An expedient synthesis of pyrrolo[3,2,1-ij]quinoline-1,2-diones via intramolecular friedel-crafts cyclization protocol

Full text of DOI:10.1002/bkcs.10539

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DOI: 10.1002/bkcs.10539
BULLETIN OF THE
H. R. Moon et al.
KOREAN CHEMICAL SOCIETY
An Expedient Synthesis of Pyrrolo[3,2,1-ij]quinoline-1,2-diones
via Intramolecular Friedel–Crafts Cyclization Protocol
*
Hye Ran Moon, Su Yeon Kim, Jin Woo Lim, and Jae Nyoung Kim
Department of Chemistry and Institute of Basic Science, Chonnam National University, Gwangju 500-757,
Korea. *E-mail: kimjn@chonnam.ac.kr
Received April 15, 2015, Accepted July 17, 2015, Published online September 28, 2015
Keywords: Pyrrolo[3,2,1-ij]quinoline-1,2-diones, Intramolecular Friedel–Crafts reaction,
Morita–Baylis–Hillman bromides, Isatins
The pyrrolo[3,2,1-ij]quinolines and their reduced or oxidized
derivatives have received much attention due to their diverse
biological functions including analgesic, anti-inflammatory,
anti-epileptic, and anticancer activities.1–3 In spite of the
broad applicability and rising interest from synthetic chemists,
the reported methods for the preparation of pyrrolo[3,2,1-ij]
quinolines are rather scarce.1–3 Recently, Skropeta and co-
workers reported the synthesis of pyrrolo[3,2,1-ij]quinoline-
1,2-diones via a palladium-catalyzed C7-N annulation of 7-
bromo-N-substituted isatins (Scheme 1, Eq. 1).2a However,
the yields were very low (8–39%). France et al. reported
the synthesis of pyrrolo[3,2,1-ij]quinolin-4-ones via an
In(OTf )3-mediated intramolecular Friedel–Crafts (IMFC)
approach (Scheme 1, Eq. 2).2b
withdrawing carbonyl group. To the best of our knowledge,
there is no report on inter- and intramolecular Friedel–Crafts
alkylation of isatins.
The starting materials 3a–f were prepared from Morita–
Baylis–Hillman (MBH) bromides 1 and isatins 2 in the pres-
ence of K2CO3 in CH3CN at room temperature, as shown in
Scheme 2.6,7 The yields of 3a–f were good (83–89%).
Initially, we examined the IMFC reaction of 3a in polypho-
sphoric acid (PPA)8 at 90 ꢀC. To our delight, pyrrolo[3,2,1-ij]
quinoline-1,2-dione 4a was obtained in good yield (68%)
along with Friedel–Crafts acylation product 5a in low yield
(15%). Compound 4a was formed diastereoselectively, and
the relative stereochemistry between the substituents at 5-
and 6-positions would be a trans relationship, as France and
co-workers reported in a similar IMFC reaction.2b On expo-
sure of 4a to PPA for a long time, a slow decomposition to
intractable polar compounds was observed. The decomposi-
tion was accelerated at elevated temperature (120 ꢀC) in
PPA presumably by the cleavage of the amide bond of the isa-
tin moiety. The 6,5,6-tricyclic ring system of 4a was some-
what strained,2a,c thus an amide bond cleavage of the isatin
moiety could proceed under the acidic conditions.9 The reac-
tion of 3a in the presence of H2SO4 (5.0 equiv) in 1,2-
dichloroethane (reflux, 2 h) was ineffective. The formation
of 4a was observed on TLC; however, both 3a and 4a were
decomposed rapidly to intractable polar compounds. The
use of CH3SO3H and AlCl3 were also ineffective.
During our recent interest in IMFC reactions4 and the chem-
ical transformations of isatin derivatives,5 we reasoned out
that pyrrolo[3,2,1-ij]quinoline-1,2-diones could be prepared
via an IMFC approach as shown in Scheme 1 (Eq. (3)). We
expected that the IMFC reaction would proceed under suitable
reaction condition although the benzene ring of isatin moiety
is deactivated because of the presence of an electron-
O
O
Pd(0), 17%
Skropeta
O
O
R
(1)
N
N
Br
Ph
Ph
Ar
Thus, the IMFC reactions of 3b–f were carried out in PPA
(90 ꢀC), and the results are summarized in Table 1. The reac-
tions of 3b (entry 2), 3e (entry 5), and 3f (entry 6) showed
R
In(OTf)3
France
N
N
(2)
(3)
O
O
O
X
Ar
COOMe
O
O
COOMe
K2CO3 (1.2 equiv)
CH3CN, rt, 18 h
O
X
COOMe
+
Ar
N
O
1
O
4
N
H
Ar
3
Br
O
3a (87%): 1a + 2a
3b (89%): 1a + 2b
3c (86%): 1a + 2c
3d (83%): 1a + 2d
3e (87%): 1b + 2a
3f (84%): 1c + 2a
O
2a-d
PPA/heating
This work
1a-c
H
COOMe
N
1
N
3
3a-f
7
2a: X = H
6
Ph
1a: Ar = C6H5
1b: Ar = 4-ClC6H4
1c: Ar = 4-MeC6H4
2b: X = Me
2c: X = Cl
2d: X = OMe
Ph
5
H
COOMe
COOMe
Scheme 1. Synthesis of pyrrolo[3,2,1-ij]quinoline.
