthesis and properties
of a series of azulene analogs of triphenylmethyl cation,
i.e., tri(1-azulenyl)methyl (1a ), di(1-azulenyl)phenyl-
methyl (2a ), and (1-azulenyl)diphenylmethyl (3a ) hexa-
fluorophosphate and their derivatives (e.g., 1b-c, 2b-
c, and 3b-c) (Chart 1).1 These cations showed extreme
stabilities with high pKR+ values (e.g., 1a , 11.3; 2a , 10.5;
and 3a , 3.0, respectively).1a-c,2 In particular, the methyl
cations, which were stabilized by three (1a -c) or two
(2a -c) azulene rings, exhibited extraordinary thermo-
dynamic stabilities. The high stabilities of these cations
are rationalized by the large π-conjugative effect of
1-azulenyl groups with the cationic carbon (e.g., 1′).
Thus, the relatively low stability of the cations 1a -c,
compared with the expectation based on the stabilities
of the cations 2a -c and 3a -c, is explained by the steric
* To whom correspondence should be addressed. Tel.: +81-196-21-
6550. Fax: +81-196-21-6560. E-mail: asao@msv.cc.iwate-u.ac.jp.
† Iwate University.
X Abstract published in Advance ACS Abstracts, March 15, 1997.
(1) (a) Ito, S.; Morita, N.; Asao, T. Tetrahedron Lett. 1991, 32, 773-
776. (b) Ito, S.; Morita, N.; Asao, T. Tetrahedron Lett. 1994, 35, 751-
754. (c) Ito, S.; Morita, N.; Asao, T. Bull. Chem. Soc. J pn. 1995, 68,
1409-1436. (d) Ito, S.; Morita, N.; Asao, T. Tetrahedron Lett. 1994,
35, 3723-3726. (e) Ito, S.; Morita, N.; Asao, T. Bull. Chem. Soc. J pn.
1995, 68, 2011-2016. (f) Ito, S.; Morita, N.; Asao, T. Bull. Chem. Soc.
J pn. 1995, 68, 2639-2648. (g) Ito, S.; Fujita, M.; Morita, N.; Asao, T.
Chem. Lett. 1995, 475-476. (h) Ito, S.; Fujita, M.; Morita, N.; Asao, T.
Bull. Chem. Soc. J pn. 1995, 68, 3611-3620. (i) Ito, S.; Kikuchi, S.;
Morita, N.; Asao, T. Chem. Lett. 1966, 175-176. (j) Asao, T.; Ito, S. J .
Synth. Org. Chem. 1996, 54, 2-14. (k) Ito, S.; Morita, N.; Asao, T. J .
Org. Chem. 1996, 61, 5077-5082. (l) Ito, S.; Kobayashi, H.; Kikuchi,
S.; Morita, N.; Asao, T. Bull. Chem. Soc. J pn. 1996, 69, 3225-3237.
effects among the three azulene rings. To enhance the
thermodynamic stabilities, the third azulene rings of
1a -c should be replaced with the less hindered substit-
uents. The higher stabilities of di(1-azulenyl)[4-(di-
methylamino)phenyl]methyl cations (4a -c)11 than 1a are
in accord with these postulations (Chart 2).3
In this paper, we report the stabilizing abilities of
4-hydroxyphenyl groups as extra stabilizing groups of di-
(1-azulenyl)methylium ions, i.e., di(1-azulenyl)(4-hy-
droxy- and 3,5-di-tert-butyl-4-hydroxyphenyl)methyl hexa-
fluorophosphates and their derivatives (5a-f‚PF6-) (Chart
+
(2) The KR scale is defined by the equilibrium constant for the
reaction R+ + 2H2O ) ROH + H3O+ of a carbocation and a water
+
+
molecule (KR ) [ROH][H3O+]/[R+]). The pKR scales stand for the
carbocation in aqueous solution. Thus, pKR ) -log KR+. The larger
+
pKR+ index indicates a smaller KR+ value and in turn a higher stability
of the carbocation.
S0022-3263(96)01820-8 CCC: $14.00 © 1997 American Chemical Society

2424 J . Org. Chem., Vol. 62, No. 8, 1997
Ito et al.
Ch a r t 2
Sch em e 1
groups, which stabilized the protonated forms of 6a -f
effectively by the large π-conjugative effect (Chart 3). In
this paper, we also report the preparation and the highly
polarized properties of 6a -f, which were characterized
by large solvatochromic effect, the high pKa values of
their conjugate acids, and their redox behaviors.
Ch a r t 3
Resu lts a n d Discu ssion
Syn th esis of th e Sa lts 5a -f‚P F 6-. The synthesis of
di(1-azulenyl)(4-hydroxy- and 3,5-di-tert-butyl-4-hydrox-
yphenyl)methyl cations 5a -f was accomplished by the
hydride abstraction from the appropriate di(1-azulenyl)-
(4-hydroxy- and 3,5-di-tert-butyl-4-hydroxyphenyl)meth-
anes 7a -f (Scheme 1). The reaction of azulenes 8a -c1a-c
with 4-hydroxy- and 3,5-di-tert-butyl-4-hydroxybenzal-
dehydes in a 4:1 mixture of acetic acid and dichlo-
romethane solution at room temperature for 48 h afforded
7a -f in 18-100% yields, together with diastereomeric
mixtures of 1,3-bis[(1-azulenyl)(4-hydroxy- and 3,5-di-
tert-butyl-4-hydroxyphenyl)methyl]azulenes (9a ,b, 16%,
and 9c,d , 32%), in the case of 8a (Table 1). The
diastereomeric mixture of 9a ,b was separable by column
chromatography on silica gel (9a , 7.7%, and 9b, 7.0%),
whereas that of 9c,d 8 was inseparable by silica gel and
by gel permeation chromatography (GPC). Acceleration
of the reaction by warming to 60 °C or using high
pressure (10 kbar), which gave satisfactory results for
the reaction of 8a -c with 4-(dimethylamino)benz-
aldehyde,1l decreased the yields of the desired 7a -f and
in some cases also afforded undesired byproducts (Chart
4) such as (3-methyl- and 3,6-di-tert-butyl-1-azulenyl)(4-
hydroxyphenyl)methanes (10a ,b) and R-(3,6-di-tert-butyl-
1-azulenyl)-3,5-di-tert-butyl-1,5-benzoquinone methide (11)
in considerable yields (Table 1). Hydride abstraction1 of
7a -f with DDQ in dichloromethane at room temperature
followed by the addition of a 60% aqueous HPF6 solution
3). Although the stabilizing abilities of the 4-hydrox-
yphenyl group should be lower than those of the 4-(di-
methylamino)phenyl group,5 the group will also stabilize
di(1-azulenyl)methylium ions owing to the mesomeric
effect of the 4-hydroxy substituent, effectively. The major
distinctions of these cations (5a -f) may be made as to
attain equilibrium with R,R-di(1-azulenyl)-1,4-benzo-
quinone methides 6a -f under basic conditions. Although
numerous substituted quinone methides have been de-
scribed in the literature,7 6a -f will be highly polarized
by the extreme-electrodonating properties of 1-azulenyl
-
yielded the salts 5a -f‚PF6 in 92-100% yield. These
-
new salts 5a -f‚PF6 were stable deep blue crystals in
solution.
Sch em e 2
(3) Since the pKR+ value of tri(1-azulenyl)methyl cation (1a ) is fairly
+
larger than that of tris[4-(dimethylamino)phenyl]methyl cation (pKR
9.36),4 the stabilizing ability of 4-(dimethylamino)phenyl groups must
be considerably lower than that of 1-azulenyl groups. However, the
pKR values of 4a were higher than that of 1a . This is in accord with
+
these postulations.
(4) (a) Goldacre, R. J .; Phillips, J . N. J . Chem. Soc. 1949, 1724-
1732. (b) Deno, N. C.; Schriesheim, A. J . Am. Chem. Soc. 1955, 77,
3051-3054.
-
Sp ectr oscop ic P r op er ties of th e Sa lts 5a -f‚P F 6
.
-
High-resolution mass spectra of 5a -f‚PF6 ionized by
(5) The hydroxyl substituents stabilize carbocations to a considerable
extent, e.g., the pKR+ value of tris(4-hydoxyphenyl)methyl cation (pKR
+
1.97) is fairly larger than that of triphenylmethyl cation (pKR+ -6.44):6
Deno, N. C.; Evans, W. L. J . Am. Chem. Soc. 1957, 79, 5804-5807.
(6) Arnett, E. M.; Busshick, R. D. J . Am. Chem. Soc. 1964, 86, 1564-
1571.
(7) See, e.g.: (a) Zanarotti, A. Tetrahedron Lett. 1982, 23, 3815-
3818. (b) Becker, H.-D. J . Org. Chem. 1967, 32, 2943-2947.
(8) The diastereomeric ratio of 9c:9d was 5:3, which was determined
by the 1H NMR spectrum.

Di(1-azulenyl)(4-hydroxyphenyl)methyl Cations
J . Org. Chem., Vol. 62, No. 8, 1997 2425
Ta ble 1. Acid -Ca ta lyzed Con d en sa tion of 8a -c w ith 4-Hyd r oxy- a n d 3,5-Di-ter t-bu tyl-4-h yd r oxyben za ld eh yd e
azulene 8a -c
aldehyde
mmol
recovered
azulene (%)
yieldb (%)
entry
R1
R2
mmol
R
condnsa
1
2
3
4
5
6
7
8
9
10
11
12
13
14
H
H
10
10
5
5
5
5
5
10
10
5
H
5
2.5
5
2.6
5
2.6
5
5
2.5
5
2.6
5
2.6
5
A
B
A
B
A
B
C
A
B
A
B
A
B
C
18 (7a )
2.0 (7a )
96 (7b)
27 (7b)
85 (7c)
56 (7c)
60 (7c)
34 (7d )
15 (7d )
100 (7e)
60 (7e)
80 (7d )
57 (7d )
39 (7d )
7.7 (9a )
7.0 (9b)
(27)
(16)
(1.8)
Me
H
H
H
12 (10a )
t-Bu
t-Bu
(14)
5.8 (10b)
32 (9c,d )
16 (9c,d )
H
H
t-Bu
t-Bu
t-Bu
(49)
(42)
(21)
(7.6)
Me
t-Bu
H
5
5
5
5
t-Bu
(48)
27 (11)
a
Conditions A: at room temperature for 48 h in acetic acid/dichloromethane (4:1). Conditions B: at 10 kbar, 30 °C for 24 h in acetic
b
acid/dichloromethane (1:1). Conditions C: at 60 °C for 24 h in acetic acid/dichloromethane (4:1). Isolated yields based on azulenes
8a -c reacted.
