Synthesis of Cyclopenta[b]indol-1-ones and Carbazol-4-ones from N-(2-Halophenyl)-Substituted Enaminones by Intramolecular Heck Reaction

Article abstract of DOI:10.1002/hlca.200490020

An efficient synthetic route towards N-methylated or nonmethylated 3,4-dihydrocyclopent[b]indol-1(2H)-ones (3) and 1,2,3,9-tetrahydrocarbazol-4(4H)-one (10) was elaborated, based on Pd-catalyzed intramolecular Heck reaction. The chemoselectivity of the cyclization was studied in the case of the bi- and trifunctional substrates 12 and 17, respectively. In the latter case, depending on the catalyst, either the brominated indole 18 or the tetracyclic compound 19 were obtained by single and double Heck reaction, respectively.

Full text of DOI:10.1002/hlca.200490020

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Helvetica Chimica Acta Vol. 87 (2004)
Synthesis of Cyclopenta[b]indol-1-ones and Carbazol-4-ones from
N-(2-Halophenyl)-Substituted Enaminones by Intramolecular Heck Reaction
by Ulrik S. S˘rensen and Esteban Pombo-Villar*
Nervous System Research, WSJ386.7.15, Novartis Pharma AG, Lichtstrasse 35, CH-4002 Basel
(e-mail: esteban.pombo@pharma.novartis.com)
An efficient synthetic route towards N-methylated or nonmethylated 3,4-dihydrocyclopent[b]indol-1(2H)-
ones (3) and 1,2,3,9-tetrahydrocarbazol-4(4H)-one (10) was elaborated, based on Pd-catalyzed intramolecular
Heck reaction. The chemoselectivity of the cyclization was studied in the case of the bi- and trifunctional
substrates 12 and 17, respectively. In the latter case, depending on the catalyst, either the brominated indole 18 or
the tetracyclic compound 19 were obtained by single and double Heck reaction, respectively.
Introduction. A group of serotonin (5-HT3) receptor antagonists are structurally
based on the tricyclic carbazolone ring system. Examples of this class of neuroactive
compounds are ondansetron (1) and alosetron (2) [1], developed as an antiemetic and a
treatment of the so-called irritable bowel syndrome (IBS), respectively.
Ondansetron (1) contains a hex-2-enone ring, but the key intermediate in a
synthesis of 2 is the cyclopenta[b]indol-1(2H)-one (3a), which, by Beckmann
rearrangement, can be converted into the −lactam× 4, which, in several steps, can be
further modified to give 2 (Scheme 1) [1c].
We were particularly interested in the preparation of 3,4-dihydro-4-methyl-
cyclopental[b]indol-1(2H)-one (3a). Previously described syntheses of 3a gave only
low yields, and were mostly based on photochemical activation [1c][2] or the Fischer
indole synthesis [1c]. Thus, cyclization of 5 under UV light for 4 d gave 3a in 40% yield
(Scheme 1) [2]. Base-promoted intramolecular alkylation of indole 6a has also been
reported to give 3a, but only in 4% isolated yield, in contrast to the sterically hindered
6b, which gave much higher yields of 3a (Scheme 1) [3]. Furthermore, carbazolones
and carbolines (azacarbazoles) have been prepared from N-(2-haloaryl)-substituted
enaminones by palladium catalyzed cyclization [4] and by a coupling entirely promoted
by equivalent or excess amounts of CuI [5].

Helvetica Chimica Acta Vol. 87 (2004)
83
Scheme 1
Due to the limited success reported for the preparation of 3a, we were looking for a
more-efficient synthesis.
Results and Discussion. Our strategy was to use an intramolecular Heck reaction,
starting with substrates of type 7, in which a bond is formed between the ortho-
halogenated C-atom and the enone ring (Scheme 2).
