On the nucleophilic accession of 1H-benzotriazole to maleimides Текст научной статьи по специальности «Химические науки»

ХИМИЧЕСКИЕ НАУКИ/ CHEMICAL SCIENCES Оригинальная статья / Original article УДК 541.64:542.954

DOI: http://dx.doi.org/10.21285/2227-2925-2019-9-1 -6-12

On the nucleophilic accession of 1H-benzotriazole to maleimides

© Dmitry M. Mognonov*, Ivan A. Farion*, Oksana Zh. Ayurova*, Olga V. Ilyina*, Mikhail E. Zayakhanov**, Alexander V. Bituev**

* Baikal Institute of Nature Management (BINM) of SB RAS Ulan-Ude, Republic of Buryatia, Russian Federation

** East Siberian State University of Technology and Management Ulan-Ude, Republic of Buryatia, Russian Federation

Abstract: According to the quantum chemical calculations of N-phenylmaleimide (PMI) using the LCAO MO method in Hückel п-electron approximation, a maximum deficit of п-electrons is observed on carbonyl carbon atoms; subsequently, a nucleophilic attack of "pyridinic" nitrogen atoms on carbonyl carbon is likely to occur. Moreover, an alternative attack on olefinic atoms with the opening of a multiple bond is possible. Since the nitrogen atoms N1 and N3 are equivalent in nucleophilic reactions of 1H-benzotriazole (BT) and taking the spectroscopic data on the BT adduct into account, it is impossible to conclude that all three nitrogen atoms are involved. For these purposes, it is advisable to use benzotriazoles with substitution in position 5 (or 6), where the nitrogen atoms N1 and N3 are not equivalent in these reactions. The reaction products were analysed us-

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ing the С NMR-spectroscopy method. The obtained data testify to the preferential occurrence of the nucleophilic attack of benzotriazoles on the multiple maleimide bond during their interaction in the melt at elevated temperatures, as well as on the participation of all three nitrogen atoms of the 1H-benzotriazolyl fragment in the nucleophilic attachment of benzotriazoles to the multiple PMI bond.

Keywords: 1H-benzotriazole, N-phenylmaleimide, nucleophilic addition, methylene bis-(benzotriazolyl succin-imide), nuclear magnetic resonance

Information about the article: Received August 15, 2018; accepted for publication March 4, 2019; available online March 29, 2019.

For citation: Mognonov D.M., Farion I.A., Ayurova O.Zh., Ilina O.V., Zayakhanov M.E., Bituev A.V. On nucleophilic addition of 1H-benzotriazole to maleimides. Izvestiya Vuzov. Prikladnaya Khimiya i Biotekhnologiya [Proceedings of Universities. Applied Chemistry and Biotechnology]. 2018, vol. 9, no. 1, pp. 6-12. (In Russian). DOI: 10.21285/2227-2925-2019-9-1-6-12.

О нуклеофильном присоединении 1Н-бензотриазола к малеимидам

© Д.М. Могнонов*, И.А. Фарион*, О.Ж. Аюрова*, О.В. Ильина*, М.Е. Заяханов**, А.В. Битуев**

* Байкальский институт пиродопользования СО РАН,

г. Улан-Удэ, Республика Бурятия, Российская Федерация

** Восточно-Сибирский государственный университет технологий и управления, г. Улан-Удэ, Республика Бурятия, Российская Федерация

Резюме: Согласно квантовохимическим расчетам N-фенилмалеимида (ФМИ) методом МО ЛКАО в п-электронном приближении Хюккеля на карбонильных атомах углерода наблюдается максимальный дефицит п-электронов, поэтому вероятна нуклеофильная атака «пиридиновых» атомов азота на карбонильный углерод ФМИ. Возможен альтернативный вариант атаки на олефиновые атомы с раскрытием кратной связи. Поскольку в нуклеофильных реакциях 1Н-бензотриазола (БТ) атомы азота N1 и N3 эквивалентны, сделать вывод об участии всех трех атомов азота на основании спектроскопических данных продуктов присоединения БТ невозможно. Для этих целей целесооб-

разно использовать замещенные в положение 5 (или 6) бензотриазолы, где атомы азота N1 и N3 не являются эквивалентными в данных реакциях. Продукты реакции исследовали методом ЯМР 13С спектроскопии. Полученные данные свидетельствуют о преимущественном протекании нуклео-фильной атаки бензотриазолов на кратную связь малеимидов при их взаимодействии в расплаве при повышенных температурах, а также об участии в нуклеофильном присоединении бензотриазолов к кратной связи ФМИ всех трех атомов азота 1Н-бензотриазолильного фрагмента. Ключевые слова: 1Н-бензотриазол, Nфенилмалеимид, нуклеофильное присоединение, метилен-бис-(бензотриазолилсукциниимид), ядерно-магнитный резонанс

Информация о статье: Дата поступления 15 августа 2018 г.; дата принятия к печати 4 марта 2019 г.; дата онлайн-размещения 29 марта 2019 г.

