Synthesis, structure, and electrochemical properties of 12,42-dioxo-21,31-diphenyl-7,10,13-trioxa-1,4(3,1)-diquinoxalina-2(2,3),3(3,2)-diindolizinacyclopentadecaphane

Abstract

The oxidative dehydrocyclization of the 3 (indolizin 2´ yl) 2 oxoquinoxaline monopodand performed either electrochemically or under the action of molecular iodine affords new redox active heterocyclophane consisting of the redox switchable biindolizine fragment combined with the polyether bridged π deficient quinoxaline systems. The single crystal X ray diffrac tion study showed that the trioxaundecane chain of heterocyclophane adopts an extended conformation, and one of the phenyl substituents of the molecule closes the pseudocavity formed by the spacer from one of the sides. The cyclic voltammetric study of heterocyclophane in MeCN and DMF showed the three step oxidation of the indolizine fragments accompanied by the single electron transfer in each step. The first and third steps are reversible, and the second step is irreversible. The oxidation at potentials of the first peak gives rise to stable radical cations detected by the ESR method (g = 2.0024, a 2N = 0.26 mT).In recent years, the synthesis of macrocyclic com pounds, which can reversibly respond to external actions (thermal, photochemical, electrochemical, pH, etc.) by changing important properties and characteristics (the cavity size, the surface shape, the electronic structure, the complexing ability, etc.) due to the specially introduced functional groups or fragments, has taken a special place in supramolecular chemistry. 1 Such "sensitive" hetero cyclophanes containing redox active biindolizine systems can serve as molecular switches 2 and membrane carriers 3 and are of great interest in the design of new sensors for modern technologies based on molecular processes. Un like redox active compounds (ferrocenes, 4,5 tetrathia fulvalenes, 6,7 and quaternized 4,4´ bipyridines 8,9 ), bi indolizines have found little use as active regions, which make cyclophanes able to respond to external actions, in spite of the fact that biindolizines are quite stable two step redox systems, whose electrochemical behavior has been studied in sufficient detail. 10-15Indolizines are π rich compounds, which are readily oxidized (~0.2-0.3 V relative to Fc 0/+ ) to form radical cations. 10-14 The stability and subsequent transforma tions of radical cations are determined primarily by the presence of hydrogen atoms in the pyrrole ring of the indolizine system. The radical cations and dications of 3,3´ biindolizines, in which all hydrogen atoms in the five membered ring are replaced by alkyl or aryl groups, are quite stable and can be isolated and characterized as perchlorates. 12 The electrochemical behavior of two dia stereomers of macrocyclic biindolizines, in which both heterofragments are linked at positions 3,3´ and, through a bridge, at positions 1,1´, is different. 13 Thus, the diaste reomer having the anti configuration is oxidized to form stable radical cations and dications, whereas the oxida tion of the diastereomer having the syn configuration is followed by the intramolecular cyclization with the in volvement of the C(5) and C(5´) atoms of the pyridine rings of...

Macrocycles, derivatives of nitrogen-containing heterocycles 3. Synthesis of di(imidazo[1,5-a]quinoxalina)-2(1,3)-benzadithiacycloalkaphanes

“…The formation of the latter is confirmed by the presence of the peaks for the MH + 48 We have chosen molecular iodine successfully used in oxidation of indolisines to biindolisines. 49 The use of mo lecular iodine as the oxidant for mercaptanes, as a rule, requires presence of a base to combine with the liberated hydrogen iodide, which is a strong reducing agent. How ever, the presence in bisthiols 14 of the "pyridine" nitrogen atom allowed us to carry out this reaction without using the base.…”

Synthesis, Electrochemical and Mass Spectrometric Properties of the Macrocycles with One, Two and Four 3,3´-Biindolizine Redox-Active Fragments on the 3-(Indolizin-2-yl)quinoxalin-2-one Platform

“…[13,14] Это метод был успешно применен для полу-чения индолизиновых макроциклов, [13][14][15][16] для которых характерно редокс-переключаемое связывание некото-рых катионов. [25][26][27][28] В настоящей работе разработан метод получения макроциклов, содержащих 2 n хиноксалиноно-вых и индолизиновых структурных единиц в составе ма-кроциклического остова, показана универсальность вы-шеупомянутого метода трансформации индолизин  би-индолизин распространением его на замыкание в макро-цикл индолизиновых подандов с длинными спейсерами, изучены электрохимические и масс-спектрометрические свойства макроциклов.…”

“…[13,15] Исследуемые соединения 3, 5 отличаются спейсером: оксаэтиленовые фрагменты заменены на алифатическую углеводород-ную цепочку, а в соединении 5 присутствуют два редокс-активных бииндолизиновых фрагмента. Замена спейсе-ра приводит к снижению растворимости соединений 3, 5, а тем более соединений 7, 9, и в CH 3 CN, и в ДМФА; их растворимость не позволила достичь концентраций растворов, необходимых для вольтамперометрических измерений.…”

“…[13,15] На ЦВА-кривых, снятых на стеклоуглеродном электроде в среде CH 2 Cl 2 /0.1 M Bu 4 NBF 4 , фиксируется три одноэлектрон-ных диффузионно контролируемых пика окисления бииндолизинового фрагмента при тех же потенциалах (Рисунок 4, Таблица 2), что и для ранее изученных ге-тероциклофанов. [13,15] Первый и третий пики обратимы, а второй необратим.…”

“…Среди индолизиновых макроциклов, кроме син-тезированных в наших работах, [13][14][15][16] известны ма-кроциклы с одним индолизиновым [17,18] и двумя [19][20][21][22] индолизиновыми (бииндолизиновым) фрагментами. Последние, благодаря редокс-активному фрагменту, относятся к макроциклическим соединениям, способ-ным обратимо реагировать на внешние воздействия.…”