Microwave‐assisted regioselective one‐pot synthesis of trisubstituted pyridine scaffolds using K₅CoW₁₂O₄₀.3H₂O under solvent free conditions

Abstract

A highly efficient, microwave-assisted, regioselective synthesis of 2,3-disubstituted-6-arylpyridines and new series of 7,7-dimethyl-2-aryl-5,6,7,8-tetrahydroquinoline-5-ones from enaminones in the presence of K 5 CoW 12 O 40 .3H 2 O (1.0 mol %) as heterogeneous catalyst under solvent free conditions is reported.

Facile Diversity-Oriented Synthesis and Antitubercular Evaluation of Novel Aryl and Heteroaryl Tethered Pyridines and Dihydro-6H-quinolin-5-ones Derived via Variants of the Bohlmann–Rahtz Reaction

“…Although the method is readily adopted, there is no synthetic protocol for the preparation of several β-enaminones used in this work. Literature described β-enaminones were synthesized by a protocol standardized in our laboratory . Extending it to other heteroaryl β-enaminones, ( E )-1-(Dibenzo[ b,d ] thiophene-2-yl)-3-(dimethylamino)-2-propenone 1 { 7 }, ( E )-3-Dimethyl amino-1-[1-(toluene-4-sulfonyl)-1 H -indol-3-yl]propenone 1 { 10 }, ( E )-1-(5-Chlorothiophen-2-yl)-3-dimethylaminopropenone 1 { 13 }, ( E )-6-(3-Dimethylaminoacryloyl-3-methyl- 3H -benzothiazol-2-one 1 { 15 }, and ( E )-6-(3-Dimethylamino acryloyl)-4-methyl-4 H -benzo[ 1,4 ]xazin-3-one 1 { 16 } were synthesized in excellent yields.…”

“…β-Enaminones, because of the presence of ambident nucleophilic character of enamine moiety and the ambident elctrophilic character of enone moiety, turned out to be simple synthetic intermediates for the subject of the present synthesis (Figure B). Taking advantage of their electronic properties, we envisioned to use aryl and heteroaryl embodied β-enaminones as polarized variants of acetylenic ketones in the synthesis of 2,3,6-trisubstituted pyridines and quinolin-5-ones with three points of diversity …”

“…On the basis of our progressive endeavors in exploring novel one-pot reactions, we herein report an efficient CeCl 3 ·7H 2 O-NaI catalyzed regioselective conversion of β-enaminones 1 { 1–16 } to novel substituted pyridines 3 {( 1–16 ), 1 } and dihydro-6 H -quinolin-5-ones 4 {( 1–16 ),( 2–3 )} having appended aryl and heteroaryl groups through Michael addition, cyclodehydration and elimination sequence. One-pot reaction of substituted ( E )-aryl and ( E )-heteroaryl 3-(dimethylamino)-3-prop-2-enone 1 { 1–16 } (here after called as enaminones) derived from the respective commercially available aryl and heteroaryl methyl ketones; with readily available ethyl acetoacetate 2 { 1 } or cyclic 1,3-dicarbonyls 2 { 2–3 } and ammonium acetate in the presence of catalytic amount of CeCl 3 ·7H 2 O-NaI resulted title compounds with high regioselectivity at 2,3,6-positions.…”

Environmentally benign synthesis of heterocyclic compounds by combined microwave-assisted heterogeneous catalytic approaches†

“…Syntheses of 2,3-disubstituted-6-aryl pyridines and 7,7dimethyl-2-aryl-5,6,7,8-tetrahydroquinoline-5-ones were achieved efficiently in a solvent-free reaction catalyzed by a potassium dodecatungstocobaltate trihydrate catalyst (1 mol% catalyst loading) and a strong heteropoly acid (Scheme 20). 55 The target compounds were synthesized by the condensation of enaminones and cyclic/acyclic 1,3-diketones in excellent yields in 3-6 min.…”

Chemoselective Condensation of 3-Amino-2-cyclohexenones with Cinnamaldehydes: Switchable Synthesis of Dihydroquinolinones and Hexahydroacridinediones

“…Among them, dihydroquinolinones and hexahydroacridinediones represent a large family of active ingredients that strongly inhibit or modulate the potentials of phosphoinositide-specific phospholipase C-γ (PLC-γ), free fatty acid receptor 3 (FFA3), metabotropic glutamate receptor 5 (mGlu 5 ), human carbonic anhydrase isoenzymes (hCA I/II), general control non-repressed protein 5 (GCN5), and CDK 4/6 (Figure ). Many synthetic strategies have been used to prepare dihydro-6 H -quinoline-5-one skeletons either by the reaction of β-enaminones with 1,3-diketones in the presence of catalysts such as K 5 CoW 12 O 40 , CeCl 3 , and DBU or by the reaction between a 1,3-diketone, aldehyde, and ketone , /β-chloro-α,β-unsaturated aldehyde in the presence of catalysts such as MCM-41, etc. (Scheme a).…”