Reactions of 3-Benzylindole-2-carbohydrazides: Synthesis of New 10-Benzyl-1,2-dihydro-1-oxo-1,2,4-triazino[4,5-a]indoles and 3-Benzyl-2-(1,3,4-oxadiazol-2-yl)indoles

Article abstract of DOI:10.1002/jhet.5570410102

3-Benzylindole-2-carbohydrazides (4) on reaction with triethylorthoformate in a polar solvent like DMF yielded only 10-benzyl-1,2-dihydro-1-oxo-1,2,4 -triazino[4,5-a]indoles (5) while (4) on reaction with triethylorthoacetate in DMF yielded both 10-benzyl-4-methyl-1,2-dihydro-1-oxo-1,2,4-triazino[4,5-a]indoles (5) and 3-benzyl-2-(5-methyl-1,3,4-oxadiazol-2-yl)indoles (6) instead of only the triazinoindoles as expected. The oxadiazolylindoles (6) were also synthesized by refluxing (4) with excess of orthoesters. The structures of the compounds formed were characterized by their analytical and spectral data.

Full text of DOI:10.1002/jhet.5570410102

Jan-Feb 2004
7
Reactions of 3-Benzylindole-2-carbohydrazides: Synthesis of New
10-Benzyl-1,2-dihydro-1-oxo-1,2,4-triazino[4,5-a]indoles and
3-Benzyl-2-(1,3,4-oxadiazol-2-yl)indoles
Shambabu Joseph Maddirala§, Vidya S. Gokak¶ & Linganagouda D. Basanagoudar*
P. G. Department of Studies in Chemistry, Karnatak University, Dharwad- 580 003, India
Received May 7, 2003
3-Benzylindole-2-carbohydrazides (4) on reaction with triethylorthoformate in a polar solvent like DMF
yielded only 10-benzyl-1,2-dihydro-1-oxo-1,2,4-triazino[4,5-a]indoles (5) while (4) on reaction with tri-
ethylorthoacetate in DMF yielded both 10-benzyl-4-methyl-1,2-dihydro-1-oxo-1,2,4-triazino[4,5-a]indoles
(5) and 3-benzyl-2-(5-methyl-1,3,4-oxadiazol-2-yl)indoles (6) instead of only the triazinoindoles as
expected. The oxadiazolylindoles (6) were also synthesized by refluxing (4) with excess of orthoesters. The
structures of the compounds formed were characterized by their analytical and spectral data.
J. Heterocyclic Chem., 41, 7 (2004).
The reactions of both aromatic and heteroaromatic acid
DMF gave exclusively 10-benzyl-1,2-dihydro-1-oxo-
1,2,4-triazino[4,5-a]indoles (5 a - d), while with excess of
triethylorthoformate only, the corresponding oxadia-
zolylindoles (6a-d) were obtained as anticipated (Scheme
2). However, hydrazides (4) when refluxed with triethy-
lorthoacetate in DMF yielded corresponding triazinoin-
doles (5e-h) along with compounds which were character-
ized, by their analytical and spectral data, to be corre-
sponding 3-benzyl-2-(5-methyl-1,3,4-oxadiazol-2-
yl)indoles (6e'-h'). The structures of compounds (6e'-h')
were further confirmed by their independent syntheses, by
refluxing appropriate hydrazides with excess of triethyl-
orthoacetate only (Scheme 2). The m.p., infrared (KBr)
and NMR spectra of (6e'-h') were identical to those of
(6e-h) respectively; no depression in their mixed melting
points was observed.
It appears, therefore, that the reactions of 5-substituted-3-
benzylindole-2-carbohydrazides with orthoesters provide
an interesting example of competitive cyclisation to five
and six-membered ring products. A pathway consistent
with these results may be given as follows. Although the
hydrazides normally yield the oxotriazines (5) directly on
reaction with orthoesters, in a polar solvent like dimethyl-
formamide, it appears that the stepwise mechanism for the
cyclisation involves initial condensation with the more
nucleophilic hydrazide nitrogen with subsequent ring clo-
sure by the indole nitrogen. Initial condensation would be
expected to occur at the more nucleophilic site, the terminal
hydrazide nitrogen, producing the non-isolable intermedi-
ate (7). Intermediates of this type have been postulated and
in few cases isolated during the reactions of heterocyclic
carbohydrazides with orthoesters [9,10].
hydrazides with orthoesters have been of both synthetic and
mechanistic interest. The reactions of indole-2-carbohy-
drazides with orthoesters have been widely studied.
