One pot synthesis of substituted dihydroindeno[1,2-b]indoles and dihydrobenzo[a]carbazoles by photostimulated reactions of o-iodoaniline with carbanions by the SRN1 mechanism

Article abstract of DOI:10.1002/jhet.5570430325

The photostimulated reaction of enolate anions of cyclic aromatic ketones such as substituted indan-1-ones and 3,4-dihydro-2H-naphthalen-1-one with o-iodoaniline in DMSO affords 1-, 2-, 3-, and 4-methoxy-5,10-dihydroindeno[1,2- b]indoles (34-40%), 1,2-, 1,4-, and 2,3-dimethoxy-5,10-dihydroindeno[1,2-b]- indoles (31-43%), and 1-, 2-, and 3-methoxy-5,11-dihydro-6H-benzo[a]carbazoles (42-61%) by the S_RN1 mechanism in one pot reactions.

Full text of DOI:10.1002/jhet.5570430325

May-Jun 2006
695
One Pot Synthesis of Substituted Dihydroindeno[1,2-b]indoles and
Dihydrobenzo[a]carbazoles by Photostimulated Reactions of o-
Iodoaniline with Carbanions by the SRN1 Mechanism
Silvia M. Barolo,a Ceciré Rosales,b Jorge E. Angel Guío,b and Roberto A. Rossi*a
a INFIQC, Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba. Ciudad Universitaria 5000
Córdoba, Argentina. b Departamento de Química. Laboratorio de Síntesis Orgánica y Diseño de Fármacos. Facultad Experimental de Ciencias. La
Universidad del Zulia. Maracaibo, República Bolivariana de Venezuela
Received September 19, 2005
O
R1
I
hν
+
NH2
DMSO
R2
n
R1= OMe, R2= H
R1= R2= OMe
n=1
n=2
H
N
R1
31-61%
( )n
R2
The photostimulated reaction of enolate anions of cyclic aromatic ketones such as substituted indan-1-
ones and 3,4-dihydro-2H-naphthalen-1-one with o-iodoaniline in DMSO affords 1-, 2-, 3-, and 4-methoxy-
5,10-dihydroindeno[1,2-b]indoles (34-40%), 1,2-, 1,4-, and 2,3-dimethoxy-5,10-dihydroindeno[1,2-b]-
indoles (31-43%), and 1-, 2-, and 3-methoxy-5,11-dihydro-6H-benzo[a]carbazoles (42-61%) by the SRN
mechanism in one pot reactions.
1
J. Heterocyclic Chem., 43, 695 (2006).
Introduction.
have been widely employed providing increased func-
tional group tolerance and improved yields. In this field,
the preparation of 2-aryl and 2-heteroaryl indoles from 1-
alkynes and o-iodotrifluoroacetanilide by a copper-
catalyzed coupling-cyclization process has been reported
more recently [8].
The indole nucleus is present in a family of compounds
known to be pharmacologically active as well as in a
broad number of other bioactive molecules [1]. This fact
accounts for the continued interest in developing new,
efficient, and selective synthetic pathways toward these
compounds [2].
The radical nucleophilic substitution mechanism
(SRN1) is another interesting methodology through
which different indoles have been obtained. Within
this approach, one of the most widely studied path-
ways to ring closure reactions is the SRN1 substitution
of aromatic compounds that have an appropriate sub-
stituent ortho- to the leaving group [9]. Following this
methodology, the indole synthesis is based on the elec-
tron transfer catalyzed nucleophilic substitution of an
aromatic halide that bears an amino group ortho- to
the leaving halide. The substitution product obtained
by reaction of this type of substrates with carbanions
from acyclic aliphatic and aromatic ketones spontane-
ously cyclizes to furnish 2-substituted indoles in good
yields, as indicated for o-iodoaniline (1) in equation 1
[10,11].
