One-pot, three-component synthesis of dialkyl 1,2-dihydroquinoline-2,3-dicarboxylates from triphenylphosphine, acetylenic esters, and amide derivatives of 2-aminobenzaldehyde in aqueous acetone

Protonation of the highly reactive 1:1 intermediates, produced in the reaction between triphenylphosphine and dialkyl acetylenedicarboxylates by amide derivatives of 2-aminobenzaldehyde in the mixture of acetone-water (3:1) leads to vinyltriphenylphosphonium salts, which undergo a Michael addition reaction with a conjugate base to produce the corresponding stabilized phosphorus ylides. An intramolecular Wittig reaction of the stabilized phosphorus ylide group with the aldehyde group leads to the corresponding dialkyl 1,2-diltydroquinoline-2,3-dicarboxylates.