peri-naphthylenediamines. 38. Naphthalene and acenaphthene "proton sponges" with +M substituents in ortho positions with respect to peri-dimethylamino groups

Article abstract of DOI:10.1023/B:RUCB.0000030818.70534.6b

Previously unknown 4,5,6,7-tetrakis(dimethylamino)acenaphthene, which is the first acenaphthene derivative containing four vicinal dialkylamino groups, was synthesized based on 5,6-bis(dimethylamino)-4,7-dinitroacenaphthene. The total synthesis of 1,2,7,8

Full text of DOI:10.1023/B:RUCB.0000030818.70534.6b

404
Russian Chemical Bulletin, International Edition, Vol. 53, No. 2, pp. 404—414, February, 2004
periꢀNaphthylenediamines
38.* Naphthalene and acenaphthene "proton sponges" with
+M substituents in ortho positions with respect to periꢀdimethylamino groups
V. A. Ozeryanskii,ꢀ V. I. Sorokin, and A. F. Pozharskii
Rostov State University,
7 ul. Zorge, 344090 RostovꢀonꢀDon, Russian Federation.
Fax: +7 (863 2) 22 3958. Eꢀmail: vv_ozer2@chimfak.rsu.ru
Previously unknown 4,5,6,7ꢀtetrakis(dimethylamino)acenaphthene, which is the first
acenaphthene derivative containing four vicinal dialkylamino groups, was synthesized based on
5,6ꢀbis(dimethylamino)ꢀ4,7ꢀdinitroacenaphthene. The total synthesis of 1,2,7,8ꢀtetraꢀ
kis(dimethylamino)naphthalene was carried out starting from 3,6ꢀdinitronaphthalic anhydride.
Other "proton sponges" of this type, viz., 1,7,8ꢀtris(dimethylamino)ꢀ2ꢀmethoxyꢀ and
1,8ꢀbis(dimethylamino)ꢀ2,7ꢀdipiperidinonaphthalenes, were prepared by the nucleophilic subꢀ
stitution in 2,7ꢀdimethoxyꢀ1,8ꢀdinitronaphthalene. In solutions, 1,2,7,8ꢀtetrakis(dimethylꢀ
amino)naphthalene and its analogs can form diꢀ and trications in the presence of acids. The
1
basicity constants рKa of the compounds measured in DMSO depend in a complex way on
their structures but correlate with the basicity index B, which is determined by changes in the
chemical shifts δ after the addition of the first proton. Due to low Cꢀnucleophilicity of
H
orthoꢀdisubstituted "proton sponges" in combination with high basicity, these compounds hold
considerable promise as reagents in organic synthesis.
Key words: acenaphthene, 1,8ꢀdinitronaphthalene, nucleophilic substitution, catalytic hyꢀ
drogenation, alkylation, "proton sponge", basicity, protonation, nitration, azoꢀcoupling.
1,8ꢀBis(dimethylamino)naphthalene
("proton
as from the standpoint of organic chemistry as such. In
addition, protic salts of compound 1b have recently been
proposed as models for studying the types of intramolecuꢀ
lar hydrogen bonds.12 In the present study, we developed
a convenient procedure for the synthesis of "proton
sponges" 1b and 1c and some their close analogs, includꢀ
ing the first derivative containing simultaneously the
alkoxy and amino groups in the ortho positions. We also
studied the characteristic features of protonation of these
compounds, the relationship between their structure and
basicity, and their behavior in nitration and azoꢀcoupling
reactions.
sponge," 1a) and its 2,7ꢀdimethoxy (1b) and 2,7ꢀbis(diꢀ
methylamino) derivatives (1c) are of interest2—5 because
of their record high basicity (for example, рKa for comꢀ
pounds 1a and 1b are 12.1 and 16.1, respectively, in the
H2O scale)5—8 in combination with rather simple strucꢀ
tures.
Synthesis. Earlier, we have demonstrated that the
oꢀnitro group can be transformed into the oꢀNMe2 group
in 1,8ꢀbis(dimethylamino)naphthalene derivatives by
catalytic hydrogenation (Pd/C) followed by alkylation
(MeI—KOH—DMF). In particular, this method was used
for the preparation of triamine 2 in a total yield of 81%.13
In the present study, we used this approach for the synꢀ
thesis of diamine 3b (100%) starting from rather readily
accessible dinitroacenaphthene 3a (see Ref. 14). Methyꢀ
lation of diamine 3b in an MeI—KOH—DMF system
afforded derivative 3c (37%).
R = H (a), OMe (b), NMe2 (c),
(d),
(e)
Although the properties of the parent compound of
this series, viz., compound 1a, have been investigated in
considerable detail, derivatives 1b and 1c remain poorly
studied, primarily, because they are difficultly accessible.
Earlier, the properties of 1b and 1c have been considered
only theoretically.9—11 However, the nature of the unusuꢀ
ally high basicity of compounds 1b and 1c is of interest
from the viewpoint of the theory of acids and bases as well
However, alkylation with dimethyl sulfate
((MeO)2SO2—Na2CO3—H2O), which we have successꢀ
* For Part 37, see Ref. 1.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 388—397, February, 2004.
1066ꢀ5285/04/5302ꢀ0404 © 2004 Plenum Publishing Corporation

orthoꢀDisubstituted "proton sponges"
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 2, February, 2004
405
Although we succeeded in increasing the yield of the
key dinitrodiaminonaphthalene 7, whose synthesis from
diamide 6 has been described earlier (47% yield, see
Ref. 18), to 88%, attempts to perform its exhaustive
Nꢀmethylation failed. Diamine 7 remained intact under
the action of (MeO)2SO2—K2CO3—DMF (100 °C, 50 h)
or MeI—K2CO3—Me2NAc (50—60 °C, 30 h) systems.
The reactions with the use of MeI—KOH—DMSO (30 °C,
24 h) or MeI—K2CO3—MeOH (65 °C, 33 h) systems led
to resinification of the starting diamine 7 due, apparently,
to the competitive nucleophilic substitution of the nitro
groups. Partially methylated product 8 was prepared in a
yield of no higher than 20% only with the use of a
MeI—K2CO3—DMF mixture (50—60 °C, 30 h). Prodꢀ
uct 8 is stabilized by an intramolecular hydrogen bond
(νNH 3360 cm–1, δH(NH) 8.0), which, along with
increasing steric requirements, can hinder its further
alkylation. We succeeded in obviating this problem by
subjecting nitronaphthylamine 7 to hydrogenation folꢀ
lowed by exhaustive alkylation of tetraamine 10 with the
(MeO)2SO2—Na2CO3—H2O system. Analogously, comꢀ
pound 1c can also be prepared starting from methylamino
derivative 8 without isolation of polyamine 9 (the yield
was 33% with respect to dinitro derivative 8).
R = NO2 (a), NH2(b), NMe2 (c)
fully used earlier,15—17 proved to be a method of choice
for performing the transformation 3b → 3c. Since
Nꢀnucleophilicity of the amino groups at the C(4)
and C(7) atoms in amine 3b should be high, whereas
NHꢀacidity, on the contrary, should be low, the use of
superbasic systems, which generate readily oxidizable
Nꢀanions, is inefficient, whereas the reaction with the use
of the (MeO)2SO2—Na2CO3—H2O mixture afforded
peralkylated polyamine 3c in a yield of >63% through the
successive quaternization—deprotonation steps (the deꢀ
tails of the use of this alkylating system are reported for
the first time in the present study; see the Experimental
section).
