Synthesis of 9,9-disubstituted 9H-pyrrolo[1,2-a]indoles by hydriodic acid-catalyzed cyclization of 1-[2-(1-aryl(or methyl)ethenyl)phenyl]-1H-pyrroles

Article abstract of DOI:10.1002/hlca.201100091

A novel method is reported for the synthesis of 9,9-disubstituted 9H-pyrrolo[1,2-a]indoles. Cyclization of 1-[2-(1-aryl(or methyl)ethenyl)phenyl]- 1H-pyrroles, which can be easily prepared from 2-(1-aryl(or methyl)ethenyl) anilines, proceeds smoothly, in

Full text of DOI:10.1002/hlca.201100091

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Synthesis of 9,9-Disubstituted 9H-Pyrrolo[1,2-a]indoles by Hydriodic Acid-
Catalyzed Cyclization of 1-[2-(1-Aryl(or methyl)ethenyl)phenyl]-1H-pyrroles
by Kazuhiro Kobayashi*, Kenichi Hashimoto, Hiroo Hashimoto, Hideaki Kondo, and Hisatoshi Konishi
Division of Applied Chemistry, Department of Chemistry and Biotechnology, Graduate School of
Engineering, Tottori University, 4-101 Koyama-minami, Tottori 680-8552, Japan
(phone/fax: þ 81-857-315263; e-mail: kkoba@chem.tottori-u.ac.jp)
A novel method is reported for the synthesis of 9,9-disubstituted 9H-pyrrolo[1,2-a]indoles.
Cyclization of 1-[2-(1-aryl(or methyl)ethenyl)phenyl]-1H-pyrroles, which can be easily prepared from
2-(1-aryl(or methyl)ethenyl)anilines, proceeds smoothly, in general, at 08 in the presence of a catalytic (or
an equimolar) amount of HI in MeCN to provide the desired products.
Introduction. – 9H-Pyrrolo[1,2-a]indoles have attracted much attention due to their
structural resemblance to cytostatic mytomycine derivatives [1]. Although a number of
methods for the preparation of 9H-pyrrolo[1,2-a]indoles have recently been published
[2], there have been only few reports on the synthesis of 9,9-disubstituted derivatives
[1a][3]. For example, Cartoon and Cheeseman have reported a synthesis 9,9-diphenyl-
9H-pyrrolo[1,2-a]indole by the reaction of 1-(2-lithiophenyl)-1H-pyrrole with benzo-
phenone, followed by acid-catalyzed cyclization of the resulting adducts [3]. Therefore,
we embarked upon development of a convenient method for their preparation. In this
article, we report that the hydriodic acid-catalyzed (or mediated) cyclization of 1-[2-(1-
aryl(or methyl)ethenyl)phenyl]-1H-pyrroles 2 offers an efficient method for the
preparation of 9,9-disubstituted 9H-pyrrolo[1,2-a]indoles 3.
Results and Discussion. – Our preparation of 9,9-disubstituted 9H-pyrrolo[1,2-a]-
indoles 3 is conducted as illustrated in Scheme 1. Thus, exposure of 1-[2-(1-
arylethenyl)phenyl]-1H-pyrroles 2a – 2i, which were readily available from the
corresponding 2-(1-arylethenyl)benzenamines 1a – 1i and 2,5-dimethoxytetrahydrofur-
an in AcOH under the reported conditions [4], to a catalytic or an equimolar amount of
concentrated HI in MeCN at 08 led to 9-aryl-9-methyl-9H-pyrrolo[1,2-a]indoles 3a – 3i
in generally good yields, as compiled in the Table. While most of the cyclization
reactions of 2 proceeded smoothly in the presence of 0.1 mol-equiv. of HI to give the
corresponding desired products 3 in good yields, those of 2 with a Cl substituent at
either of the benzene rings, i.e., 2d and 2h, required an equimolar amount of HI and
extended reaction times to afford the corresponding desired products 3d and 3h,
respectively, in somewhat lower yields (Entries 4 and 8). This is attributable to the
lower reactivity of the vinyl moiety of these precursors to protonation due to an
electron-deficient benzene ring.
