4-Cyano-6,7-dimethoxycarbostyrils with solvent- and pH-independent high fluorescence quantum yields and emission maxima

Article abstract of DOI:10.1002/ejoc.200700855

Highly fluorescent and stable 6,7-dimethoxy-2-oxoquinoline-4-carbonitriles (11) were synthesized starting from appropriate 4-hydroxyquinolones 3 via reactive 4-chloroquinolones 8 by using toluenesulfinates as catalysts. In contrast to the well-described 4-trifluoromethyl-substituted analogues 18, N-substituted derivatives 11 fluoresce in water, polar, and apolar solvents in a narrow 430-440-nm window with almost constant quantum yield of 0.5. Equal excitation is possible in the broad double maximum between 385 and 410 nm yielding identical data between pH 1 and 11. These properties could lead to a broadly usable fluorescence standard. N-Alkylation with bromoacetate yields ester 13 in good yields. Reactive succinimidoyl (OSu) ester 15 was prepared by saponification to acid 14. With amino acids or peptides, linking to labeled derivatives 17 was achieved under mild conditions in slightly basic aqueous media. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Full text of DOI:10.1002/ejoc.200700855

FULL PAPER
DOI: 10.1002/ejoc.200700855
4-Cyano-6,7-dimethoxycarbostyrils with Solvent- and pH-Independent High
Fluorescence Quantum Yields and Emission Maxima
[a]
[a]
[a]
[a]
ˇ
ˇ
ˇ
Appasaheb B. Ahvale, Hana Prokopcová, Jana Sefcovicová, Waltraud Steinschifter,
Anna E. Täubl,[a] Georg Uray,[a] and Wolfgang Stadlbauer*[a]
Keywords: Quinolones / Carbostyrils / Fluorescent probes / Fluorescence labeling / Amino acids / Peptides
Highly fluorescent and stable 6,7-dimethoxy-2-oxoquinoline-
4-carbonitriles (11) were synthesized starting from appropri-
ate 4-hydroxyquinolones 3 via reactive 4-chloroquinolones 8
by using toluenesulfinates as catalysts. In contrast to the
well-described 4-trifluoromethyl-substituted analogues 18,
N-substituted derivatives 11 fluoresce in water, polar, and
apolar solvents in a narrow 430–440-nm window with almost
constant quantum yield of 0.5. Equal excitation is possible in
the broad double maximum between 385 and 410 nm yield-
ing identical data between pH 1 and 11. These properties
could lead to a broadly usable fluorescence standard. N-Al-
kylation with bromoacetate yields ester 13 in good yields.
Reactive succinimidoyl (OSu) ester 15 was prepared by sa-
ponification to acid 14. With amino acids or peptides, linking
to labeled derivatives 17 was achieved under mild conditions
in slightly basic aqueous media.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
Introduction
Results and Discussion
Luminescence properties of most carbostyrils [quinolin-
2(1H)-ones] have the disadvantage of shorter absorption
and emission wavelengths relative to coumarins.[1] In con-
trast, carbostyrils have, in general, the important advantage
that they are highly stable against chemicals (relative to
coumarins[2] or fluorescein-type dyes), thermal and photo-
chemical stress (e.g., relative to azodyes), and they are in-
sensitive to oxygen quenching (e.g., relative to 1,10-phenan-
throline complexes). All these properties make them very
useful as, for example, fluorescence markers for biological
samples. Recently, we reported systematic studies about the
fluorescence properties of differently substituted carbosty-
rils[3] which revealed that suitable structure elements shifted
the wavelengths up to 440 and 540 nm for the absorption
and emission maxima, respectively.
We were able to show that 6,7-dimethoxy-4-trifluoro-
methylcarbostyrils with linking groups either at the N-1 or
O-6 position[4] reveal very good photophysical properties,
such as an absorption maximum close to the visible region
(λՆ370 nm), large Stokes’ shifts (λF Ն440 nm), sufficiently
high extinction coefficients (ε about 104), and high fluores-
cence quantum yields (ΦF up to 0.3). The disadvantage of
dimethoxy derivatives in terms of slightly shorter absorp-
tion and emission wavelengths compared with aminocarbo-
styrils is counterbalanced by advantages such as largely pH-
independent photophysical properties and high chemical
stability.
Synthesis
Searching for new carbostyril substituents with suitable
electronic properties and high photophysical stability, we
extended the successful push–pull concept[3] and investi-
gated the properties of 4-cyanocarbostyrils 11. We had syn-
thesized some 4-cyanoquinoline-2-ones earlier in another
project,[5] but they were not further synthetically used be-
cause of their low reactivity, properties that now make them
in the push–pull modification very useful as fluorescent
probes, as they proved to be chemically and photophysically
highly stable.
In the literature there is no useful synthesis for 4-cyano-
carbostyrils described. So we started the reaction sequence
to desired 4-cyanocarbostyrils 11 from 4-hydroxycarbosty-
rils of type 3. The synthesis of 3-substituted derivatives 3a–
d was easily achieved by using the general procedure de-
scribed in refs.[6,7] starting from appropriately substituted
anilines 1a,b and alkyl- or aryl-substituted malonates 2a–c.
For 3-unsubstituted derivatives 3e,f this reaction did not
work and so we applied two known approaches: either di-
rectly with malonic acid and phosphoryl chloride as a con-
densation agent[7] or by the three-step pyrono route.[7–9] The
direct route offers the advantage of a one-step-reaction, but
phosphoryl chloride, which is used as the condensation
agent, can react in a subsequent step easily with the 4-hy-
droxy group and the 2-oxo group of the primarily formed
hydroxycarbostyril 3. To avoid such side reactions, an excess
amount of aniline 1 and malonic acid (2d) had to be used,
which gave desired carbostyrils 3e,f in moderate-to-good
yields.
[a] Department of Chemistry, Organic and Bioorganic Chemistry,
Karl-Franzens University of Graz,
Heinrichstrasse 28, 8010 Graz, Austria
E-mail: wolfgang.stadlbauer@uni-graz.at
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W. Stadlbauer et al.
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The pyrono route to 3-unsubstituted carbostyrils often with sodium or potassium cyanide in suitable organic sol-
gives better results and purer compounds[7–9] but needs a vents in the presence of crown ethers failed in most cases.
three-step reaction sequence. The first step involves the for- Only with rather reactive dichloroquinolines such as 7c,d
mation of pyranoquinolone 4 from a 2:1 reaction of diethyl- did a reaction take place; however, both of the chloro atoms
malonate (2e) with anilines 1, followed by a basic ring open- were substituted by cyano groups to form dinitriles 9
ing of the pyrone to 3-acetylcarbostyril 5 and then removal (Scheme 2). All attempts to find either conditions for a re-
of the acetyl group by ipso-substitution with 90% sulfuric gioselective monosubstitution or removal of the undesired
acid. However, in our case the reaction sequence failed in cyano group in the 2-position failed. The introduction of
the third step: in this reaction not only the acetyl group was cyano groups into the corresponding 4-chlorocarbostyrils
cleaved, but also double demethoxylation to afford 4,6,7- by these methods failed. Attempts to utilize the Rosen-
trihydroxycarbostyril 3g took place (Scheme 1).
mund–Braun aromatic cyanation[11] with copper(I) cyanide
in high-boiling solvents gave a mixture of fluorescent com-
pounds, but separation attempts with chromatographic
methods failed.
Scheme 1.
The next step in the reaction sequence to 4-cyanocarbo-
styrils was the introduction of a reactive leaving group in
the 4-position. Experiments with 4-tosylates 6a,b revealed
that no reaction took place. So we directed our attention to
the reactions of 2,4-dichloroquinolines 7 and 4-chloro-
carbostyrils 8, which were prepared by reaction of the cor-
responding hydroxycarbostyrils 3 with an excess amount of
phosphoryl chloride. 1-Unsubstituted 4-hydroxycarbosty-
rils (such as 3b,f,h,i) gave 2,4-dichloroquinolines 7a–d,
which could be hydrolyzed regioselectively to afford 4-chlo-
rocarbostyrils 8a,c,g,h. The best reaction conditions were
found with 70% methanesulfonic acid in ethanol; alkaline
hydrolysis gave significantly lower yields. The reactions of
1-substituted 4-hydroxycarbostyrils such as 3a with phos-
phoryl chloride directly gave 4-chlorocarbostyrils 8b.