Scheme 2
From N-methyl-2-iodoaniline (8a) [6] and commercially available cyclopentane-
1,3-edione, the condensation product 7a was synthesized by heating overnight without
any solvent. The key synthetic step was the Pd-catalyzed cyclization of 7a to 3a in the
presence of Pd(OAc)2 (5 mol%) and tri(o-tolyl)phosphine ((2-MeC6H4)3P) in DMF
under microwave heating [7] (1008, 5 min) to afford, after column chromatography and
recrystallization, 99% of 3a (Table, Entry 1). Thus, a short and efficient synthesis of this
key building block of alosetron (2) was obtained. However, further improvements

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Helvetica Chimica Acta Vol. 87 (2004)
could be made if it was possible to replace the 2-iodoaniline 8a with the much cheaper
bromoaniline 8b as the precursor of 7b (Scheme 2). Unfortunately, the latter turned
out to be less reactive in the above cyclization reaction (30% conversion to 3a after
30 min; Table, Entry 5). However, upon conventional heating at 1208 overnight, 3a was
isolated in 95% yield (Entry 7). In the case of the nonmethylated substrate 7c, the
reactivity was lower, leading to only 3% conversion after 30 min at 1008 (Entry 2).
However, upon increasing the amount of Pd catalyst as well as both the reaction time
and temperature, 3b could be isolated in 80% yield (Entry 3). For the corresponding
bromo-substituted substrate 7d, these conditions and a prolonged reaction time of 16 h
were not sufficient to drive the reaction to completion (37% conversion; Entry 8).
However, replacing (2-MeC6H4)3P with (t-Bu)3P improved the yield to 85%, with only
small amounts of remaining unreacted starting material (Entry 9). And in the presence
of 1,3-bis(diphenylphosphino)propane (dppp), complete conversion and 92% isolated
yield of 3b were achieved (Entry 10).
Table. Experimental Details for the Synthesis of 3a,b by Pd-catalyzeda) Heck Reaction of 7a
d
Entry Substrate R'
R
Reaction time Temp. [8] Heating
P-Ligand
Product Yield [%]
99
3b)
1
2
7a
7c
7c
7c
7b
7b
7b
7d
7d
7d
I
I
I
I
Me 30 min
100
100
120
100
100
100
120
120
120
120
Microwave (2-MeC6H4)3P 3a
Microwave (2-MeC6H4)3P 3b
Oil bath
Microwave dppp
Microwave (2-MeC6H4)3P 3a
Microwave dppp 3a
Oil bath
Oil bath
Oil bath
Oil bath
H
H
H
30 min
16 h
30 min
3
4
(2-MeC6H4)3P 3b
80
3b
25b)
30b)
35b)
95
5
6
7
Br Me 30 min
Br Me 30 min
Br Me 16 h
(2-MeC6H4)3P 3a
(2-MeC6H4)3P 3b
(t-Bu)3P
8
9
10
Br
Br
Br
H
H
H
16 h
16 h
16 h
37c)
85
3b
3b
dppp
92
a) For microwave and oil-bath experiments, 5 and 10 mol-% of catalyst were used, resp. b) Conversion into
product (%) determined by 1H-NMR of crude product. c) Separated from starting material by recrystallization
(AcOEt).
After these successful results, we carried out experiments to extend the above
procedure to the synthesis of carbazoles (Scheme 3). The cyclohex-2-enone 9, formed
by condensation of 2-iodoaniline and cyclohexane-1,3-dione, underwent cyclization
cleanly to afford the carbazolone 10 in 95% yield. In contrast, compound 11 did,
surprisingly, not give the desired product. Different methods were tested, but only
starting material or side products could be isolated.
We were further interested in determining the selectivity of the Heck coupling with
respect to different unsaturated systems. Thus compound 12, containing the enone

Helvetica Chimica Acta Vol. 87 (2004)
85
Scheme 3
function as well as an N-allyl group, was synthesized from 13 and subjected to
intramolecular Heck coupling (Scheme 4). Interestingly, 12 exclusively underwent
intramolecular endo-cyclization with the allyl function to give indole 14 in excellent
yield. Eventually, the higher electron density of the allyl group compared to the more-
delocalized enone moiety could explain this interesting and highly chemoselective
transformation.