Ch a r t 4
F igu r e 1. UV-vis spectra of cation 5a (solid line) and cation
2a (broken line) in acetonitrile.
Ta ble 2. p KR Va lu es a n d Red ox P oten tia lsa of th e
+
Ca tion s 5a -f, 1a -c, a n d 2a -c1c
+
red
red
ox
ox
pKR
E1
E2
E1
E2
5a
5b
5c
5d
5e
5f
-0.74
(-0.79)
-0.85
(-1.62)
(+1.02)
(+0.89)
+0.87
(+0.98)
(+0.90)
(+0.92)
FAB showed the correct M+ - PF6 ion peaks, which
indicated the ionic structure of these products. The
(-1.76)
(-1.50)
(+1.33)
-
characteristic bands for the counter ion PF6 were
-0.74
observed at 841-843 (strong) and 558 (medium) cm-1 in
their IR spectra, which also supported the ionic structure
of these compounds (5a -f‚PF6-).1 UV-vis spectra of 5a
in acetonitrile along with those of the related phenyl
analogs 2a was shown in Figure 1. The strong absorp-
tions of 5a -f in the visible region exhibited a hypsochro-
mic shift by 15-19 nm, compared with those of 2a -c.1c
The 1H NMR chemical shift of the methine protons of
7a -f was slightly upfield compared with those of di(1-
azulenyl)phenylmethane and its related derivatives. The
signals disappeared on the 1H NMR spectra of 5a -f.
Thus, the 1H NMR spectra also indicated a ionic structure
of these compounds. These results are in accordance with
the spectroscopic properties of di(1-azulenyl)[4-(dimethyl-
amino)phenyl]methyl cations 4a -c. The spectroscopic
properties exhibited the protonated ionic structures of
quinone methides 6a -f.
(-0.79)
-0.86
(-1.69)
1a
1b
1c
11.3
11.4
14.3
-0.78
-0.82
-0.91
(-1.56)
(-1.59)
(-1.72)
(+0.98)
(+0.85)
+0.84
(+1.07)
(+0.94)
+0.95
2a
2b
2c
10.5
10.8
12.4
-0.66
-0.77
-0.78
(-1.52)
(-1.57)
(-1.64)
(+1.04)
(+0.90)
+0.88
(+1.38)
a
The redox potentials were measured by cyclic voltammetry
(V vs Ag/Ag+, 0.1 M Et4NClO4 in acetonitrile, Pt electrode, and
scan rate 100 mV s-1). In the case of irreversible waves, which
are shown in parentheses, Eox and Ered were calculated as Epa
(anodic peak potential) -0.03 and Epc (cathodic peak potential)
+0.03 V, respectively.
potentials (V vs Ag/Ag+) are measured by cyclic voltam-
metry (CV). The redox potentials of 5a -f and those of
the comparative compounds 1a -c and 2a -c are sum-
marized in Table 2.1c The redox behavior of 5a -f is
almost identical to the behavior of the phenyl analogs
Red ox P r op er ties of th e Ca tion s 5a -f. As a
criterion of high stabilities of the cations 5a -f, the redox

2426 J . Org. Chem., Vol. 62, No. 8, 1997
Ito et al.
Ta ble 3. p Ka Va lu esa of th e P r oton a ted Ca tion s 5a -f
Sch em e 3
a n d Red ox P oten tia lsb of th e Qu in on e Meth id es 6a -f
red
red
ox
ox
pKa
E1
E2
E1
E2
5a
5b
5c
5d
5e
5f
6.5
7.1
7.0
3.4
3.7
3.8
6a
6b
6c
6d
6e
6f
-1.38
-1.39
(-1.75)
(-1.80)
(-1.93)
(+0.45)
(+0.41)
(+0.36)
+0.47
-1.41
(-1.55)
(-1.56)
-1.57
(+0.95)
(+0.72)
(+0.74)
+0.40
(-2.03)
+0.35
a
The pKa values were determined by spectrophotometrically
at 25 °C in a buffered solution prepared in 50% aqueous acetoni-
b
trile. Determined as indicated in Table 2.
-
thides 6a -f. Neutralization of 5a -f‚PF6 with 5%
aqueous NaHCO3 solution afforded the quinone methides
6a -f in 78-92% yield (Scheme 2). All new quinone
methides 6a -f are stable crystalline compounds of dark
brown color. Protonation of 6a -f with HPF6 regenerated
the corresponding (4-hydroxyphenyl)methyl hexafluoro-
-
phosphates 5a -f‚PF6 in 92-100% yield.
p Ka Va lu es of th e Con ju ga te Acid s of th e Qu in on e
Meth id es 6a -f. The high pKa values of the conjugate
acids of 6a -f provide a criterion of high stabilities of the
protonated forms of 6a -f and of a large contribution of
polar canonical forms 6′. The pKa values of the conjugate
acids 5a -f were determined spectrophotometrically at
25 °C in a buffer solution prepared in 50% aqueous
acetonitrile.1c,10 The pKa values of 5a -f, particularly
those of 5a -c (pKa 6.5-7.1), are appreciably high (Table
3).11 The values exhibit that the protonation of 6a -c
causes in almost neutral conditions. This provides strong
evidence of a large contribution of dipolar forms (e.g., 6′)
of 6a -f in the ground state. The relatively low pKa
values for 5d -f, compared with those of 5a -c, indicate
the steric effects of the tert-butyl substituents on the six-
membered rings, which hinder the protonation of the
quinone methides 6a -f. As expected, the 3-methyl and
3,6-di-tert-butyl substituents on the azulene rings slightly
increase the pKa values by 0.3-0.6 pK units. The
protonation and the neutralization of these compounds
6a -f are approximately reversible. Neutralization of the
acidic solutions of 6a -f with NaOH regenerated the
absorptions of the quinone methides in the visible region
quantitatively.
Solva toch r om ic P r op er ties of th e Qu in on e Me-
th id es 6a -f. The large solvatochromic effects of 6a -c
also provides strong evidence of a large contribution of
dipolar forms (e.g., 6′) of 6a -f in the ground state,
although 6d -f showed rather weak solvatochromic ef-
fects for the steric reasons of the tert-butyl substituents
on the six-membered rings, which hinder the solvation
of the protic solvents as well as the protonation. Com-
pounds 6a -c form solutions that appear deep red in
dichloromethane but deep blue in methanol. The marked
2a -c, except for the enlargement of the reduction
potentials owing to the stabilization by the 4-hydroxyl
substituents. The reduction of 5a -f in acetonitrile
showed a reversible wave at -0.74 to -0.86 V and an
irreversible wave at -1.50 to -1.76 V upon the CV,
except for 5b and 5e, which showed an irreversible wave
at -0.79 V. These two waves are ascribed to the
formation of a radical and an anion species such as 12
and 13, respectively (Scheme 3). The more negative
reduction potentials of 5a -f compared to those of 2a -c
by 0.02-0.08 V indicate the stabilization of the methyl
cations by the 4-hydroxy substituent on the phenyl
groups. The most negative reduction potential of the tert-
butyl derivatives (5c, -0.85 V, and 5f, -0.86 V) among
these compounds corresponds to their high electrochemi-
cal stability. The potentials are comparable with those
of the tri(1-azulenyl)methyl cations 1a -c. Although the
thermodynamic stabilities (pKR+ values) of these cations
5a -f could not be determined due to the equilibrium with
the quinone methides 6a -f, the redox potentials of 5a -f
indicate that the 4-hydroxy substituents on the phenyl
groups stabilize the cations effectively by their mesomeric
effects. The high stabilities of 5a -f are attributable to
the high contribution of the azulenium ion structures (5′)
in addition to the electron-donating properties of the less
hindered 4-hydroxyphenyl groups.5
Although the oxidation of 4-(dimethylamino)phenyl
derivatives 4a -c exhibited voltammograms that were
characterized by a barely separated two-step oxidation
wave at +0.75 to +0.87 and +0.89 to +1.01 V,1l 5a -f
exhibited similar oxidation properties with those of the
corresponding phenyl derivatives 2a -c.1c The oxidation
potentials of 5a -f were also comparable with those of
2a -c. The oxidation of 5a -f showed a wave at +0.87 to
+1.02 V, which is ascribed to the oxidation of an azulene
ring to give dication radical species such as 14 (Scheme
3). The tert-butyl substituents on the azulene rings also
stabilize the oxidation states of these cations, as indicated
by the oxidation of 5c. The oxidation of 5c exhibited an
(9) The electrochemical oxidation of di(1-azuenyl)[4-(dimethylami-
no)phenyl]methyl cations 4a -c exhibited voltammograms that were
characterized by a barely separated two-step oxidation wave at +0.75
to +0.87 and +0.87 to +1.01 V. This provides the strong evidence of
the contribution of dimethyl(4-methylidene-2,5-cyclohexadien-1-ylide-
ne)ammonium structures for 4a -c, which faciliated the oxidation of
the two azulene rings.1l
ox
irreversible E2 wave at +1.33 V, which is in the
potential range comparable with those of 2c. The oxida-
tion properties of 5a -f did not show any evidence of the
contribution of (4-methylidene-2,5-cyclohexadien-1-ylide-
ne)oxonium structures.9
Neu tr a liza tion of th e Sa lts 5a -f‚P F 6-. These salts
5a -f‚PF6- cause a deprotonation upon a treatment with
bases, forming R,R-di(1-azulenyl)-1,4-benzoquinone me-
(10) The pKa values for 5a -f were determined in a similar manner
as the determination of the pKR+ values for carbocations: (a) Kerber,
R. C.; Hsu, H. M. J . Am. Chem. Soc. 1973, 95, 3239-3245. (b) Komatsu,
K.; Masumoto, K.; Waki, Y.; Okamoto, K. Bull. Chem. Soc. J pn. 1982,
55, 2470-2479.