The evident precursor of "proton sponge" 1c, viz.,
1,8ꢀbis(dimethylamino)ꢀ2,7ꢀdinitronaphthalene (analog
of compound 3a), is difficult to prepare.14 Hence, we
developed an alternative procedure for the preparation of
compound 1c from 3,6ꢀdinitronaphthalic anhydride (4)
(Scheme 1). In spite of the fact that this procedure
involves many steps, it is characterized by high reliꢀ
ability and good yields (seven steps, the total yield is
10—15%).
It should be emphasized that the fourꢀstep synthesis of
1,2,7,8ꢀtetrakis(dimethylamino)naphthalene (1c) deꢀ
scribed earlier3 afforded the target product in a yield of as
low as 4% due, primarily, to complications in the methyꢀ
lation step (Scheme 2).
We demonstrated that the use of the
(MeO)2SO2—Na2CO3—H2O system instead of
Scheme 1

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Russ.Chem.Bull., Int.Ed., Vol. 53, No. 2, February, 2004
Ozeryanskii et al.
Scheme 2
Table 1. Nucleophilic substitution in 2,7ꢀdimethoxyꢀ1,8ꢀdinitroꢀ
naphthalene (11) in the presence of secondary alkylamines
Run
HNR2
τ
Composition of the reaction
mixture (%)
Referꢀ
ence
/day
11
A
B
Resins*
3
1
HNMe2 **
7
90 (13)
0
***
2
3
HNMe2
3
4
0
0
0
0
84 (12a)
90 (12b)
16
10
3
3
4
7
10
8
32 (12c)
50
***
* Products of unknown composition.
** 3 h.
12a → 1c
12b → 1d
12c → 1e
*** The present study.
11 → 1b
Under the same conditions, 1,8ꢀdinitronaphthalenes conꢀ
taining primary (7) or secondary (8) oꢀamino groups as
well as dimethoxynaphthalene 11 remain intact.
1: R = OMe (b), NMe2 (c), N(CH2)4 (d), N(CH2)5 (e)
12: R = Me (a, 84%)3; R2 = (CH2)4 (b, 90%)3; (CH2)5 (c, 32%)
Dinitronaphthalenes prepared in this step were transꢀ
formed into new "proton sponges" 14 and 1e in 61 and
39% yields, respectively, by catalytic hydrogenation and
alkylation with dimethyl sulfate. 2,7ꢀDipyrrolidine deꢀ
rivative 1d has been characterized earlier3 by Xꢀray difꢀ
fraction analysis and its рKa has been determined; howꢀ
ever, the yield, spectroscopic characteristics, and physiꢀ
cal properties of 1d have not been reported. We prepared
(in 48% yield) and completely characterized this comꢀ
pound (see the Experimental section).
(MeO)2SO2—NaH for methylation led to an increase in
the total yield of compound 1c from 5 to 40%. Moreover,
the analogous transformation 11 → 1b afforded the target
product in a yield of up to 70% (earlier,2 the efficiency of
this transformation was lower than 20%).
Other "proton sponges" 1d,e can be prepared by varyꢀ
ing secondary alkylamine in the step of nucleophilic subꢀ
stitution of the methoxy groups in dinitronaphthalene 11.
Earlier,3 this reaction was carried out with the use of
dimethylamine and pyrrolidine. The results of the reacꢀ
tions of these and other dialkylamines with dimethoxy
derivative 11 are presented in Table 1.
As can be seen from this table, the percentage of exꢀ
haustive substitution products decreases in the series
pyrrolidine ≈ dimethylamine > piperidine (see Table 1,
runs 2 and 4). The latter reaction is accompanied by subꢀ
stantial resinification. We
succeeded in preparing parꢀ
tial substitution product 13
containing the methoxy
and dimethylamino groups
in the ortho positions of the
naphthalene system in high
yield by decreasing the reꢀ
action time (see Table 1, run 1).
Nitronaphthylamines 12a—c and 13 containing terꢀ
tiary arylamino groups are sensitive to light. When exꢀ
posed to UV light or sunlight, these compounds turn black
both in solution and in the solid state within a few hours.
Protonation. "Proton sponges" 1a—d, 3b,c, and 14 are
polyacidic bases, which can add several protons (concenꢀ
trated HBr, HClO4, and HBF4 were used). The first proꢀ
ton is coordinated to the periꢀNMe2 groups (Scheme 3)

orthoꢀDisubstituted "proton sponges"
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 2, February, 2004
407
to form the cation D with an intramolecular hydrogen
bond. This cation is classical for "proton sponges".5 For
the cations D, the signals of the periꢀNMe2 groups are
shifted downfield by 0.4—0.5 ppm and turn into doublets
due to spinꢀspin coupling with the proton of the NH
stable cation D. This assumption is confirmed by the folꢀ
lowing observations. Under homogeneous conditions
(MeCN, MeOH, or DMF), a monoprotonated salt of the
type D can be prepared in the individual form by adding
one equivalent of mineral acid to the "proton sponges"
under study followed by careful removal of the solvent.
By contrast, under heterogeneous conditions (hexane,
benzene, or Et2O), the addition of even one equivalent of
acid led to the rapid formation of a precipitate, which
virtually completely consisted of diprotonated salt E.
In the presence of an excess of acid, protonation of
compound 14 afforded the dication E (R = Me, Y = OMe)
as the final product. The other "proton sponges" gave the
trications F (see Scheme 3). It is noteworthy that the
1H NMR spectroscopic characteristics of the trication
3b•3H+, unlike those of the monocation 3b•H+, are simiꢀ
lar to those of salt 15 (Scheme 4, Table 3).
1
group; the latter appears in the H NMR spectrum as a
broadened singlet or a multiplet (depending on the symꢀ
metry of the cation) at δ 18—20 (see the Experimental
section and Table 2).19
Scheme 3
Scheme 4
i. Proton transfer
There are grounds to suppose that in the reactions of
acids with orthoꢀaminoꢀsubstituted "proton sponges," the
first proton rapidly adds to the more accessible βꢀamino
group to form the cation C. In solution, the latter is irreꢀ
versibly rearranged into the thermodynamically more
Another distinguishing feature of "proton sponges"
containing orthoꢀamino substituents is that the constant
JNH,NMe gradually decreases with increasing amount of
the acid added to solutions of the "proton sponges" in
acetonitrile. In the course of this process, the chemical
shift of the chelated proton δNH first sharply decreases
Table 2. Chemical shifts (δ ) of selected fragments of orthoꢀdiꢀ
H
substituted "proton sponges" in the neutral and protonated* forms
(DMSOꢀd6)
Comꢀ
pound
R
NMe2
Ho
N—H...N
Table 3. Spectroscopic characteristics of solutions of salts
3b•HClO4 and 15 (δ , CD3CN)
H
1b
1c
OMe
NMe2
2.82 (3.18)
2.91 (3.30)
7.16 (7.53)
7.20 (7.85)
(19.38)
(19.81)
Comꢀ HClO4
pound (equiv.)
δ
JNH,NMe
/Hz
NMe2 CH2CH2 Harom N...H—N
1d
2.83 (3.25)
7.11 (7.79)
(19.82)
3b
3b
3b
3b
3b
15
1
2
4
10
20
—
3.22
3.27
3.27
3.28
3.28
3.29
3.29
3.36
3.38
3.41
3.41
3.59
6.87
7.12
7.16
7.24
7.28
7.86
17.69
17.01
17.17
17.46
17.65
18.65
2.72
2.71
2.69
2.66
2.62
2.58
1e
2.92 (3.29)
7.28 (7.84)
(19.88)
3b
3c
NH2
NMe2
2.80 (3.14)
2.88 (3.25)
6.45 (6.55)
7.04 (7.65)
(18.48)
(18.53)
* The spectroscopic data for the protonated form are given in
parentheses.

