Ortho-ketimines of 1,8-bis(dimethylamino)naphthalene: Synthesis, hydrolytic stability and transfer of basicity from proton sponge moiety to the imino function

Article abstract of DOI:10.1055/s-0034-1379008

A series of 2-ketimines and 2,7-diketimines of 1,8-bis(dimethylamino)naphthalene (proton sponge, DMAN) have been obtained and converted into the corresponding ketones via acidic hydrolysis. Investigation of structural and spectral properties of DMAN-based imines led to the conclusion that their unusual hydrolytic stability results from a combination of different factors the most important of which is a strong electron-donor effect of peri-dimethylamino groups.

Full text of DOI:10.1055/s-0034-1379008

PAPER
▌3273
poarpetrho-Ketimines of 1,8-Bis(dimethylamino)naphthalene: Synthesis, Hydrolytic
Stability and Transfer of Basicity from Proton Sponge Moiety to the Imino
Function
ortho-Ketimines of 1,8-Bis(dimethylamino)naphthalene
Alexander S. Antonov, Vladimir Y. Mikshiev, Alexander F. Pozharskii,* Valery A. Ozeryanskii
Department of Organic Chemistry, Southern Federal University, Zorge str. 7, 344090 Rostov-on-Don, Russian Federation
Fax +7(863)2975146; E-mail: apozharskii@sfedu.ru
Received: 25.06.2014; Accepted after revision: 31.07.2014
Me2N
NMe2
Me2N
NMe2
Abstract: A series of 2-ketimines and 2,7-diketimines of 1,8-
bis(dimethylamino)naphthalene (proton sponge, DMAN) have
been obtained and converted into the corresponding ketones via
acidic hydrolysis. Investigation of structural and spectral properties
of DMAN-based imines led to the conclusion that their unusual hy-
drolytic stability results from a combination of different factors the
most important of which is a strong electron-donor effect of peri-di-
methylamino groups.
R
Li 1) RCN, Et2O
r.t.
n-BuLi, Et2O
(a)
–20 °C
2) H2O
1a R = H
1b R = Br
2
Me2N
NMe2 NH
3a R = Ph (65%)
3b R = 4-MeOC6H4 (60%)
3c R = 1-naphthyl (68%)
3d R = 3-pyridyl (69%)
3e R = 2-thienyl (89%)
3f R = t-Bu (43%)
R
Key words: amines, imines, hydrolysis, ketones, organometallic
reagents
3
4
Me2N
NMe2 NH
Me2N
NMe2
CN
1) RLi, Et2O
–20 °C to r.t.
Imines are of common interest in organic synthesis, me-
dicinal chemistry, and biochemistry.1 However, in many
cases handling imines, especially those with an unsubsti-
tuted NH group, is difficult due to the ease of their hydro-
lysis. Recently, we obtained two 2-ketimino derivatives of
1,8-bis(dimethylamino)naphthalene (1a, proton sponge,
DMAN), namely 3a,b, and turned our attention to their
enhanced hydrolytic stability.2 To shed light on the origin
of this phenomenon, in the present work we have prepared
a number of new representatives of these compounds with
widely varied structure and studied their properties
(Scheme 1). In particular, we have focused on their hydro-
lytic activity, molecular structure, and mutual influence of
the formally conjugated peri-NMe2 and imino groups.
R
(b)
2) H2O
3f R = t-Bu (55%)
3g R = n-Bu (70%)
3h R = Me (52%)
H
N
Me2N
NMe2
NMe2
Me2N
3i (44%)
Scheme 1
To overcome this difficulty, we were forced to employ the
reversed approach to synthesize alkyl(naphthyl)ketimines
3f–h by the interaction of ortho-cyanide 4 with alkyllithi-
um reagents [Scheme 1 (b); notably the use of alkylmag-
nesium halides for this purpose failed]. To our
satisfaction, imines with butyl and methyl groups 3g,h
were obtained in good yields. Even for imine 3f contain-
ing the tert-butyl group the protocol increased the yield by
12% to 55%. Actually, both approaches were merged
when 2-Li-DMAN 2 was allowed to react with nitrile 4 to
produce symmetrical binaphthylketimine 3i (44%).
Monoketimines 3a–f were synthesized in 60–89% yields
by combining aryl and hetaryl cyanides with 1,8-bis(di-
amino)-1-lithionaphthalene (2, 2-Li-DMAN) generated
from bromide 1b [Scheme 1 (a)].3 The reaction proceeded
with more difficult for alkyl cyanides, apparently due to
the enhanced acidity of their α-CH bonds causing protol-
ysis of 2 [compare with the reactions of 2-lithium and 2,7-
dilithium derivatives of 1,8-bis(dimethylamino)naphtha-
lene with acetyl chloride3]. Thus, on treatment of 2-Li-
DMAN 2 with acetonitrile or valeronitrile the correspond-
ing imines were not formed at all and only unsubstituted
DMAN 1a was isolated from the reaction mixture. Use of
tert-butyl cyanide, containing no α-CH bonds, was more
successful and the yield of imine 3f reached 43%.
Taking into account the higher nucleophilicity of 1,8-
bis(dimethylamino)-2,7-dilithionaphthalene (6, 2,7-Li2-
DMAN) in comparison with 2-Li-DMAN 2 and to con-
firm that two NMe2 groups can stabilize two ortho-imino
functionalities towards hydrolysis, it was also important
to synthesize 2,7-diketimines of 1a. Interaction of 2,7-Li2-
DMAN 6 with benzonitrile or 4-methoxybenzonitrile
gave diimines 7a,b in 14% and 11% yields, respectively,
along with ~30% yield of the corresponding monoke-
timines 3a,b (Scheme 2).
SYNTHESIS 2014, 46, 3273–3282
Advanced online publication: 26.08.2014
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DOI: 10.1055/s-0034-1379008; Art ID: ss-2014-t0392-op
© Georg Thieme Verlag Stuttgart · New York

3274
A. S. Antonov et al.
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Me2N
NMe2
Me2N
NMe2
Me2N
NMe2
1) PhLi (2 equiv)
Et2O
Me2N
NMe2
HN
Ph
NH
Ph
n-BuLi
(2 equiv)
1) RCN (2 equiv)
Et2O, –20 °C
NC
CN
Br
Br
Li
Li
25 °C, 24 h
2) H2O
Et2O, –20 °C
2) H2O
6
5
10
7a (46%)
Me2N
NMe2 NH
HN Me2N
NMe2 NH
Scheme 4
R
R
R
+
CDCl3, the NH proton resonates at δ = 8.7–9.5 as a broad
peak (up to 1 ppm wide) visible only at high concentra-
tions (~0.3 М). In DMSO-d6 this signal is considerably
narrowed and shifts to a lower field (δ = 9.5–10.8, see the
Supporting Information, Section SI-1). The carbon signal
of the C=N group in the 13C NMR spectra resonating with-
in δ = 179–193 is also very characteristic. The IR spectra
of all imines in CCl4 solution contain a rather sharp peak
νNH at 3250–3265 cm–1 (Table 1, see also the Supporting
Information, section SI-2). These data make the engage-
ment of the C=NH groups in hydrogen bond formation
unlikely.
3a R = Ph (32%)
3b R = 4-MeOC6H4 (28%)
7a R = Ph (14%)
7b R = 4-MeOC6H4 (11%)
Scheme 2
These results leave no doubt that under these conditions
2,7-Li2-DMAN 6 undergoes considerable (mono)protoly-
sis into 2-Li-DMAN 2, which then is converted into
monoimine.
To improve the yield of compounds 7, we tested a step-
wise introduction of the imino groups. For this, dibromide
5 on treatment with one equivalent of butyllithium was
transformed into less basic 2-bromo-7-lithio-1,8-bis(di-
methylamino)naphthalene (8),3 to which aryl cyanide, bu-
tyllithium, and again aryl cyanide were sequentially added
in a one-pot mode (Scheme 3). In accord with our assump-
tion, this protocol provided a nearly fourfold increase in
the yields of diimines 7a,b, although due to the low solu-
bility of the intermediate salt 9 the introduction of the sec-
ond imino group occurred under heterogeneous
conditions and was accompanied by the formation of
some unidentified side products. Quenching the process
by water addition just after the stage 8 → 9 allowed us to
isolate imine 3j with the bromine atom in position 2
(Scheme 3) thus opening up the possibility for further
functionalization of the imine structure.
