A facile synthesis of pyrrolo[2,3-b]quinolines via a Rh(i)-catalyzed carbodiimide-Pauson-Khand-type reaction

Article abstract of DOI:10.1039/b924301a

A new straightforward synthetic method for 2,3-dihydro-1H-pyrrolo[2,3-b] quinolin-2-ones via a [RhCl(CO)₂]₂-dppp catalyzed Pauson-Khand-type reaction of N-[2-(2-alkyn-1-yl)phenyl]carbodiimides is reported. The Royal Society of Chemis

Full text of DOI:10.1039/b924301a

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A facile synthesis of pyrrolo[2,3-b]quinolines via a Rh(I)-catalyzed
carbodiimide-Pauson–Khand-type reaction†
Takao Saito,* Naoki Furukawa and Takashi Otani‡
Received 19th November 2009, Accepted 2nd December 2009
First published as an Advance Article on the web 7th January 2010
DOI: 10.1039/b924301a
A new straightforward synthetic method for 2,3-dihydro-1H-pyrrolo[2,3-b]quinolin-2-ones via a
[RhCl(CO)2]2–dppp catalyzed Pauson–Khand-type reaction of
N-[2-(2-alkyn-1-yl)phenyl]carbodiimides is reported.
for pyrrolo[2,3-b]quinolines involved stepwise annulation strate-
Introduction
gies, e.g., cyclization of preformed substituted aminoquinolines
or 3-alkylidene-2-(phenylimino)-pyrrolidines.11 In this context,
we envisioned that the intramolecular PK-reaction of N-[2-(2-
alkyn-1-yl)phenyl]carbodiimides 4–6 (Fig. 1) would enable a facile
approach to the pyrrolo[2,3-b]quinoline framework. Herein, we
wish to report the results.
The formal [2 + 2 + 1] cocyclization of an alkyne, an alkene
and carbon monoxide by a transition metal reagent (Pauson–
Khand (PK)-type reaction) has been frequently used as a con-
vergent and atom-economical approach for the synthesis of the
cyclopentenone framework.1,2 The hetero-PK-type reaction using
a heteroalkene counterpart, such as an aldehyde, ketone or
imine, leading to g-butyrolactones or g-lactams, has also been
developed.3
Results and discussion
We have been focusing on functionalized heterocumulenes as
substrates in various ring-forming reactions4–7 and succeeded for
the first time in the stoichiometric (Mo(CO)6–DMSO)5 and cat-
alytic (Rh(I))6 carbodiimide-Pauson–Khand (PK)-type reaction
using 1 and 2 (Fig. 1), which allowed their facile transformation
into pharmaceutically important 1H-pyrrolo[2,3-b]indol-2-ones
and pyrrolo[2,3-b]pyrrolinones. Indeed, Mukai et al. reported
the synthesis of ( )-physostigmine, ( )-flustramide B, and ( )-
flustramines B and E by the Co2(CO)8-catalyzed PK reaction of o-
alkynylphenylcarbodiimides 1.8 We further demonstrated the first
Carbodiimides 4–6 were prepared as outlined in Scheme 1:
(a) addition of lithium acetylide to 2-azidobenzaldehyde or 1-
(2-azidophenyl)ethanone, (b) hydrogenolysis with triethylsilane
and trifluoroacetic acid, or (b¢) O-methylation, (c) conversion
to iminophosphorane (Staudinger reaction), and (d) aza-Wittig
reaction with isocyanates.
=
C S bond-involved PK cyclocarbonylation of o-alkynylphenyl
isothiocyanates 3 as substrates to give thieno[2,3-b]indol-2-ones.7
Fig. 1
Scheme 1 Reagents and conditions: (a) R C CLi, -78–0 ◦C, THF;
1
≡
(b) Et3SiH, CF3CO2H, CH2Cl2, 0 ◦C; (b¢) MeI, NaH; (c) PPh3, CH2Cl2;
The pyrrolo[2,3-b]quinoline core is often found in biologically
active compounds such as blebbistatin (myosin II inhibitor)9 and
PGP-4008 (P-gp-specific MDR modulator).10 Straightforward
and efficient synthetic methods for such an important heterocyclic
system are always desired. Hitherto-reported synthetic methods
(d) R2NCO.
Initially, a brief screening of rhodium catalysts for the catalytic
PK reaction was carried out using 4a (Table 1).12 The reaction
in the presence of [RhCl(CO)dppp]2,13 prepared in situ from
[RhCl(CO)2]2 (5 mol%) and 1,3-bis(diphenylphosphino)propane
(dppp, 11 mol%) under an atmospheric pressure of carbon
monoxide13 in a gently refluxing toluene solution, provided
pyrrolo[2,3-b]quinoline 15a, a formal [1,3]-H migrated product
of the PK product 16a, in 26% yield along with unreacted 4a
(65%) (entry 1). When the reaction was carried out in refluxing
xylene, 15a was obtained in 41% yield along with recovered 4a
(47%) (entry 2). Increasing the amount of catalyst to 7 mol%
Department of Chemistry, Faculty of Science, Tokyo University of
Science, Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan. E-mail:
tsaito@rs.kagu.tus.ac.jp; Fax: +81 3 5261 4631; Tel: +81 3 5228 8254
† Electronic supplementary information (ESI) available: Detailed experi-
mental procedures, characterization data, and H and 13C NMR spectra
1
for all new compounds. See DOI: 10.1039/b924301a
‡ Present address: Functional Elemento-Organic Chemistry Unit Ad-
vanced Science Institute, RIKEN, 2-1, Hirosawa, Wako-shi, Saitama 351-
0198 Japan; E-mail: t-otani@riken.jp; Fax: +81 48 462 4995
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Table 1 Optimization of the Rh(I)-catalyzed Pauson–Khand reaction of
alkynyl carbodiimide 4a
Ph) are also good substrates for the Rh(I)-catalyzed PK reactions
(entries 13–16). t-Butyldimethylsilylalkynyl carbodiimides 4q–t
(R1 = TBS) were transformed to the corresponding pyrroloquino-
lines 15q–t without elimination of the TBS group in moderate
to good yields (entries 17–20), while both trimethylsilylalkyne
carbodiimide 4u (R1 = TMS) and triethylsilylalkyne carbodiimide
4v (R1 = TES) were converted to the 3-unsubstituted pyrrolo[2,3-
b]quinolin-2-one 15u (27% and 70% yield, respectively) via
elimination of the TMS or TES group under these conditions
(Scheme 2).
Yield (%)
Entry Rh(I)-catalyst (mol%)
Solvent Time/h 15a 4a (s.m.)
