N-Isopropenylazoles: I. Direct N-Isopropenylation of Azoles with Propyne and Allene

Article abstract of DOI:10.1023/A:1025502016921

A number of previously unknown N-isopropenyl-substituted pyrroles, indoles, and di- and -triazoles were synthesized in 20-86% yield by reaction of the corresponding azole with an equilibrium mixture of propyne with allene or pure propyne and allene in the system KOH-DMSO (105-145°C, 5-15 h, atmospheric or elevated pressure). The reaction is regioselective. The electronic and steric structure and the degree of conjugation between the exocyclic double bond and the azole ring are discussed on the basis of the ¹H and ¹³C NMR spectra. Almost complete absence of p-π conjugation in N-disubstituted N-isopropenylazoles have been found.

Full text of DOI:10.1023/A:1025502016921

Russian Journal of Organic Chemistry, Vol. 39, No. 3, 2003, pp. 408 414. Translated from Zhurnal Organicheskoi Khimii, Vol. 39, No. 3, 2003,
pp. 437 442.
Original Russian Text Copyright
2003 by Trofimov, Tarasova, Shemetova, Afonin, Klyba, Baikalova, A.I.Mikhaleva.
Dedicated to Full Member of the Russian Academy of Sciences
I.P. Beletskaya on Her Jubilee
N-Isopropenylazoles: I. Direct
N-Isopropenylation of Azoles with Propyne and Allene
B. A. Trofimov, O. A. Tarasova, M. A. Shemetova, A. V. Afonin, L. V. Klyba,
L. V. Baikalova, and A. I. Mikhaleva
Irkutsk Institute of Chemistry, Siberian Division, Russian Academy of Sciences,
ul. Favorskogo 1, Irkutsk, 664033 Russia
Received July 10, 2002
Abstract A number of previously unknown N-isopropenyl-substituted pyrroles, indoles, and di- and -tri-
azoles were synthesized in 20 86% yield by reaction of the corresponding azole with an equilibrium mixture
of propyne with allene or pure propyne and allene in the system KOH DMSO (105 145 C, 5 15 h, atmos-
pheric or elevated pressure). The reaction is regioselective. The electronic and steric structure and the degree
1
of conjugation between the exocyclic double bond and the azole ring are discussed on the basis of the H
and 13C NMR spectra. Almost complete absence of p conjugation in , -disubstituted N-isopropenylazoles
have been found.
Direct vinylation of biologically important NH-
heterocycles, such as pyrroles, indoles, and di- and
triazoles, with acetylene has been studied in sufficient
detail. Pyrrole [1] and substituted NH-pyrroles [2 4]
are known to readily react with acetylene in the
system KOH DMSO at 100 120 C (3 h) under
atmospheric or elevated pressure to give the corre-
sponding N-vinyl derivatives in quantitative yield.
Vinylation with acetylene under pressure in aqueous
dioxane in the presence of 30% KOH was reported for
imidazole, benzimidazole (160 180 C, 1 h) [5], pyr-
azole (160 165 C, 3 h, with no water added) [6],
indole, and 1,2,4-triazole (220 C, 30 min and 3 4 h,
respectively) [7, 8]. In the reaction with pyrazole,
3 5% CuCl can be used as catalyst instead of KOH
[6]. Vinylation with acetylene under atmospheric
pressure was performed for imidazole (5% CuCl as
catalyst), benzimidazole [8% Cd(OAc)2, N-methyl-
pyrrolidinone, 180 C, 16 28 h) [9], and 1,2,4-triazole
(40% KOH, sulfolane or triethylene glycol, 205 C,
12 h) [10]. The yields of the corresponding N-vinyl-
azoles ranged from 67 to 91%.
