Synthesis of 4-substituted oxazolo[4,5-c]quinolines by direct reaction at the C-4 position of oxazoles

Abstract

A facile synthesis of 4-aryl substituted oxazolo[4,5-c]quinolines has been described via a modified Pictet-Spengler method and using Cu(TFA)2 as a catalyst. The developed methodology directly functionalizes the C-4 position of oxazoles without the aid of any prefunctionalization, in the presence of the more reactive C-2 position in good yields. The versatility of the established method has been demonstrated by its application in the synthesis of 4-substituted oxazolo-[1,8]naphthyridine ring systems.

Benzopyrano‐Fused N‐Heterocyclic Polyaromatics

“…The Pictet–Spengler reaction was broadly used in the syntheses of nitrogen containing extended aromatic systems like azacoronenes, extended pyrrolopyrroles, fused porphyrins or other polycyclic compounds . While applying the Pictet–Spengler reaction in the synthesis of ligands for boroquinol complexes from amine 1 and salicylaldehyde 2 , it was realized that compound 3 undergoes a transformation at 180 °C (Scheme ): Treating phenol 3 for 24 h at this temperature in vacuo gave cyclized compound 4 in 80 % yield.…”

Synthesis of Dibenzo[b,h][1,5]naphthyridin-7(12H)-ones: The Pictet–Spengler Reaction versus a Rearrangement of 4-Phenyl[1,3]oxazolo[4,5-c]quinolines

“…Yield: 204 mg (83%); white solid; mp 137-138 °C (Lit. 23 mp 134-138 °C). IR (KBr): 3074, 1806(KBr): 3074, , 1643(KBr): 3074, , 1594(KBr): 3074, , 1518(KBr): 3074, , 1504(KBr): 3074, , 1447(KBr): 3074, , 1361(KBr): 3074, , 1319(KBr): 3074, , 1201(KBr): 3074, , 1051(KBr): 3074, , 1021, 634 cm -1 .…”

One‐Step Synthesis of Fused Chromeno[4,3‐b]pyrrolo[3,2‐h]quinolin‐7(1H)‐One Compounds and their Anticancer Activity Evaluation

“…We have an ongoing interest in the synthesis and applications of fused heterocyclic compounds . In continuation with our research programme, we have initiated an exploration in the area of coumarin fused heterocyclic systems.…”