(11) The pKa values for the conjugate acid of the majority of carbonyl
compounds lie between 0 and -10. For example, the pKa value for the
protonation of acetone is reported as -7.2: Arnett, E. M. Progr. Phys.
Org. Chem. 1963, 1, 223-403.

Di(1-azulenyl)(4-hydroxyphenyl)methyl Cations
J . Org. Chem., Vol. 62, No. 8, 1997 2427
Sch em e 4
F igu r e 2. UV-vis spectra of the quinone methide 6a in
dichloromethane (solid line) and in methanol (broken line).
wave at -1.38 to -1.57 V and an irreversible wave at
-1.75 to -2.03 V upon the CV, except for 6d and 6e,
which showed an irreversible wave at -1.55 to -1.56 V.
These two waves are ascribed to the formation of a
radical and an anion species such as 15 and 16, respec-
tively (Scheme 4). The more negative reduction poten-
tials of 6d -f than those of 6a -c by about 0.2 V
corresponds to the high electrochemical stabilization by
the 3′,5′-di-tert-butyl substituents on their phenyl groups.
The reduction potentials for 6a -f are affected little by
the substituents on their azulene rings.
Ta ble 4. Solva toch r om ic Da ta for th e Lon gest
Wa velen gth Absor p tion of 6a -f
CH2Cl2
max, nm
MeOH
max, nm
λ
log ꢀ
λ
log ꢀ
6a
6b
6c
6d
6e
6f
522
534
537
507
523
534
(4.43)
(4.49)
(4.50)
(4.42)
(4.43)
(4.46)
549
594
599
521
529
536
(4.55)
(4.57)
(4.47)
(4.45)
(4.47)
(4.26)
solvent dependence of the electronic spectra of 6a -f is
illustrated by the data in Table 4, showing the absorption
maxima for the lowest-energy electronic transition, and
by the spectra of 6a in Figure 2. The strong absorption
of 6a -c in the visible region exhibited an appreciable
bathochromic shift by 27, 60, and 62 nm, respectively,
on changing the solvent from dichloromethane to metha-
nol. In contrast to the large solvatochromic effects of 6a -
c, the longest wavelength absorption of 6d -f showed a
slight bathochromic shift within 2-14 nm on changing
the solvents. The solvatochromic effects of 6a -c can be
rationalized by the stabilization of the excited state by
the hydrogen bonding of the quinone methides with the
protic solvents. The tert-butyl substituents on the six
membered rings of 6d -f hinder the solvation of the
quinone methides with the polar solvents. This reflects
the rather weak solvatochromic effects of 6d -f. In
conclusion, the charge-separated ionic forms (6′) with “di-
(1-azulenyl)methylium ion” character make a remarkable
contribution to the resonance hybrid for the ground
state.12
Red ox P r op er ties of th e Qu in on e Meth id es 6a -
f. The redox potentials (V vs Ag/Ag+) of 6a -f measured
by CV in dimethylformamide (DMF) are summarized in
Table 3. The redox potentials of 6a -f were apparently
distinct from those of 5a -f, as expected. The redox
properties of 6a -f can be characterized by rather high
reduction potentials and by rather low oxidation poten-
tials, compared with those of their conjugate acids 5a -
f. The reduction of 6a -f in DMF showed a reversible
The oxidation of 6a -f showed a wave at +0.35 to +0.47
V, which corresponds to the oxidation of the quinone
methide moieties to form phenoxy radical cations such
as 17 (Scheme 4). The reversibilities of the waves for
6d -f are due to the stabilization of the phenoxy radicals
by the adjacent 3′,5′-di-tert-butyl substituents on the
phenyl rings. The oxidation of 6d -f also exhibited an
ox
irreversible E2 wave at +0.72 to +0.95 V.
Con clu sion s. The stabilities of the cations 5a -f were
examined by the redox potentials measured by CV.
These cations (5a -f) exhibited high stabilities with high
reduction potentials, which were comparable with those
of the tri(1-azulenyl)methyl cations 1a -c. The high
stabilization of 5a -f by the 4-hydroxyphenyl groups is
attributable to the high contribution of the azulenium
ion structures (5′) in addition to the electron-donating
properties of the less hindered 4-hydroxyphenyl groups.5
The large solvatochromic effects of 6a -c provide strong
evidence of a large contribution of a dipolar form of 6a -c
in the ground state, although 6d -f showed little effect
due to the steric effect of the tert-butyl substituents on
the six-membered rings. The dipolar structures of the
quinone methides 6a -f also reflect the high pKa values
of their conjugate acids 5a -f owing to the contribution
of azulenium ion structures such as 6′. The high pKa
values for 5a -f are consistent with the high electro-
chemical stabilities of 5a -f. The relatively low oxidation
potentials for 6a -f, compared with those of 5a -f, which
correspond to the oxidation of the quinone methide
moieties to form phenoxy radical cations, reflect to facile
formation of phenoxy radical cations 17, stabilized by two
1-azulenyl groups.
(12) For interesting similar situations for solvatochromic effect of
diarylquinocyclopropenes see: (a) Wellman, D. E.; West, R. J . Am.
Chem. Soc. 1984, 106, 355-360. (b) West, W.; Zecher, D. C. J . Am.
Chem. Soc. 1970, 92, 155-161.

2428 J . Org. Chem., Vol. 62, No. 8, 1997
Ito et al.
(dd, J ) 9.8, 9.8 Hz, 2H), 6.872 (d, J ) 8.4 Hz, 4H), 6.601 (s,
2H), 6.574 (d, J ) 8.4 Hz, 4H), 4.694 (s, 2H); 13C NMR (150
MHz, CDCl3) δ 153.449 (s), 141.047 (s), 139.694 (d), 138.206
(d), 137.855 (s), 137.372 (d), 137.227 (d), 136.659 (d), 135.748
(s), 134.929 (s), 133.823 (d), 133.583 (d), 133.338 (s), 132.053
(s), 129.793 (d), 122.421 (d), 121.778 (d), 121.620 (d), 116.459
(d), 114.896 (d), 41.849 (d). Anal. Calcd for C44H32O2‚2H2O:
C, 84.05; H, 5.77. Found: C, 84.24; H, 5.43.
Exp er im en ta l Section
Gen er a l P r oced u r es. Melting points were determined on
a micro melting point apparatus and are uncorrected. Mass
spectra were usually obtained at 70 eV. 1H NMR spectra (13C
NMR spectra) were recorded at 90 MHz (22.5 MHz), at 400
MHz (100 MHz), and/or at 600 MHz (150 MHz). Voltammetry
measurements were carried out with an electrochemical
workstation equipped with Pt working and auxiliary elec-
trodes, and a reference electrode formed from Ag/AgNO3 (0.01
M) and tetraethylammonium perchlorate (TEAP) as a sup-
porting electrolyte, at the scan rate of 100 mV s-1. Elemental
analyses were performed at the Instrumental Analysis Center
of Chemistry, Faculty of Science, Tohoku University.
Gen er a l P r oced u r e for th e Rea ction of Azu len es 8a -c
w ith 4-Hyd r oxy- or 3,5-Di-ter t-bu tyl-4-h yd r oxyben za l-
d eh yd e a t Atm osp h er ic P r essu r e. A solution of the ap-
propriate azulenes 8a -c (5-10 mmol) and 4-hydroxy- or 3,5-
di-tert-butyl-4-hydroxybenzaldehyde (5 mmol) in a 4:1 mixture
of acetic acid and CH2Cl2 (50-100 mL) was stirred at room
temperature for 48 h or at 60 °C for 12 h under an Ar
atmosphere (Table 1). The solvent was removed in vacuo. The
residue was diluted with CH2Cl2. The organic layer was
washed with 5% aqueous NaHCO3 and water, dried with
MgSO4, and concentrated in vacuo. The residue was then
purified by column chromatography on silica gel and/or GPC
to afford the di(1-azulenyl)(4-hydroxy- and 3,5-di-tert-butyl-
4-hydroxyphenyl)methanes 7a -f. The product was further
purified by recrystallization.
Gen er a l P r oced u r e for th e High -P r essu r e Rea ction of
Azu len es 8a -c w ith 4-Hyd r oxyben za ld eh yd e or 3,5-Di-
ter t-bu tyl-4-h yd r oxyben za ld eh yd e. A solution of the ap-
propriate azulenes 8a -c (5 mmol) and 4-hydroxy- or 3,5-di-
tert-butyl-4-hydroxybenzaldehyde (2.5-2.6 mmol) in a 1:1
mixture of acetic acid and CH2Cl2 (3.7 mL) was pressurized
up to 10 kbar at 30 °C for 24 h (Table 1). The crude material
was then purified by column chromatography on silica gel and/
or GPC to afford the di(1-azulenyl)(4-hydroxy- and 3,5-di-tert-
butyl-4-hydroxyphenyl)methanes 7a -f.
Di(1-a zu len yl)(4-h yd r oxyp h en yl)m eth a n e (7a ). The
general procedure was followed using azulene 8a (1.28 g, 10.0
mmol) and 4-hydroxybenzaldehyde (612 mg, 5.01 mmol) at
room temperature for 48 h. Column chromatography on silica
gel with ethyl acetate/CH2Cl2 and GPC with CHCl3 afforded
the recovered 8a (348 mg, 27%), the methane 7a (241 mg,
18%), and a diastereomeric mixture of 1,3-bis[(1-azulenyl)(4-
hydroxyphenyl)methyl]azulene (9a and 9b) (236 mg, 16%),
which was separable by column chromatography on silica gel
with ethyl acetate/CH2Cl2 (9a : 110 mg, 7.7%; 9b: 101 mg,
7.0%). When the general procedure was followed using 8a
(1.28 g, 10.0 mmol) and the benzaldehyde (307 mg, 2.51 mmol)
in a 50% acetic acid solution of CH2Cl2 (9.1 mL) at 10 kbar for
24 h, column chromatography afforded the recovered 8a (207
mg, 16%) and the methane 7a (30 mg, 2.0%).
