Derivatives of indole. 143. Synthesis of photochromic derivatives of 2-arylindoles

Article abstract of DOI:10.1007/s10593-005-0053-3

New derivatives of 2-arylindoles containing (4-pyridyl)alkyl substituents at various positions of the pyrrole ring were synthesized. They react with 2,3 dimethoxycarbonylspirofluorenylcyclopropene with the formation of light-sensitive systems belonging to the photochromic dihydroindolizine class.

Full text of DOI:10.1007/s10593-005-0053-3

Chemistry of Heterocyclic Compounds, Vol. 40, No. 11, 2004
HETEROCYCLIC SYNTHESIS USING
NITRILE IMINES. 4*. SYNTHESIS OF 3-SUBSTITUTED
1-ARYL-1,2,4-TRIAZASPIROALK-2-ENES
H. M. Dalloul
Cycloalkanone oximes react with C-(2-furoyl)-, C-(2-thenoyl)- and C-(phenylaminocarbonyl)nitrile
imines to give unexpected 3-substituted 1-aryl-1,2,4-triazaspiroalk-2-enes rather than the cycloaddition
or the cyclocondensation products.
Keywords: cycloalkanone oxime, nitrile imines, 1,2,4-triazaspiro[4,5]dec-2-ene, cycloaddition.
1,3-Dipolar cycloaddition reactions of nitrile imines with dipolarophiles containing C=N bond represent
an important synthetic route to substituted 1,2,4-triazoles [2].
The reaction of nitrile imines with methyl hydrazones of aliphatic ketones is reported to give the
cyclocondensation products, viz 1,2,4,5-tetrazines rather than the cycloaddition products at C=N, 1,2,4-triazoles
apparently, because of the strong nucleophilicity of the nitrogen atom carrying the methyl group, where the
reaction starts [1, 3, 4]. Simple hydrazones react in a similar manner giving initially the acyclic electrophilic
addition products, which cyclize to 1,2,4,5-tetrazines upon heating with charcoal [5-7]. Recently, Ferwanah and
co-workers [8-10] described a versatile and efficient one-pot synthesis of 5,5-di- substituted 3-acetyl-1-aryl-1H-
1,2,4-triazoles utilizing available ketoximes and hydrazonoyl halides (precursors of nitrile imines, the reactive
1,3-dipolar species). In this work, the reaction of nitrile imines 1a-d with cycloalkanone oximes 2-7 is
investigated.
Initially, it was thought that the reaction will produce cycloaddition products 1,2,4-triazoles 8 or
cyclocondensation products 1,2,4,5-oxatriazines 9, but the spectral data of the resulting products indicated
unexpected 3-substituted 1-aryl-1,2,4-triazaspiroalk-2-enes 10-15 (Scheme). The formation of compounds 10-15
is assumed to involve cycloaddition adducts 8 which tautomerize to amine oxide-type intermediates that are
deoxygenated by triethylamine [10].
The structures of products 10-15 were elucidated on the basis of analytical and spectral data. The
electron impact (EI) mass spectra (Table) display the correct molecular ions in accordance with the suggested
structures. The base peak in all these compounds is that of the conjugated vinyltriazole cation. This occurs at
·
·
M+· - 29, C2H5 for compounds containing cyclopentane moiety, M+· - 43, C3H7 for compounds containing
cyclohexane moiety, M+· - 57, C4H9 for compounds containing cycloheptane and methyl cyclohexane moiety,
·
·
·
M+· - 71, C5H11 for compounds containing cyclooctane moiety, and M+· - 99, C7H15 for compounds containing
_______
* For Part 3 see Ref. 1.
__________________________________________________________________________________________
Department of Chemistry, Faculty of Applied Sciences, Al-Aqsa University of Gaza, P. O. Box 4051,
Gaza Strip via Israel; e-mail: dalloul15@hotmail.com, dalloul-15@mail.com. Published in Khimiya
Geterotsiklicheskikh Soedinenii, No. 11, pp. 1626-1631, November, 2004. Original article submitted
September 14, 2003.
