The cyclisation of 2'-aminochalcones using silica-supported Yb(OTf)3 under solvent-free conditions

Article abstract of DOI:10.3184/030823409X416974

Silica-supported Yb(OTf)3 is utilised as a catalyst for the synthesis of 2-substituted dihydroquinolinones from 2'-amino chalcones in good yields. The catalyst is easily prepared and is active under solvent-free conditions and environmentally friendly con

Full text of DOI:10.3184/030823409X416974

170 RESEARCH PAPER
MARCH, 170-173
JOURNAL OF CHEMICAL RESEARCH 2009
The cyclisation of 2'-aminochalcones using silica-supported Yb(OTfh
under solvent-free conditions
Jianjun Li, Linyong Jin, Chuanming Yu and Weike SU*
Key Laboratory of Pharmaceutical
Engineering of Ministry of Education, College of Pharmaceutical
Sciences,
Zhejiang University of Technology, Hangzhou 310014, P.R. China
Silica-supported Yb(OTfb is utilised as
a
catalyst for the synthesis of 2-substituted dihydroquinolinones
from
2'-amino chalcones in good yields. The catalyst is easily prepared and is active under solvent-free conditions
and environmentally friendly conditions.
Keywords: 2'-aminochalcones, Yb(OTf)3' solventless, dihydroquinolinones
2-Substitued dihydroquinolinones display various important
pharmacological activities and can also be utilised as
valuable precursors for the synthesis of medicinally important
%
"",0
M(On)n
••
compounds.!-3 The catalysts used previously for their
synthesis are homogeneous, hazardous and corrosive acids or
bases such as H3P04 or NaOEt. They are well known for their
corrosive properties and the troublesome worknp procedure
as well as for excessive waste production.4,5 Donnelly and
his group reported that 2-substitued dihydroquinolinones
can be obtained from the cyclisation of 2'-aminochalcones
by using orthophosphoric acid in acetic acid.6 Perumal et
al. demonstrated that 2-aminochalcones can be cyclised by
using silica gel supported InCl3 as a catalyst under microwave
irradiation to give 2-aryl-2,3-dihydroquinolin-4(1H)-ones.7
In general, these procedures are associated with the use of
corrosive acid, strong alkali or long reaction times. In addition,
many of the existing procedures are of limited synthetic scope
due to low yields, the need for large amount of catalyst,
microwave activationS and specialised solvents. Therefore,
designing a novel and efficient procedure for preparation of
dihydroquinolinones has achieved synthetic importance.
During the last decade, metal triflates have been widely
used as Lewis acids in various organic syntheses.9-!2
In many cases, they are reported to be of low toxicity, high
stability, and are easy to handle and recover from water
unlike AICI3, ZnClb and TiC14!3 In continuation of our
studies on the synthesis of these heterocyclic compounds,
we report an efficient and simple method for the synthesis
of 2-substituted dihydroquinolinones from the cyclisation
of the 2'-aminochalcones and its analogues using Yb(OTf)3
as catalyst. In detailed studies of this reaction, we find that
Yb(OTf)3 impregnated on silica gel has better catalytic
properties than Yb(OTf)3 in solution. The salient features of
Yb(OTf)3 absorbed on silica gel are the rapid reaction rates,
. 0
N
H
2a
" '"
1.0
Scheme
1
absence of unwanted products, improved and operational
simplicity under conventional heating. However, to the best of
our knowledge, there is no report on the use of this catalyst in
such cyclisation reactions.
Preliminary experiments were carried out using (E)-I-(2-
aminophenyl)-3-phenylprop-2-en-l-one as a typical reactant.
In order to optimise the reaction conditions, various factors
including catalysts, solvents, reaction temperature and time
were investigated. The results are summarised in Table 1.
As shown in Table 1, we found that among organic solvents,
CH3CN was the preferred solvent for the synthesis of la
compared to other solvents under similar reaction conditions
(Table 1 entries 1-6). Secondly a higher loading of the catalyst
had no significant influence on the reaction yield, while
temperature is an important factor, when the temperature
was lowered to room temperature, the yield was lower even
after long reaction time (Table 1 entries 1-3). Thirdly the use
of silica-supported Yb(OTf)3 as catalyst under solvent-free
condition gave much better results compared to Yb(OTf)3 in
solution (Table 1 entries 1, 8). Among all the metal triflate
catalysts we used, Yb(OTf)3 was particularly effective for
this cyclisation reaction with a short reaction time and higher
yield (Table! entries 8-12). In the absence ofYb(OTf)3, there
was no reaction in solution. On the other hand, 55% yield of
la was obtained in the presence of silica gel alone (Table 1
entries 7, 13).
