peri-Naphthylenediamines 36. 5,6-Bis(dimethylamino)acenaphthylene in [4+2] cycloaddition reactions. Synthesis and characteristic features of protonation of "proton sponges" with the 8,9-diazafluoranthene structure

Article abstract of DOI:10.1023/A:1022429322461

5,6-Bis(dimethylamino)acenaphthylene is readily involved in [4+2] cycloaddition reactions with symm-tetrazine derivatives to form new "proton sponges" with the diazafluoranthene skeleton. Under analogous condition, 1,8-bis(dimethylamino)-4-vinylnaphthalene gave 4-pyridazinyl derivatives. The relative reactivities of 5,6-bis(dimethylamino)acenaphthylene, 1,8-bis(dimethylamino)-4-vinylnaphthalene, 5-dimethylaminoacenaphthylene, and acenaphthylene in the reactions with 3,6-diphenyl-symm-tetrazine are in a ratio of 32:17:14:1. The site of protonation of 3,4-bis(dimethylamino)-7,10-diphenyl- 8,9-diazafluoranthene is controlled by the basicity of the solvent. The reaction in acetonitrile afforded the cation stabilized by an intramolecular hydrogen bond, whereas the reaction in dimethyl sulfoxide gave rise to the resonance-stabilized cation. 6,7-Bis(dimethylamino)phenalen-1-one was protonated only at the carbonyl group.

Full text of DOI:10.1023/A:1022429322461

218
Russian Chemical Bulletin, International Edition, Vol. 52, No. 1, pp. 218—227, January, 2003
periꢀNaphthylenediamines
36.* 5,6ꢀBis(dimethylamino)acenaphthylene in [4+2] cycloaddition reactions.
Synthesis and characteristic features of protonation
of "proton sponges" with the 8,9ꢀdiazafluoranthene structure
ꢀ
A. F. Pozharskii, V. A. Ozeryanskii, and N. V. Vistorobskii
Rostov State University,
7 ul. Zorge, 344090 RostovꢀonꢀDon, Russian Federation.
Fax: +7 (863 2) 22 3958. Eꢀmail: vv_ozer2@chimfak.rsu.ru
5,6ꢀBis(dimethylamino)acenaphthylene is readily involved in [4+2] cycloaddition reacꢀ
tions with symmꢀtetrazine derivatives to form new "proton sponges" with the diazafluoranthene
skeleton. Under analogous condition, 1,8ꢀbis(dimethylamino)ꢀ4ꢀvinylnaphthalene gave
4ꢀpyridazinyl derivatives. The relative reactivities of 5,6ꢀbis(dimethylamino)acenaphthylene,
1,8ꢀbis(dimethylamino)ꢀ4ꢀvinylnaphthalene, 5ꢀdimethylaminoacenaphthylene, and acenaꢀ
phthylene in the reactions with 3,6ꢀdiphenylꢀsymmꢀtetrazine are in a ratio of 32 : 17 : 14 : 1.
The site of protonation of 3,4ꢀbis(dimethylamino)ꢀ7,10ꢀdiphenylꢀ8,9ꢀdiazafluoranthene is
controlled by the basicity of the solvent. The reaction in acetonitrile afforded the cation
stabilized by an intramolecular hydrogen bond, whereas the reaction in dimethyl sulfoxide gave
rise to the resonanceꢀstabilized cation. 6,7ꢀBis(dimethylamino)phenalenꢀ1ꢀone was protoꢀ
nated only at the carbonyl group.
Key words: acenaphthylenes, 8,9ꢀdiazafluoranthenes, αꢀvinylnaphthalene, pyridazines,
1,2,4,5ꢀtetrazines, phenalenꢀ1ꢀone, [4+2] cycloaddition, relative reactivity, protonation, "proꢀ
ton sponges".
In our recent studies of the chemistry of 1,8ꢀbis(diꢀ
naphthylenes 3 and 4 and 1,8ꢀbis(dimethylamino)ꢀ4ꢀ
vinylnaphthalene (5).
methylamino)naphthalene ("proton sponge", 1, see the
review2), we have demonstrated that, in spite of large
steric strains in this molecule, the periꢀdimethylamino
groups retain the exceptionally strong electronꢀdonating
effect toward the aromatic πꢀsystem. This is manifested in
the unusually high reactivity of compound 1 in electroꢀ
philic substitution reactions3 as well as in its involvement
in new types of reactions, which have not been observed
earlier for compounds of the naphthalene series.4 In this
connection, it was of interest to quantitatively estimate
the electronꢀdonating effects of two NMe2 groups in molꢀ
ecule 1, particularly, in the transformations requiring staꢀ
bilization of the positive charge in the transition complex.
Unfortunately, the solution of this problem presents diffiꢀ
culties because most of the reactions of "proton sponges"
follow radically different pathways compared to their anaꢀ
logs containing other +M substituents or one NMe2 group.
In attempting to find transformations of "proton sponges"
proceeding similarly to those of their electronic analogs,
we studied the [4+2] cycloaddition of 5,6ꢀbis(dimethylꢀ
amino)acenaphthylene (2), which has been synthesized
recently,5 and a series of related compounds, viz., aceꢀ
It is known that acenaphthylenes act as very active
dienophiles in inverse electron demand cycloaddition reꢀ
actions6,7 in which the lowest unoccupied MO of the
diene and the highest occupied MO of the dienophile are
involved in the transition state of the reaction. In our
study, we used readily available 3,6ꢀdiphenylꢀsymmꢀ
tetrazine (DPT) (6) as the diene.
* For Part 35, see Ref. 1.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 206—215, January, 2003.
1066ꢀ5285/03/5201ꢀ218 $25.00 © 2003 Plenum Publishing Corporation

8,9ꢀDiazafluoranthene "proton sponges"
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 1, January, 2003
219
We found that up to oneꢀhalf of the starting diamine 2
remained unconsumed upon heating of acenaphthylene 2
with DPT in benzene even if the diene and dienophile
were taken in an equimolar ratio, and 8,9ꢀdiazafluorꢀ
anthene (8) was the only isolated product (Table 1). This
is consistent with the general scheme of transformations
in which the second DPT molecule serves as an oxiꢀ
dant8 with respect to the initially formed cycloadduct 7
(Scheme 1). Actually, refluxing of the starting compoꢀ
nents, which were taken in a 2 : 6 ratio of 1 : 2, over 30 h
afforded dehydrogenation product 8 in 94% yield, and
3,6ꢀdiphenylꢀ1,4ꢀdihydroꢀ1,2,4,5ꢀtetrazine was detected
in the reaction mixture.
180—200 °C, 1 h, 80%).7 Evidently, the reaction of
tetrazine 6 with diamine 2 proceeded much more readily
than that with acenaphthylene 4.
