ZnCl2-catalyzed intramolecular cyclization reaction of 2-aminochalcones using polymer-supported selenium reagent: Synthesis of 2-phenyl-4-quinolones and 2-phenyl-2,3-dihydroquinolin-4(1 H)-one

Article abstract of DOI:10.1055/s-0030-1259549

A new and efficient method for the synthesis of 2-phenyl-4-quinolones and 2-phenyl-2,3-dihydroquinolin-4(1H)-ones is described. The reaction involves ZnCl₂-mediated polystyrene-supported selenium-induced intramolecular cyclization of 2-amino-chalcones and subsequent traceless or functionalizing cleavage of selenium linker. Georg Thieme Verlag Stuttgart - New York.

Full text of DOI:10.1055/s-0030-1259549

LETTER
707
ZnCl2-Catalyzed Intramolecular Cyclization Reaction of 2-Aminochalcones
Using Polymer-Supported Selenium Reagent: Synthesis of 2-Phenyl-4-
quinolones and 2-Phenyl-2,3-dihydroquinolin-4(1H)-one
S
ynthesis of 2-Phenyl
T
-4-quinolones
a
a
nd 2-Pheny
n
l-2,3-dihydro
g
quinolin-4(1
,
H
)-on
*
e
Bangzheng Chen, Lianpeng Zhang, Wen Li, Jun Lin
School of Chemical Science and Technology, Yunnan University, Kunming 650091, P. R. of China
Fax +86(871)5033725; E-mail: tange@ynu.edu.cn
Received 27 November 2010
Dedicated to the memory of Prof. Xian Huang
pounds can be used as synthetic intermediates10 and Se–C
Abstract: A new and efficient method for the synthesis of 2-phe-
nyl-4-quinolones and 2-phenyl-2,3-dihydroquinolin-4(1H)-ones is
described. The reaction involves ZnCl2-mediated polystyrene-sup-
ported selenium-induced intramolecular cyclization of 2-amino-
bond can be easily broken by various methods.11 Further-
more, polymer-supported organic selenides can overcome
the shortcomings such as highly malodorous and toxicity
chalcones and subsequent traceless or functionalizing cleavage of of organic selenides. In the past decade, a variety of het-
selenium linker.
erocyclic compounds libraries have been constructed
from organoselenium resins by several research groups12
Key words: polystyrene-supported selenium reagent, intramolec-
and ours.13 In recent years, we have become interested in
ular cyclization, zinc chloride, 2-phenyl-4-quinolones, 2-phe-
nyl-2, 3-dihydroquinolin-4(1H)-one
Lewis acid catalyzed polystyrene-supported selenium-
mediated intramolecular cyclization reaction of electron-
deficient olefins with heteroatom.13a While polystyrene-
2-Aryl-4-quinolones and 2-phenyl-2,3-dihydroquinolin- supported selenium bromide has been successfully ap-
4(1H)-ones have been studied as potential treatments for plied in the synthesis of heterocyclic compounds by the
a range of diseases1 because of their important biological intramolecular electrophilic cyclization of electron-rich
properties, such as antiviral,1c,d antiplatelet,1b antitumor,2 olefins with heteroatom,12c,d olefins conjugated with the
and positive cardiac effects.1a Various methods have been carbonyl group, and of course the electron-deficient ole-
reported for the synthesis of 2-aryl-4-quinolones and 2- fins, fail to react with selenium resins.13a In order to over-
phenyl-2,3-dihydroquinolin-4(1H)-ones.3 Conrad–Limpach come the preparative obstacle, we envisioned that Lewis
and Niementowski reactions4 generally focus on the con- acid could dampen the impact of carbonyl group on olefin
densation of amines and carboxyl derivatives followed by and realize the addition of organoseleium reagent to ole-
cyclization to produce the desired quinolones. Often the fins. We have reported that ZnCl2 has a high catalytic ac-
substrate scope of these reactions is limited by the neces- tivity in the polystyrene-supported selenium-induced
sity to employ harsh cyclization conditions, including cyclization of 2-hydroxychalcones.13a In continuation of
temperature above 200 °C or strong acids such as poly- our efforts toward the solid-phase synthesis of heterocy-
phosphoric acid or Eaton’s reagent. Examples on transi- clic compounds, herein we describe an efficient approach
tion-metal-catalyzed syntheses of these compounds,5 for the solid-phase synthesis of 2-aryl-4-quinolones and
including palladium-catalyzed carbonylation reaction,6 ti- 2-phenyl-2,3-dihydroquinolin-4(1H)-ones. The key trans-
tanium-mediated reductive coupling reaction,7 and ruthe- formation of this synthetic process involves ZnCl2-
nium-catalyzed reduction reaction,8 have also been catalyzed intramolecular cyclization reaction of 2-ami-
reported. Huang has reported a solid-phase synthesis of nochalcones induced by polymer-supported organoseleni-
4(1H)-quinolones by the thermal cyclization reaction of um reagents and subsequent oxidation and elimination
polymer-bound substituted aminomethylene cyclic mal- reaction of selenides, and free-radical hydrogenation or
onic acid esters at 220–240 °C.9 High reaction tempera- allylation reaction of selenides.
