Regioselective synthesis of pyrano[3,2-f]quinolin-2(7H)-ones and Furo[3,2-f]quinolin-2-ones

Article abstract of DOI:10.1007/PL00010318

A simple and efficient synthesis of the hitherto unreported ring systems pyrano[3,2-f]quinolin-2(7H)-one and furo[3,2-f]quinolin-2-one was accomplished via a thermal [3,3]-sigmatropic rearrangement.

Full text of DOI:10.1007/PL00010318

Monatshefte f uÈ r Chemie 131, 967±973 (2000)
Regioselective Synthesis of
Pyrano[3,2-f]quinolin-2(7H)-ones
and Furo[3,2-f]quinolin-2-ones
Krishna C. Majumdar , Safalla K. Ghosh, and Paritosh Biswasa
Ã
Department of Chemistry, University of Kalyani, Kalyani-741235, India
Summary. A simple and ef®cient synthesis of the hitherto unreported ring systems pyrano[3,2-
f]quinolin-2(7H)-one and furo[3,2-f]quinolin-2-one was accomplished via a thermal [3,3]-
sigmatropic rearrangement.
Keywords. Cyclizations; 5,6-Fused quinolones; Heterocycles; Sigmatropic rearrangement.
Introduction
Quinolone alkaloids are known to possess antimicrobial activity and marked
cytotoxicity against animal and plant tumors [1]. A novel class of 4-hydroxyqui-
nolin-2(1H)-ones has recently been described [2] as selective glycinesite NMDA
antagonists with potent in vivo activity after oral administration. However, depending
on their structural types, quinolone derivatives exhibit different activities [3].
Furo[2,3-c]quinolin-4(5H)-one and 2H-pyrano[3,2-c]quinolin-5(6H)-one derivatives
are abundantly distributed in nature [4]. A number of syntheses for these
heterocycles including those from our own work have been reported [5, 6].
Continued interest in this area prompted us to undertake the present investigation on
the thermal rearrangement of different 6-allyloxy- and prop-2-ynyloxyquinolin-
2(1H)-ones.
Results and Discussion
The starting materials 3a±e were synthesized in 70±75% yield by treating 6-hydroxy-
1
-methylquinolin-2(1H)-one (1) with different propynylic and allylic halides (2) in
re¯uxing acetone in the presence of anhydrous potassium carbonate for 10 h
Scheme 1).
A thermal [3,3]-sigmatropic rearrangement was utilized for the synthesis of the
(
pyrano- and furano-quinolones. The pyrano[3,2-f ]quinolin-2(7H)-ones 4a,b were
obtained in 60±65% yield by heating the propargyl ethers 3a,b in re¯uxing N,N-
Ã
Corresponding author
a
Present address: Department of Chemistry, Chakdaha College, Chakdaha-741222, India

968
K. C. Majumdar et al.
Scheme 1
Scheme 2
diethylaniline for 12 h (Scheme 2). There was no indication for the formation of
furanoquinolone even in the crude reaction mixture.
The formation of the pyrano[3,2-f ]quinolin-2(7H)-ones 4a,b may be rationalized
by the initial [3,3]-sigmatropic rearrangement of the propargyl ethers 3a,b to the
allenyl derivatives 5 followed by enolization, [1,5]-hydrogen shift, and electrocyclic
ring closure [7] to give the products 4a,b (Scheme 3).
The furo[3,2-f ]quinolin-2-one derivatives 9 and 11 were synthesized via two
different routes. In one route, the chloropropenyl ether 3c was heated in re¯uxing
N,N-diethylaniline for 12 h to give the corresponding chlorallyl enol 8 which was
easily cyclized to the corresponding 1,6-dimethylfuro[3,2-f ]-quinoline-2-one (9) in
Scheme 3