1
2
3
4
5
[RhCl(CO)(dppp)]2 (5)
[RhCl(CO)(dppp)]2 (5)
[RhCl(CO)(dppp)]2 (7)
[RhCl(CO)2]2 (5)
Toluene 4.0
Xylene 3.0
Xylene 2.5
Xylene 2.5
Xylene 2.0
26
41
80
66
72
65
47
—
—
—
[RhCl(CO)2]2 (7)
Table 2 Rh(I)-catalyzed Pauson–Khand reactions of 4
Scheme
2
Synthesis of 3-unsubstituted-1H-pyrrolo[2,3-b]quinolin-2-
(3H)-one.
Next, we examined the catalytic PK reactions of alkynyl car-
bodiimides 5a–h bearing a methyl group on the benzylic position
(Table 3). Carbodiimides 5a and 5b reacted more smoothly
than the corresponding methylene-linked compounds 4e and 4h
(Table 3, entries 1 and 2 vs. Table 2, entries 5 and 8), and the
expected 4-methyl-1H-pyrrolo[2,3-b]quinolin-2(3H)-ones 17a and
17b were obtained in 52 and 61% yields, respectively. Interestingly,
when t-butyl alkynyl carbodiimides 5c and 5d were subjected to
the reaction in the absence of dppp, dihydroquinolines 18a (58%)
and 18b (75%) were obtained as major products along with a
small amount of quinolines 17c (8%) and 17d (9%), respectively
(entries 3 and 4). The reactions of phenylalkynyl carbodiimides
5e and 5f (R1 = Ph) proceeded sluggishly to afford 17e and 17f,
respectively, in 38% yields (entries 5 and 6). Meanwhile, TBS-
alkynyl carbodiimides 5g and 5h were good substrates for the
Entry
4
R1
R2
dppp
Time/h
15, Yield (%)b
a
1
2
3
4
5
6
7
8
4a
4b
4c
4d
4e
4f
4g
4h
4i
Pent
Pent
Pent
Pent
Me
Me
Me
Pr
+
+
2.5
1
2
2
7
2
6
3
0.5
0.5
0.5
0.5
4
15a (80)
15b (70)
15c (75)
15d (33)
15e (51)
15f (35)
15g (58)
15h (41)
15i (84)
15j (85)
15k (83)
15l (84)
15m (63)
15n (71)
15o (66)
15p (70)
15q (75)
15r (58)
15s (33)
15t (52)
a
Bn
Cy
Ph
Pr
Bn
Cy
Ph
Pr
Bn
Cy
Ph
Pr
Bn
Cy
Ph
Pr
—
a
+
+
a
—
—
a
Me
+
9
t-Bu
t-Bu
t-Bu
t-Bu
Ph
Ph
Ph
—
—
—
—
10
11
12
13
14
15
16
17
18
19
20
4j
4k
4l
a
4m
4n
4o
4p
4q
4r
4s
4t
+
+
+
+
Table 3 Rh(I)-catalyzed Pauson–Khand reactions of 5
a
2
a
0.5
1.5
1.5
1
3
3
a
Ph
TBS
TBS
TBS
TBS
—
—
—
—
Bn
Cy
Ph
a dppp (15 mol%) was added. b Isolated yield.
substantially improved the yield of 15a (80%), with substrate 4a
14
totally consumed (entry 3). The catalyst [RhCl(CO)2]2 was also
found to be effective for the present reaction under these optimized
reaction conditions (entry 5). The catalytic systems [RhCl(CO)2]2
(5 mol%) + Ph3P (11 mol%) + AgBF4 (11 mol%)15 and Ru3(CO)12
(5 mol%)16 turned out to be ineffective in this PK reaction of 4a.
Under the optimized conditions (Table 1, entries 3 and 5), the
catalytic PK reaction for a variety of alkynyl carbodiimides 4 was
examined (Table 2). The reaction of alkyl alkynes 4a–l (entries
1–12) proceeded smoothly and gave the corresponding products
15a–l in moderate to high yields. The reaction rates and the yields
of cycloadducts 15a–l tend to increase with an increase in the steric
bulk at the alkyne terminus: t-Bu (entries 9–12) > n-Pent (entries
1–4) > Me (entries 5–8). Phenylalkynyl carbodiimides 4m–p (R1 =
Yield (%)b
Entry
5
R1
R2
dppp
Time/h
17
18
a
1
2
3
4
5
6
7
8
5a
5b
5c
5d
5e
5f
Me
Me
t-Bu
t-Bu
Ph
Ph
TBS
TBS
Pr
Ph
Pr
Ph
Pr
Ph
Pr
Ph
+
+
2
1
0.5
1.5
4
2
1
1.5
17a (52)
17b (61)
17c (8)
—
—
18a (58)
18b (75)
—
—
—
—
a
—
—
17d (9)
a
+
+
17e (38)
17f (38)
17g (75)
17h (72)
a
5g
5h
—
—
a dppp (15 mol%) was added. b Isolated yield.
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1
PK reaction, and gave quinolines 17g and 17h in high yields,
respectively (entries 7 and 8). Although 5g and 5h also contain
a bulky TBS group on the alkyne terminus just like t-butylalkynyl
carbodiimides 5c and 5d, dihydroquinolines 18 were not obtained,
nor detected even at earlier stage of the reaction, in contrast to the
reactions of 5c and 5d (entries 3 and 4).
Finally, alkynyl carbodiimides 6a,b, which contain a benzylic
quaternary carbon center (Scheme 3), were subjected to the cat-
alytic PK reaction. The reaction of methylalkynyl carbodiimide 6a
was completed within 2 h to afford expected pyrroloquinoline 19a
in 68% yield. Meanwhile, the reaction of t-butylalkynyl carbodi-
imide 6b yielded a cycloisomerized product, 2-t-butyl-3-methoxy-
3-methyl-1-propyl-1,3-dihydro-azeto[2,3-b]quinoline (20) in 48%
yield. No formation of 20 was observed in the absence of the Rh-
catalyst in refluxing xylene. The formation of 20 instead of 19b
can be attributed to the difficulty of the CO-inserted metallacycle
formation, due to steric reasons between the t-butyl group and the
substituents (Me, MeO, Ar) on the quaternary carbon (Scheme 4).
a Horiba FT-710 model spectrophotometer. H and 13C NMR
spectral data were obtained with a Bruker Avance-600, a JEOL
JNM-EX 500, or a JEOL JNM-EX 300 instrument and chemical
shifts are reported in ppm down field from tetramethylsilane
(TMS) using an internal standard of TMS or CDCl3. HRMS
analysis were performed on a Bruker Daltonics microTOF. 2-
Azidobenzaldehyde17 and 1-(2-azidophenyl)-ethanone18 were pre-
pared according to the reported method.
