'Proton sponge' amides: Unusual chemistry and conversion into superbasic 6,7-bis(dimethylamino)perimidines

Article abstract of DOI:10.1016/j.tet.2012.12.040

Starting from 1-acylamino-4,5-bis(dimethylamino)naphthalenes, the first representatives of previously unknown 6,7-bis(dimethylamino)perimidines have been synthesized. In accordance with the electron-donor nature of the heterocyclic rings in these compounds they behave as proton sponges, displaying higher basicity (pK_a 8.4-9.3, DMSO) than those of the parent proton sponge (pK_a 7.5, DMSO; 18.6, MeCN) and perimidine (pK_a 13.6, MeCN). In accord with DFT calculations and proton transfer experiments, 1H-6,7-bis(dimethylamino)perimidines have been shown to exist as neutral rather than zwitterionic tautomers. A number of interesting observations concerning structure, synthesis, and reactivity of 1-acylamino-4,5-bis(dimethylamino)-8- nitronaphthalenes have been made.

Full text of DOI:10.1016/j.tet.2012.12.040

Tetrahedron 69 (2013) 1919e1929
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
‘Proton sponge’ amides: unusual chemistry and conversion into
superbasic 6,7-bis(dimethylamino)perimidines
*
Valery A. Ozeryanskii , Marina P. Vlasenko, Alexander F. Pozharskii
Department of Organic Chemistry, Southern Federal University, Zorge 7, 344090 Rostov-on-Don, Russian Federation
a r t i c l e i n f o
a b s t r a c t
Article history:
Starting from 1-acylamino-4,5-bis(dimethylamino)naphthalenes, the first representatives of previously
unknown 6,7-bis(dimethylamino)perimidines have been synthesized. In accordance with the electron-
donor nature of the heterocyclic rings in these compounds they behave as proton sponges, displaying
higher basicity (pKa 8.4e9.3, DMSO) than those of the parent proton sponge (pKa 7.5, DMSO; 18.6,
MeCN) and perimidine (pKa 13.6, MeCN). In accord with DFT calculations and proton transfer experi-
ments, 1H-6,7-bis(dimethylamino)perimidines have been shown to exist as neutral rather than zwit-
terionic tautomers. A number of interesting observations concerning structure, synthesis, and reactivity
of 1-acylamino-4,5-bis(dimethylamino)-8-nitronaphthalenes have been made.
Received 25 September 2012
Received in revised form 3 December 2012
Accepted 17 December 2012
Available online 29 December 2012
Keywords:
Amide
Hydrogen transfer
Perimidine
Proton sponge
Basicity
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
co-workers14 have prepared 6,7-bis(dimethylamino)-1,3-dimethyl-
2,3-dihydroperimidine (7), in which amino groups, being included
In the past decades there has been a long-standing interest in
organic superbases, especially ones that are neutral.1e3 Advances in
this area not only contribute to the development of acidebase
theory, but also result in the appearance of novel effective organic
reagents4 as well as other practically useful compounds.5e7 Prog-
ress in this field leads back to the discovery of proton sponges, the
parent of which is 1,8-bis(dimethylamino)naphthalene (1).8,9
Largely, proton sponge history represents ongoing attempts to
create stronger bases. A leading idea here consists in the de-
stabilization of a base that should be canceled after protonation, for
example, due to decreasing electronic and steric repulsions of basic
centers, namely peri-NMe2 groups. The greater gain in the free
energy on protonation, the larger the basicity of the corresponding
base (proton sponge). One of the simplest ways to cause this de-
stabilization is entering the strong electron-donor groups such as
NH2, NHMe, or NMe2 into the aromatic ring.10 Indeed, as it follows
from Scheme 1, 4-amino 2 and 4-methylamino 3 proton sponge
derivatives by 2e2.5 powers of 10 are more basic than the parent
compound.11 Unlike this, introducing one (compound 4),11 two
(5),12 or even four NMe2 groups (6)13 cause much less strength-
ening basicity due to strong acoplanarity between the naphthalene
ring and the amine substituents. To minimize this factor, Staab and
in a heterocycle, are more planar. As expected, compound 7 dis-
plays the greatest basicity in this series though not too large.
In this context, the main goal of the present article was to
synthesize the first representatives of previously unknown 6,7-
bis(dimethylamino)perimidines 8. It is known that the electron-
excessive character of perimidines, formally having seven
* Corresponding author. Tel./fax: þ7 863 2975146; e-mail address: vv_ozer2@
sfedu.ru (V.A. Ozeryanskii).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.12.040

1920
V.A. Ozeryanskii et al. / Tetrahedron 69 (2013) 1919e1929
7.23e8.06, dCO 156.3e164.6 ppm (CDCl3)]. Taking into account that
the chelated NH proton in protonated 1,8-bis(dimethylamino)
naphthalenes is observed in the 1H NMR spectra at dH 18e20 ppm,4
the above data are disagree with the intramolecular proton transfer
in 12 to form bipolar structures 15.
Scheme 1. Possible tautomeric equilibria in perimidine proton sponges.
p
-electrons in the heterocyclic ring, causes the extra-Huckel elec-
tron to be delocalized into the naphthalene system.14 As a result,
the latter gets a considerable negative -charge and exhibits a high
reactivity toward electrophiles and oxidants. At the same time, the
C(2) carbon atom gains a large positive -charge facilitating its
interaction with nucleophilic reagents. With this in mind, one could
expect that perimidine proton sponges might be essentially more
basic than compound 1. Besides, tautomerism of compounds 8
posed another intriguing problem since along with classical an-
nular prototropism (8%9), jumping of the NH proton to the peri-
NMe2 groups with the formation of zwitterionic form 10 might be
possible here (Scheme 1).
p
Treatment of naphthylamides 12bed with
a mixture of
HNO3eH2SO4 (1 equiv, ꢀ15 ꢁC) is accompanied by selective peri-
nitration to give nitroamides 13aec in 66e70% yields. Nitro-
derivative 16 was the only isomeric product, which we managed to
isolate in 4e6% yield during nitration of 12d.
p
To synthesize the target perimidines we employed the following
approach, using available 1-amino-4,5-bis(dimethylamino)naph-
thalene (11)5,11 as the starting compound and amides 12 and 13 as
the obvious intermediates (Scheme 2).
As it follows from IR and 1H NMR data, the peri-nitro group does
not significantly alter the spectral parameters of the
a-naph-
thylamide fragment, somewhat increasing frequencies of the nNH
and nCO vibration bands and deshielding the amide NH proton.
It seemed interesting to compare the nitration of carboxamides
12 with that of previously described sulfonamide 17.16 Complete
tarring occurred on treatment of 17 with the nitrating mixture at
ꢀ15 ꢁC or with HNO3/MeCN at 82 ꢁC.17 At the same time, in the
HNO3/AcOH system at 50 ꢁC, more controllable reaction led to the
formation of rather unexpected products, some of which like
nitroformamide 18 (20%), dibenzo[a,h]phenazine 19 (1%), and
naphthoquinone 20 (2%) were isolated; again, much of the starting
amide was decomposed in this case.
Scheme 2. Proposed synthetic approach to perimidine proton sponges.
2. Results and discussion
2.1. Synthesis and some properties of proton sponge amides
In addition to known carboxamide 12a,11 on treatment of amine
11 with the corresponding aroyl chloride or TFAA we have prepared
its analogs 12bed in 50e65% yields. Notably, that use of the aux-
iliary bases (K2CO3, Et3N, pyridine) in this reaction has little effect
on the yield owing to the deactivation of highly basic amine 1111 by
a liberated acid.
The NHCOR fragment in the synthesized amides has standard
Formation of 18 may be rationalized as the oxidation of amide 17
into N-formyl derivative 21 followed by mononitration.
properties [nNH 3233e3304, nCO 1645e1712 cmꢀ1 (Nujol), dNH

V.A. Ozeryanskii et al. / Tetrahedron 69 (2013) 1919e1929
1921
Table 1
Attempted deacylation of nitroamide 13b
Entry Reaction conditions
Result
1
2
3
4
Concd H2SO4/1 d/20 ꢁC
Concd H2SO4/5 min/0 ꢁC
Tarringa
Tarringa
Concd HCl/2 d/20 ꢁ
C
Starting compound
Starting compound
10% H2SO4/1 h/reflux
5
6
30% H2SO4/1 h/reflux
20% HCl/3 h/reflux
Starting compound and 25
Compound 25
7
8
9
4% HCl/1 h/reflux
Starting compound
Starting compound
Starting compound
Tarring
Starting compound
Starting compound
Starting compound
Starting compound
Starting compound
Starting compound
Like 18, dibenzophenazine 19 has the similar peri-arrangement
of the dimethylamino and N-methylformamido groups in the
molecule. Earlier we reported on a very rare example of dibenzo-
phenazine formation at oxidation of amine 11 (but not sulfonamide
17) with such a mild oxidant as tosyl chloride.16 Apparently, the
detosylation and oxidative dimerization of intermediate diamide
21 might lead to 19. From the other hand, one can suggest a com-
petitive process, when the hydrolytic cleavage of the formamide
group in 21 is followed by oxidation. This reaction pathway will
bring to ortho-naphthoquinone 20. Its structure, apart red-orange
color, is confirmed by 1H NMR spectrum, in which a low-field
broad singlet of the H-bonded proton (11.7 ppm), and a signal of
one of the N-methyl groups split into a doublet (3JNH,NMe¼5.0 Hz)
are observed. Additionally, there are quinone-specific [Mþ2]þ
along with the intense [MꢀCO]þ and [MꢀCOꢀOH]þ peaks in the
mass spectrum of 20.