Synthesis of Quinolinones
969
Scheme 4
Scheme 5
80% yield when treated with 20% alcoholic potassium hydroxide for 3 h (Scheme 4).
The second approach to the synthesis of furo[3,2-f ]quinoline-2-ones 11d,e made use
of the allylic ethers 3d,e of 6-hydroxy-1-methylquinolin-2(1H)-one (1). The allylic
ethers 3d,e were heated in re¯uxing N,N-diethylaniline for 12 h to give 5-allyl-6-
hydroxy-1-methylquinolin-2(1H)-one derivatives 10d,e in 65±70% yield. These were
ꢀ
then cyclized by stirring with concentrated sulfuric acid [8] at 0±5 C for 3 h to give
11d,e in 75±80% yield. These products failed to undergo dehydrogenation upon
treatment with palladized charcoal in boiling diphenyl ether for 3 h (Scheme 5).
It may be concluded that the method described here is simple and general. 6-
Propynyloxy-quinolin-2(1H)-ones were thermally cyclized regioselectively to
pyrano[3,2-f ]quinolin-2(7H)-ones in excellent yields. 6-Allyloxy- and 6-(2-chlor-
oallyloxy)-quinolin-2(1H)-ones were thermally rearranged and subsequently
cyclized by acid and alcoholic KOH to give regioselectivity the furo[3,2-f ]-
quinolin-2-ones.
Experimental
Melting points are uncorrected. UV/Vis spectra were recorded on a Hitachi 200-20 spectrophotometer
1
(
absolute ethanol). IR spectra were run as KBr discs on a Perkin-Elmer 1330 apparatus. II NMR
spectra were measured in CDCl3 and DMSO-d6 with TMS as internal standard on a 300 MHz NMR
spectrometer (Bruker). Elemental analyses data were in accordance with the calculated values. Mass
spectra were recorded by RSIC (CDRI), Lucknow, India. Silicagel (60±120) was obtained from
Spectrochem. Extracts were dried over anhydrous Na2SO4.
General procedure for the alkylation of 6-hydroxy-1-methylquinolin-2(1H)-one
6
-Hydroxy-1-methylquinolin-2(1H)-one (1, 1.7 g, 10 mmol) was re¯uxed with the corresponding
3
alkyl halide (2, 10 mmol) in 100 cm dry acetone in the presence of 2 g anhydrous K2CO3 for 10±
3
12 h. The reaction mixture was then ®ltered, and the residue was washed with acetone ꢁ3  25 cm †.