Classical approaches to indole synthesis include
the Fischer method [3]. Within this methodology,
the preparation of the N-arylhydrazones used as
substrates has recently been improved by means of
palladium catalysis [4]. Another approach utilized
in acidic media is the Bischler synthesis, which has
been modified in the last years by Moody [5]. More
recently, a new pathway toward the regioselective
synthesis of functionalized indoles and six-
membered benzo-fused N-, O-, and S- heterocycles
has been proposed. The key step of this procedure
involves the generation of a benzyne-tethered vinyl
or aryllithium compound that undergoes a subse-
quent intramolecular anionic cyclization to afford
indoles and tetrahydrocarbazoles, among other het-
erocycles [6].
In the indole synthesis area, as in others of organic syn-
thesis, the contribution of transition-metal chemistry has
been very important. Thus, transition-metal-based reac-
tions and particularly palladium-catalyzed protocols [7]
I
hν
CH2COR
+
R
(1)
N
NH2
H
1

696
S. M. Barolo, C.Rosales, J. E. Angel Guío, and R.A. Rossi
Vol 43
The scope of the SRN1 mechanism in ring closure reac-
different mono and disubstitution positions is being re-
port. The value of this approach is based on the fact that
methoxy functionalized tetracyclic indoles can be easily
prepared under mild conditions in one-pot reaction from
readily accessible starting materials. Besides, the presence
of methoxy-substituents on indole or carbazole nucleus
might change their biological activity. For instances, some
methoxy indole alkaloids exhibit strong effects on the
nervous system [15]. Extensive studies on indole bioiso-
steres of melatonin have demonstrated that suitable
spaced methoxy moieties are important for binding and
activation of the melatonin receptors [16].
tions is based on the excellent yields of new C-C bond
formation usually achieved by reaction of unactivated
aromatic and heteroaromatic substrates (halides being the
most widely used leaving groups) with carbanions
[12,13], where the reactions are usually performed under
photo-initiation in liquid ammonia or in DMSO as sol-
vents.
The mechanism is a chain process depicted in Scheme
1. The initiation step is an electron transfer from the nu-
cleophile to the substrate to afford a radical anion (2). In
some systems the electron transfer step is spontaneous,
but in others light is required to induce the reaction. The
propagation steps consist of the fragmentation of the radi-
cal anion 2 to afford an aromatic radical 3 and the nucleo-
fugal group. The radical 3 then couples with the nucleo-
phile to afford a radical anion 4, which by electron trans-
fer to the substrate forms the intermediate necessary to
continue the propagation cycle. Overall, Scheme 1 depicts
a nucleophilic substitution in which radicals and radical
anions are intermediates.
Results and Discussion.
Following the SRN1 approach, substrate 1 was reacted
under irradiation with the enolate anion of methoxy-
indan-1-ones (7a-d) to give methoxy-5,10-dihydroindeno-
[1,2-b]indoles (8a-d) in 34-40% yield (experiments 1-4,
Table 1) (equation 3).
Unfortunately, in addition to the desired product, we
also observed aniline. A plausible route to this compound
is the reduction of the radicals by hydrogen abstraction
from ammonia [17].
Scheme 1
Initiation Step
O
H
N
7
CH3O
CH3O
4
1
hν
(ArX)
6
5
ArX + Electron Donor
(3)
2
3
2
1 +
2
DMSO
3
4
Propagation Steps
1
2
Ar + X
3
7a, 4-methoxy
7b, 5-methoxy
7c, 6-methoxy
7d, 7-methoxy
8a, 1-methoxy
8b, 2-methoxy
8c, 3-methoxy
8d, 4-methoxy
+ Nu
(ArNu)
3
4
+ ArX
ArNu +
4
2
Similar yields are observed when the dimethoxy deriva-
tives of the indan-1-ones are employed as nucleophiles.
The 4,5-, 4,7-, and 5,6-dimethoxy derivatives 9a-c were
inspected. The photostimulated reaction of these nucleo-
philes with 1 gives dimethoxy-5,10-dihydro[1,2-b]indoles
(10a-c) in 31-43% yields (experiments 5-7, Table 1)
(equation 4).
Fused indoles are important molecules due to their
pharmaceutical applications. Besides, they can also be
precursors to other planar molecules. Within this subject
we have previously informed about the SRN1 synthesis,
with good yields, of 5,10-dihydroindeno[1,2-b]indole (6a)
and 5,11-dihydro-6H-benzo[a]carbazole (6b) by photo-
stimulated reaction of enolate ions of 1-indanone (5a)
and 1-tetralone (5b) respectively, with 1 in DMSO or in
liquid ammonia (equation 2) [14].