1402
0009-3122/04/4011-1402©2004 Springer Science+Business Media, Inc.

tert-butyl cyclohexane moiety. This fragmentation pattern is well known for cycloalkanones [11]. The 1H NMR
spectra of products 10-15 show a signal at 5.5 ppm, which is characteristic for the N-H of the five-membered
ring, and in compounds containing PhNHCO group another signal of N-H appears at 9.5 ppm (Experimental).
'
Ar
Cl(Br)
N
N
A
'
C
N
Ar
NHAr
Ar
N
16a–d
OH
NEt3 / 0 oC
8
'
Ar
N
N
_
THF/ r. t.
+
A
'
Ar
C
N
HO
N
A
NHAr
+
Ar
N
H
1a–d
2–7
'
10a–d – 15a–d
Ar
N
N
N
Ar
A
O
H
9
a, b, d X = Cl, c X = H; 2, 10 A = (CH2)2, 3, 11 A = (CH2)3,
;
X
Ar' =
4, 12 A = CH2CHMeCH2, 5, 13 A = CH2CH(t-Bu)CH2, 6, 14 A = (CH2)4, 7, 15 A = (CH2)5;
CO , c, d Ar =
CO
, b Ar =
NHCO
1, 10–16
Ar =
a
S
O
The 13C NMR spectra account for the different carbons of these triazoles. The signal at 85-95 ppm,
which is attributed to C(5) (spiro carbon) of the triazole ring is of special significance. This is similar to reported
values of spiro carbons flanked by two nitrogens in five-membered heterocycles [9, 10, 12].
EXPERIMENTAL
Melting points were determined on Electrothermal Melting Temperature Apparatus and are uncorrected.
1
IR spectra were obtained by using Satellite 3000 Mid infrared spectrometer (KBr discs). H and 13C NMR
1
13
spectra were recorded on a Bruker instrument (400 MHz for H and 100 MHz for C) in CDCl3 using TMS as
an internal reference. Chemical shifts (δ) are expressed in ppm downfield from internal TMS. Electron impact
mass spectra were run on LCT Electrospray mass spectrometer. Elemental analysis was performed at Cairo
University, Egypt. Hydrazonoyl halides (16a) [13], (16b) [14], and (16c,d) [15], cycloalkanone oximes (2-7)
[16, 17] were prepared according to known literature procedures.
1403

TABLE 1. Physical Properties and Elemental Analyses of Compounds 10-15
Found, %
Calculated, %
H
Empirical
formula,
M+·
——————
Com-
pound
mp, °C
Yield, %
C
N
10b
10d
11a
11b
11c
11d
12a
12b
12c
12d
13a
13b
13d
14a
14b
14c
15b
15d
C17H16ClN3OS
345/347
58.80
59.04
4.50
4.66
12.10
12.15
109-111
123-125
131-133
140-142
148-150
158-160
123-125
117-119
149-151
160-162
134-136
146-148
163-165
129-131
138-140
152-154
126-128
160-162
55
50
60
61
59
60
52
54
59
62
58
60
61
58
60
57
55
48
C19H19ClN4O
354/356
64.50
64.31
5.60
5.40
15.60
15.79
C18H18ClN3O2
343/345
63.10
62.88
5.40
5.28
12.30
12.22
C18H18ClN3OS
359/361
59.90
60.06
5.10
5.04
11.70
11.68
C20H22N4O
334
71.60
71.83
6.50
6.63
16.80
