Synthesis of aryl-substituted 1,3-butadiones

Article abstract of DOI:10.1081/SCC-120016361

The synthesis of several electron donor substituted 1-aryl-1,3-butadiones and their use as ligands in the formation of scandium(III) complexes is reported.

Full text of DOI:10.1081/SCC-120016361

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Synthesis of Aryl-Substituted 1,3-Butadiones
Burkhard König a
a Institut für Organische Chemie, Universität Regensburg, Regensburg, Germany
Version of record first published: 17 Aug 2006.
To cite this article: Burkhard König (2003): Synthesis of Aryl-Substituted 1,3-Butadiones, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 33:6, 967-976
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SYNTHETIC COMMUNICATIONSÕ
Vol. 33, No. 6, pp. 967–976, 2003
Synthesis of Aryl-Substituted 1,3-Butadiones
*
Burkhard Konig
Institut fur Organische Chemie, Universitat
Regensburg, Regensburg, Germany
ABSTRACT
The synthesis ofseveral electron donor substituted 1-aryl-1,3-buta-
diones and their use as ligands in the formation of scandium(III)
complexes is reported.
Key Words: Ketone; Scandium complexes; Acetylacetonate ligands.
Acetyl acetonates are well known ligands for the preparation of
stable complexes with many metal ions. The reaction oflithiated imines
ofacetone with esters followed by imine hydrolysis is a general synthetic
route for the preparation of 1-substituted 1,3-butadiones. We report here
the synthesis ofsome electron rich 1-aryl-1,3-butadiones by this method.
*Correspondence: Burkhard Konig, Institut fur Organische Chemie, Universitat
Regensburg, D-93040 Regensburg, Germany; E-mail: burkhard.Koenig@
chemie.uni-regensburg.de.
967
DOI: 10.1081/SCC-120016361
Copyright & 2003 by Marcel Dekker, Inc.
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968
Konig
Alkyl aminobenzoates (1)[1] as readily available starting materials[2] were
reacted with lithiated N-isopropylidene cyclohexylamine[3] (2) in THF at
0ꢀC to the intermediate keto enamines 3, which were hydrolyzed to give
the target 1,3-butadiones 4[4] (Sch. 1a). The hydrolysis of 3 is slow in
acetic acid/THF at room temp., but much faster if refluxed in a mixture
ofaqueous 2 M HCl and acetone.
A 1,3-butadione in which the electron rich arene is separated from
the dicarbonyl moiety was synthesized starting from 5, which reacted
with ethyl acetate and sodium to give ester 6.[5] The double bond was
hydrogenated and the reaction ofthe ester with 2 followed by acid
catalyzed hydrolysis gave compound 8 (Sch. 2).
Proton and carbon NMR spectra ofcompounds 4a–d (Sch. 1b) show
signals for keto- and enol-tautomers with the enol form as the major
isomer (80–90%). The fraction of the enol tautomere is smaller in 8
(65%) due to the lack ofdirect conjugation with the aromatic system.
The absorption in UV/Vis spectra ofcompounds 4a–d reaches longer
wavelength and is more intensive as for the parent aromatic chromo-
phore N,N-dimethylaniline.[6] Like N,N-dimethylaniline[7] compounds
4a–d emit light upon excitation, but their emission maxima are shifted
bathochromically. The photophysical properties of 8 are, as expected,
similar to that of N,N-dimethyl-aniline. The redox potentials of
compounds 4a–d and 8 were examined by cyclic voltammetry and are
summarized in Table 1. The oxidation of 4a–d requires a more positive
potential (þ150 À200 mV) than the corresponding anilines due to the
electron withdrawing character ofthe conjugated 1,3-butadione moiety.
Compounds 4a–d were deprotonated with ammonia[10] and reacted
with scandium(III) chloride to yield the corresponding complexes 9a–d
Scheme 1a. Synthesis ofamino-substituted 1-aryl-1,3-butadiones.