The probable pathway to 3 from 2 is depicted in Scheme 2. Protonation of the vinyl
moiety of 2 generates a carbocation in a-position to the benzene ring (!4), which is
ꢀ 2011 Verlag Helvetica Chimica Acta AG, Zꢁrich

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Table. Preparation of 9H-Pyrrolo[1,2-a]indoles 3
Entry
1
2
Yielda) [%] HI [equiv.] Time
3
Yielda) [%]
1
2
3
4
5
6
7
8
9
1a R1 ¼ H, R2 ¼ Ph
2a 74
2b 70
2c 78
2d 81
2e 67
2f 73
0.1
0.1
0.1
1
0.1
0.1
0.1
1
1 h
1 h
1 h
3a 93
3b 82
3c 91
3d 78
3e 80
1b R1 ¼ H, R2 ¼ m-Tol
1c R1 ¼ H, R2 ¼ p-Tol
1d R1 ¼ H, R2 ¼ 4-ClꢀC6H4
1e R1 ¼ H, R2 ¼ 3-MeOꢀC6H4
1f R1 ¼ H, R2 ¼ 4-MeOꢀC6H4
12 h
1 h
10 min 3f 88
5 min 3g 92
12 h
3.5 h 3i 83
12 h
3j 34b)
1g R1 ¼ H, R2 ¼ 3,4-(MeO)2ꢀC6H3 2g 72
1h R1 ¼ Cl, R2 ¼ Ph
1i R1 ¼ MeO, R2 ¼ Ph
1j R1 ¼ H, R2 ¼ Me
2h 74
2i 75
2j 79
3h 67
0.1
1
10
a) Yields of isolated products. b) Carried out at room temperature.
Scheme 1
Scheme 2
attacked by C(2) of the pyrrole ring to give the intermediate 5. Subsequent
deprotonation of 5 gives rise to 3.
The reaction of 1-[2-(1-methylethenyl)phenyl]-1H-pyrrole (2j) occurred scarcely at
08, but it proceeded slowly at room temperature to give the corresponding desired
product, 9,9-dimethyl-9H-pyrrolo[1,2-a]indole (3j), in rather low yield (Entry 10). This
result indicates that the benzyl cation intermediate (4, R2 ¼ Me) from 2j is less stable
than those (4, R2 ¼ Ar) from the other precursors 2a – 2i, which give particularly well-
stabilized benzylic carbocations.
It should be noted that all attempts to prepare 9-ethyl-9-phenyl-9H-pyrrolo[1,2-a]-
indole from 1-[2-(1-phenylprop-1-enyl)phenyl]-1H-pyrrole were unsuccessful; the
reaction with an equimolar amount of HI at 08 was extremely reluctant, and the

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reaction at elevated reaction temperature resulted in the formation of an intractable
mixture of products, from which only a trace amount of the desired product was
isolated as a mixture with structurally undefined products. Presumably, the Me
substituent in the b-position of the vinyl moiety of the starting material renders the
cyclization difficult.
In summary, we have demonstrated that the HI-catalyzed (or-mediated) cyclization
reaction of 1-[2-(1-aryl(or methyl)ethenyl)phenyl]-1H-pyrroles allows convenient
access to 9,9-disubstituted 9H-pyrrolo[1,2-a]indoles. The mild conditions, simplicity,
and efficiency makes this method attractive.
Experimental Part
General. All of the org. solvents used in this study were dried over appropriate drying agents and
distilled prior to use. TLC: Merck silica gel 60 PF254. Column chromatography (CC): Wako Gel C-200E.
M.p.: Laboratory Devices MEL-TEMP II melting-point apparatus; uncorrected. IR Spectra: Shimadzu
FT-IR-8300 spectrophotometer. NMR Spectra: JEOL ECP500 FT-NMR spectrometer (1H: 500 and 13C:
125 MHz); in CDCl3 with TMS as an internal reference. LR-MS (EI, 70 eV): JEOL JMS AX505 HA
spectrometer.