Scheme 2.
Another method, however, which was described re-
cently,[12] allowed us to introduce the nitrile group at the 4-
When we applied our findings from studies in the nucleo- position of chlorocarbostyrils 8 under rather mild condi-
philic substitution of quinolines and quinolones,[8,10] we tions of 120 °C by using sodium or lithium p-toluenesulfin-
found that the introduction of nitrile groups by reaction ate as intermediates in dimethylformamide as the solvent.
564
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Eur. J. Org. Chem. 2008, 563–571

Carbostyrils with High Fluorescence Quantum Yields and Emission Maxima
Only the reactions of 4-chlorocarbostyrils of type 8 with aqueous–ethanolic sodium hydroxide gave quinolinyl-1-ace-
3-alkyl- or 3-alkoxy-substituents in the 3-position did not tic acid 14 in excellent yield, which was subsequently trans-
proceed. In ref.[12] the intermediate sulfinates were not iso- formed into reactive succinimidoyl active ester 15 (OSu es-
lated. We decided to determine if isolation of the intermedi- ter) in dry tetrahydrofuran containing diisopropylcarbodi-
ate and a two-step reaction could produce better results; imide as a water scavenger. Ester 15 is stable in aqueous
thus, as an example, we prepared sulfinate 10 (Scheme 3) solution, but highly reactive towards amino groups.[13]
from 4-chlorocarbostyril 8c, which was then treated with
The reaction of OSu ester 15 with phenylalanine (16a)
potassium cyanide at 70 °C to afford 4-cyanocarbostyril proceeded under biochemical conditions (aqueous medium,
11a. The yields and purity show that there is no advantage 15–20 °C) by using aqueous dimethyl sulfoxide as the sol-
for the two-step reaction. So, we synthesized 11 in one step vent and an aqueous pH 7 buffer as the base; this reaction
in good-to-excellent yields (65–97%), with the exception of afforded amino-linked carbostyril 17a in 70% yield. In the
11b (16%).
same manner, the reaction of tripeptide glycyl-glycyl-glycine
(16b) afforded amino-linked carbostyril 17b in 55% yield
(Scheme 4).
Scheme 3.
Because the yields of N-methyl carbostyrils (e.g., 3e, 11b)
were rather low, we also checked the possibility of later N-
methylation of 11a to compare it with the use of N-methyl
derivatives in earlier stages. Methylation with iodomethane
in acetonitrile gave, as expected, in 75% yield a mixture of
O-methylated and N-methylated products 12a and 13a (ra-
tio 1:4), respectively, which was separated by dry flash
chromatography.[18] So all routes with N-methyl derivatives
were somewhat restricted in terms of yield; together with
some disadvantages in the construction of linkers at O-6 of
the carbostyrils,[4b] this route was not further completed.
Recently, we showed that the introduction of linker
groups attached at N-1 of 4-trifluoromethylcarbostyrils
hardly influenced the photophysical properties regarding
wavelengths and Stokes’ shifts; however, water as the sol-
vent lowered the fluorescence quantum yields by about
50%[4a]
Scheme 4.
Electronic Spectra
When we used bromoacetate[4a] in the N-alkylation reac-
tion in a binary mixture of sodium hydroxide/water and
Figure 1 shows the normalized excitation and emission
dichloromethane in the presence of dibenzo-18-crown-6, 4- spectra of N-methyl derivative 13a and the previously pub-
chlorocarbostyril 11a afforded a mixture of O- and N-alkyl- lished[4b] trifluoromethyl analogue 18 in water. Both the ex-
ated products, 12b and 13b, respectively, in 90% yield in a citation and the emission maxima of 13a are redshifted sig-
1:5 ratio; the isomers were separated by dry flash nificantly. Significantly different are the fluorescence quan-
chromatography. Hydrolysis of quinolinyl-1-acetate 13b in tum yields: whereas in DMSO they are about equal (about
Eur. J. Org. Chem. 2008, 563–571
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W. Stadlbauer et al.
FULL PAPER
0.5), 18 and similar compounds are quenched in water sig- be obtained by an additional three-step reaction in good
nificantly to give a quantum yield of 0.16. A solvent-inde- yields.
pendent quantum yield as shown for cyanocarbostyrils such
Absorption spectra of the new N-linked 6,7-dimethoxy-
as 13a is at least new in the class of carbostyrils; therefore, 4-cyanocarbostyrils 13b, 14, and 17a,b are all very similar
we measured the fluorescence spectra in two additional sol- with broad double maxima between 385 and 410 nm in po-
vents: dichloromethane and ethanol. No quenching by oxy- lar and apolar solvents. In water, a maximum redshift of
gen was observed, as the intensities did not change after about 20 nm is observed. The extinction coefficients are
degassing with argon.
high with values between 10000 and 13000. Interestingly,
and in contrast to the 4-trifluoromethyl analogues, the
emission values range between 430 and 440 nm in all sol-
vents, which therefore shows varying Stokes’ shifts. Most
important of all, fluorescence quantum yields are almost
independent of solvents and pH and high values of around
0.5 are obtained. These findings reveal that 4-cyanocarbo-
styrils substituted at the 6- and 7-positions with electron-
donating substituents will be very useful new fluorophores
that are well suited as fluorescence standards.
Experimental Section
Figure 1. Excitation and emission spectra of 4-cyano- vs. 4-trifluor-
omethylcarbostyrils 13a and 18 in water.
General Remarks: Melting points were determined with a Stuart
SMP3 melting point apparatus in open capillary tubes. 1H and 13
C
NMR spectra were recorded with a Bruker AMX 360 instrument
(360 or 90 MHz) or a Bruker Avance DRX 500 instrument (500 or
125 MHz). Chemical shifts are given in ppm (δ) from the internal
TMS standard. IR spectra were recorded with a Mattson Galaxy
Series FTIR 7020 instrument with potassium bromide discs. Ele-
mental analyses were performed at the Microanalytical Laboratory
of the University of Vienna, Austria. Mass spectra were obtained
with a HP 1100 LC/MSD mass spectral instrument (positive or
negative APCI ion source, 50–200 V, nitrogen). UV/Vis spectra
were recorded with a Shimadzu UV/Vis scanning spectrophotome-
ter UV-2101 PC; concentration: 1ϫ10–4 . Excitation and emission
spectra were recorded with a Shimadzu RF-5001 PC spectrofluoro-
meter (150-W Xe lamp, 6 selectable slits: 1.5, 3, 5, 10, 15, 20 nm,
R452–01 photomultiplier; monochromator: ion-blazed holographic
concave grating F/2.5); concentration: 1ϫ10–4 . Determination of
quantum yields: emission signals were set in relation to the known
area of the emission signal of quinine sulfate at pH 1. Corrections
were made for other solvents by using the factor (nwater/nsolvent).[2]
Analytical HPLC was performed with a Shimadzu LC 20 system
equipped with a diode array detector (215 and 254 nm) with a
Pathfinder AS reversed phase (4.6ϫ150 mm, 5 µm) column, run-
ning an acetonitrile/water gradient (30–100% acetonitrile).
The data for 4-cyanocarbostyril 13a in Table 1 show an
almost complete independence of solvent influences for
emission maxima and fluorescence quantum yield. All
other N–CH2–CO–R derivatives 13b, 14, and 17a,b exhibit
very similar electronic spectra; however, quantum yields of
the latter are about 0.55 in water and 0.45Ϯ0.05 in DMSO.
The use of this type of labeling fluorophore in biological
samples is therefore superior to the trifluoromethyl variants
similar to 18, which are equally linked at N-1.[4a]
Table 1. Independence of solvent influences for emission maxima
and fluorescence quantum yield of N-methyl derivative 13a.
Solvent
UV[a] λmax
[nm]
ε
exc[a] λmax em λmax
Φ
[–1cm–1
]
[nm]
[nm]
Dichloromethane
DMSO
392
390
385
380
13000
12400
13100
11000
400
400
390
385
430
436
432
432
0.48
0.61
0.51
0.50
All reactions were monitored by thin-layer chromatography (TLC)
on 0.2-mm silica gel F-254 (Merck) plates by using UV light (254
and 366 nm) for detection. Common reagent-grade chemicals were
either commercially available and were used without further purifi-
cation or prepared by standard literature procedures. All optical
measurements were performed by using analytical-grade solvents.
