One-Pot Preparation of Pyranoquinolinones by Ytterbium(III) Trifluoromethanesulfonate-Catalyzed Reactions: Efficient Synthesis of Flindersine, N-Methylflindersine, and Zanthosimuline Natural Products

Article abstract of DOI:10.1055/s-2001-17516

An efficient synthesis of pyranoquinolinones is achieved by ytterbium(III) triflate-catalyzed reaction of 4-hydroxy-2-quinolones with a variety of α,β-unsaturated aldehydes in moderate yields. This new method has been applied to the synthesis of pyranoqui

Full text of DOI:10.1055/s-2001-17516

PAPER
1851
One-Pot Preparation of Pyranoquinolinones by Ytterbium(III)
Trifluoromethanesulfonate-Catalyzed Reactions: Efficient Synthesis of
Flindersine, N-Methylflindersine, and Zanthosimuline Natural Products
O
ne-Pot Preparatio
o
n of
P
yranoq
n
uinolinonesg Rok Lee,*a Hyuk Il Kweon,a Wha Soo Koh,a Kyung Rak Min,b Youngsoo Kim,b Seung Ho Leec
a
b
c
School of Chemical Engineering and Technology, Yeungnam University, Kyongsan 712-749, Korea
College of Pharmacy, Chungbuk National University, Cheongju 361-763, Korea
College of Pharmacy, Yeungnam University, Kyongsan 712-749, Korea
Fax +82(53)8148790; E-mail: yrlee@yeungnam.ac.kr
Received 14 May 2001; revised 13 July 2001
Ytterbium(III) triflate-catalyzed reactions have become
an important method in organic synthesis.6 Recently, the
ytterbium(III) triflate-catalyzed Michael addition of b-
keto esters to a,b-unsaturated carbonyl compounds in wa-
ter and in solvent-free conditions has been reported by
Feringa7 and Kotsuki.8 However, in contrast to these pre-
vious reported results, we found that ytterbium(III) triflate
was a useful reagent for a 1,2-addition reaction to a,b-un-
saturated aldehydes. We report here a convenient and ef-
ficient one-pot synthesis of pyranoquinolinone
derivatives and pyranoquinolinone natural products using
a tandem Knoevenagel-electrocyclic reaction starting
from 4-hydroxy-2-quinolones and a variety of a,b-unsat-
urated aldehydes in the presence of ytterbium triflate.
Abstract: An efficient synthesis of pyranoquinolinones is achieved
by ytterbium(III) triflate-catalyzed reaction of 4-hydroxy-2-quino-
lones with a variety of a,b-unsaturated aldehydes in moderate
yields. This new method has been applied to the synthesis of pyra-
noquinolinone alkaloids.
Key words: pyranoquinolinone alkaloids, Yb(OTf)3, flindersine,
N-methylflindersine, zanthosimuline
Pyranoquinolinone alkaloids are widely distributed in na-
ture (Figure 1).1 They have a variety of interesting biolog-
ical activities and potential medical applications.2 They
are also used as synthetic precursors for the preparation of
other dimeric quinoline alkaloids and polyheterocycles.3
Flindersine (1) is the parent compound among the known
pyranoquinoline natural products.4 Although several syn-
thetic approaches of pyranoquinolinone derivatives have
been reported, general and efficient approaches still re-
main scarce.5 The many steps and low yields reported in
the literature5a–d for the preparation of pyranoquinolinones
have prompted our research for a better synthesis of pyra-
noquinolinone derivatives.5a–d
Starting materials, 4-hydroxy-2-quinolones 13a and 13c,
were readily prepared from isatoic anhydride by the Cop-
pola method in 50 and 77% yields, respectively.9 The oth-
er material 13b is commercially available (Figure 2).