2-(Prop-1-en-2-yl)benzenamine (1j) was commercially available. 2-(1-Arylethenyl)benzenamines 1a
[5], 1c [6], 1d [7], 1f [5], 1g [5], 1h [8], and 1i [9] were prepared by the reported procedures. All other
chemicals used in this study were commercially available.
2-(1-Arylethenyl)benzenamines 1b and 1e. These compounds were prepared from 1-(2-amino-
phenyl)ethanone by a sequence practically same as that described for the preparation of the above 2-(1-
arylethenyl)benzenamines [5 – 9].
2-[1-(3-Methylphenyl)ethenyl]benzenamine (1b). 1-(2-Aminophenyl)ethanone was treated with
3.5 mol of 3-methylphenylmagnesium bromide in THF at 08 to give 1-(2-aminophenyl)-1-(3-methyl-
phenyl)ethanol. Yield: 99%. Yellow oil. Rf (CH2Cl2) 0.40. IR (neat): 3383, 1607. 1H-NMR: 1.86 (s, 3 H);
2.32 (s, 3 H); 3.67 (br. s, 2 H); 3.92 (br. s, 1 H); 6.65 (dd, J ¼ 8.2, 1.4, 1 H); 6.87 (ddd, J ¼ 7.8, 7.3, 1.4, 1 H);
7.05 (dd, J ¼ 7.3, 0.9, 1 H); 7.14 (ddd, J ¼ 7.8, 7.3, 1.4, 1 H); 7.17 – 7.20 (m, 2 H); 7.24 (s, 1 H); 7.41 (dd, J ¼
7.8, 1.4, 1 H). Anal. calc. for C15H17NO (227.30): C 79.26, H 7.54, N 6.16; found: C 79.16, H 7.63, N 5.94.
The above alcohol was dehydrated by heating at 1608 (neat) for 40 min to give 1b. Yield: 62%. Pale-
1
yellow oil. Rf (THF/hexane 1:10) 0.40. IR (neat): 3472, 3379, 1614. H-NMR: 2.32 (s, 3 H); 3.55 (br. s,
2 H); 5.33 (d, J ¼ 1.8, 1 H); 5.76 (d, J ¼ 1.8, 1 H); 6.69 (dd, J ¼ 7.8, 0.9, 1 H); 6.79 (ddd, J ¼ 7.8, 7.3, 0.9,
1 H); 7.11 (dd, J ¼ 7.8, 1.4, 2 H); 7.14 – 7.22 (m, 4 H). Anal. calc. for C15H15N (209.29): C 86.08, H 7.22, N
6.69; found: C 86.09, H 7.20, N 6.68.
2-[1-(3-Methoxyphenyl)ethenyl]benzenamine (1e). 1-(2-Aminophenyl)ethanone was treated with
3.5 mol of 3-methoxyphenylmagnesium bromide in THF at 08 to give 1-(2-aminophenyl)-1-(3-
methoxyphenyl)ethanol. Yield: 90%. Yellow oil. Rf (THF/hexane 1:5) 0.22. IR (neat): 3460, 3383,
1614. 1H-NMR: 1.86 (s, 3 H); 3.65 (br. s, 2 H); 3.78 (s, 3 H); 4.08 (br. s, 1 H); 6.65 (d, J ¼ 7.8, 1 H); 6.78
(dd, J ¼ 8.2, 2.3, 1 H); 6.88 (ddd, J ¼ 7.8, 7.3, 1.4, 1 H); 6.90 (dd, J ¼ 7.8, 1.8, 1 H); 7.04 (dd, J ¼ 2.3, 1.8,
1 H); 7.14 (ddd, J ¼ 7.8, 7.3, 1.4, 1 H); 7.21 (dd, J ¼ 8.2, 7.8, 1 H); 7.41 (dd, J ¼ 7.8, 1.4, 1 H). Anal. calc. for
C15H17NO2 (243.30): C 74.05, H 7.04, N 5.76; found: C 74.15, H 7.12, N 5.64.
The above alcohol was dehydrated by heating at 2208 (neat) for 20 min to give 1e. Yield: 63%.