(Cp2TiCH2ClAlMe2) [11]. N-Isopropenylbenzotriazole
was obtained in two ways: (1) from N-vinylbenzotri-
azole, by reaction with BuLi and subsequent treatment
of the lithium derivative with MeI (yield 44%) [12];
and (2) by transvinylation of benzotriazole with
isopropenyl acetate in the presence of HgSO4 (yield
81%; N-acetylbenzotriazole was formed as by-prod-
uct) [13]. N-Isopropenylimidazole was synthesized in
4% yield by reaction of N,N -carbonyldiimidazole
with acetone [14]. Physical constants were given only
for N-isopropenylbenzotriazole [12].
Propyne allene mixture is a by-product of high-
temperature pyrolysis of petroleum derivatives [15].
It is now the most accessible acetylene raw material
ranking next after acetylene; moreover, it needs to
be utilized. Therefore, development of synthetic
procedures on the basis of propyne allene mixture is
justified from the viewpoints of both economy and
ecology.
We recently demonstrated for the first time the
possibility for direct N-isopropenylation of pyrrole
with propyne allene mixture in the system KOH
DMSO under atmospheric pressure [16]. N-Isopro-
penylpyrrole was thus obtained in 60% yield. This
compound may be regarded as a new pyrrole building
block and a monomer.
Up to now, only a few N-isopropenyl azoles have
been reported. N-Isopropenyl derivatives of indole,
3-phenylindole, and aza- and diazaindoles were syn-
thesized in 50 56% yield by reaction of the corre-
sponding N-acyl derivatives with Tebbe’s reagent
1070-4280/03/3903-0408$25.00 2003 MAIK Nauka/Interperiodica

N-ISOPROPENYLAZOLES: I.
409
Scheme 1.
The present communication gives first results of
our systematic study of direct isopropenylation of
various azoles, namely pyrrole (I), 2,3-dimethylpyr-
role (II), 2,3,5-trimethylpyrrole (III), indole (IV),
4,5,6,7-tetrahydroindole (V), 2-methyl-4,5,6,7-tetra-
hydroindole (VI), 2-phenylpyrrole (VII), imidazole
(VIII), 2-methylimidazole (IX), pyrazole (X), and
1,2,4-triazole (XI). As isopropenylating agent we used
both propyne allene mixture (4:1) and its individual
components. Experiments were carried out under
atmospheric and elevated pressure, the temperature
was 105 145 C. The progress of the reactions was
monitored by GLC and TLC, following disappearance
of the initial azole.
be necessary. The presence of a small amount of water
is also required to ensure successful and safe process;
for this purpose, DMSO containing 0.4% of H2O may
be used. Anhydrous DMSO promotes spontaneous
exothermic polymerization of propyne and allene.
Addition of a larger amount of water (to a concentra-
tion of more than 0.4%) reduces the basicity of the
system, and the reaction is suppressed. The relatively
high temperature (125 145 C), as compared to vinyla-
tion in KOH DMSO, favors formation of by-products
via reaction of DMSO with propyne and allene;
presumably, isopropenyl methyl sulfide and diiso-
propenyl sulfide are thus obtained, by analogy with
the formation of methyl vinyl sulfide and divinyl
sulfide in the system acetylene KOH DMSO [18]. In
fact, 1 2% of volatile components was detected by
GLC analysis of the reaction mixtures (these compo-
nents were not examined).
As expected, the reactions under pressure were
more effective. This follows from the results of iso-
propenylation of azoles I, VIII, and IX. 2-Phenylpyr-
role (VII) and 1,2,4-triazole (XI) failed to react under
atmospheric pressure. The yield of the final N-iso-
propenylazole strongly depends on the substrate-to-
reagent ratio (under pressure). The yield increases
as the concentration of isopropenylating agent rises
(Table 1).
Table 1 contains the reaction conditions and the
yields of the products (Scheme 1). It is seen that the
reaction direction does not depend on the alkenylating
agent. The reaction is regioselective: it gives only the
corresponding N-isopropenyl derivatives. Only in the
reaction with pyrrole (I) under pressure, we isolated
and identified (by GLC using an authentic sample
1
[17] and by H NMR spectroscopy) N-(1-E-propenyl)-
pyrrole. Its yield was 0.7% (1% in the mixture).