O
O
O
O
N
O
N
R2
R3
N
O
N
O
O
O
R4 R1
8 Benzosimuline
9 Zanthosimuline
10 Huajiaosimuline
1 R1=R2=R3=R4=H Flindersine
2 R1=Me, R2=R3=R4=H N-Methylflindersine
3 R1=R3=R4=H, R2=OMe Haplamine
O
R5
4 R1=Me, R2=R3=OMe, R4=H Oricine
5 R1=Me, R2=H, R3=R4=OMe Veprisine
6 R1=Me, R2=R3=H, R4=OMe Zanthobungeanine
7 R1=CH2OAc, R2=R3=H, R4=OMe Zanthophylline
N
O
11 R5=OH Simulenoline
12 R5=OOH Peroxysimulenoline
Figure 1 Structures of some naturally occurring pyranoquinolinones alkaloids
Synthesis 2001, No. 12, 25 09 2001. Article Identifier:
1437-210X,E;2001,0,12,1851,1855,ftx,en;F04001ss.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0039-7881

1852
Y. R. Lee et al.
PAPER
1651 cm–1 (enone C=O of amide) and the expected chem-
ical shifts associated with two vinylic protons as a doublet
at 6.76 ppm (J = 9. 9 Hz) and as a doublet of doublet at
5.52 ppm (J = 9.9 and 3.3 Hz) in the 1H NMR spectrum.
In this case, only a single product was seen and no Micha-
el addition product was found. Similarly, reaction of 13a
with citral gave the desired pyranoquinolinone 15 in 40%
yield. The other similar results are summarized in the Ta-
ble. Interestingly, in the case of cyclohex-1-ene-1-carbal-
dehyde (Table, entry 4) with a ring system, the expected
pyranoquinolinone 18 was also produced in 40% yield.
These results provide a concise synthetic entry into pyra-
noquinolinone derivatives and polyheterocycles as a one-
pot reaction.
OH
N
R
O
13a R=H
13b R=Me
13c R=Bn
Figure 2 Structures of 4-hydroxy-2-quinolones 13a–c
Reaction of 13a with crotonaldehyde in refluxing acetoni-
trile for 12 hours in the presence of 10 mol% of ytterbium
triflate as a catalyst afforded pyranoquinolinone 14 in
53% yield (Scheme 1). The formation of 14 is supported
by the observation of a peak in the IR spectrum at
Table Synthesis of Pyranoquinolinone Derivatives
Entry
1
4-Hydroxy-2-quinolone
a,b-Unsaturated Aldehyde
Product
Yield (%)
40
OH
O
H
O
N
H
O
N
H
O
O
O
13a
13b
15
2
3
4
52
48
40
OH
N
O
H
O
N
O
16
OH
N
O
H
O
N
O
13b
17
OH
N
O
H
O
N
O
O
13b
18
5
42
O
H
OH
N
O
N
O
O
13c
19
Synthesis 2001, No. 12, 1851–1855 ISSN 0039-7881 © Thieme Stuttgart · New York

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One-Pot Preparation of Pyranoquinolinones
1853
ence of ytterbium triflate for 12 hours at reflux gave 9 in
55% yield (Scheme 3). Spectral data of our synthetic ma-
terial 9 are also in agreement with those reported in the lit-
erature.1c
OH
O
O
H
Yb(OTf)3
CH3CN
reflux 12h
N
H
O
N
H
O
13a
14
53%
OH
O
N
O
Scheme 1
H
N
O
Yb(OTf)3
CH3CN
reflux 12h
O
The synthesis of natural products demonstrates an inter-
esting application of this methodology. Flindersine (1)
and N-methylflindersine (2) have been primarily isolated
from Rutaceous plants, Fagara heitzii,4a Geijera balan-
sae,4b Haplophyllum saveolens,4c Atalantia rox-
burghiana,4d Micromelum minutum4e and Zanthoxylum
coco.4f In addition, N-methylflindersine (2) was isolated
from antifeedant active species,10 Fagara chalybea, F.
hostil, Xylocarpus granatum and Orixa japonica.11 The
steams and leaves of O. japonica were formerly used in
Japan as an insecticide for livestock.11 Reaction of 13a
and 13b with 3-methylbut-2-enal afforded flindersine (1)
and N-methylflindersine (2) in 50 and 57% yields, respec-
tively (Scheme 2). The spectroscopic properties of our
synthetic materials 1 and 2 agreed well with those report-
ed in the literature.5d,11
13b
9 Zanthosimuline (55%)
Scheme 3
Although the exact mechanism of the reaction is still not
clear, it is best described as shown in Scheme 4. The 4-hy-
droxy-2-quinolone (13a) first attacks aldehyde to yield
the alcohol 20, which is dehydrated on heating under acid-
ic condition to give 21. The intermediate 21 then under-
goes electrocyclic reaction to furnish cycloadduct 14.