408
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 2, February, 2004
Ozeryanskii et al.
Table 4. Protonation of tetraamines 1c and 3c in CD3CN acꢀ
cording to H NMR spectroscopic data
Table 5. Constants рKа for selected "proton sponges"
(24 °C, DMSO)
1
Comꢀ
pound (equiv.)
HClO4
δ
JNH,NMe
/Hz
Comꢀ
pound
рКа
Comꢀ
pound
рКа
αꢀNMe2 βꢀNMe2 N...H—N
1a
1b
1c
1d
7.47 0.04 20
11.50 0.05 3,6
11.23 0.04b
10.97 0.04c
1e
3b
3c
14
11.31 0.04a
11.38 0.17
11.11 0.05a
11.27 0.04
1c
1c
1c
1c
3c
3c
1
2
3
4
1
3
3.30
3.40
3.43
3.43
3.28
3.39
2.74
2.85
3.22
3.23
2.74
3.15
20.08
16.97
17.26
17.33
18.80
15.53
2.61
—*
2.52
2.51
2.56
2.20
a The constant was determined at 70 °C due to poor solubility of
the compound in DMSO and extrapolated to ∼20 °C.
b Cf. lit. data3: 11.20.
* The constant was not determined because of overlapping of
the signal of the αꢀdimethylamino groups with the common
signal of the water molecule and the acidic protons (except for
the chelated proton in the N—H...N bridge); in this case, the
signal of the bridging proton does not have a multiplet structure
and appears as a broadened singlet.
c Cf. lit. data3: 10.90.
poorer solvation of the cation 3c•H+ in DMSO because
of the presence of the ethylene bridge. In the basicity,
"hybrid" 14 (рKa is 11.3 in DMSO) is intermediate beꢀ
tween compounds 1b and 1c (pKa are 11.5 and 11.2, reꢀ
spectively), being more similar to the latter. This fact is
probably attributable to the presence of an asymmetric
and, hence, weaker intramolecular hydrogen bond in the
cation 14•H+ (see above).
Analysis of the influence of the ortho substituents in
the orthoꢀdisubstituted "proton sponges" on the 1H NMR
spectroscopic parameters (cf. the chemical shifts of the
Ho protons and the dimethylamino groups in the neutral
and monoprotonated compounds, see Table 2) shows that
their electronꢀdonating effect changes in the following
series:*
and then slowly increases. The minimum chemical shift
δNH was observed in the presence of 2—3 equiv. of
monobasic acid (see Tables 3 and 4). Protonation of the
monocations D in DMSO, as opposed to that in acetoꢀ
nitrile, was virtually undetectable, because this basic solꢀ
vent successfully competes with these monocations for
subsequent protons.
It should be noted that all cationic species, which are
generated in the reactions of acids with symmetrical
polyamines 1a—e and 3b,c, are symmetrical in solutions
on the NMR time scale. Only triamine 14 forms the true
unsymmetrical monoꢀ and dications, the chelated NH
proton in its monocation being shifted by 60% toward the
βꢀdimethylamino group and only by 40% toward the
βꢀmethoxy group (the degree of asymmetry of intramoꢀ
lecular hydrogen bonds in such cations was determined
according to a procedure described in the literature19).
Structure—basicity relationship. Evidently, the overall
electronic effect of the ortho substituents in "proton
sponges" should depend substantially on the solvation efꢀ
fects. Apparently, that is the reason why the constants рKa
of compounds 1a—e and 3b,c change in a very complex
way (Table 5).
As expected, all orthoꢀaminoꢀsubstituted "proton
sponges" are much more basic than parent compound 1a,
although their рKa are no higher than the record value of
11.5 (in DMSO) for dimethoxy derivative 1b. The evident
reason for this fact is that the mesomeric interactions of
the βꢀdialkylamino groups, which are substantially twisted
relative to the ring, with the aromatic π system, are weaker
compared to those of the methoxy groups in compound
1b (see below). At the same time, the conjugation of the
oꢀNH2 groups in amine 3b should be stronger, which
corresponds to higher basicity of this compound comꢀ
pared to 3c. The latter compound is also somewhat less
basic than its naphthalene analog 1c due, apparently, to
NH2 > OMe >
>
> NMe2.
The changes in рKa are, on the whole, consistent with
this series, except for compound 1d, which is characterꢀ
ized by a somewhat lower basicity. This fact is to a certain
extent explained by the results of Xꢀray diffraction analyꢀ
sis, which are presented in Table 6 along with analogous
data for amines 1b, 1c, and 3c. Xꢀray diffraction analysis
of the latter compound was carried out in the present
study. The overall view of one of two crystallographically
independent molecules 3c is shown in Fig. 1.
As can be seen from Table 6, the pyrrolidine groups in
base 1d are twisted with respect to the naphthalene system
by only 36°. This fact should be favorable for their strong
steric interactions with the periꢀNMe2 groups. To reduce
repulsions, all amino groups in molecule 1d deviate from
the mean plane of the naphthalene ring in different direcꢀ
tions and the ring undergoes distortions. The torsion angle
between the C(4)—C(5) and C(10)—C(11) bonds inꢀ
* This series differs substantially from the analogous series for
the sterically unhindered methoxy and amino groups in benzene
derivatives21
> NMe2
>
> NH2 > OMe.

orthoꢀDisubstituted "proton sponges"
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 2, February, 2004
409
Table 6. Selected structural characteristics of molecules 1b,c,d and 3c
Comꢀ
pound
R
N...Na
/Å
Angle/deg
Sum of C—N—C anglesd
/deg
pe
(%)
T/K
Referꢀ
ence
NMe2—ringb
R—ringc
1b
1c
OMe
NMe2
2.756
2.770
74
55
6
64
346.2
356.2
90
97
190
298
23
3
1d
3c
2.848
2.824 f
61
63
36
68
357.6
352.4
98
95
298
120
3
g
NMe2
a The nonbonded distance between the periꢀnitrogen atoms.
b The average angles of rotation of the periꢀNMe2 groups with respect to the aromatic ring.
c The average angles between the substituents R and the aromatic ring.
d The average sums of the angles at the nitrogen atoms of the periꢀNMe2 groups.
e The p character of the lone electron pairs of the nitrogen atoms of the periꢀNMe2 groups was evaluated (%) from the
C—N—C bond angles as described in the study.22
f The average value for two crystallographically independent molecules in the unit cell.
g The present study.
creases to 19° as opposed to 3° in compounds 1b and 3c
and 14° in molecule 1c (see Fig. 1). Apparently, the
conformationally more rigid pyrrolidine groups in the
cation 1d•H+ are virtually perpendicular to the plane of
the aromatic system, as evidenced by the largest changes
in the chemical shifts of the dimethylamino groups
(∆δ(NMe2) 0.42) and the aromatic Ho protons
(∆δ(Ho) 0.68) for a pair of the species 1d—1d•H+ in the
series of the compounds under consideration (see Table
2). Taking into account that the chemical shift of the
chelated proton δH(NH) is determined by the effective
volume of the ortho substituent,24 the data presented in
Table 2 allow one to easily calculate the dimensionless
basicity index B, which we propose as the following exꢀ
pression
electronic interactions between the substituents, and the
steric effects and depends qualitatively on the conꢀ
stant рKa. For example, the indices B for compounds 1c,
1d and 3c are 19.0, 18.0, and 18.9, respectively.