Presumably, a failure in the preparation of the peri-nitro de-
rivative of amide 17 may be caused by the low oxidative potential of
the latter and lability of the N-tosyl fragment in the acidic media.
For comparison, benzamide 12b was also nitrated in the HNO3/
AcOH mixture. This time, although the overall regioselectivity had
decreased compared with the action of HNO3 in H2SO4, only ni-
tration products 13a (9%), 22 (9%), and 23 (12%) were isolated.
AcOH/2 d/20 ꢁC
NH2NH2eEtOH/24 h/60 ꢁC
HOCH2CH2NH2/5 min/reflux (170 ꢁC)
Et3N/1 h/reflux
10
11
12
13
14
15
16
17
Piperidine/2 d/20 ꢁC
PiperidineePhMe/27 h/reflux
10% KOH/1 h/reflux
MeONaeMeOH/1 d/20 ꢁC
LiOH/H2OeMeOHeTHF (1:1:1)/2 d/20 ꢁ
C
LiOH/H2OeMeOHeTHF (1:1:1)/1 h/reflux Starting compound
a
p-Nitrobenzoic acid is found.
As seen, a great majority of the acidic and basic reagents leave
nitroamide 13b untouched; a gradual tarring is observed under
more severe conditions. From this, it is hard to conclude whether
the applied conditions and reagents or the instability of nitroamine
24 are the reason of tarring. The presence of p-nitrobenzoic acid
among degradation products (Table 1, entries 1 and 2) indicates
that the deacylation still proceeds, but the amine formed un-
dergoes further transformations. Thus, under conditions of entries
5 and 6, it is possible to collect about 12% of an orange substance, to
which the structure of perimidin-6-one 25a, equilibrating with the
imino-form 25b was assigned (Scheme 4). Highly conjugated 25 is
soluble in acids and bases rendering some problems with its iso-
lation. In addition, the compound is crystallized from a wide range
of solvents, but forms only tiny needles or spheroidal aggregates of
those needles not suitable for X-ray measurements.
With a set of peri-nitroamides 13aec at hands, we were eager to
prepare still unknown amine 24, capable to form cation 24$Hþ
with highly asymmetrical intramolecular [NeH/N]þ bonding
(Scheme 3). Currently, much attention is focused on the properties of
such H-bonds, especially their geometry, energy of disruption at
assistance of solvent, counter-ion, temperature variations or selected
substituents, as well as on the ways to control their asymmetry.18e22
Scheme 4. Observed tautomeric equilibrium in quinoneimine 25.
It is noteworthy, that the result of the observed conversion does
not depend on the N-acyl substituent, as amides 13a and 13c on
heating in 20% HCl also produce compound 25 with 8e12% yield.
With this in mind one can suggest that nitroamine 24 is yet formed,
but exhibits strong instability undergoing a complex set of trans-
formations including redox reactions, hydrolytic deamination, and
heterocyclization; obviously, that the C(2) atom in 25 originates
from one of the NMe2 groups of amine 24. Some of the speculative
steps on this account are shown in Scheme 5.
Scheme 3. Possible mode of protonation of amine 24.
There is one example in the literature, namely compound 26, in
which the authors23 failed to remove the N-acyl groups by acid or
alkaline hydrolysis. Hence, an extremely low hydrolytic activity of
the naphthalene peri-nitroamides cannot be directly connected
with the presence of the proton sponge fragment. The observed
behavior of nitroamides 13aec and 26 may thus be interpreted in
terms of the steric shielding of a carbonyl group by the bulky nitro
functionality in the neighboring peri-position and the electrostatic
shielding exerted by NO2 with regard to external electrophiles and
Because the synthesis of compound 24 from amide 17 failed,
further efforts were focused on the hydrolysis of nitroamides
13aec. Unexpectedly, this seemingly simple transition was not
achieved. While starting amides 12bec heated at reflux with 10%
aqueous HCl are quantitatively deacylated within 1e5 h back to
amine 11, the adjacent peri-nitro group strongly inhibits the hy-
drolysis. Table 1 lists some of the tested conditions, applied to
amide 13b.

1922
V.A. Ozeryanskii et al. / Tetrahedron 69 (2013) 1919e1929
caused by the repulsive interaction of the two pairs of peri-func-
tionalities. The additional stimulus for the twisting is the tendency
of NMe2 groups to conjugate with the nitro group; the latter being
about 35ꢁ turned out of the mean ring plane, whereas the benza-
mide fragment is almost perpendicular to this plane and, hence, the
carbonyl group is not shielded. No H-bonded intramolecular in-
teractions were found between the NO2 and NH fragments, yet they
do exist intermolecularly (Supplementary data, Fig. S1). Hardly
these interactions as well as other geometrical features of 13a and
its analogs are the crucial reasons making hydrolysis so difficult.
Again, we may conclude that the steric shielding of amide carbonyl
is not the only factor lowering the rate of deacylation, as hydrolysis
of 1-acetylamino-8-phenylnapthalene, although requiring 10 h
for completion, still proceeds in ethanolic HCl.27 We believe that
the electrostatic shielding of the nearby situated nitro group
may impose some destabilization of the positive charge of pro-
tonated carbonyl (inhibition of acid catalysis), as well as the elec-
trostatic repulsion between the nitro group and the approaching
nucleophiles.
It is also known that the parent 1-amino-8-nitronaphthalene is
formed via acyl transfer between phthalimide 29 and hydrazine.28
To test this possibility we used peri-nitroimide 31, prepared in high
yield by the nitration of compound 30, in the reaction with a slight
excess of ethanolic hydrazine hydrate. Although the starting
compound was readily consumed even at room temperature,
a complex mixture of products hampered accurate assignment of
1H NMR signals. In addition, one could conclude that the extensive
loss of the NeMe and NMe2 groups took place during
hydrazinolysis.
Scheme 5. Proposed mechanism of transformation 24/25.
nucleophiles. Indeed, acenaphthene derivative 27 and formamide
28, in which the nitro and amido groups seem to be more distant
from each other than in 26, are readily hydrolyzed to the corre-
sponding amines in aqueous or methanolic HCl.24,25
As there is a lack of information on structure of peri-nitroamides
(no reports of such a kind were published to date), we determined
the molecular structure of amide 13a (Fig. 1).
Nevertheless, some of the products were identified (struc-
tures 32 and 33), including the desired nitroamine 24 (up to
67% yield). Next, we proved that both 24 and 31 on heating with
20% hydrochloric acid gave 25 in low yield, in agreement
with the proposed degradation of 24 in acidic media (see
Scheme 5).
The main structural feature of this compound is a severe
twisting of the naphthalene moiety [more than 26ꢁ if expressed as
a torsion angle between the C2eC3 and C7eC8 bonds; compare
with 11ꢁ for unsubstituted 1,8-bis(dimethylamino)naphthalene26
]
ꢁ
ꢀ
Fig. 1. Single-crystal X-ray structure of nitroamide 13a (100 K, P¼50%). Key lengths [A] and angles [ ]: N(4)eH 0.86, C(15)eO(3) 1.227, N(1)eC(1) 1.360, N(2)eC(9) 1.369, N(3)eC(4)
1.432, N(1)/N(2) 2.977, N(3)/N(4) 2.916, C(4)eC(5)eC(6) 124.9, C(1)eC(10)eC(9) 124.5, C(7)eC(6)eN(4)eC(15) 94.8, C(3)eC(4)eN(3)eO(2) 32.4, C(2)eC(3)eC(7)eC(8) 26.4.

V.A. Ozeryanskii et al. / Tetrahedron 69 (2013) 1919e1929
1923
ring, as was previously shown,31 are very prone to oxidation. With
this in mind, rather than to reduce amides 13a and 13c, we have
performed the catalytic hydrogenation of their protic salts, in which
the dimethylamino groups should be switched off from conjuga-
tion. Indeed, after evaporation of a solvent, tetrafluoroborates
34$HBF4 and 37$HBF4 were obtained as the only stable products of
spontaneous heterocyclization of the transient amines (Scheme 6).