With pyrrole (I) as an example, we examined the
effect of the amount of catalyst and temperature on
the yield of N-isopropenylpyrrole (XII). The reactions
were carried out under elevated pressure. Almost no
reaction occurred in the presence of 30 wt % of KOH
(relative to the initial azole); such concentration of the
catalyst is usual for the vinylation of pyrroles [3, 4].
An equimolar or larger amount of alkali was found to
In the vinylation of pyrroles with acetylene in the
system KOH DMSO [1 4], pyrrolate ion readily
attacks acetylene molecule at 100 120 C, and sub-
stitution of the azole ring weakly affects the yield of
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 3 2003

410
TROFIMOV et al.
Table 1. Isopropenylation of azoles I XI with propyne allene mixture and pure propyne and alene; molar ratio azole
isopropenylating agent KOH DMSO (0.4% H2O) 1: 1.5: 1.1: 7.7
Initial
azole
Isopropenylating
agent
Reaction
time, h
Methoda
Temperature,
C
Product
Yield, %
I
Propyne allene
Allene
a [16]
125 135
105 115
125 135
125 135
135 300
125 135
135 145
130 135
135 145
125 135
125 135
125 135
130 140
125 135
135 145
135 145
130 135
130 140
130 140
5
6
6
3.5
XII
59
34
Traces
b
bb
bc
Black polymer
b
a
a
a
a
b
b
b
a
b
b
a
b
b
6
10
7
15
9
5
6
6
7
6
5
8
6
73 (86)d
II
Propyne allene
Propyne allene
Propyne allene
Propyne
Allene
Allene
XIII
XIV
XV
XVI
XVII
XVIII
40
39
40
66
34
III
IV
V
VI
VII
9
28e
23
VIII
Propyne allene
Allene
Allene
Propyne allene
Allene
Allene
XIX
60 (70)f
34
IX
X
XX
XXI
38
46
20
XI
6
XXII
a
b
c
d
e
f
Method a: under atmospheric pressure; method b: under pressure.
Molar ratio pyrrole KOH 1:0.3; 63% of the initial pyrrole was recovered.
In anhydrous DMSO.
Molar ratio azole allene 1:2.3.
Molar ratio azole allene 1:7.
Molar ratio azole allene 1:3.
Table 2. Boiling points, refractive indices, elemental analyses, and molecular weights (GC MS data) of N-isopropenyl-
azoles XII XXII
Found, %
H
Calculated, %
Comp.
no.
bp,
(p, mm)
C
M+
(Irel, %)
n2D0
Formula
Mcalc
C
N
C
H
N
XII
147a
1.5186a 78.79 8.48 12.86
C7H9N
78.46 8.47 13.17
79.95 9.69 10.36
107 (100)
135 (100)
149 (100)
157 (100)
161 (95)
175 (70)
183 (100)
108 (100)
122 (100)
108 (100)
109 (91)
107.16
135.21
149.24
157.22
161.25
175.27
183.25
108.14
122.17
108.14
109.13
XIII
XIV
XV
XVI
XVII
XVIII
XIX
XX
73 (18)
77 (11)
109 (8)
78 (3)
105 (5)
110 (5)
98 (25)
60 (3)
1.5070
1.4984
1.6066
1.5442
1.5252
1.5988
1.5224
1.5574
1.5126
1.5040
79.80 9.63 10.35
C9H13N
C10H15N
C11H11N
C11H15N
C12H17N
C13H13N
C6H8N2
C7H10N2
C6H8N2
C5H7N3
80.50 9.97
84.00 7.03
81.79 9.30
81.94 9.70
84.92 7.09
9.23
8.69
8.63
7.88
7.60
80.48 10.13
84.04 7.05
81.94 9.38
82.23 9.78
85.21 7.15
9.39
8.91
8.69
7.99
7.64
66.39 7.46 25.84
68.67 8.13 22.78
66.43 7.34 25.72
54.83 6.40 38.30
66.64 7.46 25.90
68.82 8.25 22.93
66.64 7.46 25.90
55.03 6.47 38.50
XXI
XXII
64 (30)
75 (14)
a
Data of [16].