Ethanol
Water[b]
[a] Maximum at the center of the broad signal or at the center
of the sometimes visible almost equally intense double peak (see
Experimental Section). [b] Identical values between pH = 1 and pH
= 11.
4-Hydroxy-6,7-dimethoxy-1-methyl-3-phenylquinolin-2(1H)-one
(3a): A mixture of 3,4-dimethoxy-N-methylbenzenamine[4b] (1b;
3.72 g, 22 mmol) and diethyl phenylmalonate (2a; 5.24 g, 22 mmol)
in diphenyl ether (25 mL) was heated under reflux for 3 h. During
this time, ethanol was liberated (2.1 mL). The mixture was cooled
to 20 °C, diluted with cyclohexane (50 mL), and the formed pre-
cipitate was filtered by suction. The solid was dissolved in aqueous
NaOH (0.5 , 80 mL), and the byproducts were extracted with tol-
uene (50 mL) and decolorized with charcoal. The product was pre-
Conclusions
The synthesis of highly fluorescent 6,7-dimethoxy-4-cya-
nocarbostyril 11a can be achieved in a three-step reaction
with an overall yield of about 30%. Linkers can be intro-
duced easily at N-1, and labeled proteins such as 17b can cipitated upon acidification with HCl (2 ), filtered by suction, and
566 Eur. J. Org. Chem. 2008, 563–571
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Carbostyrils with High Fluorescence Quantum Yields and Emission Maxima
dried at 40 °C under reduced pressure to afford 4.93 g (71% yield)
washed with water, and dried at 40 °C under reduced pressure to
afford 7.10 g (79 % yield) of pale-green prisms. M.p. Ͼ320 °C
2820 (br., m), 1625 (sh), 1610 (s) cm–1. H NMR (360 MHz, [D6]- (DMF/ethanol); ref.[14] m.p. Ͼ320 °C. IR (KBr): ν = 3570–3250
of colorless prisms. M.p. 264–267 °C (DMF). IR (KBr): ν = 3180–
˜
1
˜
DMSO): δ = 3.61 (s, 3 H, NMe), 3.82 and 3.89 (2 s, 2ϫ3 H, 6-
and 7-OMe), 6.95 (s, 1 H, 8-H), 7.28–7.33 (m, 5 H, PhH), 7.45 (s,
1 H, 5-H), 9.80 (s, 1 H, OH) ppm. C18H17NO4 (311.34): calcd. C
69.44, H 5.50, N 4.50; found C 69.25, H 5.78, N 4.81.
(br., s), 2920 (s), 1685 (s), 1641 (sh), 1617 (m), 1605 (sh), 1518 (s)
cm–1. 1H NMR (360 MHz, [D6]DMSO): δ = 3.76 and 3.78 (2 s,
2ϫ3 H, 6- and 7-OMe), 5.61 (s, 1 H, 3-H), 6.81 (s, 1 H, 8-H), 7.15
(s, 1 H, 5-H), 11.00 (s, 1 H, NH) ppm. MS: m/z (%) = 222 (8) [M
+ 1], 221 (100) [M]. C11H11NO4 (221.21): calcd. C 59.73, H 5.01,
N 6.33; found C 59.55, H 4.87, N 6.68.
4-Hydroxy-6,7-dimethoxy-3-phenylquinolin-2(1H)-one (3b): A mix-
ture of aniline 1a (3.43 g, 22 mmol) and diethyl phenylmalonate
(2a; 5.24 g, 22 mmol) was brought to reaction (24 h) and worked
up as described for 3a to afford 5.55 g (85% yield) of colorless
4,6,7-Trihydroxy-1-methylquinolin-2(1H)-one (3g): 3-Acetylquin-
olone 5 (1.39 g, 5 mmol) was dissolved in 90% H2SO4 (4 mL) and
heated for 15 min at 140 °C. Then, the solution was poured into
ice/water (100 mL). The obtained suspension was kept for 24 h at
20 °C, and it was then filtered, washed with water (250 mL), and
dried at 40 °C under reduced pressure to afford 0.74 g (71% yield)
of light-brownish prisms. M.p. 310–311 °C (ethanol/water). IR
prisms. M.p. 340–343 °C (DMF). IR (KBr): ν = 3120–2600 (br.,
˜
1
m), 1640 (s), 1610 (s) cm–1. H NMR (360 MHz, [D6]DMSO): δ =
3.82 and 3.86 (2 s, 2ϫ3 H, 6- and 7-OMe), 6.85 (s, 1 H, 8-H),
7.30–7.35 (m, 5 H, PhH), 7.39 (s, 1 H, 5-H), 9.81 (s, 1 H, OH),
11.20 (s, 1 H, NH) ppm. C17H15NO4 (297.31): calcd. C 68.68, H
5.09, N 4.71; found C 68.96, H 4.85, N 4.58.
(KBr): ν = 3400–2800 (br., s), 1621 (s), 1590 (m), 1561 (s), 1526
˜
(m) cm–1 1H NMR (360 MHz, [D6]DMSO): δ = 3.40 (s, 3 H,
.
3-Benzyl-4-hydroxy-6,7-dimethoxyquinolin-2(1H)-one (3c): A mix-
ture of aniline 1a (3.43 g, 22 mmol) and diethyl benzylmalonate
(2b; 5.50 g, 22 mmol) was brought to reaction (48 h) and worked
up as described for 3a to afford 4.24 g (62% yield) of pale-brownish
NMe), 5.65 (s, 1 H, 3-H), 6.77 (s, 1 H, 8-H), 7.19 (s, 1 H, 5-H),
9.21 (s, 1 H, OH), 9.79 (s, 1 H, OH), 10.90 (s, 1 H, NH) ppm. MS:
m/z (%) = 208 (10) [M + 1], 207 (100) [M], 192 (8). C10H9NO4
(207.19): calcd. C 57.97, H 4.38, N 6.76; found C 58.18, H 4.13, N
6.44.
prisms. M.p. 207–210 °C (DMF). IR (KBr): ν = 3150–2850 (br.,
˜
1
m), 1645 (s), 1615 (s) cm–1. H NMR (360 MHz, [D6]DMSO): δ =
3.83 and 3.87 (2 s, 2ϫ3 H, 6- and 7-OMe), 3.99 (s, 2 H, benzyl-
CH2), 6.83 (s, 1 H, 8-H), 7.29–7.35 (m, 5 H, PhH), 7.40 (s, 1 H, 5-
H), 9.79 (s, 1 H, OH), 11.23 (s, 1 H, NH) ppm. C18H17NO4
(311.34): calcd. C 69.44, H 5.50, N 4.50; found C 69.71, H 5.24, N
4.82.
4-Hydroxy-8,9-dimethoxy-6-methyl-2H-pyrano[3,2-c]quinoline-2,5-
(6H)-dione (4): A mixture of 3,4-dimethoxy-N-methylbenzen-
amine[4b] (1b; 3.34 g, 20 mmol) and diethyl malonate (2e; 6.41 g,
40 mmol) in diphenyl ether (20 mL) was heated under reflux in a
distillation apparatus equipped with a 20-cm Vigreux column. Dur-
ing 3–4 h, the liberated ethanol was distilled until no more ethanol
was formed (about 3.6 mL). The reaction mixture was cooled to
100 °C and treated with dioxane (20 mL). The precipitate was fil-
tered by suction, washed with dioxane (20 mL) to remove diphenyl
ether, and dried at 40 °C under reduced pressure to afford 4.48 g
(74% yield) of yellow prisms. M.p. 315–316 °C (DMF). IR (KBr):
3-Ethyl-4-hydroxy-6,7-dimethoxyquinolin-2(1H)-one (3d): A mix-
ture of aniline 1a (3.43 g, 22 mmol) and diethyl ethylmalonate (2c;
4.03 g, 22 mmol) was brought to reaction (48 h) and worked up as
described for 3a to afford 0.49 g (9 %) of pale green-brownish
prisms. M.p. 229–234 °C (DMF). IR (KBr): ν = 3160–2890 (br.,
˜
1
m), 1650 (s), 1610 (s) cm–1. H NMR (360 MHz, [D6]DMSO): δ =
ν = 3550–3450 (br., s), 1739 (s), 1677 (m), 1622 (m), 1576 (m), 1520
˜
1.28 (t, J = 7.1 Hz, 3 H, ethyl-CH3), 2.36 (q, J = 7.1 Hz, 2 H, ethyl-
CH2), 3.85 and 3.88 (2 s, 2ϫ3 H, 6- and 7-OMe), 6.79 (s, 1 H, 8-
H), 7.40 (s, 1 H, 5-H), 9.78 (s, 1 H, OH) ppm. C13H15NO4 (249.27):
calcd. C 62.64, H 6.07, N 5.62; found C 62.38, H 5.87, N 5.91.