970
K. C. Majumdar et al.
The solvent was removed, and the residual crude mass was puri®ed by column chromatography over
silica gel using benzene-ethyl acetate (3:1) as the eluent.
1-Methyl-6-(prop-2-ynyloxy)-quinolin-2-one (3a; C13H11NO2)
ꢀ
1
Yield: 75%; m.p.: 160 C; H NMR (CDCl3; ꢀ, 300 MHz): 7.55 (d, J ˆ 9:5 Hz, 1H), 7.25 (d,
J ˆ 9:5 Hz, 1H), 7.18 (dd, J ˆ 9:5; 3 Hz, 1H), 7.05 (d, J ˆ 3 Hz, 1H), 6.68 (d, J ˆ 9:5 Hz, 1H), 4.68
(
d, J ˆ 2:4 Hz, 2H), 3.64 (s, 3H), 2.48 (t, J ˆ 2:4 Hz, 1H) ppm; IR (KBr): ꢁ ˆ 2125, 1640 (CO),
�
1
1
250 cm ; UV/Vis (EtOH): ꢂmaxꢁ"† ˆ 234 (109648), 271 (14791), 352 (15488) nm; MS:
‡
m=z ˆ 213 ꢁM †.
1-Methyl-6-(1-methylprop-2-ynyloxy)-quinolin-2-one (3b; C14H13NO2)
ꢀ
1
Yield: 70%; m.p.: 162 C; H NMR (CDCl3; ꢀ, 300 MHz): 7.62 (d, J ˆ 9:5 Hz, 1H), 7.31 (d,
J ˆ 9:5 Hz, 1H), 7.26 (dd, J ˆ 9:5; 3 Hz, 1H), 7.17 (d, J ˆ 3 Hz, 1H), 6.72 (d, J ˆ 9:5 Hz, 1H), 4.90
(
dq, J ˆ 6:5; 2 Hz, 1H), 3.69 (s, 3H), 2.49 (d, J ˆ 2 Hz, 1H) 1.70 (d, J ˆ 6:5 Hz, 3H) ppm; IR (KBr):
�
1
ꢁ
ˆ 1630, 1255 cm ; UV/Vis (EtOH): ꢂmaxꢁ"† ˆ 234 (138038), 271 (19952), 352 (19055) nm; MS:
‡
m=z ˆ 227 ꢁM †.
6-(2-Chloroprop-2-enyloxy)-1-methylquinolin-2-one (3c; C13H12ClNO2)
Yield: 75%; viscous liquid; 1H NMR (CDCl3; ꢀ, 300 MHz): 7.61 (d, J ˆ 9:5 Hz, 1H), 7.32 (d,
J ˆ 9:5 Hz, 1H), 7.23 (dd, J ˆ 9:5; 3 Hz, 1H), 7.04 (d, J ˆ 3 Hz, 1H), 6.73 (d, J ˆ 9:5 Hz, 1H), 5.57
�
‡
1
(
s, 1H), 5.47 (s, 1H), 4.64 (s, 2H), 3.71 (s, 3H) ppm; IR (KBr): ꢁ ˆ 1620, 1255 cm ; UV/Vis (EtOH):
ꢂmaxꢁ"† ˆ 234 (95499), 271 (13804), 352 (13490) nm; MS: m=z ˆ 251; 249 ꢁM †.
1-Methyl-6-(prop-2-enyloxy)-quinolin-2-one (3d; C13H13NO2)
ꢀ
1
Yield: 70%; m.p.: 115 C; H NMR (CDCl3; ꢀ, 300 MHz): 7.55 (d, J ˆ 9:5 Hz, 1H), 7.25 (d,
J ˆ 9:5 Hz, 1H), 7.15 (dd, J ˆ 9:5; 3 Hz, 1H), 6.97 (d, J ˆ 3 Hz, 1H), 6.68 (d, J ˆ 9:5 Hz, 1H), 6.06
�
1
(
(
m, 1H), 5.35 (m, 2H), 4.54 (m, 2H), 3.66 (s, 3H) ppm; IR (KBr): ꢁ ˆ 1630, 1240 cm ; UV/Vis
‡
EtOH): ꢂmaxꢁ"† ˆ 234 (141254), 272 (23442), 353 (21878) nm; MS: m=z ˆ 215 ꢁM †.
6-(But-2-enyloxy)-1-methylquinolin-2-one (3e; C14H15NO2)
1
Yield: 75%; viscous liquid; H NMR (CDCl3; ꢀ, 300 MHz): 7.60 (d, J ˆ 9:5 Hz, 1H), 7.27 (d,
J ˆ 9:5 Hz, 1H), 7.20 (dd, J ˆ 9:5; 3 Hz, 1H), 7.01 (d, J ˆ 3 Hz, 1H), 6.72 (d, J ˆ 9:5 Hz, 1H), 5.82
(
m, 2H), 4.51 (d, J ˆ 6 Hz, 2H), 3.71 (s, 3H), 1.77 (d, J ˆ 6:5 Hz, 3H), ppm; IR (KBr): ꢁ ˆ 1640,
�
1
1
250 cm ; UV/Vis (EtOH): ꢂmaxꢁ"† ˆ 215 (83176), 234 (169824), 280 (23988) 354 (25119) nm;
‡
MS: m=z ˆ 229 ꢁM †.
General procedure for the rearrangement of compounds 3a±e
3
Compounds 3a±e (3mmol) were re¯uxed in 4 cm N,N-diethylaniline for 12 h. The reaction mixture
was cooled and poured into an ice cold 1:1 HCl solution. The solution was then extractd with
3
3
3
3
 25 cm CHCl3. The CHCl3 extract was washed with 3  25 cm 1:1 HCl, 3  25 cm H2O, and
dried ꢁNa2SO4†. The CHCl3 was removed, and the crude mass was then puri®ed by column
chromatography over silica gel using benzene-ethyl acetate (3:1) as the eluent.
1-Methylpyrano[3,2-f]quinolin-2(7H)-one (4a; C13H11NO2)
Yield: 65%; viscous liquid; 1H NMR (CDCl3; ꢀ, 300 MHz): 7.96 (d, J ˆ 9:5 Hz, 1H), 7.26 (d,
J ˆ 9:5 Hz, 1H), 7.17 (d, J ˆ 9:5 Hz, 1H), 7.01 (d, J ˆ 10 Hz, 1H), 6.84 (d, J ˆ 9:5 Hz, 1H), 6.12 (dt,