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 3 2003

N-ISOPROPENYLAZOLES: I.
411
the product (75 97% [3, 4, 15]). By contrast, the yield
of N-isopropenylazoles (Table 1) considerably
depends on the initial azole structure, though the
reaction is carried out at higher temperature. The
presence of a substituent in the -position of the azole
ring is likely to hinder attack on bulkier propyne and
allene molecules for steric reasons, so that the yield
of N-isopropenyl derivatives XIII XVIII, and XX
is lower than the yield of the corresponding products
from unsubstituted pyrrole (I) and imidazole (VIII).
Moderate yields of N-isopropenylindole (XV) and
N-isopropenyl-2-phenylpyrrole (XVIII) are likely to
result from the reduced nucleophilicity of the corre-
sponding anions [19] due to electron-acceptor effect
of fused benzene ring (indole) and phenyl group
(2-phenylpyrrole). The same factor is responsible for
the lowest (in the series of unsubstituted azoles) yields
of N-isopropenyl derivatives from pyrazole and 1,2,4-
triazole (40 and 26%, respectively); although their
molecules have no bulky substituents, the anions
derived therefrom are least nucleophilic.
Thus we have developed a new general and simple
procedure for introduction of isopropenyl group into
azole ring. Previously unknown N-isopropenylazoles
have been synthesized, which supplement the series
of N-alkenylazoles, highly reactive building blocks
and monomers.
EXPERIMENTAL
1
The H and 13C NMR spectra were recorded on
1
a Bruker DPX-400 spectrometer (400.13 MHz for H
and 100.69 MHz for 13C) using chloroform-d as sol-
vent and hexamethyldisiloxane as internal reference.
The IR spectra were measured on a Bruker IFS-25
spectrometer from samples prepared as thin films.
The mass spectra (electron impact, 60 eV) were run
on an LKB-2091 GC MS system (SE-54 capillary
column, 38 m; injector temperature 250 C; oven tem-
perature programming from 70 to 200 C at a rate of
10 deg/min; ion source temperature 240 C). The reac-
tion mixtures were analyzed by GLC with an LKhM-
8MD chromatograph 3.5-m 3-mm column packed
with 5% of XE-60 on Chromaton N-AW-HMDS;
thermal conductivity detector; carrier gas helium;
oven temperature 70 180 C, depending on the com-
ponent volatility; detector temperature 200 C; injector
temperature 250 C. Commercial DMSO containing
0.4% of water and commercial potassium hydroxide
containing 15% of water (2KOH H2O) were used.
Allene was prepared by dehalogenation of 2,3-di-
chloro-1-propene with zinc dust according to the
procedure reported in [21]; its purity was >99%.
Propyne (98%) was commercial product (Aldrich).
Propyne allene mixture (4:1) was prepared from allyl
chloride in the system KOH DMSO.
The structure of products XII XXII was confirmed
by the NMR, IR, and mass spectra and elemental
analyses (Tables 2 4). The mass spectra of all these
compounds (Table 2) contain the molecular ion peak
which is the base peak or next in intensity.
1
Analysis of the H and 13C NMR spectra (Table 3)
revealed some structural features of N-isopropenyl-
azoles XII XXII. Molecules XII, XIX, XXI, and
XXII having no other substituents in the heteroring
are characterized by coplanar arrangement of the
N-isopropenyl group and the heteroring. This follows
from the upfield shift of the CH2 carbon signal
relative to the corresponding signal of propene
(
115.5 ppm [20]) due to p
conjugation. The
prCesence of a substituent in the -position with respect
to the N1 atom (compounds XIII, XVIII, and XX),
as well as of fused benzene ring (XV and XVI),
hampers coplanar arrangement of the isopropenyl
group and the heteroring; therefore, inversion of the
HA and HB signals is observed due to anisotropic
effect of the azole ring and the CH2 carbon signal
shifts downfield by 10 ppm. In molecules XIV and
XV where both -positions are occupied, the isopro-
penyl group is likely to be oriented orthogonally with
respect to the heteroring plane: the 13C chemical shift
of the CH2 moiety is the same as in the propene
Synthesis of N-isopropenylazoles XII XXII
(general procedure). a. Under atmospheric pressure.
