Synthesis and reactions of 2-(dimethylaminomethylidene)-6-methoxynaphto[1, 8-bc]pyran-3-one

Article abstract of DOI:10.1134/S1070428008040222

The reaction of 6-methoxynaphthol[1,8-bc]pyran-3-one with dimethylformamide dimethyl acetal gave the corresponding 2-dimethylaminomethylidene derivative which reacted with amines to form new 2-aminomethylidene-6-methoxynaphtho[1,8- bc]pyran-3-ones via rep

Full text of DOI:10.1134/S1070428008040222

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2008, Vol. 44, No. 4, pp. 602–606. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © O.M. Golyanskaya, N.A. Voloshin, A.V. Chernyshev, A.D. Dubonosov, A.V. Metelitsa, V.V. Mezheritskii, V.A. Bren’, 2008,
published in Zhurnal Organicheskoi Khimii, 2008, Vol. 44, No. 4, pp. 608–611.
Synthesis and Reactions of 2-(Dimethylaminomethylidene)-
6-methoxynaphtho[1,8-bc]pyran-3-one
O. M. Golyanskayaa, N. A. Voloshinb, A. V. Chernysheva, A. D. Dubonosovb, A. V. Metelitsaa,
V. V. Mezheritskiia, and V. A. Bren’a
a Institute of Physical and Organic Chemistry, Southern Federal University,
pr. Stachki 194/2, Rostov-on-Don, 344090 Russia
e-mail: mezher@ipoc.rsu.ru
b Southern Research Center, Russian Academy of Sciences, ul. Chekhova 41, Rostov-on-Don, 344006 Russia
Received July 2, 2007
Abstract—The reaction of 6-methoxynaphtho[1,8-bc]pyran-3-one with dimethylformamide dimethyl acetal
gave the corresponding 2-dimethylaminomethylidene derivative which reacted with amines to form new
2-aminomethylidene-6-methoxynaphtho[1,8-bc]pyran-3-ones via replacement of the dimethylamino group.
2-Dimethylaminomethylidene-6-methoxynaphtho[1,8-bc]pyran-3-one also reacted with 2,3-dimethylchromeni-
um perchlorate and 1,2,3,3-tetramethyl-3H-indolium perchlorate to give the corresponding merocyanine dyes.
The latter were examined for chemosensor and photochromic properties.
DOI: 10.1134/S1070428008040222
We previously [1] reported on the synthesis of
2-acyl-substituted 6-methoxynaphtho[1,8-bc]pyran-3-
ones. These compounds, as well as metal chelates
derived therefrom, were found to exhibit strong yel-
low–orange fluorescence which can be observed visu-
ally. Their fluorescent properties were studied in [2].
We anticipated that 2-formyl derivative of the above
peri-fused heterocyclic system may be a potential pre-
cursor of new chemosensors [3] and photochromic
compounds [4]. However, our attempts to effect
Scheme 1.
R
N
R
N
H
O
H
CHNMe2
O
H
O
H
O
O
O
O
O
Me2NCH(OMe)2
RNH2
+
OMe
OMe
OMe
OMe
I
II
A
IVa–IVc
B
CHO
OH
O
H+/H2O
II
OMe
III
R = PhCH2 (a), p-MeC6H4 (b), p-MeOC6H4CONH (c).
602

SYNTHESIS AND REACTIONS OF 2-(DIMETHYLAMINOMETHYLIDENE)-...
603
Scheme 2.
CHNMe2
O
Me
OH
O
O
Me
O
+
ClO4
ClO4
OMe
O
Me
OMe
II
V
C
1
Me
O
4
3
5
O
Me2NH
–ClO4
2
O
OMe
6
8
7
VII
CHNMe2
O
Me
Me
OH
O
Me
N
Me
Me
N
Me
O
+
ClO4
ClO4
OMe
Me
VI
OMe
II
D
Me
Me
O
3
4
1
5
N
2
Me2NH
–ClO4
Me
O
OMe
6
8
7
VIII
sively the quinoid rather than benzoid structure, as
follows from their IR, 1H NMR, and UV spectra. In the
IR spectra of both compound II and amino ketones
IVa–IVc we observed a strong absorption band at
1660–1680 cm–1, which is typical of a carbonyl rather
formylation of previously synthesized 6-methoxy-
naphtho[1,8-bc]pyran-3-one (I) [5] according to
Rieche [6] or Vilsmeier [7] were unsuccessful, whereas
heating of compound I with dimethylformamide
dimethyl acetal gave 2-dimethylaminomethylidene
derivative II (Scheme 1). Unfortunately, hydrolysis of
II resulted in the formation of a tarry material instead
of expected aldehyde III, and we failed to isolate
individual compounds.