All proton sponge ortho-imines are crystalline (except
3g,h) yellow-, orange-, or red-colored compounds. Their
electronic spectra, as in the case of DMAN 1a,4 contain
the long-wavelength absorption band at 350 nm (Table 1).
However, unlike DMAN 1a, this band does not tail off at
400 nm (except for 3f) but extends into the visible region
up to 440–450 nm (Supporting Information, section SI-3).
This end absorption differs by low intensity and is likely
caused by n → π* electron transition within the imino
group.
X-ray crystal structure experiments were performed for
three of the obtained imines, 3b, 3f, and 3i; their results
are shown in Figure 1 and Table 2. All imines display con-
siderable molecular distortions. Thus, the rotation angle
of the 1-NMe2 group relatively the average ring plane in
molecules 3b, 3f, and 3i varies in the limits of 53–56°
while the dihedral angle C1–C2–CN changes from 37° in
3i to 126° in 3b. The angle between the two naphthalene
planes in 2,2′-binaphthylimine 3i is equal to 81.6° which
is close to that in the proton sponge-based 2,2′-binaph-
thylmethanols.5 Although such distortions should affect
the interaction between the peri-NMe2 and the imino
groups, their conjugation is still clearly distinguishable.
For example, the C=N bonds in molecules 3b and 3i are
lengthened by 0.15–0.20 Å in comparison with imines of
the benzene series.6 Owing to the bulkiness of the tert-bu-
tyl group, the structure of imine 3f reveals some specifics.
First, the 1-NMe2 group is out-inverted, likely because its
methyls are pushed by the tert-butyl group into the peri in-
ternitrogen space; the free amine nitrogen electron pairs in
3b and 3i remain in-inverted but the 1-NMe2 groups un-
dergo considerable planarization with ΣN = 358.6 (359.2)
and 354.5°, respectively. The nitrogen inversion in 3f is
accompanied, as in other similar cases,3,5 by substantial
increase of the N1···N8 distance: 2.90 Å in 3f against 2.80
and 2.76 Å in 3b and 3i. The dihedral angle C1–C2–CN,
as well as the naphthalene ring twisting (the angle be-
tween the C2–C3 and C6–C7 bonds)7 in 3f are also larger
Me2N
NMe2
Me2N
NMe2
NLi
Ph
RCN
Li
Br
n-BuLi
Br
(1 equiv)
(1 equiv)
5
Et2O, –20 °C
Et2O, –20 °C
8
9
1) n-BuLi (1 equiv)
2) RCN (1 equiv)
–20 °C, 24 h
3) H2O
H2O
Me2N
Br
NMe2
NH
Ph
7a (40%)
7b (48%)
3j (41%)
Scheme 3
To check the applicability of the reversed approach (vide
supra) for the synthesis of diimines we reacted 2,7-dicya-
no-1,8-bis(dimethylamino)naphthalene (10) with two
equivalents of phenyllithium; the reaction gave diimine
7a in 46% yield (Scheme 4).
The most interesting aspect in the 1H NMR spectra of the
obtained imines is the appearance of the NH group. In
Synthesis 2014, 46, 3273–3282
© Georg Thieme Verlag Stuttgart · New York

PAPER
ortho-Ketimines of 1,8-Bis(dimethylamino)naphthalene
3275
than those in 3b and 3i. Lastly, the C=N bond in imine 3f group, thus making the site of first protonation less unam-
is shortened which makes its involvement in conjugation biguous [a typical example of such a phenomenon is
with the ring π-system and the NMe2 groups unlikely.
found for 1,3,5-tris(dialkylamino)benzenes which are
protonated at ring carbon atoms9]. The latter assumption
was partially confirmed by studying the most hydrolyti-
cally stable imine 3b. We prepared the monoperchlorate
All imines exist in the syn form relatively to the C=N dou-
ble bond (apart from 3i, for which the syn and anti forms
are indistinguishable) with the N–H bond turned away
from the 1-NMe2 group that excludes the formation of the
intramolecular hydrogen bond between them.
1
of 3b and recorded its H NMR spectra in DMSO-d6. It
was found that under these conditions the salt exists as a
mixture of two forms 11 and 12 with the proton localized
either between the NMe2 groups or at the imine nitrogen
(Scheme 5), the second form being predominant in a ca.
2:1 ratio; this proportion can be best estimated from the
relative intensity of two signals of the OMe groups at
δ = 3.8–3.9. Both forms are also easily identified with re-
gard to the position of the NH proton: in 11 the chelated
proton resonates at δ = 18.6, a usual region for all proton
sponge cations,4 while the signal of the protonated imino
group C=NH2+ in 12 appears at δ = 11.9 (Supporting In-
formation, section SI-4a).
As the proton sponge ketimines contain two different ba-
sic centers (chelating NMe2 groups and the imine nitro-
gen), the relative ease and sequence of their protonation
are of importance. It would seem that the first protonation
should proceed at peri-NMe2 groups with the formation of
the chelated cation of type 11. Indeed, the basicity of the
benzophenone imine (pKa = 6.82) and even that of cyclo-
hexanone imine (pKa = 9.15)8 is much lower than that of
DMAN 1a (pKa = 12.1).4 However, since in the proton
sponge ketimines the NMe2 and the C=NH groups are for-
mally conjugated, some part of the electron density may
be transferred towards the electron-accepting imino
Table 1 Selected Spectral Characteristics of Proton Sponge Imines
Imine
IR (CCl4) ν (NH) (cm–1)
1H NMR δ (NH)
13C NMR (CDCl3) δ (C=N) UV (MeCN) λmax (nm) (log ε)
CDCl3
DMSO-d6
3a
3b
3c
3d
3e
3263
3266
3252
3262
3273
9.48
8.88
10.23
180.72
179.81
180.35
178.86
173.93
250 (4.47)
343 (3.79)
9.96
255 (4.43)
342 (3.76)
a
–
10.78
10.61
9.90
282 (4.16)b
346 (3.79)b
9.68
248 (3.76)
342 (4.35)
a
–
252 (4.50)b
288 (4.19)b
332 (3.86)b
3f
3253
3251
3250
3251
3265
3264
3266
9.35
9.10
10.04
9.86
192.77
186.16
182.4
242 (4.73)b
344 (4.10)
3g
3h
3i
294 (4.34)
343 (3.81)
a
–
9.69
248 (4.52)b
344 (3.94)
9.52
9.30
8.69
–
9.0–10.5c
10.30
10.39
9.86
179.31
180.06
180.39
177.49d
260 (4.76)
348 (4.14)
3j
254 (4.49)
337 (3.75)
7a
7b
258 (4.82)
358 (4.08)
263 (4.46)
356 (3.68)
a The signal is extremely broad and difficult to determine.
b Center of shoulder.
c In CD3CN.
d In DMSO-d6.
© Georg Thieme Verlag Stuttgart · New York
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3276
A. S. Antonov et al.
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content of form 11. Obviously, the enlargement results
+
from merging of signals of the C=NH and C=NH2 groups
in 11 and 12a owing to their fast exchange on the NMR
timescale. This is a vivid illustration of the difference in
behavior of kinetically active and kinetically inert basic
centers within the same molecule. One cannot exclude
that cation 12 exists in two isoenergetic chelated forms
12b′ and 12b′′ with slowly exchangeable NH protons and
the out-inverted 1-NMe2 group. Indirectly, strong broad-
+
ening of the C=NH2 group signals (over 1 ppm) favors
this hypothesis; possibly this may reflect dynamics of the
rechelation process (cf. ref.10). Regrettably, we have so far
failed to study temperature-dependent NMR spectra of
perchlorate 3b·HClO4 because of its very bad solubility in
common low-freezing solvents.