Yellow solid. M.p. 60 – 628 (hexane/Et2O). IR (KBr): 3466, 3376, 1609. 1H-NMR: 3.55 (br. s, 2 H); 3.78 (s,
3 H); 5.36 (d, J ¼ 1.4, 1 H); 5.79 (d, J ¼ 1.4, 1 H); 6.68 (d, J ¼ 8.2, 1 H); 6.79 (ddd, J ¼ 7.8, 7.3, 0.9, 1 H);
6.84 (dd, J ¼ 8.2, 2.3, 1 H); 6.93 (dd, J ¼ 2.3, 1.4, 1 H); 6.95 (dd, J ¼ 7.8, 0.9, 1 H); 7.11 (dd, J ¼ 7.8, 0.9,
1 H); 7.15 (ddd, J ¼ 7.8, 7.3, 1.4, 1 H); 7.23 (dd, J ¼ 8.2, 7.8, 1 H). Anal. calc. for C15H15NO (225.29): C
79.97, H 6.71, N 6.22; found: C 79.72, H 6.72, N 6.13.
1-(2-Ethenylaryl)-1H-pyrroles 2. These compounds were prepared by reacting 1 with 2,5-
dimethoxytetrahydrofuran in AcOH at reflux temp. [4].

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1-[2-(1-Phenylethenyl)phenyl]-1H-pyrrole (2a). Colorless oil. Rf (Et2O/hexane 1:20) 0.63. IR
1
(neat): 1603. H-NMR: 5.06 (s, 1 H); 5.59 (d, J ¼ 0.9, 1 H); 6.28 (t, J ¼ 2.3, 2 H); 6.86 (t, J ¼ 2.3, 2 H);
7.28 – 7.36 (m, 9 H). Anal. calc. for C18H15N (245.32): C 88.13, H 6.16, N 5.71; found: C 88.10, H 6.20, N
5.63.
1-{2-[1-(3-Methylphenyl)ethenyl]phenyl}-1H-pyrrole (2b). Colorless oil. Rf (CHCl3/hexane 1:10)
0.36. IR (neat): 1614, 1601. 1H-NMR: 2.24 (s, 3 H); 5.17 (s, 1 H); 5.58 (s, 1 H); 6.02 (dd, J ¼ 2.3, 1.8, 2 H);
6.66 (dd, J ¼ 2.3, 1.8, 2 H); 6.94 (s, 1 H); 6.95 (d, J ¼ 7.8, 1 H); 6.99 (d, J ¼ 7.3, 1 H); 7.06 (dd, J ¼ 7.8, 7.3,
1 H); 7.33 (dd, J ¼ 7.8, 7.3, 1 H); 7.36 – 7.47 (m, 3 H). Anal. calc. for C19H17N (259.35): C 87.99, H 6.61, N
5.40; found: C 87.98, H 6.78, N 5.14.
1-{2-[1-(4-Methylphenyl)ethenyl]phenyl}-1H-pyrrole (2c). Colorless needles. M.p. 44 – 468 (hexane/
Et2O). IR (neat): 1609. 1H-NMR: 2.28 (s, 3 H); 5.14 (d, J ¼ 0.9, 1 H); 5.57 (d, J ¼ 0.9, 1 H); 6.03 (t, J ¼ 2.3,
2 H); 6.68 (t, J ¼ 2.3, 2 H); 6.98 (d, J ¼ 8.2, 2 H); 7.05 (d, J ¼ 8.2, 2 H); 7.31 – 7.42 (m, 4 H). Anal. calc. for
C19H17N (259.35): C 87.99, H 6.61, N 5.40; found: C 87.87, H 6.65, N 5.24.
1-{2-[1-(4-Chlorophenyl)ethenyl]phenyl}-1H-pyrrole (2d). Yellow oil. Rf (THF/hexane 1:15) 0.60.
1
IR (neat): 1614. H-NMR: 5.29 (s, 1 H); 5,57 (s, 1 H); 6.00 (dd, J ¼ 2.3, 1.8, 2 H); 6.61 (dd, J ¼ 2.3, 1.8,
2 H); 7.02 (d, J ¼ 8.7, 2 H); 7.10 (d, J ¼ 8.7, 2 H); 7.31 (dd, J ¼ 7.8, 0.9, 1 H); 7.35 – 7.45 (m, 3 H). Anal. calc.
for C18H14ClN (279.76): C 77.28, H 5.04, N 5.01; found: C 77.26, H 5.09, N 4.92.