ture limits the application of this method. Therefore, it is
First, 2-aminochalcones were synthesized in yield of 80%
still a challenge to explore a mild and efficient solid-phase
by reaction of 2-aminoacetophenone with benzaldehyde
synthesis of 4-quinolones.
in the presence of sodium hydroxide at 0 °C.14 Then poly-
Solid-phase synthesis is becoming an increasingly impor- styrene-supported selenenyl bromide15 (dark-red resin,
tant tool for the synthetic chemists due to the simple work- Br: 0.99 mmol/g), was treated in turn with ZnCl2 and 2-
up procedure and adaptable to parallel synthesis. aminochalcones in dry CH2Cl2 to give the corresponding
Organoselenium resins are ideal linkers and reagents for 2,3-dihydro-3-polystyrene-supported
selenenyl-4-qui-
solid-phase synthesis because organoselenium com- nolone (2) which underwent further NH-alkylation with
alkyl halides under alkaline conditions to give 3, subse-
quent selenide oxidation and elimination reactions with
SYNLETT 2011, No. 5, pp 0707–0711
Advanced online publication: 15.02.2011
DOI: 10.1055/s-0030-1259549; Art ID: W18710ST
© Georg Thieme Verlag Stuttgart · New York
x
x.
x
x.
2
0
1
1
H2O2 to afford 1-alkyl-4-quinolone 4 in moderate yields
(40–48%). The yields of 4 could be increased to 76–89%
when 2-alkylamino chalcones 5 were used as reactants

708
E Tang et al.
LETTER
(Scheme 1). This was probably due to the higher nucleo-
philicity of the alkylamino moiety.
Table 1 Optimization of Solid-Phase Conditions of Cyclization
Entry
Lewis acid
(mol%)
Time
(h)
Yield of 4a Purity of 4a
(%)a
n.r.
n.r.
n.r.
45
(%)b
It was observed that the decolorization of polystyrene-
supported selenenyl bromide occurred when 5.0 equiva-
lents of compound 1 were used. After being stirred at
room temperature for 12 hours, the solid-phase ring-
closure reaction was completed, and elemental analysis of
resin 2 showed that no Br was present. The reaction was
also monitored by FT-IR, which showed a strong peak of
the carbonyl absorption at 1638 cm–1 in the resulting resin
2.
1
2
TiCl4 (40)
12
12
12
12
12
12
12
12
12
12
24
–
BF3·OEt2 (40)
SnCl2·4H2O (40)
SnCl4 (40)
AlCl3 (40)
FeCl3 (40)
ZrCl4 (40)
–
3
–
4
>85
>80
>80
>80
>90
>95
>95
>90
5
20
6
28
O
O
SeBr, ZnCl2
CH2Cl2, r.t.
7
10
Se
route B
8
ZnCl2 (20)
ZnCl2 (40)
ZnCl2 (60)
ZnCl2 (40)
64
NH2
N
H
9
82
1
2
10
11
80
RX, K2CO3, DMF
55~90%
RX, NaI
K2CO3, DMF
route A
route B
80
a Yields of the crude products based on the loading of selenium bro-
mide resin (Br, 0.99 mmol/g); n.r. = no reaction.
b Determined by HPLC analysis.
O
O
SeBr, ZnCl2
CH2Cl2, r.t.
Se
route A
NH
R
N
R
3
above conditions. The results are summarized in Table 2.
A variety of quinolones 4 containing neutral, electron-
rich, and electron-poor aryl substituents could be obtained
in good yields. HPLC analysis showed that the purities of
the products were >90% in most cases. 1-alkyl substitu-
ents were also tolerated. However, the yield of products
4d, 4e, and 4f was low (50–55%) when using 30% H2O2
at 0–25 °C as the traceless cleavage reaction conditions of
30% H2O2
0 °C to r.t.
