Quinonic enaminones; synthesis of new dialkylaminovinyl and bis(dialkylaminovinyl) derivatives of quinones

Article abstract of DOI:10.1055/s-2000-6314

The reaction of halogenated quinones with a variety of secondary amines in the presence of acetaldehyde proceeds via intermediate formation of enamines and produces mono quinonic enaminones. The use of two equivalents of enamine results in both symmetrica

Full text of DOI:10.1055/s-2000-6314

PAPER
1087
Quinonic Enaminones; Synthesis of New Dialkylaminovinyl and
Bis(dialkylaminovinyl) Derivatives of Quinones
Mohammad Alnabari, Shmuel Bittner*
Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
E-mail: bittner@bgumail.bgu.ac.il
Received 31 January 2000; 14 March 2000
O
O
Abstract: The reaction of halogenated quinones with a variety of
R2
R2
R1
R1
R1
R2
R2
secondary amines in the presence of acetaldehyde proceeds via in-
termediate formation of enamines and produces mono quinonic
enaminones. The use of two equivalents of enamine results in both
symmetrical and nonsymmetrical bis-derivatives.
Toluene
room temp.
+
HNR3R4
+
CH3CHO
O
O
NR3R4
1-4
5-8
Key words: quinones, enamines, quinonic enaminones
1,5 R1 = R2 = Cl
2,6 R1= R2 = Br
4,8 R1 = Cl, R2 =
Donor/acceptor substituted organic molecules exhibit in-
teresting optical and electronic properties. They are used
in non linear optics (NLO),1-3 in molecular electronic de-
vices,4-6 and in artificial photosynthetic models.7-9
3,7 R1 = Cl, R2= CN
5a R3 = R4 = C2H5
5c R3 = C2H5, R4 = c -C6H11 5d R3 = R4 = CH3
5b R3 = CH3, R4 = Bn
Several novel donor/acceptor naphthoquinone derivatives
e.g. substituted benzo[b]phenoxazine-6,11-diones and
their N-tosyl derivatives were recently prepared.10 UV-
Vis measurements and theoretical calculations proved the
existence of an intramolecular electron transfer from the
HOMO of the donor moiety to the LUMO of the acceptor
(the quinonic fragment of the molecules).
5e R3 = R4 = Bn
6b R3 = CH3, R4 = Bn
7a R3 = R4 = Bn
8a R3 = CH3, R4 = Bn
8c R3 = C2H5, R4 = Ph
6a R3 = R4 = Bn
6c R3 = R4 = C2H5
7b R3 = R4 = C2H5
8b R3 = R4 = C2H5
8d R3 = R4 = Bn
8e R3 = C2H5, R4 = c- C6H11
In this paper, we describe the synthesis and properties of
a different type of quinones which might show non-linear
optical properties. These are the 3-dialkylaminovinyl de-
rivatives of benzoquinone 5-7 and of naphthoquinone 8
and also the 3,6-bis(dialkylaminovinyl) derivatives of
benzoquinone 9. As can be seen from Scheme 1, the
quinonic moieties were derived from chloranil, bromanil,
DDQ, and 2,3-dichloronaphthoquinone.
Scheme 1
O
O
O
Cl
Cl
Cl
Cl
+
NR3R4
H
O
NR3R4
The mono substituted enaminones 5-8 are combined do-
nor-acceptor materials while the bis-substituted enamino-
nes 9 are composed of two donors and one acceptor
covalently bonded in the same molecule.The reaction pro-
ceeds via formation of an enamine,11 which reacts with the
haloquinone as describe in Scheme 2. Thus, using one
equivalent of the enamine, the “blue quinones” 5-8 were
formed in medium to high yields. The use of two equiva-
lents of the enamine and tetrahalobenzoquinones resulted
in formation of the red symmetrical bis-enaminones (9b,
9c, 9e).
4
4'
O
O
Cl
-HCl
NR3R4
8a-e
Scheme 2
Nonsymmetrical bis-enaminones, in which two different
secondary amines are attached to the quinonic backbone
(9a, 9d) were prepared from the trihalobenzoquinones 2
and 3 as described in Scheme 3.
