Reactivity of heterocyclic enaminones: Regioselective synthesis of polyfused indolones

Article abstract of DOI:10.3987/COM-99-8837

Photocyclization of heterocyclic enaminones to give partial hydrogenated derivatives of indolo[2,3-c]quinoline, pyrido[2,3-c]carbazole, and pyrido[4,3-a]carbazole is described. In addition, 3-[(5'-quinolinyl)- benzylamino]cyclohex-2-en-1-one and 3-[(8'-quinolinyl)benzylamino]cyclohex-2- en-1-one undergo C-N bond cleavages and a benzyl migration on the C-6 and C-7 positions respectively.

Full text of DOI:10.3987/COM-99-8837

HETEROCYCLES, Vol. 53, No. 4, 2000, pp. 905 - 916, Received, 22nd December, 1999
REACTIVITY OF HETEROCYCLIC ENAMINONES: REGIOSELECTIVE
SYNTHESIS OF POLYFUSED INDOLONES
a
Yves Blache, * Véronique Benezech,a Jean-Michel Chezal,b Pierre Boule,c
Henri Viols,a Olivier Chavignon,b Jean-Claude Teulade,b and Jean-Pierre
Chapata
aLaboratoire de Chimie Organique Pharmaceutique, E.A. 2414, 15 Avenue
Charles Flahault, Faculté de Pharmacie, 34060 Montpellier, France.
bLaboratoire de Chimie Organique Pharmaceutique, UFR de Pharmacie, 28
Place Henry Dunant, B.P. 38, 63001 Clermont-Ferrand, France. cLaboratoire de
Photochimie Moléculaire et Macromolécuclaire, UFR des Sciences, 63177
Aubière Cedex, France
Abstract- Photocyclization of heterocyclic enaminones to give partial
hydrogenated derivatives of indolo[2,3-c]quinoline, pyrido[2,3-c]carbazole, and
pyrido[4,3-a]carbazole is described. In addition, 3-[(5'-quinolinyl)-
benzylamino]cyclohex-2-en-1-one and 3-[(8'-quinolinyl)benzylamino]cyclohex-
2-en-1-one undergo C-N bond cleavages and a benzyl migration on the C-6 and C-
7 positions respectively.
Introduction
Interest in the chemistry of pyridocarbazoles and indoloquinolines has increased this last decade since
these skeletons are present in a large number of alkaloids of biological interests. For example, the
indoloquinoline type alkaloids quindoline (1) and cryptolepine (2) extracted from the roots of Cryptolepis
Sanguinolenta1 have been shown to exhibit promising in vitro and in vivo antiplasmodial activities2
(Scheme 1). However, poor works have been conducted to increase the activities of such alkaloids by
slight modifications of the heterocyclic nucleus.3 As an example of such possible modifications, it was
shown, in the acridine series, that the tetrahydro derivatives possessing a carbonyl group on the C-1
position (floxacrine type compounds (4) exhibited higher activities on Plasmodium berghei than the

parent mepacrine type compounds (3).4 As a part of our program concerning the elaboration of analogs of
natural products,5 we are interested in the chemistry as well as in the biological activities of such modified
heterocyles. Our methodology resides in the photocyclizations of enaminones6 derived from diverses
amino-heterocyles to give polyfused indolones. In this context, we had previously described the reactions
of enaminones respectively derived from 3-aminopyridines7 and from 2-aminopyridines8 to give the
corresponding pyridoindolones as synthetic intermediates for the synthesis of analogs of
murrayaquinones.9 Poor regioselectivities were found in these reactions. As a continuation of these
studies, we now report the regioselective synthesis of partial hydrogenated polyfused indolones which can
be further implicated in the synthesis of a new class of antiplasmodial pyridocarbazoles and
indoloquinolines.