16.75
C20H21ClN4O
368/370
64.90
65.12
5.60
5.74
15.30
15.19
C19H20ClN3O2
357/359
63.90
63.77
5.70
5.63
11.60
11.74
C19H20ClN3OS
373/375
60.80
61.03
5.30
5.39
11.10
11.24
C21H24N4O
348
72.50
72.39
7.10
6.94
15.90
16.08
C21H23ClN4O
382/384
66.10
65.88
5.90
6.05
14.50
14.63
C22H26ClN3O2
399/401
66.20
66.07
6.70
6.55
10.60
10.51
C22H26ClN3OS
415/417
C24H29ClN4O
424/426
63.70
63.52
6.40
6.30
9.90
10.10
67.60
67.83
6.80
6.88
13.20
13.18
C19H20ClN3O2
357/359
63.90
63.77
5.70
5.63
11.60
11.74
C19H20ClN3OS
373/375
60.90
61.03
5.40
5.39
11.30
11.24
C22H28N4O
364
72.30
72.50
7.80
7.74
15.20
15.37
C20H22ClN3OS
387/389
62.10
61.92
5.90
5.72
10.70
10.83
C22H25ClN4O
396/398
66.70
66.57
6.50
6.35
14.00
14.12
Synthesis of Substituted Heterocyclic Spiro Compounds 10-15 (General procedure). Triethylamine
(0.05 mol) in absolute THF (10 ml) was added dropwise to a stirred solution of hydrazonoyl halides 16a-d (0.01
mol) and the respective cycloalkanone oxime 2-7 (0.025 mol) in THF (100 ml) at room temperature. Stirring was
continued overnight, the solvent was then evaporated in vacuo, and the residual solid was washed with water to
get rid of triethylamine salt. The crude product was collected and recrystallized from ethanol. The following
compounds were synthesized using this method:
1
1-(4-Chlorophenyl)-3-(2-thenoyl)-1,2,4-triazaspiro[4.4]non-2-ene (10b). H NMR, δ, ppm; 8.2-7.2
(7H, m, aromatic), 5.5 (1H, s, NH), 2.3-1.6 (8H, m, cyclopentane protons). 13C NMR, δ, ppm: 174.3 (C=O),
146.9 (C=N), 141.5, 140.2, 135.2, 135.0, 129.1, 128.2, 128.0, 120.8 (8 aromatic carbons), 87.9 (spiro carbon),
34.9, 24.9 (cyclopentane carbons). IR, ν, cm-1: 3370 (NH), 1660 (C=O).
1
1-(4-Chlorophenyl)-3-phenylaminocarbonyl-1,2,4-triazaspiro[4.4]non-2-ene (10d). H NMR, δ, ppm:
9.6 (1H, s, C6H5NH), 7.6-7.1 (9H, m, aromatic), 56 (1H, s, NH), 2.3-1.7 (8H, m, cyclopentane protons).
13C NMR, δ, ppm: 159.8 (C=O), 146.9 (C=N), 141.3, 135.3, 134.8, 132.4, 129.1, 127.9, 127.5, 115.9 (8 aromatic
carbons), 87.4 (spiro carbon), 34.7, 24.8 (cyclopentane carbons). IR, ν, cm-1: 3350 (NH), 1655 (C=O).
1404

1-(4-Chlorophenyl)-3-(2-furoyl)-1,2,4-triazaspiro[4.5]dec-2-ene (11a). 1H NMR, δ, ppm: 8.3-7.1 (7H,
m, aromatic), 5.5 (1H, s, NH), 1.9-1.1 (8H, m, cyclohexane protons). 13C NMR, δ, ppm: 174.2 (C=O), 147.4
(C=N), 141.6, 140.1, 135.1, 135.0, 128.9, 128.1, 127.9, 120.6 (8 aromatic carbons), 87.8 (spiro carbon), 35.5,
24.7, 23.1 (cyclohexane carbons). IR, ν, cm-1: 3360 (NH), 1665 (C=O).