(s) cm–1. 1H NMR (360 MHz, CF3COOD): δ = 4.25 (s, 3 H, NMe),
4.43 and 4.45 (2 s, 2ϫ3 H, 8- and 9-OMe), 6.25 (s, 1 H, 3-H), 7.51
(s, 1 H, 10-H), 8.16 (s, 1 H, 7-H) ppm. MS: m/z (%) = 304 (24) [M
+ 1], 303 (100) [M], 289 (55), 259 (100). C15H13NO6 (303.27): calcd.
C 59.41, H 4.32, N 4.62; found C 59.11, H 4.50, N 4.79.
4-Hydroxy-6,7-dimethoxy-1-methylquinolin-2(1H)-one (3e): A mix-
ture of 3,4-dimethoxy-N-methylbenzenamine[4b] (1b; 4.22 g,
25 mmol) and dry malonic acid (2d; 2.57 g, 25 mmol) in phospho-
ryl chloride (2.65 mL, 17 mmol) was heated to 110 °C until strong
foaming decreased and the mixture solidified (about 30 min). The
mixture was suspended in water and stirred for 24 h until complete
crystallization had taken place. The solid was dissolved in aqueous
NaOH (0.5 , 100 mL), decolorized with charcoal, filtered, and
acidified with HCl (6 ). The precipitate was filtered by suction,
washed with water (250 mL), and dried at 40 °C under reduced
pressure to afford 1.63 g (41% yield) of pale-brown microprisms.
3-Acetyl-4-hydroxy-6,7-dimethoxy-1-methylquinolin-2(1H)-one (5):
A mixture of pyranoquinoline 4 (3.03 g, 10 mmol) and aqueous
NaOH (1 , 3 mL) in 1,2-dihydroxyethane (30 mL) was heated to
gentle boiling for 1 h and then poured into ice/water (100 mL). The
obtained solution was slowly acidified with concentrated HCl (at-
tention: strong foaming!). The precipitate was filtered by suction,
washed with water (2ϫ250 mL), and dried at 40 °C under reduced
pressure to afford 1.97 g (71% yield) of yellow prisms. M.p. 238–
239 °C (toluene). IR (KBr): ν = 2939 (w), 1653 (s), 1594 (s), 1563
˜
1
(s), 1520 (s) cm–1. H NMR (360 MHz, CDCl3): δ = 2.82 (s, 3 H,
M.p. 262.4 °C (DMF). IR (KBr): ν = 3480–3120 (br., m), 2950–
˜
2820 (m), 1665 (s) cm–1. 1H NMR (360 MHz, [D6]DMSO): δ =
3.61 (s, NMe), 3.76 and 3.78 (2 s, 2ϫ3 H, 6- and 7-OMe), 5.60 (s,
1 H, 3-H), 6.80 (s, 1 H, 8-H), 7.15 (s, 1 H, 5-H), 11.05 (s, 1 H, NH)
ppm. C12H13NO4 (235.24): calcd. C 61.27, H 5.57, N 5.95; found
C 61.62, H 5.88, N 5.57.
acetyl-Me), 3.66 (s, 3 H, NMe), 3.98 and 4.05 (2 s, 2ϫ3 H, 8- and
9-OMe), 6.69 (s, 1 H, 8-H), 7.55 (s, 1 H, 5-H) ppm. MS: m/z (%)
= 278 (14) [M + 1], 277 (100) [M], 262 (43). C14H15NO5 (277.28):
calcd. C 60.65, H 5.45, N 5.05; found C 60.83, H 5.48, N 4.95.
6,7-Dimethoxy-2-oxo-3-phenyl-1,2-dihydroquinolin-4-yl 4-Methyl-
benzenesulfonate (6a): A mixture of hydroxyquinolone 3b (9.78 g,
33 mmol), p-tosyl chloride (9.44 g, 49.5 mmol), and 4-(N,N-di-
methyl)aminopyridine (200 mg) in dry pyridine (200 mL) was
stirred at 20 °C for 24 h. Then the mixture was poured into ice/
water (500 mL), and the solid was filtered by suction, washed sub-
sequently with water (200 mL) and ethanol (50 mL), and then crys-
tallized from DMF to afford 14.7 g (99% yield) of colorless prisms.
4-Hydroxy-6,7-dimethoxyquinolin-2(1H)-one (3f): A mixture of ani-
line 1a (6.12 g, 40 mmol) and dry malonic acid (4.38 g, 42 mmol)
in phosphoryl chloride (6.2 g, 40 mmol) was heated at 50 °C for
2 h, then the temperature was raised slowly up to 90 °C and kept
there for 30 min. The obtained residue was dissolved in NaOH
solution (0.5 , 100 mL) and acidified with concentrated HCl to
pH 2–3. A light-green precipitate was formed, which was filtered,
Eur. J. Org. Chem. 2008, 563–571
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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567

W. Stadlbauer et al.
FULL PAPER
M.p. Ͼ310 °C (dec.) (DMF). IR (KBr): ν = 3100–2850 (br., m),
yield) of yellowish prisms. M.p. 171–176 °C (ethanol/water). IR
˜
1660 (sh), 1650 (s), 1635 (s), 1615 (m), 1595 (w), 1575 (w) cm–1. 1H (KBr): ν = 3450–3250 (br., w), 2960 (w), 1635 (m), 1610 (s) cm–1.
˜
NMR (360 MHz, CF3COOH): δ = 2.23 (s, Me), 3.91 and 3.96 (2
s, 2 ϫ3 H, 6- and 7-OMe), 6.99 (s, 1 H, 8-H), 7.11–7.17 (m, 9 H,
5 PhH, 4 TosH), 7.59 (s, 1 H, 5-H) ppm. C24H21NO6S (451,50):
calcd. C 63.85, H 4.69, N 3.10; found C 63.67, H 4.58, N 3.24.
1H NMR (360 MHz, [D6]DMSO): δ = 4.09 and 4.22 (2 s, 2ϫ3 H,
6- and 7-OMe), 4.66 (s, 3 H, NMe), 7.29–7.31 (m, 1 H, 8-H), 7.37–
7.44 (m, 2 H, PhH), 7.58–7.64 (m, 2 H, PhH), 7.72 (s, 1 H, PhH),
7.84 (s, 1 H, 5-H) ppm. C18H16ClNO3 (329.79): calcd. C 65.56, H
4.89, N 4.25; found C 65.22, H 4.97, N 4.01.
2-Oxo-1,2-dihydroquinolin-4-yl 4-Methylbenzenesulfonate (6b): Hy-
droxyquinolone 3j (3.67 g, 23 mmol), p-tosyl chloride (5.69 g,
30 mmol), and 4-(N,N-dimethyl)aminopyridine (200 mg) in dry
pyridine (200 mL) were brought to reaction and worked up as de-
scribed for 6a to afford 6.05 g (84% yield) of colorless prisms. M.p.
4-Chloro-6,7-dimethoxyquinolin-2(1H)-one (8c): A solution of
dichloroquinoline 7b (5.16 g, 20 mmol), 70% CH3SO3H (9.60 g,
100 mmol) and ethanol (80 mL) was heated under reflux for 28 h.