7a : blue prisms; mp 187.0-188.0 °C; MS (70 eV) m/z (rel
inten) 360 (M+, 100), 359 (37), 267 (27), 265 (40), 231 (38); ES
(CH2Cl2) λmax, nm (log ꢀ) 238 (4.58), 278 (4.87), 350 (4.02), 366
(3.93), 601 (2.83), 655 (2.74); 1H NMR (600 MHz, CDCl3) δ
8.271 (d, J ) 9.4 Hz, 2H), 8.248 (d, J ) 9.7 Hz, 2H), 7.501 (dd,
J ) 9.9, 9.7 Hz, 2H), 7.440 (d, J ) 3.9 Hz, 2H), 7.271 (d, J )
3.9 Hz, 2H), 7.075 (dd, J ) 9.7, 9.4 Hz, 2H), 7.008 (d, J ) 8.7
Hz, 2H), 6.986 (dd, J ) 9.9, 9.7 Hz, 2H), 6.692 (d, J ) 8.7 Hz,
2H), 6.685 (s, 1H), 4.773 (s, 1H); 13C NMR (150 MHz, CDCl3)
δ 153.608 (s), 141.023 (s), 138.241 (d), 138.065 (s), 137.331 (d),
136.713 (d), 134.913 (s), 133.683 (d), 133.558 (s), 129.889 (d),
122.485 (d), 121.924 (d), 116.552 (d), 115.045 (d), 41.932 (d).
Anal. Calcd for C27H20O: C, 89.97; H, 5.59. Found: C, 90.10;
H, 5.78.
9a (fa st elu a te): blue crystals; mp 168.0-172.0 °C; MS (70
eV) m/z (rel inten) 592 (M+, 1.6), 360 (25), 128 (100); ES (CH2-
Cl2) λmax, nm (log ꢀ) 239 (4.71), 281 (5.00), 346 (4.13), 366 (4.10),
604 (2.93); 1H NMR (600 MHz, CDCl3) δ 8.218 (d, J ) 9.7 Hz,
2H), 8.200 (d, J ) 9.8 Hz, 2H), 8.150 (d, J ) 9.8 Hz, 2H), 7.482
(dd, J ) 9.8, 9.8 Hz, 2H), 7.391 (t, J ) 9.8 Hz, 1H), 7.318 (d,
J ) 3.8 Hz, 2H), 7.189 (d, J ) 3.8 Hz, 2H), 7.120 (s, 1H), 7.047
(dd, J ) 9.8, 9.7 Hz, 2H), 6.930 (dd, J ) 9.8, 9.8 Hz, 2H), 6.877
9b (secon d elu a te): blue crystals; mp 158.0-160.0 °C; MS
(70 eV) m/z (rel inten) 592 (M+, 1.1), 360 (28), 128 (100); ES
(CH2Cl2) λmax, nm (log ꢀ) 239 (4.69), 281 (4.96), 350 (4.11), 365
1
(4.08), 605 (2.91); H NMR (600 MHz, CDCl3) δ 8.179 (d, J )
9.7 Hz, 2H), 8.163 (d, J ) 9.9 Hz, 2H), 8.139 (d, J ) 9.7 Hz,
2H), 7.439 (dd, J ) 9.9, 9.9 Hz, 2H), 7.356 (t, J ) 9.9 Hz, 1H),
7.275 (d, J ) 3.8 Hz, 2H), 7.140 (d, J ) 3.8 Hz, 2H), 7.050 (s,
1H), 7.014 (dd, J ) 9.9, 9.7 Hz, 2H), 6.885 (dd, J ) 9.9, 9.7
Hz, 2H), 6.881 (d, J ) 8.5 Hz, 4H), 6.841 (dd, J ) 9.9, 9.9 Hz,
2H), 6.585 (s and d, J ) 8.5 Hz, 6H), 5.061 (s, 2H); 13C NMR
(150 MHz, CDCl3) δ 153.351 (s), 140.978 (s), 139.715 (d),
138.198 (d), 137.910 (s), 137.365 (d), 137.236 (d), 136.623 (d),
135.721 (s), 134.857 (s), 133.753 (d), 133.629 (d), 133.216 (s),
132.137 (s), 129.797 (d), 122.402 (d), 121.799 (d), 121.608 (d),
116.371 (d), 114.951 (d), 41.863 (d). Anal. Calcd for C44H32O2‚
1/2H2O: C, 87.82; H, 5.53. Found: C, 88.17; H, 5.76.
Bis(3-m et h yl-1-a zu len yl)(4-h yd r oxyp h en yl)m et h a n e
(7b ). The general procedure was followed using 1-methyl-
azulene (8b) (719 mg, 5.06 mmol) and 4-hydroxybenzaldehyde
(611 mg, 5.00 mmol) at room temperature for 48 h. Column
chromatography on silica gel with CH2Cl2 afforded the recov-
ered 8b (13 mg, 1.8%) and the methane 7b (923 mg, 96%).
When the general procedure was followed using 8b (712 mg,
5.01 mmol) and the benzaldehyde (318 mg, 2.60 mmol) in a
50% acetic acid solution of CH2Cl2 (3.7 mL) at 10 kbar for 24
h, column chromatography on silica gel with CH2Cl2 and GPC
with CHCl3 afforded the methane 7b (264 mg, 27%) and (3-
methyl-1-azulenyl)(4-hydroxyphenyl)methane (10a ) (78 mg,
12%).
7b: blue crystals; mp 179.0-181.0 °C; MS (70 eV) m/z (rel
inten) 388 (M+, 100), 373 (39), 279 (23), 245 (20), 231 (31); ES
(CH2Cl2) λmax, nm (log ꢀ) 241 (4.50), 281 (4.84), 357 (3.98), 374
1
(3.96), 631 (2.84); H NMR (90 MHz, CDCl3) δ 8.11 (d and d,
J ) 9.5 Hz, 4H), 7.40 (dd, J ) 10.6, 9.7 Hz, 2H), 7.28 (s, 2H),
6.98 (d, J ) 8.8 Hz, 2H), 6.93 (dd, J ) 9.7, 9.5 Hz, 2H), 6.82
(dd, J ) 10.6, 9.5 Hz, 2H), 6.66 (d, J ) 8.8 Hz, 2H), 6.61 (s,
1H), 4.60 (br, 1H), 2.55 (s, 6H); 13C NMR (22.5 MHz, CDCl3) δ
153.44 (s), 139.29 (d), 138.19 (s), 137.13 (d), 136.94 (s), 134.99
(s), 133.47 (d), 132.98 (d), 131.91 (s), 129.78 (d), 124.47 (s),
120.94 (d), 120.66 (d), 114.99 (d), 41.54 (d), 12.73 (q). Anal.
Calcd for C29H24O: C, 89.65; H, 6.23. Found: C, 89.29; H, 6.34.
10a : blue needles; mp 96.0-97.5 °C; MS (70 eV) m/z (rel
inten) 248 (M+, 100), 247 (23), 233 (77), 155 (35); ES (CH2Cl2)
λmax, nm (log ꢀ) 240 (4.24), 286 (4.68), 354 (3.71), 371 (3.60),
629 (2.52); 1H NMR (400 MHz, CDCl3) δ 8.153 (d, J ) 9.5 Hz,
1H), 8.112 (d, J ) 9.5 Hz, 1H), 7.508 (s, 1H), 7.435 (dd, J )
9.8, 9.8 Hz, 1H), 7.030 (d, J ) 8.3 Hz, 2H), 6.952 (dd, J ) 9.8,
9.5 Hz, 1H), 6.922 (dd, J ) 9.8, 9.5 Hz, 1H), 6.692 (d, J ) 8.3
Hz, 2H), 4.972 (s, 1H), 4.306 (s, 2H), 2.599 (s, 3H); 13C NMR
(100 MHz, CDCl3) δ 153.55 (s), 138.95 (d), 137.34 (d), 136.80
(s), 135.83 (s), 134.16 (s), 133.38 (d), 132.97 (d), 129.62 (d),
127.95 (s), 124.86 (s), 120.76 (d), 120.61 (d), 115.17 (d), 32.48
(t), 12.55 (q). Anal. Calcd for C18H16O: C, 87.06; H, 6.50.
Found: C, 86.90; H, 6.72.
Bis(3,6-d i-t er t -b u t yl-1-a zu le n yl)(4-h yd r oxyp h e n yl)-
m eth a n e (7c). The general procedure was followed using 1,6-
di-tert-butylazulene (8c) (1.20 g, 5.00 mmol) and 4-hydroxy-
benzaldehyde (612 mg, 5.01 mmol) at room temperature for
48 h. Column chromatography on silica gel with CH2Cl2
afforded the methane 7c (1.24 g, 85%). When the general
procedure was followed using 8c (1.20 g, 5.00 mmol) and the
benzaldehyde (612 mg, 5.01 mmol) at 60 °C for 12 h, column
chromatography on silica gel with CH2Cl2 and GPC with
CHCl3 afforded the methane 7c (884 mg, 60%) and (3,6-di-
tert-butyl-1-azulenyl)(4-hydroxyphenyl)methane (10b ) (100
mg, 5.8%). When the general procedure was followed using
8c (1.20 g, 5.01 mmol) and the benzaldehyde (318 mg, 2.60
mmol) in a 50% acetic acid solution of CH2Cl2 (3.7 mL) at 10

Di(1-azulenyl)(4-hydroxyphenyl)methyl Cations
J . Org. Chem., Vol. 62, No. 8, 1997 2429
kbar for 24 h, column chromatography on silica gel with ethyl
acetate/CH2Cl2 afforded the recovered 8c (174 mg, 14%) and
the methane 7c (708 mg, 56%).
δ 8.241 (d, J ) 9.7 Hz, 2H), 8.203 (d, J ) 9.6 Hz, 2H), 8.143
(d, J ) 9.4 Hz, 2H), 7.477 (dd, J ) 9.8, 9.8 Hz, 2H), 7.341 (t,
J ) 9.8 Hz, 1H), 7.317 (d, J ) 3.8 Hz, 2H), 7.181 (s, 1H), 7.178
(d, J ) 3.8 Hz, 2H), 7.032 (dd, J ) 9.8, 9.6 Hz, 2H), 6.944 (dd,
J ) 9.8, 9.7 Hz, 2H), 6.935 (s, 2H), 6.849 (s, 2H), 6.815 (dd, J
) 9.8, 9.4 Hz, 2H), 6.552 (s, 2H), 4.949 (s, 1H), 1.240 (s, 18H);
13C NMR (150 MHz, CDCl3) δ 151.646 (s), 140.982 (s), 139.506
(d), 138.084 (d), 137.018 (d), 136.967 (d), 136.394 (d), 135.647
(s), 135.422 (s), 135.153 (s), 134.684 (s), 134.501 (s), 133.736
(d), 133.541 (d), 132.731 (s), 125.340 (d), 122.133 (d), 121.580
(d), 121.176 (d), 116.462 (d), 42.785 (d), 34.189 (s), 30.326 (q).