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Aryl-Substituted 1,3-Butadiones
969
Scheme 1b. Synthesis ofamino-substituted 1-aryl-1,3-butadiones.
Table 1. Electrochemical data of 4a–d and 8.
4a
4b
4c
4d
8
a, b
p, a
E
½VŠ 0.51 (0.37)[8] 0.52 (0.32)[8] 0.36 (0.16)[9] 0.23 (À0.04)[9] À0.09c
aPotentials were determined by cyclic voltammetry in 0.1 M NBu4PF6 CH3CN
solution vs Fc/Fcþ at 298 K with a scan rate of0.1 V/s.
bEp,a ¼ anodic peak potential; the oxidation is irreversible under the experimental
conditions. Oxidation potential for the corresponding anilines are given in pa-
renthesis. Reduction ofthe 1,3-butadione moiety requires potentials more nega-
tive than ꢀ2.24 V vs Fc/Fcþ.
cFormal reduction potential; redox process is reversible.
(Sch. 3). The UV/Vis absorption ofthe complexes is shitfed bathochro-
mic and their emission intensities are drastically reduced in comparison
with the corresponding ligands. The oxidation potentials of 9a (0.72 V)[11]
and 9b (0.70 V) are more positive as in the ligands, while 9c (0.43) and 9d
(0.21) have similar oxidation potentials as the corresponding non-coor-
dinated 1,3-butadiones.
EXPERIMENTAL
All 1H NMR spectra were recorded at 400 MHz, all 13C NMR
spectra at 100 MHz in CDCl3. The multiplicity ofthe 13C signals

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970
Konig
Scheme 2. Synthesis of1,3-butadione 8.
4a: R=4-Me2N-C6H4-
4b: R=4-Et2N-C6H4-
4c: R=3-Me2N-4-MeO-C6H3-
4d: R=3,5-(Me2N)2-C6H3-
9a: R=4-Me2N-C6H4-
9b: R=4-Et2N-C6H4-
9c: R=3-Me2N-4-MeO-C6H3-
9d: R=3,5-(Me2N)2-C6H3-
(74%)
(62%)
(74%)
(67%)
Scheme 3. Synthesis ofscandium(III) acetyl acetonate complexes.
was determined with the DEPT technique and quoted as: (þ) for CH3 or
CH, (À) for CH2 and (Cquat) for quaternary carbons. CC means column
chromatography on silica gel. PE means petrol ether with a boiling range
ꢀ
of60–70 C. EA means ethyl acetate.
1-(4-N,N-Dimethylaminophenyl)-1,3-butadione (4a).[4] To a solution
of N-isopropylidene cyclohexylamine (1.52 g, 11 mmol) in THF
(100 mL) was added at 0ꢀC LDA (12 mmol), the mixture was stirred

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Aryl-Substituted 1,3-Butadiones
971
for 30 min, methyl 4-N,N-dimethylaminobenzoate (1.93 g, 10 mmol)
was added and the reaction mixture was kept at room temp. overnight.
The solvent was removed in vacuo, dichloromethane (100 mL) and diluted
aqueous acetic acid (10 mL) were added and the mixture was stirred for
2 h. The organic phase was separated, washed with water, dried over
Na2SO4 and evaporated in vacuo. The crude product was purified by
CC (CH2Cl2/MeOH, 99:1) to give 280 mg (21%) of 4a (Rf ¼ 0.44);
ꢀ
yellow solid, M.p. 113 C. IR (KBr): ꢀ ¼ 2916 cmÀ1, 1611, 1377, 1189,
~
783, 505. UV/Vis (CH3CN): ꢁmax (lg ") ¼ 200 nm (4.273), 244 (3.776),
1
362 (4.395). H NMR: ꢂ ¼ 2.12 (s, 3H, enol), 2.25 (s, 3H, keto), 3.04 (s,
6H, enol), 3.05 (s, 6H, keto), 3.98 (s, 2H, keto), 6.06 (s, 1H, enol), 6.64 (m,
4H, keto and enol), 7.81 (m, 4H, keto and enol), 16.52 (s, 1H, enol).