After cooling, the mixture was poured into ice/water (150 mL) and
brought to pH = 4–6 with aqueous NaOH (2 ). The obtained
solid was filtered by suction, washed with water (150 mL), dried at
40 °C under reduced pressure, and crystallized from ethanol to af-
ford 2.63 g (55% yield) of dark-brownish prisms. M.p. 258–259 °C
237–238 °C (ethanol). IR (KBr): ν = 1650 (w), 1610 (w), 1510 (w)
˜
cm–1. 1H NMR (360 MHz, [D6]DMSO): δ = 2.40 (s, 3 H, Me), 7.21
(d, J = 7.0 Hz, 1 H, 8-H), 7.46 (t, J = 7.0 Hz, 1 H, Aryl-H), 7.65
(t, J = 7.0 Hz, 1 H, Aryl-H), 7.85 (dd, J = 7.0, 1.5 Hz, 1 H, 5-H),
12.30 (s, 1 H, NH) ppm. C16H13NO4S (315.35): calcd. C 60.94, H
4.16, N 4.44; found C 61.33, H 4.28, N 4.46.
(ethanol). IR (KBr): ν = 3403 (m), 2957 (w), 2929 (m), 2909 (sh),
˜
2853 (w), 1657 (s), 1624 (m), 1606 (w), 1545 (w), 1513 (s) cm–1. 1H
NMR (360 MHz, [D6]DMSO): δ = 3.82 and 3.83 (2 s, 2ϫ3 H, 6-
and 7-OMe), 6.60 (s, 1 H, 3-H), 6.90 (s, 1 H, 8-H), 7.17 (s, 1 H, 5-
H), 11.82 (s, 1 H, NH) ppm. MS: m/z (%) = 241 (23) [M + 2], 240
(12) [M + 1], 239 (100) [M], 204 (100) [M – 35]. C11H10ClNO3
(239.66): calcd. C 55.13, H 4.21, N 5.84; found C 55.49, H 4.53, N
5.45.
2,4-Dichloro-6,7-dimethoxy-3-phenylquinoline (7a): A mixture of hy-
droxyquinolone 3b (8.72 g, 29 mmol) and phosphoryl chloride
(50 mL) was heated for 1 h under reflux. The excess amount of
phosphoryl chloride was removed in vacuo, and the residue was
poured into ice/water (300 mL) and brought to pH = 4–6 with
aqueous NaOH (5 ). The precipitate was washed with water
(200 mL) and filtered by suction to afford 5.13 g (53% yield) of
4-Chloro-3-phenylquinolin-2(1H)-one (8g): A solution of 2,4-
dichloro-3-phenylquinoline[10a] (7c; 2.74 g, 10 mmol), 70 %
CH3SO3H (4.80 g, 50 mmol), and ethanol (30 mL) was brought to
reaction (40 h, 60 °C) and worked up as described for 8c to afford
2.42 g (89% yield) of colorless prisms. M.p. 252–254 °C (ethanol).
colorless prisms. M.p. 285–290 °C (ethanol). IR (KBr): ν = 3050–
˜
2850 (br., w), 1640 (m), 1615 (m), 1555 (w), 1510 (sh), 1500 (s)
cm–1. 1H NMR (360 MHz, [D6]DMSO): δ = 3.80 and 3.96 (2 s,
2ϫ3 H, 6- and 7-OMe), 7.37 (m, 1 H, ArH), 7.39 (m, 1 H, ArH),
7.47 (m, 1 H, ArH), 7.49 (m, 1 H, ArH), 7.51 (m, 1 H, ArH), 7.53
(m, 1 H, ArH), 7.55 (s, 1 H, ArH) ppm. C17H13Cl2NO2 (334.20):
calcd. C 61.10, H 3.92, N 4.19; found C 60.88, H 4.12, N 4.37.
IR (KBr): ν = 3250–2600 (br., m), 1650 (s), 1620 (sh), 1595 (m),
˜
1560 (w) cm–1. 1H NMR (360 MHz, [D6]DMSO): δ = 7.25–7.55
(m, 7 H, ArH), 7.55–7.75 (t, J = 7 Hz, 1 H, ArH), 7.90 (dd, J = 7,
1.5 Hz, 1 H, 5-H), 12.20 (s, 1 H, NH) ppm. C15H10ClNO (255.70):
calcd. C 70.46, H 3.94, Cl 13.86, N 5.48; found C 70.45, H 3.82,
Cl 13.62, N 5.46.
2,4-Dichloro-6,7-dimethoxyquinoline (7b): Hydroxyquinolone 3f
(6.60 g, 30 mmol) and phosphoryl chloride (50 mL) were brought
to reaction (8 h) and worked up as described for 7a to afford 6.20 g
(80% yield) of colorless prisms. M.p. 160–161 °C (ethanol); ref.[15]
4-Chloro-3-nitroquinolin-2(1H)-one (8h): A solution of 2,4-dichloro-
3-nitroquinoline[16] (7d; 2.43 g, 10 mmol), 70% CH3SO3H (4.80 g,
50 mmol), and ethanol (30 mL) was brought to reaction (24 h,
60 °C) and worked up as described for 8c to afford 1.80 g (85%
yield) of light-brownish prisms. M.p. 278 °C (ethanol); ref.[17] m.p.
m.p. 159 °C. IR (KBr): ν = 3550–3350 (br., m), 3007 (m), 2983 (w),
˜
1
2945 (w), 1617 (m), 1570 (s), 1504 (s) cm–1. H NMR (360 MHz,
CDCl3): δ = 4.03 and 4.06 (2 s, 2ϫ3 H, 6- and 7-OMe), 7.37 (s, 1
H, 3-H), 7.38 (s, 1 H, 8-H), 7.39 (s, 1 H, 5-H) ppm. MS: m/z (%)
= 260 (75) [M + 2], 259 (17) [M + 1], 258 (100) [M], 223 (11).
C11H9Cl2NO2 (258.11): calcd. C 51.19, H 3.51, N 5.43; found C
51.45, H 3.20, N 5.67.
275 °C. IR (KBr): ν = 3250–2650 (br., m), 1690 (sh), 1670 (s), 1655
˜
(sh), 1620 (sh), 1610 (m), 1545 (m), 1520 (m) cm–1. C9H5ClN2O3
(224.60): calcd. C 48.13, H 2.24, N 12.47; found C 48.34, H 2.36,
N 12.33.
4-Chloro-6,7-dimethoxy-3-phenylquinolin-2(1H)-one (8a): A mixture
of dichloroquinoline 7a (200 mg, 0.6 mmol), aqueous KOH (5 ,
10 mL) and 18-crown-6 (10 mg) in ethanol (30 mL) was heated for
4 d. Insoluble parts were removed by filtration, and the solution
was acidified with HCl (6 ) to pH = 1–2. The solid was separated
by suction filtration to afford 130 mg (69 % yield) of colorless
3-Phenylquinoline-2,4-dicarbonitrile (9a): A mixture of 2,4-dichloro-
3-phenylquinoline[10a] (7c; 2.70 g, 10 mmol), KCN (1.32 g,
20 mmol), and 18-crown-6 (0.10 g) in dry DMF (30 mL) was
heated under reflux for 24 h. The mixture was cooled to 20 °C,
poured into ice/water (100 mL), allowed to stand for 12 h at 20 °C,
and then the solid was filtered by suction (attention: evolution of
HCN is possible!) and dried at 40 °C under reduced pressure to
afford 1.70 g (69% yield) of yellow microprisms. M.p. 254 °C (lig-
prisms. M.p. Ͼ300 °C (dec) (ethanol/water). IR (KBr): ν = 3560–
˜
3350 (br., m), 3007 (w), 2927 (m), 2848 (m), 2792 (sh), 1658 (s),
1
1625 (w), 1596 (m), 1510 (s) cm–1. H NMR (360 MHz, CDCl3): δ
= 3.92 and 4.07 (2 s, 2ϫ3 H, 6- and 7-OMe), 6.78 (s, 1 H, 8-
H), 7.38–7.53 (m, 6 H, PhH and 5-H), 11.83 (br. s, NH) ppm.
C17H14ClNO3 (315.76): calcd. C 64.67, H 4.47, N 4.44; found C
64.39, H 4.66, N 4.76.
roin). IR (KBr): ν = 2225 (m), 1650 (m), 1605 (m), 1560 (s) cm–1.
˜
C17H9N3 (255.28): calcd. C 79.98, H 3.55, N 16.46; found C 79.63.
H 3.87, N 16.07.