1
than C=N group [8]. The H NMR spectra of enamino
ketones IVa–IVc contained a double set of signals
from protons in the NH, Me, and OMe groups with
an intensity ratio of (0.3–0.4):(0.7–0.6). Presumably,
these compounds exist as two isomers A and B. The
NH proton in isomer A resonates in the 1H NMR spec-
trum at δ 10–11 ppm, while the corresponding signal
of isomer B is located at δ 5.4 ppm in the spectrum of
compound IVa; the NH signal of IVb and IVc is
overlapped by the aromatic proton signals, and it can
be identified only by deuteration.
We found that enamino ketones IV as potential
ligands and chemosensors can be obtained by reaction
of compound II with aliphatic and aromatic amines or
carboxylic acid hydrazides (Scheme 1). Unlike struc-
turally related 2-acyl-3-hydroxy-6-methoxynaphtho-
[1,8-bc]pyrans [1], enamino ketones IV have exclu-
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 4 2008

GOLYANSKAYA et al.
10
604
the conditions for determination of their chemosensor
properties (room temperature, propan-2-ol or acetoni-
trile as solvent, c = 2.5×10–5 M) hampers chelation
with heavy metal cations. Only insignificant changes
were observed in the electronic absorption spectra, and
the emission maximum did not change its position,
regardless of the cation nature (Pb2+, Hg2+, Cu2+, Cd2+).
Thus compounds IV cannot be used as chemosensors.
0.6
8
6
4
0.4
0.2
0.2
Compound II can be used as a synthetic equivalent
of aldehyde III in the condensation with heterocyclic
cations V and VI at the activated 2-methyl group with
a view to obtain 2-styryl derivatives C and D and
convert the latter into novel potentially photochromic
spirochromenes (Scheme 2). By heating 2-dimethyl-
aminomethylidene-6-methoxynaphtho[1,8-bc]pyran-3-
one (II) with 2,3-dimethylchromenium perchlorate (V)
and 1,2,3,3-tetramethyl-3H-indolium perchlorate (VI)
in acetic acid we obtained deeply colored compounds
VII and VIII, respectively. In this condensation,
dimethylamine liberated during the process acted as
deprotonating agent. The deep color of compounds VII
and VIII in solution and in the crystalline state indi-
cates that they have open-chain merocyanine structure.
2
0
300
400
500
λ, nm
600
700
Fig. 1. (1) Electronic absorption, (2) emission, and (3) fluo-
rescence excitation spectra of 6-methoxy-2-[(2Z)-2-(1,3,3-tri-
methyl-2,3-dihydro-1H-indol-2-ylidene)ethylidene]naphtho-
[1,8-bc]pyran-3(2H)-one (VIII) in toluene (c = 1.3×10–4 M).
0.5
0.4
0.3
0.2
0.1
The electronic absorption spectra of VII and VIII
in toluene contained long-wave maxima at λ 517 and
529 nm, respectively (Fig. 1). The position and intens-
ity of these bands are typical of acyclic merocyanine
forms F of spiropyrans E [4] (Scheme 3). 3H-Indole
derivative VIII showed strong fluorescence with
a quantum yield of 0.11, the emission maximum being
located at λ 571 nm. The fluorescence excitation spec-
trum of VIII coincides with its absorption spectrum
(Fig. 1). Compound VII possesses no fluorescent
properties.