H
N
O
CH3O
CH3O
CH3O
hν
(4)
1 +
DMSO
CH3O
O
H
N
9a, 4,5-dimethoxy
9b, 4,7-dimethoxy
9c, 5,6-dimethoxy
10a, 1,2-dimethoxy
10b, 1,4-dimethoxy
10c, 2,3-dimethoxy
hν
(2)
1
+
)
(
n
( )
n
The preparation of methoxy carbazoles was also
achieved. The photostimulated reaction of 1 with
methoxy-3,4-dihydro-2H-naphthalen-1-one enolate ions
(11a-c) in DMSO affords methoxy-5,11-dihydro-6H-
benzo[a]carbazoles (12a-c) in 42-61% yields (ex-
periments 8-10, Table 1) (equation 5).
5a, n=1
5b, n=2
6a, n=1
6b, n=2
We now report an extension of our methodology to the
synthesis of methoxy substituted dihydroindeno[1,2-b]-
indoles and dihydrobenzo[a]carbazoles. A wide range of

May-Jun 2006
Synthesis of Dihydroindenoindoles and Dihydrobenzocarbazoles
697
Table 1
Photostimulated Reaction of 1 with Ketone Enolate Ions [a]
equipped with two 400-W lamps emitting maximally at 350 nm
(Philips Model HPT, air and water refrigerated). Potentiometric
titration of halide ions was performed in a pH meter using an
Ag/Ag+ electrode.
t-BuOK was commercially available and used as received.
DMSO was distilled under vacuum and stored over molecular
sieves (4Å). o-Iodoaniline, 5-methoxy-3,4-dihydro-2H-naphth-
alen-1(2H)-one (11a), 6-methoxy-3,4-dihydro-2H-naphthalen-
1(2H)-one (11b), and 7-methoxy-3,4-dihydro-2H-naphthalen-
1(2H)-one (11c) were commercially available and distilled
under reduced pressure in the Kügelrohr. The substituted
1-indanones 7a-d, and 9a-c, were prepared according to well
established methods [18-24].
1
Nucleophile
(mmol)
X-
Indole
(%)[c]
Aniline
(%)[c]
Expt.
(mmol)
(%)[b]
1
2
3
0.50
0.75
0.75
0.50
0.62
0.62
0.55
0.50
0.50
0.50
7a (2.00)
7b (3.00)
7c (3.00)
7d (2.00)
9a (2.50)
9b (2.50)
9c (2.20)
11a (2.00)
11b (2.00)
11c (2.00)
98
87
93
100
99
92
93
94
93
93
8a (34)
8b (40)
8c (35) [d]
8d (34)
37
37
34
49
37
46
41
40
45
36
4
5
6
10a (43)
10b (31)
10c (43)
12a (61)
12b (42)
12c (49)
7
8
9
10
4-Methoxyindan-1-one (7a). mp 102° (lit [18] mp 103-104°);
1H nmr (CDCl3): ꢀ 7.33 (m, 2H), 7.01 (m, 1H), 3.89 (s, 3H),
3.02 (t, 2H), 2.64 (t, 2H).
[a] Photostimulated reactions carried out under N2 at 40°C in 10 mL of
DMSO. [b] Determined potentiometrically. [c] Determined by GC by
the internal standard method. [d] Isolated yield.
5-Methoxyindan-1-one (7b). mp 101° (lit [19] mp 108-
1
110.5º); H nmr (CDCl3): ꢀ 7.67 (m, 2H), 6.88 (m, 1H), 3.86 (s,
3H), 3.07 (t, 2H), 2.66 (t, 2H).
6-Methoxyindan-1-one (7c). mp 105-107° (lit [19] mp 108-
1
108.5°, lit [20] 107-109°); H nmr (CDCl3): ꢀ 7.35 (dd, 3H, J =
O
8.2, 2.5 Hz), 7.17 (d, 1H, J = 2.5 Hz), 7.15 (d, 1H, J = 8.2 Hz),
3.76 (s, 3H), 3.05 (t, 2H), 2.70 (t, 2H).