Table
Entry
1
The synthesis of 2-phenyl-2,3-dihydroquinolin-4(1H)-one
under different reaction conditions"
Catalyst
Loading/mol%
Solvent
Temp,rC
Time/h
Yieldb/%
1
2
3
4
5
6
7
8
Yb(OTfh
Yb(OTfh
Yb(OTfh
Yb(OTfh
Yb(OTfh
Yb(OTfh
No catalyst
Yb(OTfh-Silica
Y(OTfh-Silica
Mg(OTfh-Silica
Cu(OTfh-Silica
Sr(OTfh-Silica
Silica
5
10
5
5
5
5
0
5
5
5
5
5
0
MeCN
MeCN
MeCN
PhMe
CH3N02
MeOH
MeCN
No
No
No
No
No
Reflux
Reflux
r. t.
Reflux
Reflux
Reflux
Reflux
80
80
80
80
80
4
4
15
4
89
90
20
85
86
60
0
95
90
56
50
68
55
4
10
15
2
9
3
10
11
12
13
10
10
8
No
80
15
"All reactions were run with 1.0 mmol1a under different reaction conditions.
blsolated yields based on 1a.
* Correspondent.E-mail:suweike@zjut.edu.cn

JOURNAL OF CHEMICAL RESEARCH 2009 171
With these preliminary results in hand, in order to test
the general applicability of silica-supported Yb(OTf)3
as a catalyst for the cyclisation of 2'-aminochalcone and
its analogues, a wide range of substrates were treated as
described above. The results are summarised in Table 2. In
all cases, compounds bearing either electron-donating or
electron-withdrawing substituents underwent the reaction well
and gave the corresponding products in good yield. It could
also be concluded that aromatic substrates bearing electron-
donating substituents required a shorter reaction time with
high yields (Table 2 entries 1-13). We studied the cyclisation
of the heterocyclic or aliphatic substituted 2'-aminochalcone
analogue under similar conditions. It was found that the
corresponding 2-(thiophen- 2-y1)-2,3-dihydroquino lin-4( IH)-
oxygen in 2'-hydroxychalcones as compared to the amino
nitrogen in 2'-aminochalcone.
In summary, the present procedure using a silica-supported
Yb(OTf)3 catalyst provides an efficient synthesis of 2-
substitued dihydroquinolinones by the cyclisation of the
corresponding 2'-aminochalcones and its analogues. We
believe that this procedure will provide a better and more
practical alternative to the existing procedures for the synthesis
of 2-substitued dihydroquinolinones.
Experimental
2'-Hydroxy-chalcones and la-o were prepared according to
literature.14-16 Yb(OTt)3was prepared from Yb 03 and triflic acid.
2
Melting points were measured on a Biichi B-540 capillarymelting
point apparatusand are uncorrected.IR spectrawere recordedon a
Nicolet Aviatar-370,spectrometerusing samples as neat liquids or
as KEr discs. IH NMR and l3CNMR spectra were recorded on a
Varian400 MHz or BrokerAvanceIII (500 MHz) instrumentusing
CDCI3as the solvent,andchemicalshiftswere expressedin partsper
million(ppm)usingTMS as an internalstandard.Mass spectrawere
measuredwith a TraceFinniganDSQ.High resolutionmass spectral
(HRMS) analysis was measured on an Agilent 6210 TOF LC/MS
usingAPCI (electrosprayionisation)techniques.All spectraldata of
the productswere identicalto authenticsamples.
one 2n and 2-tert-butyl-2,3-dihydroquinolin-4(1H)-one
20
could also be obtained in high yields (Table 2 entries 14, 15).
Inspection of the data in Table 2 also shows that the use
of Yb(OTf)3 impregnated on silica gel as catalyst (Method
A) has significantly higher yields compared to using silica
gel alone (Method B). Compared with method B, we can
see that Yb(OTf)3 impregnated on silica gel as catalyst can
significantly improve the yields to 90%. This lack of reactivity
may be due to the low acidity of silica gel compared to silica-
supported Yb(OTf)3.