4-Chloro-6,7-dimethoxy-1-methyl-3-phenylquinolin-2(1H)-one (8b): 3-Nitroquinoline-2,4-dicarbonitrile (9b): 2,4-Dichloro-3-nitroquin-
A mixture of hydroxyquinolone 3a (5.42 g, 17 mmol) and phospho-
ryl chloride (30 mL) was heated under reflux for 1 h. The excess
amount of phosphoryl chloride was removed in vacuo, and the
residue was poured into ice/water (200 mL) and neutralized to pH
= 4–6 with aqueous NaOH (5 ). The precipitate was filtered by
suction and washed with water (100 mL) to afford 4.64 g (83 %
oline[16] (7d; 2.40 g, 10 mmol) in dry acetonitrile (30 mL) was
brought to reaction (48 h) and worked up as described for 9a to
afford 1.60 g (73% yield) of yellowish microprisms. M.p. 194 °C
(ligroin). IR (KBr): ν = 2225 (m), 1605 (m), 1550 (s) cm–1
.
˜
C11H4N4O2 (224.18): calcd. C 58.94, H 1.80, N 24.99; found C
59.77, H 1.63, N 24.88.
568
www.eurjoc.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 563–571

Carbostyrils with High Fluorescence Quantum Yields and Emission Maxima
6,7-Dimethoxy-2-oxo-1,2-dihydroquinolin-4-yl 4-Methylbenzenesulf-
inate (10): A mixture of chloroquinolone 8c (0.239 g, 1 mmol) and
sodium p-toluenesulfinate (267 mg, 1.5 mmol) in DMF (60 mL)
was heated at 120 °C for 20 h and then poured into water (150 mL).
The obtained solid was filtered by suction, washed with water
(100 mL), and dried at 40 °C under reduced pressure to afford
251 mg (72% yield) of yellow prisms. M.p. 295–296 °C (ethanol).
orange needles. M.p. 202–203 °C (ethanol). IR (KBr): ν = 3050 (w),
˜
2240 (m), 1640 (s), 1610 (m), 1600 (m), 1570 (w) cm–1. H NMR
(360 MHz, CDCl3): δ = 3.81 (s, 3 H, NMe), 7.42–7.50 (m, 5 H,
ArH), 7.55–7.65 (m, 2 H, ArH), 7.70 (t, J = 7 Hz, 1 H, ArH), 8.05
(dd, J = 7, 1.5 Hz, 1 H, 5-H) ppm. C17H12N2O (260.30): calcd. C
78.44, H 4.65, N 10.76; found C 78.18, H 4.64, N 10.38.
1
2-Oxo-1,3-diphenyl-1,2-dihydroquinoline-4-carbonitrile (11d)
IR (KBr): ν = 3650–3350 (br., m), 2969 (w), 2942 (m), 2904 (w),
˜
2844 (m), 1674 (s), 1625 (w), 1595 (w), 1516 (s) cm–1. 1H NMR
(360 MHz, CDCl3): δ = 2.43 (s, 3 H, Me), 3.93 and 4.02 (2 s, 2ϫ3
H, 6- and 7-OMe), 6.87 (s, 1 H, 3-H), 7.34–7.37 (m, 3 H, ArH),
7.73 (s, 1 H, ArH), 7.89 (d, J = 7.0 Hz, 2 H, ArH), 12.97 (s, 1 H,
NH) ppm. MS: m/z (%) = 360 (15) [M + 1], 359 (100) [M], 344
(24), 221 (9). C18H17NO5S (359.40): calcd. C 60.16, H 4.77, N 3.90;
found C 60.47, H 4.35, N 4.21.
Method A: A mixture of 4-chloro-1,3-diphenylquinolin-2(1H)-
one[8] (8e; 3.31 g, 10 mmol), lithium p-toluenesulfinate (4.05 g,
25 mmol), and KCN (1.65 g, 25 mmol) were brought to reaction
and worked up as described for 11a (Method A) to afford 2.51 g
(78% yield).
Method B: A mixture of chloroquinolone 8e (3.31 g, 10 mmol), so-
dium p-toluenesulfinate (4.45 g, 25 mmol), and KCN (1.65 g,
25 mmol) were brought to reaction and worked up as described for
11a (Method A) to afford 2.48 g (77% yield) of yellow microprisms.
6,7-Dimethoxy-2-oxo-1,2-dihydroquinoline-4-carbonitrile (11a)
Method A: A mixture of chloroquinolone 8c (2.39 g, 10 mmol), so-
dium p-toluenesulfinate (3.80 g, 21 mmol), and KCN (1.65 g,
25 mmol) in dry DMF (60 mL) was heated at 120 °C for 20 h with
vigorous stirring. After cooling to room temperature, the mixture
was poured into ice/water (200 mL) and acidified with concentrated
HCl to pH = 1–2. (attention: evolution of HCN is possible!). The
obtained solid was filtered by suction, washed with water, dried,
and crystallized from acetonitrile to afford 1.50 g (65% yield) of
yellow prisms.
M.p. 224 °C (dioxane). IR (KBr): ν = 2215 (m), 1650 (s), 1605 (w),
˜
1590 (w) cm–1 1H NMR (360 MHz, CDCl3): δ = 6.75 (d, J =
.
7.0 Hz, 1 H, ArH), 7.20–7.75 (m, 12 H, ArH), 8.05 (d, J = 7.0 Hz,
1 H, 5-H) ppm. C22H14N2O (322.37): calcd. C 81.97, H 4.38, N
8.69; found C 81.70, H 4.40, N 8.63.
3-Oxo-2-phenyl-6,7-dihydro-3H,5H-benzo[ij]quinolizin-1-carbo-
nitrile (11e): A mixture of 1-chloro-2-phenyl-6,7-dihydro-3H,5H-
benzo[ij]quinolizin-3-one[8] (8f; 4.44 g, 15 mmol), potassium cya-
nide (1.98 g, 30 mmol), and sodium p-toluenesulfinate (4.05 g,
23 mmol) was brought to reaction and worked up as described for
11a (Method A) to afford 4.32 g (92%) of yellow microprisms. M.p.
Method B: A mixture of quinolinyl tolyl sulfinate 10 (359 mg,
1.0 mmol) and potassium cyanide (100 mg, 1.5 mmol) in dry DMF
(6 mL) was heated at 70 °C for 6 h. Then, the mixture was poured
into water (50 mL) and acidified with concentrated HCl to pH =
1–2 (attention: evolution of HCN is possible!). The obtained solid
was filtered by suction, washed with water, and dried at 40 °C un-
der reduced pressure to afford 152 mg (65% yield) of yellow prisms.
197 °C (ethanol). IR (KBr): ν = 2900 (w), 2220 (m), 1640 (s), 1590
˜
(s) cm–1. 1H NMR (360 MHz, CDCl3): δ = 2.00–2.21 (m, 2 H,
CH2), 3.00–3.10 (m, 2 H, Ar-CH2), 4.10–4.20 (m, 2 H, N-CH2),
7.30–7.60 (m, 7 H, ArH), 7.74 (d, J = 8.0 Hz, 1 H, ArH), 7.95 (d,
J = 7.5 Hz, 1 H, 10-H) ppm. C19H14N2O (286.34): calcd. C 79.70,
H 4.93, N 9.78; found C 79.31, H 4.87, N 9.43.
M.p. 295–296 °C (acetonitrile). IR (KBr): ν = 3550–3400 (br., m),
˜
2921 (m), 2832 (w), 2218 (m), 1664 (s), 1625 (w), 1511 (s) cm–1. 1H
NMR (360 MHz, [D6]DMSO): δ = 3.79 and 3.86 (2 s, 2ϫ3 H, 6-
and 7-OMe), 6.85 (s, 1 H, 3-H), 7.24 (s, 1 H, 8-H), 8.54 (s, 1 H, 5-
H), 12.28 (s, 1 H, NH) ppm. UV (DMSO): λ = 398, 385 nm. UV
(water): λ = 380 nm. MS: m/z (%) = 231 (15) [M + 1], 230 (100)
[M]. C12H10N2O3 (230.23): calcd. C 62.61, H 4.38, N 12.17; found
C 62.69, H 4.65, N 11.65.