A 250-ml glass flask equipped with a stirrer, reflux
condenser, thermometer, and gas-inlet and gas-outlet
tubes was charged with 0.2 mol of azole I XI, 14 g
(0.215 mol) of 2KOH H2O, and 100 ml of DMSO.
The mixture was heated to 125 145 C (Table 1), and
propyne allene mixture (4:1) or propyne (in the case
of 4,5,6,7-tetrahydroindole) was passed through the
mixture over a period of 5 15 h (depending on the
substrate, see Table 1) under stirring. Unreacted
propyne and allene were collected in a trap cooled to
78 C and were returned to the reaction. When the
reaction was complete, the mixture was cooled and
diluted with 200 ml of water. Pyrroles XIII and XIV
and indoles XV and XVI were isolated by extraction
with ether (4 50 ml), the combined extracts were
washed with three portions of water to remove
molecule, which means that p
conjugation with
the isopropenyl group is absent.
N-Isopropenylazoles XII XXII show in the IR
spectra (Table 4) a strong absorption band at 1647
1
1663 cm , which corresponds to stretching vibrations
of the double C C bond in the isopropenyl fragment.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 3 2003

412
TROFIMOV et al.
Table 3. 1H and 13C NMR spectra of N-isopropenylazoles XII XXII
1H NMR spectrum,a , ppm
Comp.
13C NMR spectrum, C, ppm
CH2 Me azole
no.
HA, q HB, q Me, d.d
azole
>C
XII
4.54
4.91
2.19
6.95
6.21
t
t
(2H, 2-H, 5-H), 140.69
(2H, 3-H, 4-H),
97.93 20.39 118.24 (C2, C5), 109.56
(C3, C4)
3J = 2.2 Hz
XIII
4.94
4.82
2.09
5.96 d (4-H), 6.57 d (5-H), 142.19 108.37 22.70 124.49 (C2), 116.17 (C3),
3J = 2.8 Hz; 2.14 s (2-Me),
109.34 (C4), 118.15 (C5),
2.02 s (3-Me)
10.88
(2-Me),
11.49
(3-Me)
XIV
XV
5.28
5.06
4.80
5.22
4.92
5.16
4.78
4.90
1.95
2.27
2.12
1.98
5.68 s (4-H), 2.06 s (2-Me), 142.00 115.11 22.97 123.12 (C2), 113.58 (C3),
1.97
s
(3-Me), 2.12
s
107.40 (C4), 125.94 (C5),
10.00 (2-Me), 11.05
(3-Me), 12.14 (5-Me)
(5-Me)
7.21 d (2-H), 6.55 d (3-H), 140.85 105.73 22.16 126.33 (C2), 103.11 (C3),
3J = 3.3 Hz, 7.62 m (4-H),
7.21 m (5-H), 7.11 m (6-H),
7.62 m (7)
121.18 (C4), 122.35 (C5),
120.36 (C6), 112.02 (C7),
135.61 (C8), 129.58 (C9)
XVI
XVII
6.64 d (2-H), 5.96 d (3-H), 141.15 105.24 22.37 118.27 (C2), 107.39 (C3),
3J = 2.8 Hz, 2.52 m (2H,
4-H), 1.75 m (4H, 5-H,
6-H), 2.59 m (2H, 7-H)
23.35 (C4), 23.88 (C5),
23.35 (C6), 24.22 (C7),
127.78 (C8), 119.06 (C9)
5.69 s (3-H), 2.46 m (4H, 141.33 114.28 22.88 126.71 (C2), 15.36 (C3),
4-H, 7-H), 1.74 m (4H,
5-H, 6-H), 2.16 s (2-Me)
23.02 (C4), 23.85 (C5),
23.65 (C6), 22.55 (C7),