Scheme 1
R
N
N
1 quindoline R = H
2 cryptolepine R= CH3
2
3
R
R
O
N
O
N
N
3
R
1
1
R
4
R
R
2
R
3 "mepacrine" type
4 "floxacrine" type
Results and discussion
The required N-[quinolinyl]enaminones (10, 11, 12, and 13)and N-[isoquinolinyl]enaminone (14), were
obtained with good yields from the corresponding 3-amino-, 5-amino-, 6-amino-, 8-aminoquinolines, and
5-aminoisoquinoline (5, 6, 7, 8 and 9) respectively by condensation with 1,3-cyclohexanedione in
refluxing toluene according to our previous methodology.7,8 Subsequent protection of the nitrogen atom
was achieved by treatment of the secondary enaminones with sodium hydride in refluxing toluene
followed by addition of 1.1 equivalent of benzyl chloride to give 15, 16, 17, 18, and 19 (Scheme 2).

Scheme 2
O
O
R4
R2
N
(i)
(ii)
Het
Het
N
N
R3
R1
Bn
H
15 Het= 3-quinolinyl
16 Het= 5-quinolinyl
17 Het= 6-quinolinyl
18 Het= 8-quinolinyl
5 R1=NH2, R2=R3=R4=H
6 R2=NH2, R1=R3=R4=H
7 R3=NH2, R1=R2=R4=H
8 R4=NH2, R1=R2=R3=H
10 Het= 3-quinolinyl
11 Het= 5-quinolinyl
12 Het= 6-quinolinyl
13 Het= 8-quinolinyl
O
N
(i)
N
R
N
NH2
14 R=H
19 R=Bn
9
(ii)
(i) 1,3-cyclohexanedione, toluene, p-TSA, reflux
(ii) a: NaH, toluene b: C6H5CH2Cl
Photochemical studies: Irradiation of tertiary enaminones (15 and 17). The reactions were conducted
by irradiating with "black light" (see experimental section) in a Pyrex immersion well apparatus. Optimal
conditions were obtained with methanol as a solvent. Under these conditions, compounds (15 and 17) led
to regioselectives reactions on the C-15 positions giving respectively 20 and 21 with 75 and 60% yields
(Scheme 3).
Scheme 3
6
O
1
5
2
3
2
4
O
1
3
14
11
15
N
Y
4
10
9
13
12
Bn
7
(i)
8
X
5
9
N
Y
X
8
6
11
10
Bn
15 X=N, Y=CH
17 X=CH, Y=N
20 X=N, Y=CH
21 X=CH, Y=N
-10 h for 15
-14 h for 17
reagents and conditions : hυ("black light", Pyrex), MeOH

1
Position of cyclization on the C-15 position of 15 to give 20 was easily determined by H-NMR which
showed a characteristic singlet of H-6 at δ 8.86, while the signal of H-1 was shifted downfield (δ 9.92,
multiplet) by the proximity of the carbonyl group. In the case of compound (21), a similar deshielding
effect was observed on H-1 which appeared as a doublet at δ 10.44 (J = 8.5 Hz).
Irradiation of enaminones (16, 18 and 19): In order to appreciate the influence of the position of the
intracyclic nitrogen atom on such reactions, we were interested in the reactivity of the enaminones (16, 18
and 19). While 16 and 18 were recovered unchanged under irradiation in a Pyrex reactor, compound (19)
led to the formation of the pyridocarbazole (22) (best result obtained in acetonitrile by irradiating in the
range 290-350 nm (maximum at 313 nm)). Change of the solvents and wavelenght was no more effective
for 16, while in the case of 18, irradiation in methanol in the range 290-350 nm led to a reductive cleavage
of the C-N bond to give 23 13 (scheme 4).
