Kröhnke pyridines: an efficient solvent-free synthesis of 2,4,6-triarylpyridines

Silica Sulfuric Acid as a Efficient and Recyclable Solid Acid Catalyst for the One-Pot Synthesis of 2,4,6-Triaylpyridines Under Solvent Free Conditions

“…The catalyst was filtrated and the filtrate was concentrated to give the solid product that was washed with water, and recrystallized from n-hexane to give pure products 4a-f. The structure of the products were confirmed by 1 H NMR, IR spectroscopy, and comparison with authentic samples prepared by reported methods 12,20 .…”

“…The general method for synthesis of 2,4,6-triarylpyridines (krohke pyridine) involves the reaction of N-phenacylpyridinium salts with α-ϖ-unsaturated ketones in the presence of ammonium acetate 10,11 . Many procedures have been developed for the synthesis of 2,4,6-triarylpyridines, which include solvent-free reaction of chalcones with ammonium acetate 12 , reaction of α-ketoketene dithioacetals with methyl ketones in the presence of ammonium acetate 13,14 , reaction of Nphosphinylethanimines with aldehydes 15 , solventfree reaction between acetophenones, benzaldehydes, and ammonium acetate in the presence of various catalyst, for example HClO 4 -SiO 2 16 , sodium hydroxide 17 , I 2 18 , preyssler type hetero polyacid 19 and ionic liquid 20 . However most of the traditional processes suffer from a variety of disadvantages, such as pollution, high cost, excess reagents, prolonged reaction times, and harsh reaction conditions.…”

Montmorillonite K10 Clay Catalyzed One Pot Synthesis of 2,4,6-Tri Substituted Pyridine under Solvent Free Condition

“…The mechanism of triaryl pyridine synthesis is as shown in Scheme 2 [25]. First step involves the conden- 4 OAc is as nitrogen source and acetic acid is formed as by-product, the reaction is catalysed by acid, the presence of acetic acid increases the acidity of the medium.…”

One-pot multicomponent synthesis of substituted 5,7-dihydro-1,6-naphthyridines and 5,6,7,8-tetrahydroquinolines

“…The pyridines with the same aryl groups at 2,6-positions are usually prepared in moderate yields by refluxing the three component mixtures in suitable solvent for several hours. Several new improvements to these procedures have been developed including solvent free reaction conditions [18,19], reaction in aqueous media, [20] one-pot procedure under microwave irradiation [21,22] and direct heating α,β-unsaturated ketones and ammonium acetate in the presence of a catalyst amount of acetic acid [23]. Recently, we found that the onepot condensation reaction of aromatic aldehyde and cyclic ketone with N-phenacylpyridinium bromide in the presence of ammonium acetate with a catalytic amount of acetic acid results in bicyclic annulated pyridines with additional benzylidene groups in high yields [15].…”