HN
CH3O
8
5
CH3O
4
hν
3
2
7
1
4
(5)
1
2
1 +
DMSO
7-Methoxyindan-1-one (7d). mp 104° (lit [21] mp 108°); H
6
3
nmr (CD3COCD3): ꢀ 7,49 (t, 1H, J = 7.7, 7.9 Hz), 6.99 (1H, d, J
= 7.4 Hz ), 6.79 (d, 1 H, J = 8.2 Hz), 3.93 (s, 3H), 3.06 (t, 2H),
2.65 (t, 2H).
1
11a, 5-methoxy
11b, 6-methoxy
11c, 7-methoxy
12a, 1-methoxy
12b, 2-methoxy
12c, 3-methoxy
4,5-Dimethoxyindan-1-one (9a). mp 78-79° (lit [22] 82°, lit
1
[23] mp 74-75°); H nmr (CDCl3): ꢀ 7.15 (d, 2H), 3.90 (s, 3H),
3.85 (s, 3H), 3.00 (t, 2H), 2.63 (t, 2H).
4,7–Dimethoxyindan-1-one (9b). mp 122-124° (lit [24] mp
1
Conclusions.
124-125°); H mnr (CD3COCD3): ꢀ 6.98 (d, 1H), 6.72 (d, 1H),
3.88 (s, 3H), 3.84 (s, 3H), 2.96 (t, 2H), 2.65 (t, 2H).
The photostimulated reactions of several mono- and di-
substituted cyclic ketone enolate ions derived from 1-
tetralone and 1-indanone with substrate 1 in DMSO afford
fused indoles in acceptable yields by the SRN1 mechanism
(34-61%) together with the reduced product aniline. Con-
sidering the availability/simplicity of the starting materials,
and the readiness of the procedure, this reaction becomes a
valid alternative to the synthesis of tetracyclic indoles.
The wide range of mono- and dimethoxy substitution posi-
tions covered makes the system of special interest in the field
of biological assays and in synthetic organic chemistry.
5,6-Dimethoxyindan-1-one (9c). mp 117-120° (lit [19] mp
118.8-119.5º, lit [23] 117-119º); 1H nmr (CDCl3): ꢀ 7.15 (s, 1H),
6.86 (s, 1H), 3.94 (s, 3H), 3.87 (s, 3H), 3.02 (t, 2H), 2.64 (t, 2H).
General Procedure for the Photostimulated Reaction of Ketone
Enolate Ions 7a-d, 9a-c, and 11a-c with o-Iodoaniline (1).
The following procedure is representative of all these reac-
tions. They were carried out in a 20 mL three-neck round-
bottomed flask equipped with a nitrogen inlet and magnetic
stirrer. To 10 mL of dry and degassed DMSO under nitrogen
was added 2.02 mmol (0.227 g) of t-BuOK and 2.0 mmol (0.352
g) of 3,4-dihydro-1-methoxy-2H-naphthalen-1-one (11a). After
15 minutes 1 (0.50 mmol, 0.109 g) was added and the reaction
mixture was irradiated for 180 minutes. The reaction was
quenched with an excess of ammonium nitrate and water (60
mL). The mixture was extracted three times with methylene
chloride (20 mL each), the organic extract was washed twice
with water, dried over Na2SO4, and quantified by gc using the
internal standard method. The iodide ions in the aqueous solu-
tion were determined potentiometrically. In other experiments,
the solvent was removed under reduced pressure. From the re-
maining residue product purification was accomplished by radial
tlc (eluted with petroleum ether (60-80°C):acetone).
EXPERIMENTAL
1H nmr (200.13 MHz) and 13C nmr (50.32 MHz) spectra were
recorded on a Bruker AC 200 nuclear magnetic resonance spec-
trometer with CDCl3, CD3COCD3 or DMSO-d6 as solvent. Cou-
pling constants (J) are given in Hz units. Mass spectra were
obtained with a GC/MS Shimadzu QP5050A. Melting points
were recorded on Büchi 510 and were uncorrected. Gas chroma-
tographic analyses were performed with a Hewlett Packard 5890
series II with a flame ionization detector using a HP1 column
(0.53 mm x 5m) and a HP data system. The purification of the
products was done with radial tlc using silica gel 60 PF-254 with
calcium sulfate (Merck). The distillation at reduced pressure was
performed in a Kügelrohr. Irradiation was performed in a reactor
1-Methoxy-5,10-dihydroindeno[1,2-b]indole (8a).