The monoprotonation of 24 produces cation 24$Hþ (isolated as
tetrafluoroborate) with highly asymmetric [NeH$N]þ bonding. In
fact, using JNH,NMe coupling constants as the key indicators, we
3
estimated that the chelated proton is localized by 79% on the NMe2
fragment connected with the amino substituted benzene ring
(Scheme 3, in DMSO-d6; see also Fig. S2 in Supplementary data and
note that the NH2 group in 24 is not affected by protonation).29,30
2.2. Perimidine proton sponges
To synthesize perimidine proton sponges 8, we subjected
nitroamides 13a and 13c to the action of reducing agents. The in-
teraction of 13a with zinc dust in AcOH was accompanied by a color
change from red to yellow, which is typical for all simple peri-
midines.15 However, neutralization of the reaction mass with
KOH followed by chromatography gave, instead of expected
2-phenylperimidine 34, a mixture of epoxide 35 (18%) and peri-
midinone 36 (4%) as the products of oxidative transformations.
Scheme 6. Reductive heterocyclization of protonated peri-nitroamides.
Alternatively, the oxidation of aminoperimidines may be
inhibited via N(1)-substitution. Thus, the reduction of tertiary
nitroamides 38 and 39 prepared by N-methylation32 of the corre-
sponding secondary amides gave yellow and air-stable 1-
methylperimidines 40 and 41 in high yield (Scheme 7). Only one
Compound 36, being a 2-phenyl derivative of quinoneimine 25,
has similar spectral properties and, like 25, undergoes fast tauto-
merization in solutions under ambient conditions. The structure of
epoxide 35 was confirmed by NMR and mass spectroscopic
methods and finally proved by a single-crystal X-ray diffraction
experiment (Fig. 2).
Scheme 7. Preparation of stable perimidine derivatives.
of them, namely 41, could be quaternized with methyl iodide at
room temperature providing salt 42 almost quantitatively. This is
not realized for 40 possibly due to the steric strain arising from
close proximity of the three CH3 groups in the corresponding salt
(cf. however, Ref. 33).
The sensitivity of perimidine 34 to air is not surprising in view of
the
p-excessive character of perimidines in conjunction with the
presence of the strong þM-substituents (NMe2 groups).15 Even
simple perimidines bearing one amino group in the naphthalene
ꢁ
ꢀ
Fig. 2. Single-crystal X-ray structure of epoxide 35 (100 K, P¼50%, one of four independent molecules is presented). Key lengths [A] and angles [ ]: N(43)eC(44) 1.360, N(42)eC(46)
1.319, C(43)eC(42) 1.356, C(47)eC(48) 1.474, C(41)eN(41) 1.351, C(49)eO(42) 1.226, N(43)eC(413)eN(42) 125.4, C(411)eN(41)eC(412) 115.7, C(419)eC(414)eC(413)eN(43) 14.9,
C(42)eC(41)eN(41)eC(411) 18.4, C(41)eC(410)eC(49)eO(42) 22.8.

1924
V.A. Ozeryanskii et al. / Tetrahedron 69 (2013) 1919e1929
An interesting result was obtained on recrystallization of 42
one from the heterocyclic ring and the other from the NMe2 groups,
to give perimidine 34 (see Fig. S4 in Supplementary data); no traces
of zwitterion 10 (R¼Ph) were found. We may also conclude that the
NH-acidity of compound 34 is not enough to generate anion 46
under these conditions.
from a CH2Cl2eCCl4 mixture to get crystals suitable for X-ray
measurements. Unexpectedly, salt 43 with two iodide ions had
been isolated. Its structure, apart from perimidinium fragment,
contained 2,3-dihydroperimidinium moiety evidently arising in the
result of oxidation of the peri-dimethylamino groups during crystal
growing (Fig. 3). Such kind of transformations in proton sponges
under action of various oxidants is well known.34e36 Apparently, in
1/2
our case carbon tetrachloride (E ¼ꢀ0.25 V, MeCN, SCE)37 for the
red
first time served as an oxidant. This had been proved in a separate
1/2
experiment, when proton sponge 1 (E ¼þ0.36 V, MeCN, SCE)38
ox
was refluxed in CCl4 for prolonged time (26 h). The formation of
1,1,3-trimethyl-2,3-dihydroperimidinium chloride, although in
a small yield (1.5%), was detected. In principle, the conversion
42/43 could also proceed as an intramolecular hydride transfer
from the NMe2 groups onto the perimidinium ring.39 However,
such a possibility had been rejected since 1 remained unchanged
on heating with 1,3-dimethylperimidinium methylsulfate in EtOH
(see Ref. 40 for reductive potentials of such cations).
Second, when 34$HBF4 was mixed with 1 equiv of proton
sponge 1, an equilibrium depicted in Scheme 8 was established by
1H NMR in DMSO-d6. Based on the content of 34 in this mixture
(11%, see Fig. S5 in Supplementary data), we estimated pKa of
ꢁ
ꢀ
Fig. 3. Single-crystal X-ray structure of dication of salt 43 (100 K, P¼50%). Key lengths [A] and angles [ ]: N(1)eC(1) 1.429, N(2)eC(9) 1.467, N(3)eC(6) 1.413, N(4)eC(4) 1.429,
C(15)eN(4) 1.327, C(15)eN(3) 1.342, N(3)eC(15)eN(4) 121.9, N(1)eC(12)eN(2) 110.9, N(3)eC(15)eC(18)eC(19) 69.6, N(4)eC(15)eC(18)eC(23) 79.0, C(10)eC(1)eN(1)eC(12) 30.6.
An intriguing question to answer is which of the two NH protons
in salts 34$HBF4 and 37$HBF4 would undergo an acidic ionization
first? It could not be excluded that the electron withdrawing sub-
Scheme 8. Deprotonation of 34$HBF4 by 1,8-bis(dimethylamino)naphthalene.
stituents in position 2 of the perimidine system (Ph and CF3 groups)
might stabilize zwitterionic forms 10. However, DFT calculations
undertaken to establish relative stability of the species depicted in
Scheme 2 (cases for R¼H, Me, Ph, and CF3 were considered, see
Table S1 in Supplementary data) have shown that neutral forms
8(9) are by 11.9e15.5 kcal/mol more stable in the gas phase over
zwitterions 10, although solvation (DMSO) and electron-accepting
groups in position 2 strongly minimize this difference (up to
0.4 kcal/mol).
First, we have demonstrated that the cation of salt 34$HBF4 is
protonated at the N(3) nitrogen to form symmetrical dication 44
(Supplementary data, Fig. S3). Upon treatment with excess of
superbasic diamine 45 (pKa¼11.5 in DMSO),41 44 loses two protons,
perimidine proton sponge 34 as 9.3. It should be noted that 34 upon
formation gradually decomposes into insoluble crimson deposits
even in a closed ampoule.42
Finally, we had measured basicity of compounds 40 and 41,
allowing them to equilibrate with 1 taken as tetrafluoroborate or
perchlorate salts. Integration of the corresponding signals in the 1H
NMR spectra (DMSO-d6) gave pKa 8.8 for 40 and 8.4 for 41. Thus,
6,7-bis(dimethylamino)perimidines are notably stronger bases
than the parent proton sponge. In fact, they are 105e106 times more
basic than simple perimidines with no substituents in the

V.A. Ozeryanskii et al. / Tetrahedron 69 (2013) 1919e1929
1925
naphthalene ring.43 It should be also stressed that, while peri-
4.4. 1-Benzoylamido-4,5-bis(dimethylamino)naphthalene (12b)
midine 41 is quaternized at the heterocyclic ring (see Scheme 7)
both 40 and 41 are protonated at the dimethylamino groups (see
Fig. S6 in Supplementary data). This is a typical behavior of proton
sponges [cf. recent data on 4,5-bis(dimethylamino)quinolines].44
The crude product obtained after solvent evaporation was pu-
rified by column chromatography (Al2O3, ethyl acetate, Rf¼0.87) to
afford 12b (50%) as a colorless solid; mp 202e203 ꢁC (EtOAc). 1H
NMR (CDCl3):
d
¼2.79 (s, 6H, 5-NMe2), 2.80 (s, 6H, 4-NMe2),
6.89e7.02 (m, 2H, 3-H, 6-H), 7.33 (dd, J¼7.4, J¼8.1, 1H, 7-H), 7.41 (d,
3. Conclusions
J¼8.1,1H, 8-H), 7.43e7.62 (m, 3H, 30-H, 40-H, 50-H), 7.69 (d, J¼7.4,1H,
2-H), 7.87e8.01 (m, 3H, 20-H, 60-H, NH). 13C NMR (CDCl3):
d
¼43.63
In summary, the first representatives of perimidine proton
sponges [6,7-bis(dimethylamino)perimidines] have been synthe-
sized. It has been shown that the compounds with the free NH group
in the heterocyclic moiety exist exclusively as neutral rather than
zwitterionic species, what was confirmed by DFT calculations and
NMR protonation experiments. Perimidine proton sponges differ by
three remarkable peculiarities: (1) unlike ordinary perimidines they
are protonated at the peri-NMe2 groups (proton sponge behavior)
but alkylated at the heterocyclic ring, producing 1,3-dialkylperimi-
dinium salts (azole-like behavior), (2) their basicity is nearly by
two powers of 10 higher than that of the parent proton sponge and
much higher than that of perimidines, which allows to classify 6,7-
bis(dimethylamino)perimidines as superbases,2 (3) unusually easy
oxidative cyclization of 6,7-bis(dimethylamino)-1,3-dimethyl-2-
phenyl-1H-perimidinum iodide into tetraazapyrenium diiodide
has been disclosed.