Scheme 2. Preparation of starting materials.
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Table 1. Synthesis of pyrrolo[3,2,1-ij]quinolines 4a-4f.a
5-methoxyisatin derivative 3d (entry 4), and compound 4d
wasobtained inlowyield(42%). TheFriedel–Craftsacylation
products 5b (entry 2) and 5e (entry 5) were isolated in low
yields; however, 5c, 5d, and 5f could not be isolated in appre-
ciable amount.
Time
Entry Substrate (h)
Products (%)
O
O
As a next entry, we prepared 3g–j by the alkylation of isa-
tins 2a–d with cinnamyl bromide, as shown in Scheme 3. The
reactions of 3g–j under the standard condition (PPA, 90 ꢀC)
afforded 4g–j in good to moderate yields (41–81%). As we
observed for the synthesis of 4c and 4d (entries 3 and 4 in
Table 1), the yields of 4i and 4j were relatively low compared
to the other products 4g and 4h.
In contrast to N-cinnamyl derivatives 3g–j, unfortunately,
the reactions of N-(but-2-enyl)isatin (3k) and N-(3-methylbut-
2-enyl)isatin (3l) failed to afford the corresponding IMFC
reaction products, as shown in Scheme 4. Under the typical
reaction condition, hydration products 6a and 6b were formed
in good yields (87 and 86%, respectively). The reactions of
3k and 3l in PPA at elevated temperature (120 ꢀC, 4 h) showed
complete decomposition to intractable polar compounds.
5-Benzylidenepyrrolo[3,2,1-ij]quinoline-1,2,6-trione
derivative 5a could be synthesized as a major product by using
the carboxylic acid derivative of 3a, as shown in Scheme 5.
Base hydrolysis of 3a afforded 7 in good yield (94%), and
O
O
N
N
1
3a
3b
3c
3d
4
4
9
2
Ph
O
COOMe
4a (68)
Ph
5a (15)
O
O
Me
Me
O
O
N
N
2
Ph
O
COOMe
4b (62)
Ph
O
5b (14)
O
Cl
Cl
O
O
3b
N
N
Ph
4c
O
COOMe
(38)
d
Ph
5c
(-)
O
O
MeO
O
MeO
O
4c
N
N
O
O
Ph
O
X
cinnamyl bromide
K2CO3 (1.2 equiv)
DMF, rt,12h
X
COOMe
4d (42)
O
Ph
5d (-)d
O
N
PPA
2a-d
N
90 °C,2 h
O
O
(4 h for 4i)
Ph
Ph
O
O
4g-j
N
N
3g-j
5
6
3e
3f
4
4
4g: X = H (77%)
3g: X = H (94%)
3h: X = Me (81%)
3i: X = Cl (93%)
O
4h: X = Me (81%)
4i: X = Cl (41%)
4j: X = OMe (55%)
COOMe
4e (63)
Cl
5e (12)
3j: X = OMe (88%)
Cl
Scheme 3. Synthesis of pyrrolo[3,2,1-ij]quinolines 4g-j.
O
O
O
O
O
O
N
N
O
O
O
COOMe
4f (70)
PPA
N
N
Me
5f (-)d
R
90 °C, 2 h
R
HO
Me
Me
Me
a Substrate 3 (0.5 mmol) was used in PPA (1.0 g) at 90 ꢀC for given time.
b Compound 3c (9%) was recovered.
6a (R = H, 87%)
6b (R = Me, 86%)
3k (R = H)
3l (R = Me)
c Compound 3d (12%) was recovered.
dCompounds 5c, 5d and 5f were not isolated in appreciable amounts.
Scheme 4. Trials of IMFC reaction of 3k and 3l.
O
similar reactivity as that of 3a, and the corresponding products
4b, 4e, and 4f were obtained in good yields (62–70%). How-
ever, the reaction of 5-chloroisatin derivative 3c (entry 3)
showed somewhat sluggish reactivity, and 4c was obtained
in low yield (38%) for 9 h. When we increased the reaction
time, the yield of 4c decreased because of decomposition
to polar side products. The situation was similar for
KOH (3.0 equiv)
THF/H2O (2:1)
O
PPA
5a (74%)
3a
N
rt, 3 h (94%)
90 °C, 3h
Ph
H
COOH
7
Scheme 5. Selective synthesis of 5a.