13C NMR: ꢂ ¼ 24.9 (þ), 30.2 (þ), 39.9 (þ), 39.9 (þ), 54.7 (À), 94.9 (þ),
110.7 (þ), 111.0 (þ), 122.0 (Cquat), 129.0 (þ), 131.0 (þ), 153.1 (Cquar),
185.1 (Cquat), 189.4 (Cquat). MS (70 eV), m/z (%): 205 (100) [Mþ], 190 (38)
[Mþ ÀCH3], 162 (4) [Mþ ÀC(O)CH3]. ÀC12H15NO2: calcd. C 70.22, H
7.37, N 6.82; found C 70.04, H 7.30, N 6.81.
1-(4-N,N-Diethylaminophenyl)-1,3-butadione (4b). N-Isopropylidene
cyclohexylamine (1.95 g, 14 mmol), LDA (14 mmol) and ethyl 4-N,N-
diethylaminobenzoate (2.21 g, 10 mmol) were allowed to react as
described for 4a. The solution was neutralized with 7.5 mL ofHCl
(2 M), evaporated to a volume of30 mL, dichloromethane (200 mL)
was added and the organic phase was separated, washed with sat. aque-
ous NH4Cl (4 Â 50 mL), water (1 Â 50 mL), dried over Na2SO4 and evap-
orated in vacuo. CC (CH2Cl2/MeOH 99:1) yielded 300 mg (13%) of 4b
ꢀ
(Rf ¼ 0.44); yellow solid, M.p. 53 C. IR (KBr): ꢀ ¼ 2971 cmÀ1, 2931, 2900,
~
1603, 1522, 1196, 1009, 779. UV/Vis (CH3CN): ꢁmax (lg ") ¼ 198 nm
1
(4.279), 246 (3.749), 372 (4.530). H NMR: ꢂ ¼ 1.22 (m, 12H, keto and
enol), 2.13 (s, 3H, enol), 2.28 (s, 3H, keto), 3.43 (m, 8H, keto and enol),
3.97 (s, 2H, keto), 6.05 (s, 1H, enol), 6.64 (m, 4H, keto and enol), 7.80 (m,
4H, keto and enol), 16.55 (s, 1H, OH, enol). 13C NMR: ꢂ ¼ 12.4 (þ), 12.5
(þ), 24.8 (þ), 30.2 (þ), 44.5 (À), 44.5 (À), 54.7 (À), 94.7 (þ), 110.2 (þ),
110.5 (þ), 121.2 (Cquat), 129.3 (þ), 131.3 (Cquat), 150.9 (Cquat), 185.0
(Cquat), 189.0 (Cquar). MS (70 eV), m/z (%): 233 (42) [Mþ], 218 (100)
[Mþ ÀCH3], 190 (10) [Mþ ÀC(O)CH3]. ÀC14H19NO2: Calcd. C 72.07,
H 8.21, N 6.00; found C 72.03, H 8.21, N 5.97.