Scheme 4
Extending the above observations to a 2,6-dibromo substituted analog, it should, in
principle, be possible to achieve a multiple cyclization to the corresponding indole and
the indol-1-one. Starting from 2,6-dibromoaniline, we first prepared 15, which,
however, gave only a black residue upon reaction with cyclopentane-1,3-dione
(Scheme 5). However, when performing first the condensation with 2,6-dibromoaniline
to give 16, followed by N-alkylation with allylbromide, the desired substrate 17 could be
prepared in 50% overall yield. Pd-catalyzed cyclization gave, after 16 h at 1208,
compound 18 as the only major product, i.e., only cyclization to the 3-methylindole had
taken place, the second Br-atom being left unreacted in the presence of (2-MeC6H4)3P.
However, when dppp was used as phosphine ligand, a more-complex reaction was
observed, and, apart from small amounts of 18, the only product isolated was the
tetracyclic compound 19, the latter lacked the expected 3-methylindole moiety of 18,
and the presence of an exocyclic methylidene group was apparent. The structural

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Helvetica Chimica Acta Vol. 87 (2004)
Scheme 5
1
assignment of 19 was supported by NOE, DEPT, H-COSY, and C/H-correlation
spectroscopy. We speculate that, in this case, the 3-methylindolyl moiety was initially
formed and that the second cyclization then gave rise to a migration of the double bond
to 19.
The authors thank Mr. Regis Denay for the structural characterisation of 19.
Experimental Part
General. Reagents and solvents were purchased from commercial sources and used without further
purification, unless stated otherwise. Melting points (m.p.) were determined in open capillaries, uncorrected.
Microwave irradiation was performed with a MLS-Ethos-1600 instrument (Milestone). Column chromatog-
raphy (CC) was performed on silica gel 60 (0.040 0.063 mm; Merck) or with prepacked Flashpack silica-gel
columns (50 or 70 g; Jones Chromatography Ltd., UK). Compounds were visualized by thin-layer
chromatography (TLC; silica-gel 60F
plates; Merck) using UV light and KMnO4 spraying reagent. 1H-
254
and 13C-NMR spectra1): Bruker, at 400 or 100 MHz, resp. HR-MS: performed by the Analytics Department at
Novartis Pharma AG (Basel) on an Agilent Series 1100 LC/MSD instrument; in m/z. Elemental analyses were
performed by Solvias AG, Basel.
General Procedure 1 (GP1) for the N-Alkylation of Anilines. See the synthesis of 13 (below).
2-Bromo-N-(prop-2-enyl)aniline (13). GP1: 2-Bromoaniline (7.00 g, 40.7 mmol), dissolved in anh. THF
(100 ml), was cooled to À788 under Ar. To the stirred mixture was slowly added a 1.6m soln. of MeLi in Et2O
(28.0 ml, 44.8 mmol), followed, after stirring for 30 min, by dropwise addition of allyl bromide (5.42 g,
44.8 mmol). The mixture was stirrred for 10 min at À788, then 2 h at r.t. Then, aq. NaHCO3 soln. was added, and
the mixture was extracted with AcOEt (3Â). The combined org. layer was dried (MgSO4), filtered, and
1) Note that the various (phenylamino)cyclopent-2-enone and (phenylamino)cyclohex-2-enone moieties
gave rise to tautomerism (typically 1:9), and that the chemical shifts d (in ppm rel. to SiMe4) and the
coupling constants J (in Hz) are stated for the most-abundant forms only.
1
)

Helvetica Chimica Acta Vol. 87 (2004)
87
concentrated in vacuo. The residue was purified by CC (0 5% AcOEt in hexane) to give 13 (7.13 g, 83%). Oil.
1H-NMR (CDCl3): 3.76 3.82 (m, 2 H); 4.45 (br. s, 1 H); 5.15 5.18 (m, 1 H); 5.23 5.29 (m, 1 H); 5.86 5.98 (m,
1 H); 6.50 6.61 (m, 2 H); 7.10 7.16 (m, 1 H); 7.37 7.42 (m, 1 H). 13C-NMR (CDCl3) [8]: 46.1; 109.7; 111.5;
‡
116.3; 117.8; 128.4; 132.3; 134.6; 144.7. ESI-MS: 314 (100, [M ‡ 1] ).