In conclusion, the ytterbium(III) triflate-catlyzed reaction
of 4-hydroxy-2-quinolones with a,b-unsaturated alde-
hydes has been carried out in refluxing acetonitrile solu-
tion to yield the pyranoquinolinone derivatives. This new
method has been also applied to the synthesis of naturally
occurring pyranoquinolinone alkaloids such as flindersine
(1), N-methylflindersine (2) and zanthosimuline (9) in
moderate yields.
OH
O
O
H
Yb(OTf)3
CH3CN
reflux 12h
N
R
O
N
R
O
All experiments were conducted under N2. Merck precoated silica
gel plates (Art. 5554) with fluorescent indicator were used for ana-
lytical TLC. Flash column chromatography was performed using
silica gel 9385 (Merck). Melting points were determined with mi-
crocover glasses on a Fisher-Johns apparatus and are uncorrected.
1H NMR spectra were recorded on a Bruker Model ARX (300
MHz) spectrometer. IR spectra were recorded on a Jasco FTIR 5300
spectrophotometer. HRMS spectra were obtained VG-Micromass
13a R=H
1 R=H Flindersine (50%)
2 R=Me N-Methylflindersine (57%)
13b R=Me
Scheme 2
As another application of this methodology, synthesis of
zanthosimuline (9) was next examined. Zanthosimuline Autospec spectrometer.
(9), a monoterpenoid pyranoquinolinone alkaloid, has
Pyranoquinolinones 1, 2, 9, 15–19; General Procedure
been isolated from the root bark of Taiwanese Zanthoxy-
lum simulans.1c This natural product has a general cyto-
toxic activity when evaluated with a variety of cultured
human cancer cell lines and the expression of cellular
markers associated with cell differentiation in cultured
HL-60 cells.2b,12 Reaction of 13b with citral in the pres-
The appropriate 4-hydroxy-2-quinolone 13 (1.0 mmol) and a,b-un-
saturated aldehyde (2.0 mmol) were dissolved in MeCN (10 mL),
and Yb(OTf)3 (62 mg, 0.1 mmol) was added at r.t. The mixture was
refluxed for 12 h and then cooled to r.t. Removal of the solvent left
an oily residue, which was then purified by column chromatography
Yb3+
OH
O
OH
O
O
O
H
Yb(OTf)3
-H2O
N
H
O
N
H
N
H
O
13a
CH3CN
20
21
O
N
H
O
14
Scheme 4
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1854
Y. R. Lee et al.
PAPER
(EtOAc-Hexanes) on silica gel to give the pyranoquinolinone prod-
uct.
1H NMR (300 MHz, CDCl3): d = 7.86 (1 H, d, J = 8.0 Hz), 7.48 (1
H, dd, J = 8.6, 7.1 Hz), 7.26 (1 H, d, J = 8.6 Hz), 7.17 (1 H, dd,
J = 8.0, 7.1 Hz), 6.40 (1 H, s), 5.12 (1 H, m), 3.65 (3 H, s), 2.53–
1.34 (8 H, m).
2-Methyl-2,6-dihydropyrano[3,2-c]quinolin-5-one (14)
Reaction of 13a (161 mg, 1.0 mmol) with crotonaldehyde (140 mg,
2.0 mmol) in MeCN (10 mL) afforded 14 (113 mg, 53%) as a solid;
mp 121–122 °C.
1H NMR (300 MHz, CDCl3): d = 11.40 (1 H, s), 7.80 (1 H, d, J = 8.0
Hz), 7.45 (1 H, dd, J = 8.0, 7.2 Hz), 7.31 (1 H, d, J = 8.0 Hz), 7.16
(1 H, dd, J = 8.0, 7.2 Hz), 6.76 (1 H, d, J = 9.9 Hz), 5.52 (1 H, dd,
J = 9.9, 3.3 Hz), 5.15 (1 H, m), 1.50 (3 H, d, J = 6.6 Hz).
IR (KBr): 2938, 1638, 1618, 1578, 1503, 1459, 1420, 1321, 1249,
1194, 1163, 1122, 1097, 1041, 952, 755 cm–1.