Typical procedure for preparation of alcohols 7 and 8
1-(2-Azidophenyl)but-2-yn-1-ol
(7b). n-Butyllithium/n-
hexane solution (1.5 M, 27.8 mL, 44.0 mmol) was added to
a solution of 1-bromo-1-propene (2.60 mL, 30.4 mmol) in
THF (20 mL) at -78 ◦C. After stirring for 2 h, a solution of
2-azidobenzaldehyde (2.94 g, 20.0 mmol) in THF (10 mL) was
added, and the mixture was stirred for a further 1 h. The mixture
was quenched with saturated aqueous ammonium chloride
and extracted with dichloromethane. The organic extracts were
washed with brine, dried over anhydrous magnesium sulfate,
and evaporated. The residue was purified by silica gel column
chromatography (ethyl acetate–hexane = 1 : 4) to give the
alcohol 7b (3.72 g, 19.9 mmol, 99%) as a yellow solid. mp
50.0–51.5 ◦C. IR (KBr/cm-1): 3301, 2291, 2129, 1581, 1303, 748.
1H-NMR (300 MHz, CDCl3, d): 7.65 (dd, J = 1.7, 8.0 Hz, 1H),
7.36 (ddd, J = 1.5, 7.2, 7.8 Hz, 1H), 7.20–7.12 (m, 2H), 5.64–5.56
(m, 1H), 2.80–2.68 (br, 1H), 1.90 (d, J = 2.2 Hz, 3H). 13C-NMR
(75 MHz, CDCl3, d): 137.15 (C), 132.05 (C), 129.50 (CH), 128.22
(CH), 124.99 (CH), 118.16 (CH), 83.03 (C), 78.17 (C), 60.60 (CH),
3.70 (CH3). HRMS-ESI (m/z): [M+Na]+ calcd for C10H9N3NaO,
210.0638; found, 210.0633. Anal calcd for C10H9N3O: C 64.16, H
4.85, N 22.45, found: C 64.20, H 5.23, N 22.06.
Scheme 3 Rh(I)-catalyzed Pauson–Khand reactions of 6.
2-(2-Azidophenyl)pent-3-yn-2-ol
(8a). Yellow
oil.
IR
(neat/cm-1): 3055, 2129, 1473, 1265, 741. H-NMR (500 MHz,
CDCl3, d): 7.67(dd, J = 1.4, 7.8 Hz, 1H), 7.34 (ddd, J = 1.4, 7.7,
7.7 Hz, 1H), 7.19 (d, J = 7.9 Hz, 1H), 7.14 (ddd, J = 1.2, 7.6,
7.6 Hz, 1H), 3.82 (s, 1H), 1.90 (s, 3H), 1.86 (s, 3H). 13C-NMR
(125 MHz, CDCl3, d): 136.58 (C), 135.67 (C), 128.96 (CH), 127.05
(CH), 124.91 (CH), 119.12 (CH), 82.21 (C), 80.83 (C), 69.14 (C),
30.44 (CH3), 3.75 (CH3). HRMS-ESI (m/z): [M+Na]+ calcd for
C11N11N3NaO, 224.0794; found, 224.0789.
1
Typical procedure for preparation of 9 and 10
Scheme 4 A plausible reaction pathway.
1-Azido-2-(but-2-ynyl)benzene
(9b). Trifluoroacetic acid
(0.22 mL, 3.0 mmol) was added to a mixture of alcohol 7b
(374 mg, 2.0 mmol) and triethylsilane (0.48 mL, 3.00 mmol)
in dichloromethane (7 mL) at 0 ◦C. After stirring for 10 h
at 0 ◦C, the mixture was quenched by addition of saturated
aqueous sodium hydrogen carbonate. The mixture was extracted
with dichloromethane, washed with brine, dried over anhydrous
magnesium sulfate and evaporated. The residue was purified
by silica gel column chromatography (hexane) to give alkynyl
azide 9b (142 mg, 0.83 mmol, 41%) as a yellow solid. mp
49.5–50.5 ◦C. IR (KBr/cm-1): 2916, 2283, 2121, 1581, 1288, 748.
1H-NMR (300 MHz, CDCl3, d): 7.51 (d, J = 7.3 Hz, 1H), 7.26
(dd, J = 7.3, 7.5 Hz, 1H), 7.20–7.04 (m, 2H), 3.44 (s, 2H), 1.84
(d, J = 1.5 Hz, 3H). 13C-NMR (75 MHz, CDCl3, d): 137.45 (C),
129.57 (CH), 128.75 (C), 127.81 (CH), 124.75 (CH), 117.69 (CH),
Conclusions
In summary, we have demonstrated for the first time [RhCl(CO)2]2
(7 mol%) + dppp (15 mol%)-catalyzed PK reactions of N-[2-
(2-alkyn-1-yl)phenyl]carbodiimides for a new entry to synthetic
methods of pyrrolo[2,3-b]quinolines.
Experimental
General information
All melting points were determined on a Yanaco melting point
apparatus and are uncorrected. Infrared spectra were recorded on
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78.14 (C), 75.79 (C), 20.49 (CH2), 3.52 (CH3). HRMS-ESI (m/z):
7.80–7.67 (m, 6H), 7.55–7.47 (m, 4H), 7.45–7.35 (m, 6H), 6.79–
6.72 (m, 1H), 6.70–6.64 (m, 1H), 6.45–6.37 (m, 1H), 4.81–4.69
(m, 1H), 1.85 (dd, J = 2.4, 2.4 Hz, 3H), 1.49 (s, 3H). 13C-NMR
(125 MHz, CDCl3, d): 147.61 (C), 137.78 (C, d, J = 22.0 Hz),
132.48 (CH¥6, d, J = 9.31 Hz), 131.63 (C¥3, d, J = 99.3 Hz),
131.47 (CH¥3, d, J = 2.6 Hz), 128.50 (CH¥6, d, J = 12.2 Hz),
126.84 (CH), 126.36 (CH), 120.73 (CH, d, J = 10.1 Hz), 117.32
(CH), 84.26 (C), 75.87 (C), 27.42 (CH3), 22.89 (CH), 3.70 (CH3).
HRMS-ESI (m/z): [M+H]+ calcd for C29H27NP, 420.1876; found,
420.1867.
[M+Na]+ calcd for C10H9N3Na, 194.0689; found, 194.0691.