Taking into account the aforesaid, it seemed attractive
to us to use directly 5,6ꢀbis(dimethylamino)acenaphthene
9
11 for the synthesis of "proton
sponge" 8. However, the experiment
demonstrated that compound 11 was
not dehydrogenated with DPT in reꢀ
fluxing benzene (cf. successful deꢀ
hydrogenation of compound 11 with
chloranil5).
By contrast, acenaphthene 11 reꢀ
acted with tetrazine 6 in refluxing dimethyl sulfoxide
(189 °C). The dienophile : diene ratio of 1 : 3 was the ratio
of choice in the reactions performed under an inert atmoꢀ
sphere, which corresponds to the series of the transformaꢀ
tions 11 → 2 → 7 → 8. In each step of this process, one
equivalent of azadiene was consumed. After 6.5 h, the
starting compounds disappeared but the yield of comꢀ
pound 8 was at most 27% due to competitive oligomerizaꢀ
tion processes.
Scheme 1
As expected, the reaction of "proton sponge" 2 with
dimethyl tetrazinedicarboxylate 12 proceeded even more
readily (already at 20 °C) to form diazafluoranthene 14 as
the final product in high yield (Scheme 2, see Table 1).
Scheme 2
R = CO2Me
Unlike the aboveꢀdescribed reaction, the reaction of
unsubstituted acenaphthylene 4 with tetrazine 6 (as was
demonstrated in the study7) proceeded to completion even
if the reagents were taken in a molar ratio of 1 : 1 because
dehydrogenation of dihydrodiazafluoranthene 9 must proꢀ
ceed more difficultly and there are no reasons to expect
that a portion of DPT would be consumed for its oxidaꢀ
tion. Nevertheless, only aromatic heterocycle 10 was isoꢀ
lated in this case as well due, presumably, to autooxidation
of form 9 with atmospheric oxygen (xylene, sealed tube,
i. atmospheric O2 or 12.
In the reaction of equimolar amounts of 2 and 12, like
in the reaction with tetrazine 6, diamine 2 remained parꢀ
tially unconsumed. The latter compound rapidly disapꢀ
peared upon the addition of the second equivalent of
tetrazine 12. The 1H NMR monitoring in CDCl3 showed
that dihydro adduct 13 was the primary reaction product,
which was then oxidized to compound 14 (including with

220
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 1, January, 2003
Pozharskii et al.
Table 1. Physicochemical characteristics of the compounds synꢀ
thesized
tions for the construction of more complex polycyclic
systems of type 15 containing two fragments of "proton
sponge" 2.
Comꢀ M.p./°C
pound (solvent)
Found
Calculated
Molecular
formula
(%)
С
H
Cl
(I)
3
Oil
85.9
86.1
6.6
6.7
—
C14H13
N
8
275—276
(benzene)
81.2
81.4
6.5
5.9
—
С30H26N4
R = Ph, CO2Me
8*
10
14
16
17
17*
242—245
(decomp., EtOH) 66.4
66.2
5.4
5.0
6.2 C30H27ClN4O4
6.5
Refluxing of compounds 8 or 14 in the presence of
one equivalent of acenaphthylene 2 in oꢀxylene for 60 h
revealed no evidence of their reaction. Under more drasꢀ
tic condition (oꢀxylene, sealed tube, 200 °C, 3 h), 80—90%
of the starting compounds were recovered and the reꢀ
maining portions decomposed. Evidently, the fact that
azadienes 8 and 14, unlike pyridazines containing elecꢀ
tronꢀwithdrawing groups,10 are inactive in these reactions
results from a substantial increase in the energy of LUMO
because of an increase in the electron density in the
pyridazine rings of 8 and 14 caused by the periꢀdimethylꢀ
amino groups.
309—310
(СНСl3)
—
—
—
—
—
—
—
170—172
(toluene)
65.2
65.0
5.3
5.5
C22H22N4O4
Oil
84.9
85.2
7.6
7.7
C14H15
N
184—185
(nꢀoctane)
84.1
84.2
5.6
5.3
C28H21N3
103—104
169—170
(decomp., MeCN)
67.1
67.3
4.6
4.4
6.8 C28H22ClN3O4
7.1
The previously unknown model compound 3 was
prepared by alkylation of 5ꢀaminoacenaphthene in
the KOH—DMF system to form 5ꢀdimethylaminoaceꢀ
naphthene (16) (yield was 95%) followed by dehydrogeꢀ
nation with chloranil upon heating in benzene (this comꢀ
pound was not dehydrogenated with DPT in refluxing
DMSO). The transformation 16 → 3 was accompanied by
a change in the color because acenaphthylene 3, unlike
virtually colorless compound 16, is a darkꢀorange oil with
18
199—201
(toluene)
80.6
80.7
6.7
6.8
—
—
C30H30N4
C30H28N4
19
161—162.5
(nꢀoctane)
81.3
81.1
6.5
6.4
19*
>150
(darkened)
234—236
66.2
66.1
5.5
5.4
6.7 C30H29ClN4O4
6.5
(decomp., MeCN)
21
22
199
235
63.4
63.7
5.4 (21.3) C31H29IN4
5.0 (21.7)
λ
max 425 nm. The reaction of alkene 3 with DPT afforded
aromatic product 17 (refluxing in benzene, 90 h, 74%).
(decomp., MeOH)
215
(blackened)
236
56.2
56.6
4.8
4.6
10.3 C31H30Cl2N4O8
10.8
(decomp., MeCN)
23*
260—262
(decomp., EtOH) 56.8
56.3
5.2
5.6
9.7 C18H21ClN2O5
9.3
* Perchlorate.
As can be seen from the reaction conditions, the reacꢀ
tivity of amine 3 appeared to be somewhat lower due to
the presence of only one electronꢀdonating group (see
below).
In our opinion, 1,8ꢀbis(dimethylamino)ꢀ4ꢀvinylꢀ
naphthalene (5)11 can be considered as an acyclic analog
of acenaphthylene 2 in which the ethylene fragment would
be expected to be less activated because it is remote from
the 8ꢀNMe2 group. We found that heating of "proton
sponge" 5 with one equivalent of tetrazine 6 (benzene,
30 h; oꢀxylene, 10 min) afforded 1,4ꢀdihydropyridꢀ
atmospheric oxygen). This fact indicates that dehydrogeꢀ
nation of dihydrodiazine 13 proceeded more difficultly
than that of its analog containing the phenyl groups, which
was even not detected in the reaction mixture. In spite of
this fact, the isolation of compound 13 presented difficulꢀ
ties because this compound gradually underwent aromaꢀ
tization both in air and solutions (process was completed
in 2—3 days).