1-{2-[1-(3-Methoxyphenyl)ethenyl]phenyl}-1H-pyrrole (2e). Colorless oil. Rf (Et2O/hexane 1:5)
0.60. IR (neat): 1599. 1H-NMR: 3.73 (s, 3 H); 5.22 (s, 1 H); 5.61 (s, 1 H); 6.03 (t, J ¼ 2.3, 2 H); 6.65 – 6.68
(m, 3 H); 6.72 – 6.75 (m, 2 H); 7.09 (dd, J ¼ 8.2, 7.8, 1 H); 7.31 – 7.43 (m, 4 H). Anal. calc. for C19H17NO
(275.34): C 82.88, H 6.22, N 5.09; found: C 82.65, H 6.34, N 5.03.
1-{2-[1-(4-Methoxyphenyl)ethenyl]phenyl}-1H-pyrrole (2f). Colorless oil. Rf (THF/hexane 1:10)
0.60. IR (neat): 1607. 1H-NMR: 3.75 (s, 3 H); 5.11 (d, J ¼ 0.9, 1 H); 5.33 (d, J ¼ 0.9, 1 H); 6.03 (t, J ¼ 2.3,
2 H); 6.67 (t, J ¼ 2.3, 2 H); 6.69 (d, J ¼ 8.7, 2 H); 7.08 (d, J ¼ 8.7, 2 H); 7.31 – 7.43 (m, 4 H). Anal. calc. for
C19H17NO (275.34): C 82.88, H 6.22, N 5.09; found: C 82.63, H 6.21, N 5.04.
1-{2-[1-(3,4-Dimethoxyphenyl)ethenyl]phenyl}-1H-pyrrole (2g). White solid. M.p. 74 – 768 (hexane/
Et2O). IR (KBr): 1607. 1H-NMR: 3.78 (s, 3 H); 3.83 (s, 3 H); 5.14 (s, 1 H); 5.52 (s, 1 H); 6.04 (dd, J ¼ 2.3,
1.8, 2 H); 6.63 – 6.67 (m, 4 H); 6.71 (d, J ¼ 1.8, 1 H); 7.32 (dd, J ¼ 7.8, 0.9, 1 H); 7.34 – 7.43 (m, 3 H). Anal.
calc. for C20H19NO2 (305.37): C 78.66, H 6.27, N 4.59; found: C 78.59, H 6.41, N 4.51.
1-[4-Chloro-2-(1-phenylethenyl)phenyl]-1H-pyrrole (2h). White solid. M.p. 62 – 638 (hexane/Et2O).
IR (KBr): 1611. 1H-NMR: 5.25 (s, 1 H); 5.62 (s, 1 H); 6.00 (t, J ¼ 2.3, 2 H); 6.60 (t, J ¼ 2.3, 2 H); 7.10 – 7.12
(m, 2 H); 7.15 – 7.19 (m, 3 H); 7.25 (d, J ¼ 9.2, 1 H); 7.38 – 7.40 (m, 2 H). Anal. calc. for C18H14ClN
(279.76): C 77.28, H 5.04, N 5.01; found: C 77.27, H 5.01, N 4.91.
1-[4-Methoxy-2-(1-phenylethenyl)phenyl]-1H-pyrrole (2i). White solid. M.p. 51 – 528 (hexane). IR
(KBr): 1611. 1H-NMR: 3.85 (s, 3 H); 5.21 (s, 1 H); 5.57 (s, 1 H); 5.98 (t, J ¼ 1.8, 2 H); 6.56 (t, J ¼ 1.8, 2 H),
6.91 – 6.95 (m, 2 H); 7.14 – 7.18 (m, 5 H); 7.23 (d, J ¼ 8.2, 1 H). Anal. calc. for C19H17NO (275.34): C 82.88,
H 6.22, N 5.09; found: C 82.61, H 6.24, N 5.02.