1-Azido-2-(pent-3-yn-2-yl)benzene (10a). Yellow oil. IR
(neat/cm-1): 3054, 2121, 1265, 741. 1H-NMR (500 MHz, CDCl3,
d): 7.59 (dd, J = 1.5, 7.7 Hz, 1H), 7.27 (ddd, J = 1.5, 7.7, 7.7 Hz,
1H), 7.14 (ddd, J = 1.2, 7.7, 7.7 Hz, 1H), 7.11 (dd, J = 1.2, 7.7 Hz,
1H), 3.99 (dq, J = 2.3, 2.4 Hz, 1H), 1.85 (d, J = 2.4 Hz, 3H),
1.37 (d, J = 7.1 Hz, 3H). 13C-NMR (125 MHz, CDCl3, d): 136.57
(C), 135.23 (C), 128.40 (CH), 127.83 (CH), 125.02 (CH), 117.95
(CH), 81.58 (C), 77.25 (C), 26.62 (CH3), 23.36 (CH), 3.60 (CH3).
HRMS-ESI (m/z): [M+Na]+ calcd for C11H11N3Na, 208.0845;
found, 208.0841.
2-(2-Methoxypent-3-yn-2-yl)-N -(triphenylphosphonylidene)-
benzenamine (14a). Yellow solid; mp 140.9–141.3 ◦C. IR
(KBr/cm-1): 3055, 2977, 2931, 2245, 1913, 1581, 1473, 1342, 1111,
1
Typical procedure for preparation of 11
741. H-NMR (500 MHz, CDCl3, d): 7.91–7.80 (m, 6H), 7.65–
7.59 (m, 1H), 7.50–7.36 (m, 9H), 6.84–6.77 (m, 1H), 6.67–6.60
(m, 1H), 6.46–6.40 (m, 1H), 3.37 (s, 3H), 2.09 (s, 3H), 1.70 (s,
3H). 13C-NMR (125 MHz, CDCl3, d): 134.11 (C, d, J = 22.2),
132.57 (CH¥6, d, J = 9.8 Hz), 132.00 (C, d, J = 9.8 Hz), 131.80
(C¥3, d, J = 99.8 Hz), 131.28 (CH¥3), 128.39 (CH¥6, d, J =
11.9 Hz), 127.49 (CH), 127.47 (CH), 122.29 (CH, d, J = 11.6
Hz), 116.29 (CH), 81.72 (C), 80.46 (C), 77.07 (C), 51.80 (CH3),
27.56 (CH3), 3.55 (CH3). HRMS-ESI (m/z): [M+H]+ calcd for
C30H29NOP, 450.1981; found, 450.1986.
1-Azido-2-(2-methoxypent-3-yn-2-yl)benzene (11a).
A solu-
tion of azide alcohol 8a (2.44 g, 12.1 mmol) in THF (5 mL)
was added to a cold (-50 ◦C) stirred suspension of 60% NaH
(726 mg, 18.1 mmol) in THF (15 mL). After stirring for 10 min,
methyl iodide (1.1 mL, 18.1 mmol) was added. The mixture was
allowed to warm to room temperature, stirred for a further 3 h
then quenched with water. The resulting mixture was extracted
with dichloromethane, dried over anhydrous magnesium sulfate,
and evaporated. The residue was purified by silica gel column
chromatography (ethyl acetate–hexane = 1 : 4) to provide methyl
ether 11a as a yellow oil (2.30 g, 88%). IR (neat/cm-1): 2931, 2121,
1481, 1296, 756. 1H-NMR (500 MHz, CDCl3, d): 7.80(dd, J = 1.5,
7.8 Hz, 1H), 7.34 (ddd, J = 1.6, 7.8, 7.8 Hz, 1H), 7.20 (dd, J =
1.1, 7.9 Hz, 1H), 7.13 (ddd, J = 1.0, 7.6, 7.6 Hz, 1H), 3.22 (s, 3H),
1.98 (s, 3H), 1.83 (s, 3H). 13C-NMR (125 MHz, CDCl3, d): 137.18
(C), 132.55 (C), 129.64 (CH), 129.13 (CH), 124.39 (CH), 119.58
(CH), 83.39 (C), 79.30 (C), 76.26 (C), 52.18 (CH3), 29.11 (CH3),
3.63 (CH3). HRMS-ESI (m/z): [M+Na]+ calcd for C12N13N3NaO,
238.0951; found, 238.0949.
Typical procedure for preparation of carbodiimides 4–6
(2-But-2-ynyl)propylcarbodiimide (4e). Propyl isocyanate
(0.16 mL, 1.66 mmol) was added to a solution of imino-
phosphorane 12b (446.0 mg, 1.10 mmol) in dichloromethane
(5 mL) at room temperature. After stirring for 10 h, the mixture
was concentrated under reduced pressure. The residue was purified
by silica gel column chromatography (ethyl acetate–hexane =
1 : 4) to give carbodiimide 4e (220.3 mg, 1.03 mmol, 94%) as a
colorless oil. IR (neat/cm-1): 2970, 2877, 2144, 1496, 1265, 1088,
1
740. H-NMR (300 MHz, CDCl3, d): 7.49 (d, J = 7.4 Hz, 1H),
Typical procedure for preparation of iminophosphoranes 12–14
7.25–7.04 (m, 3H), 3.61–3.54 (m, 2H), 3.36 (t, J = 6.8 Hz, 2H),
1.84 (dd, J = 2.6, 2.6 Hz, 3H), 1.69 (tq, J = 7.1, 7.1 Hz, 2H),
1.00 (t, J = 7.3 Hz, 3H). 13C-NMR (75 MHz, CDCl3, d): 138.33
(C), 135.20 (C), 131.11 (C), 129.02 (CH), 127.38 (CH), 124.52
(CH), 123.54 (CH), 77.75 (C), 76.38 (C), 48.48 (CH2), 24.65
(CH2), 21.17 (CH2), 11.37 (CH3), 3.56 (CH3). HRMS-ESI (m/z):
[M+H]+ calcd for C14H17N2, 213.1386; found, 213.1385.
2-(But-2-ynyl)-N-(triphenylphosphonylidene)benzenamine (12b).