Scheme 4
O
(i)
N
X
Y
N
Bn
Z
22
9
Bn
H
O
N
N
Bn
N
(ii)
16 X=N; Y,Z=CH
18 X,Z=CH; Y=N
19 X,Y=CH, Z=N
23
(i) Z= N, hυ,
(ii) Y= N, hυ,
MeOH, 10 h, 365 nm, ("black light,Pyrex)
MeOH, 2 h, 313 nm (Pyrex)
These results clearly indicate the dramatic effect of the presence of a nitrogen atom adjacent to the
benzene ring, while in the case of the isoquinoline ring, the cyclization occurred in a satisfactory manner
(yield 65%). Such differences of reactivity are not surprising since it has been demonstrated in the
benzene series itself, that yields of photocyclizations can be greatly dependant of the nature, and the
position of substituents on the aromatic ring.14 An interesting problem arised with the differences of
reactivity observed for 16 and 18 and with the unexpected formation of compound (23) through a
C(enaminone)-N bond cleavage. With respect to the general pathways described for the photolysis of tertiary

amines,15 we can reasonably suppose that such cleavage occurred through a radical process. In the case of
16, no reaction was found at 313 nm, while in the case of 18, photoinduced homolysis of C(enaminone)-N
bond occurred, indicating that the strengh of such bond is greatly affected by the position of the
intracyclic nitrogen atom. In a last attempt, reactions of 16 and 18 were investigated at 254 nm. When
compound (18) was irradiated for 30 min at 254 nm, 8-aminoquinoline (8) was isolated admixed with 23
and 8-amino-7-benzylquinoline (27) (Scheme 5).
Scheme 5
General reaction pathways for homolysis of N-benzyl derivatives
Homolysis of 18
hυ
313 nm
N
N
N
N
O
N
N
Bn
23
Bn
Bn
H
18
23
hυ / quartz
C6H5 CH2
+
8
N
H
24
N
25
H
hydrogen transfer
24 +
N
N
NH2
NH2
27
26
Homolysis of 23 and 28
X
Y
X
hυ / quartz
Y
Bn
N
NH2
Bn
H
27 Y=N, X=CH (32%)
(admixed with 8 (9%))
29 Y=N, X=CH (6%)
(admixed with 6 (26%))
23 Y=N, X=CH
28 X=N, Y=CH

Formation of 27 occurred through homolysis of the C(benzyl)-N bond to give the intermediary species (24)
and (25). Radical species (25) could further undergo a photoinduced 1,3-hydrogen transfer to give the
radical species (26) which, by coupling with 24, gave compound (27). In this pathway, 8-aminoquinoline
could be produced either through 25 and 26. This result was confirmed by studying the homolysis of 23
(obtained by N-benzylation of 8) which led to a mixture of 27 (major product) and 8. These results are in
good agreement with those obtained recently by Siskos and co-workers16 and earlier by Ogata and co-
workers17 who described the photoinduced homolysis of N-benzylaniline at 254 nm to give such an ortho
(or para) benzyl migration. In the case of 16 such photolysis did not occurred, and starting material was
recovered unchanged, while in the same conditions, the N-benzyl derivative (28)18 (obtained from 6 by N-
benzylation) underwent a C(benzyl)-N bond cleavage to give 6 as the major compound. In this case, benzyl
migration occurred on C-6 position to give 29 as the minor compound. These results indicate that the
strengh of the C(benzyl)-N bond is greatly increased by the presence the enaminone moiety.
Conclusion
Formation of fused indolones from 3, 6-aminoquinolines and 5-aminoisoquinoline heterocycles by means
of photocyclization of enaminones is a remarkable process occuring with a total regioselectivity in the
crucial step. In addition, when the electrocyclic ring closure did not occur, a photoinduced homolysis of
C(enaminone)-N bond was observed, and the strengh of such bond is found to be dependent of the nature of
the heterocycle. Furthermore, the strengh of C(benzyl)-N bond is greatly increased by the presence of the
enaminone moiety, and photoinduced homolysis of such bond is only permitted after an initial C(enaminone)
-
N bond cleavage.
EXPERIMENTAL
Melting points were determined on a Büchi capillary melting point apparatus and are not corrected. Elemental
analysis was perfomed by Microanalytical Center, ENSCM, Montpellier. Spectral measurements were taken
using the following instruments: 1H-NMR spectra were taken on Brüker AC 100 or WM 360 or EM 400WB;
13C-NMR spectra were obtained at 26°C with proton noise decoupling at 25 MHz with a Brüker AC 100
instrument. Chemical shifts are expressed relative to residual chloroform. MS spectra were recorded on a
LKB 2091 spectrometer at 15eV [θ(source)=180°C]. Dichloromethane was dried over activated alumina and
distilled from calcium hydride.