Based on the experimental results, a plausible mechanism
can be proposed (Scheme 3). The mechanism of this process
includes intramolecular Michael addition of amino group to
the a,13-unsaturated ketone followed by subsequent cyclisation
under the catalysis ofYb(OTf)/silica gel.
We also tried to cyclise 2'-hydroxychalcones to their
corresponding flavanones using silica-supported Yb(OTf)3
under the same reaction conditions. Disappointingly, no
product was observed even after prolonged reaction times of
2 days (Scheme 4) or an increased amount of catalyst. This
lack of reactivity may be due to the low nucleophilicity of
(0_--- Yb(OTfh
Yb(OTfh
•.
~
N
R
H' 'H
!-Yb(OTfh
o
OH
c6"'"
~=~
.lj N
R
~NJ-R
H
H
Catalyst
Scheme 3
..
~
llAN~R
80°C
H
2a-o
SiliYcab(-OsuTpfhported c6v
0
)(
•.
1
'<:::
. l j
R= Aryl,heteroary,alkyl
0
'<:::
Catalyst1: silica-supportedYb(OTfh
Catalyst2: silicagel
1.0
Scheme 2
Scheme 4
Table 2 The synthesis of 2-substituted dihydroquinolinones under solvent-free conditions
Method Be
Time/h (Yield%)b
Entry
R
Product
Method A"
Time/h (Yield/%)b
1
Ph
2a
2b
2c
2d
2e
2f
295
2 90
2 96
295
294
290
294
3 85
3 90
387
3 82
392
375
298
390
1560
1540
1542
1545
1550
2425
1070
1530
1535
1550
1553
245
2
3-MeOC6H4
4-MeOC6H4
2,4-(MeOhC
3
4
6
H
3
5
3,4-(OCH
4-N(MehC6H4
2
0)C
6
H
3
6
7
3,4-(MehC
4-02NC6H4
3-02NC6H4
3-BrC6H4
4-CIC6H4
3-FC6H4
6
H
3
2g
2h
2i
8
9
10
11
12
13
14
15
2j
2k
21
2m
2n
20
2-CIC6H4
Thiophen-2-yl
C(Meh
1535
1556
1540
"Method A: 1a-o (1.0 mmol) and silica-gel supported Yb(OTfh (0.05 mmol) were kept at 80°C for 2-3 h.
blsolated yields based on 1a-o.
eMethod B:1a-o (1.0 mmo!) and silica gel alone were kept at 80°C for 10-24 h.

172 JOURNAL OF CHEMICAL RESEARCH 2009
Preparation
procedure
of 2-substituted
dihydroquinolinones
in solvent: general
IH NMR 8: 2.27 (d, 6H, CH3 J= 3.6 Hz), 2.71 (dd, lH, J] = 3.6, J2 =
16.4 Hz), 2.84 (dd, lH, J] = 14.0, J2 = 16.0 Hz), 4.53 (br s, lH, NH),
4.65 (dd, lH, J] = 3.6, J2 = 13.6 Hz), 6.69 (d, lH, J= 8.4 Hz), 6.76
(t, lH, J= 7.2 Hz), 7.13-7.17 (m, 2H), 7.29-7.34 (m, lH), 7.85 (dd,
lH, J] = 1.2, J2 = 8.0 Hz). l3e NMR 8: 19.4, 19.8,46.4,58.1, 115.9,
118.2, 118.9, 123.9, 127.5, 127.8, 130.1, 135.3, 136.8, 137.2, 138.4,
151.6, 193.5. MS (EI): m/z (%) = 252 (18), 251 (M+, 100), 146 (73).
HRMS (EI): m/z calcd for C17H17NO:251.1310, found: 251.1310.
la (1 mmo1) was added to 2 mL of solvent such as MeCN with
Yb(OTfh (0.05 mmo1). The whole mixture was stirred in oil-bath
for the appropriate time. On completion, the solvent was evaporated
under reduced pressure, and the remainder was extracted with ethyl
acetate (2 x 10 mL). The combined organic extracts were washed
with water followed by brine and dried over anhydrous Na2S04.