Triphenylphosphine (228.7 mg, 0.82 mmol) was added to a solu-
tion of alkynyl azide 9b (135.7 mg, 0.79 mmol) in dichloromethane
(5 mL) at room temperature. After stirring for 10 h, the mixture
was concentrated under reduced pressure. The residue was purified
by silica gel column chromatography (ethyl acetate–hexane = 1 : 4)
to give iminophosphorane 12b (318.8 mg, 0.78 mmol, 99%) as a
yellow solid. mp 139.6–141.0 ◦C. IR (KBr/cm-1): 3047, 1589, 1481,
1442, 1342, 1103, 748. 1H-NMR (300 MHz, CDCl3, d): 7.84–7.68
(m, 6H), 7.55–7.35 (m, 10H), 6.78 (dd, J = 7.1, 7.1 Hz, 1H), 6.67
(dd, J = 7.1, 7.1 Hz, 1H), 6.49–6.38 (m, 1H), 3.85 (s, 2H), 1.83
(dd, J = 2.1, 2.1 Hz, 3H). 13C-NMR (75 MHz, CDCl3, d): 148.54
(C), 132.49 (CH¥6, d, J = 9.7 Hz), 131.63 (C¥3, d, J = 100.0 Hz),
131.59 (C, d, J = 21.7 Hz), 131.50 (CH¥3, d, J = 2.6 Hz), 128.49
(CH¥6, d, J = 11.9 Hz), 127.92 (CH), 126.39 (CH), 120.36 (CH, d,
J = 9.5 Hz), 117.23 (CH), 78.61 (C), 77.00 (C), 22.24 (CH2), 3.67
(CH3). HRMS-ESI (m/z): [M+H]+ calcd for C28H25NP, 406.1719;
found, 406.1718. Anal calcd for C28H24NP: C 82.94, H 5.97, N
3.45, found: C 82.56, H 6.05, N 3.43.
(2-(1-Methylbut-2-ynyl)phenyl)propylcarbodiimide (5a). Col-
orless oil. IR (neat/cm-1): 2970, 2137, 1589, 1496, 1265, 741. 1H-
NMR (500 MHz, CDCl3, d): 7.56 (dd, J = 1.5, 7.6 Hz, 1H),
7.20–7.08 (m, 3H), 4.20–4.14 (m, 1H), 3.38 (t, J = 6.8 Hz, 2H),
1.85 (d, J = 2.4 Hz, 3H), 1.71 (dt, J = 7.2, 7.2 Hz, 2H), 1.39 (d,
J = 7.0 Hz, 3H), 1.02 (t, J = 7.3 Hz, 3H). 13C-NMR (150 MHz,
CDCl3, d): 137.50 (C), 137.46 (C), 135.62 (C), 127.82 (CH), 127.36
(CH), 124.82 (CH), 123.84 (CH), 82.18 (C), 76.88 (C), 48.61 (CH2),
27.09 (CH3), 24.76 (CH2), 23.50 (CH), 11.45 (CH3), 3.64 (CH3).
HRMS-ESI (m/z): [M+Na]+ calcd for C15H18N2Na, 249.1362;
found, 249.1361.
Propyl-(2-(2-methoxypent-3-yn-2-yl))carbodiimide (6a). Col-
orless oil. IR (neat/cm-1): 2970, 2939, 2144, 1496, 1095, 756. 1H-
NMR (600 MHz, CDCl3, d): 7.74 (d, J = 7.4 Hz, 1H), 7.24 (ddd,
J = 1.5, 7.7, 7.7 Hz, 1H), 7.15 (dd, J = 1.3 7.8 Hz, 1H), 7.09 (ddd,
J = 1.3, 7.4, 7.7 Hz, 1H), 3.38 (t, J = 6.8 Hz, 2H), 3.23 (s, 3H),
2-(Pent-3-yn-2-yl)-N -(triphenylpho◦sphonylidene)benzenamine
(13a). Yellow solid; mp 144.0–144.3 C. IR (KBr/cm-1): 3062,
2916, 1589, 1481, 1350, 1103, 694. 1H-NMR (500 MHz, CDCl3, d):
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1.98 (s, 3H), 1.87 (s, 3H), 1.70 (tq, J = 7.1, 7.3 Hz, 2H), 1.01
(t, J = 7.4 Hz, 3H). 13C-NMR (150 MHz, CDCl3, d): 138.07
(C), 134.33 (C), 134.30 (C), 128.97 (CH), 128.69 (CH), 125.61
(CH), 124.02 (CH), 82.93 (C), 79.77 (C), 76.61 (C), 52.13 (CH3),
48.50 (CH2), 29.00 (CH3), 24.74 (CH2), 11.47 (CH3), 3.72 (CH3).
HRMS-ESI (m/z): [M+Na]+ calcd for C16H20N2NaO, 279.1468;
found, 279.1462.
(CH), 129.03 (CH), 127.85 (CH), 127.59 (CH), 125.57 (C), 124.59
(C), 124.25 (CH), 51.98 (CH), 44.00 (CH), 31.64 (CH2), 30.65
(CH2), 28.83 (CH2), 28.71 (CH2), 26.01 (CH2), 25.99 (CH2), 25.29
(CH2), 25.14 (CH2), 22.32 (CH2), 13.91 (CH3). HRMS-ESI (m/z):
[M+Na]+ calcd for C22H28N2NaO, 359.2094; found, 359.2097.
3-Pentyl-1-phenyl-1H-pyrrolo◦[2,3-b]quinolin-2(3H)-one (15d).
Yellow solid; mp 103.4–106.3 C. IR (KBr/cm-1): 2924, 1736,
1581, 1427, 1219, 910, 748. 1H-NMR (500 MHz, CDCl3, d): 7.91
(s, 1H), 7.87 (d, J = 8.5 Hz, 1H), 7.75 (d, J = 7.9 Hz, 1H), 7.63
(d, J = 8.1 Hz, 2H), 7.40 (dd, J = 7.8, 7.8 Hz, 1H), 7.54 (dd, J =
7.7, 7.7 Hz, 2H), 7.41 (dd, J = 7.5, 7.5 Hz, 2H), 3.73 (t, J =
6.1 Hz, 1H), 2.18–2.03 (m, 2H), 1.57–1.37 (m, 2H), 1.37–1.27 (m,
4H), 0.87 (t, J = 6.8 Hz, 3H). 13C-NMR (125 MHz, CDCl3, d):
176.69 (C), 156.56 (C), 146.59 (C), 133.33 (C), 130.89 (CH), 129.29
(CH), 128.96 (CH¥2), 128.16 (CH), 127.91 (CH), 127.58 (CH),
126.70 (CH¥2), 126.22 (C), 124.74 (CH), 124.15 (C), 44.21 (CH),
31.65 (CH2), 30.94 (CH2), 25.42 (CH2), 22.35 (CH2), 13.94 (CH3).
HRMS-ESI (m/z): [M+Na]+ calcd for C22H22N2NaO, 353.1624;
found, 353.1621.