Ainsworth [1,2] reported that a neat reaction leading to the
formation of exclusively oxadiazoles occurs on boiling
indole-2-carbohydrazides with orthoesters. However,
refluxing of indole-2-carbohydrazide with orthoester in
presence of a polar solvent, like DMF, results in the forma-
tion of 1,2-dihydro-1-oxo-1,2,4-triazino[4,5-a]indoles [3].
Robba and co-workers [4,5,6] have reported the synthesis
of 1,2-dihydro-1-oxo-1,2,4-triazino[4,5-a]indoles as a base
induced ring expansion rearrangement of oxadiazolylin-
doles. 3-Substituted indole-2-carbohydrazides (1) with
appropriate orthoester in boiling DMF yielded triazines (2)
as the only products of the reaction; with a view to study the
role of stereoelectronic factors in the reaction of (1) with
orthoesters, different substituents at C-3 and a variety of
groups of different electronic nature at C-5 position in the
indole nucleus were incorporated [7] (Scheme 1).
Scheme 1
Loss of a molecule of ethanol, directly from the interme-
diate (7), would yield 3-benzyl-1,2-dihydro-1-oxo-1,2,4-
triazinoindoles (5), while its iminol tautomer (8) would
give 3-benzyl-2-(1,3,4-oxadiazol-2-yl)indoles (6)
(Scheme 3). Direct evidence for the possible intermediate
(7) was sought but not obtained in the present study. The
failure to detect the intermediate suggests the rapid nucle-
In continuation of our interest in the synthesis of tri-
azino[4,5-a]indoles, herein we report the results of the
reactions of various 5-substituted 3-benzylindole-2-carbo-
hydrazides (4) with orthoesters. Reaction of ethyl 3-ben-
zylindole-2-carboxylates (3) [8] with hydrazine hydrate
gave 3-benzylindole-2-carbohydrazides (4) in good yields.
Refluxing compounds (4) with triethylorthoformate in

8
S. J. Maddirala, V. S. Gokak & L. D. Basanagoudar
Vol. 41
Scheme 2
Scheme 3
Formation of both the triazinoindoles and oxadiazolylin-
doles together in the same reaction suggests that both the
compounds are sufficiently stable under the reaction con-
ditions. Further, the formation of both the products in the
case of benzyl substituent and not with methyl or phenyl
substituent at 3-position of indole [7] suggests that steric
factors also and not the electronic factors alone control the
course of reaction. It may, therefore, be concluded that
both the steric implications of the orthoester substituent
and substituent at 3-position of indole-2-carbohydrazides
appear to influence the mode of cyclisation and the type of
products obtained from these cyclisation reactions.
EXPERIMENTAL
All melting points are uncorrected. Infrared spectra were
recorded on a Nicolet Impact-410 FT-IR spectrophotometer
-1
1
using KBr pellets; the frequencies are expressed in cm . The H
NMR spectra were recorded on Bruker Avance –200 MHz FT-
NMR, and Bruker AMX-400 400 MHz instruments with
tetramethylsilane as the internal reference; the chemical shifts are
reported in ppm and coupling constants (J) are given in Hertz
(Hz). Elemental analyses were performed using Heraus CHN
rapid analyzer.
3-Benzylindole-2-carbohydrazides (4a-d).
General Procedure.
A solution of appropriate ethyl 3-benzylindole-2-carboxylate
(3 a - d) (0.05 mole) in pyridine (25 ml) and 30 g of hydrazine
hydrate (99%) was heated under reflux for 2 hours and cooled.
The crystalline solid that separated was collected by filtration
and recrystallised from dioxane to give the corresponding 3-ben-
zylindole-2-carbohydrazides. The physical data and spectral
ophilic involvement of either the indole nitrogen or iminol
oxygen with consequent formation of products.