5
5a R = Bn
5b R = Me
5c R = Et
3a R = Bn
3b R = Me
3c R = Et
O
N
R
4a R = Bn
4b R = Me
4c R = Et
O
O
4
SeBr, ZnCl2
CH2Cl2, r.t.
route B
total yield via route A: 76–89%
total yield via route B: 40–48%
Se
Scheme 1
NH2
N
H
1
2
In an effort to optimize the reaction conditions, various
cyclization reaction conditions involving 2-benzylamino
chalcone (5a) and polystyrene-supported selenenyl bro-
mide were explored (Table 1). In the first attempt, 40
mol% of SnCl4, FeCl3, AlCl3, and ZrCl4 were used as cat-
alyst, respectively, product 4a was obtained in low yields
(Table 1, entries 4–7), 82% being the highest yield ob-
tained when using 40 mol% of ZnCl2 as the catalyst at
room temperature for 12 hours (Table 1, entry 9).
AcCl, pyridine
86%
AcCl, Et3N, CH2Cl2
or AcCl, pyridine
route A
route B
O
O
SeBr, ZnCl2
CH2Cl2, r.t.
Se
route A
NH
Ac
6a
N
Ac
7a
n-Bu3SnH
AIBN
Increasing or decreasing the amount of ZnCl2 or prolong-
ing the reaction time had little effect on the yield of 4a.
TiCl4, BF3·OEt2, and SnCl2·4H2O has no catalytic activity
in the cyclization reaction (Table 1, entries 1–3). As a re-
sult, the optimized conditions of the cyclization reaction
were 5.0 equivalents of 5, 40 mol% of ZnCl2, and 1.0 g of
polystyrene-supported selenenyl bromide in 15 mL of dry
CH2Cl2 at room temperature for 12 hours. To test the
scope and generality of this protocol, the polystyrene-sup-
ported selenium-induced cyclization reactions of a series
of substituted 2-amino-chalcones 5 were studied under the
O
H2O2
O
N
N
Ac
9a
total yield from 6a: 82%
Ac
8a
Scheme 2
Synlett 2011, No. 5, 707–711 © Thieme Stuttgart · New York

LETTER
Synthesis of 2-Phenyl-4-quinolones and 2-Phenyl-2,3-dihydroquinolin-4(1H)-one
709
Table 2 Solid-Phase Synthesis of 4-Quinolone 417
washed off, and the selenoxide was eliminated in CCl4 un-
der heating conditions (Table 2, entries 4–6).
O
O
The reaction of 1-(2-acetylaminophenyl)-3-phenylprop-
2-en-1-one (6a) with polystyrene-supported selenenyl
bromide afforded the intramolecular aminoselenation
products 7 which could also be obtained from the acetyla-
tion of 2 in pyridine or in Et3N–CH2Cl2. However, the re-
action of 7a with hydrogen peroxide did not afford 1-
acetyl-2-phenylquilolin-4(1H)-one (8a). The structure of
products 7a was confirmed by the reduction of 7a with
tributyltin hydride and afforded 1-acetyl-2-phenyl-2,3-di-
hydroquinolin-4(1H)-one (9a, Scheme 2).
Se
SeBr, ZnCl2
CH2Cl2, r.t.
R2
R2
R3
R4
R3
R4
NH
R1
N
R1
H2O2
3
5
O
R2
R3
R4
N
R1
4
Furthermore, 1-acetyl-3-allyl-2-phenyl-2,3-dihydroquin-
olin-4(1H)-one (9b) was obtained by using allyltributyl-
stannane as the cleavage reagent of selenium linker.