HRMS: m/z (M+) Calcd for C17H17NO2: 267.1259. Found:
267.1263.
6-Benzyl-2-methyl-2,6-dihydropyrano[3,2-c]quinolin-5-one
(19)
IR (KBr): 3198, 2978, 1651, 1615, 1499, 1435, 1410, 1372, 1269,
1249, 1190, 1138, 1118, 1032, 910 cm–1.
HRMS: m/z (M+) Calcd for C13H11NO2: 213.0790. Found:
Reaction of 13c (251 mg, 1.0 mmol) with crotonaldehyde (140 mg,
2.0 mmol) in MeCN (10 mL) afforded 19 (127 mg, 42%) as a solid;
mp 157–158 °C.
1H NMR (300 MHz, CDCl3): d = 7.93 (1 H, d, J = 8.0 Hz), 7.43–
7.35 (2 H, m), 7.29–7.13 (6 H, m), 6.84 (1 H, d, J = 10.0 Hz), 5.61
(1 H, dd, J = 10.0, 3.3 Hz), 5.51 (2 H, s), 5.24 (1 H, m), 1.53 (3 H,
d, J = 6.5 Hz).
213.0787.
2-Methyl-2-(4-methylpent-3-enyl)-2,6-dihydropyrano[3,2-
c]quinolin-5-one (15)5f
Reaction of 13a (161 mg, 1.0 mmol) with citral (304 mg, 2.0 mmol)
in MeCN (10 mL) afforded 15 (118 mg, 40%) as a solid; mp 143–
144 °C (Lit.5f mp not reported).
1H NMR (300 MHz, CDCl3): d = 11.72 (1 H, s), 7.86 (1 H, d, J = 8.0
Hz), 7.47 (1 H, dd, J = 8.2, 7.1 Hz), 7.35 (1 H, d, J = 8.2 Hz), 7.17
(1 H, dd, J = 8.0, 7.1 Hz), 6.79 (1 H, d, J = 10.0 Hz), 5.48 (1 H, d,
J = 10.0 Hz), 5.08 (1 H, m), 2.20–1.66 (4 H, m), 1.60 (3 H, s), 1.53
(3 H, s), 1.48 (3 H, s).
IR (KBr): 3063, 3032, 2976, 1634,1556, 1497, 1454, 1375, 1325,
1192, 1151, 910 cm–1.
HRMS: m/z (M+) calcd for C20H17NO2: 303.1259. Found: 303.1260.
Flindersine (1)
Reaction of 13a (161 mg, 1.0 mmol) with 3-methylbut-2-enal (168
mg, 2.0 mmol) in MeCN (10 mL) afforded 1 (113 mg, 50%) as a
solid; mp 195 °C.
IR (KBr): 3161, 2969, 1651, 1601, 1564, 1499, 1433, 1414, 1362,
1277, 1184, 1128, 1117, 1076, 918 cm–1.
1H NMR (300 MHz, CDCl3): d = 11.5 (1 H, s), 7.87 (1 H, d, J = 8.1
Hz), 7.46 (1 H, dd, J = 8.2, 7.4 Hz), 7.31 (1 H, d, J = 8.2 Hz), 7.17
(1 H, dd, J = 8.1, 7.4 Hz), 6.75 (1 H, d, J = 9.9 Hz), 5.54 (1 H, d,
J = 9.9 Hz), 1.53 (6 H, s).
2,6-Dimethyl-2,6-dihydropyrano[3,2-c]quinolin-5-one (16)
Reaction of 13b (175 mg, 1.0 mmol) with crotonaldehyde (140 mg,
2.0 mmol) in MeCN (10 mL) afforded 16 (118 mg, 52%) as a solid;
mp 115–116 °C.
IR (KBr): 3152, 2975, 1651, 1630, 1599, 1499, 1433, 1411, 1361,
1278, 1132, 872 cm–1.
1H NMR (300 MHz, CDCl3): d = 7.92 (1 H, d, J = 8.0 Hz), 7.53 (1
H, dd, J = 8.5, 7.2 Hz), 7.30 (1 H, d, J = 8.5 Hz), 7.20 (1 H, dd,
J = 8.0, 7.2 Hz), 6.78 (1 H, d, J = 9.9 Hz), 5.57 (1 H, dd, J = 9.9, 3.3
Hz), 5.19 (1 H, m), 3.67 (3 H, s), 1.49 (3 H, d, J = 6.5 Hz).