We failed to use diazafluoranthenes 8 and 14 as the
starting compounds in the [4π+2π] cycloaddition reacꢀ

8,9ꢀDiazafluoranthene "proton sponges"
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 1, January, 2003
221
Table 2. Rate constants and relative rates (krel) of the reactions
of compounds 2—5 with symmꢀdiphenyltetrazine (6) at 21 °C
azine 18, which was isolated in individual form. The
1H NMR spectrum of compound 18 has a broadened
singlet at δ 9.3 belonging to the NH group as well as a
doublet for the H(4) proton and a doublet of doublets for
the H(5) proton at δ 5.4 (due to its coupling with the
proton of the NH group). After the addition of D2O, the
signal at δH 9.3 disappeared and the signal at δH 5.4 deꢀ
generated into a doublet, which confirms structure 18 and
is inconsistent with alternative structure 18a. The transꢀ
formation of compound 18 into aromatic pyridazine 19
required heating with chloranil (toluene, 100 °C, 10 min)
or with one more equivalent of DPT (oꢀxylene, 2 h)
(Scheme 3, see Table 1).
b
Comꢀ
pound
Solvent
k•103 a
/L mol–1 s–1
krel
2
2
3
4
5
CDCl3
CDCl2CDCl2
CDCl3
2.34
1.93
1.02
32
26
14
1
CDCl3
CDCl3
7.32•10–2
1.26
17
a The accuracy of determination was 5%.
b k(4) = 1.
tivities of the dienophiles in the series 5,6ꢀbis(dimethylꢀ
amino)acenaphthylene (2), 1,8ꢀbis(dimethylamino)ꢀ4ꢀ
vinylnaphthalene (5), 5ꢀdimethylaminoacenaphthylene
(3), and acenaphthylene (4) is 32 : 17 : 14 : 1 (Table 2).
The reactivities of these compounds to DPT in benzene
are comparable with those in xylene (2 : 3 : 4 — 68 : 23 : 1;
for the reaction conditions, see the Experimental section).
Therefore, the introduction of one NMe2 group at
position 5 leads to an increase in the reactivity of the
acenaphthylene system by more than an order of magniꢀ
tude, and the introduction of the second NMe2 group at
the peri position causes a further approximately twofold
increase in the reactivity. The reactivity of vinylnaphthaꢀ
lene 5 is intermediate between those of acenaphthylenes 2
and 3. The fact that the largest increase in the reactivity
occurs upon the insertion of the first NMe2 group is,
apparently, associated with steric hindrances in "proton
sponge" 2, which decrease the efficiency of conjugation of
each dimethylamino group with the π system of the ring.
At the same time, these results are inconsistent with other
data, which are indicative of dramatic changes in the
reactivities on going from 1ꢀdimethylaminonaphthalene
to 1,8ꢀbis(dimethylamino)naphthalene (1).1 Apparently,
this is attributed to the fact that the transition state of the
cycloaddition reaction under study is characterized by
low polarity and, consequently, it is poorly sensitive to
the resonance effect of the substituents.
Scheme 3
Therefore, the reactions of compound 5 differ from
those of acenaphthylenes 2—4, which either immediately
afford aromatic products or give dihydro forms (for exꢀ
ample, 13) that are readily oxidized. This behavior is typiꢀ
cal of many insufficiently activated alkenes whose cycloꢀ
adducts with tetrazines require additional aromatization
(for example, with K2Cr2O7—AcOH).12 Even the reacꢀ
tion of pꢀmethoxystyrene with ester 12 gave 1,4ꢀdihydroꢀ
pyridazine with the structure of type 18 resistant to atmoꢀ
spheric oxygen.13
It can be readily seen that cycloadducts 8, 14, 17,
and 19 prepared by us are pronounced pushꢀpull systems
in which the dimethylamino groups are efficiently conjuꢀ
gated with the pyridazine ring. This must lead to a subꢀ
stantial contribution of bipolar structures of types 8a and
8b to the resonance hybrid and, as a consequence, to a
decrease in the basicity of the NMe2 groups and an inꢀ
crease in the basicity of the pyridazine system (Scheme 4).
In this situation, in spite of high basicity typical of "proꢀ
ton sponges",2 it cannot be predicted with certainty that
the resulting cycloadducts would be protonated at the
dimethylamino groups rather than at the heterocycle. This
conclusion was confirmed by our studies performed with
The relative reactivities of compounds 2—5 were estiꢀ
mated by H NMR spectroscopic studies of their reacꢀ
1
tions with DPT in deuterated chloroform or 1,2ꢀdichloroꢀ
ethane. A series of spectra were recorded with the use
of all reagents taken at the initial concentrations of
6.78•10–2 mol L–1. The course of the reactions was folꢀ
lowed from a decrease in the concentration of alkene
until its conversion reached 25%. The ratio of the reacꢀ
1
the use of electronic absorption and H NMR spectroꢀ
scopy.

222
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 1, January, 2003
Pozharskii et al.
Scheme 4
It appeared that diazafluoranthene 8 in acetonitrile
(CD3CN) was protonated with one equiv. of HClO4 to
form the cation A in which the NMe2 groups are linked
through an intramolecular hydrogen bond (see Scheme 4).
The chemical shift of the proton of the NH group in this
cation is >16 ppm, and the signal of the dimethylamino
groups is observed as a doublet with the spinꢀspin couꢀ
3
pling constant J = 2.6 Hz (Table 3), which is also charꢀ
acteristic of cations of other "proton sponges" containing
the fiveꢀmembered ring at the peri positions of the naphꢀ
thalene ring.5
It should be noted that protonation of compound 8 in
acetonitrile (MeCN) was not visually accompanied by a
change in the color of the solution, although the UV
spectrum of salt 8•HClO4 substantially changed and beꢀ
came similar to the spectrum of diazafluoranthene 10
(Table 4). This is attributable to the presence of a low
concentration of unprotonated base 8, which masked the
color of the solution. Actually, the spectrum of salt
8•HClO4 has a lowꢀintensity longꢀwavelength band in
the visible region, which is observed as a shoulder in
virtually the same region as that of the corresponding
band of compound 8 (see Table 4). When the concentraꢀ
tion of perchlorate 8•HClO4 was 3•10–5 mol L–1, the
Table 3. Spectroscopic characteristics of the compounds synthesized
Comꢀ
pound
1H NMR spectrum
Other spectroscopic
propertiesa
Conditions
CD3CN
δ, J/Hz
3
3.09 (s, 6 Н, NMe2); 6.89 (d, 1 Н, H(4)); 6.94 (d, 1 Н, H(2));
7.52 (dd, 1 Н, H(7)); 7.58 (d,1 Н, H(3)); 7.69 (d, 1 Н, H(8));
7.01 (d, 1 Н, H(1)); 8.10 (d, 1 Н, H(6)); J1,2 = 5.2, J3,4 = 7.5,
J6,7 = 8.4, J7,8 = 6.9, J6,8 = 1.4
UV: 238 (sh, 4.18), 287 (3.59),
310 (3.56), 324 (3.62), 359 (3.54),
375 (sh, 3.49), 425 (3.43)
8
CDCl3
2.95 (s, 12 Н, NMe2); 6.89 (d, 2 Н, H(2), H(5)); 7.57 (m, 6 Н, Ph);
UV b
7.67 (d, 2 Н, H(1), H(6)); 7.92 (m, 4 H, Ph); J1,2 = 8.2
Fluorescence: 483 (excit.),
536 (fluor.)