Irradiation of a solution of VIII at 293 K at a wave-
length corresponding to its long-wave absorption max-
imum (λ 546 nm) promotes irreversible photoinduced
transformation which is accompanied by reduction in
the fluorescence intensity at 529 nm (Fig. 2). Com-
pound VII is photochemically inactive: no changes in
the electronic absorption spectrum was observed upon
irradiation of a solution of VII in toluene at 293 K
with a mercury lamp (λ 546 nm, intensity 1.5×
1016 quantum/s) over a period of 20 min.
300
400
500
600
λ, nm
Fig. 2. Variation of the electronic absorption spectrum of
6-methoxy-2-[(2Z)-2-(1,3,3-trimethyl-2,3-dihydro-1H-indol-
2-ylidene)ethylidene]naphtho[1,8-bc]pyran-3(2H)-one
(VIII) in toluene (c = 1.1×10–4 M) at 293 K upon irradiation
at λ 546 nm; the spectra were recorded at 20-s intervals.
The quinoid structure of compounds IVa–IVc is
also confirmed by the presence in their electronic ab-
sorption spectra of a long-wave absorption band in the
region λ 430–470 nm, regardless of the solvent polar-
ity. As noted above, 2-acyl-3-hydroxy-6-methoxy-
naphtho[1,8-bc]pyrans are characterized by strong
fluorescence in the region of about λ 570 nm with
a considerable Stokes shift due to O→N hydrogen
transfer in the excited state [9]. Enamino ketones IV
displayed much weaker fluorescence at λ 480 nm, and
the absorption and emission bands are mirror sym-
metric. The quinoid structure of compounds IV under
Scheme 3.
Ht
Ht
O
O
E
F
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 4 2008

SYNTHESIS AND REACTIONS OF 2-(DIMETHYLAMINOMETHYLIDENE)-...
605
Thus we have synthesized new compounds VII and
VIII which have the structure of open-chain mero-
cyanine forms of spiropyrans. These compounds
exhibit no photochromic properties (reverse photo-
chromism) at 293 K.
6-Methoxy-2-(4-methylphenylaminomethyli-
dene)naphtho[1,8-bc]pyran-3-one (IVb) was syn-
thesized in a similar way. Yield 62%, red crystals,
mp 128–129°C (from ethanol). IR spectrum, ν, cm–1:
3200, 1670, 1590. 1H NMR spectrum, δ, ppm: 2.34 s
(3H, CH3), 4.18 s (0.3CH3, OCH3), 4.20 s (0.7CH3,
OCH3), 6.90–7.50 m (7H, Harom, =CHN), 7.66 d (0.7H,
EXPERIMENTAL
3
NH, J = 12 Hz), 7.70–8.26 m (3H, Harom), 11.38 d
The IR spectra were recorded in mineral oil on
3
(0.3H, NH, J = 12 Hz). Found, %: C 76.43; H 4.95;
1
a Specord IR-71 spectrophotometer. The H NMR
N 4.39. C21H17NO3. Calculated, %: C 76.13; H 5.14;
N 4.23.
spectra were measured on a Varian Unity-300 instru-
ment (USA) from solutions in CDCl3 using hexa-
methyldisiloxane as internal reference. The electronic
absorption spectra were obtained on a Varian Cary 100
spectrophotometer. The emission and fluorescence
excitation spectra were measured on a Varian Cary
Eclipse spectrofluorimeter. The fluorescence quantum
yields were determined relative to a solution of Eosin
in 0.1 M NaOH (φ = 0.20 [10]). Solutions were
prepared using toluene of ultrapure grade. A DRSh-250
mercury lamp was used as irradiation source; required
spectral bands were isolated with the aid of inter-
ference filters.
6-Methoxy-2-[2-(4-methoxybenzoyl)hydrazino-
methylidene]naphtho[1,8-bc]pyran-3-one (IVc).