Removal of solvent followed by purification on silica gel column
with a mixture of ethyl acetate: petroleum ether = 1 : 10 afforded the
corresponding products.
2-(4-nitrophenyl)-2,3-dihydroquinolin-4(1
H)-one
(2h): Yellow
solid. M.p. 200-202°C (Lit.s m.p. 192-193°C). IR (cm·I): 3364
(NH), 1678 (C=O). IH NMR 8: 2.82-2.85 (m, 2H), 4.62 (br s, NH,
lH), 4.90 (dd, lH, J] = 6.8, J2 = 10.0 Hz), 6.78 (d, lH, J= 8.4 Hz),
6.85 (t, lH, J= 7.2 Hz), 7.37-7.41 (m, lH), 7.66 (d, 2H, J= 8.8 Hz),
7.87 (d, lH, J= 8.4 Hz), 8.25 (d, 2H, J= 8.8 Hz). l3e NMR 8: 46.1,
57.9, 116.1, 119.1, 124.3, 127.5, 127.6, 135.7, 147.8, 148.3, 150.9,
191.9. MS (ESI): m/z = 267 (M+-1).
Preparation
of 2-substituted
dihydroquinolinones
under solvent
free conditions
-
general procedure,
Method A: la-o (1 mmo1)
was added to silica gel (200~300 mesh) (0.5 g) impregnated with
Yb(OTfh (0.05 mmo1). The whole mixture was ground for 5 min for
uniform mixing and was then kept in a water bath at 80°C for the
appropriate time. On completion, the reaction mixture was directly
charged on a small silica gel column and eluted with a mixture of
2-(3-nitrophenyl)-2,3-dihydroquinolin-4(1H)-one
(2i): Pale yellow
solid. M.p. 183-185°C(Lit.? m.p. 185-186°C). IR (cm·I): 3442 (NH),
1655 (C=O). IH NMR 8: 2.84-2.91 (m, 2H), 4.62(brs, lH, NH), 4.90
(dd, lH, J] = 4.8, J2 = 12.4 Hz), 6.78 (d, lH, J= 8.0 Hz), 6.82-6.86
(m, lH), 7.36-7.41 (m, lH), 7.59 (t, lH, J = 7.6 Hz), 7.80 (d, lH,
J = 8.0 Hz),7.86-7.88 (m, lH), 8.20-8.22 (m, lH), 8.38 (d, lH,
J= 2.0 Hz). l3e NMR8: 46.2, 57.7,116.0,119.1,121.6,123.4,127.6,
129.4, 130.1, 132.7, 135.6, 143.2, 148.6, 150.9, 192.0. MS (EI): m/z
(%) = 269 (7), 268 (M+, 41), 146 (100).
ethyl acetate:petro1eum ether
products in high yields.
= 1: 10 to afford the corresponding
Method B: la-o (1 mmo1) was added to silica gel (200~300 mesh)
(0.5 g). The whole mixture was stirred for 5 min for uniform mixing
and was then kept in a water bath at 80°C for the appropriate time.
On completion, the reaction mixture was directly charged on a small
silica gel column and eluted with a mixture of ethyl acetate:petro1eum
ether = 1: 10 to afford the corresponding products. The physical and
spectra data of the compounds 2a-o are as follows.
2-(3-bromophenyl)-2,3-dihydroquinolin-4(1
H)-one
(2j):
Pale
yellow solid. M.p. 123-125°C (Lit.18 m.p. 124-125°C). IR (em·I):
3330 (NH), 1660 (C=O). IH NMR 8: 2.73-2.87 (m, 2H), 4.53(br
s, lH, NH), 4.71 (dd, lH, J] = 4.4, J2 = 13.2 Hz), 6.73 (d, lH,
J= 8.0 Hz), 6.81 (t, lH, J= 6.8 Hz), 7.28-7.33 (m, lH), 7.35-7.38
(m, 2H), 7.46-7.63 (m, lH), 7.64 (s, lH), 7.86 (dd, lH, J] = 1.6,
J2 = 8.0 Hz). l3e NMR 8: 46.3, 58.0, 116.0, 118.8, 119.1, 123.0,
125.3, 127.6, 129.7, 130.6, 131.6, 135.5, 143.4, 151.2, 192.6.