Compound 8a was purified by radial tlc. It was recrystallized
1
from benzene. White needles, mp 156-157º; H nmr (CDCl3): ꢀ

698
S. M. Barolo, C.Rosales, J. E. Angel Guío, and R.A. Rossi
Vol 43
8.23 (s, 1H), 7.66-7.62 (m, 1H), 7.42-7.07 (m, 5H), 6.79 (d, 1H,
J = 8.0 Hz), 3.93 (s, 3H), 3.67 (s, 2H); 13C nmr (CDCl3): ꢀ
156.05, 143.22, 140.69, 136.46, 134.22, 128.26, 124.76, 121.93,
121.63, 120.18, 118.96, 112.04, 110.74, 107.86, 55.36, 27.51;
ms: m/z 236 (17), 235 (100), 234 (18), 220 (19), 205 (11), 204
(63), 192 (16), 191 (25), 190 (12), 118 (15), 102 (17), 96 (13).
Anal. Calcd. for C16H13NO: C, 81.68; H, 5.57; N, 5.95. Found:
C, 81.52; H, 5.58; N, 5.77.
(48), 250 (91), 235 (42), 234 (22), 233 (15), 220 (34), 219 (21),
190 (14), 178 (14), 177 (14), 89 (18), 76 (22), 75 (16). HRMS:
(EI) Anal. Calcd for C17H15NO2: 265.1103. Found: 265.0978.
Anal. Calcd. for C17H15NO2: C, 76.96; H, 5.70; N, 5.28.
Found: C, 76.85; H, 5.71; N, 5.24.
1,4-Dimethoxy-5,10-dihydro-[1,2-b]indole (10b).
Compound 10b was purified by radial tlc. It was recrystal-
1
lized from benzene. Light yellow needles, mp 136-137º; H nmr
2-Methoxy-5,10-dihydroindeno[1,2-b]indole (8b).
(DMSO-d6): ꢀ 11.25 (s, 1H), 7.53 (dd, 1H, J = 6.4, 3.3 Hz), 7.49
(dd, 1H, J = 6.6, 2.9 Hz), 7.11-6.98 (m, 2H), 6.93 (d, 1H, J = 9.0
Hz), 6.8 (d, 1H, J = 9.0 Hz), 3.91 (s, 3H), 3.83 (s, 3H), 3.59 (s,
2H); 13C nmr (DMSO-d6): ꢀ 150.18, 146.68, 141.64, 140.99,
134.63, 125.07, 123.72, 120.40, 119.11, 118.27, 118.14, 112.64,
110.43, 108.65, 55.93, 55.50, 27.39; ms: m/z 266 (19), 265
(100), 250 (49), 235 (20), 234 (32), 222 (28), 207 (30), 191 (13),
179 (10), 178 (13), 133 (10), 76 (10).
Compound 8b was purified by radial tlc. It was recrystallized
from ethyl alcohol, white crystals, mp 225-226º dec; H nmr
1
(DMSO-d6): ꢀ 11.43 (s, 1H), 7.52-7.39 (m, 3H), 7.18 (s, 1H),
7.08-6.97 (m, 2H), 6.92 (dd, 1H, J = 8.0, 2.2 Hz), 3.8 (s, 3H),
3.65 (s, 2H); 13C nmr (DMSO-d6): ꢀ 157.54, 149.59, 143.42,
140.21, 128.19, 124.36, 120.30, 119.19, 118.11, 118.06, 112.29,
112.21, 112.16, 111.94, 55.31, 30.03; ms: m/z 236 (17), 235
(100), 234 (12), 221 (15), 220 (91), 192 (24), 191 (38), 190 (19),
118 (12), 96 (16). HRMS: (EI) Anal. Calcd for C16H13NO:
235.0997. Found: 235.1032.
Anal. Calcd. for C17H15NO2: C, 76.96; H, 5.70; N, 5.28.