A mixture of 0.1 g (0.4 mmol) of compound II and
0.07 g (0.45 mmol) of p-methoxybenzohydrazide in
1 ml of toluene was heated for 2 h under reflux. After
cooling, the precipitate was filtered off. Yield 0.08 g
(58%), yellow crystals, mp 227–228°C (from aceto-
nitrile). IR spectrum, ν, cm–1: 3486, 3406, 3260, 1670,
1
1660, 1600. H NMR spectrum (DMSO-d6), δ, ppm:
3.80 s (0.4CH3, C6H4OCH3), 3.83 s (0.6CH3, C6H4O-
CH3), 4.05 s (0.6CH3, 6-OCH3), 4.10 s (0.4CH3,
6-OCH3), 6.95–8.20 m (10H, Harom, =CHN), 8.4 s
(0.4H, NHCO), 9.25 d [0.6H, NHNHCO, J(NH,CH) =
10.36 Hz], 10.80 s (0.6H, NHCO), 11.80 d [0.4H,
NHNHCO, J(NH,CH) = 10.36 Hz]. Found, %:
C 67.91; H 4.55; N 7.38. C22H18N2O5. Calculated, %:
C 67.69; H 4.62; N 7.18.
2-Dimethylaminomethylidene-6-methoxynaph-
tho[1,8-bc]pyran-3-one (II). N,N-Dimethylformamide
dimethyl acetal, 0.18 ml (1.5 mmol), was added to
a hot solution of 0.21 g (1 mmol) of compound I in
3 ml of toluene, and the mixture was heated for 3 h
under reflux. The orange precipitate was filtered off
and recrystallized from alcohol. Yield 0.17 g (71%),
mp 202–203°C. IR spectrum, ν, cm–1: 1670 (C=O),
6-Methoxy-2-[(2Z)-2-(methyl-2H-chromen-2-
ylidene)ethylidene]naphtho[1,8-bc]pyran-3(2H)-one
(VII). A mixture of 0.1 g (0.4 mmol) of compound II
and 0.12 g (0.45 mmol) of 2,3-dimethylchromenium
perchlorate in 3 ml of acetonitrile was heated for 0.5 h
under reflux. After cooling, the precipitate was filtered
off. Yield 0.08 g (54%), green crystals with metallic
luster, mp 249–251°C (from acetonitrile). IR spectrum,
ν, cm–1: 1646, 1566, 1540. 1H NMR spectrum, δ, ppm:
2.20 s (3H, CH3), 4.10 s (3H, OCH3), 6.06 d (1H, 2-H,
J2,3 = 12.15 Hz), 6.60 s (1H, 1-H), 6.98–7.36 m (6H,
Harom), 7.48 t (1H, 7-H, J7,8 = 8.21, J7,6 = 7.91 Hz),
7.65 d (1H, 3-H, J3,2 = 12.15 Hz), 7.86 d (1H, 7-H,
J8,7 = 8.21 Hz), 8.32 d (1H, 4-H, J4,5 = 8.20 Hz).
Found, %: C 78.91; H 4.55. C25H18O4. Calculated, %:
C 78.53; H 4.71.
1
1620, 1580. H NMR spectrum, δ, ppm: 3.30 s (6H,
NMe2), 4.05 s (3H, OCH3), 6.93 d (1H, 5-H, J5,4
=
8.25 Hz), 6.98 d (1H, 7-H, J7,8 = 7.85 Hz), 7.22 s (1H,
=CHN), 7.38 t (1H, 8-H, J8,9 = 8.25, J8,7 = 7.85 Hz),
7.72 d (1H, 9-H, J9,8 = 8.25 Hz), 8.11 d (1H, 4-H,
J4,5 = 8.25 Hz). Found, %: C 71.51; H 5.76; N 5.35.
C16H15NO3. Calculated, %: C 71.36; H 5.61; N 5.20.
