A malonic ester‐type synthesis with 4‐chloroquinoline utilizing highly acidic enols

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Abstract
A synthetic method of attaching carbon‐chain substituents to the 4‐position of the quinoline ring was developed. In our approach enolate anions were generated from highly acidic enols under conditions in which the 4‐chloroquinoline can be N‐acylated or N‐protonated. Isopropylidene alkyl(4‐quinolyl)malonates or 5‐alkyl‐5‐(4‐quinolyl)barbituric acids were obtained from the reaction of 4‐chloroquinolines with isopropylidene alkylmalonates in acetic anhydride or with 5‐alkylbarbituric acids by heating in the absence of solvent. Some of the products were hy‐drolyzed and decarboxylated to give the corresponding 4‐alkylated quinolines.