Synthesis and conformations of cross-conjugated polyenes containing heterocyclic moieties with diverse structures

Article abstract of DOI:10.1016/j.mencom.2014.11.024

New non-linear cross-conjugated polyenes containing a central 4-ylidene-substituted pyran or N-methyldihydropyridine ring have been synthesized. Interaction of chromophores in these compounds occurs through the ylidene group linked to the heterocycles.

Full text of DOI:10.1016/j.mencom.2014.11.024

Mendeleev
Communications
Mendeleev Commun., 2014, 24, 377–379
Synthesis and conformations of cross-conjugated polyenes
containing heterocyclic moieties with diverse structures
Zhanna A. Krasnaya,* Vadim V. Kachala and Sergei G. Zlotin
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russian Federation.
Fax: +7 499 135 5328; e-mail: kra@ioc.ac.ru
DOI: 10.1016/j.mencom.2014.11.024
New non-linear cross-conjugated polyenes containing a central 4-ylidene-substituted pyran or N-methyldihydropyridine ring have
been synthesized. Interaction of chromophores in these compounds occurs through the ylidene group linked to the heterocycles.
NMe2
Previously, we performed the reaction of b-dimethylamino-
Y
Y
acrolein aminal Me2NCH=CHCH(NMe2)2 1 with 2,6-dimethyl-
4-pyrone or N-methyl-2,6-dimethylpyridin-4-one to give keto-
cyanine dyes 2 and 3 (cross-conjugated polyene w,w'-bisamino-
ketones with a central pyran or dihydropyridine moiety) containing
two aminopolyene chromophores with equal lengths linked by a
carbonyl group and a central bridge.1,2
Me2N
NMe2
4
5
6
3
2
1
1
Me
O
Me
O
10a–e
Me2N
NMe2
12a–e (34–87%)
X
Y
Y
4
5
6
3
2
1
O
2, 3: X = O
1
Me
N
Me
Me
Me2N
N
NMe2
4, 5: X = C(CN)2
6, 7: X = C(CN)C6H4NO2-p
Me
O
Me2N
NMe2
11a–d
13a–d (64–80%)
2, 4, 6, 8
8, 9: X =
X
Me
O
O
Ph
N
N
O
N
O
a Y =
b Y =
c Y =
N
N
Me2N
N
NMe2
Ph
Ph
O
Ph
O
Me
3, 5, 7, 9
Me
N
Et
O
O
O
N
N
d Y =
e Y =
O
S
Replacement of the bridging O atom by an NMe group
drastically changes the dye absorption spectrum, since in com-
pound 2 the chromophores are arranged at a sharp angle to each
other, whereas at an obtuse angle in compound 3.3–5
N
O
Me
Et
Scheme 1
The same phenomenon occurred in the case of cross-con-
jugates w,w'-dimethylaminopolyenes 4–9 containing a central
pyran or N-methyldihydropyridine moiety. The aminopolyene
chromophores in these compounds interact through 2,2-dicyano-,
2-cyano-2-(4-nitrophenyl)- or dioxoindan-2-ylidene groups located
at 4-position of the heterocycle.6
Previously, interesting data were reported that new chromo-
phores based on pyranone and functionalised conjugated aldehydes
containing bridging moieties demonstrated nonlinear optical pro-
perties,7 whereas pyran dyes with push-pull structures incorporat-
ing a CN group were found to be promising for solar energy
cells.8 Furthermore, a D-p-A-p-D dye containing a central acceptor
core A similar to the core of polyene 3 and heterocyclic donor
groups D was recently synthesized.9
ylidene derivatives of barbituric acids are promising not only as
biologically active compounds10 but also as potential dyes.11
To perform this task, we studied the reaction of aminal 1 with
substituted 2,6-dimethyl-4H-pyrans 10a–e and 1,2,6-trimethyl-
1,4-dihydropyridines 11a–e containing the corresponding hetero-
cycles at 4-position (Schemes 1 and 2).