1-(3-N,N-Dimethylamino-4-methoxyphenyl)-1,3-butadione (4c). N-
Isopropylidene cyclohexylamine (1.64 g, 12 mmol), LDA (12 mmol) and
methyl 3-N,N-dimethylamino-4-methoxybenzoate (1.68 g, 8 mmol) were
reacted and worked up as described before. To the obtained yellow oil
was added water (10 mL), aqueous HCl (10 mL, 2 M) and acetone
(80 mL) and the mixture was refluxed for 2.5 h. Aqueous NaHCO3 was

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972
Konig
added to adjust the pH to neutral, the mixture was diluted with dichloro-
methane (100 mL), the organic phase was separated, washed with
sat. aqueous NH4Cl and water, dried over Na2SO4 and the solvent was
removed in vacuo. The crude product was purified by CC
(CH2Cl2/MeOH 99:1) to yield 1.14 g (61%) of 4c (Rf ¼ 0.25) as a yellow
oil. IR (KBr): ꢀ ¼ 2944 cmÀ1, 2834, 2783, 1592, 1510, 1252, 781. UV/Vis
~
(CH3CN): ꢁmax (lg ") ¼ 192 nm (4.166), 200 (4.155), 256 (4.194),
1
284 (4.059), 314 (4.075). H NMR: ꢂ ¼ 2.17 (s, 3H, enol), 2.28 (s, 3H,
keto), 2.83 (s, 12H, keto and enol), 3.88 (s, 2H, keto), 3.95 (s, 3H,
enol), 4.05 (s, 3H, keto), 6.11 (s, 1H, enol), 6.87 (m, 2H, keto and enol),
7.60 (m, 4H, keto and enol), 16.34 (s, 1H, enol). 13C NMR: ꢂ ¼ 25.1 (þ),
43.1 (þ), 43.2 (þ), 54.8 (À), 55.6 (þ), 55.7 (þ), 95.8 (þ), 110.1 (þ), 110.4
(þ), 116.9 (þ), 122.5 (þ), 124.9 (Cquat), 127.7 (Cquat), 155.9 (Cquat),
184.9 (Cquat), 190.9 (Cquat). MS (70 eV), m/z (%): 235 (100) [Mþ],
220 (76) [Mþ ÀCH3]. ÀC13H17NO3: Calcd. C 66.35, H 7.29, N 5.96;
found C 66.69, H 7.39, N 5.89.
1-[3,5-(N,N,N0,N0-Tetramethylamino)phenyl]-1,3-butadione (4d). N-
Isopropylidene cyclohexylamine (735 mg, 5.3 mmol) dissolved in THF
ꢀ
(50 mL) was treated with 5.3 mmol ofLDA at 0 C as described before.
Methyl 3,5-N,N,N0,N0-tetramethylaminobenzoate (790 mg, 3.6 mmol)
was added at 0ꢀC, the mixture was stirred at room temp. overnight,
dichloromethane (100 mL) was added, the solution was washed with
sat. aqueous NH4Cl (3 Â 100 mL) and water (1 Â 100 mL), dried
over Na2SO4 and the solvent was evaporated in vacuo. The yellow residue
was heated in 50 mL ofacetone and 3 mL ofHCl (2 M) for 3 h to reflux,
the reaction mixture was diluted with dichloromethane (200 mL)
and adjusted to neutral pH with sat. aqueous NaHCO3. The organic
phase was separated, washed with sat. aqueous NH4Cl and water,
dried over MgSO4 and the solvent was removed in vacuo.
CC (CH2Cl2/MeOH 99:1) ofthe crude product gave 610 mg (69%)
of 4d (Rf ¼ 0.64) as
a
yellow solid, M.p. 88ꢀC. IR (KBr):
ꢀ ¼ 2914 cmÀ1, 2817, 1591, 1492, 1442, 1384, 1243, 771. UV/Vis
(CH3CN): ꢁmax (lg ") ¼ 192 nm (4.051), 240 (4.471), 296 (4.107), 340
(3.866). 1H NMR: ꢂ ¼ 2.11 (s, 3H, enol), 2.19 (s, 3H, keto), 2.91
(s, 24H, keto and enol), 3.98 (s, 2H, keto), 6.06 (s, 1H, enol), 6.13
(m, 2H, keto and enol), 6.57 (d, 4J ¼ 2.2 Hz, 2H, enol), 6.62 (d,
4J ¼ 2.3 Hz, 2H, keto), 16.20 (s, 1H, enol). 13C NMR: ꢂ ¼ 25.6 (þ), 40.7
(þ), 40.8 (þ), 55.5 (À), 96.9 (þ), 100.7 (þ), 100.8 (þ), 102.0 (þ), 136.3
(Cquat), 151.6 (Cquat), 185.8 (Cquat), 192.7 (Cquat). MS (70 eV), m/z (%):
248 (100) [Mþ], 233 (30) [Mþ ÀCH3], 205 (76) [Mþ ÀC(O)CH3].