Jan-Feb 2004
Reactions of 3-Benzylindole-2-carbohydrazides
9
Table 1
Physical and Analytical Data of 3-Benzylindole-2-carbohydrazides
Compound
R
Yield
(%)
Mp
(°C)
Molecular
Formula
Analyses %
Calcd./Found
H
C
N
4a
4b
4c
4d
H
CH
OCH
Cl
78
75
74
72
217-218
205-206
208-209
208-209
C
C
H
N O
72.43/72.51
73.10/73.19
69.14/69.25
64.11/64.22
5.70/5.79
6.13/6.21
5.80/5.92
4.71/4.82
15.84/15.92
15.04/15.27
14.23/14.31
14.02/14.14
16 15
3
H N O
17 17 3
3
C H N O
17 17 3 2
3
C
H
16 14
ClN O
3
Table 2
Physical and Analytical Data of 10-Benzyl-1,2-dihydro-1-oxo-1,2,4-triazino[4,5-a]indoles
1
Compound
R
H
CH
OCH
Cl
H
CH
OCH
Cl
R
Yield
(%)
Mp
(°C)
Molecular
Formula
Analyses %
Calcd./Found
H
C
N
5a
5b
5c
5d
5e
5f
H
H
H
62
68
58
53
42
50
60
50
265-266
272-273
235-236
268-269
275-276
290-291
260-261
299-300
C
C
H
N O
74.17/74.25
74.72/74.81
70.81/70.92
65.92/65.99
74.72/74.91
75.23/75.29
71.46/71.52
66.77/66.82
4.76/4.82
5.23/5.32
4.95/5.07
3.90/4.12
5.23/5.00
5.65/5.72
5.37/5.49
4.36/4.49
15.26/15.34
14.52/14.64
13.76/13.82
13.57/13.68
14.52/14.61
13.85/13.99
13.16/13.21
12.98/13.09
17 13
3
H
N O
3
18 15
3
C H N O
18 15 3 2
C H ClN O
3
H
17 12 3
CH
CH
CH
CH
C H N O
18 15 3
3
3
3
3
C H N O
19 17 3
C H N O
3
5g
5h
3
19 17 3 2
C
H ClN O
18 14 3
Table 3
Physical and Analytical Data of 3-Benzyl-2-(1,3,4-oxadiazol-2-yl)indoles
1
Compound
R
R
Yield
(%)
Mp
(°C)
Molecular
Formula
Analyses %
Calcd./Found
H
C
N
6a
6b
6c
6d
6e'
6e
6f'
6f
6g'
6g
6h'
6h
H
CH
OCH
Cl
H
H
CH
CH
OCH
OCH
Cl
H
H
H
55
58
58
58
33
64
37
55
28
56
32
56
225-226
235-236
230-231
248-249
217-218
218-219
235-236
237-238
234-235
234-235
267-268
267-268
C
C
H
N O
74.17/74.05
74.72/74.61
70.81/70.70
4.76/4.86
5.23/5.32
4.95/5.05
3.90/3.98
5.23/5.34
5.23/5.20
5.65/5.72
5.65/5.60
5.37/5.48
5.37/5.30
4.36/4.42
4.36/4.31
15.26/15.34
14.52/14.61
13.76/13.84
13.57/13.68
14.52/14.67
14.52/14.49
13.85/13.92
13.85/13.80
13.16/13.24
13.16/13.08
12.98/13.08
12.98/12.90
17 13
3
H
N O
3
18 15
3
C H N O
18 15 3 2
3
H
C H ClN O 65.92/66.10
17 12 3
CH
CH
CH
CH
CH
CH
CH
CH
C
H N O
H N O
74.72/74.82
74.72/74.68
75.23/75.33
75.23/75.19
71.46/71.52
71.46/71.40
3
3
3
3
3
3
3
3
18 15 3
C
C
C
18 15 3
H N O
19 17 3
3
H
N O
3
3
19 17
C
H N O
H
H ClN O 66.77/66.83
3
3
19 17 3
2
2
C
N O
3
19 17
C
18 14 3
Cl
C H ClN O 66.77/66.70
18 14 3
analyses of these substituted 3-benzylindole-2-carbohydrazides
are recorded in Table 1 and Table 4.