N-Methyl-2-bromoaniline (8b). GP1: 5.43 g (84%). Oil. 1H-NMR (CDCl3): 5.40 (s, 3 H); 6.85 (br. s, 1 H);
9.06 9.18 (m, 2 H); 9.70 9.76 (m, 1 H); 9.92 10.0 (m, 1 H). 13C-NMR (CDCl3): 33.5; 112.5; 113.6; 120.5;
‡
131.5; 135.2; 148.9. ESI-MS: 187 (20, [M ‡ 1] ).
2,6-Dibromo-N-(prop-2-enyl)aniline (15). GP1: 6.41 g (92%). Oil. 1H-NMR (CDCl3): 3.86 3.91 (m, 2 H);
3.98 (br. s, 1 H); 5.11 5.15 (m, 1 H); 5.23 5.30 (m, 1 H); 5.92 6.02 (m, 1 H); 6.67 (t, J ˆ 8.0, 1 H); 7.45 (d, J ˆ
‡
8.0, 2 H). 13C-NMR (CDCl3): 50.8; 116.7; 117.3; 123.8; 132.7; 135.6; 144.7. ESI-MS: 292 (100, [M ‡ 1] ).
3-[(2,6-Dibromophenyl)(prop-2-enyl)amino]cyclopent-2-en-1-one (17). Compound 16 (1.00 g,
3.02 mmol), dissolved in anh. DMF (10 ml), was cooled on ice under Ar. To the stirred soln. was added NaH
(181 mg, 4.53 mmol; 60% dispersion in mineral oil), followed, after stirring for 45 min, by dropwise addition of
allyl bromide (365 mg, 3.02 mmol). The mixture was allowed to warm to r.t. and was stirrred for 4 h. Then, aq.
NaHCO3 soln. was added, and the mixture was extracted with AcOEt (3Â). The combined org. layer was dried
(MgSO4), filtered, and concentrated in vacuo. The residue was purified by CC (SiO2; AcOEt) to give 17 (1.05 g,
1
94%). Oil. H-NMR (CDCl3): 2.18 2.22 (m, 2 H); 2.34 2.38 (m, 2 H); 4.15 (d, J ˆ 6.9, 2 H); 5.14 5.30 (m,
2 H); 5.36 (s, 1 H); 5.93 6.05 (m, 1 H); 7.16 (t, J ˆ 8.1, 1 H); 7.65 (d, J ˆ 8.1, 2 H). 13C-NMR (CDCl3): 28.1; 34.0;
‡
56.1; 102.8; 120.3; 125.8; 130.9; 131.0; 132.8; 140.6; 176.0; 204.8. ESI-MS: 372 (100, [M ‡ 1] ). HR-MS: 369.9444
‡
(C14H14Br2NO ; calc. 369.9442).
General Procedure 2 (GP2) for the Condensation of Anilines and Cyclic 1,3-Diones. See the synthesis of 9
(below).
3-[(2-Iodophenyl)amino]cyclohex-2-en-1-one (9). GP2: 2-Iodoaniline (8.50 g, 38.8 mmol) and cyclohexa-
1,3-dione (4.35 g, 38.8 mmol) were stirred overnight at 1208. The mixture was cooled to r.t., dissolved in a small
amount of CH2Cl2, and purified by CC (CH2Cl2/AcOEt/Et3N 10 :88 :2) to give 9 (7.67 g, 63%). Solid. M.p.
156.5 157.58 (lit. 155 1568 [4b]). 1H-NMR (CDCl3): 2.02 2.10 (m, 2 H); 2.37 (t, J ˆ 6.6, 2 H); 2.54 (t, J ˆ 6.1,
2 H); 5.34 (s, 1 H); 6.18 (br. s, 1 H); 6.89 6.95 (m, 1 H); 7.31 7.35 (m, 2 H); 7.82 7.86 (m, 1 H). 13C-NMR
‡
(CDCl3): 21.8; 29.6; 36.5; 95.9; 100.7; 126.2; 127.7; 129.2; 139.3; 139.6; 161.5; 198.3. ESI-MS: 314 (100, [M ‡ 1] ).
