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ISSN 1998-9539

Synthesis of Benzihemiporphyrazine Bearing tert-Butylquinoxaline[2,3-c]pyrrole Fragments

Svetlana V. Alekseeva, Alexandra S. Kuznetsova,@1 Oscar I. Koifman, and Mikhail K. Islyaikin@2
Dedicated to Academician Aslan Yusupovich Tsivadze on the occasion of his 75-th birthday
IRLoN, Research Institute of Macroheterocycles, Ivanovo State University of Chemistry and Technology, 153000 Ivanovo, Russia
@1Corresponding author E-mail: kuznetsova.alex.91@gmail.com
@2Corresponding author E-mail: islyaikin@isuct.ru
 
DOI: 10.6060/mhc170724k
Macroheterocycles 2017 10(4-5) 543-547
 
A new representative macroheterocyclic compound of the ABAB-type was synthesized by crossover-condensation of m-phenylenediamine and 6-tert-butylquinoxaline-2,3-dicarbonitrile by refluxing in fresh distillated BuOH. The crude product was washed by hot hexane and purified by column chromatography on silica gel using an eluent mixture comprised of methylene chloride:methanol:hexane. Solvents were then evaporated and orange powder was dried at reduced pressure. The obtained substance was characterized by UV-Vis, IR, 1H NMR spectroscopy and mass-spectrometry data. The signal located at 655.5 Da which corresponds to [M+H]+  ions was detected in MALDI-TOF (without matrix). Using of α-cyano-4-hydroxycinnamic acid (CHCA) as matrix induces the appearance of a reduced form of the macrocycle which is detected by a signal at 656 Da [M+2H]+. The structures of two regioisomers with different positions of tert-butyl groups in pyrroloquinoxaline fragments were optimized at DFT/B3LYP/6-31G(d,p) level. It was predicted that both isomers have nonplanar saddle-shape structures and that the cis-isomer was found to be of 0.75 kcal/mol more stable than alternative regioisomer. The positive values of NICS calculated at the centers of molecules confirm the nonaromatic character of their macrorings.

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