Found: C, 76.77; H, 5.84; N, 5.30.
2,3-Dimethoxy-5,10-dihydro-[1,2-b]indole (10c).
Anal. Calcd. for C16H13NO: C, 81.68; H, 5.57; N, 5.95. Found:
C, 81.44; H, 5.48; N, 5.69.
Compound 10c was purified by chromatography on silica
gel. Recrystallization from hexane:1,2-dichloroethane pro-
3-Methoxy-5,10-dihydroindeno[1,2-b]indole (8c).
1
duces light yellow crystals, mp 234-235º dec; H nmr (DMSO-
Compound 8c was purified by radial tlc. Recrystallization
from benzene produces a white needle crystals, mp 206-207º
dec; 1H NMR (CDCl3): ꢀ 8.24 (s, 1H), 7.64-7.59 (m, 1H), 7.41-
7.35 (m, 2H), 7.22-7.10 (m, 2H), 7.01 (d, 1H, J = 2.6 Hz), 6.75
(dd, 1H, J = 8.0, 2.6 Hz), 3.86 (s, 3H), 3.64 (s, 2H); 13C nmr
(CDCl3): ꢀ 158.99, 143.06, 140.66, 139.88, 136.16, 125.73,
124.76, 123.22, 121.79, 120.23, 118.99, 112.06, 109.94, 103.84,
55.57, 29.54; ms: m/z 236 (18), 235 (100), 234 (16), 220 (40),
219 (11), 204 (47), 192 (25), 191 (36), 190 (18), 118 (14), 96
(16). HRMS: (EI) Calcd for C16H13NO: 235.0997. Found:
235.1009.
d6): ꢀ 11.38 (s, 1H), 7.51-7.40 (m, 2H), 7.24 (s, 1H), 7.23 (s,
1H), 7.07-6.97 (m, 2H), 3.84 (s, 3H), 3.81 (s, 3H), 3.59 (s,
2H); 13C nmr (DMSO-d6): ꢀ 148.06, 146.90, 143.99, 140.19,
139.83, 127.84, 124.39, 120.05, 119.14, 118.65, 117.90,
112.18, 110.67, 102.48, 55.91, 55.72, 29.65; ms: m/z 266 (18),
265 (100), 250 (53), 222 (36), 221 (35), 220 (21), 204 (17),
191 (14), 179 (13), 178 (15), 132 (19), 110 (10), 102 (10), 96
(14), 89 (11), 76 (22).
HRMS: (EI) Anal. Calcd for
C17H15NO2: 265.1103. Found: 265.1115.
Anal. Calcd. for C17H15NO2: C, 76.96; H, 5.70; N, 5.28.
Found: C, 76.81; H, 5.80; N, 5.27.
Anal. Calcd. for C16H13NO: C, 81.68; H, 5.57; N, 5.95. Found:
C, 81.76; H, 5.60; N, 5.71.
1-Methoxy-5,11-dihydro-6H-benzo[a]carbazole (12a).
Compound 12a was purified by radial tlc. It was recrystallized
from benzene as white crystals, mp: 141-142º; 1H nmr (CDCl3):
ꢀ 8.13 (s, 1H), 7.55 (d, 1H, J = 7.0 Hz), 7.37-7.33 (m, 1H), 7.25-
7.07 (m, 3H), 6.96 (d, 1H, J = 7.7 Hz), 6.79 (d, 1H, J = 8.0 Hz),
3.86 (s, 3H), 3.12-2.90 (m, 4H); 13C nmr (CDCl3): ꢀ 157.05,
137.00, 132.95, 129.91, 127.48, 127.02, 124.22, 122.30, 119.83,
118.80, 112.77, 112.58, 111.04, 109.53, 55.57, 21.37, 19.05; ms:
m/z 250 (18), 249 (100), 248 (97), 247 (13), 233 (25), 218 (11),
217 (17), 205 (16), 204 (40), 117 (28), 108 (19), 102 (27), 88
(11).