3-[(2-Iodophenyl)(methyl)amino]cyclopent-2-en-1-one (7a). GP2: 6.83 g (63%). Yellowish gum. 1H-NMR
(CDCl3): 2.13 2.21 (m, 2 H); 2.32 2.40 (m, 2 H); 3.22 (s, 3 H); 5.21 (s, 1 H); 7.02 7.46 (m, 3 H); 7.88 7.92 (m,
‡
1 H). ESI-MS: 314 (100, [M ‡ 1] ).
3-[(2-Bromophenyl)(methyl)amino]cyclopent-2-en-1-one (7b). GP2: 2.17 g (76%). Oil. 1H-NMR (CDCl3):
2.18 2.45 (m, 4 H); 3.25 (s, 3 H); 5.22 (s, 1 H); 7.22 7.45 (m, 3 H); 7.65 7.72 (m, 1 H). 13C-NMR (CDCl3): 28.1;
‡
34.4; 40.7; 101.7; 123.1; 128.9; 129.6; 130.1; 133.9; 143.0; 177.0; 204.5. ESI-MS: 266 (100, M ).
3-[(2-Iodophenyl)amino]cyclopent-2-en-1-one (7c). GP2: 3.80 g (46%). Solid. M.p. 178.5 179.58.
1H-NMR (CDCl3): 2.45 2.51 (m, 2 H); 2.80 2.85 (m, 2 H); 5.42 (s, 1 H); 6.85 6.99 (m, 2 H); 7.32 7.39 (m,
2 H); 7.82 7.86 (m, 1 H). 13C-NMR (CDCl3): 28.91; 33.59; 93.12; 103.42; 123.14; 127.00; 129.39; 139.57; 140.29;
‡
172.37; 205.75. ESI-MS: 299 (100, M ). Anal. calc. for C11H10INO ¥ 0.05 Et3N: C 44.62, H 3.56, N 4.84; found:
C 44.22, H 3.33, N 5.19.
3-[(2-Bromophenyl)amino]cyclopent-2-en-1-one (7d). GP2: 4.86 g (70%). Solid. M.p. 166.5 168.08.
1H-NMR (CDCl3): 2.45 2.52 (m, 2 H); 2.79 2.84 (m, 2 H); 5.60 (s, 1 H); 6.81 (br. s, 1 H); 7.00 7.05 (m, 1 H);
7.32 7.42 (m, 2 H); 7.57 7.62 (m, 1 H). 13C-NMR (CDCl3): 29.2; 33.4; 104.0; 115.7; 122.2; 125.9; 128.5; 133.2;
‡
137.5; 171.2; 205.9. ESI-MS: 252 (100, M ). Anal. calc. for C11H10BrNO ¥ 0.05 Et3N: C 52.78, H 4.21, N 5.72;
found: C 52.47, H 4.03, N 6.09.
3-[(2,6-Dibromophenyl)amino]cyclohex-2-en-1-one (11). GP2: 1.65 g (40%). Solid. M.p. 255 2578.
1H-NMR (CDCl3): 2.03 2.12 (m, 2 H); 2.36 (t, J ˆ 6.5, 2 H); 2.52 (t, J ˆ 6.2, 2 H); 4.82 (s, 1 H); 5.92 (br. s,
1 H); 7.06 (t, J ˆ 8.1, 1 H); 7.60 (d, J ˆ 8.1, 2 H). 13C-NMR (CDCl3): 21.8; 28.7; 36.4; 101.6; 124.5; 130.0; 132.7;
‡
135.5; 161.6; 198.2. ESI-MS: 346 (100, [M ‡ 1] ). Anal. calc. for C12H11Br2NO: C 41.77, H 3.21, N 4.06; found:
C 41.65, H 3.24, N 3.99.