Typical procedure for the catalytic Pauson–Khand reaction using
[Rh(CO)2Cl]2-dppp to produce 15
3-Pentyl-1-propyl-1H-pyrrolo[2,3-b]quinolin-2(3H)-one (15a)
(Table 2, entry 1). 1,2-Bis(diphenylphosphino)propane (dppp)
(28.4 mg, 0.069 mmol) was added to a stirred solution of
[Rh(CO)2Cl]2 (12.5 mg, 0.032 mmol) in p-xylene (5 mL), and the
mixture was degassed and charged with carbon monoxide. The
resulting pale yellow suspension was heated at 130 ◦C, and a
solution of carbodiimide 4a (123.7 mg, 0.462 mmol) in p-xylene
(1 mL) was added slowly. After heating at the same temperature
for 2.5 h, the mixture was evaporated. The residue was purified
by silica gel column chromatography (ethyl acetate–hexane =
1 : 10) to provide pyrroloquinoline 15a (109.6 mg, 0.370 mmol,
80%) as a yellow oil. IR (neat/cm-1): 2931, 2862, 1728, 1643,
3-Methyl-1-propyl-1H-pyrrolo[2,3-b]quinolin-2(3H)-one (15e).
◦
Yellow solid; mp 105.0–105.8 C. IR (KBr/cm-1): 2939, 2360,
1712, 1635, 1442, 1373, 1219, 957, 756. 1H-NMR (300 MHz,
CDCl3, d): 7.92 (d, J = 8.3 Hz, 1H), 7.77 (s, 1H), 7.70 (d, J =
7.8 Hz, 1H), 7.61 (ddd, J = 1.4, 7.0, 8.3 Hz, 1H), 7.38 (ddd, J =
1.0, 7.5, 7.5 Hz, 1H), 3.89 (t, J = 7.3 Hz, 2H), 3.53 (q, J = 7.2 Hz,
1H), 1.84 (tq, J = 7.4, 7.4 Hz, 2H), 1.54 (d, J = 7.5 Hz, 3H), 0.99
(t, J = 7.4 Hz, 3H). 13C-NMR (75 MHz, CDCl3, d): 177.97 (C),
156.44 (C), 146.84 (C), 129.88 (CH), 129.10 (CH), 127.67 (CH),
127.61 (CH), 125.92 (C), 125.74 (C), 124.26 (CH), 40.76 (CH2),
38.97 (CH), 20.76 (CH2), 15.33 (CH3), 11.24 (CH3). HRMS-ESI
(m/z): [M+H]+ calcd for C15H17N2O, 241.1335; found, 241.1343.
1
1581, 1450, 1219, 1088, 756. H-NMR (500 MHz, CDCl3, d):
7.92 (d, J = 8.3 Hz, 1H), 7.81 (s, 1H), 7.73 (dd, J = 0.9, 8.0 Hz,
1H), 7.62 (ddd, J = 1.4, 7.2, 8.4 Hz, 1H), 7.40 (ddd, J = 0.9, 7.4,
8.0 Hz, 1H), 3.95–3.85 (m, 2H), 3.55 (ddd, J = 1.1, 5.5, 6.7 Hz,
1H), 2.09–2.01 (m, 1H), 1.99–1.91 (m, 1H), 1.84 (tq, J = 7.4,
7.4 Hz, 2H), 1.48–1.24 (m, 6H), 0.99 (t, J = 7.5 Hz, 3H), 0.86
(t, J = 7.1 Hz, 3H). 13C-NMR (125 MHz, CDCl3, d): 177.48
(C), 156.94 (C), 146.91 (C), 130.23 (CH), 129.19 (CH), 127.75
(CH¥2), 125.95 (C), 124.63 (C), 124.34 (CH), 44.15 (CH), 40.88
(CH2), 31.66 (CH2), 30.58 (CH2), 25.44 (CH2), 22.35 (CH2), 20.85
(CH2), 13.93 (CH3), 11.35 (CH3). HRMS-ESI (m/z): [M+Na]+
calcd for C19H24N2NaO, 319.1781; found, 319.1775.
Typical procedure for the catalytic Pauson–Khand reaction using
[Rh(CO)2Cl]2 to produce 17 and 18 (Table 3, Entry 3), and 19a
and 20
1-Benzyl-3-pentyl-1H-pyrrolo[2,3-b]quinolin-2(3H)-one (15b).
Yellow oil. IR (neat/cm-1): 2931, 1720, 1643, 1442, 1219, 756.
1H-NMR (500 MHz, CDCl3, d): 7.94 (d, J = 8.4 Hz, 1H), 7.80
(d, J = 8.4 Hz, 1H), 7.71 (dd, J = 1.2, 7.9 Hz, 1H), 7.62 (ddd,
J = 1.5, 7.0, 8.3 Hz, 1H), 7.54 (d, J = 7.3 Hz, 2H), 7.39 (ddd,
J = 1.2, 7.0, 7.9 Hz, 2H), 7.28 (dd, J = 7.3, 7.3 Hz, 1H),
7.22 (dd, J = 7.3, 7.3 Hz, 1H), 5.15–5.07 (m, 2H), 3.56 (t, J =
6.0 Hz, 1H), 2.10–1.90 (m, 2H), 1.42–1.21 (m, 6H), 0.82 (t, J =
7.1 Hz, 3H). 13C-NMR (125 MHz, CDCl3, d): 177.25 (C), 156.44
(C), 146.83 (C), 136.75 (C), 130.45 (CH), 129.23 (CH), 128.71
(CH¥2), 128.41 (CH¥2), 127.91 (CH), 127.74 (CH), 127.50 (CH),
126.12 (C), 124.52 (C), 124.44 (CH), 44.22 (CH), 42.73 (CH2),
31.62 (CH2), 30.62 (CH2), 25.43 (CH2), 22.32 (CH2), 13.91 (CH3).
HRMS-ESI (m/z): [M+Na]+ calcd for C23H24N2NaO, 364.1781;
found, 367.1791.
A solution of [Rh(CO)2Cl]2 (14.0 mg, 0.036 mmol) in p-xylene
(5 mL) was degassed, charged with carbon monoxide, and was
heated to 130 ◦C. A solution of carbodiimide 5c (138.4 mg, 0.516
mmol) in p-xylene (1 mL) was added, and the mixture was heated
at the same temperature for 2.0 h. The mixture was evaporated, and
the residue was purified by silica gel column chromatography (ethyl
acetate–hexane = 1 : 10) to give pyrroloquinoline 17c (13.1 mg,
0.041 mmol, 8% as a yellow oil) and 18a (94.9 mg, 0.299 mmol,
58%).
3,4-Dimethyl-1-propyl-1H-pyrrolo[◦2,3-b]quinolin-2(3H)-one
(17a). Brown solid; mp 185.2–186.7 C. IR (KBr/cm-1): 3062,
1
2969, 1720, 1635, 1589, 1435, 1227, 748. H-NMR (500 MHz,
CDCl3, d): 7.91 (d, J = 8.3 Hz, 1H), 7.85 (d, J = 8.4 Hz, 1H), 7.63
(d, J = 8.1 Hz, 2H), 7.59 (dd, J = 7.6, 7.6 Hz, 1H), 7.53 (dd, J =
7.7, 7.7 Hz, 2H), 7.46–7.38 (m, 2H), 3.76 (dt, J = 7.4, 7.4 Hz, 1H),
2.66 (s, 3H), 1.68 (d, J = 7.4 Hz, 3H).