Next we attempted to estimate the basicity of imine 3b us-
ing NMR competitive proton exchange.11 For this, the
precise amount of DMAN 1a (1 equiv) was added to a
1
solution of 3b·HClO4 in DMSO-d6. The H NMR spec-
trum of the resulting mixture (Supporting Information,
section SI-4b) showed that form 11 was completely
deprotonated by DMAN 1a. This conclusion follows from
replacing peak at δ = 18.6 by that at δ = 18.3 which is
characteristic for the protonated DMAN 1a.4 At the same
time only about 40% of DMAN 1a underwent protonation
in this experiment. Both observations suggest that: (1) the
basicity of the proton sponge moiety in 3b is at least two
orders of ten lower than that of the parent proton sponge
and (2) basicities of 3b as imine and as DMAN are quite
comparable. Unfortunately, we failed to make more exact
estimation of the pKa values for 3b due to a strong broad-
ening of some peaks in the 1H NMR spectra of this mix-
ture. It is only possible to conclude that under these
conditions DMAN 1a deprotonates form 11 completely
and forms 12a partially, entering with the latter in a slow
proton exchange.
Figure 1 Molecular structures of imines 3b (a), 3f (b), 3i (c)
Me
Me
N
H
+
+
Me2N
Me2N
NMe2
NH2
NH
HClO4
+
3b
–
–
ClO4
OMe
OMe
ClO4
12a
11
?
Me
Me
Me2N
Me
Me
Me2N
Hb
Ha
Ha
Hb
+
N
N
+
N
N
Finally, we performed an acidic hydrolysis of the ke-
timines in 10% hydrochloric acid under reflux. As a re-
sult, a series of ketones 13 and 14 were obtained generally
in good to moderate yield (Table 3). The time to complete
the reaction and the yield of ketones allows the imines to
be arranged in the order of their hydrolytic stability. As
seen, the most stable are imines 3b, 3e, and 7b. Imine 3f
containing the bulky and hydrophobic tert-butyl group
was also hydrolyzed slowly. In contrast, imines with n-al-
kyl, phenyl, and pyridyl substituents at the C=NH group
OMe
OMe
–
–
ClO4
ClO4
12b''
12b'
Scheme 5
Interestingly, the intensity of the C=NH2+ peak for 12a is
enlarged by 25%, which almost exactly corresponds to
Table 2 Selected Geometrical Parameters of Some Imines (X-ray Diffraction Data)
Compound Bond lengths and distances (Å)
C=N peri-N···N
ΣN for 1-NMe2 (°) Dihedral angles (°)
1-NMe2 and C1···C10 C1–C2 and C=N C2–C3 and C6–C7
T (K)
3b
3f
3i
1.285 (1.293)a 2.817 (2.797)a
359.2 (358.6)a
355.2
50.6 (52.9)a
55.9
126.2 (117.0)a
90.4
14.4 (11.9)a
15.4
120
100
120
1.270
1.288
2.903
2.758 (2.754)b
354.5 (354.9)b
56.2 (57.2)b
36.9 (40.2)b
11.3 (12.1)b
a For the second independent molecule.
b For the second proton sponge fragment.
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ortho-Ketimines of 1,8-Bis(dimethylamino)naphthalene
3277
are relatively active. The hydrolytic behavior of symmet- It seemed reasonable to compare the hydrolytic stability
rical imine 3i with two DMAN moieties is very specific of imines 3 with their benzene analogues. With this aim,
and will be discussed in a separate communication.
2-(dimethylamino)benzophenone imine (15)12 was pre-
pared as shown in Scheme 6 and then hydrolyzed to ke-
tone 16. As expected, 15 also revealed noticeable stability
on heating in acids but nonetheless it was four times lower
in comparison with 3a.
Table 3 Results of Acidic Hydrolysis of Ketimines 3 and 7 (Reflux
in 10% HCl)
Imine Time Product
(h)
Yield
(%)
NMe2
NMe2
NMe2
NH
Ph
O
1) PhCN
Et2O, –20 °C
Me2N
Me2N
NMe2
NMe2
Li
O
10% HCl
3a
2
13a
99
Ph
2) H2O
Δ, 0.5 h
Ph
16 (99%)
15 (77%)
Scheme 6
O
3b
32
13b
78
From the above it can be concluded that the considerable
hydrolytic inertness of the proton sponge ketimines can be
caused by a combination of electronic and steric factors.
In our opinion, the most important of them is a pro-
nounced electron-donor effect of the peri-NMe2 groups
lowering the electrophilicity of the carbon atom in the
protonated imino group (see resonance structures 17a–d
in Scheme 7).
OMe
Me2N
Me2N
NMe2
NMe2
O
O
3c
3d
3e
3
1
13c
13d
13e
72
65
56
+
Me2N
NMe2 NH
Me2N
NMe2 NH2
+
R
R
N
O
Me2N
NMe2
17a
17b
+
+
Me2N
NMe2 NH2
Me2N
NMe2 NH2
12
S
R
R
Me2N
Me2N
Me2N
NMe2
NMe2
NMe2
O
O
O
17c
17d
3f
8
1
1
1
1
13f
13g
13h
13j
14a
10
78
77
85
80
Scheme 7
Solution H and 13C NMR experiments were performed with a
Bruker DPX-250 spectrometer (250 MHz for 1H, 63 MHz for 13C)
using the solvent residual peaks as the internal reference. FT-IR
spectra were measured on a FSM-1202 spectrophotometer. UV/vis
spectra were measured on a Varian Cary 50 Probe spectrophotome-
ter. MS were obtained from Finnigan MAT INCOS 50 instrument
(EI, 70 eV) and on a Bruker micrOTOF II instrument (ESI). All re-
agents and starting materials were obtained from commercial sourc-
es and used without further purification.
1
3g
3h
3j
Me
Me2N
NMe2
O
Br
X-ray diffraction analysis. Crystals suitable for X-ray studies were
grown up by slow evaporation from solutions of compounds in ap-
propriate solvents or solvent mixtures: Et2O–hexane–acetone for
3b, CHCl3 for 3f, MeCN–EtOH for 3i. X-ray measurements were
conducted with Bruker SMART 1000 (for 3i, MoKα line, graphite
monochromator, ω/2θ-scanning) and Bruker APEX II diffractome-
ters (for 3b and 3f, Mo-Kα line, graphite monochromator, ω-scan-
ning). The structures were solved by direct method and refined by
the full-matrix least-squares against F2 in anisotropic (for non-hy-
drogen atoms) approximation. All hydrogen atoms were placed in
geometrically calculated positions and were refined in isotropic ap-
proximation in riding model with the Uiso(H) parameters equal to
n·Ueq(Ci) (n = 1.2 for CH and CH2 groups and n = 1.5 for CH3
groups), where U(Ci) are respectively the equivalent thermal pa-
rameters of the atoms to which corresponding H atoms are bonded.
Ph
Me2N
NMe2
O
O
7a
Ph
Ph
Me2N
NMe2
O
O
7b
26
14b
55
MeO
OMe
© Georg Thieme Verlag Stuttgart · New York
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A. S. Antonov et al.
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The H(N) hydrogen atoms were found in difference Fourier synthe-
sis and refined in isotropic approximation in riding model with the
Uiso(H) parameters equal to 1.2 Ueq(Ni), where U(Ni) are the equiv-
alent thermal parameters of the N atom to which corresponding H
atom is bonded. The main crystallographic data and some experi-
mental details are given in the Supporting Information (section SI-
5). CCDC 1009757–1009759 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from the Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
1H NMR (DMSO-d6): δ = 2.47 (s, 6 H), 2.66 (s, 6 H), 7.04 (d,
J = 7.5 Hz, 1 H), 7.14 (d, J = 5.3 Hz, 1 H), 7.23 (d, J = 8.0 Hz, 1 H),
7.67–7.31 (m, 6 H), 8.03–7.89 (m, 2.2 H), 9.05 (s, 0.8 H), 10.64 (s,
0.2 H), 10.78 (s, 0.8 H).
13C NMR (CDCl3): δ = 44.2, 45.3, 114.5, 122.5, 123.3, 123.8,
124.4, 125.9, 126.2, 126.6, 126.9, 128.0, 128.3, 128.6, 130.4, 131.1,
134.3, 134.6, 137.8, 138.8, 147.6, 152.5, 180.4.
MS (EI): m/z (%) = 43 (22), 57 (21), 126 (24), 127 (75), 128 (27),
141 (26), 153 (51), 154 (50), 155 (27), 167 (35), 168 (59), 240 (42),
322 (34), 323 (75), 336 (57), 351 (55), 352 (73), 367 [M]+ (100),
368 (28).