3-[(2-Bromophenyl)(prop-2-enyl)amino]cyclopent-2-en-1-one (12). GP2: 2.98 g (72%). Oil. 1H-NMR
(CDCl3): 2.17 2.23 (m, 2 H); 2.30 2.35 (m, 2 H); 3.97 (dd, J ˆ 6.5, 15.6, 2 H); 4.28 (dd, J ˆ 5.7, 15.6, 2 H);
5.15 5.33 (m, 3 H); 5.82 5.95 (m, 1 H); 7.20 7.42 (m, 3 H); 7.65 7.71 (m, 1 H). 13C-NMR (CDCl3): 28.5; 34.1;
‡
56.5; 102.1; 119.3; 123.5; 128.6; 130.1; 130.7; 130.8; 133.8; 141.7; 176.4; 204.6. ESI-MS: 292 (100, M ).
3-[(2,6-Dibromophenyl)amino]cyclopent-2-en-1-one (16). GP2: 2.77 g (53%). Solid. An anal. sample was
recrystallized from AOEt/MeOH. M.p. 210.1 211.08. 1H-NMR ((D6)DMSO): 2.20 2.30 (m, 2 H); 2.65 2.75
(m, 2 H); 3.30 3.34 (m, 1 H); 4.28 (br. s, 1 H); 7.24 (t, J ˆ 8.1, 1 H); 7.79 (d, J ˆ 8.1, 2 H). 13C-NMR

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Helvetica Chimica Acta Vol. 87 (2004)
‡
((D6)DMSO): 27.4; 34.2; 100.9; 123.9; 131.0; 133.2; 137.4; 175.1; 203.0. ESI-MS: 332 (100, [M ‡ 1] ). Anal. calc.
for C11H9Br2NO: C 39.92, H 2.74, N 4.23; found: C 39.91, H 2.67, N 4.44.
General Procedure 3 (GP3) for the Preparation of Cyclopenta[b]indol-1-ones. See the synthesis of 3a
(below).
3,4-Dihydro-4-methylcyclopenta[b]indol-1(2H)-one (3a). GP3: A stirred soln. of 7a (6.00 g, 19.2 mmol),
AcONa (6.29 g, 76.6 mmol), Bu4NCl (5.33 g, 19.2 mmol), tri(o-tolyl)phosphine (583 mg, 1.92 mmol), and
Pd(OAc)2 (0.96 mmol, 215 mg) in anh. DMF (300 ml) under Ar was heated in a microwave oven at 1008 for
30 min. The mixture was cooled to r.t., added to aq. NaHCO3 soln., and extracted with AcOEt (3Â). The org.
layer was dried (MgSO4), filtered, and concentrated in vacuo, and the remaining solid was purified by CC
(CH2Cl2/AcOEt 1:1, then AcOEt/Et3N 98:2) and recrystallization (AcOEt/MeOH) to give 3a (3.52 g; 99%).
Solid. M.p. 214.3 216.08 (lit. 209 2108 [3]). 1H-NMR (CDCl3): 2.80 (s, 4 H); 3.58 (s, 3 H); 7.16 7.26 (m, 3 H);
7.84 7.90 (m, 1 H). 13C-NMR (CDCl3): 20.4; 30.4; 40.7; 110.0; 119.1; 120.7; 121.3; 122.2; 123.3; 143.0; 168.2;
‡
195.1. ESI-MS: 185 (100, M ). Anal. calc. for C12H11NO: C 77.81, H 5.99, N 7.56; found: C 77.61, H 5.91, N 7.62.
3,4-Dihydrocyclopenta[b]indol-1(2H)-one (3b). GP3: 228 mg (80%). Solid. M.p. 259.5 260.58 (lit. 257
2598 [9]). 1H-NMR ((D6)DMSO): 3.00 3.03 (m, 2 H); 3.25 3.29 (m, 2 H); 7.30 7.40 (m, 2 H); 7.60 7.65 (m,
1 H); 7.82 7.87 (m, 1 H). 13C-NMR ((D6)DMSO): 21.4; 41.0; 113.0; 119.6; 119.8; 121.3; 121.9; 123.3; 142.6;
‡
168.2; 195.1. ESI-MS: 172 (100, [M ‡ 1] ).