N-Methylflindersine (2)
Reaction of 13b (175 mg, 1.0 mmol) with 3-methylbut-2-enal (168
mg, 2.0 mmol) in MeCN (10 mL) afforded 2 (137 mg, 57%) as a
solid; mp 80 °C.
IR (KBr): 3080, 2975, 1652, 1557, 1505, 1464, 1423, 1372, 1161,
1124, 1096, 1044, 1002, 918 cm–1.
HRMS: m/z (M+) Calcd for C14H13NO2: 227.0946. Found:
1H NMR (300 MHz, CDCl3): d = 7.93 (1 H, d, J = 8.0 Hz), 7.51 (1
H, dd, J = 8.3, 7.3 Hz), 7.28 (1 H, d, J = 8.3 Hz), 7.19 (1 H, dd,
J = 8.0, 7.3 Hz), 6.73 (1 H, d, J = 10.0 Hz), 5.51 (1 H, d, J = 10.0
Hz), 3.67 (3 H, s), 1.49 (6 H, s).
227.0948.
IR (KBr): 2976, 1645, 1505, 1464, 1418, 1360, 1325, 1211, 1154,
1123, 1092, 1044, 1005, 987, 895 cm–1.
2,3,6-Trimethyl-2,6-dihydropyrano[3,2-c]quinolin-5-one (17)
Reaction of 13b (175 mg, 1.0 mmol) with trans-2-methylbut-2-enal
(168 mg, 2.0 mmol) in MeCN (10 mL) afforded 17 (116 mg, 48%)
as a solid; mp 123–124 °C.
1H NMR (300 MHz, CDCl3): d = 7.90 (1 H, d, J = 8.0 Hz), 7.51 (1
H, dd, J = 8.3, 7.1 Hz), 7.29 (1 H, d, J = 8.3 Hz), 7.20 (1 H, dd,
J = 8.0, 7.1 Hz), 6.52 (1 H, s), 5.02 (1 H, m), 3.68 (3 H, s), 1.82 (3
H, s), 1.40 (3 H, d, J = 6.5 Hz).
Zanthosimuline (9)
Reaction of 13b (175 mg, 1.0 mmol) with citral (304 mg, 2.0 mmol)
in MeCN (10 mL) afforded 9 (170 mg, 55%) as a solid; mp 127–
128 °C.
1H NMR (300 MHz, CDCl3): d = 7.93 (1 H, d, J = 7.8 Hz), 7.52 (1
H, dd, J = 8.0, 7.5 Hz), 7.29 (1 H, d, J = 8.0 Hz), 7.20 (1 H, dd,
J = 7.8, 7.5 Hz), 6.77 (1 H, d, J = 10.0 Hz), 5.46 (1 H, d, J = 10.0
Hz), 5.07 (1 H, m), 3.67 (3 H, s), 2.09 (2 H, m), 1.90–1.66 (2 H, m),
1.60 (3 H, s), 1.52 (3 H, s), 1.46 (3 H, s).
IR (KBr): 2961, 2927, 1636, 1618, 1458, 1417, 1404, 1182, 1096,
754 cm–1.
HRMS: m/z (M+) Calcd for C15H15NO2: 241.1103. Found:
241.1103.
IR (KBr): 2970, 2926, 1651, 1570, 1502, 1464, 1420, 1362, 1325,
1209, 1163, 1123, 1096, 1076, 1044, 1003, 906 cm–1.
5-Methyl-5,8,9,10,11,11a-hexahydro-12-oxa-5-azabenzo[a]an-
thracen-6-one (18)
Reaction of 13b (175 mg, 1.0 mmol) with cyclohex-1-ene-1-carbal-
dehyde (224 mg, 2.0 mmol) in MeCN (10 mL) afforded 18 (107 mg,
40%) as a solid; mp 128–129 °C.
Acknowledgement
This work was supported by the Korea Research Foundation Grant
(KRF-99-042-F00167).
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One-Pot Preparation of Pyranoquinolinones
1855
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Synthesis 2001, No. 12, 1851–1855 ISSN 0039-7881 © Thieme Stuttgart · New York