Imines 3c–f,i Starting from 1,8-Bis(dimethylamino)-2-lithio-
naphthalene (2); General Procedure 1 (GP1)
UV/vis (MeCN): λmax (log ε) = 282 (4.16), 282 (4.16) sh, 346 nm
(3.79) sh.
To a solution of 1,8-bis(dimethylamino)-2-lithionaphthalene (2)
obtained by standard techniques3 from 2-bromo-1,8-bis(dimethyl-
amino)naphthalene (1b, 1000 mg, 3.4 mmol), a solution of the cor-
responding nitrile in anhyd Et2O (10 mL) was added via syringe
under an argon atmosphere at –20 °C. The red-colored mixture was
kept at r.t. for 24–96 h and then treated with distilled H2O (10 mL).
The yellow ether solution was separated and the aqueous phase was
extracted with CHCl3 (3 × 10 mL). The organic fractions were com-
bined, evaporated, and chromatographed (alumina). The synthesis
of imines 3a and 3b was published earlier.2
Anal. Calcd for C25H25N3: C, 81.71; H, 6.86; N, 11.43. Found: C,
81.84; H, 6.75; N, 11.41.
2-[Imino(pyridin-3-yl)methyl]-N1,N1,N8,N8-tetramethylnaph-
thalene-1,8-diamine (3d)
Prepared according to GP1 from 3-cyanopyridine (396 mg, 3.8
mmol). Reaction time: 24 h. Orange crystals; yield: 740 mg (69%);
mp 153–155 °С (n-octane); Rf = 0.2 (alumina, Et2O–n-hexane, 1:1).
IR (CCl4): 3263 (NH), 3084, 3055, 2958, 2931, 2861, 2829, 2784
cm–1 (CH).
1H NMR (CDCl3): δ = 2.60 (s, 6 H), 2.71 (s, 6 H), 7.01 (dd, J = 7.0,
1.1 Hz, 1 H), 7.17 (d, J = 8.3 Hz, 1 H), 7.42–7.21 (m, 3 H), 7.44 (d,
J = 8.3 Hz, 1 H), 7.88 (d, J = 7.3 Hz, 1 H), 8.60 (dd, J = 4.7, 1.4 Hz,
1 H), 8.76 (d, J = 1.0 Hz, 1 H), 9.68 (s, 1 H).
1H NMR (DMSO-d6): δ = 2.51 (s, 6 H), 2.68 (s, 6 H), 7.04 (d,
J = 7.4 Hz, 1 H), 7.18 (d, J = 7.6 Hz, 1 H), 7.48–7.30 (m, 3 H), 7.53
(d, J = 8.3 Hz, 1 H), 7.76 (d, J = 6.3 Hz, 1 H), 8.70–8.47 (m, 2 H),
10.61 (s, 1 H).
13C NMR (CDCl3): δ = 44.7, 45.4, 77.0, 77.5, 78.0, 114.8, 122.6,
123.3, 123.4, 123.7, 127.1, 127.2, 132.0, 135.5, 135.6, 139.1, 147.7,
150.0, 151.7, 152.6, 178.9.
Imines 3f–h Starting from 2-Cyano-1,8-bis(dimethylami-
no)naphthalene (4); General Procedure 2 (GP2)
To a solution of 2-cyanonaphthalene 4 (1000 mg, 4.2 mmol) in abs
Et2O (20 mL), a solution of the corresponding alkyllithium was add-
ed via syringe under an argon atmosphere at –20 °C. The red-col-
ored mixture was kept at r.t. for 24 h and treated with H2O (10 mL).
The yellow ether solution was separated and the aqueous phase was
extracted with CHCl3 (30 mL). The organic fractions were com-
bined, evaporated, and chromatographed (alumina).
Imines 7a,b Starting from 2,7-Dibromo-1,8-bis(dimethylami-
no)naphthalene (5); General Procedure 3 (GP3)
To a solution of dibromonaphthalene 5 (1000 mg, 2.6 mmol) in an-
hyd Et2O (50 mL), 1.6 M BuLi in hexanes (1.6 mL, 2.6 mmol) was
added via syringe under an argon atmosphere at –20 °C. After stir-
ring for 10 min, a solution of the corresponding nitrile (2.6 mmol)
in anhyd Et2O (10 mL) was added via syringe. The red-colored mix-
ture was kept at –20 °C for 24 h. Then 1.6 M BuLi in hexanes (1.6
mL, 2.6 mmol) was added via syringe. Again, after stirring for 10
min, a solution of the corresponding nitrile (2.6 mmol) in anhyd
Et2O (10 mL) was added via syringe. The resulted suspension was
kept at –20 °C for 24 h and treated with H2O (10 mL). The yellow
ether solution was separated and the aqueous phase was extracted
with CHCl3 (3 × 10 mL). The organic fractions were combined,
evaporated, and chromatographed (alumina).
MS (EI): m/z (%) = 29 (26), 30 (36), 32 (86), 42 (68), 43 (27), 44
(100), 51 (36), 78 (42), 105 (35), 115 (20), 127 (35), 128 (22), 154
(23), 167 (20), 168 (42), 274 (35), 287 (45), 302 (39), 303 (27), 318
[M]+ (56).
UV/vis (MeCN): λmax (log ε) = 342 (3.76), 248 nm (4.35).
Anal. Calcd for C20H22N4: C, 75.44; H, 6.96; N, 17.60. Found: C,
75.53; H, 6.88; N, 17.59.
2-[Imino(thiophen-2-yl)methyl]-N1,N1,N8,N8-tetramethylnaph-
thalene-1,8-diamine (3e)
Prepared according to GP1 from thiophene-2-carbonitrile (0.33 mL,
3.5 mmol). Reaction time: 24 h. Orange crystals; yield: 975 mg
(89%); mp 117–119 °С (n-hexane); Rf = 0.7 (alumina, Et2O–n-hex-
ane, 2:1).
Ketones 13 and 14 by Hydrolysis of Imines 3 and 7; General
Procedure 4 (GP4)
The imine (100 mg) was dissolved in 10% aq HCl (10 mL). The re-
sulting solution (mostly dark red in color) was refluxed for 1–32 h
and neutralized by 10% aq NH3. The product was extracted with
CHCl3 and chromatographed on alumina.
IR (CCl4): 3273 (NH), 3078, 3056, 2976, 2935, 2904, 2868, 2860,
2829, 2782 cm–1 (CH).
1H NMR (CDCl3): δ = 2.79 (s, 6 H), 2.80 (s, 6 H), 7.07–6.98 (m, 3
2-[Imino(naphthalen-1-yl)methyl]-N1,N1,N8,N8-tetramethyl-
naphthalene-1,8-diamine (3c)
Prepared according to GP1 from 1-cyanonaphthalene (536 mg, 3.5
mmol). Reaction time: 24 h. Yellow crystals; yield: 850 mg (68%);
mp 58–60 °С (n-hexane); Rf = 0.5 (alumina, Et2O–n-hexane, 2:1).
In DMSO solution 3c exists as a mixture of syn- and anti-forms (see
1H NMR in DMSO-d6).
H), 7.20 (d, J = 8.3 Hz, 1 H), 7.50–7.30 (m, 4 H).
1H NMR (DMSO-d6): δ = 2.69 (s, 6 H), 2.72 (s, 6 H), 6.80 (d,
J = 2.6 Hz, 1 H), 7.06–6.99 (m, 2 H), 7.09 (d, J = 8.3 Hz, 1 H), 7.33
(t, J = 7.6 Hz, 1 H), 7.41 (dd, J = 7.9, 1.0 Hz, 1 H), 7.46 (d, J = 8.3
Hz, 1 H), 7.69 (d, J = 4.9 Hz, 1 H), 9.90 (s, 1 H).
13C NMR (CDCl3): δ = 44.6, 44.8, 114.1, 122.6, 122.0, 122.9,
126.4, 126.5, 127.4, 129.9, 131.4, 131.7, 138.5, 145.7, 147.2, 152.1,
173.9.