MS (EI): m/z (%) = 303 (40), 301 (M+, 44),146 (100).
2-Phenyl-2,3-dihydroquinolin-4(1H)-one
(2a): Pale yellow solid.
M.p. 147-149°C (Lit.? m.p. 149-150°C). IR (cm·I): 3346 (NH), 1659
(C=O). IH NMR 8: 2.72-2.89 (m, 2H, CH2), 4.57 (br s, lH, NH),
4.72 (dd, lH, J] = 3.6, J2 = 13.6 Hz), 6.70-6.80 (m, 2H), 7.31-7.45
(m, 6H), 7.86 (dd, lH, J] = 1.2, J2 = 7.6 Hz). l3e NMR 8: 46.4, 58.4,
115.9, 118.4, 119.0, 126.6, 127.5, 128.4, 128.9, 135.3, 141.0, 151.5,
193.2. MS (EI): m/z (%) = 224 (17), 223 (M+, 98), 146 (100).
2-(3-methoxyphenyl)-2,3-dihydroquinolin-4(1H)-one
(2b): Pale
2-(4-chlorophenyl)-2,3-dihydroquinolin-4(1
H)-one
(2k):
Pale
yellow solid. M.p. 129-130°C (Lit.2 m.p. 129-131°C). IR (cm·I):
3339 (NH), 1656 (C=O). IH NMR 8: 2.74-2.90 (m, 2H), 3.82(s, 3H,
OCH3), 4.56 (br s, lH, NH), 4.71 (dd, lH, J] = 4.0, J2 = 13.6 Hz),
6.72 (d, lH, J= 8.0 Hz), 6.77-6.81 (m, lH), 6.87-6.90 (m, lH), 7.01-
7.03 (d, 2H, J= 7.2 Hz), 7.29-7.36 (m, 2H), 7.86(dd, lH, J] = 1.6,
J2 = 8.0 Hz). 13e NMR 8: 46.4, 55.3, 55.4, 112.2, 113.7, 115.9, 118.4,
118.8, 119.0, 127.6, 130.0, 135.4, 142.6, 151.5, 160.0, 193.2. MS
(ESI): m/z = 254 (M+ + 1).
yellow solid. M.p. 169-171°C (Lit.? m.p. 168°C). IR (cm·I): 3307
(NH), 1652 (C=O). IH NMR 8: 2.72-2.87 (m, 2H), 4.49(br s, lH,
NH), 4.73 (dd, lH, J] = 4.4, J2 = 13.2 Hz), 6.72 (d, lH, J = 8.0 Hz),
6.81 (dd, lH,J] = 7.6, J2= 8.0 Hz), 7.33-7.41 (m, 5H), 7.87 (d, lH, J
= 7.6 Hz). l3e NMR 8: 46.4, 57.9, 115.9, 118.7, 119.1, 127.6, 128.0,
129.2, 134.2, 135.5, 139.6, 151.3, 192.7. MS (EI): m/z (%) = 259
(33),257 (M+, 100), 146(100).
2-(4-methoxyphenyl)-2,3-dihydroquinolin-4(1H)-one
(2c): Pale
2-(3-jluorophenyl)-2,3-dihydroquinolin-4(1H)-one
(21):
Pale
yellow solid. M.p. 145-147°C (Lit.? m.p. 147°C). IR (cm·I): 3416
(NH), 1647 (C=O). IH NMR 8: 2.73 (dd, lH, J] = 3.6, J2 = 16.4 Hz),
2.86 (dd, lH, J] = 14.0, J2 = 16.8 Hz), 3.82 (s, 3H, OCH3), 4.47 (br
s, lH, NH), 4.69 (dd, lH, J] = 3.6, J2 = 13.6 Hz), 6.69 (d, lH, J = 8.4
Hz) 6.76-6.80 (m, lH) 6.90-6.94 (m, 2H), 7.30-7.39 (m, 3H), 7.87
(dd, lH, J] = 1.2, J2 = 8.0 Hz). l3e NMR 8: 46.5, 55.4, 57.9, 114.3,
115.9, 118.4, 119.0, 127.6, 127.8, 133.1, 135.3, 151.6, 159.7, 193.4.
MS (EI): m/z (%) = 254 (12), 253 (M+, 80), 146 (100).
yellow solid. M.p. 140-142°C. IR (cm·I): 3341 (NH), 1662 (C=O).