1-[2-(Prop-1-en-2-yl)phenyl]-1H-pyrrole (2j). Colorless liquid. Rf (Et2O/hexane 1:20) 0.71. IR
(neat): 1600. 1H-NMR: 1.54 (s, 3 H); 5.06 (s, 1 H); 5.09 (s, 1 H); 6.28 (dd, J ¼ 2.3, 1.8, 2 H); 6.86 (dd, J ¼
2.3, 1.8, 2 H); 7.26 – 7.35 (m, 4 H). Anal. calc. for C13H13N (183.25): C 85.21, H 7.15, N 7.64; found: C 84.93,
H 7.21, N 7.53.
9H-Pyrrolo[1,2-a]indoles 3. General Procedure. To a stirred soln. of 2 (1.0 mmol) in MeCN (12 ml)
at 08 was added conc. HI (the quantity as indicated in the Table). After stirring for the time indicated in
Table 1, sat. aq. NaHCO3 (10 ml) and 10% aq. Na2S2O3 (5 ml) were added, and MeCN was evaporated.
The org. materials were extracted with Et2O (3 ꢁ 10 ml), and the combined extracts were washed with
brine (10 ml) and dried (Na2SO4). After evaporation of the solvent, the residue was purified by CC
(SiO2) to give 3.
9-Methyl-9-phenyl-9H-pyrrolo[1,2-a]indole (3a). Pale-yellow oil. Rf (Et2O/hexane 1:20) 0.53. IR
(neat): 1615. 1H-NMR: 1.91 (s, 3 H); 6.01 (dd, J ¼ 2.7, 0.9, 1 H); 6.39 (dd, J ¼ 2.7, 2.3, 1 H); 7.04 – 7.09 (m,
2 H); 7.18 (tt, J ¼ 7.3, 1.4, 1 H); 7.24 – 7.28 (m, 5 H); 7.32 (dd, J ¼ 7.8, 1.4, 2 H). 13C-NMR: 26.81; 48.96;
101.19; 109.52; 109.84; 113.47; 123.59; 124.80; 126.21; 126.55; 127.66; 128.39; 139.44; 144.91; 145.13;
145.39. MS: 245 (45, Mþ), 230 (100). Anal. calc. for C18H15N (245.32): C 88.13, H 6.16, N 5.71; found: C
87.85, H 6.31, N 5.58.

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9-Methyl-9-(3-methylphenyl)-9H-pyrrolo[1,2-a]indole (3b). Yellow oil. Rf (hexane) 0.27. IR (neat):
1614. 1H-NMR: 1.89 (s, 3 H); 2.28 (s, 3 H); 6.01 (dd, J ¼ 3.2, 1.4, 1 H); 6.39 (dd, J ¼ 3.2, 2.7, 1 H); 7.00 (d,
J ¼ 7.8, 1 H); 7.04 – 7.08 (m, 2 H); 7.11 – 7.17 (m, 3 H); 7.24 – 7.29 (m, 3 H). 13C-NMR: 21.59; 26.90; 48.87;
101.14; 109.43; 109.79; 113.42; 123.28; 123.55; 124.78; 126.88; 127.34; 127.57; 128.26; 137.90; 139.41;
144.98; 145.00; 145.45. MS: 259 (51, Mþ), 244 (100). Anal. calc. for C19H17N (259.35): C 87.99, H 6.61, N
5.40; found: C 87.95, H 6.65, N 5.11.
9-Methyl-9-(4-methylphenyl)-9H-pyrrolo[1,2-a]indole (3c).Yellow oil. Rf (Et2O/hexane 1:20) 0.50.
1
IR (neat): 1614. H-NMR: 1.88 (s, 3 H); 2.28 (s, 3 H); 6.00 (dd, J ¼ 3.2, 0.9, 1 H); 6.38 (t, J ¼ 3.2, 1 H);
7.03 – 7.07 (m, 3 H); 7.20 (d, J ¼ 8.2, 2 H); 7.23 – 7.29 (m, 4 H). 13C-NMR: 20.88; 26.81; 48.64; 101.05;
109.42; 109.79; 113.42; 123.56; 124.70; 126.08; 127.55; 129.07; 136.12; 139.39; 142.16; 145.08; 145.54. MS:
259 (45, Mþ), 244 (100). Anal. calc. for C19H17N (259.35): C 87.99, H 6.61, N 5.40; found: C 87.93, H 6.72,
N 5.31.