In the synthesis of perimidine proton sponges, unexpectedly
high hydrolytic resistance of their precursors, naphthalene peri-
nitroamides, has been discovered and studied. Regardless of the
acyl structure, under prolonged heating in acidic conditions the
indicated amides, instead of the expected peri-nitroamines, gave
highly conjugated 7-methylamino-6H-perimidin-6-one as the only
isolable product.
and 43.65 (NMe2), 111.2, 112.0, 113.5, 119.8, 122.4, 125.0, 125.6, 126.7,
128.2, 131.0, 132.2, 134.6, 149.0, 150.7, 165.8 (C]O). IR (
n
/cmꢀ1):
3304 (NH), 1645 (C]O), 1558, 1522 (Ar). C21H23N3O (333.44): calcd.
C 75.65, H 6.95, N 12.60; found C 75.72, H 6.90, N 12.67.
4.5. 4,5-Bis(dimethylamino)-1-(p-nitrobenzoylamido)naph-
thalene (12c)
The crude product was purified by crystallization from CHCl3 to
afford 12c (50%) as light orange crystals; mp 220e222 ꢁC (EtOAc).
1H NMR (CDCl3):
d
¼2.79 (s, 12H, 4,5-NMe2), 6.87e6.97 (m, 2H, 3-H,
6-H), 7.26e7.37 (m, 2H, 7-H, 8-H), 7.60 (d, J¼8.1, 1H, 2-H), 8.00e8.13
(m, 3H, 20-H, 60-H, NH), 8.60 (d, J¼8.8, 2H, 30-H, 50-H). 13C NMR
(CDCl3):
d
¼44.2 (both NMe2), 111.6, 112.8, 113.7, 120.3, 123.3, 124.0,
124.6, 126.6, 128.5, 132.7, 140.6, 149.7, 150.3, 151.5, 164.6 (C]O). IR
(n
/cmꢀ1): 3275 (NH),1648 (C]O),1602,1558 (Ar),1526,1343 (NO2).
C21H22N4O3 (378.43): calcd. C 66.65, H 5.86, N 14.81; found C 66.63,
H 5.82, N 14.74. MS, m/z (I (%)): 378 [M]þ (36), 363 (12), 334 (16),
212 (12), 197 (55), 183 (29), 168 (25), 150 (12), 115 (15), 104 (19), 76
(18), 58 (100).
4.6. 4,5-Bis(dimethylamino)-1-trifluoroacetamidonaphthalene
(12d)
4. Experimental section
A solution of trifluoroacetic anhydride (0.17 mL, 0.12 mmol) in
dry toluene (15 mL) was added dropwise to a solution of amine 11
(221 mg, 0.10 mmol) in dry toluene (15 mL) at 0 ꢁC for 30 min. The
mixture was stirred for another 30 min at room temperature, after
that 25% aqueous ammonia (20 mL) was added. The organic layer
was separated and the aqueous layer was extracted by toluene. The
combined toluene extract was washed with water and evaporated.
The crude product thus obtained was purified by column chro-
matography (Al2O3, ethyl acetate/n-hexane, 1:2, Rf¼0.62). Sub-
sequent crystallization from n-hexane at ꢀ20 ꢁC afforded 12d (65%)
as sand-colored crystals, quickly liquefying on contact with vapors
4.1. Spectroscopic measurements
1H and 13C NMR spectra were recorded on a Bruker DPX-250
(250 MHz) spectrometer with the solvent residual peaks as the
internal standard (d
/ppm, nJ/Hz). IR spectra were measured in Nujol
on an FT FSM-1202 spectrometer. Mass spectra were obtained from
Finnigan MAT INCOS 50 instrument (electron impact, 70 eV). Thin
layer chromatography was carried out on Al2O3 and on silica gel
(70e230 mesh, Aldrich). The progress of reactions and the purity of
products were monitored by TLC on Al2O3 and Silufol plates; de-
velopment with iodine vapor. The melting points were measured in
sealed capillaries and are uncorrected. The solvents were purified
and dried by standard methods.
of solvents; mp 47e49 ꢁC. 1H NMR (CDCl3):
d¼2.79 (s, 12H, 4,5-
NMe2), 6.88 (d, J¼8.2, 1H, 3-H), 6.94 (dd, J¼7.6, J¼1.0, 1H, 6-H),
7.21 (dd, J¼8.5, J¼1.0, 1H, 8-H), 7.37 (dd, J¼8.5, J¼7.6, 1H, 7-H), 7.57
(d, J¼8.2, 1H, 2-H), 7.97 (br s, 1H, NH). 13C NMR (CDCl3):
¼44.4 and
d
44.5 (NMe2), 111.5, 113.2, 113.3, 116.7 (q, JC,F¼287.1, CF3), 120.3,
4.2. Preparation of starting materials
122.3, 123.2,127.3, 132.3, 151.1,151.8,156.3 (q, JC,F¼36.4, C]O). IR (
n/
cmꢀ1): 3265 (NH), 1712 (C]O), 1578, 1538 (Ar), 1186e1128 (CeF).
C16H18F3N3O (325.34): calcd. C 59.07, H 5.58, N 12.91; found C 59.11,
H 5.62, N 12.94. MS, m/z (I(%)): 325 [M]þ (80), 310 (31), 294 (51),
279 (59), 266 (13), 225 (14), 209 (17), 197 (91), 183 (45), 168 (83),
154 (18), 140 (21), 127 (12), 115 (37), 105 (11), 99 (18), 69 (40), 58
(100), 44 (36), 30 (18).
Compounds115,11 and3832 wereprepared asdescribed previously.
For transprotonation measurements, 1,8-bis(dimethylamino)naph-
thalene (1) (Alfa Aesar) was used as received.
4.3. Benzoylation of 1-amino-4,5-bis(dimethylamino)naph-
thalene (11)
4.7. Nitration of amides with nitrating mixture
This was performed with benzoyl chloride or p-nitrobenzoyl
chloride according to the published method.45 Pyridine (3 equiv)
and acyl chloride (1.1 equiv) were added to a cooled to 0 ꢁC solution
of amine 11 in anhydrous chloroform. The mixture was stirred for
4 h at 0 ꢁC until the starting amine disappeared and neutralized
with KOH (1.5 equiv). The organic layer was separated, washed with
the equal amount of water, dried with anhydrous Na2SO4, and
concentrated to the minimum volume.
A solution of 56% aqueous HNO3 (0.009 mL, 0.10 mmol) in concd
H2SO4 (1 mL) was added dropwise to a cooled to ꢀ20 ꢁC solution of
the corresponding amide (0.10 mmol) in concd H2SO4 (2 mL). The
mixture was stirred for 5 min at ꢀ20 ꢁC, poured on crashed ice
(20 g), neutralized with aqueous ammonia, and extracted with
chloroform (3ꢂ10 mL). The solvent was removed and the crude
product was purified by column chromatography (Al2O3, CHCl3).

1926
V.A. Ozeryanskii et al. / Tetrahedron 69 (2013) 1919e1929
4.8. 1-Benzoylamido-4,5-bis(dimethylamino)-8-nitronaphth-
alene (13a)
4.13. N-(8-Dimethylamino-4-(4-methylphenylsulfonamido)-
3-nitronaphthalen-1-yl)-N-methylformamide (18)
Yield 67%; Rf¼0.83, dark red solid with mp 218e219 ꢁC (EtOAc).