4-Methoxy-5,10-dihydroindeno[1,2-b]indole (8d).
Compound 8d was purified by radial TLC. It was recrystal-
1
lized from ethyl alcohol. White needles, mp 177-178º; H mnr
(CDCl3): ꢀ 8.57 (s, 1H), 7.63-7.57 (m, 1H), 7.47-7.39 (m, 1H),
7.17-7.12 (m, 4H), 6.89-6.81 (m, 1H), 3.97 (s, 3H), 3.72 (s, 2H);
13C nmr (CDCl3): ꢀ 152.25, 149.47, 142.39, 140.47, 126.05,
124.57, 124.19, 120.99, 119.96, 119.31, 118.59, 118.50, 111.98,
108.67, 55.44, 30.67; ms: m/z 236 (18), 235 (100), 234 (13), 221
(12), 220 (74), 204 (23), 192 (31), 191 (32), 190 (17), 118 (17),
102 (12), 96 (27). HRMS: (EI) Anal. Calcd for C16H13NO:
235.0997. Found: 235.1002.
Anal. Calcd. for C17H15NO: C, 81.90; H, 6.06; N, 5.62. Found:
C, 81.98; H, 6.06; N, 5.53
Anal. Calcd. for C16H13NO: C, 81.68; H, 5.57; N, 5.95. Found:
C, 81.65; H, 5.33; N, 5.97.
2-Methoxy-5,11-dihydro-6H-benzo[a]carbazole (12b).
Compound 12b was purified by radial tlc. It was recrystal-
lized from benzene. White crystals, mp 168-169º (lit [25] mp
169º); H nmr (CDCl3): ꢀ 8.05 (br.s, 1H); 7.53-7.49 (cplx.m,
1H); 7.35-7.30 (cplx.m, 1H); 7.22-7.06 (cplx.m, 3H); 6.84 (d,
1H, J = 2.6); 6.74 (dd, 1H, J s= 8.4, 2.6); 3.8 (s, 3H); 3.07-2.89
(m, 4H); 13C nmr (CDCl3): ꢀ 158.67, 138.53, 136.78, 133.17,
127.62, 122.09, 121.77, 120.88, 119.80, 118.37, 114.92, 111.34,
110.93, 110.80, 55.30, 29.99, 19.67; ms: m/z 250(18), 249
(100), 248 (83), 247 (27), 234 (20), 233 (20), 217 (12), 205 (18),
204 (47), 124 (12), 117 (26), 108 (21), 102 (34), 88 (12).
1,2-Dimethoxy-5,10-dihydro[1,2-b]indole (10a).
1
Compound 10a was purified by radial tlc. It was recrystallized
1
from benzene. White needles, mp 184-186º; H nmr (CDCl3): ꢀ
8.22 (s, 1H), 7.58 (dd, 1H, J = 5.8, 2.9 Hz), 7.42-7.34 (m, 1H),
7.18-7.12 (m, 2H), 7.09 (d, 1H, J = 8.0 Hz), 6.86 (d, 1H, J = 8.0
Hz), 3.99 (s, 3H), 3.90 (s, 3H), 3.76 (s, 2H); 13C nmr (CDCl3): ꢀ
150.82, 146.35, 142.95, 140.53, 139.91, 129.42, 124.92, 121.26,
120.55, 120.20, 118.59, 112.58, 111.93, 111.15, 60.34, 56.30,
27.81; ms: m/z 266 (19), 265 (100), 264 (14), 263 (46), 252

May-Jun 2006
Synthesis of Dihydroindenoindoles and Dihydrobenzocarbazoles
699
[6] J. Barluenga, F. J. Fananas, R Sanz and Y. Fernandez, Chem.
Eur. J., 8, 2034 (2002).
Anal. Calcd. for C17H15NO: C, 81.90; H, 6.06; N, 5.62. Found:
C, 82.19; H, 6.00; N, 5.65.
[7] Aminopalladation-reductive elimination domino reaction
review: [a] G. Battistuzzi, S. Cacch and Fabrizi, G., Eur. J. Org. Chem.,
2671 (2002); [b] K. Onitsuka, S. Suzuki and S. Takahashi, Tetrahedron
Lett., 43, 6197 (2002).