The ethylene bridge in compound 3c is responsible for
a series of structural changes, which are unfavorable for
an increase in the constant рKa compared to that of "proꢀ
ton sponge" 1c. Among these changes are: 1) an increase
in the N...N distance from 2.77 to 2.82 Å resulting in the
formation of a more elongated and weak hydrogen bridge
in the cation 3c•H+ (see Tables 2 and 4); 2) an increase
in acoplanarity of the oꢀdimethylamino groups and the
naphthalene ring (68° compared to 64° for tetraamine 1c),
which reduces their electronꢀdonating effect; 3) an inꢀ
crease in the distance between the ortho substituents and
the periꢀNMe2 groups and, consequently, a decrease in
their mutual repulsion (the degree of pyramidality of the
bonds at the nitrogen atoms of the periꢀNMe2 groups
increases). The latter fact leads to a decrease in the sum of
the bond angles at the periꢀnitrogen atoms and a decrease
in the рꢀcharacter of their lone electron pairs, which is
virtually equivalent to a decrease in basicity (see Table 6).25
Nevertheless, all these factors are to a certain extent comꢀ
pensated by the +I effect of the CH2CH2 fragment.26
Reactivity. Earlier studies demonstrated that, in spite
of the virtually complete absence of Nꢀnucleophilicity,
"proton sponge" 1a possesses high Cꢀnucleophilicity and
readily reacts with numerous electrophiles.5,27 For exꢀ
ample, the reaction of compound 1a with dilute HNO3 in
AcOH immediately afforded the 2,4,5,7ꢀtetranitro deꢀ
rivative regardless of the substrate : HNO3 ratio. Until
recently, analogous data on orthoꢀdisubstituted "proton
sponges" were lacking. However, this problem is of conꢀ
siderable interest due to high basicity of these compounds
and the sharply different geometry of their periꢀdimethylꢀ
amino groups, which are substantially twisted (by 55—74°)
with respect to the naphthalene ring (see Table 6). These
B = δ (NH)/(∆δ(NMe2) + ∆δ(Ho)).
H
Since this index deals with the chemical shifts, it takes
into account the influence of the solvent (DMSO), the
C(18)
N(3)
C(15)
C(16)
C(17)
C(19)
N(4)
N(2)
C(6)
C(13)
C(14)
C(12)
N(1)
C(5)
C(4)
C(7)
C(11)
C(20)
C(8)
C(10)
C(9)
C(3)
C(2)
C(1)
Fig. 1. Overall view and the atomic numbering scheme for one
of crystallographically independent molecules of compound 3c.

410
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 2, February, 2004
Ozeryanskii et al.
facts should lead to a decrease in the activity of comꢀ
pounds of types 1b and 1c in electrophilic substitution
reactions, even despite the presence of additional activatꢀ
ing groups. The results of our study on the behavior of
compounds 1b and 1c in nitration and azoꢀcoupling reacꢀ
tions confirmed this assumption.
Unlike compound 1a, compound 1b is not niꢀ
trated by nitronium salts (NO2BF4—MeCN and
NO2BF4—Py—MeCN systems were examined) as well as
by HNO3 in AcOH. It should be noted that the latter
reaction performed on heating afforded naphthol 19 in
1
∼3% yield. Its structure was confirmed by H NMR
It was found that the reaction of 2,7ꢀdimethoxy deꢀ
rivative 1b with one equivalent of HNO3 (d = 1.41) in
concentrated H2SO4 (20 °C, 45 min) afforded only traces
of 3ꢀnitro derivative 16. The yield of the latter was inꢀ
creased to 81% in the presence of four equivalents of
HNO3. This is the first example of the meta substitution
with respect to the NMe2 groups in a series of naphthaꢀ
lene "proton sponges" devoid of substituents in the
peri positions (cf. lit. data28). This fact is quite underꢀ
standable. In an acidic medium, compound 1b occurs
completely in the cationic form due to its high basicity. In
this cation, the charged dimethylamino groups cannot
activate the ortho and para positions of the ring due to
which the direction of the attack of the electrophile is
determined by the methoxy groups.
spectroscopy (δOH 18.6) and mass spectrometry
(m/z 292 [M]+).
Compound 1c appeared to be completely inactive with
respect to nitrating agents. Under all the aboveꢀmenꢀ
tioned conditions, this compound remained intact. This
is consistent with the data on the geometry of base 1c as
well as with the fact that in acidic media this compound
forms the trication F in which all positions of the naphꢀ
thalene ring are strongly deactivated. The resistance of
tetraamine 1c to electrophiles (see also below) correꢀ
lates with the analogous behavior of 1,2ꢀbis(dimethylꢀ
amino)benzene, which, unlike the 1,3ꢀ and 1,4ꢀisomers,
does not undergo nitrosation and azo coupling with diꢀ
azonium salts.29
We examined the possibility of the reactions of comꢀ
pounds 1a—c with diazonium tetrafluoroborates30 in a
neutral medium (MeCN). It was demonstrated for the
first time that compound 1a readily reacts with diazonium
salts to form azo dyes (for example, 20) in 15—55% yields.*
By contrast, 2,7ꢀdisubstituted naphthalenes 1b,c, like their
tetrafluoroborates, are inert to the diazonium cations unꢀ
der study both at room temperature and on heating to
60—80 °C.
This fact can be used for synthetic purposes. It is
known5 that in some cases, acid HX eliminated in elecꢀ
trophilic substitution reactions of "proton sponge" 1a is
trapped by the starting substrate, thus removing oneꢀhalf
of the compound from the reaction. This trapping occurs
also in the azoꢀcoupling reaction of diamine 1a with diꢀ
azonium tetrafluoroborates due to which a twoꢀfold exꢀ
cess of the substrate is required. We demonstrated that in
the reaction of one equivalent of the diazonium salt with
an equimolar mixture of compounds 1a and 1b (or 1c),
"proton sponges" 1b,c only trap a proton, whereas
1,8ꢀbis(dimethylamino)naphthalene (1a) is completely
transformed into an azo dye. One of examples is illusꢀ
trated in Scheme 5.
Compound 20 is easily separated from the salt
1b•HBF4 with diethyl ether, and base 1b can be regenerꢀ
ated and used repeatedly.
Evidently, the introduction of ortho substituents into
molecule 1a substantially passivates the naphthalene sysꢀ
tem with respect to electrophiles, due to which many
reactions are either hindered or do not proceed at all.
Only 2,7ꢀdimethoxy derivative 1b was successively subꢀ
jected to nitration, which proceeded with an anomaꢀ
Interestingly, this reaction at 0 °C afforded dinitro
derivative 17 as virtually the only product, although in a
low yield (∼18%). Apparently, the transformation 16 → 17
proceeds through demethylated intermediate 18, in which
the methylamino group is efficiently conjugated with the
naphthalene ring due to the presence of an intramolecular
hydrogen bond. As a result, the second nitro group is
attached at position 5 (cf. lit. data14). The remarkable
1
feature of the H NMR spectrum of compound 17 is
strong deshielding of the H(4) proton (δH 9.51) due to the
presence of the adjacent orthoꢀ and periꢀnitro groups.
* The results of detailed investigation of this problem will be
published elsewhere.