ÀC14H20N2O2: Calcd. C 67.70, H 8.12, N 11.29; found C 67.68, H
8.23, N 11.11.
~

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Aryl-Substituted 1,3-Butadiones
973
Tris[1-(4-N,N-dimethylaminophenyl)-1,3-butadionate]scandium(III) (9a).
1-(4-N,N-Dimethylaminophenyl)-1,3-butadione (100 mg, 0.48 mmol) (4a)
and scandium(III) chloride (27 mg, 0.11 mmol) were dissolved in 30 mL of
methanol. Ammonia was bubbled through the solution and 9a precipi-
tates. The crystals were collected by filtration and washed with a small
amount ofmethanol. Yield: 54 mg (74%) of 9a as yellow crystals, M.p.
ꢀ
257 C. IR (KBr): ꢀ ¼ 2919 cmÀ1, 2871, 2809, 1570, 1502, 778, 424.
~
UV/Vis (CH3CN): ꢁmax (lg ") ¼ 198 nm (4.817), 244 (4.278), 316
1
(4.244), 386 (5.046). H NMR: ꢂ ¼ 2.10 (s, 9H), 3.00 (s, 18H), 6.15 (s,
3H), 6.59 (d, 3J ¼ 9.0 Hz, 6H), 7.86 (d, 3J ¼ 9.0 Hz, 6H). 13C NMR:
ꢂ ¼ 27.5 (þ), 40.1 (þ), 97.8 (þ), 110.8 (þ), 125.3 (Cquat), 129.8 (þ),
152.6 (Cquat), 183.0 (Cquat), 190.4 (Cquat). MS (70 eV), m/z (%): 657
(32) [Mþ], 453 (100) [Mþ ÀC12H14NO2].
Tris[1-(4-N,N-diethylaminophenyl)-1,3-butandionate]scandium(III) (9b).
1-(4-N,N-Diethylaminophenyl)-1,3-butadione (90 mg, 0.38 mmol) (4b)
and scandium(III) chloride (22 mg, 0.09 mmol) were dissolved in 15 mL
ofmethanol and ammonia was bubbled through the solution. The pre-
cipitated crystals were collected by filtration after 2 h, washed with water
and dried to give 42 mg (62%) of 9a as yellow crystals, M.p. 218ꢀC. IR
(KBr): ꢀ ¼ 2971 cmÀ1, 2928, 1607, 1569, 1502, 1193, 777, 428. UV/Vis
~
(CH3CN): ꢁmax (lg ") ¼ 198 nm (4.803), 246 (4.222), 318 (4.244), 396
1
3
(5.050). H NMR: ꢂ ¼ 1.17 (t, J ¼ 7.0 Hz, 18H), 2.08 (s, 9H), 3.36 (q,
3J ¼ 7.0 Hz, 12H), 6.11 (s, 3H), 6.55 (d, 3J ¼ 9.0 Hz, 6H), 7.83 (d,
3J ¼ 9.0 Hz, 6H). 13C NMR: ꢂ ¼ 12.5 (þ), 27.5 (þ), 44.4 (À), 97.5 (þ),
110.2 (þ), 124.5 (Cquat), 130.1 (þ), 150.1 (Cquat), 182.9 (Cquat), 190.0
(Cquat). MS (70 eV), m/z (%): 741 (78) [Mþ], 509 (100) [Mþ
ÀC14H19NO2].