Bis(3-m et h yl-1-a zu len yl)(3,5-d i-ter t-b u t yl-4-h yd r ox-
yp h en yl)m eth a n e (7e). The general procedure was followed
using 1-methylazulene (8b) (715 mg, 5.03 mmol) and 3,5-di-
tert-butyl-4-hydroxybenzaldehyde (1.17 g, 5.00 mmol). Column
chromatography on silica gel with CH2Cl2/CCl4 afforded the
recovered 8b (147 mg, 21%) and the methane 7e (1.00 g, 100%).
When the general procedure was followed using 8b (712 mg,
5.01 mmol) and the benzaldehyde (610 mg, 2.60 mmol) in a
50% acetic acid solution of CH2Cl2 (3.7 mL) at 10 kbar for 24
h, column chromatography afforded the recovered 8b (54 mg,
7.6%) and the methane 7e (754 mg, 60%). 7e: blue prisms;
mp 208.0-209.0 °C; MS (70 eV) m/z (rel inten) 500 (M+, 100),
485 (23), 141 (25), 57 (50); ES (CH2Cl2) λmax, nm (log ꢀ) 241
7c: blue crystals; mp 217.0-218.0 °C dec; MS (70 eV) m/z
(rel inten) 584 (M+, 85), 528 (42), 527 (97), 277 (21), 57 (100);
ES (CH2Cl2) λmax, nm (log ꢀ) 243 (4.49), 287 (4.90), 304 (4.86),
359 (4.04), 376 (3.96), 611 (2.91); 1H NMR (90 MHz, CDCl3) δ
8.53 (d, J ) 10.8 Hz, 2H), 8.15 (d, J ) 10.8 Hz, 2H), 7.36 (s,
2H), 7.13 (dd, J ) 10.8, 1.9 Hz, 2H), 7.04 (dd, J ) 10.8, 1.9
Hz, 2H), 6.97 (d, J ) 8.6 Hz, 2H), 6.66 (d, J ) 8.6 Hz, 2H),
6.56 (s, 1H), 3.73 (br, 1H), 1.49 (s, 18H), 1.40 (s, 18H); 13C NMR
(22.5 MHz, CDCl3) δ 160.15 (s), 153.26 (s), 138.65 (s), 137.55
(s), 136.21 (d), 134.56 (s), 134.38 (d), 134.14 (s), 132.13 (d),
130.81 (s), 129.81 (d), 119.11 (d), 118.16 (d), 114.87 (d), 41.27
(d), 38.22 (s), 33.31 (s), 32.33 (q), 31.91 (q). Anal. Calcd for
C43H52O: C, 88.30; H, 8.96. Found: C, 88.34; H, 9.07.
10b: blue crystals; mp 155.0-156.0 °C; MS (70 eV) m/z (rel
inten) 346 (M+, 66), 332 (28), 331 (100), 107 (42); ES (CH2Cl2)
λ
max, nm (log ꢀ) 242 (4.25), 290 (4.74), 300 (4.74), 356 (3.80),
1
373 (3.58), 613 (2.55); H NMR (400 MHz, CDCl3) δ 8.527 (d,
J ) 10.5 Hz, 1H), 8.119 (d, J ) 10.5 Hz, 1H), 7.533 (s, 1H),
7.149 (dd, J ) 10.5, 1.8 Hz, 1H), 7.116 (dd, J ) 10.5, 1.8 Hz,
1H), 7.039 (d, J ) 8.3 Hz, 2H), 6.693 (d, J ) 8.3 Hz, 2H), 4.852
(s, 1H), 4.294 (s, 2H), 1.544 (s, 9H), 1.415 (s, 9H); 13C NMR
(100 MHz, CDCl3) δ 160.61 (s), 153.45 (s), 137.83 (s), 135.91
(d), 135.40 (s), 134.45 (d), 134.36 (s), 133.93 (s), 132.30 (d),
129.58 (d), 126.61 (s), 119.09 (d), 118.23 (d), 115.09 (d), 38.19
(s), 33.22 (s), 32.54 (t), 32.22 (q), 31.80 (q). Anal. Calcd for
C25H30O: C, 86.65; H, 8.72. Found: C, 86.72; H, 8.78.
Di(1-a zu le n yl)(3,5-d i-t er t -b u t yl-4-h yd r oxyp h e n yl)-
m eth a n e (7d ). The general procedure was followed using
azulene (8a ) (1.28 g, 10.0 mmol) and 3,5-di-tert-butyl-4-
hydroxybenzaldehyde (1.17 g, 5.00 mmol) at room temper-
ature for 48 h. Column chromatography on silica gel with
CH2Cl2/CCl4 and GPC with CHCl3 afforded the recovered 8a
(630 mg, 49%), the methane 7d (405 mg, 34%), and an
unseparable diastereomeric mixture of 1,3-bis[(1-azulenyl)(3,5-
di-tert-butyl-4-hydroxyphenyl)methyl]azulene (9c and 9d ) (439
mg, 32%) in a ratio of 5:3. When the general procedure was
followed using 8a (1.28 g, 10.0 mmol) and the benzaldehyde
(587 mg, 2.51 mmol) in a 50% acetic acid solution of CH2Cl2
(9.1 mL) at 10 kbar for 24 h, column chromatography afforded
the recovered 8a (538 mg, 42%), the methane 7d (211 mg,
15%), and a diastereomeric mixture of 9c and 9d (236 mg,
16%).
1
(4.52), 280 (4.85), 358 (3.98), 374 (3.95), 632 (2.79); H NMR
(90 MHz, CDCl3) δ 8.16 (d, J ) 9.2 Hz, 2H), 8.10 (d, J ) 9.2
Hz, 2H), 7.40 (dd, J ) 9.5, 9.0 Hz, 2H), 7.35 (s, 2H), 7.00 (s,
2H), 6.92 (dd, J ) 9.2, 9.0 Hz, 2H), 6.82 (dd, J ) 9.5, 9.2 Hz,
2H), 6.56 (s, 1H), 4.99 (s, 1H), 2.57 (s, 6H), 1.32 (s, 18H); 13C
NMR (22.5 MHz, CDCl3) δ 151.64 (s), 139.20 (d), 136.91 (d),
135.85 (s), 135.27 (s), 134.99 (s), 133.22 (d), 132.95 (d), 132.70
(s), 125.39 (d), 124.44 (s), 120.72 (d), 120.42 (d), 42.24 (d), 34.38
(s), 30.44 (q), 12.79 (q). Anal. Calcd for C37H40O: C, 88.75;
H, 8.05. Found: C, 88.33; H, 8.70.
Bis(3,6-d i-ter t-bu tyl-1-a zu len yl)(3,5-d i-ter t-bu tyl-4-h y-
d r oxyp h en yl)m eth a n e (7f). The general procedure was
followed using 1,6-di-tert-butylazulene (8c) (1.20 g, 5.01 mmol)
and 3,5-di-tert-butyl-4-hydroxybenzaldehyde (1.17 g, 5.00 mmol)
at room temperature for 48 h. Column chromatography on
silica gel with CCl4 afforded the methane 7f (1.39 g, 80%).
When the general procedure was followed using 8c (1.21 g,
5.03 mmol) and the benzaldehyde (1.17 g, 5.01 mmol) at 60
°C for 12 h, column chromatography on silica gel with CH2-
Cl2/CCl4 and GPC with CHCl3 afforded the methane 7f (684
mg, 39%) and R-(3,6-di-tert-butyl-1-azulenyl)-3,5-di-tert-butyl-
1,4-benzoquinone methide (11) (474 mg, 21%). When the
general procedure was followed using 8c (1.20 g, 5.00 mmol)
and the benzaldehyde (610 mg, 2.60 mmol) in a 50% acetic
acid solution of CH2Cl2 (3.7 mL) at 10 kbar for 24 h, column
chromatography on silica gel with CH2Cl2/CCl4 and GPC with
CHCl3 afforded the recovered 8c (573 mg, 48%) and the
methane 7f (522 mg, 57%).
7d : blue plates; mp 182.0-183.0 °C; MS (70 eV) m/z (rel
inten) 472 (M+, 100), 471 (21), 415 (26), 267 (28), 265 (30); ES
(CH2Cl2) λmax, nm (log ꢀ) 239 (4.59), 278 (4.88), 351 (4.02), 367
(3.92), 602 (2.83), 657 (2.74); 1H NMR (600 MHz, CDCl3) δ
8.286 (d, J ) 9.7 Hz, 2H), 8.249 (d, J ) 9.4 Hz, 2H), 7.498 (d,
J ) 3.9 Hz, 2H), 7.485 (dd, J ) 10.0, 9.9 Hz, 2H), 7.270 (d, J
) 3.9 Hz, 2H), 7.050 (dd, J ) 9.9, 9.4 Hz, 2H), 7.023 (s, 2H),
6.982 (dd, J ) 10.0, 9.7 Hz, 2H), 6.641 (s, 1H), 5.021 (s, 1H),
1.320 (s, 18H); 13C NMR (150 MHz, CDCl3) δ 151.804 (s),
141.012 (s), 138.197 (d), 137.122 (d), 136.481 (d), 135.706 (s),
135.341 (s), 134.873 (s), 134.420 (s), 133.657 (d), 125.444 (d),
122.237 (d), 121.729 (d), 116.536 (d), 42.610 (d), 34.269 (s),
30.330 (q). Anal. Calcd for C35H36O: C, 88.94; H, 7.68.
Found: C, 88.48; H, 7.89.