Rf¼0.21, yield 20%, yellow-orange solid with mp 185e186 ꢁC
1H NMR (CDCl3):
d
¼2.80 (s, 6H, 4-NMe2), 3.00 (s, 6H, 5-NMe2), 6.64
(EtOAc). 1H NMR (CDCl3):
d
¼2.41 (s, 3H, CMe), 2.61 (s, 3H, 5-NMe2),
(d, J¼9.0, 1H, 6-H), 7.05 (d, J¼8.5, 1H, 3-H), 7.41e7.54 (m, 3H, 30-H,
2.76 (s, 3H, 5-NMe2), 3.41 (s, 3H, NMe), 7.19 (d, J¼8.2, 2H, 30-H, 50-
H), 7.33e7.44 (m, 3H, 6-H, 20-H, 60-H), 7.51 (s,1H, 3-H), 7.64 (t, J¼7.9,
J¼8.5, 1H, 7-H), 8.14 (s, 1H, CHO), 8.42 (br s, 1H, NH), 8.52 (dd, J¼8.5,
40-H, 50-H), 7.72 (d, J¼8.5, 1H, 2-H), 7.87e7.96 (m, 2H, 20-H, 60-H);
8.00 (d, J¼9.0, 1H, 7-H), 8.48 (s, 1H, NH). 13C NMR (CDCl3):
¼43.44
d
and 43.48 (NMe2), 107.0, 113.0, 116.8, 122.7, 127.0, 127.6, 129.1, 129.9,
J¼1.0, 1H, 8-H). 13C NMR (CDCl3):
¼21.8 (CMe), 34.4 (NMe), 44.3
d
130.5, 132.1, 135.1, 137.1, 150.7, 157.3, 166.5 (C]O). IR (
n
/cmꢀ1): 3400
and 45.7 (NMe2), 118.7, 120.1, 123.8, 125.4, 126.7, 127.4, 129.6, 134.2,
(NH), 1670 (C]O), 1576, 1558, 1506 (Ar), 1530, 1345 (NO2).
C21H22N4O3 (378.43): calcd. C 66.65, H 5.86, N 14.81; found C 66.69,
H 5.80, N 14.84.
136.0, 136.3, 139.8, 140.9, 142.2, 149.7, 163.6 (C]O). IR (n
/cmꢀ1):
3085 (NH), 1657 (C]O), 1580 (Ar), 1537, 1353 (NO2), 1336, 1166
(SO2). C21H22N4O5S (442.50): calcd. C 57.00, H 5.01, N 12.66; found C
57.05, H 5.03, N 12.62. MS, m/z (I (%)): 442 [M]þ (13), 287 [MꢀTs]þ
(14), 260 (18), 259 [MꢀTsꢀCO]þ (100), 213 [MꢀTsꢀNO2]þ (6), 91
(21), 44 (11).
4.9. 4,5-Bis(dimethylamino)-8-nitro-1-(p-nitrobenzoylamido)
naphthalene (13b)
Yield 70%; Rf¼0.81, dark red solid with mp 220e221 ꢁC (EtOAc).
4.14. N,N0-(4,11-Bis(dimethylamino)dibenzo[a,h]phenazine-
5,12-diyl)bis(N-methylformamide) (19)
1H NMR (CDCl3):
d
¼2.82 (s, 6H, 4-NMe2), 3.02 (s, 6H, 5-NMe2), 6.65
(d, J¼9.1, 1H, 6-H), 7.05 (d, J¼8.5, 1H, 3-H), 7.73 (d, J¼8.5, 1H, 2-H),
8.01e8.11 (m, 3H, 20-H, 60-H, 7-H), 8.31 (d, J¼8.8, 2H, 30-H, 50-H),
Rf¼0.83, yield 1%, orange solid (fluorescent in solutions under
8.73 (br s, 1H, NH). 13C NMR (CDCl3):
d
¼43.36 and 43.44 (NMe2),
UV-light), mp 235e236 ꢁC (EtOAc). 1H NMR (CDCl3):
d
¼2.75 and
107.1, 112.8,121.8,124.3,126.9, 128.8, 129.1, 130.4, 130.5, 136.6, 140.7,
2.81 (both s, 12H, NMe2), 3.54 (s, 6H, NMe), 7.51 (d, J¼8.5, 2H, 3-H,
10-H), 7.76 (s, 2H, 6-H, 13-H), 7.82 (dd, J¼8.5, J¼7.2, 2H, 2-H, 9-H),
8.45 (s, 2H, CHO), 9.42 (d, J¼7.2, 2H, 1-H, 8-H). C28H28N6O2
(480.58): calcd. C 73.00, H 5.87, N 17.49; found C 73.03, H 5.82, N,
17.54. MS, m/z (I (%)): 480 [M]þ (20), 424 [Mꢀ2CO]þ (56), 259 (27),
241 (68), 221 (22), 195 (29), 194 (37), 188 (26), 181 (36), 98 (23),
97 (23), 91 (58), 83 (32), 69 (47), 57 (65), 55 (86), 44 (100), 42 (67),
41 (56).
150.0, 151.2, 157.6, 164.4 (C]O). IR (
n
/cmꢀ1): 3269 (NH), 1657 (C]
O), 1600, 1566 (Ar), 1524, 1344 (NO2). C21H21N5O5 (423.43): calcd. C
59.57, H 5.00, N 16.54; found C 59.51, H 5.07, N,16.51. MS, m/z (I (%)):
423 [M]þ (8), 377 [MꢀNO2]þ (76), 332 (4), 273 (4), 211 (7), 197 (7),
183 (11), 150 (11), 104 (17), 76 (15), 58 (100), 44 (9), 42 (7).
4.10. 4,5-Bis(dimethylamino)-8-nitro-1-trifluoracetamidonaph-
thalene (13c)
4.15. 5-Dimethylamino-4-methylaminonaphthalene-1,2-dione
(20)
Yield 66%; Rf¼0.79, dark red solid with mp 144e145 ꢁC (n-oc-
tane). 1H NMR (CDCl3):
d
¼2.82 (s, 6H, 4-NMe2), 3.01 (s, 6H, 4-
NMe2), 6.66 (d, J¼9.2, 1H, 6-H), 6.99 (d, J¼8.7, 1H, 3-H), 7.61 (d,
Rf¼0.10, yield 2%, red-orange solid with mp 223e225 ꢁC (EtOAc).
J¼8.7, 1H, 2-H), 8.09 (d, J¼9.2, 1H, 7-H), 8.87 (s, 1H, NH). 13C NMR
1H NMR (CDCl3):
d
¼2.75 (s, 6H, 5-NMe2), 3.07 (d, J¼5.0, 3H, 4-
(CDCl3):
d
¼43.2 and 43.4 (NMe2), 107.1, 112.3, 116.0, 116.6 (q,
NMe), 5.79 (s, 1H, 3-H), 7.48e7.57 (m, 1H, 7-H), 7.61 (dd, J¼8.2,
JC,F¼286.8, CF3), 119.3, 126.5, 129.9, 131.0, 136.0, 151.7, 156.6 (q,
J¼1.6, 1H, 6-H), 8.06 (dd, J¼7.2, J¼1.6, 1H, 8-H), 11.71 (br s, 1H, NH).
JC,F¼36.5, C]O), 157.7. IR (
n
/cmꢀ1): 3354 (NH), 1716 (C]O), 1581,
13C NMR (CDCl3):
d
¼30.2 (NMe), 45.5 (NMe2), 98.6, 123.6, 126.7,
1558 (Ar), 1538, 1344 (NO2), 1182e1128 (CeF). C16H17F3N4O3
(370.33): calcd. C 51.89, H 4.63, N 15.13; found C 51.82, H 4.69, N
15.16. MS, m/z (I (%)): 370 [M]þ (61), 325 (32), 294 (13), 279 (19),
255 (11), 240 (17), 224 (38), 209 (35), 197 (17), 181 (23), 168 (19),
140 (21), 115 (11), 69 (21), 58 (100), 44 (23), 30 (12).
128.1, 131.6, 133.6, 151.8, 159.8, 174.8 (C]O), 182.6 (C]O). IR (n/
cmꢀ1): 3427 (NH), 1684, 1615 (C]O), 1595, 1574, 1539 (Ar).
C13H14N2O2 (230.27): calcd. C 67.81, H 6.13, N 12.17; found C 67.75,
H 6.18, N 12.09. MS, m/z (I (%)): 232 [Mþ2]þ (3), 231 [Mþ1]þ (7),
230 [M]þ (19), 202 [MꢀCO]þ (100), 185 [MꢀCOꢀOH]þ (48), 170
(20), 144 (40), 130 (27), 77 (22).
4.11. 4,5-Bis(dimethylamino)-3-nitro-1-trifluoracetamidonaph-
thalene (16)
4.16. Nitration of benzoylamide 12b in AcOH
Yield 4e6%; Rf¼0.62, raspberry-red solid with mp 62e64 ꢁC (n-
A solution of 56% aqueous HNO3 (0.045 mL, 0.50 mmol) was
added to solution of amide 12b (33 mg, 0.10 mmol) in glacial AcOH
(2 mL). The mixture was stirred for 1 h, poured on crashed ice
(20 g), neutralized with aqueous ammonia, and extracted with
CH2Cl2 (3ꢂ10 mL). The extract was washed with water and evap-
orated to dryness. The resulting mixture was chromatographed
(Al2O3, CHCl3), affording compound 13a (Rf¼0.83, 9%) and two
more nitro derivatives with the properties indicated below.
octane). 1H NMR (CDCl3):
d
¼2.82 (s, 6H, 5-NMe2), 2.95 (s, 6H, 4-
NMe2), 7.03 (dd, J¼7.9, J¼1.0, 1H, 6-H), 7.16 (dd, J¼8.2, J¼1.0, 1H,
8-H), 7.47 (dd, J¼8.2, J¼7.9, 1H, 7-H), 7.93 (s, 1H, NH), 7.99 (s, 1H, 2-
H). IR (n
/cmꢀ1): 3256 (NH),1725 (C]O),1579 (Ar),1526,1338 (NO2),
1200e1115 (CeF). C16H17F3N4O3 (370.33): calcd. C 51.89, H 4.63, N
15.13; found C 51.85, H 4.66, N 15.19.