Compounds 10a–e were obtained by heating 2,6-dimethyl-4H-
pyran-4-one with heterocyclic compounds containing a reactive
methylene group (the residue of the latter is denoted as Y in
Scheme 1) in acetic anhydride. Substituted 1,2,6-trimethyl-1,4-
dihydropyridines 11a–e were synthesized from the corresponding
pyrans 10a–e by treatment with 40% MeNH2 aqueous solution
or 15% MeNH2 solution in EtOH (see Online Supplementary
Materials).
In view of this, we decided to synthesize new cross-conjugated
polyenes containing a pyran or dihydropyridine ring and a methyl-
idene acceptor linked to carbonyl-containing polynitrogen or
nitrogen-oxygen heterocycles with various structures. Of these,
Dyes 12a–e and 13a–d were prepared by condensation of
pyrans 10a–e or dihydropyridines 11a–d with excess aminal 1
(reactant ratio of 1:3) in the absence of a solvent, except for
© 2014 Mendeleev Communications. All rights reserved.
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Mendeleev Commun., 2014, 24, 377–379
S
S
S
Et
Et
O
Et
Et
Et
Et
O
NMe2
NMe2
N
N
N
N
N
N
Me2N
O
O
O
O
1
+
4
5
3
6
2
1
Me
N
Me
Me2N
N
NMe2
Me
N
NMe2
Me
11e
Me
Me
13e
14
Scheme 2
polyenes 12b,e which were obtained in dry benzene.† Note that,
though the reaction conditions vary, in all cases (except for
dihydropyridine 11e), the reaction of aminal 1 involves both
methyl groups to afford polyenes containing two polyene chromo-
phores. The reaction of dihydropyridine 11e with aminal 1 in
dry benzene without heating gave a mixture of polyene 13e and
tetraene 14 in 2:3 ratio (Scheme 2).‡
Fractional crystallization of this mixture provided pure tetraene
14. Heating of the mixture of compounds 13e and 14 with excess
aminal 1 finally led to polyene 13e.
The structures and conformations of the obtained compounds
1
12a–e, 13a–e and 14 were proved from 1D and 2D H and
4-{2,6-Bis[(1E,3E)-4-dimethylaminobuta-1,3-dienyl]-1-methylpyridin-
4(1H)-ylidene}-3-phenylisoxazol-5(4H)-one 13b. Aminal 1 (0.13 g,
0.76 mmol) was added to substituted dihydropyridine 11b (0.07 g, 0.2 mmol)
and the mixture was stirred for 35 min at 70–75°C. The reaction mixture
containing a cherry-coloured precipitate was concentrated in vacuo, then
Et2O was added. The precipitate was filtered off and washed with a small
amount of EtOH to give 0.08 g (73%) of polyene 13b as brick-red crystals,
mp > 240°C. UV [lmax/nm (e)]: 360 (22100), 430 (sh., 35360), 490
(61880) (EtOH); 470 (47883) (CHCl3). 1H NMR (DMSO-d6) d: 5.97 (d,
2H, Ha, J 14.5 Hz), 6.54 (dd, 2H, Hb, J 13.5 Hz, J 12 Hz), 5.22 (t, 2H,
Hg, J 12 Hz), 6.76 (d, 2H, Hd, J 12.7 Hz), 7.45 (m, 2H, m-HPh, J 7.7 Hz),
7.59 (m, 3H, p-HPh, o-HPh, J 7.04 Hz), 7.28 (s, 2H, H3, H5), 2.89 (s, 12H,
NMe2), 3.56 (s, 3H, NMe). MS (ESI), m/z: 443.2403 [M+H]+ (calc. for
C27H30N4O2, m/z: 443.2442).