7f: blue crystals; mp 255.0-256.0 °C dec; MS (70 eV) m/z
(rel inten) 696 (M+, 100), 640 (32), 639 (59); ES (CH2Cl2) λmax
,
nm (log ꢀ) 243 (4.48), 285 (4.92), 359 (4.01), 377 (3.93), 618
(2.80); 1H NMR (90 MHz, CDCl3) δ 8.50 (d, J ) 10.8 Hz, 2H),
8.25 (d, J ) 10.8 Hz, 2H), 7.45 (s, 2H), 7.11 (dd, J ) 10.8, 1.8
Hz, 2H), 7.05 (dd, J ) 10.8, 1.8 Hz, 2H), 7.00 (s, 2H), 6.52 (s,
1H), 4.96 (s, 1H), 1.50 (s, 18H), 1.40 (s, 18H), 1.32 (s, 18H);
13C NMR (22.5 MHz, CDCl3) δ 159.90 (s), 151.52 (s), 137.43
(s), 136.12 (d and s), 134.99 (s), 134.47 (s), 134.14 (d and s),
131.97 (d), 131.67 (s), 125.57 (d), 119.01 (d), 117.89 (d), 41.57
(d), 38.19 (s), 34.41 (s), 33.34 (s), 32.36 (q), 31.91 (q), 30.47
(q). Anal. Calcd for C51H68O: C, 87.83; H, 9.83. Found: C,
87.61; H, 10.02.
9c and 9d : blue crystals; mp 225.0-227.0 °C dec; MS (70
eV) m/z (rel inten) 816 (M+, 80), 473 (21), 472 (66), 471 (77),
345 (38), 128 (100); ES (CH2Cl2) λmax, nm (log ꢀ) 239 (4.76),
281 (5.05), 350 (4.21), 366 (4.18), 607 (2.97). Anal. Calcd for
C60H64O2‚H2O: C, 86.29; H, 7.96. Found: C, 86.70; H, 8.18.
1
9c (m a jor p r od u ct): H NMR (600 MHz, CDCl3) δ 8.332 (d,
J ) 9.4 Hz, 2H), 8.233 (d, J ) 9.7 Hz, 2H), 8.216 (d, J ) 9.6
Hz, 2H), 7.461 (dd, J ) 9.8, 9.8 Hz, 2H), 7.432 (d, J ) 3.8 Hz,
2H), 7.418 (t, J ) 9.8 Hz, 1H), 7.279 (s, 1H), 7.212 (d, J ) 3.8
Hz, 2H), 7.037 (dd, J ) 9.8, 9.6 Hz, 2H), 6.925 (dd and dd, J
) 9.8, 9.4 Hz and J ) 9.8, 9.7 Hz, 4H), 6.593 (s, 2H), 4.928 (s,
1H), 1.156 (s, 18H); 13C NMR (150 MHz, CDCl3) δ 151.646 (s),
141.017 (s), 138.978 (d), 138.023 (d), 137.096 (d and d), 136.467
(d), 135.467 (s), 135.383 (s), 135.100 (s), 134.928 (s), 134.405
(s), 133.519 (d), 133.034 (d and s), 125.340 (d), 122.204 (d),
121.739 (d), 121.313 (d), 116.440 (d), 41.930 (d), 34.100 (s),
30.180 (q). 9d (m in or p r od u ct): 1H NMR (600 MHz, CDCl3)
11: greenish brown plates; mp 130.5-133.0 °C; MS (70 eV)
m/z (rel inten) 456 (M+, 100), 441 (56), 399 (24), 57 (42); ES
(CH2Cl2) λmax, nm (log ꢀ) 232 (4.39), 258 (4.35), 292 (4.31), 301
(4.30), 355 (4.13), 505 (4.69); 1H NMR (400 MHz, CDCl3) δ
8.628 (d, J ) 11.0 Hz, 1H), 8.487 (d, J ) 11.0 Hz, 1H), 8.183
(s, 1H), 7.982 (d, J ) 2.2 Hz, 1H), 7.668 (s, 1H), 7.462 (dd, J
) 11.0, 1.8 Hz, 1H), 7.451 (dd, J ) 11.0, 1.8 Hz, 1H), 7.174 (d,
J ) 2.2 Hz, 1H), 1.614 (s, 9H), 1.470 (s, 9H), 1.404 (s, 9H),
1.385 (s, 9H); 13C NMR (100 MHz, CDCl3) δ 185.58 (s), 163.57
(s), 148.00 (s), 145.80 (s), 142.44 (s), 141.14 (s), 138.62 (s),
136.06 (d), 135.83 (d), 135.78 (d), 134.76 (d), 133.11 (d), 128.92

2430 J . Org. Chem., Vol. 62, No. 8, 1997
Ito et al.
(d), 127.54 (s), 123.76 (d), 123.43 (s), 123.24 (d), 38.56 (s), 35.49
(s), 34.98 (s), 33.28 (s), 31.68 (q), 31.67 (q), 29.64 (q). Anal.
Calcd for C33H44O: C, 86.79; H, 9.71. Found: C, 86.90; H, 9.94.
Gen er a l P r oced u r e for th e Syn th esis of Di(1-a zu le-
n yl)(4-h yd r oxy- a n d 3,5-d i-ter t-bu tyl-4-h yd r oxyp h en yl)-
m eth yl Hexaflu or oph osph ates 5a -f‚P F6-. DDQ was added
at room temperature to a solution of di(1-azulenyl)(4-hydroxy-
and 3,5-di-tert-butyl-4-hydroxyphenyl)methanes 7a -f in CH2-
Cl2 (100 mL). The solution was stirred at the same temper-
ature for 5 min. A 60% aqueous HPF6 solution (10 mL) was
added to the reaction mixture. After the mixture was stirred
at room temperature for an additional 5 min, water was added
to the mixture. The resulting suspension was filtered with
suction. The organic layer was separated, dried with MgSO4,
and concentrated under reduced pressure. The residue was
dissolved in CH2Cl2 (5 mL) and hexane (100 mL) was added
to the solution. The precipitated crystals were collected by
azulenyl)(3,5-di-tert-butyl-4-hydroxyphenyl)methane (7d ) (473
mg, 1.00 mmol). Recrystallization from CH2Cl2/hexane gave
-
the hexafluorophosphate 5d ‚PF6 (617 mg, 100%): brown
crystals; mp 154.5-157.0 °C dec; MS (FAB) m/z 471 (M+
-
PF6); ES (MeCN) λmax, nm (log ꢀ) 230 (4.63), 251 (4.50), 289
(4.41), 404 (4.06), 511 (4.40), 622 (4.49); 1H NMR (90 MHz,
CDCl3) δ 8.79 (d, J ) 11.0 Hz, 2H), 8.22-7.81 (m, 8H), 7.72
(d, J ) 4.4 Hz, 2H), 7.52 (dd, J ) 10.3, 10.3 Hz, 2H), 7.26 (s,
2H), 6.20 (br, 1H), 1.40 (s, 18H); 13C NMR (22.5 MHz, CDCl3)
δ 165.94 (s), 160.66 (s), 152.77 (s), 147.22 (s), 146.12 (d), 143.16
(d), 141.30 (d), 139.05 (d), 137.31 (s), 134.72 (d), 134.32 (d),
133.10 (d), 132.55 (s), 132.28 (s), 125.45 (d), 34.47 (s), 30.08
(q). Anal. Calcd for C35H35O‚PF6: C, 68.17; H, 5.72. Found:
C, 69.40; H, 5.74.
Bis(3-m et h yl-1-a zu len yl)(3,6-d i-ter t-b u t yl-4-h yd r oxy-
p h en yl)m eth yl Hexa flu or op h osp h a te (5e‚P F 6-). The gen-
eral procedure was followed using DDQ (272 mg, 1.20 mmol)
and bis(3-methyl-1-azulenyl)(3,5-di-tert-butyl-4-hydroxyphe-
nyl)methane (7e) (501 mg, 1.00 mmol). Recrystallization from
CH2Cl2/hexane gave the hexafluorophosphate 5e‚PF6- (593 mg,
92%): dark brown crystals; mp 208.0-211.0 °C; MS (FAB) m/z
499 (M+ - PF6); ES (MeCN) λmax, nm (log ꢀ) 234 (4.60), 276
(4.38), 405 (4.09), 525 (4.27), 657 (4.35); 1H NMR (90 MHz,
MeCN-d3) δ 8.74 (d, J ) 11.0 Hz, 2H), 8.19-7.75 (m, 6H), 7.83
(s, 2H), 7.45 (dd, J ) 10.1, 10.1 Hz, 2H), 7.25 (s, 2H), 3.40 (br,
1H), 2.68 (s, 6H), 1.37 (s, 18H); 13C NMR (22.5 MHz, MeCN-
d3) δ 163.96 (s), 161.07 (s), 151.46 (s), 149.15 (s), 146.65 (d),
143.60 (d), 139.85 (d), 139.02 (d), 138.57 (s), 135.24 (d), 135.03
(s), 134.08 (d), 133.66 (d), 133.44 (s), 132.56 (s), 35.27 (s), 30.30
(q), 12.89 (q). Anal. Calcd for C37H39O‚PF6: C, 68.93; H, 6.10.
Found: C, 69.32; H, 5.96.
Bis(3,6-d i-ter t-bu tyl-1-a zu len yl)(3,6-d i-ter t-bu tyl-4-h y-
dr oxyph en yl)m eth yl Hexaflu or oph osph ate (5f‚P F6-). The
general procedure was followed using DDQ (274 mg, 1.21
mmol) and bis(3,6-di-tert-butyl-1-azulenyl)(3,5-di-tert-butyl-4-
hydroxyphenyl)methane (7f) (698 mg, 1.00 mmol). Recrystal-
lization from CH2Cl2/hexane gave the hexafluorophosphate
5f‚PF6- (827 mg, 98%): dark brown crystals; mp 232.0-233.0
°C; MS (FAB) m/z 695 (M+ - PF6); ES (MeCN) λmax, nm (log ꢀ)
235 (4.69), 256 (4.60), 299 (4.57), 400 (4.21), 518 (4.36), 666
(4.57); 1H NMR (90 MHz, CDCl3) δ 9.06 (d, J ) 11.2 Hz, 2H),
8.10 (dd, J ) 11.2, 2.0 Hz, 2H), 7.89 (d, J ) 11.0 Hz, 2H), 7.64
(s, 2H), 7.57 (dd, J ) 11.0, 2.0 Hz, 2H), 7.23 (s, 2H), 6.11 (br,
1H), 1.61 (s, 18H), 1.45 (s, 18H), 1.41 (s, 18H); 13C NMR (22.5
MHz, CDCl3) δ 168.29 (s), 161.88 (s), 159.87 (s), 147.95 (s),
147.64 (s), 146.09 (s), 142.83 (d), 139.02 (d), 137.74 (d), 137.03
(s), 134.47 (d), 132.43 (s), 130.94 (d), 130.66 (d and s), 39.31
(s), 34.65 (s), 33.37 (s), 31.57 (q), 31.36 (q), 30.29 (q). Anal.
