Über arylierte Pyridine und ihre Beziehungen zu den entsprechenden Pyryliumverbindungen. II

Abstract

Wahrend die aliphatischen Abkommlinge des Pyridins in groBer Mannigfaltigkeit bekannt und untersucht sind, ist dies bei den rein aromatischen Vertretern, insbesondere denjenigen, deren Phenylreste Substituenten tragen, nicht der Fall. Das hat seinen Grund darin, daB die Methoden, welche leicht zu aliphatischen Aminen fuhren, in der aromatischen Reihe entweder ganz versagen oder nur geringe Ausbeuten liefern. Als sich nun der von Baeyer und P i c c a r d 2) an aliphatischen

Solvent‐free synthesis of new 2,4,6‐triarylpyridines catalyzed by a Brønsted acidic ionic liquid as a green and reusable catalyst

“…Owing to their wide range of pharmacological activity and industrial and synthesis applications, a number of methods have been reported for the synthesis of Kröhnke‐type pyridines [7]. Previously, 2,4,6‐triarylpyridines have been prepared by the condensation of 1,5‐diketones with formamide‐formic acid [8] and by other synthetic procedures including the Chichibabin method [9–12]. Following this procedure, the yields of single products are low because of the formation of mixtures of pyridines and various by‐products [12].…”

Barium Chloride Dispersed on Silica Gel Nanoparticles: An Efficient Catalyst for the Preparation of 2,4,6-Triarylpyridines under Solvent-Free Conditions

“…Despite their importance from a pharmacological and synthetic point of view, comparatively few methods for the preparation of 2,4,6-triarylpyridines (commonly named as Krohnke pyridines) have been reported in the literature. [4][5][6][7][8][9] New amongst these methods is the cyclo-condensation reaction of acetophenones, benzaldehydes and NH 4 OAc using conventional heating in the presence of Brønsted and Lewis acid catalysts. [10][11][12][13] The overall aim of this study was to develop and validate an efficient protocol for the synthesis and easy purification of 2,4,6-triarylpyridines from the cyclo-condensation reaction of acetophenones, benzaldehydes and NH 4 OAc in the presence of BaCl 2 -nano SiO 2 as an efficient catalyst (Scheme 1).…”