4.12. Nitration of sulfonamide 17 in AcOH
4.17. 1-Benzoylamido-4,5-bis(dimethylamino)-3-nitronaphth-
alene (22)
A solution of 57% aqueous HNO3 (0.054 mL, 0.62 mmol) in gla-
cial AcOH (1 mL) was added dropwise to a solution of amide 1716
(120 mg, 0.31 mmol) in AcOH (4 mL) at 50 ꢁC. The mixture was
stirred for 10 min at 50 ꢁC, poured on ice (20 g), neutralized with
aqueous ammonia (15 mL), and extracted with dichloromethane
(3ꢂ10 mL). The extract was washed with water, evaporated to
dryness, and the mixture was chromatographed (Al2O3, ethyl ace-
tate) to afford major fractions with the next properties.
Yield 9%, Rf¼0.89, orange solid with mp 192e193 ꢁC (EtOAc). 1H
NMR (CDCl3):
d
¼2.82 (s, 6H, 5-NMe2), 2.92 (s, 6H, 4-NMe2), 7.03
(dd, J¼7.4, J¼1.1, 1H, 6-H), 7.36 (dd, J¼8.1, J¼1.1, 1H, 8-H), 7.43 (dd,
J¼7.4, J¼8.1, 1H, 7-H), 7.46e7.62 (m, 3H, 30-H, 40-H, 50-H), 7.89 (br s,
1H, NH), 7.91e7.97 (m, 2H, 20-H, 60-H), 8.09 (s, 1H, 2-H). 13C
NMR (CDCl3):
d
¼43.7 and 44.4 (NMe2), 113.9, 114.6, 118.1, 124.1,

V.A. Ozeryanskii et al. / Tetrahedron 69 (2013) 1919e1929
1927
127.2, 128.4, 128.9, 129.0, 132.1, 134.3, 134.4, 139.2, 144.0, 153.8,
166.5 (C]O). IR (
/cmꢀ1): 3292 (NH), 1646 (C]O), 1580 (Ar), 1522,
1352 (NO2). C21H22N4O3 (378.44): calcd. C 66.65, H 5.86, N 14.81;
found C 66.72, H 5.81, N 14.86.
134.6, 138.9, 152.6, 155.6, 167.9 (C]O). IR (
n
/cmꢀ1): 1722, 1714 (C]
n
O), 1568, 1496 (Ar), 1524, 1366 (NO2). C22H20N4O4 (404.43): calcd. C
65.34, H 4.98, N 13.85; found C 65.40, H 4.95, N 13.88. MS, m/z (I
(%)): 404 [M]þ (26), 358 [MꢀNO2]þ (100), 328 (8), 313 (14), 256
(20), 243 (12), 214 (10), 164 (22), 156 (13), 128 (8), 76 (17), 58 (45),
44 (22), 32 (53).
4.18. 1-Benzoylamido-4,5-bis(dimethylamino)-6-nitronaphth-
alene (23)
4.22. 1-Amino-4,5-bis(dimethylamino)-8-nitronaphthalene (24)
Yield 12%, Rf¼0.96, yellow solid with mp 234e235 ꢁC (EtOAc). 1H
NMR (CDCl3):
d
¼2.81 (s, 6H, 4-NMe2), 2.93 (s, 6H, 5-NMe2), 7.04 (d,
A slight excess of 100% hydrazine hydrate NH2NH2$H2O
J¼8.4, 1H, 3-H), 7.37 (d, J¼9.2, 1H, 8-H), 7.48e7.63 (m, 4H, 7-H, 30-H,
40-H, 50-H), 7.69 (d, J¼8.4,1H, 2-H), 7.83 (br s,1H, NH), 7.92e7.99 (m,
(0.03 mL, 0.62 mmol) was added to a suspension of nitroamide 31
(50 mg, 0.12 mmol) in ethanol (10 mL) with stirring. The resulting
mixture was stirred at 60 ꢁC for 8 h until complete consumption of
the starting amide. The crude product obtained after solvent
evaporation was purified by column chromatography (Al2O3, CHCl3,
Rf¼0.45) to afford 24 (67%) as dark black-maroon crystals with mp
2H, 20-H, 60-H). 13C NMR (CDCl3):
115.2, 122.1, 122.5, 125.6, 126.4, 127.2, 128.9, 132.0, 134.5,
140.3, 145.8, 146.1, 152.2, 166.5 (C]O). IR (
d
¼43.7 and 44.4 (NMe2), 114.0,
n
/cmꢀ1): 3258 (NH), 1650
(C]O), 1578 (Ar), 1524, 1353 (NO2). C21H22N4O3 (378.44): calcd. C
66.65, H 5.86, N 14.81; found C 66.60, H 5.84, N 14.76.
48e50 ꢁC (n-hexane). 1H NMR (CDCl3):
d
¼2.65 (s, 6H, 4-NMe2), 2.97
(s, 6H, 5-NMe2), 3.94 (br s, 2H, 1-NH2), 6.64 (d, J¼8.8, 1H, 6-H), 6.89
4.19. 7-Methylamino-6H-perimidin-6-one (25)
(ABq, J¼8.5, J¼8.5, 2H, 2-H, 3-H), 7.93 (d, J¼8.8, 1H, 7-H). 13C NMR
(CDCl3):
d
¼43.2 and 43.5 (NMe2), 106.9, 115.0, 118.2, 118.6, 121.1,
A solution of amide 13a (or 13b) (38 mg 0.10 mmol) in 20% HCl
(4 mL) was refluxed for 3 h until complete consumption of the
starting material. After that the mixture was poured on ice (20 g),
neutralized with aqueous ammonia to pH 7, and extracted with
chloroform (5ꢂ10 mL). The extract was evaporated and the crude
compound was separated by chromatography (Al2O3, CHCl3,
Rf¼0.73) to give perimidinone 25 (12%) as orange solid (its solutions
possess yellow-orange fluorescence under UV-light and turn
crimson in acids) with mp 148e150 ꢁC (CHCl3). 1H NMR (CDCl3):
127.9, 135.0, 138.3, 145.1, 156.0. IR (CCl4, n
/cmꢀ1): 3438, 3349 (NH2),
2937, 2857, 2830, 2791 (CH), 1576 (Ar), 1524, 1375 (NO2).
C14H18N4O2 (274.32): calcd. C 61.30, H 6.61, N 20.42; found C 61.36,
H 6.55, N 20.38. MS, m/z (I (%)): 275 [Mþ1]þ (12), 274 [M]þ
(100), 228 [MꢀNO2]þ (11), 198 (14), 183 (28), 169 (10), 58 (42), 44
(45), 32 (91).
Tetrafluoroborate 24$HBF4: orange crystals with mp 183e185 ꢁC
(EtOAc). 1H NMR (DMSO-d6):
d
¼3.01 (d, J¼0.9, 6H, 5-NMe2), 3.17 (d,
J¼3.5, 6H, 4-NMe2), 5.34 (br s, 2H, 1-NH2), 7.22 (d, J¼8.5, 1H, 2-H),
8.00e8.10 (m, 3H, 3-H, 6-H, 7-H), 18.25 (br s, 1H, NHNþ).
C14H19BF4N4O2 (326.17): calcd. C 46.44, H 5.29, N 15.47; found C
46.49, H 5.25, N 15.36.
d
¼3.31 (d, J¼5.4, 3H, NMe), 7.28 (d, J¼9.8, 1H, 8-H), 7.62 (d, J¼9.8,
1H, 4-H), 7.92 (d, J¼9.8, 1H, 9-H), 8.15 (d, J¼9.8, 1H, 5-H), 9.35 (s, 1H,
2-H), 11.72 (br s, 1H, NH). IR (CHCl3,
/cmꢀ1): 1636 (C]O), 1604,
n
1577 (Ar). C12H9N3O (211.23): calcd. C 68.24, H 4.29, N, 19.89; found
C 68.25, H 4.22, N 19.80. MS, m/z (I (%)): 212 [Mþ1]þ (14), 211 [M]þ
(100), 194 [MꢀOH]þ (30), 183 [MꢀCO]þ (16), 155 (20), 154 (19), 139
(12), 127 (14), 57 (11), 55 (10), 43 (15), 41 (10).