2,6,7-Trimethoxyquinoline-4-carbonitrile (12a): A mixture of 4-cya-
noquinolone 11a (2.30 g, 10 mmol), iodomethane (2.82 g,
20 mmol), and potassium carbonate (1.38 g, 5 mmol) in dry aceto-
nitrile (90 mL) was stirred at 50 °C for 5 h. Then, the reaction mix-
ture was poured into water (100 mL), and the obtained solid was
filtered, washed with water, and dried at 40 °C under reduced pres-
sure. TLC analysis showed two isomeric products: N-methylated
quinolone 13 and O-methylated quinoline 12; the yield was 1.8 g
(75%). The mixture was separated by dry flash column chromatog-
raphy (Merck Silica gel 60 H, 5–40 µm).[18] Toluene as the eluent
afforded O-methylated quinoline 12a (360 mg, 15% yield) as pale-
6,7-Dimethoxy-1-methyl-2-oxo-3-phenyl-1,2-dihydroquinoline-4-car-
bonitrile (11b): A mixture of chloroquinolone 8b (1.98 g, 6 mmol),
sodium p-toluenesulfinate (2.67 g, 15 mmol), and potassium cya-
nide (1.19 g, 18 mmol) was brought to reaction (65 h) and worked
up as described for 11a (Method A). Further purification was per-
formed by dry flash chromatography (Merck Silica gel 60 H, 5–
40 µm)[18] with hexane/ethyl acetate (6:4) as eluent. The samples
with the product (checked by TLC) were combined, and the solvent
was removed in vacuo. The crude product was crystallized from
ethanol to afford 310 mg (16% yield) of yellow prisms. M.p. 179–
yellow prisms. M.p. 184–185 °C (ethanol). IR (KBr): ν = 3550–
˜
3360 (w), 2949 (m), 2222 (s), 1622 (w), 1605 (s), 1576 (w) cm–1. 1H
NMR (360 MHz, CDCl3): δ = 4.00 and 4.06 (2 s, 2ϫ3 H, 6- and
7-OMe), 4.14 (s, 3 H, 2-OMe), 7.01 (s, 1 H, 3-H), 7.23 (s, 1 H, 8-
H), 8.23 (s, 1 H, 5-H) ppm. C13H12N2O3 (244.25): calcd. C 63.93,
H 4.95, N 11.47; found C 63.61, H 4.58, N 11.19.
185 °C (ethanol). IR (KBr): ν = 2960 (sh), 2920 (m), 2840 (sh),
˜
1
2205 (w), 1638 (s), 1620 (sh), 1583 (m) cm–1. H NMR (360 MHz,
Ethyl [(4-Cyano-6,7-dimethoxyquinolin-2-yl)oxy]acetate (12b): To a
stirred mixture of 4-cyanoquinolone 11a (2.30 g, 10 mmol) was
added aqueous NaOH (8 , 5 mL), dibenzo-18-crown-6 (150 mg,
0.25 mmol) in dichloromethane (200 mL), and ethyl bromoactate
(0.55 mL, 50 mmol), and the mixture was stirred 12–14 h until
starting material 11a had disappeared (TLC check). Then, the mix-
CDCl3): δ = 3.67 and 3.79 (2 s, 2ϫ3 H, 6- and 7-OMe), 4.02 (s, 3
H, NMe), 6.82 (s, 1 H, 8-H), 7.36–7.55 (m, 6 H, ArH) ppm. UV
(DMSO): λ = 398, 385 nm. UV (water): λ = 380 nm. MS: m/z (%)
= 307 (21), 306 (100) [M – 14], 257 (100). C19H16N2O3 (320.35):
calcd. C 71.24, H 5.03, N 8.74; found C 70.85, H 5.22, N 8.37.
1-Methyl-2-oxo-3-phenyl-1,2-dihydroquinoline-4-carbonitrile (11c): ture was filtered, and the solvent was removed under reduced pres-
A mixture of 4-chloro-1-methyl-3-phenylquinolin-2(1H)-one[8] (8d;
2.70 g, 10 mmol), sodium p-toluenesulfinate (3.80 g, 21 mmol), and
KCN (1.65 g, 25 mmol) was brought to reaction and worked up as
described for 11a (Method A) to afford 3.56 g (97 % yield) of
sure. The combined solids were rinsed with hexane (40 mL), fil-
tered, washed with hexane, and dried at 40 °C under reduced pres-
sure. TLC analysis showed two isomeric products: N-alkylated
quinolone 13b and O-alkylated quinoline 12b; the yield was 2.84 g
Eur. J. Org. Chem. 2008, 563–571
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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569

W. Stadlbauer et al.
FULL PAPER
(90%). The mixture was separated by dry flash column chromatog-
raphy (Merck Silica gel 60 H, 5–40 µm).[18] Toluene as eluent af-
forded O-alkylated quinoline 12b (470 mg, 15 % yield) as light-
quinolinylacetic acid 14 (288 mg, 1.0 mmol) in dry tetrahydrofuran
(20 mL) at 0 °C. Then N,N-diisopropylcarbodiimide (125 mg,
1.0 mmol) was added at 0–5 °C dropwise whilst stirring, which
formed a yellowish-white precipitate; the mixture was stirred at 0–
green prisms. M.p. 158–159 °C (ethanol). IR (KBr): ν = 3480–3420
˜
(br., w), 3000–2930 (br., w), 2227 (m), 1753 (s), 1655 (w), 1621 (m), 5 °C for about 15 h, and the solvent was removed under reduced
1
1607 (m), 1511 (s) cm–1. H NMR (360 MHz, CDCl3): δ = 1.27 (t, pressure. The obtained solid was filtered by suction and washed
J = 7.1 Hz, 3 H, ethyl-CH3), 4.02 and 4.04 (2 s, 2ϫ3 H, 6- and 7-
OMe), 4.27 (q, J = 7.1 Hz, 2 H, ethyl-CH2), 5.07 (s, 2 H, acetate-
CH2), 7.02 (s, 1 H, 3-H), 7.14 (s, 1 H, 8-H), 8.26 (s, 1 H, 5-H) ppm.
MS: m/z (%) = 317 (10) [M + 1], 316 (100) [M]. C16H16N2O5
(316.32): calcd. C 60.76, H 5.10, N 8.86; found C 61.11, H 5.24, N
8.51.
with dry tetrahydrofuran. The solid was then stirred in dry ethanol
(50 mL) at 20 °C for 30 min to remove N,N-diisopropylurea formed
during the reaction. Suction filtration afforded 288 mg (59% yield)
of pale-yellow prisms. M.p. 232–233 °C (ethanol). IR (KBr): ν =
˜
3300–3550 (br., s), 2909 (m), 2223 (m), 1809 (w), 1783 (m), 1745 (s),
1660 (sh), 1646 (m), 1621 (m), 1561 (m) cm–1. 1H NMR (500 MHz,
CDCl3): δ = 2.87 (s, 4 H, 2 succinimide-CH2), 3.97 and 4.14 (2 s,
2ϫ3 H, 6- and 7-OMe), 5.56 (s, 2 H, acetate-CH2), 6.64 (s, 1 H,
3-H), 6.98 (s, 1 H, 8-H), 8.15 (s, 1 H, 5-H) ppm. UV (DMSO): λ
= 398, 385 nm. UV (water): λ = 380 nm. MS: m/z (%) = 386 (5)
[M + 1], 385 (42) [M], 288 (17), 270 (100). C18H15N3O7 (385.34):
calcd. C 56.11, H 3.92, N 10.90; found C 56.34, H 3.89, N 11.29.
6,7-Dimethoxy-1-methyl-2-oxo-1,2-dihydroquinoline-4-carbonitrile
(13a): The reaction was performed as described for O-methylated
quinoline 12a: dry flash column chromatography[18] of the mixture
of quinolines 12a/13a with toluene/acetone (9:1) as the eluent gave
N-methylated quinolone 13a (1.44 g, 60 % yield) as pale-yellow
prisms. M.p. 260–261 °C (ethanol). IR (KBr): ν = 3500–3350 (br.,
˜
N-[(4-Cyano-6,7-dimethoxy-2-oxo-1,2-dihydroquinolin-1-yl)acetyl-
amino]-3-phenylpropionic Acid (17a): To a solution of (, )-phenyl-
alanine (16a; 19 mg, 0.1 mmol) in 90% aqueous DMSO (1.5 mL)
was added a solution of OSu ester 15 (38 mg, 0.1 mmol) in 90%
aqueous DMSO (1.5 mL) dropwise at 20 °C. Then, aqueous pH 7
buffer solution (Merck 9887, 0.75 mL) was added. The mixture was
stirred for 14 h at 20 °C, poured into water (25 mL), and then acidi-
fied with concentrated HCl to pH = 1–2. A solid separated, which
was filtered by suction and washed with an excess amount of water
to afford 29 mg (68 % yield) of dark-yellow prisms. M.p. 242–
w), 3045 (m), 2963 (m), 2919 (w), 2226 (m), 1632 (s), 1592 (w),
1567 (w), 1524 (m) cm–1. 1H NMR (360 MHz, CDCl3): δ = 3.77
and 3.96 (2 s, 2ϫ3 H, 6- and 7-OMe), 4.06 (s, 3 H, NMe), 6.77 (s,
1 H, 3-H), 6.97 (s, 1 H, 8-H), 8.09 (s, 1 H, 5-H) ppm. UV (DMSO):
λ (ε, –1 cm–1) = 390 (12400) nm. Fluorescence data: see Table 1.
