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. 2021 Sep 20;26(18):5692.
doi: 10.3390/molecules26185692.

Electrophilically Activated Nitroalkanes in Double Annulation of [1,2,4]Triazolo[4,3- a]quinolines and 1,3,4-Oxadiazole Rings

Alexander V Aksenov  1 , Nikita K Kirilov  1 , Nicolai A Aksenov  1 , Dmitrii A Aksenov  1 , Elena A Sorokina  2 , Carolyn Lower  3 , Michael Rubin  1   3
Affiliations

Electrophilically Activated Nitroalkanes in Double Annulation of [1,2,4]Triazolo[4,3- a]quinolines and 1,3,4-Oxadiazole Rings

Alexander V Aksenov et al. Molecules. .

Abstract

Nitroalkanes activated with polyphosphoric acid could serve as efficient electrophiles in reactions with amines and hydrazines, enabling various cascade transformations toward heterocyclic systems. This strategy was developed for an innovative synthetic protocol employing simultaneous or sequential annulation of two different heterocyclic cores, affording [1,2,4]triazolo[4,3-a]quinolines with 1,3,4-oxadiazole substituents.

Keywords: annulation; cascade transformations; heterocycles; nitroalkanes.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Scheme 1
Scheme 1
Electrophilic activation of nitroalkanes in synthesis of heterocycles.
Scheme 2
Scheme 2
Preparation of [1,2,4]triazolo[4,3-a]quinolines with 1,3,4-oxadiazole rings.
Scheme 3
Scheme 3
Mechanistic rationale involving electrophilic nitroalkanes.
Scheme 4
Scheme 4
Mechanistic rationale involving electrophilic nitroacetophenones.
Scheme 5
Scheme 5
Stepwise installation of[1,2,4]triazolo[4,3-a]quinolines and 1,3,4-oxadiazole moieties.
Figure 1
Figure 1
ORTEP drawing of X-ray structures of (2-ethyl-5-(3-ethyl-[1,2,4]triazolo[4,3-a]pyridin-6-yl)-1,3,4-oxadiazole) (3ba, CCDC #2092596) and 1-(5-ethyl-1,3,4-oxadiazol-2-yl)[1,2,4]triazolo[4,3-a]quinoline (12a, CCDC #2093198). The thermal ellipsoids are shown at 50% probability.
See this image and copyright information in PMC

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