4.23. Reaction of nitroamide 31 with excess of hydrazine
hydrate
Hydrazine hydrate (0.065 mL, 1.34 mmol) was added to a sus-
pension of amide 31 (50 mg, 0.12 mmol) in ethanol (10 mL) with
stirring. The resulting mixture was stirred at 20 ꢁC for 30 h until
complete consumption of the starting amide. The crude mixture of
products obtained after solvent evaporation was purified by suc-
cessive column chromatography (Al2O3, CHCl3 then silica gel, ethyl
acetate) to afford 32, 33, and 24 (7%) in the order of elution.
4.20. N-(4,5-Bis(dimethylamino)naphthalene-1-yl)phthalimide
(30)
A mixture of amine 11 (0.93 g, 4.05 mmol) and phthalic anhy-
dride (0.60 g, 4.05 mmol) was gradually heated to 190 ꢁC in an oil
bath until no water is released. The resulting melt was cooled and
then chromatographed (Al2O3, ethyl acetate, Rf¼0.60) to give main
yellow-orange fraction. The compound was recrystallized from
ethyl acetate at ꢀ20 ꢁC to afford 30 (830 mg, 60%) as yellow-orange
4.24. 4-Amino-1-methylamino-5-nitronaphthalene (32)
prisms with mp 210e211 ꢁC. 1H NMR (CDCl3):
d¼2.80 (s, 6H, 5-
Yield 15%, dark red crystals with mp 110e112 ꢁC (n-hexane). 1H
NMe2), 2.84 (s, 6H, 4-NMe2), 6.91 (d, J¼7.6, 1H, 6-H), 6.96 (d,
J¼8.2, 1H, 3-H), 7.02 (d, 1H, J¼8.4, 8-H), 7.21e7.30 (m, 2H, 2-H, 7-H),
NMR (CDCl3):
d
¼3.00 (s, 3H, NMe), 3.72 (br s, 3H, NHþNH2), 6.65 (d,
J¼8.1, 1H, 2-H), 6.98 (d, J¼8.1, 1H, 3-H), 7.44 (dd, J¼7.5, J¼8.6, 1H, 7-
7.74e7.85 (m, 2H, 30-H, 40-H), 7.92e8.02 (m, 2H, 20-H, 50-H). IR (
n/
H), 7.68 (dd, J¼7.5, J¼1.2, 1H, 6-H), 8.07 (dd, J¼8.6, J¼1.2, 1H, 8-H).
cmꢀ1): 1777, 1737, 1717 (C]O), 1598, 1573, 1515 (Ar). C22H21N3O2
(359.43): calcd. C 73.51, H 5.89, N 11.69; found C 73.56, H 5.85, N
11.63. MS, m/z (I (%)): 359 [M]þ (83), 344 (26), 328 (74), 313 (84),
256 (10), 209 (18), 195 (10), 181 (12), 168 (100), 154 (25), 140 (26),
130 (31), 115 (14), 104 (36), 76 (92), 58 (27), 44 (85), 32 (92).
13C NMR (CDCl3):
d
¼30.9 (NMe), 106.7, 117.3, 119.2, 121.7, 122.5,
124.5, 125.7, 130.3, 139.3, 147.8. C11H11N3O2 (217.23): calcd. C 60.82,
H 5.10, N 19.34; found C 60.76, H 5.05, N 19.36. MS, m/z (I (%)): 217
[M]þ (100), 200 (29), 171 [MꢀNO2]þ (87), 169 (76), 155 (26), 144
(37), 140 (24), 129 (32), 115 (64), 102 (28), 89 (14), 77 (19), 63 (17),
58 (14), 32 (80).
4.21. N-(4,5-Bis(dimethylamino)-8-nitronaphthalene-1-yl)
phthalimide (31)
4.25. 1-Amino-5-dimethylamino-4-methylamino-8-nitronaph-
thalene (33)
The compound was obtained by mononitration of 30 as de-
scribed above for nitroamides 13. Yield 91%, Rf¼0.75, red-orange
Yield 5%, dark red crystals with mp 80e82 ꢁC (n-hexane). 1H
crystals with mp 249e250 ꢁC (EtOH). 1H NMR (CDCl3):
d¼2.87 (s,
NMR (CDCl3):
d¼2.64 (s, 6H, 4-NMe2), 2.97 (d, J¼5.1, 3H, NHMe), 3.5
6H, 4-NMe2), 2.95 (s, 6H, 5-NMe2), 6.68 (d, J¼8.8, 1H, 6-H), 6.98 (d,
(br s, 2H, NH2), 6.18 (d, J¼8.9, 1H, 6-H), 6.84 (d, J¼8.2, 1H, 2-H), 7.18
(d, J¼8.2, 1H, 3-H), 8.13 (d, J¼8.9, 1H, 7-H). C13H16N4O2 (260.30):
calcd. C 59.99, H 6.20, N 21.52; found C 60.06, H 6.25, N 21.56. MS,
m/z (I (%)): 260 [M]þ (100), 246 (22), 243 (32), 230 (20), 217 (22),
J¼8.4, 1H, 3-H), 7.31 (d, J¼8.4, 1H, 2-H), 7.71e7.81 (m, 3H, 7-H, 30-H,
40-H), 7.87e7.97 (m, 2H, 20-H, 50-H). 13C NMR (CDCl3):
43.7 (NMe2), 107.7, 113.4, 117.0, 117.8, 124.1, 126.9, 128.0, 131.5, 132.1,
d
¼43.6 and

1928
V.A. Ozeryanskii et al. / Tetrahedron 69 (2013) 1919e1929
213 [MꢀHNO2]þ (11), 200 (22), 184 (35), 171 (34), 169 (48), 155 (26),
149 (48), 143 (17), 129 (19), 115 (30), 101 (18), 95 (13), 85 (22),
77 (15), 69 (28), 63 (11), 58 (10), 56 (15), 51 (10), 44 (31), 41 (44),
32 (96).
7.86 (m, 1H, 40-H), 7.92e7.98 (m, 2H, 20-H, 60-H), 17.76 (br s, 1H, NH).
1H NMR (DMSO-d6):
1H, 9-H), 6.92 (d, J¼8.1, 1H, 4-H), 7.52e7.64 (m, 3H, Ph), 7.68e7.81
(m, 2H, 5-H, 8-H), 8.00e8.11 (m, 2H, Ph), 11.14 (br s, 1H, NH), 17.53
(br s, 1H, NHNþ). C21H23BF4N4 (418.25): calcd. C 60.30, H 5.54, N
13.40; found C 60.26, H 5.59, N 13.33.
d
¼3.02 (d, J¼2.0, 12H, NMe2), 6.79 (d, J¼8.4,
4.26. Reaction of amide 13a with zinc in AcOH/DMF
A suspension of Zn-dust (200 mg) in glacial AcOH (0.2 mL) was
added to a solution of amide 13a (100 mg, 0.26 mmol) in DMF
(6 mL). The mixture was stirred for 20 min until the color of the
solution turned from red to yellow, poured on water (20 mL),
neutralized with 20% aqueous KOH to pH 9e10 and extracted with
CHCl3 (3ꢂ10 mL). The solvent was removed and the residue was
chromatographed (silica gel, ethyl acetate) affording the next major
compounds.
4.31. 6,7-Bis(dimethylamino)-2-trifluoromethyl-1H-perimidine
hydrogen tetrafluoroborate (37$HBF4)
Yellow crystals with mp 230e233 ꢁC (MeOH). 1H NMR (CD3OD):
d
¼3.08 (s, 12H, NMe2), 6.86 (d, J¼8.1, 2H, 4-H, 9-H), 7.71 (d, J¼8.1,
2H, 5-H, 8-H), 18.06 (br s, 0.3H, NHNþ). C16H18BF7N4 (410.14): calcd.
C 46.86, H 4.42, N 13.66; found C 46.80, H 4.49, N 13.61.
