Synthesis of benzotriazolylsuccinimides in melt

Article abstract of DOI:10.1007/s11172-008-0063-2

N-Phenyl-3-(benzotriazol-1-yl)pyrrolidine-2,5-dione was synthesized by condensation of N-phenylmaleimide with benzotriazole in melt. The adducts of 2 moles of benzotriazole to different bismaleimides, namely, bis[3-(benzotriazol- 1-yl)pyrrolidine-2,5-dion

Full text of DOI:10.1007/s11172-008-0063-2

Russian Chemical Bulletin, International Edition, Vol. 57, No. 2, pp. 409—411, February, 2008
409
Synthesis of benzotriazolylsuccinimides in melt
b
c
c
I. A. Farion,a Z. M. Khaltarov, D. F. Kushnarev, and A. V. Rokhin
ꢀ
aBaikal Institute of Nature Management, Siberian Branch of the Russian Academy of Sciences,
6 ul. Sakhiyanovoi, 670047 UlanꢀUde, Russian Federation.
Fax: +7 (301 2) 43 4259. Eꢀmail: fariv@mail.ru
bBuryat State University,
24а ul. Smolina, 670000 UlanꢀUde, Russian Federation.
Fax: +7 (301 2) 43 4259. Eꢀmail: zurude@gmail.com
cIrkutsk State University,
1 prosp. K. Marksa, 664003 Irkutsk, Russian Federation.
Fax: +7 (395 2) 42 5935. Eꢀmail: aciu@chem.isu.ru
NꢀPhenylꢀ3ꢀ(benzotriazolꢀ1ꢀyl)pyrrolidineꢀ2,5ꢀdione was synthesized by condensation of
Nꢀphenylmaleimide with benzotriazole in melt. The adducts of 2 moles of benzotriazole to
different bismaleimides, namely, bis[3ꢀ(benzotriazolꢀ1ꢀyl)pyrrolidineꢀ2,5ꢀdiones] were obtained
under analogous conditions. These adducts, according to the data from 1Н and 13С NMR
spectroscopy, contain also (benzotriazolꢀ2ꢀyl)succinimide and residual maleimide fragments.
Key words: benzotriazole, Nꢀphenylmaleimide, maleimides, succinimides.
Scheme 1
Benzotriazole (Bt) is currently one of the interesting
heterocyclic benzoannulated compounds. The presence
of concatenated nitrogen atoms leads to such properties
as high N—Hꢀacidity (pKa 8.2),1 good complexation propꢀ
erties2 and high nucleophilicity.3
In practice, Bt is used as antifogging agent in photogꢀ
raphy and corrosion inhibitor.4 2ꢀSubstituted benzoꢀ
triazole derivatives are used as polymer UVꢀstabilizers.5
The range of chemical reaction of Bt and its derivaꢀ
tives is rather broad and include nucleophilic substitution
reactions,3,6 nucleophilic addition to electronꢀdeficient
multiple bonds,1,6 and elimination of N2 followed by cyclizaꢀ
tion.6,7 Concerning the use of Bt in organic synthesis,
most chemical reactions of both Bt and its derivatives
have been fully described earlier.6
Bt and its derivatives are very well documented in the
literature, however, no works have been published during
the last 15 years on addition reactions of Bt to the πꢀ
electronꢀdeficient olefin bonds in cyclic imides. Thus,
the aim of the present work is synthesis and study of
benzotriazolylsuccinimides based on Bt and maleimides.
The possibility of the reaction of Bt with maleimides
was studied by performing condensation of Bt with
Nꢀphenylmaleimide (PMI) in melt in a fluoroplast cup at
120—220 °C (Scheme 1).
C(3´)H resonates at δ 5.96 (dd, 1 H). Aliphatic protons of
an analog of this compound based on benzimidazole and PMI,
viz., 1ꢀ(2,5ꢀdioxoꢀ1ꢀphenylpyrrolidinꢀ3ꢀyl)benzimidazole,
give similar spectral pattern.8 In the 13C NMR spectrum
(DMSOꢀd6), the signals for aliphatic atoms C(4') and
C(3´) were observed at δ 35.43 and 56.34, respectively,
and two signals for carbonyl atoms C(2') and C(5') at
δ 172.33 and 173.19. These data altogether prove the forꢀ
mation of 3ꢀsubstituted siccinimide.
In the 1H NMR spectrum (CDCl3) of the isolated prodꢀ
uct 1, the protons of the group C(4´)H2 give well resolved
signals at δ 3.67 and 3.85 (both dd, 1 H, Jvic = 18.5 Hz,
Jtrans = 9.61 Hz, Jcis = 5.52 Hz), and the methine proton
The presence of two signals for the aromatic protons in
the 1H NMR spectrum of 1 (DMSOꢀd6) at δ 7.95 and 8.15
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 399—401, February, 2008.
1066ꢀ5285/08/5702ꢀ0409 © 2008 Springer Science+Business Media, Inc.