[8] S Cacchi,. G. Fabrizi and L. M. Parisi, Org. Lett., 5, 3843
(2003).
[9] R. A Rossi and M. T. Baumgartner, In Targets in Heterocyc-
lic Systems: Chemistry and Properties, Vol 3, O. A. Attanasi, D.
Spinelli, Eds., Soc. Chimica Italiana, Italy, 1999, pp 215-243.
[10a] R. Beugelmans and G. Roussi, Tetrahedron, 37, 393 (1981);
[b] R. R. Bard and J. F. Bunnett, J. Org. Chem., 45, 1546 (1980).
[11] M. T. Baumgartner, M. A. Nazareno, M. C Murguia, A. B.
Pierini and R. A. Rossi, Synthesis, 2053 (1999).
3-Methoxy-5,11-dihydro-6H-enzo[a]carbazole (12c).
Compound 12c was purified by radial tlc. It was recrystallized
from benzene. White crystals, mp 126-127º (lit [26] mp 131-
133º); 1H nmr (CDCl3): ꢀ 8.12 (s, 1H), 7.54 (d, 1H, J = 7.5 Hz),
7.33 (d, 1H, J = 7.0 Hz), 7.20-7.07 (m, 3H), 6.86 (d, 1H, J = 2.6
Hz), 6.69 (dd, 1H, J = 8.0, 2.6 Hz), 3.82 (s, 3H), 2.94 (s, 2H);
13C nmr (CDCl3): ꢀ 158.50, 137.00, 132.98, 129.80, 129.13,
128.72, 127.43, 122.39, 119.83, 118.80, 113.25, 111.18, 111.09,
106.49, 55.38, 28.62, 19.91; ms: m/z 250 (18), 249 (100), 248
(100), 247 (30), 234 (11), 233 (19), 217 (21), 205 (25), 204 (51),
117 (12), 109 (12), 108 (11), 102 (26), 88 (11).
[12] For reviews, see: [a] R. A Rossi, A. B. Pierini and A. B.
Peñéñory, in The Chemistry of Functional Groups, Chapter 24, S. Patai
and Z. Rappoport, Eds., Wiley, Chichester, Supplement D2, 1995, pp
1395-1485; [b] R. A. Rossi, A. B. Pierini and A. N. Santiago, in Organic
Reactions Vol. 54, L. A. Paquette and R Bittman, Eds., Wiley & Sons:
1999, pp 1-271; [c] R. A Rossi, A. B. Pierini and A. B. Peñéñory, Chem.
Rev., 103, 71 (2003); [d] R. A. Rossi, in Synthetic Organic Photochemis-
try, Chapter 15, A. G. Griesberck and J. Mattay, Eds., Marcel Dekker,
New York, 2005, Vol 12, pp 495-527.
[13a] M. T. Baumgartner, M. H. Gallego and A. B. Pierini, J. Org.
Chem., 63, 6394 (1998); [b] M. A. Nazareno and R. A. Rossi, Tetrahe-
dron Lett., 35, 5185 (1994); [c] E. Austin, C. G. Ferrayoli, R. A. Alonso
and R. A. Rossi, Tetrahedron, 49, 4495 (1993).
Anal. Calcd. for C17H15NO: C, 81.90; H, 6.06; N, 5.62.
Found: C, 82.12; H, 5.79; N, 5.48.
Acknowledgement.
This work was supported in part by the Consejo de Investiga-
ciones de la Provincia de Córdoba (CONICOR), the Consejo
Nacional de Investigaciones Científicas y Técnicas (CONICET),
SECYT, Universidad Nacional de Córdoba, and FONCYT, Ar-
gentina. We thank L. CONDES-LUZ CC 0158-06, FONACIT,
Venezuela. S.M.B. gratefully acknowledges receipt of a fellow-
ship from CONICET.
[14] S. M. Barolo, A. E. Lukach and R. A. Rossi, J. Org. Chem.,
68, 2807 (2003).
[15] L. Lipin´ska, Tetrahedron Lett., 45, 8831 (2004), and refer-
ences cited therein.
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