Tris[1-(3-N,N-dimethylamino-4-methoxyphenyl)-1,3-butandionate]scan-
dium(III) (9c). A solution of1-(3- N,N-dimethylamino-4-methoxyphenyl)-
1,3-butadione (200 mg, 0.85 mmol) (4c) and scandium(III) chloride (47 mg,
0.19 mmol) in 10mL ofmethanol was treated with ammonia as described
above and left overnight. Precipitated crystals were collected by filtration
and washed with a small amount ofmethanol to yield 105 mg (74%) of
ꢀ
9c as yellow crystals, M.p. 142 C. IR (KBr):ꢀ ¼ 2942 cmÀ1, 2831, 2781,
~
1548, 1532, 1274, 779, 427. UV/Vis (CH3CN): ꢁmax (lg ") ¼ 192 nm (4.727),
204 (4.721), 262 (4.680), 354 (4.712). 1H NMR: ꢂ ¼ 2.14 (s, 9H), 2.72
(s, 18H), 3.91 (s, 9H), 6.20 (s, 3H), 6.79 (d, 3J ¼ 8.5 Hz, 3H), 7.54
4
3
4
(d, J ¼ 2.0 Hz, 3H), 7.60 (dd, J ¼ 8.5 Hz, J ¼ 2.0 Hz, 3H). 13C NMR:
ꢂ ¼ 27.6 (þ), 43.1 (þ), 55.5 (þ), 98.8 (þ), 110.1 (þ), 117.9 (þ), 123.1
(þ), 130.6 (Cquat), 141.9 (Cquat), 155.3 (Cquat), 183.1 (Cquat),
192.3 (Cquat). MS (70 eV), m/z (%): 747 (86) [Mþ], 513 (100) [Mþ
ÀC13H16NO3].

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974
Konig
Tris[1-(3,5-N,N,N0,N0-tetramethylamino)phenyl-1,3-butandionate]scan-
dium(III) (9d). 1-[3,5-N,N,N0,N0-Tetramethylamino)phenyl]-1,3-buta-
dione (100 mg, 0.4 mmol) (4d) and scandium(III) chloride (22 mg,
0.09 mmol) in 10 mL ofmethanol were treated with ammonia, overnight
precipitated crystals were collected by filtration and washed with a small
amount ofmethanol to yield 47 mg (67%) of9d as yellow crystals, M.p.
ꢀ
181 C. IR (KBr): ꢀ ¼ 2919 cmÀ1, 2875, 2849, 2795, 1554, 1512, 1373,
~
1061, 778, 427. UV/Vis (CH3CN): ꢁmax (lg ") ¼ 192 nm (4.584), 242
1
(4.932), 336 (4.618). H NMR: ꢂ ¼ 2.12 (s, 9H), 2.90 (s, 36H), 6.16 (t,
4J ¼ 2.2 Hz, 3H), 6.19 (s, 3H), 6.72 (d, 4J ¼ 2.2 Hz, 6H). 13C NMR:
ꢂ ¼ 27.6 (þ), 40.9 (þ), 99.9 (þ), 100.9 (þ), 102.4 (þ), 139.5 (Cquat),
151.4 (Cquat), 185.3 (Cquat), 192.6 (Cquat). MS (70 eV), m/z (%): 786
(100) [Mþ], 539 (54) [Mþ ÀC14H19N2O2].
Ethyl trans-{3-[2,5-(N,N,N0,N0-tetramethylamino)phenyl]}acrylate (6).
A solution of2,5-( N,N,N0,N0-tetramethylamino)benzaldehyde (520 mg,
2.7 mmol) (5) in ethyl acetate (10 mL) was added at 0ꢀC to sodium
(75 mg, 3.3 mmol) in ethyl acetate (10 mL), the reaction mixture was
refluxed for 5 h and then stirred overnight at room temp. Glacial acetic
acid (0.25 mL) was added, the solution was washed with water, dried over
Na2SO4 and the solvents were removed in vacuo. CC (PE/EA 7:3) ofthe
crude product gave 530 mg (74%) of 6 (Rf ¼ 0.66) as a yellow oil. IR
(KBr): ꢀ ¼ 3037 cmÀ1, 2979, 2826, 2786, 1711, 1505, 1168. UV/Vis
~
(CH3CN): ꢁmax (lg ") ¼ 204 nm (4.204), 268 (4.292), 398 (3.365).