orthoꢀDisubstituted "proton sponges"
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 2, February, 2004
411
Scheme 5
Table 7. Crystallographic data and details of Xꢀray diffraction
study of compound 3c
Parameter
Characteristic
Molecular formula
Molecular weight
C20H30N4
326.48
T/K
120(2)
λ/Å
0.71073
Diffractometer
Crystal dimensions/mm
Space group
a/Å
«Bruker SMART 1000 CCD»
0.35×0.40×0.60
Monoclinic, P2(1)/n
10.626(5)
b/Å
c/Å
26.575(13)
13.527(6)
β/deg
98.600(10)
3777(3)
V/Å3
lous orientation and was accompanied by oxidative deꢀ
methylation.
Z
8
dcalc/g cm–3
µ/mm–1
F(000)
1.148
0.069
1424
* * *
θ
max/deg
2.08—27.87
28191
8952 (0.1951)
To summarize, we developed convenient preparative
procedures for the synthesis of both new (1e, 3b,c, and 14)
and previously known (1b,c,d) orthoꢀdisubstituted "proꢀ
ton sponges." The characteristic features of their protonaꢀ
tion and the dependence of the basicity on the structural
factors were revealed. It was demonstrated that these comꢀ
pounds tend to act as strong bases rather than to be subꢀ
jected to the electrophilic attack. As a resut, orthoꢀdisubꢀ
stituted "proton sponges" are more convenient auxiliary
reagents in organic synthesis compared to parent comꢀ
pound 1a in reactions, which require the use of a strong
but lowꢀnucleophilic base.31—33
Number of measured reflections
Number of independent
reflections (Rint
)
R factors for all reflections
R1
wR2
0.2191
0.2076
0.821
GOOF
study. Since acenaphthene 3b containing free oꢀamino groups is
readily oxidized in solution, its рKa was estimated with a low
accuracy.
Orange crystals of tetraamine 3c suitable for Xꢀray diffracꢀ
tion analysis were grown by concentraing its saturated solution
in nꢀhexane under isothermal conditions at +5 °C. The crystalꢀ
lographic characteristics and main details of Xꢀray diffracꢀ
tion study are given in Table 7. The atomic coordinates, bond
lengths, bond angles, and torsion angles for the structure
of 3c were deposited with the Cambridge Structural Database
(CCDC 216764).
Experimental
1
The H NMR spectra were recorded on Bruker DPXꢀ250
(250 MHz) and Varian Unityꢀ300 (300 MHz) instruments with
SiMe4 as the internal standard. The UV spectra were measured
on a Varian Cary 100 spectrophotometer in 96% EtOH. The IR
spectra were recorded on a Specord IRꢀ75 spectrometer in Nujol
mulls. The mass spectra were obtained on a Perkin—Elmer
PEꢀ5MS RX instrument. Chromatography was carried out on
silica gel L (40—100 µm; Chemapol). The course of the reacꢀ
tions and the purities of the reaction products were monitored
by TLC on Al2O3 and Silufol plates; visualization was carried
out with iodine vapor. The melting points were measured
in sealed capillaries and are uncorrected. Commercial
5% Pd/C (Lancaster) and 1,8ꢀbis(dimethylamino)naphthalene
(1a, Aldrich) were used.
The basicities of amines 1d,e, 3b,c, and 14 were measured
by the competitive method using 1H NMR spectroscopy
in DMSOꢀd6; the concentration of each compound was
4.10•10–2 mol L–1; "proton sponges" 1b and 1c were used
as the reference compounds. The results of measurements
(the first ionization constants characterizing the neutral
Compounds 4 and 5 were synthesized according to proceꢀ
dures described earlier.34,35
4,7ꢀDiaminoꢀ5,6ꢀbis(dimethylamino)acenaphthene (3b).
A suspension of dinitroacenaphthene 3a (see Ref. 14) (0.1 g,
0.3 mmol) in MeOH (80 mL) was hydrogenated in the presence
of 5% Pd/C (0.025 g). After separation of the catalyst and reꢀ
moval of MeOH under a stream of argon, diamine 3b was preꢀ
pared in a yield of 0.081 g (∼100%) as paleꢀgray crystals, which
turned dark on storage in air, m.p. 172—174 °C (from 96%
EtOH). Found (%): C, 71.22; H, 8.03. C16H22N4. Calcuꢀ
lated (%): C, 71.08; H, 8.20. IR, ν/cm–1: 3450, 3360 (br., NH2).
1H NMR (CDCl3), δ: 2.92 (s, 12 H, NMe2); 3.14 (s, 4 H,
CH2CH2); 3.90 (br.s, 4 H, NH2); 6.54 (s, 2 H, Harom). Perchloꢀ
rate 3b•HClO4, colorless needleꢀlike crystals (from MeOH),
which turned dark on storage in sunlight or air; the compound
does not melt up to 300 °C, gradually turns black, and decomꢀ
poses. IR, ν/cm–1: 3492, 3395, 3240, 1630 (NH2); 1100 (ClO4–).
Perchlorate 15 was prepared from compound 3a accordꢀ
ing to a known procedure19 as paleꢀcreamꢀcolored crystals,
base
monocation equilibrium) are given in Table 5. The
constants рKa of compounds 1c and 1d were refined in the present

412
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 2, February, 2004
Ozeryanskii et al.
m.p. 214—215 °C (with decomp., from MeCN). Found (%):
C, 44.60; H, 4.32; Cl, 8.41. C16H19ClN4O8. Calculated (%):
C, 44.61; H, 4.45; Cl, 8.23.
2,7ꢀDi(pꢀtoluenesulfonamido)naphthalene (6) was synthesized
by catalytic hydrogenation of dinitronaphthalene 5 (cf. lit. data36)
followed by tosylation of 2,7ꢀdiaminonaphthalene.37 Comꢀ
pound 6 was prepared as greenish needleꢀlike crystals, m.p.
the reaction time being decreased from 3 days to 3 h. Red plateꢀ
letꢀlike crystals, m.p. 223—224 °C (from acetone). Found (%):
C, 53.55; H, 4.54. C13H13N3O5. Calculated (%): C, 53.61;
H, 4.50. H NMR (CDCl3), δ: 2.98 (s, 6 H, NMe2); 3.98 (s,
3 H, OMe); 7.16, 7.21, 7.72, and 7.82 (all d, 1 H each, H(6),
1
H(3), H(4), H(5)); J3,4 = 9.2 Hz, J5,6 = 9.0 Hz.
2,7ꢀDipiperidinoꢀ1,8ꢀdinitronaphthalene (12c) (see Table 1,
run 4). A solution of dinitronaphthalene 11 (0.278 g, 1 mmol)
and piperidine (2 mL, 20 mmol) in DMF (5 mL) was kept in the
dark for one week. Then the solution was poured into water
(50 mL). The precipitate was separated, washed with water,
dried in air, and purified by chromatography on silica gel
(CHCl3). The main orange zone was collected. The solvent was
removed. The oily residue was triturated with nꢀpentane to preꢀ
pare yellowꢀorange crystals in a yield of 0.123 g (32%), m.p.
183—184 °C (from acetone or MeOH). Found (%): C, 62.32;
H, 6.17. C20H24N4O4. Calculated (%): C, 62.49; H, 6.29.
1H NMR (DMSOꢀd6), δ: 1.56 (m, 12 H, H(3´), H(4´), H(5´));
3.01 (m, 8 H, H(2´), H(6´)); 7.66 and 8.18 (both d, 2 H each,
H(3), H(6), H(4), H(5)); J3,4 = 9.0 Hz.
1,8ꢀBis(dimethylamino)ꢀ2,7ꢀdimethoxynaphthalene (1b).