3-[3'-Quinolinylamino]cyclohex-2-en-1-one (10) : A solution of 3-aminoquinoline (5) (1 g, 7.7 mmol),
1,3-cyclohexanedione (0.95 g, 8.46 mmol), and p-toluenesulfonic acid monohydrate (70 mg, 0.39 mmol)
in 100 mL of anhydrous toluene was refluxed with a Dean-Stark for 3 h. After cooling, the solution was

basified (10% Na2CO3) and extracted with dichloromethane. Organic layers were dried over sodium
sulfate and evaporated in vacuo. Recrystallisation of the yellow paste from ethanol gave 1.28 g (77%) of
10 ; mp 171-173°C ; 1H NMR (CDCl3, 400 MHz) δ 1.92 (m, 2 H), 2.28 (t, 2 H, J = 6.4 Hz), 2.53 (t, 2 H,
J = 6.0 Hz), 5.65 (s, 1 H), 7.41 (t, 1 H, J = 7.3 Hz), 7.56 (m, 2 H), 7.83 (d, 1 H, J = 1.9 Hz), 7.93 (d, 1 H,
J = 8.4 Hz), 8.66 (d, 1 H, J = 1.9 Hz), 8.80 (s, 1 H). 13C NMR (CDCl3, 100 MHz) δ 21.6, 29.2, 36.5, 99.6,
127.2, 127.3, 127.5, 127.7, 128.8 (2 carbons), 132.2, 145.1, 147.2, 163.3, 198.8. Anal. Calcd for
C15H14N2O : C 75.60, H 5.93, N 11.76. Found : C 75.53, H 5.99, N 11.71.
3-[5'-Quinolinylamino]cyclohex-2-en-1-one (11): This compound was obtained in 61% yield from 5-
1
aminoquinoline (6) according to the general procedure used for the synthesis of 10; mp 118-120°C; H
NMR (CDCl3, 100 MHz) δ 1.94 (m, 2 H) 2.19 (t, 2 H, J = 6.2 Hz), 2.56 (t, 2 H, J = 4.65 Hz), 4.85 (s, 1
H), 7.27 (m, 2 H), 7.51 (t, 1 H, J = 7.9 Hz), 7.88 (d, 1 H, J = 8.3 Hz), 8.14 (d, 1 H, J = 8.3 Hz), 8.75 (m,
13
2 H); C NMR (CDCl3, 25 MHz) δ 21.6, 24.1, 35.9, 99.0, 121.1, 124.4, 124.7, 127.8, 128.9, 131.6,
134.1, 148.1, 150.2, 166.1, 198.3. Anal. Calcd for C15H14N2O : C 75.60, H 5.93, N 11.76. Found: C
75.67, H 6.01, N 11.63.
3-[6'-Quinolinylamino]cyclohex-2-en-1-one (12): This compound was obtained in 80% yield from 6-
aminoquinoline (7) according to the general procedure used for the synthesis of 10; brown paste; 1H NMR
(CDCl3, 100 MHz) δ 1.89 (m, 2 H), 2.27 (t, 2 H, J = 5.8 Hz), 2.51 (t, 2 H, J = 5.4 Hz), 5.60 (s, 1 H), 7.10-
7.38 (m, 3 H), 7.87 (m, 2 H), 8.65 (d, 1 H, J = 5.0 Hz), 8.94 (s, 1 H); 13C NMR (CDCl3, 25 MHz) δ 21.3,
28.8, 35.9, 98.8, 119.3, 121.3, 126.1, 128.2, 129.3, 135.6, 136.6, 144.7, 149.0, 163.5, 199.0. Anal. Calcd
for C15H14N2O : C 75.60, H 5.93, N 11.76. Found C 75.81, H 5.85, N 11.82.