Therefore, a series of substituted 2-phenyl-3-polystyrene-
supported seleno-2,3-dihydroquinolin-4(1H)-ones 7 were
Entry R1
R2
R3
R4
Product Yield Purity
(%)a (%)d
1
2
3
4
Bn
H
H
H
H
H
H
H
H
H
H
H
H
4a
4b
4c
4d
89b
77b
76b
>95
>95
>95
Me
Et
H
Table 3 Solid-Phase Synthesis of 4-Keton-2-phenyl-1,2,3,4-tetra-
hydroquinoline 918
O
O
50b
70c
–
>90
n-Bu3SnR5,
AIBN
R5
Se
R2
R2
R3
R4
R3
R4
toluene, 90 °C
5
6
H
H
H
H
F
H
4e
4f
52b
72c
–
>90
N
R1
N
R1
OMe OMe
55b
70c
–
>90
7
9
Entry R1
R2
R3
R4
R5
Product Yield Purity
(%)a (%)b
7
8
Me
Bn
Bn
Bn
Bn
Bn
Bn
Bn
Bn
H
F
H
H
H
F
OMe
Br
4g
4h
4i
79b
82b
68b
77b
80b
75b
69b
84b
86b
>95
>95
>95
>95
>90
>85
>90
>95
>95
1
2
Ac
Ac
Ac
Ac
Ac
Ac
Ac
Ac
Ac
Ac
Ac
Ac
Ac
Ac
Ac
Ac
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Br
Br
H
H
H
H
9a
82
79
78
85
70
73
80
68
83
75
69
74
65
70
55
50
68
>95
>90
>90
>95
>90
>85
>90
>85
>90
>85
>80
>85
>80
>85
>80
>80
>80
9
H
H
H
Cl
H
H
H
OMe
H
H
H
Allyl 9b
10
11
12
13
14
15
4j
3
OMe
H
H
H
H
9c
H
H
CF3
Cl
4k
4l
4
OMe
H
9d
5
OMe
H
Allyl 9e
OMe OBn
4m
4n
4o
6
OMe Allyl 9f
H
H
Cl
Br
7
H
F
H
9g
8
H
F
Allyl 9h
9
H
Br
H
H
H
9i
9j
73b
>85
O
16
Bn
H
H
4p
10
11
12
13
14
15
16
17
Br
H
O
17
18
Bn
Bn
H
H
H
OBn
4q
4r
83b
65b
>90
>85
Br
H
Allyl 9k
Allyl 9l
OMe OMe
Br
H
a Yields of the crude products based on the loading of selenium bro-
mide resin (Br, 0.99 mmol/g).
CF3
CF3
H
H
9m
Allyl 9n
9o
Allyl 9p
9q
b The reaction conditions of selenide oxidation and elimination is 30%
H2O2, THF, 0 °C 1 h, then r.t., 20 min.
H
c Selenide oxidation and elimination reaction involves two steps: (a)
30% H2O2, THF, 0 °C, 2 h; (b) CCl4, 80 °C, 10 min.
d Determined by HPLC analysis.
H
H
H
H
H
H
H
a Yields of the crude products based on the loading of selenium bro-
mide resin (Br, 0.99 mmol/g) via route A.
selenium linker. The yield of 4d, 4e, and 4f was signifi-
cantly improved when selenide was oxidized by 30%
H2O2 in THF at 0 °C for 2 hours, then the oxidant was
b Determined by HPLC analysis.
Synlett 2011, No. 5, 707–711 © Thieme Stuttgart · New York

710
E Tang et al.
LETTER
synthesized, followed by free-radical hydrogenation and
allylation reaction with tributyltin hydride and allyltri-
butylstannane in the presence of 2,2-azobis(2-methylpro-
pionitrile) (AIBN) in toluene at 90 °C to afford 2-phenyl-
2,3-dihydroquinolin-4(1H)-ones 9 in good yields and pu-
rities. Substituents on benzene ring had little impact on the
free-radical cleavage reaction (Table 3).
References and Notes
(1) (a) Osawa, T.; Ohta, H.; Akimoto, K.; Harada, K.; Soga, H.;
Jinno, Y. EP 0343574, 1994. (b) Huang, L.-J.; Hsieh,
M.-C.; Teng, C.-M.; Lee, K.-H.; Kuo, S.-C. Bioorg. Med.
Chem. 1998, 6, 1657. (c) Llinàs-Brunet, M.; Bailey, M. D.;
Ghiro, E.; Gorys, V.; Halmos, T.; Poirier, M.; Rancourt, J.;
Goudreau, N. J. Med. Chem. 2004, 47, 6584. (d) Frutos, R.
P.; Haddad, N.; Houpis, I. N.; Johnson, M.; Smith-Keenan,
L. L.; Fuchs, V.; Yee, N. K.; Farina, V.; Faucher, A.-M.;
Brochu, C.; Haché, B.; Duceppe, J.-S.; Beaulieu, P.
Synthesis 2006, 2563.
(2) Selected references on 2-aryl-4-quinolones as antitumor
agents: (a) Hadjeri, M.; Peiller, E.-L.; Beney, C.; Deka, N.;
Lawson, M. A.; Dumontet, C.; Boumendjel, A. J. Med.