IH NMR 8: 2.73-2.86 (m, 2H), 4.60 (br s, lH, NH), 4.74 (dd, lH,
J] = 4.4, J2 = 12.8 Hz), 6.74 (d, lH, J = 8.4 Hz), 6.80 (t, lH, J = 8.0
Hz), 7.01-7.06 (m, lH), 7.18-7.22 (m, 2H), 7.33-7.39 (m, 2H), 7.86
(d, lH,J= 7.6 Hz). l3eNMR8: 46.3,58.0, 113.5 (d,J= 22 Hz), 115.3
(d, J = 20.5 Hz), 116.0, 118.7, 122.2, 127.6, 130.6 (d, J = 7.6 Hz),
135.5,143.6 (d, J= 6.1 Hz), 151.3, 161.8, 164.2, 192.7. MS (EI): m/z
(%) = 242 (17), 241 (M+, 100), 146 (88). HRMS (EI): m/z calcd for
eISH12NOF: 241.0903, found: 241.0905.
2-(2, 4-dimethoxyphenyl)-2,
3-dihydroquinolin-4(1
H)-one (2d): Pale
yellow solid. M.p. 135-137°C. IR (em·I): 3334 (NH), 1651 (C=O).
IH NMR 8: 2.83-2.85 (m, 2H), 3.81(d, 6H, OCH3 J= 5.6 Hz), 4.62
(br s, lH, NH), 5.07 (dd, lH, J] = 5.6, J2 = 10.0 Hz), 6.48-6.50 (m,
2H), 6.67-6.76 (m, 2H), 7.26-7.36 (m, 2H), 7.85 (d, lH, J= 7.6 Hz).
l3e NMR 8: 43.8, 51.0, 55.4, 98.7,104.3,116.0,117.9,119.0,121.4,
127.2, 127.5, 135.1, 151.9, 157.8, 160.6, 194.0. MS (EI): m/z (%)
= 284 (17), 283 (M+, 100), 146 (58). HRMS (EI): m/z calcd for
e17H17N03: 283.1208, found: 283.1201.
2-(2-chlorophenyl)-2,3-dihydroquinolin-4(1H)-one
solid. M.p. 145-14rC
(2m): Pale yellow
(Lit.? m.p. 146-147°C). IR (em·I): 3286 (NH),
1650 (C=O). IHNMR8: 2.77 (dd, lH,J] = 12.4,J2= 16.4Hz), 2.94 (dd,
lH, J] = 4.0, J2 = 16.4 Hz), 4.56 (br s, lH, NH), 5.26 (dd, lH, J] = 4.4,
J2 = 12.4 Hz), 6.73-7.25 (m, 2H), 7.26-7.41 (m, 4H), 7.67 (dd, lH, J] =
1.6, J2 = 7.6 Hz), 7.88 (dd, lH, J] = 0.8, J2 = 7.6 Hz). l3e NMR 8: 44.0,
54.2,116.0,118.6,119.0, 127.4, 127.5, 127.5, 129.3, 130.0, 132.7, 135.4,
138.3, 151.5, 192.8. MS (ESI): m/z = 256.4 (M+-1).
2-(benzo[ d}[ 1,3} dioxo- 5-yl)- 2,3-dihydroquinolin-4(1
H)-onel?
(2e):
2-(thiophen-2-yl)-2,
3-dihydroquinolin-4(1
H)-one19
(20):
Pale
Pale yellow solid. M.p. 131-133°C. IR (em·I): 3329 (NH), 1651 (C=O).
IHNMR8: 2.69-2.85 (m, 2H),4.52(brs, lH, NH),4.65 (dd, lH,J] =3.6,
J2= 13.2 Hz), 5.97 (s, 2H), 6.71 (d, lH, J= 8.4 Hz), 6.76-6.81(m, 2H),
6.88 (dd, lH, J] = 1.2, J2= 8.0 Hz), 6.96 (d, lH, J= 0.8 Hz), 7.31-7.35
(m, lH), 7.85 (d, lH, J= 8.0 Hz). l3e NMR 8: 46.6, 58.2,101.2,106.9,
108.4, 115.9, 118.4, 119.0, 120.1, 127.5, 134.9, 135.4, 147.6, 148.0,
151.5,193.3. MS (ESI): m/z= 268 (M++ 1).
yellow solid. M.p. 135-13rC.
