AN EXCEEDINGLY MILD AND EFFICIENT SYNTHESIS OF 1,2,4-TRIAZOLO[4,3-a][1,8]NAPHTHYRIDINES USING IODOBENZENE DIACETATE IN THE SOLID STATE

Green Synthesis of Fused Imidazo[1,2‐a][1,8]naphthyridine Derivatives Catalyzed by DABCO under Solvent‐Free Solid‐State Conditions and Their Biological Evaluation

“…Rate accelerations can be described because of the conversion of mechanical energy (kinetic energy applied due to grinding) into heat energy, which becomes the driving force for improved activation of molecules. The kinetic energy provided during grinding can have various effects on a crystalline solid which exclusively is a kind of “stirring.” To develop an eco‐friendly green methodology, we have synthesized novel fused imidazo[1,2‐a][1,8]naphthyridine scaffolds using under the solvent‐free grinding method by involving 2‐aminonicotinaldehyde 1 on condensation with phenylacetonitrile 2 in the presence of piperidine obtained corresponding compound 2‐amino‐1,8‐naphthyridines 3 at room temperature according to the literature procedure , and then 2‐amino‐1,8‐naphthyridines reacted with 2‐bromo‐1‐(4‐chlorophenyl)ethan‐1‐one 4 in the presence of DABCO (10 mol %) 11.2 mg in water (5 mL) interestingly furnished corresponding 9‐(4‐chlorophenyl)‐6‐phenylimidazo[1,2‐a][1,8]naphthyridine derivatives ( 5a–g ) with good yields, and then the same reaction carried out 3‐(2‐bromoacetyl)‐2H–chromen‐2‐one 6 instead of 2‐bromo‐1‐(4‐chlorophenyl)ethan‐1‐one obtained 3‐(6‐phenylimidazo[1,2‐a][1,8]naphthyridin‐9‐yl)‐2H–chromen‐2‐one derivatives ( 7a–f ) with good yields in short reaction time. The reaction is facile and efficient and is devoid of any side products.…”

Efficient synthesis of 1,2,4‐triazolo[4,3‐a][1,8]naphthyridines under microwave irradiation

“…Microwave irradiation was carried out in a domestic microwave oven (LG MG 556p, 2450 MHz). The starting compounds 1 were prepared according to our reported procedures [16–20]. The 4‐phenoxylbenzaldehyde ( 2 ) was purchased from Aldrich Chemical Company.…”

Hypervalent‐Iodine(III)‐Mediated Oxidative Methodology for the Synthesis of Fused Triazoles

“…In their approach, oxidative cyclization of the hydrazones with an equimolar amount of IBD in the solid state by grinding at room temperature for 5min resulted in the formation of 9-aryl-6-(4-methoxyphenyl)-[1,2,4]-triazolo[4,3-a] [1,8]naphthyridine derivatives in good yields (70-82 %) with high purity.O no ther hand, stirring the reaction mixture in CH 2 Cl 2 for the same reactiont ime at room temperature gave the product in 15 %y ield (Scheme 20). [50] Interestingly,w hen the same reaction was performed under conventionalc onditions in an oil bath that had been pre-heated to 120 8C( the highest observed temperature during the irradiation reaction), the reaction only proceeded to am inor extent (5-10 %) in 4-6 min (Scheme 21). [51] 6.…”