Vinylphosphonium Salt Mediated Facile Synthesis of Trialkyl 4-(2-Quinolyl)-1-cyclobutene-1,2,3-tricarboxylates and Dialkyl 3-Ethoxy-4-oxo-5-(2-(1H)-quinolinylidene)-2-cyclopentene-1,2-dicarboxylates

Summary.

 The reactive 1:1 intermediate produced in the reaction between dialkyl acetylenedicarboxylates and triphenylphosphine was trapped by ethyl 3-(1,2-dihydroquinoline-2-ylidene)-pyruvate to yield the isomeric dialkyl 3-ethoxy-4-oxo-5-(2-(1H)-quinolinylidene)-2-cyclopentene-1,2-dicarboxylates and trialkyl 4-(2-quinolyl)-1-cyclobutene-1,2,3-tricarboxylates in nearly 4:1 ratio.