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Russ.Chem.Bull., Int.Ed., Vol. 57, No. 2, February, 2008
Farion et al.
(both d, 1 H each, H(7), H(4), J = 8.24 Hz, J = 8.55 Hz),
and six signals for the carbon atoms of the benzotriazole
fragment in the 13C NMR spectrum at δ 110.71 (C(7)),
119.72 (C(4)), 124.78 (C(5)), 128.38 (C(6)), 133.09
(C(1a)) and 145.43. (C(3a)) prove the formation of
succinimide with nonsymmetrical benzotriazolꢀ1ꢀyl subꢀ
stituent.
Thus, the data from NMR spectroscopy prove comꢀ
pound 1 to be 1ꢀ(2,5ꢀdioxoꢀ1ꢀphenylpyrrolidinꢀ3ꢀyl)ꢀ
benzotriazole.
compounds with higher molecular masses and lower soluꢀ
bility. Hence, the loss of minor isomers containing
benzotriazolꢀ2ꢀyl fragments could be excluded.
Synthesis of bisꢀderivatives has been performed
according to Scheme 2.
Scheme 2
The choice of reaction conditions is explained by the
proneness of maleimides to anionic homopolymerization
across the olefin bonds and ring opening under classical
Michael conditions in solution in the presence of a base.
We have shown that, in contrast to benzimidazole8, Bt is
not added to the electronꢀdeficient double bond of PMI
under acidic conditions. In addition, synthesis in melt is
environmentally and fireꢀsafe. If the reaction is carried
out in glass reactors (melting at 220 °C), then during 2—4
min a sideꢀreaction of homopolymerization of maleimides
(in the case of bisꢀmaleimides, the formation of crossꢀ
linked polymers) occurs. According to our suggestions,
the homopolymerization of maleimides in this case can
be catalyzed by ≡Si—O–M+ groups on the glass surface.
That is why we have chosen a reactor made of an inert
fluoroplast material.
(Benzotriazolꢀ1ꢀyl)succinimide (Benzotriazolꢀ2ꢀyl)succinimide
fragment
fragment
It is known that the nucleophilic addition1 or subꢀ
stitution9,3b in benzotriazoles leads not only to 1ꢀsubstiꢀ
tuted Bt derivatives, but also to the 2ꢀsubstituted derivaꢀ
tives as minor products. Consequently, the formation of
benzotriazolꢀ2ꢀylꢀsubstituted isomer 2 as a sideꢀproduct
could be expected (see Scheme 1). Indeed, low intensity
signals for aromatic carbon atoms in the 13C NMR specꢀ
trum of symmetrical benzotriazolꢀ2ꢀyl fragment were
observed. Probably, compound 2 has mainly been lost
during purification and crystallization. To prove the posꢀ
sibility of formation of (benzotriazolꢀ2ꢀyl)ꢀsubstituted
succinimides, we have carried out condensation of bisꢀ
derivatives of maleimides under analogous condiꢀ
tions, viz., N,N´ꢀhexamethylenebimaleimide (HMBMI),
N,N´ꢀmethylene(4,4'ꢀdiphenyl)bimaleimide (MDPBMI),
and N,N´ꢀoxido(4,4'ꢀdiphenyl)bimaleimide (ODPBMI).
In this case, fragments of both benzotriazolꢀ1ꢀ and ꢀ2ꢀylꢀ
substituted succinimides would be incorporated into
In the 13C NMR spectra of compounds 3a—c (Table 1),
besides the signals for carbon atoms of (benzotriazolꢀ1ꢀyl)ꢀ
succinimide, there were signals for the (benzotriazolꢀ2ꢀyl)ꢀ
succinimide fragment.
In the 1H NMR spectra of compounds 3a—c, the
integral intensity ratio of C(3')H and C(3'’’)H protons are
equal to 7, 4.5 and 7 respectively, which correspond to
the molar ratio of benzotriazolꢀ1ꢀ and ꢀ2ꢀyl succinimide
fragments in these products.
In addition to this, in the 1H and 13C NMR spectra of
compounds 3a—c signals for residual protons of maleimide
fragments were present as lowꢀintensity peaks at δ 6.97—7.03
(s, 0.08—0.27 H), which is an evidence of incompleteness
of the addition reaction of Bt to the maleimide double
bond. This fact can be explained in terms of reversibility
of the reaction at elevated temperatures.
Table 1. 13C NMR spectroscopic data of benzotriazolꢀ1ꢀ and ꢀ2ꢀylsuccinimide fragments of compounds 1 and 3a—c (DMSOꢀd6)
Comꢀ
pound
δ
C(4´) C(4´´´) C(3´) C(3´´´)
C(7)
C(4)
C(5)
C(6)
C(1a)
C(3a) C(4″) +
+ C(7″)
C(5″) + C(1a″) +
+ C(6″) + C(3a″)
1
35.43
—
56.34
—
110.71 119.72 124.78 128.38 133.09 145.43
—
—
—
3a
3b
3c
35.33 36.16
35.40 36.27
35.13 36.01
55.80 63.40
56.28 63.71
55.72 63.20
110.51 119.69 124.72 128.30 133.17 145.35 118.16
110.67 119.71 124.76 128.37 133.07 145.41 118.20
109.97 119.45 124.13 127.76 133.05 145.32 117.84
127.42
127.51
126.83
144.19
144.21
144.16