A mixture of dinitronaphthalene 11 (1.39 g, 5 mmol), MeOH
(60 mL), and Pd/C (0.4 g) was hydrogenated until the calcuꢀ
lated amount of hydrogen was absorbed. The catalyst was filꢀ
tered off and the methanol was removed on a rotary evaporator
under a stream of argon. Dimethyl sulfate (3.79 mL, 40 mmol),
Na2CO3•10H2O (11.44 g, 40 mmol), and water (30 mL) were
added to the residue of 1,8ꢀdiaminoꢀ2,7ꢀdimethoxynaphthalene.
The suspension was vigorously stirred under argon at 20 °C for
5 h and then extracted with benzene (25 mL). The extract,
which contained oxidation products and resins, was discarded.
Potassium hydroxide (10 g) was added with cooling and stirring
to the aqueous phase. After dissolution of KOH, the reaction
product was extracted with benzene (5×25 mL). The organic
phase was dried with anhydrous K2CO3 and then 60% aqueous
HBF4 (0.575 mL, 5 mmol)* was added. The reaction mixture
was vigorously stirred for 1 h to prepare a precipitate of
1,8ꢀbis(dimethylamino)ꢀ2,7ꢀdimethoxynaphthalene tetrafluoroꢀ
borate (1b•HBF4) (1.27 g, 70%), which was separated, washed
with Et2O, and crystallized from aqueous EtOH or water. Paleꢀ
gray needleꢀlike crystals were obtained, m.p. 228 °C (cf. lit.
data2: 227—230 °C). 1H NMR (CD3CN), δ: 3.19 (d, 12 H,
NMe2); 4.07 (s, 6 H, OMe); 7.41 and 7.96 (both d, 2 H each,
∼190 °C (from 50% EtOH; cf. lit. data37: 198 °C). IR, ν/cm–1
:
1
3260, 1650 (NH); 1600, 1525 (ring). H NMR (DMSOꢀd6), δ:
2.28 (s, 6 H, Me); 7.16 (dd, 2 H, H(3), H(6)); 7.31, 7.34, 7.65,
and 7.70 (all d, 4 H, 2 H, 2 H and 4 H, H(3´), H(1), H(8), H(4),
H(5), H(2´)); 10.51 (s, 2 H, NH); J1,3 = 1.9 Hz, J3,4 = 8.9 Hz,
J
2´,3´ = 8.2 Hz.
2,7ꢀDiaminoꢀ1,8ꢀdinitronaphthalene (7). A solution 70%
HNO3 (6.22 mL, 97 mmol) was added dropwise with vigorous
stirring to a solution of disulfonamide 6 (3.11 g, 6.7 mmol) in
AcOH (30 mL) at a temperature of no higher than 30 °C for
10 min. After 10—15 min, crystals began to precipitate. The
suspension was stirred for 12 h and then poured into water
(200 mL). The orangeꢀbrown precipitate that formed was washed
with water and dried in air at 120 °C to prepare a dinitro derivaꢀ
tive, which was dissolved in cold concentrated H2SO4 (45 mL)
and kept at ≈20 °C for 16 h. Then the resulting dark solution was
poured into ice water (450 g), which gave rise to a precipitate of
compound 7. The latter was separated, washed with water, and
dried in air at 120 °C. Small orangeꢀred crystals were prepared
in a yield of 1.46 g (88%), m.p. 282 °C (decomp., from acetone;
cf. lit. data18: t.decomp. 302 °C). IR, ν/cm–1: 3480, 3395, 3375,
1
1625 (NH2); 1530, 1350 (NO2). H NMR (DMSOꢀd6), δ: 6.94
(d, 2 H, H(3), H(6)); 7.40 (br.s, 4 H, NH2); 7.65 (d, 2 H, H(4),
H(5)); J3,4 = 8.9 Hz.
2,7ꢀBis(methylamino)ꢀ1,8ꢀdinitronaphthalene (8). A mixture
of diamine 7 (0.248 g, 1 mmol), K2CO3 (0.690 g, 5 mmol),
DMF (8 mL), and MeI (2.5 mL, 40 mmol) was refluxed for 30 h
and diluted with water (150 mL). The reaction products were
extracted with 1,2ꢀdichloroethane (DCE) (3×10 mL). After reꢀ
moval of the solvent and traces of DMF in vacuo, the residue
was dissolved in a minimum amount of DCE and purified by
chromatography on silica gel (DCE). The main darkꢀorange
fraction was collected. Methylamino derivative 8 was prepared
in a yield of 0.055 g (20%) as red prismatic crystals, m.p.
265—266 °C (decomp., from CHCl3 or DCE); a powder of 8 is
orange in color. Found (%): C, 52.29; H, 4.15. C12H12N4O4.
Calculated (%): C, 52.17; H, 4.38. IR, ν/cm–1: 3360 (NH);
H(3), H(6), H(4), H(5)); 19.61 (m, 1 H, NH); JNH,NMe
=
1
1540, 1350 (NO2). H NMR (CDCl3), δ: 3.07 (d, 6 H, Me);
2.6 Hz, J3,4 = 9.3 Hz. Free base 1b was prepared as follows. The
required amount of tetrafluoroborate (100—250 mg) was disꢀ
solved in a minimum volume of MeCN. The resulting solution
was shaken with 35% aqueous KOH (10 mL) and compound 1b
was extracted with nꢀhexane (5×10 mL). Compound 1b with
m.p. 68 °C was prepared in nearly quantitative yield. The propꢀ
erties of 1b are identical to those of the sample described in the
literature.2
6.83 and 7.60 (both d, 2 H each, H(3), H(6), H(4), H(5)); 7.99
(br.s, 2 H, NH); JNH,NMe = 5.1 Hz, J3,4 = 9.1 Hz.
2,7ꢀDimethoxyꢀ1,8ꢀdinitronaphthalene (11) was prepared acꢀ
cording to a procedure described in the literature.38 Redꢀbrown
crystals, t.decomp. 270 °C (from Py) (cf. lit. data38: 286 °C);
m.p. 235—245 °C reported in the study12 is, apparently, erroꢀ
1
neous. H NMR (DMSOꢀd6), δ: 4.05 (s, 6 H, OMe); 7.67 and
8.33 (both d, 2 H each, H(3), H(6), H(4), H(5)); J3,4 = 9.3 Hz.
2,7ꢀBis(dimethylamino)ꢀ1,8ꢀdinitronaphthalene (12a) was
synthesized according to a known procedure3 (see Table 1, run 2)
in 84% yield. The properties of compound 12a are identical to
those published in the literature.3 1H NMR (CDCl3), δ: 2.96 (s,
12 H, NMe2); 7.19 and 7.66 (both d, 2 H each, H(3), H(6),
H(4), H(5)); J3,4 = 9.0 Hz.
Compounds 1c,d,e, 3c, and 14 and their tetrafluoroborates
were synthesized analogously.
1,2,7,8ꢀTetrakis(dimethylamino)naphthalene (1c), paleꢀyelꢀ
low needleꢀlike crystals, m.p. 78—80 °C (from MeOH) (cf. lit.
data3: 78—80 °C); does not decompose up to 250 °C. The yield
* In the synthesis of "proton sponges" 1c,d,e, 3c, and 14, which
contain the βꢀamino groups and, hence, can form bis(tetraꢀ
fluoroborates) (see the text), this amount was doubled.
7ꢀDimethylaminoꢀ2ꢀmethoxyꢀ1,8ꢀdinitronaphthalene (13)
(see Table 1, run 1) was prepared analogously to compound 12a,

orthoꢀDisubstituted "proton sponges"
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 2, February, 2004
413
from compound 12a was 57%; the yield from compound 8
was 33%. Tetrafluoroborate 1c•HBF4, colorless plateletꢀlike
crystals, m.p. 255—257 °C (decomp., from water) (cf. lit. data3:
254—256 °C).