General Procedure.
A mixture of the appropriate 3-benzylindole-2-carbohydrazide
(4 a - d) (0.01 mole) and triethylorthoformate (50 ml) was heated
under reflux for 12 hours. Excess of the reagent was removed under
reduced pressure. The residue was treated with pet. ether and crys-
tallized from ethanol to obtain the 5-substituted 3-benzyl(1,3,4-oxa-
diazol-2-yl)indoles. The physical data and spectral analyses of these
oxadiazolylindoles are recorded in Table 3 and Table 4.
General Procedure for the Reaction of 3-Benzylindole-2-carbo-
hydrazides (4) with Triethylorthoformate.
A mixture of appropriate 3-benzylindole-2-carbohydrazide (4a-
d) (0.011 mole) and triethylorthoformate (2.07 g, 0.014 mole) in
dimethylformamide (20 ml) was refluxed for 12 hours while pro-
tecting it from moisture. The reaction mixture was poured onto
crushed ice. The white solid that separated was collected by filtra-
tion and crystallized from dioxane ethanol mixture to obtain the
various 8-substituted 10-benzyl-1,2-dihydro-1-oxo-1,2,4-tri-
azino[4, 5-a]i ndoles (5 a - d). The physical data and spectral analy-
ses of these triazinoindoles are recorded in Table 2 and Table 4.
General Procedure for the Reaction of 3-Benzylindole-2-carbo-
hydrazides (4) with Triethylorthoacetate.
A mixture of the appropriate 3-benzylindole-2-carbohydrazide
(4a-d) (0.011 mole) and triethylorthoacetate (2.27 g, 0.014 mole)
in dimethylformamide (20 ml) was refluxed for 12 hours while
protecting it from moisture. The reaction mixture was left
3-Benzyl-2-(1,3,4-oxadiazol-2-yl)indoles (6a-d).

10
S. J. Maddirala, V. S. Gokak & L. D. Basanagoudar
Vol. 41
Table 4
1
IR and H-NMR Spectral Analyses for Compounds 4a-d, 5a-h, 6a-d and 6e'-h'
-1
1
Compound IR (KBr) (ν/cm )
H NMR (Solvent/ δ values in ppm)
4a
4b
4c
4d
5a
5b
1616 (C=O),
3350-3260 (br)
(DMSO-d ): 4.43 (s, 2H, CH Ph), 4.53 (s, 2H, -NH ), 6.96-7.00 (m, 1H, 5-H), 7.07-7.11 (m, 1H, 6-H), 7.16-7.21
6 2 2
(m, 3H, phenyl protons), 7.27-7.29 (m, 2H, phenyl protons), 7.37 (d, J = 8.2 Hz, 1H, 4-H), 7.53 (d, J = 7.98Hz,
1H, 7-H), 9.28 (s, 1H, indole NH), 11.15 (s, 1H, -CONH).
(DMSO-d ): 2.32 (s, 3H, CH ), 4.41 (s, 2H, CH Ph), 4.53 (s, 2H, -NH ), 7.01 (d, J = 8.36 Hz, 1H, 6-H), 7.10 (t, J =
6 3 2 2
7.16 Hz, 1H, 4'-H), 7.20 (t, J = 7.16 Hz, 2H, 3' and 5'-H), 7.28 (d, J = 8.39 Hz, 3H, 2', 6' and 7-H), 7.31 (s, 1H, 4-H),
9.25 (s, 1H, indole NH), 11.04 (s, 1H, -CONH).
(DMSO-d ): 3.69 (s, 3H, OCH ), 4.39 (s, 2H, CH Ph), 4.48 (s, 2H, -NH ), 6.83 (dd, J = 8.61 Hz, 2.35 Hz, 1H, 6-H),
6 3 2 2
6.95 (d, J = 2.35 Hz, 1H, 4-H), 7.09 (t, J = 7.04 Hz, 1H, 4'-H), 7.19 (t, J = 7.04 Hz, 2H, 3'-H and 5'-H), 7.26-7.29 (m,
3H, 2'-H, 6'-H and 7-H), 9.18 (s, 1H, indole NH), 10.98 (s, 1H, -CONH).