1
1-(4-Chlorophenyl)-3-(2-thenoyl)-1,2,4-triazaspiro[4.5]dec-2-ene (11b). H NMR, δ, ppm: 8.3-7.1
(7H, m, aromatic), 5.5 (1H, s, NH), 1.9-1.1 (10H, m, cyclohexane protons). 13C NMR, δ, ppm: 174.2 (C=O),
147.4 (C=N), 141.6, 140.1, 135.1, 135.0, 128.9, 128.1, 127.9, 120.6 (8 aromatic carbons), 87.8 (spiro carbon),
35.5, 24.7, 23.1 (cyclohexane carbons). IR, ν, cm-1: 3375 (NH), 1660 (C=O).
1-Phenyl-3-phenylaminocarbonyl-1,2,4-triazaspiro[4.5]dec-2-ene (11c). 1H NMR, δ, ppm: 9.6 (1H, s,
C6H5NH), 7.5-7.0 (10H, m, aromatic), 5.5 (1H, s, NH), 2.1-1.4 (10H, m, cyclohexane protons). 13C NMR,
δ, ppm: 159.9 (C=O), 147.2 (C=N), 141.5, 135.4, 134.7, 132.6, 129.2, 127.8, 123.2, 115.8 (8 aromatic carbons),
88.2 (spiro carbon), 35.7, 24.8, 22.9 (cyclohexane carbons). IR, ν, cm-1: 3350 (NH), 1655 (C=O).
1-(4-Chlorophenyl)-3-phenylaminocarbonyl-1,2,4-triazaspiro[4.5]dec-2-ene (11d). 1H NMR, δ, ppm;
9.7 (1H, s, C6H5NH), 7.7-7.0 (9H, m, aromatic), 5.5 (1H, s, NH), 2.1-1.4 (10H, m, cyclohexane protons). 13C
NMR, δ, ppm: 159.9 (C=O), 147.0 (C=N), 141.3, 135.3, 134.8, 132.2, 129.0, 127.9, 127.6, 115.7 (8 aromatic
carbons), 88.1 (spiro carbon), 35.6, 24.7, 23.0 (cyclohexane carbons). IR, ν, cm-1: 3350 (NH), 1650 (C=O).
1
1-(4-Chlorophenyl)-3-(2-furoyl)-8-methyl-1,2,4-triazaspiro[4.5]dec-2-ene (12a). H NMR, δ, ppm:
8.2-7.1 (7H, m, aromatic), 5.5 (1H, s, NH), 2.0-1.1 (9H, m, cyclohexane protons), 0.9 (3H, s, CH3). 13C NMR,
δ, ppm: 173.5 (C=O), 147.4 (C=N), 141.5, 140.2, 135.2, 135.0, 129.1, 128.2, 128.0, 120.8 (8 aromatic carbons),
87.9 (spiro carbon), 35.2, 28.4, 22.6 (cyclohexane carbons), 31.4 (CH3 at cyclohexane ring). IR, ν, cm-1: 3365
(NH), 1665 (C=O).
1
1-(4-Chlorophenyl)-8-methyl-3-(2-thenoyl)-1,2,4-triazaspiro[4.5]dec-2-ene (12b). H NMR, δ, ppm:
8.2-7.1 (7H, m, aromatic), 5.5 (1H, s, NH), 2.0-1.1 (9H, m, cyclohexane protons), 0.9 (1H, s, CH3). 13C NMR, δ,
ppm: 174.2 (C=O), 146.4 (C=N), 141.3, 140.0, 134.8, 134.6, 128.9, 127.9, 127.7, 120.1 (8 aromatic carbons),
89.0 (spiro carbon), 34.8, 29.3, 22.1 (cyclohexane carbons), 31.3 (CH3 at cyclohexane ring). IR, ν, cm-1: 3370
(NH), 1665 (C=O).