The coupling constant are J = 12-13 Hz which proves
that the compounds are in the E configuration.
The electronic absorption spectra of the blue mono enam-
inones compounds 5-8 show the expected naphto-
quinonic bands in the UV region around 270-280 nm and
at 320-340 nm. In addition, another band appeared in the
visible region between 600-700 nm. This band is known
For spectroscopic data of compounds 5–9, see Tables 1
and 2. The vinylic protons of the products appear in the 1H
NMR spectrum as two doublets, at d = 5.54-5.93 and at
d = 8.25-8.89 (for the proton adjacent to the quinone).
Synthesis 2000, No. 8, 1087–1090 ISSN 0039-7881 © Thieme Stuttgart · New York

1088
M. Alnabari, S. Bittner
PAPER
Table 1 Quinonic Enaminones 5−8
Products
5a
Yield1
(%)
Mp (∞C)
122-123
132-134
102-103
IR (KBr)
1H NMR (CDCl3)
d (ppm), J (Hz)
MS (m/z)
n cm−1
90
95
90
2960, 2890, 1583, 1497,
1439
8.25 (d, 1 H, J = 12.6), 5.64 (d, 1 H, J =
13.0), 3.48 (m, 4 H), 1.19 (t, 6 H)
310 [M+3H]+,
292, 280
5b
2955, 2911, 2851, 1664,
1581, 1525
8.54 (d, 1 H, J = 12.6), 7.45 (m, 5 H), 5.61
(d, 1 H, 12.8), 4.72 ( s, 2 H), 3.40 (s, 3 H)
357[ M+2H]+,
322, 265
5c2,3
2932, 2855, 1663, 1591,
1514
8.32 (d, 1 H, J = 12.8), 5.67 (d, 1 H, J =
12.5), 3.43−3.52 (m, 3 H), 1.15−1.85 (m,
13 H)
263 [M+2H]+,
326, 282
5d
5e
76
93
146-148
122-124
2961, 2820, 1659, 1588,
1521
8.32 (d, 1 H, J = 12.8), 5.58 (d, 1 H, J =
12.8), 3.23 (s, 6 H)
281 [M+2H]+,
248, 230, 168
2980, 2851, 1665, 1588,
1521
8.66 (d, 1 H, J = 13.0), 7.37 (s, 5 H), 7.24
(s, 5H), 5.88 (d, 1 H, J = 12.9), 4.50 (br s,
4 H)
434 [M+3H]+,
364, 305, 230,
196
6a
6b
76
65
130-132
148-149
2953, 2830, 1640, 1532,
1490
8.59 (d, 1 H, J = 13.0), 7.36 (br s, 10 H),
5.93 (d, 1 H, J = 12.8), 4.48 (br s, 4 H)
566 [M+3H]+,
487, 409, 344,
196
2965, 2889, 1600, 1497
8.49 (d, 1 H, J = 12.8), 7.40 (m, 5 H), 5.72
(d, 1 H, J = 12.9), 4.52 (s, 2 H), 2.91 (s, 3
H)
491 [M+3H]+,
487, 367, 334
6c
7a
7b
8a
67
50
44
90
140-142
148-150
132-134
96-97
2834, 2872, 1630, 1560
3165, 2198, 1563, 2970
3160, 2195, 2972, 1560
1674, 1599, 1569
8.26 (d, 1 H, J = 12.8), 5.78 (d, 1 H, J =
12.6), 3.49 (q, 4 H), 1.25 (t, 6 H)
425 [M+2H]+,
365, 342
8.89 (d, 1 H, J = 12.4), 7.34 (m, 10 H), 5.55
(d, 1 H), 4.62 (s, 2 H), 4.41 (s, 2 H)
417 [M+3H]+,
330, 180
8.53 (d, 1 H, J = 12.7), 5.54 (d, 1 H, J =
12.7), 3.76 (q, 4 H), 1.18 (t, 6 H)
291 [M+2H]+,
256, 204
8.70 (d, 1 H, J = 12.6), 8.15 (m,1 H), 7.99
(m, 1 H), 7.64 (m, 2 H), 7.34-7.39 (m, 5
H), 5.71 (d, 1 H, J = 12.9), 4.52 (s, 2 H),