3
1H NMR: ꢂ ¼ 1.34 (t, J ¼ 7.1 Hz, 3H), 2.66 (s, 6H,), 2.90 (s, 6H), 4.26
3
3
3
(q, J ¼ 7.1 Hz, 2H), 6.40 (d, J ¼ 16.1 Hz, 1H) 6.80 (d, J ¼ 8.2 Hz, 1H),
6.90 (s, 1H), 7.02 (d, 3J ¼ 8.2 Hz, 1H), 8.13 (d, 3J ¼ 16.1 Hz, 1H).
13C NMR: ꢂ ¼ 14.3 (þ), 41.6 (þ), 45.6 (þ), 60.2 (À), 111.7 (Cquat),
116.1 (þ), 117.5 (þ), 119.7 (þ), 129.3 (þ), 129.4 (þ),142.9 (Cquat),
143.0 (Cquat), 167.5 (Cquat). MS (70 eV), m/z (%): 262 (100) [Mþ], 247
(12) [Mþ ÀCH3]. C15H22N2O2: Calcd. C 68.67, H 8.45, N 10.68; found C
68.43, H 8.75, N 10.42.
Ethyl 3-[2,5-(N,N,N0,N0-tetramethylamino)phenyl]propionate (7). A
mixture ofethyl
trans-{3-[2,5-(N,N,N0,N0-tetramethylamino)phenyl]}
acrylate (500 mg, 1.9 mmol) (6) and 30 mg ofpalladium on charcoal
(10%) in 75 mL ofmethanol were pressurized with hydrogen (5 bar)
for 5 h at room temp. The reaction mixture was filtered through celite,
methanol was distilled off in vacuo and the crude product was purified by
CC (PE/EA 8:2) to give 500 mg (quantitative yield) of 7 (Rf ¼ 0.34) as a
yellow oil. IR (KBr): ꢀ ¼ 3029 cmÀ1, 2977, 2883, 2855, 1733, 1450, 1174,
~
944. UV/Vis (CH3CN): ꢁmax (lg ") ¼ 208 nm (4.399), 262 (4.159), 312
1
3
(3.391). H NMR: ꢂ ¼ 1.25 (t, J ¼ 7.1 Hz, 3H), 2.61 (s, 6H), 2.65 (m,
3
2H), 2.88 (s, 6H), 3.00 (m, 2H), 4.14 (q, J ¼ 7.1 Hz, 2H), 6.61 (m, 2H),

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Aryl-Substituted 1,3-Butadiones
975
7.07 (d, 3J ¼ 8.4 Hz, 1H). 13C NMR: ꢂ ¼ 14.2 (þ), 27.1 (À), 35.3 (À), 41.0
(þ), 45.8 (þ), 60.2 (À), 111.7 (þ), 114.3 (þ), 121.1 (þ), 136.9 (Cquat),
143.2 (Cquat), 147.6 (Cquat), 173.6 (Cquat). MS (70 eV), m/z (%): 264 (100)
[Mþ]. ÀC15H24N2O2: calcd. C 68.15, H 9.15, N 10.60; found C 67.92,
H 8.96, N 10.54.