1
8-Methyl-1-phenyl-3-phenylaminocarbonyl-1,2,4-triazaspiro[4.5]dec-2-ene (12c). H NMR, δ, ppm:
9.8 (1H, s, C6H5NH), 7.6-7.1 (10H, m, aromatic), 5.5 (1H, s, NH), 1.9-1.1 (9H, m, cyclohexane protons), 0.9
(3H, s, CH3). 13C NMR, δ, ppm: 159.9 (C=O), 146.9 (C=N), 141.8, 135.3, 134.8, 132.2, 129.0, 127.9, 123.6,
115.7 (8 aromatic carbons), 88.9 (spiro carbon), 34.9, 28.1, 22.1 (cyclohexane carbons), 31.2 (CH3 at
cyclohexane ring). IR, ν, cm-1: 3355 (NH), 1655 (C=O).
1
1-(4-Chlorophenyl)-8-methyl-3-phenylaminocarbonyl-1,2,4-triazaspiro[4.5]dec-2-ene (12d). H NMR,
δ, ppm: 9.6 (1H, s, C6H5NH), 7.6-7.0 (9H, m, aromatic), 5.6 (1H, s, NH), 2.1-1.2 (9H, m, cyclohexane protons),
1.0 (3H, s, CH3). 13C NMR, δ, ppm: 159.8 (C=O), 146.8 (C=N), 141.3, 135.3, 134.8, 132.2, 129.0, 127.9, 127.6,
115.7 (8 aromatic carbons), 89.0 (spiro carbon), 34.8, 27.9, 22.3 (cyclohexane carbons), 31.3 (CH3 at
cyclohexane ring). IR, ν, cm-1: 3350 (NH), 1650 (C=O).
1
8-tert-Butyl-1-(4-chlorophenyl)-3-(2-furoyl)-1,2,4-triazaspiro[4.5]dec-2-ene (13a). H NMR, δ, ppm:
8.0-7.2 (7H, m, aromatic), 5.5 (1H, s, NH), 1.9-0.9 (9H, m, cyclohexane protons), 0.8 (9H, s, (CH3)3C).
13C NMR, δ, ppm: 173.3 (C=O), 147.3 (C=N), 141.5, 140.2, 135.2, 135.0, 129.1, 128.2, 128.0, 120.8 (8 aromatic
carbons), 87.9 (spiro carbon), 47.0, 35.5, 32.4, 27.6, 24.1 (tert-butyl carbons). IR, ν, cm-1: 3360 (NH), 1660
(C=O).
8-tert-Butyl-1-(4-chlorophenyl)-3-(2-thenoyl)-1,2,4-triazaspiro[4.5]dec-2-ene (13b). 1H NMR,
δ, ppm: 8.3-7.2 (7H, m, aromatic), 5.6 (1H, s, NH), 2.1-1.1 (9H, m, cyclohexane protons), 0.9 (9H, s, (CH3)3C).
13C NMR, δ, ppm: 174.1 (C=O), 147.2 (C=N), 141.4, 140.2, 135.1, 134.9, 129.1, 128.3, 128.0, 120.8 (8 aromatic
carbons), 87.8 (spiro carbon), 47.1, 35.7, 32.4, 27.6, 24.1 (tert-butyl carbons). IR, ν, cm-1: 3370 (NH), 1665
(C=O).
1405

8-tert-Butyl-1-(4-chlorophenyl)-3-phenylaminocarbonyl-1,2,4-triazaspiro[4.5]dec-2-ene (13d).
1H NMR, δ, ppm: 9.6 (1H, s, C6H5NH), 7.6-7.0 (9H, m, aromatic), 5.5 (1H, s, NH), 2.0-1.0 (9H, m, cyclohexane
protons), 0.9 (9H, s, (CH3)3C). 13C NMR, δ, ppm: 159.9 (C=O), 146.9 (C=N), 141.3, 135.3, 134.8, 132.2, 129.0,
127.9, 127.6, 115.7 (8 aromatic carbons), 88.9 (spiro carbon), 46.9, 35.7, 32.4, 27.5, 24.0 (tert-butyl carbons).