2.88 (br s, 3 H)
340 [M+3H]+,
318, 304
8b
8c
8d
86
83
82
86-88
92-93
1678, 1670, 1562, 1591
1690, 1600,1570, 1495
1682, 1609, 1582, 1478
8.42 (d, 1 H, J = 12.9), 8.13 (m, 1 H), 7.95
(m, 1 H), 7.82 (m, 2 H), 5.61 (d, 1 H, J =
12.9), 3.46 (m, 4 H), 1.15 (t, 6 H)
292 [M+3H]+,
256, 218, 159
8.08 (m, 1 H), 7.95 (m, 1 H), 7.36 (d, 1 H,
J = 12.2), 7.08 (m, 2 H), 6.55 (m, 5 H), 5.63
(br s, 1 H), 3.01 (q, 2 H),1.16 (t, 3 H)
338 [M+H]+,
209, 192, 159
154-156
8.81 (d, 1 H, J = 13.0), 8.11 (m, 1 H), 7.99
(m, 1 H), 7.65 (m, 2 H), 7.39 (m, 5 H), 7.35
(m, 5 H), 5.92 (d, 1 H, J = 13.0), 4.49 (s, 4
H)
416 [M+3H]+,
378, 324, 288,
225
8e
90
118-119
2942, 1682, 1600, 1502,
1555
8.57 (d, 1 H, J = 12.7), 8.12 (m, 1 H), 7.98
(m, 1 H), 7.67 (m, 2 H), 5.76 (d, 1 H,
J = 13.0), 3.49 (m, 3 H), 1.89 (m, 4 H), 1.48
(m, 9 H)
344 [M+H]+,
310, 262, 226,
192, 159
1.Yields of isolated products based on the haloquinone were not optimized. Satisfactory microanalysis was obtained: C 0.31; H 0.19; N
0.28; Cl 36.
2
.
13C NMR (CDCl3): d (ppm) = 35, 61, 94, 128, 139, 140, 154, 177, 191. The other compounds also gave the correct 13CNMR spectra.
3. lmax (MeOH) = 208, 320, 694 nm. Similar absorptions were obtained for the other compounds.
Synthesis 2000, No. 8, 1087–1090 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Synthesis of New Dialkylaminovinyl and Bis(Dialkylaminovinyl) Derivatives of Quinones
1089
Table 2 Quinonic Bis-enaminones (9)
Products
Yield3
(%)
Mp(∞C)
IR (KBr)
1H NMR (CDCl3)
d (ppm), J (Hz)
MS (m/z)
n (cm−1)
9a
70
174-176
2960, 2895, 2816,
1583, 1497, 1439
8.68 (d, 2 H, J = 12.9), 7.34-7.29 (m, 5H),
5.55 (d, 2 H, J = 12.9), 4.41 (s, 2H), 2.83 (br
s, 7H), 1.18 (br, s, 6H)
420 [M+2H]+, 385,
351
9b
54
72
156-158
162-163
2952, 2850, 1665,
1592, 1522
8.73 (d, 2 H, J = 12.9), 7.22-7.28 (m, 20 H),
5.75 (d, 2 H, J = 13.0), 4.43 (s, 8 H)
618 [M+H]+, 542,
430, 196
9c1
2952, 2886, 1528,
1501
8.44 (d, 2 H, J = 12.8), 5.43 (d, 2 H, J = 12.5),
3.39 (t, 4 H), 1.20 (t, 12 H, J = 5.8)
373 [M+3H]+, 337,
302
9d2
9e
65
90
156-158
192-194
3019, 2911, 1629,
1595, 1514
8.70 (d, 2 H, J = 12.6), 7.3 (m, 10 H), 5.60(br
s, 2 H), 4.48 (s, 4 H), 2.88 (br s, 4 H)
468 [M+2H]+, 430,
375
480 [M+2H]+, 444,
351
2934, 2854, 1578,
1508, 1432
8.75 (d, 2 H, J = 12.8), 5.70 (d, 2 H, J = 12.8),
3.38 (q, 2 H), 3.1 (t, 1 H), 1.71 (m, 4 H),
1.43-1.54 (m, 12 H), 1.23 (t, 6 H)
1 13C –NMR (CDCl3): d (ppm) = 14, 43, 51, 67, 118, 141, 176. The other compounds alsogave the correct 13CNMR spectra.