8*c
CD3CN
3.21 (d, 12 Н, NMe2); 7.90 (m, 10 Н, 2 Ph); 8.06, 8.12 (both d,
2 H each, H(1), H(2), H(5), H(6)); 16.10 (m, 1 Н, NH); J1,2 = 8.0,
JNH,NMe = 2.6
UV b
DMSOꢀd6 3.09 (br.s, 12 Н, NMe2); 3.40 (br.s,
70 °С
H2O + H+); 7.27, 7.64 (both d, 2 H each, H(1), H(2), H(5), H(6));
7.78 (m, 6 Н, Ph); 7.96 (m, 4 Н, Ph); J1,2 = 9.0
10
14
DMSOꢀd6 7.74 (m, 10 Н); 7.95 (m, 4 Н); 8.26 (m, 2 Н)
UV b
DMSOꢀd6 3.03 (s, 12 Н, NMe2); 4.12 (s, 6 Н, OМе); 7.22 (d, 2 Н,
UV: 262 (4.19), 304 (4.00),
368 (4.14), 476 (sh, 429), 499
(4.45); (MeCN + HClO4) 238 (sh,
4.27), 313 (4.17), 333 (sh, 4.08),
411 (4.05), 513 (sh, 3.40)
IR: 1720 (СО); 1580, 1570, 1550,
1500 (ring)
H(2), H(5)); 8.55 (d, 2 Н, H(1), H(6)); J1,2 = 8.7
16
CDCl3
2.97 (s, 6 Н, NMe2); 3.40 (m, 4 Н, H(1), H(2)); 7.04 (d, 1 Н, H(4));
7.23, 7.32 (both br.d, 1 H each, H(3), H(8)); 7.50, 7.88 (both dd,
1 H each, H(6), H(7)); J3,4 = 7.4, J6,7 = 8.3, J7,8 = 7.0, J6,8 = 1.4
—
(to be continued)

8,9ꢀDiazafluoranthene "proton sponges"
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 1, January, 2003
223
Table 3 (continued)
Comꢀ
pound
1H NMR spectrum
δ, J/Hz
Other spectroscopic
propertiesa
Conditions
CDCl3
17
3.16 (s, 6 Н, NMe2); 6.81 (d, 1 Н, H(2)); 7.48 (dd, 1 Н, H(5));
7.60 (m, 6 Н, Ph); 7.65 (d, 1 Н, H(1)); 7.77 (br.d, 1 Н, H(6));
7.95 (m, 4 Н, Ph); 8.25 (br.d, 1 Н, H(4)); J1,2 = 8.0, J4,5 = 8.5,
J5,6 = 7.2, J4,6 = 0.9
UV: 248 (sh, 4.44), 278 (sh,
4.18), 328 (3.97), 468 (4.01)
Fluorescence: 481 (excit.),
546 (fluor.)
17*c
CD3CN
3.55 (s, 6 Н, NMe2); 6.50 (br.s, H2O + H+); 7.89 (m, 6 Н); 8.02 (m,
5 Н); 8.10 (m, 3 Н); 8.63 (d.d, 1 Н, H(4)), J4,5 = 7.9, J4,6 = 0.9
UV: 272 (4.30), 343 (4.05),
387 (4.04), 534 (3.25)
18
Acetoneꢀd6 2.71, 2.78 (both s, 6 H each, 4´ꢀ and 5´ꢀNMe2); 5.44 (d.d, 1 Н, H(5)); IR: 3305 (NH); 1605, 1590,
5.59 (d, 1 Н, H(4)); 6.81 (d, 1 Н, H(3´)); 7.06, 7.20—7.36, 7.50,
7.74 (all m, 2 Н, 6 Н, 3 Н, 2 Н, 2 Ph + H(2´), H(6´), H(7´));
8.06 (br.d, 1 Н, H(8´)); 9.25 (br.s, 1 Н, NH); J2´,3´ = 7.9,
1500 (ring)
J
6´,7´ = 7.6, J7´,8´ = 8.3, J4,5 = 5.7, JNH,5 = 2.3
19
CDCl3
2.80 (s, 12 Н, 4´ꢀ and 5´ꢀNMe2); 6.81 (d, 1 Н, H(3´)); 6.88 (br.d,
1 Н, H(6´)); 6.98—7.20, 7.47, 8.17 (all m, 6 Н, 5 Н, 2 Н, 2 Ph +
+ H(2´), H(7´), H(8´)); 7.90 (s, 1 Н, H(5)); J2´,3´ = 7.8, J6´,7´ = 7.4
UV: 250 (4.55), 278 (sh, 4.41),
358 (4.03)
19*c
CD3CN
3.11, 3.15 (both d, 6 H each, 4´ꢀ and 5´ꢀNMe2); 7.36, 7.48, 7.79,
8.22 (all m, 4 Н, 1 Н, 5 Н, 2 Н); 7.61 (t, 1 Н, H(7´)); 7.94 (br.d,
1 Н, H(6´)); 8.03 (d, 1 Н, H(3´)); 8.93 (s, 1 Н, H(5)); 18.72 (br.s,
1 Н, NH); J2´,3´ = 7.9, J6´,7´ = 7.6, JNH,4´ꢀNMe = 2.0, JNH,5´ꢀNMe = 2.8
—
DMSOꢀd6 3.12 (m, 12 Н, NMe2); 7.23, 7.36, 7.60, 8.29 (all m, 3 Н, 2 Н, 5 Н,
3 Н); 7.83, 8.18 (both d, 1 H each, H(2´), H(3´)); 8.09 (br.d, 1 Н,
H(6´)); 18.47 (br.s, 1 Н, NH); J2´,3´ = 7.9
21
CD3CN,
70 °С
3.06, 3.14 (both s, 6 H each, 3ꢀ and 4ꢀNMe2); 4.28 (s, 3 Н, N(8)Ме);
6.98, 7.10, 7.23 (all d, 1 H each, H(1), H(2), H(5));
7.70—8.00 (m, 11 Н, H(6) + 2 Ph); J1,2 = 8.9, J5,6 = 9.1
UV: 263 (sh, 4.20), 343 (4.11),
502 (sh, 4.19), 530 (4.38)
Fluorescence: 527 (excit.),
563 (fluor.)