6-[2,5-(N,N,N0,N0-Tetramethylamino)phenyl]-2,4-hexandione (8). To a
solution of N-isopropylidene cyclohexylamine (420 mg, 3 mmol) and
LDA (3 mmol) in THF (20 mL) at 0ꢀC was added ethyl 3-[2,5-
(N,N,N0,N0-tetramethylamino)phenyl]propionate (360 mg, 1.4 mmol, 7)
and the mixture was left overnight at room temp. Aqueous HCl
(10 mL, 2 M) was added, the solution was refluxed for 30 min, the pH
was then adjusted to neutral by addition ofsat. aqueous NaHCO
3
and ethyl acetate was added for dilution. The organic phase was sepa-
rated, washed with water, dried over Na2SO4 and the solvent was
removed in vacuo. CC (PE/EA 1:1) yielded 210 mg (54%) of 8
(Rf ¼ 0.46) as a yellow orange oil. IR (KBr): ꢀ ¼ 2934 cmÀ1, 2856, 2820,
~
2761, 1609, 1510, 941. UV/Vis (CH3CN): ꢁmax (lg ") ¼ 208 nm (4.391),
1
264 (4.295), 348 (2.705). H NMR: ꢂ ¼ 2.04 (s, 3H, enol), 2.21 (s, 3H,
keto), 2.61 (m, 16H, keto and enol), 2.88 (m, 16H, keto and enol), 3.57
(s, 2H, keto), 5.53 (s, 1H, enol), 6.58 (m, 4H, keto and enol), 7.07 (m, 2H,
keto and enol), 15.52 (s, 1H, enol). 13C NMR: ꢂ ¼ 24.8 (þ), 26.1 (À), 27.5
(À), 39.4 (À), 41.0 (þ), 44.9 (À), 45.9 (þ), 57.8 (À), 99.8 (þ), 111.7 (þ),
114.2 (þ), 121.0 (þ), 136.9 (Cquat), 143.1 (Cquat), 147.6 (Cquat), 190.9
(Cquat), 194.2 (Cquat). MS (70 eV), m/z (%): 276 (100) [Mþ].
ÀC16H24N2O2: calcd. C 69.53, H 8.75, N 10.14; found C 69.65, H 8.72,
N 10.10.
ACKNOWLEDGMENT
This work was supported by the Volkswagen foundation
(priority research area electron transfer). HZ thanks the state
ofNiedersachsen, Germany, of r a graduate stipend.
REFERENCES
1. Niemann, C.; Benson, A.A.; Mead, J.F. J. Am. Chem. Soc. 1941, 63,
2204–2208.
2. Esters ofthe corresponding aminobenzoic acids were synthesized
by alkylation with methyl or ethyl iodide in the presence of
potassium carbonate.

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976
Konig
3. a) Norton, D.G.; Haury, V.E.; Davis, F.C.; Mitchell, L.J.; Ballard,
S.A. J. Org. Chem. 1954, 19, 1054–1066; b) Smith, J.K.; Bergbreiter,
D.E.; Newcomb, M. J. Am. Chem. Soc. 1983, 105, 4396–4440.
4. Compound 4a has been previously synthesized: Popic, V.V.;
Korneev, S.M.; Nikolaev, V.A.; Korobitsyna, I.K. Synthesis 1991,
195–198.
5. Weil, L. Monatsh. Chem. 1908, 29, 895–908.
6. Ungnade, H.E. J. Am. Chem. Soc. 1953, 75, 432–434.
7. Atik, S.S.; Thomas, J.K. J. Am. Chem. Soc. 1981, 103, 3550–3555.
8. Bock, C.R.; Connor, J.A.; Guitierez, A.R.; Meyer, T.J.; Whitten,
D.G.; Sullivan, B.P.; Nagle, J.K. J. Am. Chem. Soc. 1979, 101,
4815–4824.
9. Saito, T.; Matsuura, T.; Inoue, K. J. Am. Chem. Soc. 1983, 105,
3200–3206.
10. Lyle, S.J.; Witts, A.D. Inorg. Chim. Acta 1971, 481–484.
11. All potentials vs Fc/FCþ. experimental conditions are identical to
the conditions given in Table 1.
Received in the UK February 17, 2002