†
4-{2,6-Bis[(1E,3E)-4-dimethylaminobuta-1,3-dienyl]-4H-pyran-
4-ylidene}-3-methyl-1-phenyl-1H-pyrazol-5(4H)-one 12a. Aminal 1
(0.18 g, 1.08 mmol) was added to substituted pyran 10a (0.1 g, 0.36 mmol).
The reaction mixture was heated for 15 min at 65°C, then evaporated
in vacuo. Dry Et2O was added to the residue; the precipitate that formed
was filtered off and washed with Et2O to give 0.12 g (76%) of polyene
12a as dark violet crystals, mp 230–233°C. UV [lmax/nm (e)]: 380
(44850), 520 (67600), 580 (sh., 39000) (EtOH); 360 (26000), 540 (46800)
1
(CHCl3). H NMR (DMSO-d6, 80°C) d: 5.87 (d, 2H, Ha, J 14.7 Hz),
7.29–7.33 (m, 2H, Hb), 5.31 (t, 2H, Hg, J 12.0 Hz), 7.12 (d, 2H, Hd,
J 12.7 Hz), 8.04 (d, 2H, o-HPh, J 8.0 Hz), 7.29–7.33 (m, 2H, m-HPh), 7.04
(t, 1H, p-HPh, J 7.3 Hz), 2.95 (s, 12H, NMe2), 7.33 (s, 1H, H3), 6.50 (s,
1H, H5), 2.39 (s, 3H, Me). 13C NMR (DMSO-d6, 80°C) d: 107.58 (Ca),
140.29 (Cb), 97.66 (Cg), 151.28 (Cd), 117.38 (o-CPh), 127.74 (m-CPh),
122.04 (p-CPh), 39.49 (NMe2), 162.76 (C2, C6), 108.28 (C3, C5), 17.59
(Me). MS (ESI), m/z: 443.2433 [M+H]+ (calc. for C27H30N4O2, m/z:
443.2442).
For synthesis and characteristics of compounds 12c–e and 13c,d, see
Online Supplementary Materials.
‡
5-{2,6-Bis[(1E,3E)-4-dimethylaminobuta-1,3-dienyl]-1-methylpyridin-
4(1H)-ylidene}-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione
13e and 1,3-diethyl-5-{2-[(1E,3E)-4-dimethylaminobuta-1,3-dienyl]-1,6-
dimethylpyridin-4(1H)-ylidene}-2-thioxodihydropyrimidine-4,6(1H,5H)-
dione 14. Procedure A. Aminal 1 (0.32 g, 1.88 mmol) was added dropwise
to a suspension of dihydropyrimidine 11e (0.2 g, 0.63 mmol) in 1.2 ml
of dry benzene. The reaction mixture was stirred at 20–22°C. After 2.5 h,
a fine carrot-coloured precipitate formed. Stirring was continued for
more 2 h, the precipitate was separated and washed with dry Et2O to give
a mixture of polyene 13e and tetraene 14 in 2:3 ratio (according to 1H NMR
data in DMSO-d6). After double recrystallization of the mixture of com-
pounds 13e and 14 from EtOH, the mother liquor was cooled to give
tetraene 14 as bright-orange crystals, mp 175–178°C. UV [lmax/nm (e)]:
285 (60149), 380 (46992), 440 (sh., 39473), 490 (54510) (EtOH); 325
4-{2,6-Bis[(1E,3E)-4-dimethylaminobuta-1,3-dienyl]-4H-pyran-
4-ylidene}-3-phenylisoxazol-5(4H)-one 12b. Aminal 1 (0.33 g, 2 mmol)
was added dropwise with stirring to a suspension of substituted pyran
10b (0.2 g, 0.75 mmol) in 2 ml of dry benzene. The reaction mixture was
stirred for 45 min at 20°C and then concentrated in vacuo. The residue
(a black viscous substance) was repeatedly triturated with anhydrous Et2O
which then was poured off. EtOH (1 ml) was added to the residue; the
mixture was triturated and mixed with water (30 ml). After 1.5 h, the
resulting extra-fine precipitate was filtered off and washed with water and
diethyl ether to give 0.11 g (34%) of polyene 12b as dark green crystals,
mp 250°C. UV [lmax/nm (e)]: 363 (26658), 400 (25177), 495 (54798),
595 (26658) (EtOH); 370 (31100), 518 (53317), 546 (sh., 44430) (CHCl3).