IR (cm·I): 3333 (NH), 1657 (C=O).
IH NMR 8: 2.88-2.98 (m, 2H), 4.67 (br s, lH, NH), 5.04 (dd, lH,
J] = 5.6, J2 = 11.2 Hz), 6.71-6.80 (m, lH), 6.80-6.82 (m, lH), 6.98-
7.00(m, lH), 7.06 (t, lH, J= 2.4 Hz), 7.27-7.36 (m, 2H), 7.87 (dd,
lH,J] = 1.6, J2= 8.0 Hz). 13e NMR8: 47.0, 53.7,116.0,118.8,119.3,
125.0, 125.1, 126.9, 127.6, 135.4, 144.5, 150.8, 192.6. MS (EI): m/z
(%) = 230 (23), 229 (M+, 92), 228 (100),146 (100).
2-(4-(dimethylamino)phenyl)-2,3-dihydroquinolin-4(1
H)-one
(2f):
2-tert-butyl-2,3-dihydroquinolin-4(1H)-one
(20): Pale white solid.
Pale yellow solid. M.p. 182-184°C (Lit.18 m.p. 185-186°C). IR
(cm·I): 3339 (NH), 1651 (C=O). IH NMR 8: 2.73 (dd, lH, J] = 3.6,
J2 = 16.4 Hz), 2.89 (dd, lH, J] = 14.6, J2 = 24.4 Hz), 2.97 (s, 6H, CH3),
4.44 (br s, lH, NH), 4.65 (dd, lH, J] = 3.6, J2 = 14.4 Hz), 6.67 (d, lH,
M.p. 149-150°C. IR (cm·I): 3354 (NH), 1659 (C=O). IH NMR 8:
1.02 (m, 9H, CH3), 2.51(dd, lH, J] = 14.0, J2 = 16.0 Hz), 2.65 (dd,
lH, J] = 3.6, J2 = 12.0 Hz), 3.33 (dd, lH, J] = 3.6, J2 = 14.0 Hz),
4.34(br s, lH, NH), 6.68-6.74 (m, 2H), 7.26-7.32 (m, lH), 7.81 (dd,
lH, J] = 1.6, J2 = 8.0 Hz). 13e NMR 8: 25.9, 33.2, 39.5, 62.2, 115.9,
117.9, 118.8, 127.4, 135.1, 152.0, 194.7. MS (EI): m/z (%) = 204
(2), 203 (M+, 8), 146 (100). HRMS (EI): m/z calcd for Cl3H17NO:
203.1310, found: 203.1320.
J=7.6Hz),
6.75-6.79 (m, 3H), 7.30-7.34(m, 3H), 7.87 (dd, lH,J] = 1.6,
J2 = 8.0 Hz). l3e NMR 8: 40.6, 46.5, 58.0, 112.7, 115.8, 118.2, 119.0,
127.5, 127.6, 135.2, 151.7, 193.9. MS (ESI): m/z = 267 (M++ 1).
2-(3,4-dimethylphenyl)-2,3-dihydroquinolin-4(1H)-one
(2g): Pale
yellow solid. M.p. 87-89°C. IR (em·I): 3351 (NH), 1652 (C=O).

JOURNAL OF CHEMICAL RESEARCH 2009 173
7
K. Hemanth Kumar, D. Muralidharan and P.T. Perumal, Synthesis, 2004,
1,63.
K. Hemanth Kumar and P.T. Perumal, Can. J Chern., 2006, 84,1079.
W.K. Su, J.J. Li, Z.G. Zheng and Y.C. Shen, Tetrahedron Lett., 2005, 46,
6037.
We are grateful to the National Natural Science Foundation of
China (No. 20806073 and 20876147) and for financial support.
8
9
Received 4 December 2008; accepted 5 January 2009
Paper 08/0321 doi: 10.3184/030823409X416974
Published online: 6 April 2009
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13 Q. Guo, T. Miyaji, R. Hara, B. Shen and T. Takahashi, Tetrahedron, 2002,
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14 G. Litkei andA.L. Tokes, Synth. Cornrnun., 1991,21,1597.
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