Synthesis of benzotriazolylsuccinimides in melt
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 2, February, 2008
411
Compound 3b. Yield 88%. Found (%): C, 64.89; H, 4.13; N,
17.60. C33H24N8O4. Calculated (%): C, 66.44; H, 4.05; N, 18.78.
IR, ν/cm–1: 1721, 1731 (C=N); 2944, 2854 (C—H aliph.); 746
(1,2ꢀPh); 1386 (C—N—C of succinimide).
Compound 3c. Yeild 91%. Found (%): C, 63.46; H, 3.74; N,
17.94. C32H22N8O5. Calculated (%): C, 64.21; H, 3.70; N, 18.72.
IR, ν/cm–1: 1715, 1732 (C=N); 1242 (—O—); 746 (1,2ꢀPh);
1393 (C—N—C of succinimide).
Thus, the conducted experiments allow us to make a
conclusion about two paths of reaction of 1Hꢀbenzotriazole
with maleimides: with formation of both (benzotriazolꢀ1ꢀyl)
and (benzotriazolꢀ2ꢀyl)siccinimides, the latter being minor
products.
Experimental
Fourierꢀtransform IRꢀspectra were recorded with an IFS25
instrument in KBr pellets. 13C and 1H NMR spectra were
obtained on a Varian VXRꢀ500S spectrometer at 126.7 and
500 MHz, respectively, in DMSOꢀd6, CDCl3 and acetoneꢀd6;
the signals of residual protons for DMSOꢀd6 (δ 2.5), CDCl3
(δ 7.24) and acetoneꢀd6 (δ 2.07) in 1H NMR spectra and for
carbon atoms of DMSO (δ 39.7) in 13C NMR spectra served as
internal standard. Melting points were determined on an
IA9100 instrument.
The starting compounds (PMI and Bt) were synthesized
and purified as described earlier;10 DMF, DMSO and benzene
were purified according to the known procedures,11 ethanol and
HCOOH ('chemically pure' grade) were used without additional
purification.
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ture of Bt (1.1913 g, 0.01 mol) and PMI (1.7937 g, 0.01 mol) in
a fluoroplast cup was placed in a preheated to 120 °C bath
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(C—H aliph.).
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g, 0.02 mole) and either HMBMI (2.7629 g, 0.01 mole) (for 3a),
or MDPBMI (3.5835 g, 0.01 mole) (for 3b), or ODPBMI (3.6032 g,
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Received September 11, 2006;
in revised form December 19, 2007