1H NMR (DMSO-d6, 80°C) d: 5.55 (d, 2H, Ha, J 12.0 Hz), 7.21 (t, 2H,
Hb, J 12.0 Hz), 5.31 (t, 2H, Hg, J 12.1 Hz), 6.71 (d, 2H, Hd, J 12.1 Hz),
7.44–7.55 (m, 5H, Ph), 7.37 (s, 2H, H3, H5), 2.91 (s, 12H, NMe2). 13C NMR
(DMSO-d6, 80°C) d: 109.39 (Ca), 140.30 (Cb), 98.39 (Cg), 150.32 (Cd),
129.00, 128.47, 132.74 (Ph), 162.71 (C2, C6), 104.19 (C3, C5), 46.37
(NMe2), 149.82 (C8), 97.69 (C7), 105.61 (C4). MS (ESI), m/z: 430.2136
[M+H]+ (calc. for C26H27N3O3, m/z: 430.2125).
4-{2,6-Bis[(1E,3E)-4-dimethylaminobuta-1,3-dienyl]-1-methyl-
pyridin-4(1H)-ylidene}-3-methyl-1-phenyl-1H-pyrazol-5(4H)-one 13a.
Aminal 1 (0.17 g, 1.02 mmol) was added to substituted dihydropyran 11a
(0.1 g, 0.34 mmol). The reaction mixture was stirred for 1 h at 60°C and
then concentrated in vacuo. Et2O was added to the residue. The precipitate
was separated and washed with diethyl ether to give 0.12 g (77%) of
polyene 13a as bright orange crystals, mp 227–229°C. UV [lmax/nm (e)]:
485 (62840) (EtOH); 465 (54170) (CHCl3). 1H NMR (DMSO-d6) d: 3.62
(s, 3H, NMe), 8.12 (s, 2H, H3, H5), 2.41 (s, 3H, Me), 6.07 (d, 2H, Ha, J
14.5 Hz), 7.05 (dd, 2H, Hb, J 14.5 Hz, J 11.1 Hz), 5.28 (t, 2H, Hg, J 11.1
Hz, J 11.9 Hz), 7.00 (d, 2H, J 11.9 Hz), 8.15 (d, 2H, o-HPh, J 7.6 Hz),
7.30 (t, 2H, m-HPh, J 7.9 Hz), 6.98 (t, 1H, p-HPh, J 3.4 Hz), 2.88 (s, 12H,
NMe2). 13C NMR (DMSO-d6) d: 38.11 (NMe), 105.22 (C3, C5), 18.02
(Me), 108.08 (Ca), 141.05 (Cb), 98.15 (Cg), 150.08 (Cd), 118.15 (o-CPh),
128.08 (m-CPh), 122.02 (p-CPh), 40.08 (NMe2), 161.22 (C2, C6). MS
(ESI), m/z: 456.2744 [M+H]+ (calc. for C28H33N5O, m/z: 456.2758).