(DMSO-d ): 4.38 (s, 2H, CH Ph), 4.54 (s, 2H, -NH ), 7.11 (t, J = 7.04 Hz, 1H, 4'-H), 7.16 (dd, J = 1.95 Hz, 8.61Hz,
6 2 2
1H, 6-H), 7.20 (t, J = 7.43 Hz, 2H, 3'-H and 5'-H), 7.26 (d, J = 7.42 Hz, 2H, 2'-H and 6'-H), 7.39 (d, J = 8.61 Hz,
1H, 7-H), 7.52 (d, J = 1.57 Hz, 4-H), 9.35 (s, 1H, indole NH), 11.37 (s, 1H, -CONH).
NHNH
2
1616 (C=O),
3320-3270 (br)
NHNH
2
1635 (C=O),
3438-3259 (br)
NHNH
2
1612 (C=O),
3350-3256 (br)
NHNH
2
1659 (C=O),
3184 (NH)
(DMSO-d ): 4.59 (s, 2H, CH Ph), 7.14 (t, J = 7.32 Hz, 1H, 4'-H), 7.24 (t, J = 7.33 Hz, 2H, 3'- and 5'-H), 7.34-7.39 (m,
6 2
3H, 8-, 2'- and 6'-H), 7.51 (ddd, J = 8.1 Hz and J = 0.9 Hz, 1H, 7-H), 7.82 (d, J = 8.08 Hz, 1H, 9-H), 8.18 (d,
J = 8.42 Hz, 1H, 6-H), 9.05 (s, 1H, -CH=N-), 11.80 (s, 1H, -NH).
1652 (C=O),
3173 (NH)
(DMSO-d ): 2.08 (s, 3H, CH ), 4.56 (s, 2H, CH Ph), 7.12 (t, J = 7.3 Hz, 1H, 4'-H), 7.23 (t, J = 7.3 Hz, 2H, 3'- and
6 3 2
5'-H), 7.31-7.36 (m, 3H, 7-, 2'- and 6'-H), 7.58 (s, 1H, 9-H), 8.05 (d, J = 8.5 Hz, 1H, 6-H), 8.95 (s, 1H, -CH=N-),
11.74 (s, 1H, -NH).
(DMSO-d ): 3.78 (s, 3H, OCH ), 4.57 (s, 2H, CH Ph), 7.11-7.39 (m, 7H, 7-H, 9-H, and phenyl protons), 8.08
5c
1658 (C=O),
3170 (NH)
1659 (C=O),
3194 (NH)
6
3
2
(d, J = 9.05 Hz, 1H, 6-H), 8.97 (s, 1H, -CH=N-), 11.75 (s, 1H, -NH).
(DMSO-d ): 4.58 (s, 2H, CH Ph), 7.14 (t, J = 6.9 Hz, 1H, 4'-H), 7.24 (t, J = 7.1 Hz, 2H, 3'- and 5'-H), 7.37 (d, J =
5d
6
2
7.8 Hz, 2H, 2'- and 6'- H), 7.53 (dd, J = 8.9 Hz, J = 1.3Hz, 1H, 7-H), 7.87 (d, J = 1.5 Hz, 1H, 9-H), 8.21 (d, J = 8.90 Hz,
1H, 6-H), 9.04 (s, 1H, -CH=N-), 11.88 (s, 1H, -NH).
5e
1659 (C=O),
3172 (NH)
(DMSO-d ): 2.84 (s, 3H, CH ), 4.67 (s, 2H, CH Ph), 7.13 (t, J = 7.3 Hz, 1H, 4'-H), 7.23 (t, J = 7.3 Hz, 2H, 3'-H and
6 3 2
5'-H), 7.36 (d, J = 7.1 Hz, 2H, 2'-H and 6'-H), 7.38 (t, J = 7.8 Hz, 1H, 8-H), 7.47 (ddd, J = 8.5 Hz, 7.1 Hz and 1.2 Hz,
1H, 7-H), 7.85 (d, J = 7.91 Hz, 1H, 9-H), 8.11 (d, J = 8.66 Hz, 1H, 6-H), 11.70 (s, 1H, NH).