126.71 (C8), 116.44 (C9),
12.25 (2-Me)
XVIII
4.97
4.95
1.90
6.30 d.d (3-H), 6.22 t (4-H), 143.34 110.14 22.38 133.08 (C2), 110.50 (C3),
3
6.78 d.d (5-H), J3,4
=
108.34 (C4), 123.58 (C5),
133.82 (Ci), 127.53 (Co),
128.30 (Cm), 123.58 (Cp)
3
3.8 Hz, J4,5 = 2.8 Hz,
4J3,5 = 3.8 Hz, 7.42 m (2H,
o-H), 7.32 m (2H, m-H),
7.22 m (p-H)
XIX
XX
4.74
5.13
4.68
5.05
4.96
5.33
2.22
2.10
2.28
7.72 s (2-H), 7.08 d (4-H), 138.14 101.64 20.20 134.72 (C2), 129.81 (C3),
7.15 d (5-H), J = 1.4 Hz
3
116.48 (C5)
6.92 d (4-H), 6.87 d (5-H), 140.10 111.24 22.30 143.86 (C2), 118.51 (C4),
3J = 0.8 Hz
127.31 (C5), 14.03 (2-Me)
XXI
7.60 d.d (3-H), 6.34 t (4-H), 140.94
99.61 19.50 140.44 (C3), 106.78 (C4),
3
7.68 d.d (5-H), J3,4
=
=
126.57 (C5)
3J4,5 = 2.0 Hz, J3,5
4
0.8 Hz
XXII
4.84
5.48
2.26
7.94 s (3-H), 8.25 s (5-H)
138.07 103.32 18.99 151.97 (C3), 140.63 (C5)
a
4J(CH3, HA) = 1.2 Hz, 4J(CH3, HB) = 0.6 Hz.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 3 2003

N-ISOPROPENYLAZOLES: I.
Table 4. IR spectra of N-isopropenylazoles XII XXII
413
Comp.
no.
1
IR spectrum, , cm
XII
602, 726 s, 851, 906 w, 957, 1002, 1048, 1093 s, 1260, 1306, 1345, 1381, 1441, 1484, 1525, 1554, 1647 s
(C CH2), 2924, 2955, 2990, 3106, 3140
XIII
XIV
XV
612 w, 634, 700 s, 826 w, 881, 902 sh, 931 w, 999 w, 1052 w, 1077 w, 1160 w, 1196, 1250 w, 1340 s, 1387,
1434, 1486 s, 1520 w, 1580 w, 1653 s (C CH2), 2739 w, 2864, 2920 s, 2980, 3100 w
626, 679 w, 775 s, 900 s, 974 w, 1003 w, 1149 w, 1169 w, 1261 w, 1331 s, 1359 s, 1387 s, 1416 s, 1439 sh,
1524, 1595 w, 1656 s (C CH2), 2732 w, 2959 s, 2919 s, 2973 s, 3024 sh, 3085 w, 3101 w
581, 599 w, 671, 719, 742 s, 766, 882, 931 w, 988 w, 1017, 1081 w, 1121 w, 1153 w, 1178, 1215 s, 1250,
1295, 1332 s, 1351, 1370, 1457 s, 1475, 1519, 1573 w, 1607 w, 1650 s (C CH2), 2949 w, 2921 w,
2953 w, 2986 w, 3050, 3080 w, 3107 w, 3130 sh
XVI
609, 637, 699 s, 852, 864, 913, 958 w, 992 w, 1059, 1141, 1158, 1181 s, 1239, 1256 w, 1294, 1311, 1323,
1341 s, 1385 s, 1439 s, 1483 s, 1516 w, 1581 w, 1649 s (C CH2), 2845 s, 2928 s, 2982, 3098 w
XVII
XVIII
600 w, 625 w, 645 w, 701 w, 727 w, 772 s, 812, 897 s, 944 w, 1006 w, 1086, 1147, 1236, 1260, 1300, 1316,
1362, 1388 s, 1428 s, 1522, 1594 w, 1654 s (C CH2), 2730 w, 2841 s, 2924 s, 2975, 3084 w, 3101 w
611, 661, 699 s, 713 s, 759 s, 795, 884 s, 912, 938 w, 974, 1005, 1028, 1053, 1075 s, 1112 w, 1155, 1192,
1241 w, 1266 w, 1295, 1325 s, 1341, 1377, 1415, 1443, 1463 s, 1496, 1543, 1574 w, 1602, 1653 s
