Reaction of substituted benzofuroxanes with styrene

Full text of DOI:10.1023/A:1012438320918

Russian Journal of Organic Chemistry, Vol. 37, No. 6, 2001, pp. 892 893. Translated from Zhurnal Organicheskoi Khimii, Vol. 37, No. 6, 2001,
pp. 938 939.
,
Original Russian Text Copyright 2001 by Panasyuk, Mel nikova, Tselinskii.
SHORT
COMMUNICATIONS
*
Reaction of Substituted Benzofuroxanes with Styrene
,
P. M. Panasyuk, S. F. Mel nikova, and I. V. Tselinskii
St. Petersburg State Technological Institute, St. Petersburg, 198013 Russia
Received November 15, 2000
Reactions of benzofuroxanes with nucleophiles
Beirut reaction) is a procedure providing quinoxa-
tion of 5-substituted benzofuroxanes Ia e with
styrene in a boiling 2-propanol.
(
line-N,N -dioxides. In this reaction take part imines
1], enamines [2], enolate-anions [3], phenols [4], and
also olefins with a less active bond than that in
enamines [5]. The least studied are the latter reactions.
At the same time the availability of olefins is very
attractive for preparation of quinoxline-N,N -dioxides
derivatives.
The duration of the process decreased with grow-
ing electron-withdrawing character of the R substitu-
ent. For instance, 5-methoxybenzofuroxane (IIa) was
not fully consumed within 7 days whereas the reac-
tion between 5-nitrobenzofuroxane IIe completed in
[
6
8 h. The yield of 6(7)-R-3-phenylquinoxaline-N,N -
dioxide also grew with increasing electron-acceptor
character of the substituent.
We established that 6(7)-R-3-phenylquinoxaline-
N,N -dioxides IIa e form in 38 65% yields in reac-
Apparently the reaction involved intermediate
formation of dihydoquinoxaline-N,N -dioxide A as
evidenced the red color of the reaction mixture
characteristic of these compounds [6]. Intermediate
A is oxidized by the second benzofuroxane molecule
affording aromatic product II. Therewith the benzo-
furoxane was reduced into o-benzoquinone dioxime
(III) that was isolated from the reaction mixture and
R = OMe (a), Me (b), Cl (c), COOMe (d), NO (e).
2
Yields and characteristics of compounds synthesized
1
H NMR spectrum of the main isomer, , ppm
Compd. Yield,
Isomers
ratio
no.
%
3
5(8)
7(6)
8(5)
H , s
H
, d
H
, d
H
, d
Ph, m
R, s
IIa
IIb
IIc
IId
IIe
40
27
46
63
65
12:88
31:69
100:0
15:85
43:57
8.84
8.78
8.94
8.97
9.17
7.77
8.22
8.46
8.95
9.08
8.44
8.38
8.54
8.65
8.71
7.57
7.76
8.03
8.41
8.69
7.95, 7.55
7.97, 7.54
7.98, 7.57
8.00, 7.58
8.01, 7.59
3.99
2.55
3.98
Found, %
Calculated, %
H
Compd.
no.
Formula
C
H
N
C
N
IIa
IIb
IIc
IId
IIe
67.16
71.42
61.66
64.86
59.37
4.51
4.79
3.33
4.08
3.20
10.44
11.10
10.27
9.46
C H N O
67.24
71.47
62.01
65.12
59.78
4.75
4.90
3.54
4.18
3.60
10.47
11.11
10.31
9.52
1
5
12
2
3
C H N O
1
5
12
2
2
C H ClN O
1
4
9
2
2
C H N O
4
1
6
12
2
14.84
C H N O
14.86
1
4
9
3
4
*
The study was carried out under financial support of the Russian Foundation for Basic Research (grant no. 99-03-33085a).
070-4280/01/3706-0892$25.00 2001 MAIK Nauka/Interperiodica
1

REACTION OF SUBSTITUTED BENZOFUROXANES WITH STYRENE
893
identified by TLC comparing it with an authentic
sample specially prepared by reduction of the cor-
responding benzofuroxane with hydroxylamine [7].
The capability of benzofuroxanes to reduce the
aromatic structure of dihydroazines while converting
into ortho-benzoquinone dioximes is well known [8].
till weakly acidic pH. The precipitated benzoquinone
dioxime III was filtered off and dried.
1H NMR spectra were recorded on Bruker AC-300
instrument in DMSO-d , internal reference DMSO.
6
Mass spectra were measured on mass spectrometer
Varian CH-6 (ionizing voltage 70 V). TLC was
performed on Silufol UV-254 plates, eluent chloro-
form.
The composition and structure of compounds
obtained was confirmed by elemental analysis,
1
H NMR and mass spectra. In the mass spectra of
6(7)-R-3-phenylquinoxaline-N,N -dioxides the mole-
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+
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solutions [10]. However the data available are not
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A solution of 0.01 mol of benzofuroxane Ia e [11]
and 0.006 mol of styrene in 40 ml of 2-propanol was
heated at reflux till complete consumption of the
initial benzofuroxane (TLC monitoring). On cooling
the reaction mixture was evaporated to 10 ml
volume and diluted with 20 ml of ether. The
separated precipitate was filtered off and recrystal-
lized from 2-propanol. Thus were obtained quinoxa-
line-N,N -dioxides IIa e. The filtrate was evaporated
to dryness, the solid residue was treated with cold 5%
solution of NaOH, the solution obtained was filtered
again, and the filtrate was acidified with concn. HCl
7
8
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RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 6 2001