Для цитирования: Могнонов Д.М., Фарион И.А., Аюрова О.Ж., Ильина О.В., Заяханов М.Е., Битуев А.В. О нуклеофильном присоединении 1Н-бензотриазола к малеимидам // Известия вузов. Прикладная химия и биотехнология. 2019. Т. 9, N 1. С. 6-12. DOI: 10.21285/2227-2925-2019-9-1-6-12.

INTRODUCTION

Currently, polymeric matrices based on bis-maleimides (BMI) appear to be promising approaches for creating heat-resistant and durable materials for special purposes [1-3]. For the synthesis of these matrices, bis-imides of unsaturated acids and nucleophilic monomers are mainly applied with in-melt heating having a molar excess of BMI [4].

Previously, synthesis of heat-resistant oligomers was carried out based on biomedical technology and bis-benzimidazoles [5-9] or bis-(1H-ben-zotriazoles) [10, 11]. In this connection, the greatest attention was paid to the study of the thermal properties of the original matrices and the mechanical characteristics of the final press materials. Although the obtained thermosetting oligomers are well-soluble and have low viscosity, the large number of different maleimide groups makes it difficult to identify benzotriazolyl succinimide fragments using the NMR method.

The aim of this work consists in a study of the fragments formed upon the nucleophilic addition of benzotriazoles to maleimides formed by Michael reactions in the melt.

EXPERIMENTAL PART

IR spectra were recorded on an ALPHA spectrometer (Bruker) in the range of wave numbers 4000-400 cm- . Samples were obtained by extrusion with KBr. Elemental analysis was performed by EA-3028 CHNS-analyser (Eurovector).

13 1

C and H NMR spectra were obtained by Varian VXR-500S spectrometer at 126.7 and 500 MHz, respectively, in DMSO-d6 and CDCl3; the residual proton signals for DMSO-d6 and CDCl3 were 5 = 2,5 ppm and 5 = 7,24 ppm, respectively. 1H-benzotriazole was synthesised according to the method presented in collection [12] at a melting temperature of Tmp= 88-89 °C.

N-phenyl maleimide (PMI) in the form of a bright yellow powder was synthesised from maleic anhydride and aniline, followed by cyclisation of the resulting amic acid with acetic anhydride in the presence of a catalyst. The PMI purified by recrystallization

from isopropyl alcohol was characterised by a melting temperature of Tmp= 89-90 °C (according to the reference data, Tmp= 85-87 °C1).

5,5- bisbenzotriazolmethane. To a 500 mL flask equipped with a stirrer, argon inlet and outlet and a thermometer, an ice-cold mixture of CH3COOH (110 mL) and distilled water (55 mL) was added, followed by 3,3',4,4'-tetraamino-diphenylmethane (22 g; 0,0964 mol). The contents of the flask were heated until complete dissolution of the solids. The solution was cooled to the temperature of 13-14 °C. After that, the solution of NaNO2 (18 g; 0,261 mol) in distilled water (40 mL) was quickly added to the flask with vigorous stirring. The temperature of the flask contents increased to 60-70 °C. The contents were stirred for 1 h. The resulting suspension was poured into cold distilled water (500-600 mL). Then, the product was filtered, washed with distilled water and dried in vacuum at the temperature of 50-60 °C. The resulting 5,5'-bisbenzotriazolmethane was recrys-tallised from CH3COOH with charcoal and dried in vacuum at 70-80 °C. The final product yielded in 19,02 g (85%) and was characterised as follows Tmp=240-241 °C; 1H NMR (DMSO-d6), 5 4,29 (s, 2H, CH2), 7,34-7,42 (d,J= 19,5 Hz, 2H, phenylprotons), 7,78 (s, 2H, phenylprotons), 7,81-7,89 (d,J=19,5 Hz, 2H, phenylprotons), 15,46 ppm.