Chem. 2004, 47, 4964. (b) Ferlin, M. G.; Chiarelotto, G.;
Gasparotto, V.; Via, L. D.; Pezzi, V.; Barzon, L.; Palu, G.;
Castagliuolo, I. J. Med. Chem. 2005, 48, 3417.
We have studied the reaction of 1-(2-acetylaminophenyl)-
3-phenyl-2-propen-1-one (6a) (1.0 equiv) and benzenese-
lenenyl bromide16 (1.0 equiv) catalyzed by 40 mol% an-
hydrous ZnCl2 in CH2Cl2 at room temperature. 1-Acetyl-
2-phenyl-3-(phenylselenyl)-2,3-dihydroquinolin-4(1H)one
(10) was obtained in isolated yield of 42% (Scheme 3).
(c) Gasparotto, V.; Castagliuolo, I.; Chiarelotto, G.; Pezzi,
V.; Montanaro, D.; Brun, P.; Palu, G.; Viola, G.; Ferlin,
M. G. J. Med. Chem. 2006, 49, 1910.
O
O
PhSeBr, ZnCl2
CH2Cl2, r.t.
Se
(3) (a) Reitsema, R. H. Chem. Rev. 1948, 43, 43. (b) Katritzky,
A. R.; Lagowski, J. M. In Advances in Heterocyclic
Chemistry, Vol. 1; Katritzky, A. R., Ed.; Academic Press:
New York, 1963, 339–437. (c) Mphahlele, M. J.; El-Nahas,
A. M. J. Mol. Struct. 2004, 688, 129.
42%
NH
Ac
6a
N
Ac
10
(4) (a) Li, J. J. Conrad-Limpach Reaction in Name Reactions:
A Collection of Detailed Reaction Mechanisms, 2nd ed.;
Springer: Berlin, 2003, 81. (b) Staskun, B.; Israelstam, S. S.
J. Org. Chem. 1961, 26, 3191. For methods utilizing
Eaton’s reagent: (c) Zewge, D.; Chen, C.-Y.; Deer, C.;
Dormer, P. G.; Hughes, D. L. J. Org. Chem. 2007, 72, 4276.
Niementowski methods: (d) Fuson, R. C.; Burness, D. M.
J. Am. Chem. Soc. 1946, 68, 1270.
(5) (a) Beifuss, U.; Ledderhose, S. Synlett 1997, 313.
(b) Strekowski, L.; Wydra, R. L.; Cegla, M. T.; Czarny, A.;
Harden, D. B.; Patterson, S. E.; Battiste, M. A.; Coxon, J. M.
J. Org. Chem. 1990, 55, 4777.
Scheme 3
However, in the solid-phase reaction, excess 6a was used,
and the yield of the product was significantly improved.
Furthermore, after the reaction, only polymer-supported
intermediate 7a was obtained after washing with various
solvents, and all other byproducts and remaining 6a were
washed off. The separation process was very simple.
In conclusion, a new methodology for the solid-phase
synthesis of 1-alkyl-2-phenyl-4-quinolones and 2-phenyl-
2,3-dihydroquinolin-4(1H)-ones has been established.
The highlight of the synthetic strategy is that organosele-
nium resin is capable of loading substrates through elec-
trophilic cyclization reactions. The target products were
obtained in good yields and with high purities by the
traceless or functionalizing cleavage of selenium linker.
Furthermore, the easy workup procedure and mild reac-
tion conditions provide an approach that is well suited for
building the parallel libraries upon the basis of further
transformation of 4-quinolones and 2,3-dihydroquinolin-
4(1H)-ones. Further modifications of resin 3 are under
way.
(6) Torii, S.; Okumoto, H.; Xu, L. H.; Sadakane, M.;
Shostakovsky, M. V.; Ponomaryov, A. B.; Kalinin, V. N.
Tetrahedron 1993, 49, 6773.
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Chem. 1994, 59, 5215.
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2001, 57, 1411.
(11) Nicolaou, K. C.; Pfefferkorn, J. A.; Cao, G. Q.; Kim, S.;
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(c) Nicolaou, K. C.; Pfefferkorn, J. A.; Cao, G.-Q. Angew
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Supporting Information for this article is available online at
http://www.thieme-connect.com/ejournals/toc/synlett.
Acknowledgment
Thanks are due to the National Natural Science Foundation of
China (Project No. 20802063) and the Foundation of the Yunnan
Province education department, China (08Y0035).
Synlett 2011, No. 5, 707–711 © Thieme Stuttgart · New York

LETTER
Synthesis of 2-Phenyl-4-quinolones and 2-Phenyl-2,3-dihydroquinolin-4(1H)-one
711
(15) Nicolaou, K. C.; Pastor, J.; Barluenga, S.; Winssinger, N.