3-[8'-Quinolinylamino]cyclohex-2-en-1-one (13): This compound was obtained in 59% yield from 8-
1
aminoquinoline (8) according to the general procedure used for the synthesis of 10; mp 115-117°C; H
NMR (CDCl3, 100 MHz) δ 1.90 (m, 2 H), 2.33 (t, 2 H, J = 5.7 Hz), 2.53 (t, 2 H, J = 5.2 Hz), 5.91 (s, 1
13
H), 7.25 (m, 3H), 7.45 (m, 1 H), 7.95 (d, 1 H, J = 8.3 Hz), 8.62 (d, 1 H, J = 3.7 Hz), 8.72 (s,1 H); C
NMR (CDCl3, 25 MHz) δ 20.7, 25.7, 35.5, 100.9, 115.7, 120.4, 120.7, 125.3, 127.2, 134.2, 135.2, 138.3,
147.2, 158.2, 197.2. Anal. Calcd for C15H14N2O : C 75.60, H 5.93, N 11.76. Found : C 75.71, H 5.79, N
11.70.
3-[5'-Isoquinolinylamino]cyclohex-2-en-1-one (14): This compound was obtained in 78% yield from 5-
aminoisoquinoline (9) according to the general procedure used for the synthesis of 10; mp 219-221°C; 1H
NMR (CDCl3, 100 MHz) δ: 1.95 (m, 2 H), 2.22 (t, 2 H, J = 5.7 Hz), 2.59 (t, 2 H, J = 5.4 Hz), 4.88 (s, 1

H), 7.39-7.45 (m, 2 H), 7.60 (d, 1 H, J = 5.9 Hz), 7.78 (dd, 1 H, J = 6.0 and 3.2 Hz), 8.39 (d, 1 H, J = 5.9
13
Hz), 8.74 (br s, 1 H), 9.16 (s, 1 H); C NMR (CDCl3, 25 MHz) δ 21.7, 28.6, 36.2, 99.2, 115.6, 126.3,
126.8, 128.0, 128.9, 131.7, 133.3, 152.4, 165.3, 198.0. Anal. Calcd for C15H14N2O : C 75.60, H 5.93, N
11.76. Found : C 75.51, H 5.79, N 11.71.
3-[(3'-Quinolinyl)benzylamino]cyclohex-2-en-1-one (15): Compound (10) (0.5 g, 2.1 mmol) was added
to a suspension of sodium hydride (85 mg, 2.1 mmol, 60% in mineral oil) in anhydrous toluene (50 mL).
The mixture was refluxed for 2 h and cooled to rt. Benzyl chloride (265 mg, 2.1 mmol) was then added
and the mixture was refluxed for 2 h. Solvent was removed and the residue washed with water. After
extraction with dichloromethane, the organic layers were dried over sodium sulfate and evaporated in
vacuo. The crude product was chromatographed on silica gel using an ether/methanol mixture (85/15) as
eluent to give 0.62 g (90%) of 15 as a yellow oil ; 1H NMR (CDCl3, 100 MHz) δ 2.00 (m, 2 H), 2.36 (m,
4 H), 4.97 (s, 2 H), 5.49 (s, 1 H), 7.30 (m, 5 H), 7.57-7.82 (m, 3 H), 7.96 (d, 1 H, J = 2.2 Hz), 8.13 (d, 1
13
H, J = 8.4 Hz), 8.75 (d, 1 H, J = 2.2 Hz); C NMR (CDCl3, 25 MHz) δ 21.6, 27.8, 35.3, 55.8, 102.0,
126.1 (2 carbons), 126.7, 126.8, 127.0 (2 carbons), 128.0 (2 carbons), 128.4, 129.2, 132.6, 135.2, 136.8,
145.7, 149.4, 163.8, 196.6. Anal. Calcd for C22H20N2O : C 80.45, H 6.14, N 8.53. Found : C 80.29, H
6.01, N 8.39.