IR, ν, cm-1: 3360 (NH), 1655 (C=O).
1
1-(4-Chlorophenyl)-3-(2-furoyl)-1,2,4-triazaspiro[4.6]undec-2-ene (14a). H NMR, δ, ppm: 7.8-6.8
(7H, m, aromatic), 5.6 (1H, s, NH), 2.3-1.5 (12H, m, cycloheptane protons). 13C NMR, δ, ppm: 173.6 (C=O),
147.6 (C=N), 141.5, 140.2, 135.2, 135.0, 129.1, 128.2, 128.0, 120.8 (8 aromatic carbons), 88.9 (spiro carbon),
39.3, 28.0, 22.2 (cycloheptane carbons). IR, ν, cm-1: 3365 (NH), 1660 (C=O).
1
1-(4-Chlorophenyl)-3-(2-thenoyl)-1,2,4-triazaspiro[4.6]undec-2-ene (14b). H NMR, δ, ppm; 8.2-7.1
(7H, m, aromatic), 5.6 (1H, s, NH), 2.4-1.6 (12H, m, cycloheptane protons). 13C NMR, δ, ppm: 174.2 (C=O),
147.3 (C=N), 141.2, 139.9, 135.0, 134.9, 128.7, 127.9, 127.6, 120.1 (8 aromatic carbons), 88.7 (spiro carbon),
39.4, 28.2, 22.3 (cycloheptane carbons). IR, ν, cm-1: 3360 (NH), 1660 (C=O).
1-Phenyl-3-phenylaminocarbonyl-1,2,4-triazaspiro[4.6]undec-2-ene (14c). 1H NMR, δ, ppm: 9.9
(1H, s, C6H5NH), 7.6-7.1 (10H, m, aromatic), 5.6 (1H, s, NH), 2.4-1.6 (12H, m, cycloheptane protons).
13C NMR, δ, ppm: 159.9 (C=O), 147.1 (C=N), 141.8, 135.3, 134.8, 132.2, 129.0, 127.9, 123.4, 115.7 (8 aromatic
carbons), 88.9 (spiro carbon), 39.6, 28.4, 22.4 (cycloheptane carbons). IR, ν, cm-1: 3355 (NH), 1650 (C=O).
1
1-(4-Chlorophenyl)-3-(2-thenoyl)-1,2,4-triazaspiro[4.7]dodec-2-ene (15b). H NMR, δ, ppm: 8.3-7.1
(7H, m, aromatic), 5.6 (1H, s, NH), 2.4-1.2 (14H, m, cyclooctane protons). 13C NMR, δ, ppm: 174.3 (C=O),
147.1 (C=N), 141.6, 140.2, 135.1, 135.0, 129.1, 128.1, 128.0, 120.5 (8 aromatic carbons), 88.6 (spiro carbon),
41.9, 36.5, 27.2, 21.8 (cyclooctane carbons). IR, ν, cm-1: 3370 (NH), 1665 (C=O).
1-(4-Chlorophenyl)-3-phenylaminocarbonyl-1,2,4-triazaspiro[4.5]dodec-2-ene (15d). 1H NMR,
δ, ppm: 10.0 (1H, s, C6H5NH), 7.8-7.2 (9H, m, aromatic), 5.6 (1H, s, NH), 2.3-1.1 (14H, m, cyclooctane
protons). 13C NMR, δ, ppm: 159.9 (C=O), 147.2 (C=N), 141.3, 135.3, 134.8, 132.2, 129.0, 127.9, 127.6, 115.7
(8 aromatic carbons), 88.9 (spiro carbon), 42.0, 36.6, 27.2, 21.9 (cyclooctane carbons). IR, ν, cm-1: 3360 (NH),
1655 (C=O).
Author wishes to thank Dr. P. H. Boyle, Trinity College, Dublin 2, Ireland, for obtaining the NMR and
mass spectra.
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1407