9-(4-Chlorophenyl)-9-methyl-9H-pyrrolo[1,2-a]indole (3d). Pale-yellow solid. M.p. 76 – 788 (hexane/
Et2O). IR (KBr): 1616. 1H-NMR: 1.88 (s, 3 H); 5.99 (d, J ¼ 3.2, 1 H); 6.38 (dd, J ¼ 3.2, 2.7, 1 H); 7.06 –
7.08 (m, 2 H); 7.20 – 7.31 (m, 7 H). 13C-NMR: 26.63; 48.46; 101.25; 109.70; 109.94; 113.57; 123.69; 124.62;
127.68; 127.87; 128.45; 132.41; 139.37; 143.75; 144.46; 144.88. MS: 279 (45, Mþ), 264 (100). Anal. calc. for
C18H14ClN (279.76): C 77.28, H 5.04, N 5.01; found: C 77.08; H 5.06; N 4.95.
9-(3-Methoxyphenyl)-9-methyl-9H-pyrrolo[1,2-a]indole (3e).Yellow oil. Rf (CH2Cl2/hexane 1:5)
0.25. IR (neat): 1607. 1H-NMR: 1.88 (s, 3 H); 3.74 (s, 3 H); 6.02 (dd, J ¼ 2.3, 1.4, 1 H); 6.38 (dd, J ¼ 3.2,
2.8, 1 H); 6.72 (dt, J ¼ 8.2, 0.9, 1 H); 6.89 – 6.91 (m, 2 H); 7.05 – 7.08 (m, 2 H); 7.18 (dd, J ¼ 8.3, 7.8, 1 H);
7.20 – 7.28 (m, 3 H). 13C-NMR: 26.82; 48.92; 55.12; 101.24; 109.51; 109.82; 111.06; 112.90; 113.45; 118.77;
123.55; 124.75; 127.66; 129.34; 141.75; 144.65; 145.12; 146.81; 159.51. MS: 275 (43, Mþ), 260 (100). Anal.
calc. for C19H17NO (275.34): C 82.88, H 6.22, N 5.09; found: C 82.84, H 6.34, N 5.09.
9-(4-Methoxyphenyl)-9-methyl-9H-pyrrolo[1,2-a]indole (3f). Pale-yellow solid. M.p. 108 – 1108
1
(hexane/Et2O). IR (KBr): 1616. H-NMR: 1.87 (s, 3 H); 3.75 (s, 3 H); 5.99 (dd, J ¼ 3.2, 0.9, 1 H); 6.38
(t, J ¼ 3.2, 1 H); 6.79 (d, J ¼ 9.2, 2 H); 7.04 – 7.07 (m, 2 H); 7.22 – 7.27 (m, 5 H). 13C-NMR: 26.94; 48.33;
55.20; 100.98; 109.41; 109.79; 113.42; 113.69; 123.35; 123.63; 127.26; 127.54; 137.23; 139.33; 145.18; 145.60;
158.20. MS: 275 (38, Mþ), 260 (100). Anal. calc. for C19H17NO (275.34): C 82.88, H 6.22, N 5.09; found: C
82.66, H 6.26, N 4.92.