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the IMFC reaction of 7 gave 5a as the sole product (74%). The
corresponding Friedel–Crafts alkylation product was not
formed in the reaction, and the result showed that Friedel–
Crafts acylation is more effective than the alkylation with
the carboxylic acid derivative 7.
In summary, the first successful IMFC cyclization of N-
cinnamylisatin derivatives in PPA provided pyrrolo[3,2,1-ij]
quinoline-1,2-diones in good to moderate yields. The
electron-deficient benzene ring of isatin could be used effec-
tively in the IMFC reaction in PPA, although some restrictions
are still present.
139.44, 144.97, 156.13, 171.14, 182.07; ESIMS m/z
356 [M+ + H], 358 [M++H + 2].
Compound4d:42%; redsolid, m.p. 166–168 ꢀC;IR(KBr)
1739, 1630, 1616, 1490 cm−1; 1H NMR (CDCl3, 300 MHz) δ
3.12 (ddd, J = 6.9, 6.6 and 4.2 Hz, 1H), 3.60 (s, 3H), 3.71 (s,
3H), 3.83 (dd, J = 13.2 and 4.2 Hz, 1H), 4.01 (dd, J = 13.2 and
6.9 Hz, 1H), 4.48 (d, J = 6.6 Hz, 1H), 6.71 (d, J = 2.4 Hz, 1H),
7.02 (d, J = 2.4 Hz, 1H), 7.10–7.16 (m, 2H), 7.26–7.39 (m,
3H); 13C NMR (CDCl3, 75 MHz) δ 37.91, 43.16, 45.25,
52.52, 55.92, 108.39, 115.89, 123.63, 124.20, 127.81,
128.44, 129.03, 139.96, 140.72, 156.66, 156.77, 171.42,
183.44; ESIMS m/z 352 [M++H].
Experimental
Compound 4g: 77%; orange solid, m.p. 137–139 ꢀC; IR
(KBr) 1737, 1601, 1473, 1353 cm−1; 1H NMR (CDCl3, 300
MHz) δ 2.09–2.24 (m, 1H), 2.26–2.39 (m, 1H), 3.68–3.86
(m, 2H), 4.14 (dd, J = 7.5 and 4.5 Hz, 1H), 6.97 (t, J = 7.5
Hz, 1H), 7.08–7.18 (m, 3H), 7.26–7.41 (m, 3H), 7.44 (d, J
= 7.5 Hz, 1H); 13C NMR (CDCl3, 75 MHz) δ 29.27, 36.72,
40.60, 115.75, 123.40, 123.55, 124.48, 127.33, 128.20,
128.92, 137.55, 141.92, 147.56, 156.85, 183.87; ESIMS m/
z 264 [M+ + H]. Anal. Calcd. for C17H13NO2: C, 77.55; H,
4.98; N, 5.32. Found: C, 77.51; H, 5.13; N, 5.19.
The starting materials 3a–l were prepared according to the
reported method,5a,5b,7 and the spectroscopic data of the
unknown compounds are reported in Supporting Information.
Typical Procedure for the Synthesis of 4a and 5a. A mix-
ture of 3a (161 mg, 0.5 mmol) and PPA (1.0 g) was heated to
90 ꢀC for 4 h. After the usual aqueous extractive work-up and
column chromatographic purification process (hexanes/
CH2Cl2/Et2O, 10:10:1), compounds 4a (110 mg, 68%) and
5a (22 mg, 15%) were isolated as orange solids. Other com-
pounds were synthesized similarly, and the selected spectro-
scopic data of 4a–d, 4g, 5a, and 5b are as follows:
Compound 5a: 74%; orange solid, m.p. 198–200 ꢀC; IR
(KBr) 1744, 1663, 1619, 1443 cm−1; 1H NMR (CDCl3, 600
MHz) δ 5.13 (d, J = 2.4 Hz, 2H), 7.24 (dd, J = 8.4 and 7.2
Hz, 1H), 7.42 (d, J = 7.2 Hz, 2H), 7.46–7.53 (m, 3H), 7.78
(dd, J = 7.2 and 1.2 Hz, 1H), 8.00 (t, J = 2.4 Hz, 1H), 8.17
(dd, J = 8.4 and 1.2 Hz, 1H); 13C NMR (CDCl3, 150 MHz)
δ 41.91, 116.39, 117.31, 124.07, 126.03, 129.02, 130.27,
130.52, 130.75, 133.75, 135.35, 140.77, 152.02, 156.82,
179.99, 181.16; ESIMS m/z 290 [M+ + H]. Anal. Calcd. for
C18H11NO3: C, 74.73; H, 3.83; N, 4.84. Found: C,
74.95; H, 4.01; N, 4.81.