1
(12530), 390 (26315), 480 (43232) (CHCl3). H NMR (DMSO-d6) d:
6.20 (d, 1H, Ha, J 14.4 Hz), 7.18 (dd, 1H, Hb, J 11.8 Hz, J 14.2 Hz), 5.38
(t, 1H, Hg, J 12.0 Hz), 7.16 (d, 1H, Hd, J 12.0 Hz), 2.95 (s, 6H, NMe2),
3.75 (s, 3H, NMe), 2.54 (s, 3H, Me), 8.42 (s, 1H, H3), 8.98 (s, 1H, H5),
1.15 (t, 6H, NCH2Me, J 6.8 Hz), 4.48 (q, 4H, NCH2Me, J 6.8 Hz). 13
C
NMR (DMSO-d6) d: 106.53 (Ca), 143.25 (Cb), 98.08 (Cg), 151.59 (Cd),
160.35 (C=O), 39.63 (NMe2), 37.40 (NMe), 21.37 (Me), 119.08 (C3),
115.19 (C5), 175.45 (C=S), 12.56 (NCH2Me), 41.86 (NCH2Me). MS
(ESI), m/z: 401.2009 [M+H]+ (calc. for C21H28N4O2S, m/z: 401.2006).
Procedure B. Aminal 1 (0.035 g) was added to 0.04 g of the mixture
of polyene 13e and tetraene 14 obtained as described above and the
mixture was stirred for 75 min at 60–70°C. The crystalline mixture was
concentrated in vacuo. The residue was repeatedly washed with dry Et2O
and boiled with EtOH to give 0.03 g of polyene 13e as red crystals,
mp > 240°C. UV [lmax/nm (e)]: 285 (21690), 430 (15424), 500 (22172)
(EtOH); 325 (7680), 370 (7680), 440 (plateau, 14880), 490 (19280).
1H NMR (DMSO-d6) d: 6.11 (d, 2H, Ha, J 14.4 Hz), 7.05 (dd, 2H, Hb,
J 11.8 Hz, J 14.2 Hz), 5.30 (t, 2H, Hg, J 12.0 Hz), 7.04 (d, 2H, Hd, J 12.0 Hz),
3.7 (s, 3H, NMe), 2.90 (s, 12H, NMe2), 8.67 (s, 2H, H3, H5), 1.15 (t, 6H,
NCH2Me, J 6.8 Hz), 4.48 (q, 4H, NCH2Me, J 6.8 Hz). 13C NMR (DMSO-d6)
d: 107.89 (Ca), 141.67 (Cb), 97.86 (Cg), 150.52 (Cd), 37.90 (NMe), 39.77
(NMe2), 114.19 (C3, C5), 160.34 (C=O), 175.26 (C=S), 12.61 (NCH2Me),
41.83(NCH2Me).MS(ESI),m/z: 482.2582[M+H]+ (calc.forC26H35N5O2S,
m/z: 482.2584).
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Mendeleev Commun., 2014, 24, 377–379
13C NMR, UV and micrOTOF mass spectra. Assignment of signals
References
1
in the H and 13C NMR spectra was based on COSY, NOESY,
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HSQC and HMBC 2D experiments. Dyes 12a–e possess a con-
formation with a sharp angle between the chromophores since
the NOESY and ROESY spectra demonstrate correlation between
the H3/H5 and Ha protons but no correlation between the H3/H5
and Hb protons, whereas dyes 13a–e and 14 have a conformation
with an obtuse angle between the chromophores since the protons
of the NMe group show coupling with Ha protons but not with
Hb protons, which give correlation with the H3/H5 protons; there
is no correlation between the Ha and H3 protons.
The configuration of double bonds in all the dyes was deter-
mined from NOESY and ROESY NMR spectra and the vicinal
coupling constants of methine protons (J 11.1–14.5 Hz). It follows
from these data that the protons at the Ca=Cb and Cg=Cd double
bondsaretrans-arranged, whilethedienemoietiesinpolymethine
chains Ca=Cb and Cg=Cd exist predominantly in the S-trans-
conformation.
The spectrofluorescent and photochemical properties of cross-
conjugated polyenes 12a–e, 13a–e and 14 will be described in
detail in a subsequent paper.
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This study was supported by the Russian Foundation for
Basic Research (project no. 10-03-00647-a).
287, 8.
Online Supplementary Materials
Supplementary data associated with this article can be found
in the online version at doi:10.1016/j.mencom.2014.11.024.
Received: 17th February 2014; Com. 14/4307
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