Calcd for C51H67O‚PF6: C, 72.83; H, 8.03. Found: C, 72.71;
H, 7.85.
filtration, washed with hexane, and dried in vacuo to give the
-
hexafluorophosphates 5a -f‚PF6
. The product was further
purified by recrystallization from CH2Cl2/hexane.
Di(1-a zu len yl)(4-h yd r oxyp h en yl)m eth yl Hexa flu or o-
p h osp h a te (5a ‚P F 6-). The general procedure was followed
using DDQ (273 mg, 1.20 mmol) and di(1-azulenyl)(4-hydroxy-
phenyl)methane (7a ) (361 mg, 1.00 mmol). Recrystallization
-
from CH2Cl2/hexane gave the hexafluorophosphate 5a ‚PF6
(506 mg, 100%): brown crystals; mp 140.5-144.0 °C dec; MS
(FAB) m/z 359 (M+ - PF6); ES (MeCN) λmax, nm (log ꢀ) 229
(4.60), 247 (4.50), 286 (4.41), 385 (4.12), 495 (4.30), 624 (4.48);
1H NMR (600 MHz, DMSO-d6, 60 °C) δ 9.072 (d, J ) 9.6 Hz,
2H), 8.293 (dd, J ) 9.9, 9.8 Hz, 2H), 8.163 (dd, J ) 9.8, 9.6
Hz, 2H), 8.079 (d, J ) 4.5 Hz, 2H), 8.060 (d, J ) 9.9 Hz, 2H),
7.956 (d, J ) 4.5 Hz, 2H), 7.773 (dd, J ) 9.9, 9.9 Hz, 2H), 7.444
(d, J ) 8.6 Hz, 2H), 7.173 (d, J ) 8.6 Hz, 2H); 13C NMR (150
MHz, DMSO-d6, 60 °C) δ 164.821 (s), 164.178 (s), 152.336 (s),
146.807 (s), 145.930 (d), 143.180 (d), 141.110 (d), 138.875 (d),
138.484 (d), 134.253 (d), 133.363 (d), 132.251 (s), 131.776 (s),
125.176 (d), 116.532 (d). Anal. Calcd for C27H19O‚PF6: C,
64.29; H, 3.80. Found: C, 64.13; H, 4.20.
Bis(3-m e t h yl-1-a zu le n yl)(4-h yd r oxyp h e n yl)m e t h yl
Hexa flu or op h osp h a te (5b‚P F 6-). The general procedure
was followed using DDQ (273 mg, 1.20 mmol) and bis(3-
methyl-1-azulenyl)(4-hydroxyphenyl)methane (7b) (389 mg,
1.00 mmol). Recrystallization from CH2Cl2/hexane gave the
-
hexafluorophosphate 5b‚PF6 (533 mg, 100%): dark brown
crystals; mp 147.0-150.0 °C dec; MS (FAB) m/z 387 (M+
-
PF6); ES (MeCN) λmax, nm (log ꢀ) 230 (4.74), 291 (4.39), 399
1
(4.21), 510 (4.17), 657 (4.44); H NMR (90 MHz, MeCN-d3) δ
8.69 (d, J ) 11.0 Hz, 2H), 8.04-7.77 (m, 6H), 7.77 (s, 2H),
7.04 (dd, J ) 10.3, 10.3 Hz, 2H), 7.26 (s, J ) 8.9 Hz, 2H), 7.01
(d, J ) 8.9 Hz, 2H), 6.84 (br, 1H), 2.63 (s, 6H); 13C NMR (22.5
MHz, MeCN-d3) δ 163.63 (s), 151.65 (s), 151.10 (s), 149.08 (s),
146.61 (d), 143.60 (d), 139.69 (d), 138.96 (d and d), 135.18 (s),
134.27 (d), 134.14 (s), 134.05 (d), 132.59 (s), 117.04 (d), 12.95
(q). Anal. Calcd for C29H23O‚PF6: C, 65.42; H, 4.35. Found:
C, 66.18; H, 5.22.
Gen er a l P r oced u r e for th e Neu tr a liza tion of th e
-
Hexa flu or op h osp h a tes 5a -f‚P F 6
. A solution of the ap-
propriate di(1-azulenyl)(4-hydroxyphenyl)methyl hexafluoro-
phosphate 5a -f‚PF6 (0.92-1.00 mmol) in CH2Cl2 (100 mL)
-
was treated with 5% aqueous NaHCO3, washed with water,
dried with MgSO4, and concentrated in vacuo. The residue
was purified by column chromatography on Al2O3 to afford the
R,R-di(1-azulenyl)-1,4-benzoquinone methides 6a -f. The prod-
uct was further purified by recrystallization.
Bis(3,6-d i-t er t -b u t yl-1-a zu le n yl)(4-h yd r oxyp h e n yl)-
m eth yl Hexa flu or op h osp h a te (5c‚P F 6-). The general pro-
cedure was followed using DDQ (272 mg, 1.20 mmol) and bis-
(3,6-di-tert-butyl-1-azulenyl)(4-hydroxyphenyl)methane (7c) (589
mg, 1.01 mmol). Recrystallization from CH2Cl2/hexane gave
r,r-Di(1-azu len yl)-1,4-ben zoqu in on e Meth ide (6a). The
general procedure was followed with di(1-azulenyl)(4-hydrox-
yphenyl)methyl hexafluorophosphate (5a ‚PF6-) (506 mg, 1.00
mmol). The crude material was then purified by column
chromatography on Al2O3 with MeOH/CH2Cl2 to afford the
quinone methide 6a (330 mg, 92%): greenish brown crystals;
mp 68.0-74.0 °C dec; MS (70 eV) m/z (rel inten) 358 (M+, 29),
267 (30), 265 (44), 231 (40), 128 (48); ES (CH2Cl2) λmax, nm
(log ꢀ) 235 (4.61), 276 (4.63), 323 (4.31), 404 (4.07), 522 (4.43);
1H NMR (600 MHz, CDCl3) δ 8.482 (d, J ) 9.7 Hz, 2H), 7.910
(d, J ) 9.8 Hz, 2H), 7.775 (d, J ) 4.1 Hz, 2H), 7.715 (dd, J )
9.8, 9.7 Hz, 2H), 7.469 (d, J ) 4.1 Hz, 2H), 7.427 (dd, J ) 9.7,
9.7 Hz, 2H), 7.287 (d, J ) 9.7 Hz, 2H), 7.171 (dd, J ) 9.8, 9.8
Hz, 2H), 6.506 (d, J ) 9.7 Hz, 2H); 13C NMR (150 MHz, CDCl3)
δ 186.642 (s), 152.571 (s), 145.583 (s), 143.033 (d), 140.812 (s),
140.716 (d), 139.532 (d), 138.394 (d), 136.948 (d), 130.795 (s),
128.246 (s), 126.705 (d), 126.585 (d), 126.545 (d), 119.515 (d).
-
the hexafluorophosphate 5c‚PF6 (734 mg, 100%): brown
crystals; mp 292.0-293.0 °C dec; MS (FAB) m/z 583 (M+
-
PF6); ES (MeCN) λmax, nm (log ꢀ) 234.3 (4.64), 253 (4.62), 301
(4.53), 397 (4.28), 503 (4.21), 666 (4.64); 1H NMR (90 MHz,
CDCl3) δ 9.00 (d, J ) 11.0 Hz, 2H), 8.05 (dd, J ) 11.0, 1.7 Hz,
2H), 7.87 (d, J ) 10.8 Hz, 2H), 7.65 (s, 2H), 7.60 (dd, J ) 10.8,
1.7 Hz, 2H), 7.22 (s, 4H), 5.33 (br, 1H), 1.58 (s, 18H), 1.47 (s,
18H); 13C NMR (22.5 MHz, CDCl3) δ 168.10 (s), 164.51 (s),
162.80 (s), 147.98 (s), 147.83 (s), 146.12 (s), 143.28 (d), 138.62
(d), 138.01 (d), 137.55 (d), 131.82 (s), 130.88 (s), 130.72 (d),
130.45 (d), 117.37 (d), 39.31 (s), 33.31 (s), 31.60 (q), 31.30 (q).
Anal. Calcd for C43H51O‚PF6: C, 70.86; H, 7.05. Found: C,
71.01; H, 7.09.