9-(3,4-Dimethoxyphenyl)-9-methyl-9H-pyrrolo[1,2-a]indole (3g). White solid. M.p. 135 – 1378
1
(hexane). IR (KBr): 1609. H-NMR: 1.88 (s, 3 H); 3.76 (s, 3 H); 3.83 (s, 3 H); 6.02 (dd, J ¼ 3.2, 0.9,
1 H); 6.39 (t, J ¼ 3.2, 1 H); 6.77 (d, J ¼ 8.7, 1 H); 6.78 (d, J ¼ 2.3, 1 H); 6.93 (dd, J ¼ 8.7, 2.3, 1 H); 7.05 –
7.09 (m, 2 H); 7.27 – 7.28 (m, 3 H). 13C-NMR: 27.17; 48.65; 55.84; 55.93; 101.11; 109.48; 109.84; 110.13;
110.96; 113.44; 118.29; 123.54; 124.62; 127.61; 137.72; 139.31; 144.93; 145.32; 147.79; 148.69. MS: 305 (37,
Mþ), 290 (100). Anal. calc. for C20H19NO2 (305.37): C 78.66, H 6.27, N 4.59; found: C 78.77, H 6.11, N 4.61.
7-Chloro-9-methyl-9-phenyl-9H-pyrrolo[1,2-a]indole (3h). Yellow oil. Rf (CH2Cl2/hexane 1:10)
0.44. IR (neat): 1614. 1H-NMR: 1.89 (s, 3 H); 6.00 (dd, J ¼ 3.2, 0.9, 1 H); 6.39 (dd, J ¼ 3.2, 2.7, 1 H); 7.02
(d, J ¼ 2.7, 1 H); 7.17 – 7.30 (m, 8 H). 13C-NMR: 26.62; 49.13; 101.65; 109.67; 110.64; 113.95; 125.26;
126.13; 126.84; 127.70; 128.54; 128.80; 138.01; 144.33; 145.26; 146.77. MS: 279 (36, Mþ), 284 (100). Anal.
calc. for C18H14ClN (279.76): C 77.28, H 5.04, N 5.01; found: C 77.23, H 5.11, N 4.88.
7-Methoxy-9-methyl-9-phenyl-9H-pyrrolo[1,2-a]indole (3i). Pale-yellow solid. M.p. 71 – 738 (hex-
1
ane). IR (KBr): 1597. H-NMR: 1.89 (s, 3 H); 3.77 (s, 3 H); 5.98 (d, J ¼ 3.2, 1 H); 6.35 (dd, J ¼ 3.2, 2.3,
1 H); 6.79 (dd, J ¼ 8.7, 2.3, 1 H); 6.82 (d, J ¼ 2.3, 1 H); 7.00 (d, J ¼ 2.3, 1 H); 7.18 (d, J ¼ 8.2, 1 H), 7.19 (d,
J ¼ 7.3, 1 H); 7.26 (dd, J ¼ 7.8, 7.3, 2 H); 7.31 (d, J ¼ 7.8, 2 H). 13C-NMR: 26.81; 49.18; 55.76; 101.01;
109.22; 110.03; 111.77; 111.98; 122.80; 126.19; 126.56; 128.40; 133.48; 145.09; 145.27; 146.45; 156.60. MS:
275 (34, Mþ), 260 (100). Anal. calc. for C19H17NO (275.34): C 82.88, H 6.22, N 5.09; found: C 82.85, H
6.47, N 4.95.
9,9-Dimethyl-9H-pyrrolo[1,2-a]indole (3j). Pale-yellow solid. M.p. 56 – 588 (hexane). IR (KBr):
1618. 1H-NMR: 1.51 (s, 6 H); 6.02 (d, J ¼ 3.2, 1 H); 6.36 (dd, J ¼ 3.2, 2.7, 1 H); 7.00 (dd, J ¼ 2.7, 0.9, 1 H);
7.10 (td, J ¼ 7.3, 1.4, 1 H); 7.22 (d, J ¼ 7.3, 1 H); 7.27 (td, J ¼ 7.3, 1.4, 1 H); 7.32 (d, J ¼ 7.3, 1 H). 13C-NMR:
28.00; 41.24; 99.27; 109.23; 109.66; 113.02; 123.19; 123.31; 127.35; 139.41; 145.47; 146.35. MS: 183 (22,
Mþ), 178 (100). Anal. calc. for C13H13N (183.25): C 85.21, H 7.15, N 7.64; found: C 85.06, H 7.24, N 7.53.

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Helvetica Chimica Acta – Vol. 94 (2011)
We thank Mrs. Miyuki Tanmatsu for recording the mass spectra and performing combustion
analyses.
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Received February 28, 2011