Compound 4a: 68%; orange solid, m.p. 186–188 ꢀC; IR
(KBr) 1740, 1626, 1603, 1474 cm−1; 1H NMR (CDCl3, 600
MHz) δ 3.14 (ddd, J = 7.2, 6.6 and 4.2 Hz, 1H), 3.61 (s,
3H), 3.89 (dd, J = 13.2 and 4.2 Hz, 1H), 4.03 (dd, J = 13.2
and 7.2 Hz, 1H), 4.52 (d, J = 6.6 Hz, 1H), 7.02 (t, J = 7.2
Hz, 1H), 7.12–7.16 (m, 3H), 7.31 (t, J = 7.2 Hz, 1H),
7.34–7.39 (m, 2H), 7.48 (d, J = 7.2 Hz, 1H); 13C NMR
(CDCl3, 150 MHz) δ 38.05, 43.19, 44.99, 52.51, 115.60,
122.43, 123.80, 123.93, 127.78, 128.45, 129.02, 137.80,
140.07, 146.58, 156.69, 171.42, 183.18; ESIMS m/z
322 [M++H]. Anal. Calcd. for C19H15NO4: C, 71.02; H,
4.71; N, 4.36. Found: C, 70.91; H, 4.93; N, 4.18.
Compound 5b: 14%; orange solid, m.p. 196–198 ꢀC; IR
(KBr) 1737, 1672, 1623, 1490 cm−1; 1H NMR (CDCl3, 300
MHz) δ 2.40 (s, 3H), 5.09 (d, J = 2.7 Hz, 2H), 7.37–7.53
(m, 5H), 7.58 (s, 1H), 7.94 (s, 1H), 7.97 (t, J = 2.7 Hz, 1H);
13C NMR (CDCl3, 75 MHz) δ 20.92, 41.88, 116.48,
117.07, 126.32, 128.99, 130.20, 130.50, 131.54, 133.81,
134.26, 135.03, 140.53, 150.09, 156.91, 180.10, 181.39;
ESIMS m/z 304 [M++H].
Compound 4b: 62%; orange solid, m.p. 182–184 ꢀC; IR
(KBr) 1740, 1624, 1489, 1349 cm−1; 1H NMR (CDCl3, 300
MHz) δ 2.24 (s, 3H), 3.10 (ddd, J = 6.6, 6.3 and 4.2 Hz,
1H), 3.60 (s, 3H), 3.80 (dd, J = 13.5 and 4.2 Hz, 1H), 4.04
(dd, J = 13.5 and 6.6 Hz, 1H), 4.49 (d, J = 6.3 Hz, 1H), 6.96
(s, 1H), 7.09–7.16 (m, 2H), 7.26–7.40 (m, 4H); 13C NMR
(CDCl3, 75 MHz) δ 20.94, 37.78, 43.01, 45.16, 52.51,
115.63, 122.01, 124.36, 127.72, 128.43, 129.00, 133.74,
138.15, 140.33, 144.47, 156.79, 171.50, 183.44; ESIMS m/
z 336 [M+ + H]. Anal. Calcd. for C20H17NO4: C, 71.63; H,
5.11; N, 4.18. Found: C, 71.81; H, 5.30; N, 4.11.
Acknowledgments.
This research was supported by
THE Basic Science Research Program through the
National Research Foundation of Korea (NRF) funded by
the Ministry of Education, Science and Technology
(2014R1A1A2053606). Spectroscopic data were obtained
from the Korea Basic Science Institute, Gwangju branch.
Compound 4c: 38%; orange solid, m.p. 214–216 ꢀC; IR
(KBr) 1744, 1621, 1602, 1476 cm−1; 1H NMR (CDCl3, 300
MHz) δ 3.15 (ddd, J = 6.9, 6.6 and 4.2 Hz, 1H), 3.64 (s,
3H), 3.86 (dd, J = 13.5 and 4.2 Hz, 1H), 4.07 (dd, J = 13.5
and 6.9 Hz, 1H), 4.52 (d, J = 6.6 Hz, 1H), 7.10–7.17 (m,
3H), 7.31–7.44 (m, 3H), 7.47 (d, J = 1.8 Hz, 1H); 13C NMR
(CDCl3, 75 MHz) δ 37.94, 42.97, 44.79, 52.65, 116.36,
123.92, 124.11, 128.07, 128.35, 129.21, 129.72, 137.07,
SupportingInformation. Additionalsupportinginformation
is available in the online version of this article.
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Bull. Korean Chem. Soc. 2015, Vol. 36, 2773–2776
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