DMSOꢀd6, 3.05, 3.14 (both s, 6 H each, 3ꢀ and 4ꢀNMe2); 4.28 (s, 3 Н, N(8)Ме);
100 °С
6.90, 7.14, 7.29 (all d, 1 H each, H(1), H(2), H(5));
7.70—8.00 (m, 11 Н, H(6) + 2 Ph); J1,2 = 8.9, J5,6 = 9.0
22
CD3CN
3.18 (m, 12 Н, NMe2); 4.45 (s, 3 Н, N(8)Ме); 7.11 (d, 1 Н,
H(6)); 7.90 (m, 11 Н, H(5) + 2 Ph); 8.10, 8.19 (both d, 1 H each,
H(1), H(2)); 16.07 (br.s, 1 Н, NH); J5,6 = 7.9, J1,2 = 8.0
UV: 270 (sh, 4.24), 339 (4.00),
391 (3.79), 485 (sh, 3.72),
519 (3.74)
23*c
CD3CN
2.65, 2.66, 3.59, 3.61 (all s, 3 H each, NMe); 2.30 (br.s,
OH + H2O); 2.81 (s, 3 Н, C(3)Ме); 7.09 (s, 1 Н, H(2));
7.48, 7.52, 8.35, 8.49 (all d, 1 H each, H(4), H(5), H(8), H(9));
J4,5 = J8,9 = 9.1
IR: 3400—3280 (OH); 1625,
1600, 1590, 1560, 1540,
1530 (ring)
DMSOꢀd6 2.62, 3.59 (both br.s, 6 H each, 6ꢀ and 7ꢀNMe2); 2.75 (s, 3 Н, C(3)Ме);
7.03 (s, 1 Н, H(2)); 7.51, 7.59, 8.32, 8.42 (all d, 1 H each, H(4), H(5),
H(8), H(9)); 11.70 (br.s, 1 Н, OH); J4,5 = J8,9 = 9.7
a UV (MeCN, λ/nm), IR (Nujol mulls, ν/cm–1), and fluorescence (MeCN, λ/nm) spectra.
b The UV spectrum is given in Table 4.
c Perchlorate.
degree of its deprotonation in acetonitrile reached 6%
(for 1,8ꢀbis(dimethylamino)ꢀ4ꢀnitronaphthalene perchloꢀ
rate (20), ≤ 1%).14 The aboveꢀconsidered data indicate
that the basicity of "proton sponge" 8 is at least an order of
magnitude lower than the basicity of pushꢀpull system 20
whose pKa in MeCN is 14.1.2 Interestingly, the solvatoꢀ
chromism which reflects the contribution of the polarized
structures of types 8a and 8b to neutral molecules 8 and
20 and is calculated as the difference ∆λmax between the
longꢀwavelength absorption bands on going, for example,
from highly polar DMSO to weakly
polar CHCl3 (dipole moments are
given in Table 4), is identical for both
compounds (20 nm for 8 and 21 nm
for 20).14
Since concentrations generally
used in 1H NMR spectroscopic studꢀ
ies are more than 1000 times higher than those used in
electronic absorption spectroscopy, the NMR spectrum
in acetonitrile detected nothing but the cation A.

224
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 1, January, 2003
Pozharskii et al.
Table 4. Electronic absorption spectra of compounds 8, 8•HClO4, and 10 in different solvents
a
Comꢀ
pound
Solvent
µ
Color
of solution
λ
max/nm (logε)b
/D
8
CHCl3
EtOH
1.1
1.7
3.5
3.9
3.5
1.7
1.7
3.5
Orange
Orange
Orange
Orange
Orange
Crimson
Yellow
Yellow
259 (4.48), 302c (4.04), 332 (3.98),
481 (4.25), 523c (3.04)
258 (4.41), 301c (3.98), 333 (4.00), 477c (4.23), 495 (4.27)
258 (4.46), 299c (4.06), 333 (4.05), 472c (4.29), 490 (4.34), 525c (3.68)
304c (4.07), 336 (4.06), 482c (4.31), 501 (4.37)
MeCN
DMSO
MeCN
MeOH
EtOH d
MeCN
8•HClO4
273 (4.31),
340 (4.01), 397 (4.04), 482c (3.18)
244 (4.22), 269 (4.23), 350 (3.98), 490c (3.94), 560 (4.25)
242 (4.65), 267c (4.24), 309 (4.00), 325 (3.99), 371 (4.06)
240 (4.74), 265c (4.26), 307 (4.00), 323 (3.99), 368 (4.03)
10
a The dipole moments of the solvents (benzene, 25 °C) were taken from the study.15
b The chargeꢀtransfer band (para band) is printed in bold type.
c Shoulder.
d This spectrum is somewhat different from that reported in the study7 for the same solvent (240 (4.71), 265 (4.30), 310 (4.00),
325 (4.00), 370 (3.07)).
The use of a substantially more basic dimethyl sulfoxꢀ
ide instead of MeCN for protonation of diazafluoranthene
8 led to the appearance of a brightꢀcrimson color,
which was also observed in alcohol (λmax 560 nm, see
Table 4) and in the solid state. The 1H NMR spectrum in
DMSOꢀd6 does not show a signal of the NH group at
δ 16; instead, the spectrum has a signal common to the
proton of the NH group and water at δ 3.6, whereas the
dimethylamino groups are manifested as a broad hump,
which is indicative of their weak involvement in the proꢀ
ton transfer (δ 3.1 compared to δ 3.2 in CD3CN). At
+70 °C, the aboveꢀmentioned hump is transformed into a
narrow singlet.
With the aim of determining the position of the proton
in the spectrum of a solution of perchlorate 8•HClO4
in DMSO, we prepared model compound 21. In the
solid state and in solutions (DMSO, EtOH, H2O, and
MeCN), this compound is bright redꢀcrimson in color
(λmax 530 nm, see Table 3) and is similar in color to a
solution of cation H+ꢀ8 in DMSO. In addition, solutions
of compound 21 exhibit greenishꢀyellow fluorescence (see
Table 3). In the 1H NMR spectrum of compound 21, the
dimethylamino groups are manifested as a hump, which
assumes a shape of two singlets only upon heating to
100 °C (DMSOꢀd6). Conceivably, such a behavior of the
NMe2 groups in salt 21 is associated with their involveꢀ
ment in delocalization of the positive charge (see, for
example, structure 21a). Apparently, this fact is also reꢀ
sponsible for a deep color of compound 21. From this
standpoint, cation H+ꢀ8 in DMSO and other basic solꢀ
vents is best described by the tautomeric form B (see
Scheme 4).
1H NMR spectroscopic study demonstrated that catꢀ
ion H+ꢀ8 did not undergo secondary protonation in
acetonitrile and DMSO (up to 10 equiv. of HClO4 were
added). By contrast, salt 21 in acetonitrile was protonated
with perchloric acid to form orange diperchlorate 22
(λmax 485 nm, δNH 16.1). In this case, the hypsochromic
shift is, apparently, associated with the fact that the NMe2
groups cannot be involved in delocalization of the posiꢀ
tive charge, like in structure 21a.
Therefore, in protic and/or basic solvents as well as in
the solid state, cycloadduct 8 adds a proton at the heteroꢀ
cycle (B), whereas cations H+ꢀ8 in acetonitrile occur in
the form A. Unfortunately, we failed to grow crystals of
salt 8•HClO4 suitable for Xꢀray diffraction analysis beꢀ
cause this salt is characterized by hygroscopicity and low
hydrolytic stability.