Synthesis of Quinolinones
971
J ˆ 10; 3:9 Hz, 1H), 4.91 (dd, J ˆ 3:9; 1:5 Hz, 2H), 3.79 (s, 3H) ppm; IR (KBr): ꢁ ˆ 1635,
�
1
1
240 cm ; UV/Vis (EtOH): ꢂmaxꢁ"† ˆ 235 (123027), 286 (36308), 363 (22909)nm; MS:
‡
m=z ˆ 213 ꢁM †.
1,7-Dimethylpyrano[3,2-f]quinolin-2(7H)-one (4b; C14H13NO2)
1
Yield: 60%; viscous liquid; H NMR (CDCl3; ꢀ, 300 MHz): 7.88 (d, J ˆ 9:5 Hz, 1H), 7.27 (d,
J ˆ 9:5 Hz, 1H), 7.17 (d, J ˆ 9:5 Hz, 1H), 7.09 (d, J ˆ 10 Hz, 1H), 6.87 (d, J ˆ 9:5 Hz, 1H), 5.89
�
1
(
m, 1H), 4.21 (m, 1H), 3.71 (s, 3H), 2.19 (d, J ˆ 4 Hz, 3H) ppm; IR (KBr): ꢁ ˆ 1645, 1250 cm
;
‡
UV/Vis (EtOH): ꢂmaxꢁ"† ˆ 235 (194984), 338 (32359) nm; MS: m=z ˆ 227 ꢁM †.
5-(2-Chloroprop-2-enyl)-6-hydroxy-1-methylquinolin-2-one (8; C13H12ClNO2)
ꢀ
1
Yield: 65%; m.p.: 230 C; H NMR (DMSO-d6; ꢀ, 300 MHz): 9.67 (s, 1H), 7.91 (d, J ˆ 9:5 Hz, 1H),
7
3
.37 (d, J ˆ 9:5 Hz, 1H), 7.21 (d, J ˆ 9:5 Hz, 1H), 6.61 (d, J ˆ 9:5 Hz, 1H), 5.20 (s, 1H), 4.91 (s, 1H),
1
�
.95 (s, 2H), 3.59 (s, 3H) ppm; IR (KBr): ꢁ ˆ 3060, 1630 cm ; UV/Vis (EtOH): ꢂmaxꢁ"† ˆ 215
‡
(
144544), 235 (169824), 281 (48978), 363 (33113) nm; MS: m=z ˆ 251; 249 ꢁM †.
6-Hydroxy-1-methyl-5-(prop-2-enyl)-quinolin-2-one (10d; C13H13NO2)
ꢀ
1
Yield: 70%; m.p.: 234 C; H NMR (DMSO-d6; ꢀ, 300 MHz): 9.46 (s, 1H), 7.93 (d, J ˆ 9:5 Hz, 1H),
7
2
.29 (d, J ˆ 9:5 Hz, 1H), 7.17 (d, J ˆ 9:5 Hz, 1H), 6.57 (d, J ˆ 9:5 Hz, 1H), 5.91 (m, 1H), 4.93 (m,
1
�
H), 3.64 (d, J ˆ 5:6 Hz, 2H), 3.57 (s, 3H), ppm; IR (KBr): ꢁ ˆ 3050, 1630 cm ; UV/Vis (EtOH):
‡
ꢂmaxꢁ"† ˆ 215 (162181), 236 (177828), 284 (56234), 353 (33884) nm; MS: m=z ˆ 215 ꢁM †.
6-Hydroxy-1-methyl-5-(1-methylprop-2-enyl)-quinolin-2-one (10e; C14H15NO2)
ꢀ
1
Yield: 65%; m.p.: 235 C; H NMR (DMSO-d6; ꢀ, 300 MHz): 9.48 (s, 1H), 8.11 (d, J ˆ 9:5 Hz, 1H),
7
2
.29 (d, J ˆ 9:5 Hz, 1H), 7.17 (d, J ˆ 9:5 Hz, 1H), 6.53 (d, J ˆ 9:5 Hz, 1H), 6.25 (m, 1H), 5.05 (m,
1
�
H), 4.35 (m, 1H), 3.57 (s, 3H), 1.42 (d, J ˆ 7:2 Hz, 3H) ppm; IR (KBr): ꢁ ˆ 3080, 1632 cm ; UV/
Vis (EtOH): ꢂmaxꢁ"† ˆ 215 (131826), 236 (131826), 283 (42658), 363 (26303) nm; MS:
‡
m=z ˆ 229 ꢁM †.
1,6-Dimethylfuro[3,2-f]quinolin-2-one (9, C13H11NO2)
3
Compound 8 (250 mg, 1 mmol) was re¯uxed in 3 cm 20% ethanolic KOH for 3 h. The solvent was
3
removed, and the residue was extracted with 3 Â 20 cm CHCl3. The combined extract was washed
3
with 3  20 cm H2O and dried ꢁNa2SO4†. After removal of the solvent, the crude mass was puri®ed
by column chromatography over silica gel using benzene-ethyl acetate (3:1) as the eluent.
ꢀ
1
Yield: 80%; m.p.: 172 C; H NMR (CDCl3; ꢀ, 300 MHz): 7.93 (d, J ˆ 9:5 Hz, 1H), 7.61 (d,
J ˆ 9:5 Hz, 1H), 7.22 (d, J ˆ 9:5 Hz, 1H), 6.79 (d, J ˆ 9:5 Hz, 1H), 6.68 (s, 1H), 3.79 (s, 3H), 2.53 (s,
�
1
3
H) ppm; IR (KBr): ꢁ ˆ 1640, 1265 cm ; UV/Vis (EtOH): ꢂmaxꢁ"† ˆ 221 (60256), 317 (24547) nm;
‡
MS: m=z ˆ 213 ꢁM †.
Cyclization of compounds 10d,e
3
ꢀ
Compounds 10d,e (1 mmol) were dissolved in 3 cm conc. H2SO4 at 0±5 C and stirred for 3 h. The
3
mixture was poured into ice-water, neutralized with Na2CO3, and extracted with 3 Â 20 cm CHCl3.
3
The combined extract was washed with 3 Â 20 cm H2O and dried (Na2SO4). The solvent was
removed, and the crude mass was puri®ed by column chromatography over silica gel using benzene-
ethyl acetate (3:1) as the eluent.