(DMSO-d ): 2.41 (s, 3H, CH Ph), 2.78 (s, 3H, CH ), 4.61 (s, 2H, CH Ph), 7.07-7.35 (m, 6H, 7-H and phenyl protons),
5f
1647 (C=O),
3178 (NH)
1652 (C=O),
3166 (NH)
1648 (C=O),
3180 (NH)
6
3
3
2
7.59 (s, 1H, 9-H), 7.96 (d, J = 8.82 Hz, 1H, 6-H), 11.63 (s, 1H, NH).
(DMSO-d ): 2.79 (s, 3H, CH ), 3.35 (s, 3H, OCH ), 4.63 (s, 2H, CH Ph), 7.09-7.38 (m, 7H, 9-H and Phenyl protons),
5g
5h
6
3
3
2
7.99 (d, J = 9.31 Hz, 1H, 6-H), 11.67 (s, 1H, NH).
(DMSO-d ): 2.82 (s, 3H, CH ), 4.64 (s, 2H, CH Ph), 7.13 (t, J = 7.2 Hz, 1H, 4'-H), 7.23 (t, J = 7.4 Hz, 2H, 3'-H and
6
3
2
5'-H), 7.35 (d, J = 7.5 Hz, 2H, 2'-H and 6'-H), 7.48 (dd, J = 9.0 Hz and J = 1.3 Hz, 1H, 7-H), 7.89 (d, J = 1.3 Hz,
1H, 9-H), 8.12 (d, J = 9.17 Hz, 1H, 6-H), 11.80(s, 1H, NH).
6a
3231 (NH),
1623 (C=N)
(DMSO-d ): 4.52 (s, 2H, CH Ph), 7.06 (t, J = 7.16 Hz, 1H, 5-H), 7.14 (t, J = 7.07 Hz, 1H 6-H), 7.21-7.43 (m, 5H,
6 2
phenyl protons), 7.48 (d, J = 8.2 Hz, 1H, 4-H), 7.62 (d, J = 8.0 Hz, 1H, 7-H), 9.41(s, 1H, 5-H of oxadiazole),
12.05 (s, 1H, -NH).
6b
6c
3245 (NH),
1606 (C=N)
3229 (NH),
1609 (C=N)
(CDCl ): 2.41 (s, 3H, CH ), 4.51( s, 2H, CH Ph), 7.14-7.39 (m, 8H, Phenyl protons), 8.43( s, 1H, 5-H of oxadiazole),
3 3 2
9.22 (brs, 1H, indole NH).
(CDCl ): 3.78(s, 3H, OCH ), 4.51 (s, 2H, -CH Ph), 6.93 (d, J = 2.35 Hz, 1H, 4-H), 7.00 (dd, J = 9 Hz, J = 2.35 Hz, 1H,
3
3
2
6-H), 7.17-7.26 (m, 5H, phenyl protons), 7.36 (d, J = 9 Hz, 1H, 7-H), 8.43 (s, 1H, 5-H of oxadiazole), 8.96 (brs,
1H, -NH).
6d
3201 (NH),
1606 (C=N)
3221 (NH),
1625 (C=N)
3222 (NH),
1616 (C=N)
3216 (NH),
1616 (C=N)
3172 (NH),
1625 (C=N)
(CDCl ): 4.50 (s, 2H, -CH Ph), 7.18-7.29 (m, 6H, 6-H and phenyl protons), 7.44 (d, J = 8.61 Hz, 1H, 7-H), 7.54 (s,
3 2
1H, 4-H), 8.48 (s, 1H, 5-H of oxadiazole), 9.41 (brs, 1H, -NH).
(CDCl ): 2.61(s, 3H, CH ), 4.51(s, 2H, CH Ph), 7.09-7.33 (m, 7H, phenyl protons), 7.46 (d, J = 8.22 Hz, 1H, 4-H),
6e'
6f'
6g'
6h'
3
3
2
7.56 (d, J = 7.83 Hz, 1H, 7-H), 9.19 (brs, 1H, -NH).