Compound 8 is the first example of "proton sponges"
capable of adding a proton at positions other than the
NMe2 groups. In searching for other analogous systems,

8,9ꢀDiazafluoranthene "proton sponges"
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 1, January, 2003
225
we examined phenalenone (23), which has been described
earlier.16 It is known17 that both phenalenone and its
heterocyclic derivatives of type 24 are protonated excluꢀ
sively at the carbocyclic carbonyl group to give resonanceꢀ
stabilized cations.
Under the action of one equiv. of HClO4, diazaꢀ
fluoranthene 17 forms cation H+ꢀ17 even in acetonitrile.
In this cation, the proton is located at the azine moiety of
the molecule (like in the structure B). The formation of
this cation is evidenced by a change in the color of the
compound from orange to crimsonꢀviolet (λmax 534 nm)
and the fact that the signals for all protons in its 1H NMR
spectrum are shifted downfield by ∼0.5 ppm compared to
those observed in the spectrum of base 17 (see Table 3).
Solutions of pyridazine 17 exhibit yellowꢀgreen fluoresꢀ
cence (λmax of fluorescence is 546 nm; the Stokes shift is
65 nm). It should be noted that fluorescence of diamine 8
is observed at a somewhat lower wavelength (536 nm; the
Stokes shift is 53 nm) due to spatial periꢀinteractions beꢀ
tween the dimethylamino groups.
Interestingly, yellow diazafluoranthene 10 devoid of
the alkylamino groups is insoluble in HCl (20%) or H2SO4
(50%) but is soluble in concentrated H2SO4, the solution
developing a brown color.
We found that "proton sponge" 23 adds a proton at the
carbonyl group both in DMSO and MeCN with the only
difference that the OH group generated in DMSO is inꢀ
volved in hydrogen bonding with the solvent (δ(OH) 11.7),
whereas this group does not form hydrogen bonds with
MeCN (δ(OH) 2.3). As a result, the resonance interacꢀ
tions of the NMe2 groups with the phenalenium system
are stronger in acetonitrile than in DMSO. Actually, due
to the unsymmetrical structure of the cation C as a whole
and because of flattening of the positively charged diꢀ
methylamino groups, the 1H NMR spectrum of salt
23•HClO4 in MeCN shows individual signals for all NMe
groups, whereas only broadening of the peaks of the NMe2
groups is observed in the spectrum in DMSO at 20 °C (by
analogy with compounds 8•HClO4 and 21, see Table 3).
Therefore, the resonance stabilization ensures a larger
gain in energy compared to that provided by the intramoꢀ
lecular hydrogen bond in the cation D whose formation
was not detected (1H NMR spectra have no signals at
δH >15 and the IR spectrum shows no C=O stretching
bands).
Protonation of compound 19 both in MeCN and
DMSO proceeded exclusively at the 1,8ꢀbis(dimethylꢀ
amino)naphthalene fragment to give cation H+ꢀ19
(δNH >18.5). Apparently, this direction of protonation is
to a large extent determined by acoplanarity of the naphꢀ
thalene and pyridazine rings, which reduces their mesoꢀ
meric interaction.*
Due to the lower basicity of compound 14 (compared
to 8), it does not form stable salts with acids and, hence,
its protonation was not studied. However, its UV specꢀ
trum in acetonitrile with an addition of perchloric acid
showed (see Table 2) that protonation in this case also
proceeded with the involvement of the NMe2 groups
(transformation 14 → H+ꢀ14 led to a substantial hypsoꢀ
chromic shift of the longꢀwavelength absorption band,
To summarize, we demonstrated that 5,6ꢀbis(diꢀ
methylamino)acenaphthylene can be used as a building
* In the case of 1,8ꢀbis(dimethylamino)ꢀ4ꢀpicrylnaphthalene
trifluoroacetate containing a slightly asymmetrical intramolecuꢀ
lar hydrogen bond, the acoplanarity of the trinitrophenyl group
and the naphthalene ring is so high (∼70°) that virtually only the
inductive component of the electronꢀwithdrawing effect of this
group persists.18
λ
max 499 (logε 4.45) → 411 (4.05) nm).

226
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 1, January, 2003
Pozharskii et al.
was dissolved in MeOH (2 mL) and then iodomethane
(0.015 mL, 0.24 mmol) was added with a microsampler. The
resulting solution was kept at 22 °C for 7 days. The alcohol was
distilled off. Compound 21 was obtained as darkꢀclaret crystals
in a yield of 0.04 g (94%).
3,4ꢀBis(dimethylamino)ꢀ7,10ꢀbis(methoxycarbonyl)ꢀ8,9ꢀdiꢀ
azafluoranthene (14). A solution of tetrazine 12 (0.08 g,
0.4 mmol) in CH2Cl2 (4 mL) was added portionwise to a soluꢀ
tion of acenaphthylene 2 (0.048 g, 0.2 mmol) in CH2Cl2 (4 mL)
(gas evolution). After 5 min, the solvent was evaporated and the
residue was dissolved in CHCl3. The solution was kept at 15 °C
for 3 days, the solvent being slowly evaporated until aromatizaꢀ
tion of the dihydro form was completed. The residue was crysꢀ
tallized from toluene. Compound 14 was obtained in a yield of
0.07 g (85%) as darkꢀbrown crystals with a green tint.
5ꢀAminoacenaphthene was prepared according to a known
procedure.21 1H NMR (CDCl3), δ: 3.35 (m, 4 H, H(1), H(2));
4.15 (br.s, 2 H, NH2); 6.81 (d, 1 H, H(4)); 7.08 (br.d, 1 H,
H(3)); 7.25 (br.d, 1 H, H(8)); 7.40 (t, 1 H, H(7)); 7.54 (br.d,
1 H, H(6)); J3,4 = 7.3 Hz, J6,7 = 8.2 Hz, J7,8 = 6.8 Hz.
5ꢀDimethylaminoacenaphthene (16). Dimethylformamide
(20 mL) was added to 5ꢀaminoacenaphthene (1.5 g, 0.01 mol)
and the reaction mixture was stirred under nitrogen until the
compound was dissolved (5 min). Then finely dispersed KOH
(1.3 g, 0.023 mol) was added. After 5 min, MeI (2.2 mL,
0.035 mol), which was cooled to 0 °C, was added portionwise.
The reaction mixture was stirred at ∼20 °C for 1 h and then at
70 °C for 1 h, cooled to 20 °C, and diluted with water (100 mL).
Then a 10% KOH solution (5 mL) was added. Acenaphthene 16
that formed was extracted with light petroleum (6×50 mL) and
the solvent was removed. A paleꢀbrown oil was obtained in a
yield of 1.46 g (74%).
5ꢀDimethylaminoacenaphthylene (3). A solution of compound
16 (0.5 g, 2.4 mmol) in benzene (10 mL) was mixed with a
solution of chloranil (0.66 g, 2.7 mmol) in benzene (10 mL).