1,8ꢀBis(dimethylamino)ꢀ2,7ꢀdimethoxyꢀ3ꢀnitronaphthalene
(16). A solution of 70% HNO3 (0.126 mL, 2.0 mmol) in concenꢀ
trated H2SO4 (5 mL) cooled to 0 °C was added with stirring to a
solution of compound 1b (0.137 g, 0.5 mmol) in concentrated
H2SO4 (10 mL) cooled to 0 °C. The reaction solution immediꢀ
ately turned darkꢀred. Then cooling was stopped and the reacꢀ
tion mixture was kept at 20 °C for 45 min, after which the
solution was poured onto ice (200 g), neutralized with concenꢀ
trated NH3 until a steady ammonia odor appeared, and exꢀ
tracted with CHCl3 (5×5 mL). The extract was concentrated to
a minimum volume and the residue was purified by chromatogꢀ
raphy on a column with Al2O3 (CHCl3 as the eluent), the brown
fraction with Rf 0.46 being collected. Nitronaphthalene 16 was
obtained in a yield of 0.129 g (81%) as small brown crystals, m.p.
118—120 °C (from MeOH—H2O, 1 : 1). Found (%): C, 60.01;
H, 6.75. C16H21N3O4. Calculated (%): C, 60.17; H, 6.63. UV,
1,8ꢀBis(dimethylamino)ꢀ2,7ꢀdipyrrolidinonaphthalene (1d),
paleꢀcreamꢀcolored needleꢀlike crystals, m.p. 109—111 °C (from
Et2O). The yield from compound 12b was 48%. Found (%):
C, 75.02; H, 9.09. C22H32N4. Calculated (%): C, 74.96; H, 9.15.
1H NMR (CDCl3), δ: 1.92 (m, 8 H, H(3´), H(4´)); 2.90 (s,
12 H, NMe2); 3.04 (m, 8 H, H(2´), H(5´)); 7.12 and 7.38
(both d, 2 H each, H(3), H(6), H(4), H(5)); J3,4 = 8.5 Hz.
Tetrafluoroborate 1d•HBF4, colorless crystals, m.p. 204—206 °C
(decomp., from water). 1H NMR (CD3CN), δ: 2.07 and
3.12 (both m, 8 H each, H(3´), H(4´), H(2´), H(5´)); 3.27 (d,
12 H, NMe2); 7.72 and 8.02 (both d, 2 H each, H(3), H(6),
H(4), H(5)); 20.09 (br. m, 1 H, NH); JNH,NMe = 2.6 Hz,
J3,4 = 9.0 Hz.
λ
max/nm (logε): 240 (4.62), 303 (4.14), 415 sh (3.59), absorption
1,8ꢀBis(dimethylamino)ꢀ2,7ꢀdi(piperidino)naphthalene (1e),
paleꢀyellow rhombic crystals, without wellꢀdefined m.p.
(138—147 °C, from nꢀpentane). The yield from compound 12c
was 39%. Found (%): C, 75.67; H, 9.60. C24H36N4. Calcuꢀ
tail to 560 nm. 1H NMR (CDCl3), δ: 2.93 and 2.97 (both s, 6 H
each, 1ꢀ and 8ꢀNMe2); 3.83 and 3.95 (both s, 3 H each, 2ꢀ and
7ꢀOMe); 7.22 (d, 1 H, H(6)); 7.35 (d, 1 H, H(5)); 8.20 (s, 1 H,
H(4)); J5,6 = 8.8 Hz.
1
lated (%): C, 75.74; H, 9.54. H NMR (CDCl3), δ: 1.56 (m,
1ꢀDimethylaminoꢀ2,7ꢀdimethoxyꢀ8ꢀmethylaminoꢀ3,5ꢀdiꢀ
nitronaphthalene (17) was prepared and isolated as described
above but the starting darkꢀred solution was kept at 0 °C for
30 min. Compound 17 was obtained as darkꢀclaret needleꢀlike
crystals in a yield of 0.030 g (18%), m.p. 172—174 °C
(from MeOH), Rf 0.49 (Al2O3—CHCl3). Found (%): C, 51.58;
H, 5.15. C15H18N4O6. Calculated (%): C, 51.42; H, 5.18. UV,
4 H, H(4´)); 1.73 (m, 8 H, H(3´), H(5´)); 2.79 (m, 8 H, H(2´),
H(6´)); 2.96 (s, 12 H, NMe2); 7.23 and 7.41 (both d, 2 H each,
H(3), H(6), H(4), H(5)); J3,4 = 8.7 Hz. Tetrafluoroborate
1e•HBF4, colorless needleꢀlike crystals, m.p. 245—246 °C
1
(decomp., from water). H NMR (CD3CN), δ: 1.49, 1.80, and
2.91 (all m, 4 H, 8 H, 8 H, H(4´), H(3´), H(5´), H(2´), H(6´));
3.30 (d, 12 H, NMe2); 7.74 and 8.02 (both d, 2 H each, H(3),
H(6), H(4), H(5)); 20.11 (br.m, 1 H, NH); JNH,NMe = 2.5 Hz,
J3,4 = 8.9 Hz.
λ
max/nm (logε): 280 (4.74), 323 sh (4.51), 417 (4.46), 503 (4.79).
IR, ν/cm–1: 3120 (NH); 1600, 1560, 1525, 1500 (ring). 1H NMR
(CDCl3), δ: 2.91 (s, 6 H, 1ꢀNMe2); 3.30 (d, 3 H, 8ꢀNMe); 3.86
and 3.90 (both s, 3 H each, 2ꢀ and 7ꢀOMe); 8.21 and 9.51
(both s, 1 H each, H(6) and H(4)); 11.33 (br.s, 1 H, NH).
8ꢀDimethylaminoꢀ2,7ꢀdimethoxyꢀ4ꢀnitronaphthalenꢀ1ꢀol
(19). A 70% HNO3 solution (0.252 mL, 4.0 mmol) was added
with stirring to a solution of compound 1b (0.274 g, 1.0 mmol)
in AcOH (20 mL). The reaction mixture was stirred at 50 °C for
2 h, poured into H2O (100 mL), neutralized with 20% NaOH to
pH 7, and extracted with CHCl3 (5×5 mL). After removal of the
solvent, the residue was chromatographed on Al2O3 (CHCl3 as
the eluent), and the orange fraction with Rf 0.41 was collected.
Naphthol 19 was obtained in a yield of 0.005 g (2.5%) as orangeꢀ
brown crystals, m.p. 146—147 °C (from MeOH). Found (%):
C, 57.69; H, 5.25. C14H16N2O5. Calculated (%): C, 57.53;
4,5,6,7ꢀTetrakis(dimethylamino)acenaphthene (3c), yellowꢀ
brown plateletꢀlike crystals, m.p. 123—124 °C (from nꢀhexane).
The yield from compound 3a was 63%. Found (%): C, 73.65;
H, 9.33. C20H30N4. Calculated (%): C, 73.58; H, 9.26. 1H NMR
(CDCl3), δ: 2.66 (s, 12 H, 4,7ꢀNMe2); 2.93 (s, 12 H, 5,6ꢀNMe2);
3.22 (s, 4 H, CH2CH2); 7.02 (s, 2 H, Harom). Tetrafluoroborate
3c•HBF4, paleꢀcreamꢀcolored needleꢀlike crystals, m.p.