IR (CCl4): 3252 (NH), 3084, 3054, 2976, 2934, 2903, 2860, 2828,
2783 cm–1 (CH).
1H NMR (CDCl3): δ = 2.70 (s, 6 H), 2.82 (s, 6 H), 7.12 (d, J = 7.3
Hz, 1 H), 7.64–7.34 (m, 8 H), 8.00–7.85 (m, 2 H), 8.84 (s, 1 H), 9.63
(s, 1 H).
MS (EI): m/z (%) = 42 (16), 44 (11), 97 (13), 110 (20), 127 (19), 139
(16), 154 (19), 167 (13), 168 (28), 195 (10), 263 (12), 279 (31), 292
(65), 293 (11), 307 (69), 308 (37), 323 [M]+ (100), 324 (19).
Synthesis 2014, 46, 3273–3282
© Georg Thieme Verlag Stuttgart · New York

PAPER
ortho-Ketimines of 1,8-Bis(dimethylamino)naphthalene
3279
UV/vis (MeCN): λmax (log ε) = 224 (5.13), 252 (4.50), 288 (4.19) sh,
332 nm (3.86).
Hz, 1 H), 7.37 (d, J = 7.7 Hz, 1 H), 7.43 (d, J = 8.3 Hz, 1 H), 9.69
(br s, 1 H).
Anal. Calcd for C19H21N3S: C, 70.55; H, 6.54; N, 12.99. Found: C,
70.66; H, 6.61; N, 12.91.
13C NMR (63 MHz, CDCl3): δ = 44.3, 45.1, 114.2, 122.2, 123.2,
123.3, 125.2, 126.2, 134.8, 138.2, 145.9, 152.1, 182.0.
UV/vis (MeCN): λmax (log ε) = 224 (5.07), 248 (4.52) sh, 344 nm
(3.94).
2-(1-Imino-2,2-dimethylpropyl)-N1,N1,N8,N8-tetramethylnaph-
thalene-1,8-diamine (3f)
Prepared according to GP1 from pivalonitrile (0.4 mL, 3.5 mmol).
Reaction time: 24 h. Beige crystals; yield: 435 mg (43%); mp 129–
131 °С (n-heptane); Rf = 0.3 (alumina, Et2O–n-hexane, 1:1).
Anal. Calcd for C16H21N3: C, 75.26; H, 8.29; N, 16.46. Found: C,
75.30; H, 8.26; N, 16.45.
2,2′-(Iminomethylene)bis(N1,N1,N8,N8-tetramethylnaphtha-
lene-1,8-diamine) (3i)
Prepared according to GP1 from 2-cyanonaphthalene 4 (894 mg,
3.7 mmol). Reaction time: 96 h. Orange crystals; yield: 723 mg
(44%); mp 125–128 °С (n-hexane); Rf = 0.7 (alumina, Et2O–n-hex-
ane, 2:1).
Alternatively prepared according to GP2 from 1.7 M t-BuLi in pen-
tane (3.9 mL, 7.9 mmol). Reaction time: 24 h. Yield: 690 mg (55%).
IR (CCl4): 3253 (NH), 3082, 3056, 2965, 2932, 2903, 2869, 2827,
2783 cm–1 (CH).
1H NMR (CDCl3): δ = 1.26 (s, 9 H), 2.72 (s, 6 H), 2.87 (s, 6 H), 7.03
(d, J = 8.3 Hz, 2 H), 7.40–7.23 (m, 3 H), 9.35 (s, 1 H).
IR (CCl4): 3251 (NH), 3054, 2974, 2934, 2903, 2861, 2828, 2781
cm–1 (CH).
1H NMR (250 MHz, CDCl3): δ = 2.80 (s, 12 H), 2.84 (s, 12 H), 7.03
1H NMR (DMSO-d6): δ = 1.19 (s, 9 H), 2.72 (s, 6 H), 2.85 (s, 6 H),
7.02 (d, J = 8.3 Hz, 1 H), 7.10 (d, J = 7.4 Hz, 1 H), 7.33 (t, J = 7.7
Hz, 1 H), 7.45 (dd, J = 8.1, 2.9 Hz, 2 H), 10.04 (s, 1 H).
(dd, J = 6.8, 1.3 Hz, 2 H), 7.42–7.25 (m, 8 H).
13C NMR (CDCl3): δ = 30.4, 40.5, 45.3, 45.8, 114.6, 122.9, 124.5,
125.7, 126.1, 136.4, 137.9, 145.6, 152.5, 192.8.
1H NMR (250 MHz, CDCl3, 212 K): δ = 3.20–2.42 (m, 24 H), 7.12–
6.83 (m, 2 H), 7.48–7.07 (m, 8 H), 9.52 (s, 1 H).
MS (EI): m/z (%) = 32 (33), 196 (11), 225 (36), 240 (100), 241 (16),
1H NMR (250 MHz, CD3CN): δ = 2.17 (s, 12 H), 2.81 (s, 12 H),
7.13 (dd, J = 6.7, 1.6 Hz, 2 H), 7.50–7.26 (m, 8 H), 9.0–10.5 (br s,
1 H).
13C NMR (63 MHz, CDCl3): δ = 44.7, 45.8, 77.0, 77.5, 78.0, 114.8,
122.7, 123.0, 124.7, 126.8, 128.2, 132.4, 139.2, 148.8, 153.0, 179.3.
HRMS (ESI): m/z [M + H]+ calcd for C29H35N5: 454.6282; found:
454.2937.
297 [M]+ (13).
UV/vis (MeCN): λmax (log ε) = 242 (4.73) sh, 344 nm (4.10).
Anal. Calcd for C19H27N3: C, 76.72; H, 9.15; N, 14.10. Found: C,
76.81; H, 9.22; N, 13.97.
2-(1-Iminopentyl)-N1,N1,N8,N8-tetramethylnaphthalene-1,8-di-
amine (3g)
Prepared according to GP2 from 1.6 M BuLi in hexanes (2.7 mL,
6.7 mmol). Orange oil; yield: 880 mg (70%); Rf = 0.5 (alumina,
Et2O–n-hexane, 1:1).
UV/vis (MeCN): λmax (log ε) = 348 (4.14), 260 (4.76), 259 (4.77),
256 (4.75), 219 (4.71), 213 nm (4.73).
Anal. Calcd for C29H35N5: C, 76.78; H, 7.78; N, 15.44. Found: C,
76.86; H, 7.69; N, 15.45.
IR (CCl4): 3601 cm–1 (NH).
2-Bromo-7-[imino(phenyl)methyl]-N1,N1,N8,N8-tetramethyl-
naphthalene-1,8-diamine (3j)
IR (thin film): 3051, 2956, 2930, 2869, 2860, 2828, 2779 (CH),
1685 (C=N), 1621, 1603, 1557, 1504 cm–1 (CH).
To a solution of dibromonaphthalene 5 (1000 mg, 2.6 mmol) in an-
hyd Et2O (50 mL), 1.6 M BuLi in hexanes (1.6 mL, 2.6 mmol) was
added via syringe under an argon atmosphere at –20 °C. After stir-
ring for 10 min, anhyd PhCN (0.3 mL, 2.6 mmol) was added via sy-
ringe under an argon atmosphere. The red-colored mixture was kept
at –20 °C for 24 h and treated with H2O (10 mL). The yellow ether
solution was separated and the aqueous phase was extracted with
CHCl3 (3 × 10 mL). The organic fractions were combined, evapo-
rated and chromatographed (alumina). Yellow crystals; yield: 421
mg (41%); mp 132–134 °С (n-octane); Rf = 0.4 (alumina, Et2O–
n-hexane, 2:1).
1H NMR (CDCl3): δ = 0.89 (t, J = 7.2 Hz, 3 H), 1.45–1.27 (m, 2 H),
1.64–1.46 (m, 2 H), 2.62–2.51 (m, 2 H), 2.73 (s, 6 H), 2.90 (s, 6 H),
6.98 (dd, J = 7.1, 1.6 Hz, 1 H), 7.09 (d, J = 8.3 Hz, 1 H), 7.42–7.25
(m, 3 H), 9.10 (s, 1 H).