Chem. Commun. 1998, 1947.
(16) Benzeneselenenyl bromide was prepared by the reaction of
diphenyldiselenide (1.0 equiv) and bromine (1.0 equiv) in
CH2Cl2 at r.t. for 1 hour.
125.22, 124.09, 117.30, 112.59, 52.36. IR (KBr):
max = 1608, 1486, 763 cm–1. HRMS: m/z calcd for
C22H18NO [M + H]+: 312.1388; found: 312.1385.
n
(18) General Procedure for the Preparation of 2-Phenyl-2,3-
dihydroquinolin-4 (1H)-one (9)
(17) General Procedure for Obtaining 4-Quinolone 4 via
Route A
An oven-dried schlenk tube was charged with a suspension
of the swollen resin 7 (0.5 g) in dry toluene (10 mL) under
nitrogen atmosphere, and tributyltin hydride (0.291 g, 1.0
mmol) or allyltributylstannane (0.331 g, 1.0 mmol) and 2,2¢-
azobisisobutyronitrile (AIBN, 0.082 g, 0.5 mmol) were
added after which the reaction mixture was heated to 90 °C
for 2 hours. After cooling, the suspension was poured into a
fritted funnel, and the resin was washed with CH2Cl2 (2 × 10
mL). The filtrate was then concentrated and 10% HCl (5 mL)
was added, and the resulting solution was washed with
hexanes (3 × 10 mL). The aqueous phase was then
neutralized with 10% NaOH and extracted with Et2O (2 × 10
mL). The combined organic layers were washed with brine
(10 mL), dried over MgSO4, and concentrated to afford the
product 9.
1-Acetyl-2-phenyl-2,3-dihydroquinolin-4 (1H)-one (9a)
1H NMR (400 MHz, CDCl3): d = 2.43 (3 H, s), 3.22–3.28 (1
H, m), 3.35–3.40 (1 H, m), 6.47 (1 H, br), 7.15–7.22 (7 H,
m), 7.44–7.48 (1 H, m), 7.93 (1 H, d, J = 7.6 Hz). 13C NMR
(100 MHz, CDCl3): d = 193.1, 170.0, 141.7, 137.9, 134.3,
128.5, 127.5, 127.2, 126.7, 126.0, 125.4, 125.0, 54.6, 42.5,
23.3. IR (film): nmax = 1693, 1682, 1663, 1601, 1461, 694
cm–1. HRMS: m/z calcd for C17H15NO2: 265.1103; found:
265.1100.
An oven-dried 50 mL round-bottomed flask was charged
with a suspension of the swollen polystyrene-supported
selenenyl bromide (Br: 0.99 mmol/g) resin (1.0 g) in dry
CH2Cl2 (20 mL). ZnCl2 (40 mol%) was added. After stirring
for 0.5 hour at r.t., substituted 2-aminochalcone 5 (5.0
mmol) was added, and the reaction was stirred for another 12
hours. The resin 3 was collected by filtration, washed with
H2O (4 × 20 mL), THF–H2O (v/v = 3:1; 2 × 20 mL), THF (2
× 15 mL), MeOH (2 × 15 mL) and CH2Cl2 (2 × 15 mL) and
dried in vacuo. To a flask containing the suspension of the
swollen resin 3 in THF (20 mL) was added 30% H2O2 aq (1.0
mL), and the mixture was stirred for 1 hour at 0 °C, followed
by 20 min at r.t. After the reaction, the mixture was filtered,
and the resin was washed with CH2Cl2 (2 × 20 mL). The
filtrate was washed with H2O (2 × 10 mL), dried over
MgSO4, and evaporated to dryness in vacuo.
1-Benzyl-2-phenyl-4-quinolone (4a)
1H NMR (500 MHz, CDCl3): d = 8.53 (1 H, d, J = 7.8 Hz),
7.56 (1 H, m), 7.45–7.26 (10 H, m), 6.98 (2 H, d, J = 7.3 Hz),
6.56 (1 H, s), 5.33 (2 H, s). 13C NMR (125 MHz, CDCl3):
d = 176.81, 155.64, 140.94, 135.98, 135.21, 132.57, 129.74,
128.98, 128.64, 128.01, 127.64, 126.65, 126.49, 125.34,
Synlett 2011, No. 5, 707–711 © Thieme Stuttgart · New York

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