2 lmax (MeOH) = 208, 352, 552 nm. Similar absorptions were obtained for the other compounds.
3 Satisfactory microanalysis was obtained: C 0.31; H 0.19; N 0.28; Cl 36.
General Procedure for the Preparation of 5-8
to arise from HOMO to LUMO transition, which corre-
To a solution of tetrahalogenated 1,4-benzoquinone or 2,3-dichlo-
sponds, in this case, to intramolecular electron transfer
from the donor enamine moiety to the acceptor quinonic
moiety of the molecule. Interestingly, the electronic ab-
sorption spectra of the red bis-enaminones 9 do not show
the charge transfer absorption in the Vis region.
ronaphthoquinone (4.4 mmol) in toluene (60 mL) was added a mix-
ture of acetaldehyde (4.4 mmol) and a secondary amine (8.8 mmol)
in toluene (20 mL). The mixture was stirred at r.t. until the disap-
pearance of the starting quinone (TLC). The blue colored solution
was evaporated under reduced pressure and the resulting solid was
purified by silica gel column chromatography using CH2Cl2 as the
eluent. The products were recrystallized from n-hexane or petro-
leum ether (60-80 °C).
In the IR spectra, the two typical quinonic absorptions ap-
pear in the region of 1580-1690 cm-1, and the conjugated
vinylic moiety is observed between 2920-3030 cm-1.
Symmetrical Bis-quinonic Enaminones (9b-9d)
A solution of p-chloranil (4.4 mmol) in toluene (70 mL) was added
slowly to a cooled and stirred solution of acetaldehyde (8.8 mmol)
and secondary amine (17.6 mmol). The stirring was continued for
2 h and then at r.t. for 2-5 h until TLC showed the disappearance of
the chloranil and the mono substituted product.
R6R5N
O
O
R2
R2
R1
R1
+ CH3CHO
HNR 5R6
Toluene
+
room temp
R2
The red purple solution was evaporated under reduced pressure and
purified using neutral alumina column chromatography and CH2Cl2
as the eluent. The products were recrystallized from n-hexane.
O
O
NR3R4
NR3R4
5
9
Nonsymmetrical Bis-quinonic Enaminones (9a, 9e)
R1 = R2 = Cl
A solution of acetaldehyde (4.4 mmol) and secondary amine (8.8
mmol) in toluene (20 mL) was added dropwise to a cold solution of
the monoquinonic enaminone 5 (4.4 mmol) in toluene (70 mL). The
mixture was stirred for 2-7 h until the disappearance of the starting
quinone 5 (TLC). The isolation and purification is as above for 9b.
9a R3 = R4 =C2H5; R5 = CH3, R6 = Bn
9b R3 = R4 = R5 = R6 = Bn
9c
R
3 = R4 = R5 = R6= C2H5
9d R3 = R5 = CH3, R4 = R6 = Bn
9e R3 = R5 = C2H5, R4 = R6 = c - C6H11
Acknowledgement
Scheme 3
This research was supported by the Israel Science Foundation foun-
ded by the academy of Science and Humanities. We wish to thank
Ethel Solomon for skilled technical help.
IR spectra were recorded on a Nicolet 5ZDX FT-IR spectrometer.
1H and 13C NMR were run on a Bruker WP 200 SY spectrometer.
Mass spectra (CI in CH4) were obtained on a Finnigan 4020 quadro-
pole spectrometer and UV-Vis spectra were measured using
Hewlett Packard 8452A diode array spectrophotometer. All re-
agents were of commercial quality. Mps were determined using a
Thomas-Hoovar capillary apparatus and are uncorrected.
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Synthesis 2000, No. 8, 1087–1090 ISSN 0039-7881 © Thieme Stuttgart · New York

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M. Alnabari, S. Bittner
PAPER
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Synthesis 2000, No. 8, 1087–1090 ISSN 0039-7881 © Thieme Stuttgart · New York