1H NMR (DMSO-d6): δ = 0.87 (t, J = 7.2 Hz, 3 H), 1.57–1.24 (m, 4
H), 2.59–2.45 (m, 2 H), 2.73 (s, 6 H), 7.04 (dd, J = 7.3, 1.3 Hz, 1 H),
7.11 (d, J = 8.3 Hz, 1 H), 7.50–7.28 (m, 3 H), 9.66 (br s, 1 H), 2.87
(s, 6 H).
13C NMR (CDCl3): δ = 14.4, 23.1, 29.0, 40.6, 44.8, 45.5, 114.5,
122.6, 123.5, 123.6, 126.4, 126.5, 135.0, 138.5, 146.2, 152.4, 186.2.
IR (CCl4): 3265 (NH), 3060, 3030, 2982, 2900, 2863, 2841, 2810,
2788 cm–1 (CH).
MS (EI): m/z (%) = 29 (21), 41 (20), 225 (28), 240 (100), 241 (20),
297 [M]+ (24).
1H NMR (CDCl3): δ = 2.63 (s, 6 H), 2.97 (s, 6 H), 7.15 (d, J = 8.2
Hz, 1 H), 7.42–7.30 (m, 4 H), 7.45 (d, J = 8.3 Hz, 1 H), 7.53 (d,
J = 8.7 Hz, 1 H), 7.62 (d, J = 7.2 Hz, 1 H), 9.30 (s, 1 H).
1H NMR (DMSO-d6): δ = 2.61 (s, 6 H), 2.96 (s, 6 H), 7.17 (d,
J = 8.0 Hz, 1 H), 7.53–7.40 (m, 3 H), 7.69–7.53 (m, 5 H), 10.30 (s,
1 H).
13C NMR (CDCl3): δ = 44.6, 45.7, 122.5, 124.4, 126.5, 127.6,
128.5, 128.6, 130.3, 131.1, 132.7, 136.6, 137.6, 139.8, 147.9, 148.2,
180.1.
UV/vis (MeCN): λmax (log ε) = 343 (3.81), 249 nm (4.34).
Anal. Calcd for C19H27N3: C, 76.75; H, 9.15; N, 14.13. Found: C,
76.84; H, 9.01; N, 14.15.
2-(1-Iminoethyl)-N1,N1,N8,N8-tetramethylnaphthalene-1,8-di-
amine (3h)
Prepared according to GP2 from 1.6 M MeLi in Et2O (2.6 mL, 4.2
mmol). Orange oil; yield: 557 mg (52%); Rf = 0.8 (alumina, Et2O–
n-hexane, 1:2).
IR (CCl4): 3250 (NH), 3056, 2976, 2860, 2828, 2784 cm–1 (CH).
MS (EI): m/z (%) = 42 (24), 58 (31), 77 (46), 104 (51), 126 (23), 127
(30), 136 (21), 152 (20), 167 (25), 168 (33), 246 (21), 248 (22), 254
(25), 255 (27), 257 (21), 320 (20), 335 (24), 336 (20), 337 (27), 349
(23), 350 (55), 351 (100), 352 (63), 353 (78), 364 (34), 365 (22),
366 (34), 379 (24), 380 (30), 381 (27), 382 (26), 395 [M]+ (66), 396
(22), 397 (63), 398 (20).
1H NMR (CDCl3): δ = 2.37 (s, 3 H), 2.77 (s, 6 H), 2.93 (s, 6 H), 7.02
(dd, J = 7.0, 1.7 Hz, 1 H), 7.15 (d, J = 8.3 Hz, 1 H), 7.39–7.27 (m,
2 H), 7.41 (d, J = 8.3 Hz, 1 H).
1H NMR (DMSO-d6): δ = 2.23 (s, 3 H), 2.71 (s, 6 H), 2.84 (s, 6 H),
7.01 (d, J = 7.2 Hz, 1 H), 7.13 (d, J = 8.3 Hz, 1 H), 7.29 (t, J = 7.6
© Georg Thieme Verlag Stuttgart · New York
Synthesis 2014, 46, 3273–3282

3280
A. S. Antonov et al.
PAPER
UV/vis (MeCN): λmax (log ε) = 337 (3.75), 254 nm (4.49).
[1,8-Bis(dimethylamino)naphthalen-2-yl](phenyl)methanone
(13a)
Anal. Calcd for C21H22BrN3: C, 63.64; H, 5.60; N, 10.60 Found: C,
63.71; H, 5.52; N, 10.69.
Prepared according to GP4 from 3a2 (100 mg, 0.32 mmol). Reaction
time: 1 h. Yellow crystals; yield: 99 mg (99%). Characterization
data were consistent with those reported in the literature.3
2,7-Bis[imino(phenyl)methyl]-N1,N1,N8,N8-tetramethylnaph-
thalene-1,8-diamine (7a)
Prepared according to GP3 from two portions of PhCN (0.3 mL, 2.6
mmol). Yellow crystals; yield: 437 mg (40%); mp 158–159 °С (n-
heptane); Rf = 0.1 (alumina, Et2O–n-hexane, 1:1).
[1,8-Bis(dimethylamino)naphthalen-2-yl](4-methoxyphe-
nyl)methanone (13b)
Prepared according to GP4 from 3b2 (100 mg, 0.29 mmol). Reac-
tion time: 32 h. Yellow crystals; yield: 78 mg (78%); mp 165–166
°C (n-octane); Rf = 0.6 (alumina, Et2O–n-hexane, 2:1).
Alternatively prepared by reaction of a solution of 2,7-dicy-
anonaphthalene 10 (1000 mg, 3.79 mmol) in anhyd Et2O (100 mL)
with a solution of PhLi [obtained from a solution of dry PhBr (23.6
mL, 22.3 mmol) in anhyd Et2O (10 mL) and 1.6 M BuLi (13.9 mL,
22.3 mmol) at –20 °С under an argon atmosphere] at r.t. Reaction
time: 24 h. Yield: 530 mg (46%).
IR (Nujol): 1639 cm–1 (C=O).
1H NMR (CDCl3): δ = 2.69 (s, 6 H), 2.75 (s, 6 H), 3.83 (s, 3 H), 6.87
(d, J = 9.0 Hz, 2 H), 6.99 (dd, J = 6.4, 2.3 Hz, 1 H), 7.22 (d, J = 9.5
Hz, 1 H), 7.44–7.29 (m, 3 H), 7.68 (d, J = 8.9 Hz, 2 H).
13C NMR (CDCl3): δ = 30.1, 45.1, 45.2, 55.9, 77.0, 77.5, 78.0,
113.8, 114.2, 122.2, 122.6, 126.5, 127.1, 130.9, 132.0, 132.7, 139.5,
149.2, 152.6, 163.7, 167.1, 199.4.
IR (CCl4): 3264 (NH), 3060, 3030, 2986, 2903, 2863, 2794 cm–1
(CH).
1H NMR (CDCl3): δ = 2.65 (s, 12 H), 7.18 (d, J = 8.3 Hz, 2 H),
7.42–7.30 (m, 6 H), 7.46 (d, J = 8.3 Hz, 2 H), 7.65 (d, J = 7.0 Hz, 4
H), 8.69 (s, 2 H).
MS (EI): m/z (%) = 121 (100), 127 (20), 135 (83), 167 (25), 168
(43), 225 (26), 304 (26), 316 (31), 331 (52), 348 [M]+ (96), 349 (22).
1H NMR (DMSO-d6): δ = 2.55 (s, 12 H), 7.13 (d, J = 8.2 Hz, 2 H),
7.47–7.38 (m, 6 H), 7.53 (d, J = 6.8 Hz, 4 H), 7.58 (d, J = 8.3 Hz, 2
H), 10.39 (s, 2 H).
13C NMR (CDCl3): δ = 45.4, 123.5, 125.4, 128.4, 128.6, 128.7,
131.2, 134.2, 139.3, 139.7, 148.7, 180.4.
UV/vis (MeCN): λmax (log ε) = 294 (4.27), 226 (5.33), 224 (5.34),
222 nm (5.35).
Anal. Calcd for C22H24N2O2: C, 75.83; H, 6.94; N, 8.04. Found: C,
75.92; H, 6.88; N, 8.09.