Di(1-a zu len yl)(3,6-d i-ter t-bu tyl-4-h yd r oxyp h en yl)m e-
th yl Hexa flu or op h osp h a te (5d ‚P F 6-). The general proce-
dure was followed using DDQ (273 mg, 1.20 mmol) and di(1-

Di(1-azulenyl)(4-hydroxyphenyl)methyl Cations
J . Org. Chem., Vol. 62, No. 8, 1997 2431
Anal. Calcd for C27H18O‚1/2H2O: C, 88.26; H, 5.21. Found:
C, 88.66; H, 5.40.
droxyphenyl)methyl hexafluorophosphate (5e‚PF6-) (593 mg,
0.92 mmol). The crude material was then purified by column
chromatography on Al2O3 with CH2Cl2/CCl4 to afford the
quinone methide 6e (375 mg, 82%): brown needles; mp 286.0-
286.5 °C; MS (70 eV) m/z (rel inten) 498 (M+, 100), 484 (24),
483 (64), 456 (20), 441 (22), 57 (41); ES (CH2Cl2) λmax, nm (log
r,r-Bis(3-m et h yl-1-a zu len yl)-1,4-b en zoq u in on e Me-
th id e (6b). The general procedure was followed with bis(3-
methyl-1-azulenyl)(4-hydroxyphenyl)methyl hexafluorophos-
phate (5b‚PF6-) (533 mg, 1.00 mmol). The crude material was
then purified by column chromatography on Al2O3 with MeOH/
CH2Cl2 to afford the quinone methide 6b (354 mg, 92%):
greenish brown crystals; mp 225.0-231.0 °C dec; MS (70 eV)
m/z (rel inten) 386 (M+, 100); ES (CH2Cl2) λmax, nm (log ꢀ) 237
1
ꢀ) 238 (4.62), 277 (4.73), 329 (4.42), 419 (4.21), 523 (4.43); H
NMR (90 MHz, CDCl3) δ 8.29 (d, J ) 9.2 Hz, 2H), 7.86 (d, J )
9.7 Hz, 2H), 7.59 (dd, J ) 9.7, 9.5 Hz, 2H), 7.54 (s, 2H), 7.24
(dd, J ) 9.7, 9.2 Hz, 2H), 7.11 (s, 2H), 6.99 (dd, J ) 9.7, 9.5
Hz, 2H), 2.63 (s, 6H), 1.19 (s, 18H); 13C NMR (22.5 MHz,
CDCl3) δ 185.39 (s), 146.64 (s), 145.54 (s), 142.95 (d), 141.27
(s), 139.53 (s), 138.62 (d), 136.39 (d), 134.60 (d), 133.62 (d),
129.78 (s), 128.25 (s), 126.55 (s), 124.35 (d), 124.05 (d), 35.23
(s), 29.86 (q), 12.67 (q). Anal. Calcd for C37H38O: C, 89.11;
H, 7.68. Found: C, 89.48; H, 7.87.
r,r-Bis(3,5-d i-ter t-b u t yl-1-a zu len yl)-3,5-d i-ter t-b u t yl-
1,4-ben zoqu in on e Meth id e (6f). The general procedure was
followed with bis(3,5-di-tert-butyl-1-azulenyl)(3,5-di-tert-butyl-
4-hydroxyphenyl)methyl hexafluorophosphate (5f‚PF6-) (827
mg, 0.98 mmol). The crude material was then purified by
column chromatography on Al2O3 with CH2Cl2/CCl4 to afford
the quinone methide 6f (627 mg, 92%): dark brown crystals;
mp >300 °C; MS (70 eV) m/z (rel inten) 694 (M+, 100), 680
(21), 679 (36), 637 (20), 57 (51); ES (CH2Cl2) λmax, nm (log ꢀ)
241 (4.62), 286 (4.78), 336 (4.43), 423 (4.20), 534 (4.46); 1H
NMR (400 MHz, CDCl3) δ 8.714 (d, J ) 10.8 Hz, 2H), 7.791
(d, J ) 10.8 Hz, 2H), 7.591 (s, 2H), 7.440 (dd, J ) 10.8, 1.8
Hz, 2H), 7.189 (dd, J ) 10.8, 1.8 Hz, 2H), 7.147 (s, 2H), 1.560
(s, 18H), 1.420 (s, 18H), 1.223 (s, 18H); 13C NMR (100 MHz,
CDCl3) δ 185.36 (s), 162.55 (s), 147.68 (s), 144.88 (s), 140.55
(d), 139.88 (s), 139.46 (s), 139.24 (s), 135.76 (d), 135.69 (d),
134.19 (d), 128.73 (s), 127.40 (s), 123.13 (d), 121.66 (d), 38.44
(s), 35.20 (s), 33.31 (s), 32.05 (q), 31.69 (q), 29.82 (q). Anal.
Calcd for C51H66O‚H2O: C, 85.90; H, 9.61. Found: C, 86.09;
H, 9.47.
1
(4.62), 283 (4.65), 330 (4.30), 355 (4.31), 534 (4.49); H NMR
(400 MHz, CDCl3) δ 8.365 (d, J ) 9.5 Hz, 2H), 7.825 (d, J )
10.0 Hz, 2H), 7.653 (dd, J ) 9.8, 9.8 Hz, 2H), 7.607 (s, 2H),
7.362 (dd, J ) 9.8, 9.5 Hz, 2H), 7.226 (d, J ) 9.7 Hz, 2H), 7.074
(dd, J ) 10.0, 9.8 Hz, 2H), 6.497 (d, J ) 9.7 Hz, 2H), 2.646 (s,
6H); 13C NMR (100 MHz, CDCl3) δ 186.36 (s), 152.43 (s), 143.59
(d), 142.72 (s), 141.44 (s), 140.74 (d), 139.37 (d), 136.52 (d),
135.27 (d), 129.34 (s), 128.09 (s), 127.65 (s), 126.16 (d), 126.07
(d), 125.48 (d), 12.62 (q). Anal. Calcd for C29H22O‚1/2H2O: C,
88.07; H, 5.86. Found: C, 88.47; H, 5.85.
r,r-Bis(3,6-d i-t er t -b u t yl-1-a zu le n yl)-1,4-b e n zoq u in -
on e Meth id e (6c). The general procedure was followed with
bis(3,6-di-tert-butyl-1-azulenyl)(4-hydroxyphenyl)methyl hexaflu-
orophosphate (5c‚PF6-) (734 mg, 1.01 mmol). The crude
material was then purified by column chromatography on
Al2O3 with MeOH/ethyl acetate/CH2Cl2 to afford the quinone
methide 6c (478 mg, 82%): brown crystals; mp 299.0-300.0
°C dec; MS (70 eV) m/z (rel inten) 582 (M+, 100); ES (CH2Cl2)
λ
max, nm (log ꢀ) 240 (4.60), 289 (4.73), 334 (4.36), 359 (4.34),
1
537 (4.50); H NMR (90 MHz, CDCl3) δ 8.78 (d, J ) 10.8 Hz,
2H), 7.91 (d, J ) 10.8 Hz, 2H), 7.56 (dd, J ) 10.8, 1.8 Hz, 2H),
7.52 (s, 2H), 7.31 (dd, J ) 10.8, 1.8 Hz, 2H), 7.24 (d, J ) 9.6
Hz, 2H), 6,51 (d, J ) 9.6 Hz, 2H), 1.55 (s, 18H), 1.45 (s, 18H);
13C NMR (22.5 MHz, CDCl3) δ 186.18 (s), 163.68 (s), 153.38
(s), 141.91 (s), 140.85 (d), 140.72 (d), 140.54 (s), 140.30 (s),
136.30 (d), 135.91 (d), 128.74 (s), 127.37 (s), 125.60 (d), 124.63
(d), 123.31 (d), 38.67 (s), 33.19 (s), 31.94 (q), 31.78 (q). Anal.
Calcd for C43H50O‚1/2H2O: C, 87.26; H, 8.68. Found: C, 87.53;
H, 9.09.
P r oton a tion of r,r-Di(1-a zu len yl)-1,4-ben zoqu in on e
Meth id es 6a -f w ith HP F 6. A solution of the appropriate
R,R-di(1-azulenyl)-1,4-benzoquinone methide 6a -f (0.20 mmol)
in CH2Cl2 (20 mL) was treated with 60% HPF6 (2 mL) and
water (20 mL). The organic layer was separated, dried with
MgSO4, and concentrated in vacuo. The residue was precipi-
tated from CH2Cl2 (3 mL) and hexane (50 mL) to afford the
hexafluorophosphates 5a ‚PF6- (93 mg, 92%), 5b‚PF6- (108 mg,
r,r-Di(1-a zu len yl)-3,5-d i-ter t-b u t yl-1,4-b en zoq u in on e
Meth id e (6d ). The general procedure was followed with di-
(1-azulenyl)(3,5-di-tert-butyl-4-hydroxyphenyl)methyl hexaflu-
orophosphate (5d ‚PF6-) (617 mg, 1.00 mmol). The crude
material was then purified by column chromatography on
Al2O3 with CH2Cl2/CCl4 to afford the quinone methide 6d (366
mg, 78%): greenish brown crystals; mp 223.0-224.0 °C; MS
(70 eV) m/z (rel inten) 470 (M+, 100), 456 (35), 455 (91), 428
(31), 427 (21), 413 (35), 386 (26), 266 (22), 265 (39), 57 (22);
ES (CH2Cl2) λmax, nm (log ꢀ) 236 (4.63), 272 (4.72), 323 (4.40),
-
100%), 5c‚PF6- (137 mg, 94%), 5d ‚PF6- (121 mg, 98%), 5e‚PF6
-
(129 mg, 100%), and 5f‚PF6 (164 mg, 97%), respectively.
Ack n ow led gm en t. This work was supported by the
Nishida Research Fund for Fundamental Organic Chem-
istry and a Grant-in-Aid for Scientific Research No.
08740480 from the Ministry of Education, Science,
Sports and Culture, J apan.
1
407 (4.27), 507 (4.42); H NMR (600 MHz, CDCl3) δ 8.424 (d,
J ) 9.5 Hz, 2H), 7.906 (d, J ) 9.8 Hz, 2H), 7.750 (d, J ) 4.0
Hz, 2H), 7.646 (dd, J ) 9.8, 9.7 Hz, 2H), 7.439 (d, J ) 4.0 Hz,
2H), 7.329 (dd, J ) 9.7, 9.5 Hz, 2H), 7.177 (s, 2H), 7.087 (dd,
J ) 9.8, 9.8 Hz, 2H), 1.203 (s, 18H); 13C NMR (150 MHz,
CDCl3) δ 185.628 (s), 147.001 (s), 145.935 (s), 144.486 (s),
142.397 (d), 139.217 (s), 138.882 (d), 137.825 (d), 136.878 (d),
133.569 (d), 131.335 (s), 128.412 (s), 125.508 (d), 125.036 (d),
118.701 (d), 35.192 (s), 29.733 (q). Anal. Calcd for C35H34O:
C, 89.32; H, 7.28. Found: C, 89.38; H, 7.53.
Su p p or tin g In for m a tion Ava ila ble: The IR spectral data
for all mentioned compounds (hexafluorophosphates of 5a -f,
6a -f, 7a -f, 9a -d , 10a ,b, and 11) (6 pages). This material is
contained in libraries on microfiche, immediately follows this
article in the microfilm version of the journal, and can be
ordered from the ACS; see any current masthead page for
ordering information.
r,r-Bis(3-m eth yl-1-a zu len yl)-3,5-d i-ter t-bu tyl-1,4-ben -
zoqu in on e Meth id e (6e). The general procedure was fol-
lowed with bis(3-methyl-1-azulenyl)(3,5-di-tert-butyl-4-hy-
J O961820Q