3-[(5'-Quinolinyl)benzylamino]cyclohex-2-en-1-one (16): This compound was obtained in 82% yield
1
from 11 according the general procedure used for the synthesis of 15 ; (brown paste); H NMR (CDCl3,
100 MHz) δ 1.94 (m, 2 H), 2.34 (m, 4 H), 4.63 (d, 1 H, J = 15.7 Hz), 5.19 (d, 1 H, J = 15.7 Hz), 5.57 (s, 1
H), 7.17-7.70 (m, 8 H), 7.93 (m, 3 H), 8.97 (d, 1 H, J = 3.0 Hz); 13C NMR (CDCl3, 25 MHz) δ 21.9, 27.5,
35.6, 56.1, 100.9, 121.9, 125.4, 126.7, 127.3 (2 carbons), 128.3 (3 carbons), 128.7, 129.6, 130.6, 135.4,
139.7, 148.7, 150.6, 165.2, 197.5. Anal. Calcd for C22H20N2O: C 80.45, H 6.14, N 8.53. Found : C 80.54,
H 6.11, N 8.63.
3-[(6'-Quinolinyl)benzylamino]cyclohex-2-en-1-one (17): This compound was obtained in 84% yield
1
from 12 according to the general procedure used for the synthesis of 15 ; (brown oil); H NMR (CDCl3,
100 MHz) δ 1.91 (m, 2 H), 2.32, (m, 4 H), 4.91 (s, 2 H), 5.41 (s, 1 H), 7.22-7.59 (m, 8 H), 8.07 (d, 2 H, J
13
= 8.5 Hz), 8.85 (d, 1 H, J = 3.7 Hz); C NMR (CDCl3, 25 MHz) δ 22.2, 28.3, 35.7, 56.4, 101.9, 121.5,
125.5, 126.5 (2 carbons), 127.2, 128.0, 128.4 (2 carbons), 129.0, 130.7, 135.6, 135.7, 141.8, 146.3, 150.6,
164.5, 197.5. Anal. Calcd for C22H20N2O : C 80.45, H 6.14, N 8.53. Found : C 80.48, H 6.22, N 8.38.
3-[(8'-Quinolinyl)benzylamino]cyclohex-2-en-1-one (18): this compound was obtained in 72% yield
1
from 13 according to the general procedure used for the synthesis of 15 ; (brown oil); H NMR (CDCl3,

100 MHz) δ 1.89 (m, 2 H), 2.29 (m, 4 H), 5.06 (s, 2 H), 5.60 (s,1 H), 7.31 (m, 5 H), 7.40 (m, 3 H), 7.87
(dd, 1 H, J = 6.8 and 2.2 Hz), 8.27 (d, 1 H, J = 8.3 Hz), 9.04 (d, 1 H, J = 3.2 Hz); 13C NMR (CDCl3, 25
MHz) δ 21.6, 27.4, 35.5, 56.1, 100.1, 121.3, 125.5, 126.5 (3 carbons), 127.8 (3 carbons), 129.0, 129.21,
135.9, 136.1, 140.4, 143.6, 150.2, 165.8, 196.7. Anal. Calcd for C22H20N2O : C 80.45, H 6.14, N 8.53.
Found : C 80.61, H 5.99, N 8.51.
3-[(5'-Isoquinolinyl)benzylamino]cyclohex-2-en-1-one (19): This compound was obtained in 86% yield
1
from 14 according to the general procedure used for the synthesis of 15 ; (brown oil); H NMR (CDCl3,
100 MHz) δ 1.98 (m, 2 H), 2.35 (t, 1 H, J = 5.8 Hz), 4.69 (d, 1 H, J = 15.2 Hz), 5.21 (d, 1 H, J = 15.2
13
Hz), 5.30 (s, 1 H), 7.27-7.72 (m, 11 H), 8.59 (d, 1 H, J = 8.5 Hz); C NMR (CDCl3, 25 MHz) δ 21.7,
27.2, 35.4, 55.5, 100.7, 114.6, 126.6, 126.9 (2 carbons), 127.0, 127.5, 128.0 (2 carbons), 129.0, 130.3,
132.6, 135.3, 143.7, 152.5, 164.8, 196.9. Anal. Calcd for C22H20N2O : C 80.45, H 6.14, N 8.53. Found: C
80.54, H 6.09, N 8.67.