IR spectroscopy: CH2 1400, 3070, 2950, NH 3333-3400 cm-1.

Elemental analysis. Calculated for C13H10N6, %: C - 62,39; H - 4,03; N - 33,58. Determined, %: C - 62,15; H - 3,90; N - 33,16.

RESULTS AND DISCUSSION

According to quantum chemical calculations of PMI using the LCAO MO method in n-Huckel electronic approximation (parameters: 5N= 1,5; 5O= 1,0; 5C (carbonyi)= 0,25), the maximum deficit of n-electrons is observed on carbonyl carbon atoms.

1

Aldrich Catalogue Handbook of Fine Chemicals, 1992-1993.

Therefore, with charge control, a nucleophilic attack of the 1,2,3-benzotriazole (pyridine) nitrogen atoms on the PMI carbonyl carbon is possible (Fig. 1).

Since the formation of n-lowest vacant molecular orbitals (n-HBMO) of PMI also involves olefinic carbons, an alternative variant of attack on these atoms (orbital control) with the opening of a multiple bond is possible.

The possible directions of interaction of BT with PMI are presented in Scheme 1.

A variant of nucleophilic attack on carbonyl carbon atoms in the absence of a polar solvating medium and hydrogen bond donors is unlikely due to negative charge in the intermediate tetrahedral intermediate being concentrated on oxygen and not stabilised by effective solvation and hydrogen bonds (see Figure 1, reaction 1).

In the case of an alternative attack on the ole-finic bond, the resulting anion is stabilised due to the delocalisation between carbonyl oxygen and carbon (see Scheme 1, reaction 2). In this case, the lack of effective solvation is compensated for by the delocalisation of the charge, which determines the preferential direction of the BT nucleo-philic attack on a multiple bond.

Furthermore, in the reaction products of BT with bis-maleimides, in addition to the peaks of the

main 1-substituted nitrogen atoms of benzotriazolyl succinimides, there are also resonant peaks of protons and carbon atoms of the minor 2-sub-stituted benzotriazolyl succinimides. The formation of a smaller quantity of these products can be explained by the lower aromaticity of 2-substituted BTs and their participation in the stabilisation of a positive charge in the intermediate of n-electrons of the benzene ring. The interaction of the nitrogen atom of BT with a multiple bond of PMI is presented in Scheme 2.

Since the nitrogen atoms N1 and N3 are equivalent in nucleophilic reactions of BT, it is impossible to conclude on the basis of the spectroscopic data on the BT adduct that all three nitrogen atoms are involved. For these purposes, it is advisable to use benzotriazoles substituted in position 5 (or 6), where the nitrogen atoms N1 and N3 are not equivalent in these reactions. In order to study the possibility of participation of all three benzotriazole nitrogen atoms in the nucleophilic addition of maleimides, methylene bis- (benzotriazolyl succinimides) were synthesised in the melt at 120-220 °С according to Scheme 3.

The reaction product was investigated by

13

NMR С-spectroscopy; the results are presented in Fig. 2-4.

1,450

о

V 1,619 с

~N\

о

1,41550

0,776 0,930 0,930 0,776

Fig. 1. Density of п-electrons at the atoms of the maleimide cycle in PMI Рис. 1. п-электронные плотности на атомах малеимидного цикла в ФМИ

Scheme 1 Схема 1

Scheme 2 Схема 2

Scheme 3 Схема 3

H2

Scheme 4 Схема 4

Fig. 2. Carbonyl region in the spectrum of compounds I and II Рис. 2. Карбонильная область спектра соединений I и II

Fig. 3. Methine carbon peaks of Compounds I and II Рис. 3. Пики метиновых углеродов соединений I и II ХИМИЧЕСКИЕ НАУКИ

H2C

Fig. 4. Methylene carbon peaks of Compounds I and II

Рис. 4. Пики метиленовых углеродов соединений I и II

For comparison, similar peaks are given on a smaller scale presenting the adduct of two moles of BT to 4,4/-diphenylmethane-bis-maleimide or compound II (Scheme 4), where the intense peaks corresponding to the carbon of the main 1-benzotriazolyl-substituted succinimide are not split.

