Cyclization of alk-4-ynals with o-diaminoarenes as a selective one-pot synthesis of arylmethylidene-substituted 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazoles and 7,8-dihydro-6H-pyrrolo[1’,2’:1,2]imidazo[4,5-b]pyridines
- Authors: Gvozdev V.D.1, Shavrin K.N.1, Baskir E.G.1, Egorov M.P.1, Nefedov O.M.1
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Affiliations:
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences
- Issue: Vol 65, No 7 (2016)
- Pages: 1829-1838
- Section: Full Articles
- URL: https://journals.rcsi.science/1066-5285/article/view/238607
- DOI: https://doi.org/10.1007/s11172-016-1517-6
- ID: 238607
Cite item
Abstract
A one-pot synthesis of arylmethylidene-substituted 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazoles based on the reaction of alk-4-ynals with 1,2-diaminobenzenes in DMSO at sequential catalysis with NH4Br and bases was suggested. The use in these processes of KOH as a base led to the selective formation of E-isomers of the final products in 48–66% yields, whereas less basic K2CO3 gave the corresponding Z-isomers in 32–82% yields. Similar cyclization reactions involving 2,3-diaminopyridine gave 7,8-dihydro-6H-pyrrolo[1’,2’:1,2]imidazo[4,5-b]pyridines in up to 56% yields. The distinguishing feature of the processes under study is proceeding of their key step that is intramolecular hydroamination of the triple bond, as a 5-exo-dig-cyclization. The necessity for the application of drastic conditions required for these processes is in agreement with the results of quantum chemical calculations of PES of their most probable rate-determining step, namely, the cyclization of the corresponding benzimidazolide anions to cyclic vinyl anions.
About the authors
V. D. Gvozdev
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences
Author for correspondence.
Email: vgvozdev2006@yandex.ru
Russian Federation, 47 Leninsky prosp., Moscow, 119991
K. N. Shavrin
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences
Email: vgvozdev2006@yandex.ru
Russian Federation, 47 Leninsky prosp., Moscow, 119991
E. G. Baskir
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences
Email: vgvozdev2006@yandex.ru
Russian Federation, 47 Leninsky prosp., Moscow, 119991
M. P. Egorov
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences
Email: vgvozdev2006@yandex.ru
Russian Federation, 47 Leninsky prosp., Moscow, 119991
O. M. Nefedov
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences
Email: vgvozdev2006@yandex.ru
Russian Federation, 47 Leninsky prosp., Moscow, 119991