1-Cyclohexyl-3-pentyl-1H-pyrrolo[2,3-b]quinolin-2(3H)-one
◦
(15c). Brownish solid; mp 67.8–69.0 C. IR (KBr/cm-1): 2931,
1720, 1635, 1581, 1435, 1219, 895, 748. 1H-NMR (500 MHz,
CDCl3, d): 7.92 (d, J = 8.3 Hz, 1H), 7.78 (s, 1H), 7.71 (d, J =
7.5 Hz, 1H), 7.61 (ddd, J = 1.3, 7.2, 8.3 Hz, 1H), 7.38 (ddd, J =
0.8, 7.4, 7.4 Hz, 1H), 4.48 (tt, J = 3.8, 12.2 Hz, 1H), 3.48 (t, J =
5.6 Hz, 1H), 2.61–2.49 (m, 2H), 2.06–1.84 (m, 4H), 1.76–1.69 (m,
2H), 1.51–1.22 (m, 10H), 0.85 (t, J = 6.6 Hz, 3H). 13C-NMR
(125 MHz, CDCl3, d): 177.35 (C), 157.04 (C), 146.69 (C), 129.99
13C-NMR (125 MHz, CDCl3, d): 177.40 (C), 155.77 (C), 146.36
(C), 139.42 (C), 133.30 (C), 129.03 (CH), 128.93 (CH¥2), 128.71
(CH), 127.86 (CH), 126.76 (CH¥2), 126.48 (C), 124.53 (CH),
123.29 (CH), 122.98 (C), 39.14 (CH), 16.11 (CH3), 14.67 (CH3).
HRMS-ESI (m/z): [M+Na]+ calcd for C19H16N2NaO, 311.1155;
found, 311.1145.
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3,4-Dimethyl-1-phenyl-1H -pyrrolo[◦2,3-b]quinolin-2(3H )-one
(17b). Brown solid; mp 185.2–186.7 C. IR (KBr/cm-1): 3062,
2969, 1720, 1635, 1589, 1435, 1227, 748. H-NMR (500 MHz,
(C), 131.92 (C), 128.67 (CH), 128.67 (CH¥2), 127.68 (CH), 127.66
(CH), 127.07 (CH), 127.03 (CH¥2), 126.40 (CH), 34.76 (C), 33.28
(CH), 29.31 (CH3¥3), 28.35 (CH3). HRMS-ESI (m/z): [M+Na]+
calcd for C22H22N2NaO, 353.1624; found, 353.1624.
1
CDCl3, d): 7.91 (d, J = 8.3 Hz, 1H), 7.85 (d, J = 8.4 Hz, 1H), 7.63
(d, J = 8.1 Hz, 2H), 7.59 (dd, J = 7.6, 7.6 Hz, 1H), 7.53 (dd, J = 7.7,
7.7 Hz, 2H), 7.46–7.38 (m, 2H), 3.76 (dt, J = 7.4, 7.4 Hz, 1H), 2.66
(s, 3H), 1.68 (d, J = 7.4 Hz, 3H). 13C-NMR (125 MHz, CDCl3, d):
177.40 (C), 155.77 (C), 146.36 (C), 139.42 (C), 133.30 (C), 129.03
(CH), 128.93 (CH¥2), 128.71 (CH), 127.86 (CH), 126.76 (CH¥2),
126.48 (C), 124.53 (CH), 123.29 (CH), 122.98 (C), 39.14 (CH),
16.11 (CH3), 14.67 (CH3). HRMS-ESI (m/z): [M+Na]+ calcd for
C19H16N2NaO, 311.1155; found, 311.1145.
4-Methoxy-3,4-dimethyl-1-propyl-1H-pyrrolo[2,3-b]quinolin-
2(4H)-one (19a). Yellow oil. IR (neat/cm-1): 2970, 2931, 1720,
1635, 1442, 1103, 756. 1H-NMR (600 MHz, CDCl3, d): 7.54 (dd,
J = 1.5, 7.6 Hz, 1H), 7.44 (dd, J = 1.1, 7.7 Hz, 1H), 7.33 (ddd,
J = 1.4, 7.7, 7.7 Hz, 1H), 7.25 (ddd, J = 1.3, 7.5, 7.5 Hz, 1H),
3.76–3.67 (m, 2H), 2.94 (s, 3H), 2.22 (s, 3H), 1.76 (tq, J = 7.3,
7.5 Hz, 2H), 1.64 (s, 3H), 0.96 (t, J = 7.5 Hz, 3H). 13C-NMR
(150 MHz, CDCl3, d): 170.74 (C), 156.46 (C), 143.75 (C), 135.83
(C), 133.31 (C), 131.33 (C), 129.04 (CH), 128.51 (CH), 126.75
(CH), 125.97 (CH), 74.40 (C), 52.47 (CH3), 40.36 (CH2), 31.01
(CH3), 21.98 (CH2), 11.32 (CH3), 9.12 (CH3). HRMS-ESI (m/z):
[M+Na]+ calcd for C17H20N2NaO2, 307.1417; found, 307.1415.
3-tert-Butyl-4-methyl-1-propyl-1H-pyrrolo[2,3-b]quinolin-2(3H)-
one (17c). Yellow oil. IR (KBr/cm-1): 3070, 2962, 1720, 1628,
1
1466, 1358, 1288, 1219, 1103, 756. H-NMR (600 MHz, CDCl3,
d): 7.89 (d, J = 8.8 Hz, 2H), 7.62 (ddd, J = 1.4, 7.0, 8.3 Hz, 1H),
7.42 (ddd, J = 1.2, 6.9, 8.3 Hz, 1H), 3.90–3.84 (m, 1H), 3.81–3.74
(m, 1H), 3.33 (s, 1H), 2.60 (s, 3H), 1.88–1.74 (m, 2H), 1.08 (s,
9H), 1.01 (t, J = 7.6 Hz, 3H).13C-NMR (150 MHz, CDCl3, d):
177.04 (C), 157.19 (C), 146.39 (C), 139.58 (C), 128.98 (CH),
128.00 (CH), 126.29 (C), 124.03 (CH), 123.82 (CH), 122.10 (C),
53.87 (CH), 40.58 (CH2), 37.84 (C), 28.07 (CH3¥3), 21.00 (CH2),
17.91 (CH3), 11.61 (CH3). HRMS-ESI (m/z): [M+Na]+ calcd for
C19H24N2NaO, 319.1781; found, 319.1775.