[1,8-Bis(dimethylamino)naphthalen-2-yl](naphthalen-1-
yl)methanone (13c)
Prepared according to GP4 from 3c (100 mg, 0.27 mmol). Reaction
time: 3 h. Yellow crystals; yield: 72 mg (72%); mp 120–121 °С
(n-hexane); Rf = 0.8 (alumina, Et2O–n-hexane, 1:1).
MS (EI): m/z (%) = 30 (57), 32 (100), 42 (24), 44 (37), 51 (20), 77
(97), 91 (41), 104 (100), 404 (54), 405 (27), 420 [M]+ (51).
UV/vis (MeCN): λmax (log ε) = 358 (4.08), 258 (4.82), 254 (4.82),
249 (4.81), 243 (4.78), 235 (4.78), 232 (4.79), 229 (4.79), 227 nm
(4.79).
IR (Nujol): 1644 cm–1 (С=О).
Anal. Calcd for C28H28N4: C, 79.97; H, 6.71; N, 13.32. Found: C,
80.09; H, 6.62; N, 13.29.
1H NMR (CDCl3): δ = 2.74 (s, 6 H), 2.81 (s, 6 H), 7.05 (dd, J = 6.1,
2.3 Hz, 1 H), 7.51–7.31 (m, 6 H), 7.73–7.54 (m, 2 H), 8.03–7.91 (m,
2 H), 9.02 (d, J = 8.5 Hz, 1 H).
13C NMR (CDCl3): δ = 44.8, 45.0, 114.0, 121.9, 122.1, 122.5,
124.1, 126.3, 126.4, 127.3, 127.4, 128.1, 128.6, 131.4, 131.6, 133.0,
134.2, 136.3, 139.7, 150.1, 152.6, 201.0.
2,7-Bis[imino(4-methoxyphenyl)methyl]-N1,N1,N8,N8-tetra-
methylnaphthalene-1,8-diamine (7b)
Prepared according to GP3 from two portions of 4-methoxybenzo-
nitrile (358 mg, 2.7 mmol). Yellow crystals; yield: 600 mg (48%);
mp 156–157 °С (n-octane); Rf = 0.2 (alumina, Et2O–n-hexane, 1:1).
MS (EI): m/z (%) = 126 (19), 127 (100), 128 (27), 41 (77), 155 (42),
167 (23), 168 (39), 227 (28), 368 [M]+ (46).
IR (CCl4): 3266 (NH), 3076, 3055, 3003, 2957, 2931, 2904, 2872,
2861, 2838, 2794 cm–1 (CH).
1H NMR (DMSO-d6): δ = 2.58 (s, 12 H), 3.77 (s, 6 H), 6.95 (d,
J = 8.6 Hz, 4 H), 7.08 (d, J = 8.2 Hz, 2 H), 7.60–7.45 (m, 6 H), 9.86
(s, 2 H).
13C NMR (DMSO-d6): δ = 45.3, 56.1, 114.3, 123.6, 125.0, 128.4,
130.4, 132.7, 134.6, 138.8, 148.0, 161.9, 177.5.
UV/vis (MeCN): λmax (log ε) = 222 (5.33), 228 (5.21) sh, 248 (4.63)
sh, 252 (4.57) sh, 334 nm (4.06) sh.
Anal. Calcd for C25H24N2O: C, 81.49; H, 6.57; N, 7.60. Found: C,
81.57; H, 6.51; N, 7.65.
[1,8-Bis(dimethylamino)naphthalen-2-yl](pyridin-3-yl)meth-
anone (13d)
Prepared according to GP4 from 3d (100 mg, 0.31 mmol). Reaction
time: 1 h. Yellow crystals; yield: 65 mg (65%); mp 114–115 °С
(n-hexane); Rf = 0.5 (alumina, Et2O–n-hexane, 1:1).
MS (EI): m/z (%) = 121 (73), 134 (35), 464 (73), 464 (32), 465 (51),
480 [M]+ (100).
UV/vis (MeCN): λmax (log ε) = 420 (2.87) sh, 356 (3.68), 263 (4.46),
225 (4.89), 222 nm (4.90).
IR (Nujol): 1650 cm–1 (C=O).
Anal. Calcd for C30H32N4O2: C, 74.97; H, 6.71; N, 11.66. Found: C,
74.81; H, 6.73; N, 11.62.
1H NMR (CDCl3): δ = 2.62 (s, 6 H), 2.69 (s, 6 H), 6.99 (dd, J = 6.0,
2.6 Hz, 1 H), 7.46–7.24 (m, 5 H), 7.97–7.85 (m, 1 H), 8.67 (dd,
J = 4.8, 1.6 Hz, 1 H), 8.77 (d, J = 1.5 Hz, 1 H).
13C NMR (CDCl3): δ = 45.1, 45.2, 114.7, 122.5, 122.7, 123.2,
123.5, 126.4, 127.8, 129.9, 134.7, 136.9, 140.0, 150.0, 151.5, 152.8,
153.3, 198.8.
2-[Imino(4-methoxyphenyl)methyl]-N1,N1,N8,N8-tetramethyl-
naphthalene-1,8-diamine Perchlorate (3b·HClO4)
An aq HClO4 soln (d = 1.508) (0.020 mL, 0.18 mmol) was added to
a solution of imine 3b (60 mg, 0.18 mmol) in EtOAc (1 mL). The
precipitate thus formed was separated by centrifugation and puri-
fied by crystallization (EtOH). Pale pink crystals; yield: 54 mg
(81%); mp>193 °С dec. (EtOH).
1H NMR (DMSO-d6): δ = 2.56 (s, 6 H), 2.71 (s, 6 H), 2.99 (s, 3 H),
3.27 (d, J = 2.3 Hz, 3 H), 3.81 (s, 1.5 H), 3.87 (s, 3 H), 7.01 (d,
J = 8.8 Hz, 3 H), 7.33 (d, J = 8.4 Hz, 0.5 H), 7.40 (d, J = 8.5 Hz, 1
H), 7.57–7.48 (m, 4 H), 7.71–7.60 (m, 2 H), 7.83 (t, J = 7.9 Hz, 0.5
H), 8.26–8.10 (m, 1.5 H), 11.93 (s, 2.5 H), 18.57 (s, 0.5 H).
MS (EI): m/z (%) = 32 (59), 44 (25), 78 (26), 168 (27), 287 (25), 288
(27), 302 (21), 319 [M]+ (100), 320 (21).
UV/vis (MeCN): λmax (log ε) = 227 (5.33), 224 (5.35), 222 nm
(5.35).
Anal. Calcd for C20H21N3O: C, 75.21; H, 6.63; N, 13.16. Found: C,
75.30; H, 6.57; N, 13.14.
Synthesis 2014, 46, 3273–3282
© Georg Thieme Verlag Stuttgart · New York

PAPER
ortho-Ketimines of 1,8-Bis(dimethylamino)naphthalene
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[1,8-Bis(dimethylamino)naphthalen-2-yl](thiophen-2-yl)meth-
anone (13e)
Prepared according to GP4 from 3e (100 mg, 0.31 mmol). Reaction
time: 12 h. Orange crystals; yield: 56 mg (56%); mp 130–131 °С
(n-hexane); Rf = 0.9 (alumina, Et2O–n-hexane, 1:1).
IR (Nujol): 1630 cm–1 (C=O).
1H NMR (250 MHz, CDCl3): δ = 2.84 (s, 6 H), 2.85 (s, 6 H), 7.15–
1-[1,8-Bis(dimethylamino)naphthalen-2-yl]ethanone (13h)
Prepared according to GP4 from 3h (100 mg, 0.39 mmol). Reaction
time: 1 h. Orange oil; yield: 77 mg (77%). Characterization data
were consistent with those reported in the literature.3
[7-Bromo-1,8-bis(dimethylamino)naphthalen-2-yl](phe-
nyl)methanone (13j)
Prepared according to GP4 from 3j (100 mg, 0.27 mmol). Reaction
time: 1 h. Yellow crystals; yield: 85 mg (85%); mp 92–93 °С
(n-hexane); Rf = 0.4 (alumina, Et2O–n-hexane, 1:1).
7.03 (m, 2 H), 7.49–7.29 (m, 5 H), 7.71 (dd, J = 4.9, 0.9 Hz, 1 H).
