3‐(Pyridin‐2‐yl)[1,2,3]triazolo[1,5‐a]quinoline: A Theoretical and Experimental Analysis of Ring‐Chain Isomerisation

Abstract

In the course of the synthesis of new fluorophores for molecular recognition an experimental (1H NMR) and theoretical (DFT) study of the ring‐chain isomerism of 3‐(pyridin‐2‐yl)[1,2,3]triazolo[1,5‐a]quinoline derivatives (A) into 2‐([1,2,3]triazolo[1,5‐a]pyridin‐3‐yl)quinoline derivatives (B) has been carried out. The rearrangement is influenced by steric and electronic effects of the substituents present on the quinoline ring. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

The trans–cis and the azide–tetrazole ring-chain isomerization of 2-azido-1,3-azoles: Quantum chemical study

“…Nevertheless, the ring-chain isomer equilibrium between isomeric azido and tetrazole species strongly depends on the nature of atom X, on the type and position of substituent groups on the 1,3-azole ring, on the temperature and, on the polarity of the solvent. Knowledge of the relative stabilities of isomers of heterocyclic as well as the conversion from one isomer to another is important from the point of view of structural chemistry [23][24][25][26][27][28][29][30][31].…”

Unusual phosphine oxidation: new triazolopyridyl-quinolyl phosphine oxide fluorescent dyes

“…[7][8][9] However, any of our previous triazolopyridyl phosphine derivatives gave signicant emission. 14 Therefore, we studied the uorescence properties of these novel compounds.…”

“…These systems are in equilibrium with a diazo compound (see Scheme 1). 6,7 When substituted at position C3 with a pyridyl ring (R ¼ 2-pyridyl), the intermediate diazo compound can undergo cyclization to the ve membered ring system via two possible nitrogen atoms giving the equilibria 1 % 3 or 2 % 4, respectively (Scheme 1). This equilibrium, known as ring-chain isomerization, is controlled by the different substituents (X), either by electronic effects in compound 1, 6 or electronic and steric effects in compound 2.…”

“…6,7 When substituted at position C3 with a pyridyl ring (R ¼ 2-pyridyl), the intermediate diazo compound can undergo cyclization to the ve membered ring system via two possible nitrogen atoms giving the equilibria 1 % 3 or 2 % 4, respectively (Scheme 1). 7 In the framework of our work on triazolopyridines and quinolines we have studied several applications based on this particular and intriguing ring-chain isomerization including the preparation of uorescent dyes, 8 tridentate ligands, 9 and phosphines based on scaffold 1 (X ¼ PPh 2 , PCy 2 , P i Pr 2 .) 7 In the framework of our work on triazolopyridines and quinolines we have studied several applications based on this particular and intriguing ring-chain isomerization including the preparation of uorescent dyes, 8 tridentate ligands, 9 and phosphines based on scaffold 1 (X ¼ PPh 2 , PCy 2 , P i Pr 2 .)…”

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3-(2-Pyridyl)-[1,2,3]triazolo[1,5-a]quinolylphosphines

suffer an unusual phosphine oxidation due to their special geometry that allows a s-donation of the nitrogen (N1) lone pair to phosphorus. 7 In the framework of our work on triazolopyridines and quinolines we have studied several applications based on this particular and intriguing ring-chain isomerization including the preparation of uorescent dyes, 8 tridentate ligands, 9 and phosphines based on scaffold 1 (X ¼ PPh 2 , PCy 2 , P i Pr 2 .) 1).

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