972
K. C. Majumdar et al.
5,6-Dihydro-1,6-dimethylfuro[3,2-f]quinolin-2-one (11d, C13H13NO2)
ꢀ
1
Yield: 80%; m.p.: 190 C; H NMR (CDCl3; ꢀ, 300 MHz): 7.53 (d, J ˆ 9:5 Hz, 1H), 7.15 (d,
J ˆ 9:5 Hz, 1H), 7.02 (d, J ˆ 9:5 Hz, 1H), 6.73 (d, J ˆ 9:5 Hz, 1H), 5.08 (m, 1H), 3.70 (s, 3H), 3.52
(
dd, J ˆ 15:6; 8:9 Hz, 1H), 2.99 (dd, J ˆ 15:6; 7:5 Hz, 1H), 1.52 (d, J ˆ 6:5 Hz, 3H) ppm; IR (KBr):
�
1
ꢁ
ˆ 1640, 1250 cm ; UV/Vis (EtOH): ꢂmaxꢁ"† ˆ 216 (131826), 238 (165959), 284 (51286), 372
‡
(
26915)nm; MS: m=z ˆ 215 ꢁM †.
5,6-Dihydro-1,5,6-trimethylfuro[3,2-f]quinolin-2-one (11e, C14H15NO2)
1
Yield: 75%; viscous liquid; H NMR (CDCl3; ꢀ, 300 MHz): 7.65 (d, J ˆ 9:5 Hz, 1H), 7.15 (d,
J ˆ 9:5 Hz, 1H), 7.03 (d, J ˆ 9:5 Hz, 1H), 6.74 (d, J ˆ 9:5 Hz, 1H), 4.90 (quintet, J ˆ 6:5 Hz, 1H),
3
.71 (s, 3H), 3.55 (quintet, J ˆ 7:2 Hz, 1H), 1.52 (d, J ˆ 6:5 Hz, 3H), 1.19 (d, J ˆ 7:2 Hz, 3H) ppm;
�
1
IR (KBr): ꢁ ˆ 1650, 1260 cm ; UV/Vis (EtOH): ꢂmaxꢁ"† ˆ 215 (144544), 238 (181970), 283
‡
(
60256), 371 (33113) nm; MS: m=z ˆ 229 ꢁM †.
Attempted dehydrogenation of compound 11d,e
3
Compound 11d,e (0.5 mmol) was re¯uxed with 25 mg 10% Pd/C in 4 cm diphenyl ether for 3 h. No
change was observed as evidenced from TLC of the reaction mixture, co-TLC with an authentic
sample of 11, and an IR spectrum superimposable with that of starting material.
Acknowledgements
We thank CSIR (New Delhi) for ®nancial assistance. S. K. Ghosh and P. Biswas are grateful to CSIR
(
New Delhi) for fellowships.
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Synthesis of Quinolinones
973
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Received March 7, 2000. Accepted May 4, 2000