(C CH2), 2848 w, 2878 w, 2920, 2958, 2982, 3032 sh, 3059, 3079, 3103
XIX
XX
605, 657, 733, 815, 870, 903, 1012, 1080, 1109, 1165, 1252, 1307, 1319, 1362, 1388, 1449, 1490 s, 1511,
1656 s (C CH2), 2924 w, 2956 w, 2991 w, 3111
602, 669, 699 w, 729, 898, 985, 1063 w, 1129, 1150, 1206, 1313 s, 1378 w, 1416 s, 1433 sh, 1494, 1524,
1658 s (C CH2), 2925 w, 2959 w, 2987 w, 3107
XXI
XXII
612 s, 645, 752 s, 870 s, 916, 956 s, 1000, 1048 s, 1085 s, 1169, 1201, 1334 s, 1394 s, 1434 s, 1519 s, 1657 s
(C CH2), 2921 w, 2968 w, 2993, 3124, 3145
612 s, 637, 672 s, 741, 882 s, 956 s, 998 s, 1058 w, 1128 s, 1159, 1217 s, 1249 w, 1282 s, 1303 s, 1349,
1381 sh, 1424 s, 1449, 1508 s, 1663 s (C CH2), 2857 w, 2926, 2962, 2994, 3119 s
DMSO, dried over MgSO4, and evaporated under
reduced pressure (50 mm). Further purification from
unreacted pyrrole was performed by column chrom-
atography on aluminum oxide using hexane or petro-
leum ether (bp 40 70 C) as eluent; the subsequent
vacuum distillation gave pure products. N-Isopro-
penylimidazole (XIX) and N-isopropenylpyrazole
(XXI) were isolated from the reaction mixture (after
dilution with water) by extraction into chloroform
(6 40 ml); the combined extracts were washed with
six portions of water to remove DMSO, dried over
CaCl2, and evaporated, and the residue was distilled
under reduced pressure.
b. Under pressure. A steel rotating high-pressure
reactor was charged with 0.2 mol of the corresponding
azole, 14 g (0.215 mol) of 2KOH H2O, 100 ml of
DMSO, and 12 g (0.3 mol) of allene which was
placed in a glass tube cooled to 78 C. The reactor
was closed and heated at 125 145 C for 5 6 h (see
Table 1). When the reaction was complete, the reactor
was cooled and opened (in none of the cases pressure
release was observed), and the products, N-isoprop-
enylazoles XII and XV XXII were isolated and
purified as described above in a. The yields, physical
constants, and spectral parameters of compounds XII
XXII are given in Tables 1 4.
N-[(E)-1-Propenyl)pyrrole was isolated as a 1:1
mixture with N-isopropenylpyrrole (XII) (0.3 g) by
distillation of the ether extract of the reaction mixture
obtained according to method b. Yield 0.7%, bp 83
1
86 C (80 mm). H NMR spectrum, , ppm (J, Hz):
6.77 t (2H, -H, pyrrole), 6.16 t (2H, -H, pyrrole),
J
= 2.2; 6.58 d.q (1H, NCH ), 5.60 m (1H,
,
CHCH3), Jt4rans = 13.7; 1.73 d.d (3H, CH3),
1
3JCH,Me = 6.8, J=CH,Me = 1.7. The GLC and H NMR
data coincided with those reported in [17].
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