2-Benzylaminomethylidene-6-methoxynaphtho-
[1,8-bc]pyran-3-one (IVa). A mixture of 0.1 g
(0.4 mmol) of compound II and 0.06 g (0.6 mmol) of
benzylamine in 2 ml of toluene was heated for 3.5 h
under reflux. After cooling, the precipitate was filtered
off. Yield 0.09 g (70%), yellow crystals, mp 180–
181°C (from toluene). IR spectrum, ν, cm–1: 3260,
1
6-Methoxy-2-[(2Z)-2-(1,3,3-trimethyl-2,3-dihy-
dro-1H-indol-2-ylidene)ethylidene]naphtho[1,8-bc]-
pyran-3(2H)-one (VIII). A solution of 0.1 g
(0.4 mmol) of compound II and 0.14 g (0.5 mmol) of
1,2,3,3-tetramethyl-3H-indolium perchlorate in 2 ml of
acetic acid was heated for 0.5 h under reflux. The
mixture was diluted with water, and the precipitate was
1665, 1580. H NMR spectrum (CDCl3), δ, ppm:
4.06 s (0.3CH3, OCH3), 4.08 s (0.7CH3, OCH3), 4.49 d
3
3
(0.3CH2, J = 4.94 Hz), 4.54 d (0.7CH2, J = 5.97 Hz),
5.38 m (0.7H, NH), 6.90–8.60 m (11H, Harom, =CHN),
9.80 m (0.3H, NH). Found, %: C 76.39; H 5.31;
N 4.08. C21H17NO3. Calculated, %: C 76.13; H 5.14;
N 4.23.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 4 2008

GOLYANSKAYA et al.
606
2. Tsukanov, A.V., Dubonosov, A.D., Golyanskaya, O.M.,
Mezheritskii, V.V., Revinskii, Yu.V., Bren’, V.A., and
Minkin, V.I., Russ. J. Gen. Chem., 2006, vol. 76, p. 841.
3. Bren’, V.A., Usp. Khim., 2001, vol. 70, p. 1017.
4. Guglielmetti, R., Photochromism, Durr, H. and Bouas-
Laurent, H., Eds., Amsterdam: Elsevier, 1990, p. 314.
5. Minyaeva, L.G., Golyanskaya, O.M., and Mezherits-
kii, V.V., Zh. Org. Khim., 1994, vol. 30, p. 258.
6. Rieche, A., Gross, H., and Hoft, E., Chem. Ber., 1960,
filtered off and purified by column chromatography on
aluminum oxide using chloroform as eluent. Yield
0.09 g (62%), dark red crystals, mp 217–219°C. IR
1
spectrum, ν, cm–1: 1646, 1593, 1540. H NMR spec-
trum (CDCl3), δ, ppm: 1.65 s (6H, CMe2), 3.27 s (3H,
NCH3), 4.10 s (3H, OCH3), 5.94 d (1H, 2-H, J2,3
13.11 Hz), 6.74 d (1H, 1-H, J = 7.77 Hz), 6.90–7.30 m
(5H, Harom), 7.46 t (1H, 7-H, J7,8 = 8.17, J7,6
=
=
7.98 Hz), 7.64 d (1H, 3-H, J3,2 = 13.11 Hz), 7.86 d (1H,
8-H, J8,7 = 8.17 Hz), 8.24 d (1H, 4-H, J4,5 = 8.13 Hz).
Found, %: C 78.81; H 5.65; N 3.70. C26H23NO3. Cal-
culated, %: C 78.59; H 5.79; N 3.53.
vol. 93, p. 88.
7. Vilsmeier, A. and Haack, A., Chem. Ber., 1927, vol. 60,
p. 121.
8. Bellamy, L.J., The Infra-red Spectra of Complex
Molecules, London: Methuen, 1958.
This study was performed under financial support
by the Ministry of Education and Science of the
Russian Federation (project nos. RNP.2.2.2.2.5592,
RNP.2.1.1.1938).
9. Knyazhanskii, M.I. and Metelitsa, A.V., Fotoinitsiiro-
vannye protsessy v molekulakh azometinov i ikh struk-
turnykh analogov (Photoinitiated Processes in Mole-
cules of Schiff Bases and Their Structural Analogs),
Rostov-on-Don: Rostov. Gos, Univ., 1992.
REFERENCES
10. Fleming, G.R., Knight, A.W.E., Morris, J.M., Morri-
son, R.J.S., and Robinson, G.W., J. Am. Chem. Soc.,
1977, vol. 99, p. 4306.
1. Mezheritskii, V.V., Minyaeva, L.G., and Golyan-
skaya, O.M., Zh. Org. Khim., 1992, vol. 28, p. 1187.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 4 2008