2-tert-Butyl-3-methoxy-3-methyl-1-propyl-1,3-dihydro-1,8-
diaza-cyclobuta[b]naphthalene (20). Yellow oil. IR (neat/cm-1):
2962, 1643, 1219, 1111, 756. 1H-NMR (300 MHz, CDCl3, d): 7.70
(dd, J = 1.3, 8.0 Hz, 1H), 7.64 (dd, J = 1.2, 8.1 Hz, 1H), 7.45 (ddd,
J = 1.5, 7.0, 8.2 Hz, 1H), 7.20 (ddd, J = 1.4, 7.0, 8.1 Hz, 1H),
3.45–3.25 (m, 2H), 3.21 (s, 3H), 2.40 (s, 3H), 1.95–1.78 (m, 2H),
1.13 (s, 9H), 1.01 (t, J = 7.4 Hz, 3H). 13C-NMR (150 MHz, CDCl3,
d): 163.90 (C), 149.88 (C), 132.53 (C), 129.20 (C), 128.44 (CH),
126.28 (CH), 126.11 (C), 123.95 (CH), 121.63 (CH), 110.41 (C),
52.43 (CH3), 45.12 (CH2), 38.10 (C), 26.27 (CH3¥3), 22.62 (CH2),
14.84 (CH3), 11.84 (CH3). HRMS-ESI (m/z): [M+H]+ calcd for
C19H27N2O, 299.2118; found, 299.2104.
3-tert-Butyl-4-methyl-1-propyl-1H-pyrrolo[2,3-b]quinolin-2(4H)-
one (18a). Yellow oil. IR (neat/cm-1): 3062, 2962, 1712, 1635,
1450, 1365, 1088, 941, 764. 1H-NMR (600 MHz, CDCl3, d): 7.42
(dd, J = 1.1, 7.8 Hz, 1H), 7.26 (ddd, J = 1.6, 7.5, 7.6 Hz, 1H),
7.18 (dd, J = 1.5, 7.6 Hz, 1H), 7.13 (ddd, 1.2, 7.4, 7.4 Hz, 1H),
4.31 (q, J = 7.3 Hz, 1H), 3.75–3.65 (m, 2H), 1.73 (dtq, J = 1.2,
7.4, 7.4 Hz, 2H), 1.45 (s, 9H), 1.39 (d, J = 7.4 Hz, 3H), 0.94 (t,
J = 7.5 Hz, 3H). 13C-NMR (150 MHz, CDCl3, d): 170.32 (C),
155.57 (C), 141.87 (C), 141.64 (C), 134.08 (C), 132.00 (C), 128.16
(CH), 127.87 (CH), 127.62 (CH), 125.91 (CH), 40.10 (CH2), 34.51
(C), 33.11 (CH), 29.27 (CH3¥3), 28.16 (CH3), 21.91 (CH2), 11.36
(CH3). HRMS-ESI (m/z): [M+Na]+ calcd for C19H24N2NaO,
319.1781; found, 319.1782.
Notes and references
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Kim and Y.-T. Hong, Angew. Chem., Int. Ed., 2002, 41, 1584; (e) N.
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4 (a) T. Saito, M. Nakane, M. Endo, H. Yamashita, Y. Oyamada and S.
Motoki, Chem. Lett., 1986, 1350; (b) T. Saito, M. Nakane, T. Miyazaki
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H. Ohmori, E. Furuno and S. Motoki, J. Chem. Soc., Chem. Commun.,
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Motoki, Chem. Lett., 1993, 1127; (e) T. Saito, H. Ohmori, T. Ohkubo
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K. Tsuda and Y. Saito, Tetrahedron Lett., 1996, 37, 209; (g) T. Saito and
K. Tsuda, Tetrahedron Lett., 1996, 37, 9071; (h) T. Saito, T. Ohkubo,
H. Kuboki, M. Maeda, K. Tsuda, T. Karakasa and S. Satsumabayashi,
J. Chem. Soc., Perkin Trans. 1, 1998, 3065; (i) S. Hirota, R. Kato, M.
Suzuki, Y. Soneta, T. Otani and T. Saito, Eur. J. Org. Chem., 2008, 2075.
3-tert-Butyl-4-methyl-1-phenyl-1H-pyrrolo[2,3-b]quinolin-2(3H)-
◦
one (17d). Yellow solid; mp 157.8–158.8 C. IR (KBr/cm-1):
1
3054, 2954, 1727, 1427, 1288, 1227, 1173, 918, 764. H-NMR
(600 MHz, CDCl3, d): 7.91 (dd, J = 1.0, 8.2 Hz, 1H), 7.83 (d, J =
8.3 Hz, 1H), 7.61–7.56 (m, 3H), 7.55–7.51 (m, 2H), 7.45–7.39
(m, 2H), 3.52 (s, 1H), 2.66 (s, 3H), 1.16 (s, 9H). 13C-NMR
(150 MHz, CDCl3, d): 176.17 (C), 156.84 (C), 146.03 (C), 140.40
(C), 133.27 (C), 129.05 (CH), 128.98 (CH¥2), 128.46 (CH), 127.88
(CH), 126.90 (CH¥2), 126.47 (C), 124.42 (CH), 123.66 (CH),
121.47 (C), 53.02 (CH), 38.57 (C), 27.95 (CH3¥3), 17.96 (CH3).
HRMS-ESI (m/z): [M+Na]+ calcd for C22H22N2NaO, 353.1624;
found, 353.1634.
3-tert-Butyl-4-methyl-1-phenyl-1H-pyrrolo[2,3-b]quinolin-2(4H)-
one (18b). Yellow oil. IR (neat/cm-1): 3062, 2954, 1720, 1627,
1589, 1496, 1427, 1227, 918, 764. 1H-NMR (500 MHz, CDCl3, d):
7.54 (d, J = 8.0 Hz, 2H), 7.48 (dd, J = 7.9, 7.9 Hz, 2H), 7.40 (d,
J = 7.7 Hz, 1H), 7.35 (dd, J = 7.4, 7.4 Hz, 1H), 7.27–7.19 (m,
2H), 7.16 (dd, J = 7.4, 7.4 Hz, 1H), 4.43 (q, J = 7.2 Hz, 1H), 1.51
(s, 9H), 1.47 (d, J = 7.2 Hz, 3H). 13C-NMR (125 MHz, CDCl3, d):
169.23 (C), 155.01 (C), 141.47 (C), 141.37 (C), 134.96 (C), 133.07
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1132 | Org. Biomol. Chem., 2010, 8, 1126–1132
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