1,2,3,9-Tetrahydrocarbazol-4(4H)-one (10). GP3: 169 mg (95%). Solid. M.p. 223 2258 (dec.). 1H-NMR
((D6)DMSO): 2.06 2.16 (m, 2 H); 2.43 (t, J ˆ 6.3, 2 H); 2.96 (t, J ˆ 6.1, 2 H); 7.10 7.19 (m, 2 H); 7.36 7.42 (m,
1 H); 7.91 7.98 (m, 1 H); 11.8 (br. s, 1 H). 13C-NMR ((D6)DMSO): 23.1; 23.8; 38.2; 111.9; 112.1; 120.5; 121.9;
‡
122.8; 124.9; 136.1; 152.6; 193.2. ESI-MS: 186 (100, [M ‡ 1] ).
3-(3-Methyl-1H-indol-1-yl)]cyclopent-2-en-1-one (14). GP3: 310 mg (90%). Solid. M.p. 162.5 163.58.
1H-NMR (CDCl3): 2.32 (s, 3 H); 2.58 2.62 (m, 2 H); 3.21 3.25 (m, 2 H); 6.26 (s, 1 H); 7.13 (s, 1 H); 7.26 7.38
(m, 2 H); 7.54 7.58 (m, 1 H); 7.65 7.69 (m, 1 H). 13C-NMR (CDCl3): 9.6; 29.4; 33.5; 111.6; 113.5; 118.3; 119.8;
‡
122.2; 122.8; 124.6; 132.3; 136.2; 167.5; 206.9. ESI-MS: 212 (100, [M ‡ 1] ). Anal. calc. for C14H13NO: C 79.59,
H 6.20, N 6.63; found: C 79.45, H 6.37, N 6.60.
3-(7-Bromo-3-methyl-1H-indol-1-yl)cyclopent-2-en-1-one (18). GP3: 155 mg (66%). Solid. M.p. 125.3
1
127.38. H-NMR (CDCl3): 2.31 (s, 3 H); 2.64 2.69 (m, 2 H); 3.12 3.17 (m, 2 H); 5.97 (s, 1 H); 7.11 7.17 (m,
2 H); 7.48 7.54 (m, 2 H). 13C-NMR (CDCl3): 9.5; 30.0; 34.7; 106.3; 116.5; 118.7; 123.6; 123.7; 125.1; 129.7; 134.6;
‡
135.0; 166.5; 205.8. ESI-MS: 291 (100, [M ‡ 1] ). Anal. calc. for C14H12BrNO: C 57.95, H 4.17, N 4.83; found:
C 58.03, H 4.30, N 4.74.
4,5,7,8-Tetrahydro-4-methylidene-9H-cyclopenta[b]pyrrolo[3,2,1-hi]indol-9-one (19). According to GP3,
but with 1,3-bis(diphenylphosphino)propane (dppp) as phosphine ligand:125 mg (34%). Solid. M.p. 192 1938.
IR (KBr): 1663, 1650. Raman (powder): 3092, 3097, 2984, 2960, 2931, 1656, 1645, 1581, 1491, 1475, 1439, 1419,
1409, 1532, 1176, 676, 698, 366. 1H-NMR (CDCl3): 2.89 2.99 (m, 4 H); 4.95 (s, 2 H); 5.29 (s, 1 H); 5.67 (s, 1 H);
7.15 7.25 (m, 2 H); 7.60 7.62 (m, 1 H). 13C-NMR (CDCl3): 21.0; 40.8; 53.5; 106.7; 114.5; 115.5; 120.5; 123.4;
‡
‡
‡
123.6; 124.5; 144.7; 155.0; 164.1; 195.4. ESI-MS: 210 (100, [M ‡ 1] ). HR-MS: 210.0917 ([M ‡ H] , C14H12NO ;
calc. 210.0919). Anal. calc. for C14H11NO ¥ 0.5 H2O: C 77.05, H 5.54, N 6.42, O 11.00; found: C 77.25, H 5.23, N
6.50, O 11.02.
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Received August 13, 2003