General methods for photochemical reactions: Three different devices were used to irradiate solutions
in UV light. One of them used for tertiary enaminones (15) and (17) consists in 3 "black light" lamps
Philips HPW 125W surrounded by a cylindrical mirror, the reactor in Pyrex with a cooling jacket being
located along the axis of the device. The active part of the lamp is a medium pressure mercury lamp; Its
emission if filtered by the black bulb. About 85% of transmitted photons correspond to the line 365 nm.
Only a few percents of photons are emitted at 334 and 313 nm. In the second device 6 fluorescent low
pressure lamps DUKE GL 20 (20 W) are surrounded by a cylindrical mirror, the reactor being on the axis.
With a reactor in quartz, solutions are irradiated in the range 275-350 nm, the maximum being located at
313 nm. With a reactor in Pyrex, wavelengths shorter than 290 nm are cut off. In the third device, a
medium pressure mercury lamp was used (150W, TQ 150) with a quartz reactor, allowing the emissions
lower than 290 nm.
7-Benzyl-8,9,10,11-tetrahydroindolo[2,3-c]quinolin-11-one (20): A solution of enaminone (15) (208
mg, 0.63 mmol) in 100 mL of methanol was irradiated under nitrogen for 10 h in a Pyrex reactor with
Philips HPW lamps (main emission at 365 nm). After evaporation of the solvents, the resulting
precipitate was recrystallized in ether to give 144 mg (70%) of 20; mp 197-199°C. IR (KBr) : υ CO = 1650
1
cm-1. MS; m/z (relative intensity) : 326 (10), 298 (5), 235 (3), 91 (100). H NMR (CDCl3, 400 MHz) δ
2.26 (m, 2 H), 2.74 (t, 2 H, J = 6.4 Hz), 2.81 (t, 2 H, J = 6.1 Hz), 5.27 (s, 2 H), 6.97 (m, 1 H), 7.31 (m, 4
H), 7.47 (m, 2 H), 8.23 (m, 1 H), 8.86 (s, 1 H,), 9.92 (m, 1 H). 13C NMR (CDCl3, 25 MHz) δ 22.6 (2
carbons), 34.6, 47.2, 115.4, 123.4, 125.9, 126.3, 127.3, 128.2, 128.4, 129.2, 129.3, 129.9, 135.2, 135.7,

144.5, 152.5, 193.2. Anal. Calcd for C22H18N2O : C 80.96, H 5.56, N 8.58. Found : C 80.81, H 5.49, N
8.47.
7-Benzyl-8,9,10,11-tetrahydropyrido[2,3-c]carbazol-11-one (21): A solution of enaminone (17) (95
mg, 0.29 mmol) in 140 mL of methanol was irradiated under nitrogen for 14.5 h in a Pyrex reactor with
Philips HPW lamps (main emission at 365 nm). After evaporation of the solvent, the resulting precipitate
was recrystallized in ether to give 46 mg (60%) of 21; mp 174-176°C. IR (KBr) : υ CO = 1650 cm-1. MS ;
1
m/z (relative intensity) : 326 (12), 298 (2), 235 (3), 207 (7), 179 (8), 91 (100). H NMR (CDCl3, 400
MHz) δ 2.30 (m, 2 H), 2.76 (t, 2 H, J = 6.2 Hz), 2.98 (t, 2 H, J = 6.0 Hz), 5.46 (s, 2 H), 7.03 (d, 1 H, J =
7.0 Hz), 7.33 (m, 4 H), 7.59 (dd, 1 H, J = 8.5 and 4.2 Hz), 7.67 (d, 1 H, J = 9.0 Hz), 8.00 (d, 1 H, J = 9.0
Hz), 8.93 (d, 1 H, J = 4.2 Hz), 10.44 (d, 1 H, J= 8.5 Hz). 13C NMR (CDCl3, 25 MHz) δ 22.9, 23.0, 39.2,
47.2, 114.0, 120.4, 120.8, 124.2, 125.9, 126.1, 128.1, 129.3, 133.7, 135.6, 137.0, 146.0, 148.2, 151.1,