4.32. N-(4,5-Bis(dimethylamino)-8-nitronaphthalene-1-yl)-
N-methylbenzamide (39)
4.27. 7-Dimethylamino-2-phenyl-4,5-epoxy-6H-perimidin-6-
one (35)
The compound was synthesized by the N-methylation (MeI/
KOH/acetone) of nitroamide 13a according to the method, sug-
gested for the synthesis of amide 38.32 Amide 39 was obtained as
a 4:1 mixture of E and Z isomers with 75% yield as red solid, mp
Yield 18%, Rf¼0.73, yellow solid with mp 182e183 ꢁC (EtOAc). 1H
NMR (CDCl3):
d
¼3.13 (s, 6H, NMe2), 4.23 (d, J¼4.0, 1H, 4-H), 4.74 (d,
J¼4.0, 1H, 5-H), 7.44e7.55 (m, 3H, Ph), 7.65 (d, J¼9.6, 1H, 8-H), 8.03
(d, J¼9.6, 1H, 9-H), 8.54e8.62 (m, 2H, Ph). 13C NMR (CDCl3):
d
¼43.8
155e158 ꢁC (EtOAc/n-hexane). 1H NMR (CDCl3):
d
¼2.60e3.00 (m,
(NMe2), 58.8 and 60.0 (OeCH), 106.1, 121.9, 125.5, 128.0, 128.6,
130.2, 134.6, 137.7, 145.0, 151.5, 157.0, 158.0, 188.3 (C]O). IR (CHCl3,
12H, NMe2), 3.31 (s, 0.61H, Z-CONMe), 3.51 (s, 2.39H, E-CONMe),
6.45 (d, J¼8.4, 0.8H), 6.71 (d, J¼8.6, 0.2H), 6.80 (d, J¼8.3, 0.8H),
6.84e6.93 (m), 6.95e7.04 (m), 7.07e7.13 (m), 7.26 (d, J¼8.3, 0.8H),
n
/cmꢀ1): 1648 (C]O), 1607, 1558 (Ar). C19H15N3O2 (317.35): calcd. C
71.91, H 4.76, N 13.24; found C 71.94, H 4.71, N 13.19. MS, m/z (I (%)):
317 [M]þ (47), 300 [MꢀOH]þ (46), 288 (15), 274 [MꢀOꢀHCN]þ (23),
272 [MꢀCOꢀOH]þ (49), 218 (29), 194 (20), 168 (33), 155 (22), 145
(23), 142 (24), 115 (32), 103 (50), 89 (23), 77 (100), 57 (51), 55 (40),
44 (49), 43 (75), 42 (74).
7.37e7.46 (m), 7.50 (d, J¼8.4, 0.8H), 7.61e7.70 (m). IR (
n
/cmꢀ1):
1650, 1636 (C]O), 1573, 1506 (Ar), 1520, 1333 (NO2). C22H24N4O3
(392.46): calcd. C 67.33, H 6.16, N 14.28; found C 67.37, H 6.10, N
14.22.
4.33. Reductiveheterocyclizationofperi-nitroamides38and 39
4.28. 7-Methylamino-2-phenyl-6H-perimidin-6-one (36)
Yield 4%, Rf¼0.51, orange solid with mp 248e250 ꢁC (EtOAc). 1H
A mixture consisting of the corresponding amide (1 mmol),
MeOH (15 mL) and 5% PdeC (10 mg, about 0.2 if taken from the
mass of the amide) was hydrogenated at room temperature with
shaking until the starting amide is consumed (controlled by TLC
(Al2O3, CHCl3)). After that, the catalyst was filtered off, and the
crude product obtained after solvent evaporation was purified by
TLC (Al2O3, CHCl3) to afford 40 (Rf¼0.55) and 41 (Rf¼0.48).
NMR (CDCl3):
d
¼3.32 (d, J¼5.0, 3H, NMe), 7.29 (d, J¼9.9, 1H, 8-H),
7.42e7.57 (m, 3H, Ph), 7.61 (d, J¼9.7, 1H, 4-H), 8.00 (d, J¼9.9, 1H, 9-
H), 8.24 (dd, J¼9.7, J¼0.8, 1H, 5-H), 8.56e8.63 (m, 2H, Ph), 11.64 (br
s,1H, NH). 13C NMR (CDCl3):
d
¼29.7 (NMe),105.2, 118.9,122.4, 128.1,
128.7, 130.0, 130.9, 137.4, 138.2, 139.0, 145.9, 150.9, 155.0, 158.9,
183.0 (C]O). IR (CHCl3,
n
/cmꢀ1): 1637 (C]O), 1602, 1576 (Ar).
C18H13N3O (287.33): calcd. C 75.25, H 4.56, N 14.62; found C 75.31, H
4.62, N 14.56. MS, m/z (I (%)): 287 [M]þ (14), 270 [MꢀOH]þ (1), 260
[MꢀHCN]þ (3), 259 [MꢀCO]þ (4), 242 [MꢀHCNꢀH2O]þ (4), 155
(12), 154 (19), 144 (28), 139 (26), 127 (24), 103 [PhCN]þ (44), 77
[Ph]þ (100), 76 (56), 51 (85), 43 (71).
4.34. 6,7-Bis(dimethylamino)-1,2-dimethyl-1H-perimidine (40)
Yellow solid with mp 175e177 ꢁC (n-hexane). 1H NMR (CDCl3):
d
¼2.30 (s, 3H, CMe), 2.74 (br s, 12H, NMe2), 3.18 (s, 3H, 1-NMe),
6.22 (br d, J¼7.3, 1H, 9-H), 6.72e6.91 (m, 2H, 5-H, 8-H), 6.95e7.03
(m, 1H, 4-H). C17H22N4 (282.39): calcd. C 72.31, H 7.85, N 19.84;
found C 72.26, H 7.85, N 19.87. MS, m/z (I (%)): 283 [Mþ1]þ (19),
282 [M]þ (100), 267 [MꢀMe]þ (11), 252 [Mꢀ2Me]þ (32), 237
[Mꢀ3Me]þ (38), 222 [Mꢀ4Me]þ (17), 208 (10), 58 (16), 44 (10), 42
(12), 32 (34).
4.29. Reductive heterocyclization of protonated peri-nitro-
amides 13a and 13c
A mixture consisting of the corresponding amide (1 mmol),
MeOH (15 mL), 40% aqueous HBF4 (1.1 mmol, 1.1 equiv), and 5%
PdeC (10 mg, about 0.2 if taken from the mass of the amide) was
hydrogenated at room temperature with shaking until the starting
amide is consumed (controlled by TLC (Al2O3, CHCl3) of a KOH-
basified probe). After that, the catalyst was filtered off and the
clear solution was slowly evaporated to give crude product, which
could be further recrystallized from MeOH or EtOH. The yields were
almost quantitative.
Tetrafluoroborate 40$HBF4: yellow crystals with mp 212e215 ꢁ
C
(EtOH). 1H NMR (CD3CN):
d¼2.56 (s, 3H, CMe), 3.01e3.09 (m, 12H,
NMe2), 3.44 (s, 3H, 1-NMe), 7.02 (d, J¼8.4, 1H, 9-H), 7.14 (d, J¼8.1,
1H, 4-H), 7.75e7.84 (m, 2H, 5-H, 8-H), 17.94 (br s, 1H, NHNþ).
C17H23BF4N4 (370.21): calcd. C 55.16, H 6.26, N 15.13; found C 55.15,
H 6.19, N 15.17.
4.35. 6,7-Bis(dimethylamino)-1-methyl-2-phenyl-1H-peri-
midine (41)
4.30. 6,7-Bis(dimethylamino)-2-phenyl-1H-perimidine hydro-
gen tetrafluoroborate (34$HBF4)
Yellow solid with mp 172e173 ꢁC (n-hexane). 1H NMR
(CDCl3):
d
¼2.69 (br s, 12H, NMe2), 3.04 (s, 3H, 1-NMe), 6.25 (br d,
Yellow crystals with mp 165e166 ꢁC (EtOH). 1H NMR (CD3CN/
J¼7.2, 1H, 9-H), 6.82e7.04 (m, 3H, 4-H, 5-H, 8-H), 7.45e7.55 (m,
5H, Ph). C22H24N4 (344.47): calcd. C 76.71, H 7.02, N 16.27; found
C 76.77, H 7.06, N 16.30. MS, m/z (I (%)): 345 [Mþ1]þ (24), 344
CCl4, 3:2):
d¼3.05 (d, J¼2.7, 12H, NMe2), 7.23 (d, J¼8.4, 2H, 4-H, 9-
H), 7.65e7.74 (m, 2H, 30-H, 50-H), 7.80 (d, J¼8.4, 2H, 5-H, 8-H),

V.A. Ozeryanskii et al. / Tetrahedron 69 (2013) 1919e1929
1929
[M]þ (100), 329 [MꢀMe]þ (16), 314 [Mꢀ2Me]þ (18), 300 (10), 299
References and notes
(29), 298 (44), 284 (14), 283 (14), 58 (23), 44 (20), 42 (10),
32 (70).
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mp 165e168 ꢁC (CHCl3). 1H NMR (CDCl3):
d
¼2.72 (s, 12H, NMe2),
3.31 (s, 6H, 1-NMe, 3-NMe), 6.92 (s, 4H, 4-H, 5-H, 8-H, 9-H),
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Acknowledgements
We thank Dr. Z. A. Starikova (A. N. Nesmeyanov Institute of
Organoelement Compounds of the Russian Academy of Sciences,
Moscow) for performing X-ray diffraction experiments and Dr. O. N.
Burov (Southern Federal University, Rostov-on-Don) for
DFT calculations. Financial support from the Russian Foundation
for Basic Research (project no. 11-03-00073) is gratefully
acknowledged.
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