The resulting solution was refluxed for 30 min and the benzene
was distilled off. The residue was chromatographed (Al2O3 (II),
CHCl3), and the first brightꢀorange fraction was collected
(Rf 0.93, CHCl3). Compound 3 was obtained as a darkꢀorange
oil in a yield of 0.22 g (44%).
3ꢀDimethylaminoꢀ7,10ꢀdiphenylꢀ8,9ꢀdiazafluoranthene (17).
A solution of tetrazine 6 (0.082 g, 0.4 mmol) and acenaphthylene
3 (0.04 g, 0.2 mmol) in benzene (10 mL) was refluxed for 90 h.
The solvent was removed, the residue was chromatographed
(Al2O3 (III), CHCl3), and the brightꢀorange fraction was colꢀ
lected (Rf 0.15, CHCl3). Compound 17 was obtained as a redꢀ
orange substance in a yield of 0.06 g (74%).
7,10ꢀDiphenylꢀ8,9ꢀdiazafluoranthene (10) was obtained from
acenaphthylene 4 and tetrazine 6 as described earlier.7 This
compound was obtained as yellow crystals. Its m.p. and 1H NMR
spectrum were measured in the present study for the first time
(see Table 4).
4ꢀ[4,5ꢀBis(dimethylamino)naphthalenꢀ1ꢀyl]ꢀ3,6ꢀdiphenylꢀ
1,4ꢀdihydropyridazine (18). 1,8ꢀBis(dimethylamino)ꢀ4ꢀvinylꢀ
naphthalene (5)11 (816 mg, 3.4 mmol) and tetrazine 6 (796 mg,
3.4 mmol) were fused together at 120 °C for 10 min (gas evoluꢀ
tion). Then oꢀxylene (4 mL) was added and the reaction mixture
was refluxed for 10 min until the pink color of the tetrazine
disappeared. The solution was cooled to 20 °C and kept for 12 h.
Then the paleꢀyellow crystals of 3,6ꢀdiphenylꢀ1,4ꢀdihydroꢀ
1,2,4,5ꢀtetrazine19 that formed (220 mg, 27%) were filtered off.
block for the construction of new molecular systems, synꢀ
thesized "proton sponges" with the diazafluoranthene skelꢀ
eton, and showed that these compounds can change the
site of protonation depending on the solvent. The quantiꢀ
tative data on the reactivities of "proton sponges" were
obtained for the first time and these data were compared
with the corresponding data for a series of their close
analogs.
Experimental
The 1H NMR spectra were recorded on Bruker DPXꢀ250
(250 MHz) and Unityꢀ300 (300 MHz) instruments with SiMe4
as the internal standard. The kinetic measurements were carried
1
out by H NMR spectroscopy in CDCl3; the initial concentraꢀ
tions of all reagents were 6.78•10–2 mol L–1. The UV spectra
were measured on a Specord Mꢀ40 spectrophotometer. The fluoꢀ
rescence spectra were recorded on a Shimadzu RF 5001 PC
instrument. The IR spectra were measured on a Specord IRꢀ75
spectrometer. Chromatography was carried out on columns with
Al2O3 (for activity grade according to Brockmann, see below)
and on silica gel L40/100 µm (Chemapol). The course of the
reactions and purities of the resulting compounds were moniꢀ
tored by TLC on Al2O3 and Silufol plates; visualization was
carried out with iodine vapor. The melting points were meaꢀ
sured in sealed glass tubes and were not corrected. The physicoꢀ
chemical characteristics of the resulting compounds are given in
Tables 1, 3, and 4.
5,6ꢀBis(dimethylamino)acenaphthylene (2),5 3,6ꢀdiphenylꢀ
1,2,4,5ꢀtetrazine (6),19 dimethyl symmꢀtetrazineꢀ3,6ꢀdicarbꢀ
oxylate (12),13 and phenalenone 23 16 were prepared according
to procedures published earlier. Acenaphthylene 4 was prepared
according to a modified procedure.20 Benzene and xylene were
dried with sodium metal and distilled. Acetonitrile and dimethyl
sulfoxide were purified and dried according to standard proceꢀ
dures. Their deuterated analogs (CD3CN and DMSOꢀd6),
CDCl3, and CDCl2CDCl2 were used without additional purifiꢀ
cation (the contents of the major components were no lower
98%, the deuterium content was no lower than 99.7%, Izotop,
St. Petersburg).
3,4ꢀBis(dimethylamino)ꢀ7,10ꢀdiphenylꢀ8,9ꢀdiazafluoranthene
(8). A. A solution of symmꢀdiphenyltetrazine (0.096 g, 0.4 mmol)
in C6H6 (5 mL) was mixed with a solution of acenaphthylene 2
(0.048 g, 0.2 mmol) in benzene (5 mL). The resulting mixture
was refluxed for 30 h, concentrated to a minimum volume, and
chromatographed (Al2O3 (V), CHCl3), the brightꢀorange zone
being collected (Rf 0.20, CHCl3). Compound 8 was obtained as
brown crystals with a green tint in a yield of 0.084 g (94%).
B. A mixture of acenaphthene 11 (0.048 g, 0.2 mmol),9
diphenyltetrazine 6 (0.14 g, 0.6 mmol), and DMSO (6 mL) was
refluxed under argon for 6.5 h. Then the hot reaction mixture
was diluted with water (10 mL) and extracted with benzene
(3×6 mL). The extract was concentrated to a minimum volume
and then treated as described in the method A. Diazafluoranthene
8 was isolated in a yield of 0.024 g (27%). The physicochemical
properties of compound 8 were identical with those of the sample
prepared according to the method A.
3,4ꢀBis(dimethylamino)ꢀ8ꢀmethylꢀ7,10ꢀdiphenylꢀ8,9ꢀdiazaꢀ
fluoranthenium iodide (21). Compound 8 (0.032 g, 0.072 mmol)

8,9ꢀDiazafluoranthene "proton sponges"
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 1, January, 2003
227
The filtrate was concentrated at 20 °C to the volume of 1.5 mL
and a heavy white precipitate was separated by washing with
cold toluene (1 mL) and cold CCl4 (2 mL). A white finely
crystalline powder of compound 18 was obtained in a yield of
210 mg (13%). After isolation of the products, the residue was
not separated and analyzed.
4. N. V. Vistorobskii, A. F. Pozharskii, S. V. Shorshnev, and
A. I. Chernyshev, Mendeleev Commun., 1991, 10; A. F.
Pozharskii, N. G. Tregub, E. Yu. Romanova, Z. A. Starikova,
and A. I. Yanovsky, Izv. Akad. Nauk, Ser. Khim., 1999, 1311
[Russ. Chem. Bull., 1999, 48, 1299 (Engl. Transl.)]; A. F.
Pozharskii, O. V. Ryabtsova, N. V. Vistorobskii, and Z. A.
Starikova, Izv. Akad. Nauk, Ser. Khim., 2000, 1103 [Russ.
Chem. Bull., Int. Ed., 2000, 49, 1097].