(CDCl ): 2.41(s, 3H, CH Ph), 2.59 (s, 3H, CH ), 4.48 (s, 2H, -CH Ph), 7.12-7.34 (m, 8H, phenyl protons),
3
3
3
2
8.97 (brs, H, -NH).
(CDCl ): 2.60 (s, 3H, CH ), 3.77 (s, 3H, OCH ), 4.48 (s, 2H, -CH Ph), 6.91(d, J = 2.35 Hz, 1H, 4-H), 6.97 (dd,
3
3
3
2
J = 8.61 Hz, J = 2.35 Hz, 1H, 6-H), 7.14-7.26 (m, 5H, phenyl protons), 7.38 (d, J = 9Hz, 1H, 7-H), 9.19 (brs, 1H, -NH).
(CDCl ): 2.63 (s, 3H, CH ), 4.46 (s, 2H, CH Ph), 7.24-7.28 (m, 6H, 6-H and phenyl protons), 7.45 (d, J = 8.8 Hz,
3
3
2
1H, 7- H), 7.52 (d, J = 2 Hz, 1H, 4- H), 9.60 (brs, 1H, NH).
overnight and then poured onto crushed ice. The white solid that
separated was collected by filtration and crystallized from diox-
ane to obtain the 8-substituted 10-benzyl-4-methyl-1,2-dihydro-
1-oxo-1,2,4-triazino[4,5-a]indoles (5e-h).
zolylindoles are recorded in Table 2, Table 3 and Table 4.
3-Benzyl-2-(5-methyl-1,3,4-oxadiazol-2-yl)indoles (6e-h).
General Procedure.
The mother liquors, from which triazinoindoles (5 e - h) were
isolated, on concentration yielded solid products which were
recrystallised from ethanol to get various 5-substituted 3-benzyl-
2-(5-methyl-1,3,4-oxadiazol-2-yl)indoles (6 e ' - h '). The physical
data and spectral analyses of these triazinoindoles and oxadia-
Appropriate 3-benzylindole-2-carbohydrazide (4a-d) (0.01
mole) and triethylorthoacetate (50 ml) were heated under
reflux for 12 hours. Excess of the reagent was removed under
reduced pressure. The residue was treated with pet. ether and
crystallized from ethanol to get 5-substituted 3-benzyl-2-(5-

Jan-Feb 2004
Reactions of 3-Benzylindole-2-carbohydrazides
11
J. Heterocyclic Chem., 17, 77 (1980).
[4] M. Robba, D. Maume and J. C. Lancelot, J. Heterocyclic
Chem., 14, 1365 (1977).
methyl-1,3,4-oxadiazol-2-yl)indoles. The physical data and
spectral analyses of these oxadiazolylindoles are recorded in
Table 3 and Table 4.
[5] M. Robba, D. Maume and J. C. Lancelot, J. Heterocyclic
Chem., 15, 1209 (1978).
[6] D. Maume, J. C. Lancelot and M. Robba, J. Heterocyclic
Chem., 16, 1217 (1979).
REFERENCES AND NOTES
§
Present address: Ciba India Private Limited, Off Aarey
[7] S. B. Rajur, A.Y. Merwade, L.D. Basanagoudar and P.V.
Kulkarni, J. Pharm. Sci., 78, 780 (1989).
[8] S. J. Maddirala and L. D. Basanagoudar, Synth. Commun.,
33, 851 (2003).
Road, Goregaon (East), Mumbai-400063, India
¶
Present address: Pearl Organics Limited, Patalganga
Industrial Area, Mumbai-410207, India.
[1] C. Ainsworth, U. S. Patent, 2,733, 245 (1956); Chem.
Abstr., 50, 12115 (1956).
[9] A. Shafiee, E. Naimi, P. Mansobi, A. Foroumadi and M.
Shekari, J. Heterocyclic Chem., 32, 1235 (1995).
[10] P. Cauliez, B. Rigo, D. Fasseur and D. Couturier, J.
Heterocyclic Chem., 33, 1073 (1996).
[2] C. Ainsworth, J. Am. Chem. Soc., 77, 1148 (1955).
[3] A. Monge, I. Aldana, M. M. Rabbani and E. A. Fernandez,