1
241—242.5 °C (decomp., from water). H NMR (CD3CN), δ:
2.74 (s, 12 H, 4,7ꢀNMe2); 3.28 (d, 12 H, 5,6ꢀNMe2); 3.42 (s,
4 H, CH2CH2); 7.58 (s, 2 H, Harom); 18.80 (br.s, 1 H, NH);
JNH,NMe = 2.6 Hz.
1,7,8ꢀTris(dimethylamino)ꢀ2ꢀmethoxynaphthalene (14), paleꢀ
yellow crystals, m.p. 47—48.5 °C (from nꢀpentane). The yield
from compound 13 was 61%. Found (%): C, 71.18; H, 8.65.
C17H25N3O. Calculated (%): C, 71.04; H, 8.77. 1H NMR
(CDCl3; the assignment was made by comparing with the specꢀ
tra of compounds 1b,c), δ: 2.68 (s, 6 H, 7ꢀNMe2); 2.90 (s, 6 H,
1ꢀNMe2); 2.94 (s, 6 H, 8ꢀNMe2); 3.87 (s, 3 H, OMe); 7.06,
7.13, 7.40, and 7.46 (all d, 1 H each, H(3), H(6), H(5), H(4));
J3,4 = 9.0 Hz, J5,6 = 8.7 Hz. Tetrafluoroborate 14•HBF4, colorꢀ
less needles, m.p. 158—159.5 °C (from water). 1H NMR
(CD3CN), δ: 2.74 (s, 6 H, 7ꢀNMe2); 3.17 (d, 6 H, 1ꢀNMe2);
3.33 (d, 6 H, 8ꢀNMe2); 4.09 (s, 3 H, OMe); 7.56, 7.62, 8.01, and
8.02 (all d, 1 H each, H(3), H(6), H(5), H(4)); 19.78 (br.s, 1 H,
NH); JNH,1ꢀNMe = 2.1 Hz, JNH,8ꢀNMe = 3.0 Hz, J3,4 = 9.2 Hz,
J5,6 = 8.9 Hz.
H, 5.52. UV, λmax/nm (logε): 241 (4.13), 436 (3.68). IR, ν/cm–1
:
2720, 1570, 1525, 1485, strong absorption in the region lower
than 650 cm–1 with the center at 500 cm–1. 1H NMR (CDCl3),
δ: 3.00 (d, 6 H, 8ꢀNMe2); 4.01 and 4.02 (both s, 3 H each,
2ꢀ and 7ꢀOMe); 7.33 (d, 1 H, H(6)); 8.24 (s, 1 H, H(3)); 8.94
(d, 1 H, H(5)); 18.58 (br.s, 1 H, OH); JOH,NMe = 1.2 Hz, J5,6
=
10.0 Hz. MS (EI, 70 eV), m/z (Irel (%)): 293 [M + 1]+ (11), 292
[M]+ (100), 277 [M – Me]+ (67), 262 [M – 2 Me]+ (31), 260
[M – Me – OH]+ (34), 231 (29), 188 (24), 144 (26), 115 (24),
102 (22).
4,5ꢀBis(dimethylamino)ꢀ1ꢀ(4ꢀmethoxyphenylazo)naphthalene
(20). A solution of pꢀmethoxyphenyldiazonium tetrafluoroꢀ
borate30 (0.022 g, 0.1 mmol) in anhydrous MeCN (0.6 mL) was
added in one portion to a solution of "proton sponge" 1a (0.021 g,
0.1 mmol) and compound 1b (0.027 g, 0.1 mmol) in anhydrous
MeCN (0.6 mL) at 0 °C. The solution immediately turned darkꢀ
red. The reaction mixture was kept at 0 °C for 1 h, the solvent
Compounds 1c and 3c and their analogs can be additionally
purified by vacuum sublimation (100 °C, 0.2 Torr)2 or elution
with Et2O through a small layer of deactivated Al2O3 (main
fractions).

414
Russ.Chem.Bull., Int.Ed., Vol. 53, No. 2, February, 2004
Ozeryanskii et al.
was removed, and the residue was treated with Et2O (2×2 mL).
After removal of Et2O and crystallization of the residue from
MeOH, azo dye 20 was prepared in a yield of 0.031 g (89%) as
blackꢀclaret crystals, m.p. 115—117 °C. Found (%): C, 72.14;
H, 7.08. C21H24N4O. Calculated (%): C, 72.39; H, 6.94. UV,
14. V. A. Ozeryanskii, A. F. Pozharskii, and N. V. Vistorobskii,
Izv. Akad. Nauk, Ser. Khim., 2000, 1215 [Russ. Chem. Bull.,
Int. Ed., 2000, 49, 1212 (Engl. Transl.)].
15. S. Hünig, Chem. Ber., 1952, 85, 1056.
16. V. I. Sorokin, V. A. Ozeryanskii, and A. F. Pozharskii,
Zh. Org. Khim., 2002, 38, 737 [Russ. J. Org. Chem., 2002, 38,
699 (Engl. Transl.)].
17. V. I. Sorokin, V. A. Ozeryanskii, and A. F. Pozharskii, Eur.
J. Org. Chem., 2003, 496.
λ
max/nm (logε): 283 (4.16), 482 (4.22), absorption tail up to
1
595 nm. H NMR (CDCl3), δ: 2.80 and 2.91 (both s, 6 H each,
4ꢀ and 5ꢀNMe2); 3.88 (s, 3 H, OMe); 7.00 (m, 4 H, H(3),
H(3´), H(5´), H(6)); 7.44 (br.t, 1 H, H(7)); 7.77 (d, 1 H, H(2));
7.95 (d, 2 H, H(2´), H(6´)); 8.58 (br.d, 1 H, H(8)); J2,3
=
18. F. Bell, J. Chem. Soc., 1962, 4254.
8.5 Hz, J2´,3´ = 8.9 Hz, J7,8 = 7.8 Hz. A gray crystalline precipiꢀ
tate was washed with diethyl ether to prepare tetrafluoroborate
of compound 1b (0.035 g, 97%), from which free amine 1b can
be isolated as described above.
19. A. F. Pozharskii and V. A. Ozeryanskii, Izv. Akad. Nauk,
Ser. Khim., 1998, 68 [Russ. Chem. Bull., 1998, 47, 66 (Engl.
Transl.)].
20. R. L. Benoit, D. Lefebvre, and M. Frechette, Can. J. Chem.,
1987, 65, 996.
21. F. Effenberger, P. Fischer, W. W. Schoeller, and W.ꢀD.
Stohrer, Tetrahedron, 1978, 34, 2409.
22. N. G. Korzhenevskaya, M. M. Mestechkin, and A. A.
Matveev, Zh. Obshch. Khim., 1992, 62, 626 [Russ. J. Gen.
Chem., 1992, 62 (Engl. Transl.)].
23. A. A. Woolf, Adv. Phys. Org. Chem., 1986, 22, 166 (CCDC
refcode JAHWEU).
24. A. F. Pozharskii, O. V. Ryabtsova, V. A. Ozeryanskii, A. V.
Degtyarev, O. N. Kazheva, G. G. Alexandrov, and O. A.
Dyachenko, J. Org. Chem, 2003, 68, 10109.
We thank Z. A. Starikova (A. N. Nesmeyanov Instiꢀ
tute of Organoelement Compounds of the Russian Acadꢀ
emy of Sciences, Moscow) for performing Xꢀray diffracꢀ
tion study of compound 3c.
This study was financially supported by the Russian
Foundation for Basic Research (Project Nos. 99ꢀ03ꢀ
33133a and 02ꢀ03ꢀ32080a).
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Received September 1, 2003