5. V. A. Ozeryanskii, A. F. Pozharskii, G. R. Milgizina, and
S. T. Howard, J. Org. Chem., 2000, 65, 7707.
6. A. Schönberg and N. Latif, J. Chem. Soc., 1952, 446; H. S.
Tucker, J. Chem. Soc., 1958, 1462; D. C. Morrison, J. Org.
Chem., 1960, 25, 1665.
7. T. Sasaki, K. Kanematsu, and T. Hiramatsu, J. Chem. Soc.,
Perkin Trans. 1, 1974, 1213.
8. R. E. Sammelson, M. M. Olmstead, M. J. Haddadin, and
M. J. Kurth, J. Org. Chem., 2000, 65, 9265.
9. V. A. Ozeryanskii and A. F. Pozharskii, Izv. Akad. Nauk,
Ser. Khim., 2000, 1405 [Russ. Chem. Bull., Int. Ed., 2000,
49, 1399].
10. R. Nesi, D. Giomi, S. Turchi, and A. Falai, J. Chem. Soc.,
Chem. Commun., 1995, 2201.
11. N. V. Vistorobskii and A. F. Pozharskii, Izv. Akad. Nauk,
Ser. Khim., 1996, 2297 [Russ. Chem. Bull., 1996, 45, 2181
(Engl. Transl.)].
12. M. Avram, I. G. Dinulescu, E. Marica, and C. D.
Nenitzescu, Chem. Ber., 1962, 95, 2248.
13. J. Sauer, A. Mielert, D. Lang, and D. Peter, Chem. Ber.,
1965, 98, 1435.
14. A. F. Pozharskii, V. V. Kuz´menko, G. G. Aleksandrov, and
D. V. Dmitrienko, Zh. Org. Khim., 1995, 31, 570 [Russ.
J. Org. Chem., 1995, 31 (Engl. Transl.)].
15. O. A. Osipov, V. I. Minkin, and A. D. Garnovskii,
Spravochnik po dipol'nym momentam [Reference Manual on
Dipole Moments], Vysshaya Shkola, Moscow, 1971, 416 pp.
(in Russian).
16. N. V. Vistorobskii and A. F. Pozharskii, Zh. Org. Khim.,
1991, 27, 1543 [J. Org. Chem. USSR, 1991, 27 (Engl.
Transl.)].
17. I. V. Borovlev and A. F. Pozharskii, Khim. Geterotsikl.
Soedin., 1978, 833 [Chem. Heterocycl. Compd., 1978 (Engl.
Transl.)].
18. J. Klimkiewicz, M. Koprowski, L. Stefaniak, E. Grech, and
G. A. Webb, J. Mol. Struct., 1997, 163; K. Wozniak, H. He,
J. Klinowski, T. L. Barr, and S. E. Hardcastle, J. Phys.
Chem., 1996, 100, 11408.
4ꢀ[4,5ꢀBis(dimethylamino)naphthalenꢀ1ꢀyl]ꢀ3,6ꢀdiphenylꢀ
pyridazine (19). A. Vinylnaphthalene 5 (0.096 g, 0.4 mmol) and
tetrazine 6 (0.187 g, 0.8 mmol) were fused together at 120 °C for
10 min (gas evolution). Then oꢀxylene (3 mL) was added and the
reaction mixture was refluxed for 2 h until the pink color of the
tetrazine disappeared. The solution was kept at 5 °C for 12 h.
3,6ꢀDiphenylꢀ1,4ꢀdihydroꢀ1,2,4,5ꢀtetrazine was separated in a
yield of 0.092 g (97%). The xylene was removed from the filꢀ
trate, and the residue was mixed with chloroform (2 mL) and
Al2O3 (1 g). Then the mixture was kept for 5 h to achieve
complete oxidation of the traces of diphenyldihydrotetrazine
(its chromatographic mobility is identical with that of product
19) to tetrazine 6. The resulting mixture was chromatographed
(Al2O3 (II), CHCl3), and the paleꢀyellow fraction was collected
(Rf 0.33, CHCl3). Yellow pyridazine 19 was obtained in a yield
of 0.162 g (88%). This compound crystallized by concentration
of its solution in nꢀoctane.
B. A mixture of dihydrodiazine 18 (45 mg, 0.1 mmol),
chloranil (25 mg, 0.1 mmol), and toluene (1 mL) was heated at
100 °C for 10 min. After cooling, the reaction mixture was
chromatographed as described above. Aromatic product 19 was
obtained in a yield of 35 mg (79%). The physicochemical propꢀ
erties of the aromatic product were identical with those of the
sample prepared according to the procedure A.
Synthesis of perchlorates (general procedure). An equimolar
amount of 70% HClO4 was added with the use of a microsampler
to a solution of the corresponding compound (0.1 mmol) in
MeCN (2 mL). The solvent was removed in vacuo. The residue
was washed with ether and crystallized if necessary. Salts
8•HClO4 (small darkꢀclaret crystals), 17•HClO4 (brownꢀred
crystals), 19•HClO4 (paleꢀyellow crystals), and 23•HClO4
(darkꢀclaret crystals) were obtained in quantitative yields. An
orange powder of compound 22 as diperchlorate was prepared
by the reaction of iodide 21 with a fivefold excess of 70% HClO4.
This study was financially supported by the Minisꢀ
try of Education of the Russian Federation (Grant
E00ꢀ5.0ꢀ25).
References
19. A. F. Pozharskii, V. A. Anisimova, and E. B. Tsupak,
Prakticheskie raboty po khimii geterotsiklov [Laboratory
Manual on Chemistry of Heterocycles], Izdꢀvo Rostovskogo
Universiteta, 1988, 44 (in Russian).
20. H. Miyamoto, K. Yui, Y. Aso, T. Otsubo, and F. Ogura,
Tetrahedron Lett., 1986, 27, 2011.
1. O. V. Vinogradova, A. F. Pozharskii, and Z. A. Starikova,
Izv. Akad. Nauk, Ser. Khim., 2003, 196 [Russ. Chem. Bull.,
Int. Ed., 2003, 52, 208].
2. A. F. Pozharskii, Usp. Khim., 1998, 67, 3 [Russ. Chem. Rev.,
1998, 67, 1 (Engl. Transl.)].
3. L. A. Kurasov, A. F. Pozharskii, V. V. Kuz´menko, N. A.
Klyuev, A. I. Chernyshev, S. S. Goryaev, and N. L. Chikina,
Zh. Org. Khim., 1983, 19, 590 [J. Org. Chem. USSR, 1983, 19
(Engl. Transl.)]; N. V. Vistorobskii and A. F. Pozharskii,
Zh. Org. Khim., 1989, 25, 2154 [J. Org. Chem. USSR, 1989,
25 (Engl. Transl.)].
21. M. M. Dashevskii, Atsenaften [Acenaphthene], Khimiya,
Moscow, 1966, 102 (in Russian).
Received April 18, 2002;
in revised form November 4, 2002