13C NMR (CDCl3): δ = 44.6, 44.9, 113.9, 121.8, 122.0, 122.3,
125.8, 127.0, 127.7, 129.9, 133.9, 134.6, 139.3, 145.9, 149.0, 152.3,
192.1.
IR (KBr): 3060, 2977, 2918, 2897, 2882, 2861, 2838, 2790, 2783
(CH), 1666 cm–1 (С=O).
1H NMR (CDCl3): δ = 2.70 (s, 6 H), 3.00 (s, 6 H), 7.20 (d, J = 8.3
Hz, 1 H), 7.36 (d, J = 8.7 Hz, 1 H), 7.47–7.38 (m, 3 H), 7.58–7.49
(m, 2 H), 7.78 (dd, J = 8.3, 1.2 Hz, 2 H).
MS (EI): m/z (%) = 39 (31), 42 (23), 44 (21), 97 (55), 111 (78), 127
(30), 167 (28), 168 (45), 182 (22), 225 (29), 292 (27), 307 (35), 324
[M]+ (100), 325 (21).
13C NMR (CDCl3): δ = 44.6, 46.1, 122.3, 123.9, 126.3, 126.4,
128.8, 129.7, 130.3, 133.1, 133.4, 134.7, 138.3, 138.6, 148.4, 149.7,
199.7.
UV/vis (MeCN): λmax (log ε) = 260 (4.35), 282 (4.27), 350 (3.72) sh,
412 nm (3.39).
Anal. Calcd for C19H20N2OS: C, 70.34; H, 6.21; N, 8.63. Found: C,
70.42; H, 6.16; N, 8.69.
MS (EI): m/z (%) = 44 (34), 58 (36), 77 (68), 81 (35), 91 (36), 100
(26), 105 (100), 168 (27), 352 (29), 396 [M]+ (37), 398 (36).
1-[1,8-Bis(dimethylamino)naphthalen-2-yl]-2,2-dimethylpro-
pan-1-one (13f)
Prepared according to GP4 from 3f (100 mg, 0.34 mmol). Reaction
time: 8 h. Beige crystals; yield: 10 mg (10%); mp 130–131 °С
(n-hexane); Rf = 0.5 (alumina, Et2O–n-hexane, 1:1).
UV/vis (MeCN): λmax (log ε) = 236 (4.75), 234 (4.80), 232 (4.81),
230 (4.82), 227 (4.84), 223 (4.82), 221 nm (4.81).
Anal. Calcd for C21H21BrN2O: C, 63.48; H, 5.33; N, 7.05. Found: C,
63.95; H, 5.41; N, 6.79.
IR (Nujol): 1679 cm–1 (C=O).
[1,8-Bis(dimethylamino)naphthalene-2,7-diyl]bis(phenylmeth-
anone) (14a)
Prepared according to GP4 from 7a (100 mg, 0.24 mmol). Reaction
time: 1 h. Yellow crystals; yield: 80 mg (80%). Characterization
data were consistent with those reported in the literature.3
1H NMR (CDCl3): δ = 1.23 (s, 9 H), 2.72 (s, 6 H), 2.86 (s, 6 H), 7.04
(d, J = 8.3 Hz, 1 H), 7.06 (dd, J = 7.3, 1.2 Hz, 1 H), 7.30 (t, J = 7.7
Hz, 1 H), 7.42–7.36 (m, 2 H).
13C NMR (CDCl3): δ = 28.3, 44.7, 44.8, 45.5, 114.7, 122.7, 122.8,
123.1, 124.2, 126.1, 135.5, 138.0, 146.0, 152.2, 216.6.
[1,8-Bis(dimethylamino)naphthalene-2,7-diyl]bis[(4-methoxy-
phenyl)methanone] (14b)
Prepared according to GP4 from 7b (100 mg (0.21 mmol). Reaction
time: 26 h. Yellow crystals; yield: 55 mg (55%); yellow crystals;
mp 165–166 °С (n-octane); Rf = 0.6 (alumina, CHCl3).
MS (EI): m/z (%) = 29 (32), 41 (44), 57 (45), 127 (21), 167 (20), 168
(54), 182 (24), 210 (36), 225 (20), 226 (34), 241 (100), 298 [M]+
(57).
UV/vis (MeCN): λmax (log ε) = 244 (4.49) sh, 344 nm (3.85).
IR (KBr): 2999, 2974, 2955, 2911, 2907, 2838, 2790 (CH), 1651
cm–1 (C=O).
1H NMR (CDCl3): δ = 2.71 (s, 12 H), 3.85 (s, 6 H), 6.94–6.87 (m, 4
H), 7.22 (d, J = 8.4 Hz, 2 H), 7.41 (d, J = 8.3 Hz, 2 H), 7.79–7.71
(m, 4 H).
13C NMR (CDCl3): δ = 45.6, 55.9, 114.0, 122.6, 124.1, 127.6,
131.7, 131.9, 132.8, 140.5, 150.5, 163.9, 198.8.
Anal. Calcd for C19H26N2O: C, 76.47; H, 8.78; N, 9.39. Found: C,
76.52; H, 8.75; N, 9.33.
1-[1,8-Bis(dimethylamino)naphthalen-2-yl]pentan-1-one (13g)
Prepared according to GP4 from 3g (100 mg, 0.27 mmol). Reaction
time: 1 h. Yellow crystals; yield: 78 mg (78%); mp 29–30 °С
(n-hexane); Rf = 0.9 (alumina, Et2O–n-hexane, 1:1).
IR (Nujol): 1687 cm–1 (C=O).
MS (EI): m/z (%) = 77 (22), 92 (13), 107 (11), 121 (100), 122 (10),
135 (83), 437 (16), 438 (20), 465 (35), 466 (13), 482 (82) [M]+, 483
(30).
1H NMR (CDCl3): δ = 0.91 (t, J = 7.3 Hz, 3 H), 1.45–1.28 (m, 2 H),
1.74–1.57 (m, 2 H), 2.75 (s, 6 H), 2.76 (t, J = 7.5 Hz, 2 H), 2.92 (s,
6 H), 6.99 (dd, J = 6.0, 2.8 Hz, 1 H), 7.20 (d, J = 8.4 Hz, 1 H), 7.41–
7.26 (m, 3 H).
13C NMR (CDCl3): δ = 14.4, 23.1, 27.5, 43.3, 45.2, 45.3, 114.5,
122.4, 123.0, 123.2, 125.1, 127.2, 133.3, 139.5, 148.5, 152.7, 166.7,
209.1.
UV/vis (MeCN): λmax (log ε) = 371 (4.00), 284 (4.75), 229 (5.14),
224 nm (5.19).
Anal. Calcd for C30H30N2O4: C, 74.67; H, 6.27; N, 5.81. Found: C,
75.01; H, 6.33; N, 5.77.
MS (EI): m/z (%) = 29 (100), 32 (29), 39 (25), 41 (76), 42 (67), 43
(51), 44 (44), 57 (34), 58 (42), 115 (20), 127 (41), 154 (31), 167
(37), 168 (70), 169 (21), 182 (38), 196 (20), 197 (20), 198 (20), 210
(60), 211 (22), 226 (22), 241 (92), 254 (34), 267 (21), 283 (38), 298
[M]+ (99), 299 (23).
Acknowledgment
Financial support from the Russian Foundation for Basic Research
(projects RFBR 12-03-31172 and 14-03-00010) is gratefully ac-
knowledged. We also thank Dr. K. Y. Suponitsky (A. N. Nesmeya-
nov Institute of Organoelement Compounds of Russian Academy of
Sciences, Moscow) for X-ray crystal structure analysis.
UV/vis (MeCN): λmax (log ε) = 288 (3.74), 230 (4.72), 227 (4.75),
223 (4.75), 221 nm (4.71).
Anal. Calcd for C19H26N2O: C, 76.47; H, 8.78; N, 9.39. Found: C,
76.52; H, 8.82; N, 9.31.
Supporting Information for this article is available online
at
http://www.thieme-connect.com/products/ejournals/journal/
10.1055/s-00000084.SunogIpimrfiantoSuIpg
n
fonirtat
ori
© Georg Thieme Verlag Stuttgart · New York
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PAPER
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Synthesis 2014, 46, 3273–3282
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