Estudio de reacciones de acoplamiento en [1,2,3]triazolo[1,5-a]piridinas. Ariltriazolopiridinas.

Abstract

1. Biaromatic fluorophores have been exploited in several analytical applications. Heterobiaryls have important biological properties and the biaryl unit is represented in several types of compounds of current interest including natural products, polymers, advanced materials, liquid crystals, luminescent molecular chemosensors, and molecules of medicinal interest. The architecture of p-conjugated heteroaromatic compounds assumes significance in view of the applications of these compounds. Recently, we have obtained a sensor of cations and anions based on the fluorogenic properties of a terheteroaryl system in which the [1,2,3]triazolo[1,5-a]pyridine nucleus is present. Nevertheless the fluorescence properties of [1,2,3]triazolo[1,5-a]pyridines have been scarcely studied. Two series of compounds, 3-aryl- and 3-methyl-7-aryl-[1,2,3]triazolo[1,5-a]pyridines have been synthesized by Suzuki cross-coupling reactions. All compounds obtained are fluorescents. 2. We describe the first deprotonation¿Celectrophilic trapping sequences using magnesates. The preparation of functional heterocycles is an important synthetic goal because of the multiple applications of these molecules. Among the methods developed, lithiation is convenient to allow a number of polyfunctional azine (pyridines, quinolines,. . .) and diazine syntheses since lithiated derivatives display a high reactivity towards many electrophilic functions. Nevertheless, this methodology often requires low temperatures, which can be difficult to realize on an industrial scale. Herein, we describe the synthesis and reactivity of lithium arylmagnesates through the regioselective deprotonation of aromatic compounds using lithium magnesates. The main advantage of this methodology is the relative stability of the organometallic species formed. 3. An experimental (1H NMR) and theoretical (DFT) study of the ring¿Cchain¿Cring isomerization of 3-(2-pyridyl)-[1,2,3]triazolo[1,5-a]pyrid-7-yl derivatives (A) into 6-{[1,2,3]triazolo[1,5-a]pyrid-3-yl}-2-pyridyl derivatives (B) has been carried out. Based on the calculations, a mechanism of several steps will be proposed. The experimental results as well as the calculations lead to the conclusion that the A¿CB ratio depends on the electronic properties of the substituents.