In the carbonyl region of the spectrum (see Fig. 2), a pair of closely spaced intense carbon peaks (172,26 and 172,32; 173,13 and 173,15 ppm) of

1- and 3-benzotriazolyl substituted succinimide fragments are observed. At the same time, at 8 equal to 171,39 and 173,22 ppm, low-intensity unsplit peaks correspond to 2-benzotriazolyl-substituted succin-imide fragment. The absence of splitness can in this case be explained by the symmetric nature of the

2-benzotriazolyl fragment. The presence of three peaks of the adducts of bis-benzotriazolmethane (BBTM) to PMI is also confirmed by the presence of three resonant peaks of methine (see Fig. 3) and

methylene (see Fig. 4) carbons of benzotriazolyl succinimide fragments. In this case, as with carbonyl carbons, the most intense closely spaced peaks correspond to 1- and 3-ben-zotriazolyl-substituted succinimide fragments. At the same time, small differences in the intensity of these peaks indicate the almost equal probability of the addition of substituted nitrogen atoms to the maleimides in the 1- and 3-benzo-triazoles positions.

CONCLUSIONS

Thus, on the basis of the conducted studies, the nucleophilic attack of benzotriazoles can be concluded to preferentially proceed on the multiple bond of maleimides during the interaction in the melt at elevated temperatures. In addition, all three nitrogen atoms of the 1H-benzotriazolyl fragment participate in the nucleophilic addition of benzotri-azoles to a multiple bond of PMI.

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11. Farion I.A., Mognonov D.M., Burdukovskii V.F., Kholkhoev B.Ch., Timashev P.S. Convenient One-Step Synthesis of Benzotriazolylsuccinimides in Melt. Journal of Heterocyclic Chemistry. 2017, vol. 54, no. 2, pp. 844-849.

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Contribution

Dmitry M. Mognonov, Ivan A. Farion, Oksana Zh. Ayurova, Olga V. Ilyina, Mikhail E. Zayakhanov, Alexander V. Bituev carried out the experimental work, on the basis of the results summarized the material and wrote the manuscript. Dmitry M. Mognonov, Ivan A. Farion, Oksana Zh. Ayurova, Olga V. Ilyina, Mikhail E. Zayakhanov, Alexander V. Bituev have equal author's rights and bear equal responsibility for plagiarism.

Conflict of interests

The authors declare no conflict of interests regarding the publication of this article.

Критерии авторства

Могнонов Д.М., Фарион И.А., Аюрова О.Ж., Ильина О.В., Заяханов М.Е., Битуев А.В. выполнили экспериментальную работу, на основании полученных результатов провели обобщение и написали рукопись. Могнонов Д.М., Фарион И.А., Аюрова О.Ж., Ильина О.В., Заяханов М.Е., Битуев А.В. имеют на статью равные авторские права и несут равную ответственность за плагиат.

Конфликт интересов

Авторы заявляют об отсутствии конфликта интересов.

AUTHORS' INDEX

Dmitry M. Mognonov IS)

Chief Researcher

Baikal Institute of Nature Management SB RAS e-mail: dmog@binm.ru

Ivan A. Farion

Researcher

Baikal Institute of Nature Management SB RAS e-mail: ifar@mail.ru

Oksana Zh. Ayurova

Researcher

Baikal Institute of Nature Management SB RAS e-mail: chem88@mail.ru

Olga V. Ilyina

Leading Engineer

Baikal Institute of Nature Management SB RAS e-mail: olil2@yandex.ru

Mikhail E. Zayakhanov

Professor

East Siberian State University of Technology and Management e-mail: psmi88@mail.ru

Alexander V. Bituev

Professor

East Siberian State University of Technology and Management e-mail: psmi88@mail.ru

СВЕДЕНИЯ ОБ АВТОРАХ

Могнонов Дмитрий Маркович IS ,

главный научный сотрудник Байкальский институт природопользования СО РАН e-mail: dmog@binm.ru

Фарион Иван Александрович,

научный сотрудник Байкальский институт природопользования СО РАН e-mail: ifar@mail.ru

Аюрова Оксана Жимбеевна,

научный сотрудник Байкальский институт природопользования СО РАН e-mail: chem88@mail.ru

Ильина Ольга Васильевна,

ведущий инженер Байкальский институт природопользования СО РАН e-mail: olil2@yandex.ru

Заяханов Михаил Егорович,

профессор

Восточно-Сибирский государственный университет технологий и управления e-mail: psmi88@mail.ru

Битуев Александр Васильевич,

профессор

Восточно-Сибирский государственный университет технологий и управления e-mail: psmi88@mail.ru