A facile and efficientone-potsynthesis of pyrano[2,3-b]quinolines has been developed via the Combes-type reaction of readily available enaminones, 2-arylamino-3-acetyl-5,6-dihydro-4H-pyrans, mediated by trifluoromethanesulfonic acid undersolvent-freeconditions.
Solvent-controlled, regio-switchable formation of 3-/5-arylaminopyrazole isomer in cyclocondensation of β-aminoenones with hydrazides: intermolecular hydrogen bonding plays a role
An unprecedented solvent-controlled, regio-switchable Knorr-type reaction for the synthesis of pyrazoles has been realized in the cyclocondensation of β-aminoenones with hydrazides. Single regioisomer of 3- or 5-arylaminopyrazole can be obtained simply by changing the reaction solvent. Using hydrazine hydrate, only 3-arylaminopyrazoles were produced.
A highly regioselective synthesis of 3-arylamino- and 5-arylaminoisoxazoles from enaminones based on reaction condition selection is reported. 3-Arylaminoisoxazoles were produced by treating enaminones with aqueous hydroxylamine in OAF at 100 degrees C, whereas 5-arylaminoisoxazoles were synthesized by subjecting enaminones to aqueous hydroxylamine in the presence of KOH and TBAB in water under reflux. A mechanism for the regioselective synthesis of 3-arylamino- and 5-arylaminoisoxazoles is proposed.