193.5. Anal. Calcd for C22H18N2O : C 80.96, H 5.56, N 8.58. Found : C 81.05, H 5.56, N 8.61.
5-Benzyl-6,7,8,9-tetrahydropyrido[4,3-a]carbazol-9-one (22): A solution of enaminone (19) (20 mg,
0.06 mmol) in 100 mL of acetonitrile was irradiated under nitrogen for 25 min in the range 290-350 nm in
a Pyrex reactor. After evaporation of the solvent, the resulting precipitate was purified by chromatography
on neutral alumina eluted with dichloromethane to give 13 mg (65%) of 22 ; mp 225-227°C. IR (KBr) :
υ
CO = 1648 cm-1. 1H NMR (CDCl3, 400 MHz) δ 2.36 (m, 2 H), 2.72 (t, 2 H, J = 8.0 Hz), 3.04 (t, 2 H, J =
7.4 Hz), 5.84 (s, 2 H), 7.09 (d, 2 H, J = 4.0 Hz), 7.38 (m, 3 H), 7.78 (d, 1 H, J = 4.0 Hz), 7.87 (d, 1 H, J=
8.0 Hz), 8.42 (d, 1 H, J= 8.0 Hz), 8.68 (d, 1 H, J = 8.0 Hz), 9.33 (s, 1 H). 13C NMR (CDCl3, 25 MHz) δ
22.4, 23.3, 38.1, 49.7, 113.3, 114.0, 122.4, 122.6, 123.3, 124.5, 125.4, 125.8, 128.2, 129.5, 135.3, 143.1,
151.9, 152.8, 194.6. Anal. Calcd for C22H18N2O : C 80.96, H 5.56, N 8.58; Found : C 80.92, H 5.71, N
8.63.
13
8-Benzylaminoquinoline (23) : A solution of enaminone (18) (101 mg, 0.3 mmol) in 220 mL of
methanol was irradiated under nitrogen for 2 h in the range 275-350 nm in a quartz reactor. After
evaporation of the solvent, the resulting precipitate was chromatographed on neutral alumina eluted with
dichloromethane to give 15 mg (21%) of 23 as a viscous oil.
8-amino-7-benzylquinoline (27): A solution of enaminone (18) (200 mg, 0.6 mmol) in 300 mL of
methanol was irradiated under nitrogen for 0.5 h with a medium mercury pressure in a quartz reactor
(emission at 254 nm). After evaporation of the solvent, the resulting mixture was chromatographed on
silica gel eluted with dichloromethane, to give 35 mg (25%) of 27 as a brown oil. MS; m/z (relative
intensity) 234 (100), 157 (40); 1H NMR (CDCl3, 100 MHz) δ 4.10 (s, 2 H), 4.50 (br s, 1 H), 7.19-7.39 (m,
8 H), 8.06, (dd, 1 H, J = 8.3 and 1.8 Hz), 8.74 (dd, 1 H, J = 4.3 and 1.8 Hz). 13C NMR (CDCl3, 25 MHz)

δ (CH and CH2) 38.2, 115.8, 120.8, 126.4, 128.6 (2 carbons), 128.7 (2 carbons), 130.1, 136.0, 147.5.
Anal. Calcd for C16H14N2 : C 82.02, H 6.02, N 11.96. Found : C 81.95, H 6.03, N 12.02. Further elution
gave 8 (8%).
5-Amino-6-benzylquinoline (29): This compound was obtained from 2818 in 6% yield using the same
method employed for the synthesis of 27; brown paste; MS; m/z (relative intensity) 234 (100), 157 (46);
1H NMR (CDCl3, 100 MHz) δ 4.10 (s, 1 H), 7.24-7.60 (m, 10 H), 8.17 (d, 1 H, J = 7.9 Hz), 8.85 (d, 1 H,
J = 2.9 Hz). Anal. Calcd for C16H14N2 : C 82.02, H 6.02, N 11.96. Found : C 82.13, H 5.95, N 11.92.
Further elution gave 6 (26%).
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