Aqueous Suspension of Basic Alumina: An Efficient Catalytic System for the Synthesis of Poly Functionalized Pyridines

Abstract

In the present work, catalytic activity of basic alumina in water has been demonstrated for the synthesis of poly functionalized pyridines. This strategy has some remarkable advantages, such as use of heterogeneous catalyst in aqueous media, reusability of catalyst and scalable approach.

A New Multicomponent Synthetic Route to Hexahydropyrido[2,3‐d]pyrimidine Derivatives

“…Refluxing benzaldehyde (1 equiv) and excess malononitrile (2 equiv) under the same reaction conditions gave the expected 2‐amino‐6‐ethoxy‐4‐phenylpyridine‐3,5‐dicarbonitrile 4 as reported in the literatures , while excess benzaldehyde (2 equiv) and one equivalent of malononitrile only gave 2‐benzylidenemalononitrile A as the intermediate. In the light of these observations, the reaction presumably proceeds by the following pathway (Scheme ).…”

“…One‐pot three‐component condensation reaction of substituted benzaldehydes, malononitrile, and thiophenol or ethanol in a 1:2.2:1 molar ratio in the presence of different catalysts such as K 2 CO 3 , NaHCO 3 , NaOH , NaH , Et 3 N , DBU , DABCO , piperidine , TBAF , TBAH , [bmim]OH , H 3 BO 3 , ZnCl 2 , MgO , Ce‐V/Al 2 O 3 , KF/Al 2 O 3 , ZrOCl 2 .8H 2 O/NaNH 2 , basic alumina , silica NPs , CaO NPs , CuI NPs , and ZnO NPs for the synthesis of polysubstituted pyridines has already been reported. Surprisingly, when we reacted equimolar amounts of malononitrile and benzaldehydes in ethanol under mild basic conditions, various hexahydropyrido[2,3‐ d ]pyrimidines 3a – h were obtained in good to excellent yield through a pseudo‐five‐component reaction (Scheme ).…”

Pyridine Derivatives—A New Class of Compounds That Are Toxic to E. coli K12, R2–R4 Strains

“…), and thiols in the presence of a catalyst [ 17 , 18 ]. Various catalysts have been reported to effect MCR, including nano-crystalline magnesium oxide, [ 19 ] silica nanoparticles [ 20 ], ZnCl 2 [ 21 ], piperidine/microwave [ 22 ] and Cd(II) metal–organic frameworks [ 23 ], refluxed in basic alumina [ 24 ]. Although the reported methods are efficient to provide the desired 2-amino-4-aryl-3,5-dicarbonitrile-6-sulfanylpyridines, there are still some drawbacks regarding these protocols, such as their longer reaction time, limited substrate scope, and complicated work-up processes, as well as the application of expensive, highly toxic and carcinogenic transition metal catalysts.…”

“…All bacterial strains were received and statistically analysed, as described in [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 ].…”

Multicomponent reactions in unconventional solvents: state of the art

“…82 This reaction can also be performed in an aqueous suspension of basic alumina. 83 With an analogous strategy, a method for synthesizing 2-amino-4-aryl(alkyl)-6-sulfanyl pyridine-3,5-dicarbonitrile 25 via a one-pot, three-component reaction of aldehyde with S-alkylisothiouronium salt and malononitrile has been developed in water in the presence of an inorganic base (Scheme 12). 84 The use of phase transfer catalyst, SDS, was demonstrated to be necessary to improve the reaction yield.…”