MS: m/z (%) = 245 (23) [M + 1], 244 (100) [M]. C13H12N2O3
(244.25): calcd. C 63.93, H 4.95, N 11.47; found C 63.68, H 5.23,
N 11.71.
Ethyl (4-Cyano-6,7-dimethoxy-2-oxo-1,2-dihydroquinoline-4-yl)ace-
tate (13b): The reaction was performed as described for O-alkylated
quinoline 12b: Dry flash column chromatography[18] of the mixture
of quinolines 12b/13b with toluene/acetone (9:1) as eluent afforded
N-alkylated quinolone 13b (2.37 g, 75% yield) as yellow prisms.
243 °C (acetone). IR (KBr): ν = 3550–3350 (br., w), 3295 (m), 2227
˜
(m), 1710 (m), 1654 (s), 1633 (s), 1562 (m), 1549 (w) cm–1. 1H NMR
(500 MHz, [D6]DMSO): δ = 2.90 and 3.05 (2 m, 2 H, PhCH2), 3.78
and 3.82 (2 s, 2ϫ3 H, 6- and 7-OMe), 4.42–4.44 (m, 1 H, N-CH),
4.85 (d, J = 16.4 Hz, 1 H, 1/2 acetate-CH2), 5.12 (d, J = 16.4 Hz,
1 H, 1/2 acetate-CH2), 6.60 (s, 1 H, 3-H), 7.21 (m, 5 H, PhH), 7.33
(s, 1 H, 8-H), 8.60 (s, 1 H, 5-H), 8.69 (d, J = 12.0 Hz, 1 H, NH)
ppm. UV (DMSO): λ (ε, –1 cm–1) = 385 (13300) nm. Fluorescence
(H2O): λ (ΦF) = 433 (0.73) nm. Fluorescence (DMSO): λ (ΦF) =
436 (0.60) nm. C23H21N3O6 (435.44): calcd. C 63.44, H 4.86, N
9.65; found C 63.12, H 4.51, N 10.03.
M.p. 220–221 °C (ethanol). IR (KBr): ν = 3480–3400 (br., w), 2922
˜
(m), 2963 (s), 2226 (s), 1732 (s), 1657 (s), 1625 (m), 1567 (w), 1560
1
(m), 1536 (w) cm–1. H NMR (360 MHz, CDCl3): δ = 1.28 (t, J =
7.1 Hz, 3 H, ethyl-CH3), 3.96 and 3.99 (2 s, 2ϫ3 H, 6- and 7-
OMe), 4.26 (q, J = 7.1 Hz, 2 H, ethyl-CH2), 5.11 (s, 2 H, acetate-
CH2), 6.53 (s, 1 H, 3-H), 6.99 (s, 1 H, 8-H), 8.14 (s, 1 H, 5-H)
ppm. UV (DMSO): λ (ε, –1 cm–1) = 385 (10400) nm. Fluorescence
(H2O): λ (ΦF) = 435 (0.53) nm. Fluorescence (DMSO): λ (ΦF) =
436 (0.46) nm. MS: m/z (%) = 317 (10) [M + 1], 316 (100) [M], 270
(47) [M – 46]. C16H16N2O5 (316.32): calcd. C 60.76, H 5.10, N 8.86;
found C 60.97, H 5.02, N 8.63.
(2-{2-[2-(4-Cyano-6,7-dimethoxy-2-oxo-1,2-dihydroquinolin-1-yl)-
acetylamino]acetylamino}acetylamino)acetic Acid (17b): Glycyl-gly-
cyl-glycine (16b; 20 mg, 0.1 mmol) was brought to reaction and
worked up as described for labeled phenylalanine 17a to afford
25 mg (55% yield) of dark-yellow prisms. M.p. 238–239 °C (ace-
(4-Cyano-6,7-dimethoxy-2-oxo-1,2-dihydroquinolin-1-yl)acetic Acid
(14): A solution of quinolinylacetate 13b (316 mg, 1.0 mmol) in eth-
anol (20 mL) and aqueous NaOH (1 , 2 mL) was heated under
reflux for 7 h. Ethanol was then removed under reduced pressure,
and the residue was dissolved in water (10 mL) under cooling. The
mixture was acidified with concentrated HCl to pH = 1–2, and the
resulting precipitate was filtered by suction and washed with water,
which afforded 232 mg (80% yield) as yellow prisms. M.p. 281–
tone). IR (KBr): ν = 3354 (s), 3302 (s), 3071 (m), 3047 (m), 2948
˜
(m), 2922 (m), 2224 (m), 1734 (m), 1639 (s), 1633 (s), 1566 (s), 1530
(w) cm–1. 1H NMR (500 MHz, [D6]DMSO): δ = 3.67 (d, J =
5.04 Hz, 2 H, glycyl-CH2), 3.72 (d, J = 5.76 Hz, 2 H, glycyl-CH2),
3.79 (d, J = 5.76 Hz, 2 H, glycyl-CH2), 3.81 and 3.92 (2 s, 2ϫ3 H,
6- and 7-OMe), 5.06 (s, 2 H, acetate-CH2), 6.83 (s, 1 H, 3-H), 7.34
(s, 1 H, 8-H), 8.08 (t, J = 5.79 Hz, 1 H, NH), 8.25 (t, J = 5.79 Hz,
1 H, NH), 8.60 (s, 1 H, 5-H), 8.62 (t, J = 5.79 Hz, 1 H, NH)
ppm. UV (DMSO): λ (ε, –1 cm–1) = 385 (11600) nm. Fluorescence
(H2O): λ (ΦF) = 434 (0.56) nm. Fluorescence (DMSO): λ (ΦF) =
436 (0.46) nm. C20H21N5O8 (459.42): calcd. C 52.29, H 4.61, N
15.24; found C 51.90, H 4.48, N 15.52.
282 °C (ethyl acetate). IR (KBr): ν = 3522 (s), 3400 (m), 2229 (w),
˜
1
1736 (m), 1641 (s), 1626 (s), 1596 (w), 1566 (s), 1514 (s) cm–1. H
NMR (360 MHz, [D6]DMSO): δ = 3.82 and 3.92 (2 s, 2ϫ3 H, 6-
and 7-OMe), 5.09 (s, 2 H, acetate-CH2), 6.99 (s, 1 H, 3-H), 7.35 (s,
1 H, 8-H), 8.63 (s, 1 H, 5-H) ppm. UV (DMSO): λ (ε, –1 cm–1) =
398, 385 (9800) nm. UV (water): λ (ε, –1 cm–1) = 380 (8700) nm.
MS: m/z (%) = 289 (16) [M + 1], 288 (80) [M], 244 (28), 243 (28),
184 (100). C14H12N2O5 (288.26): calcd. C 58.33, H 4.20, N 9.72;
found C 57.95, H 4.34, N 9.38.
Acknowledgments
This research was supported by scholarships from the Austrian Ac-
ademic Exchange Service (ÖAD EZA project 894/05, for A. B. A.)
and the Central European Exchange Program for University Stud-
ies (CEEPUS network, for J. S. and H. P.).
1-{2-[(2,5-Dioxopyrrolidin-1-yl)oxy]-2-oxoethyl}-6,7-dimethoxy-2-
oxo-1,2-dihydroquinoline-4-carbonitrile (15): N-Hydroxysuccinimide
(115 mg, 1.0 mmol) was added slowly with stirring to a solution of
570
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Received: October 19, 2007
Published Online: November 27, 2007
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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