Konrad-Limpach synthesis

Primary arylamines and p-keto esters condense in the presence of strong acids to form 2-quinolones Knorr synthesis) via P-keto anilides (e.g. 78). A thermal reaction involving p-anilinoacrylic esters (e.g. 79) yields 4-quinolones (Konrad-Limpach synthesis). ... 

While the 2-quinolone formation is due to an SgAr process analogous to a Combes synthesis, the 4-quinolone formation is thought to be the result of an electrocyclization. The Konrad-Limpach synthesis is very flexible with regard to the arylamine and P-keto ester substituents, as well as to the use of alkoxymethylene malonic esters and dianilides of malonic aicid... 

When P-ketoesters are reacted with primary aromatic amines, product formation is dependent on the reaction conditions. In the presence of strong acids, P-ketoaniUdes 98 are formed, which undergo cyclization to 2-quinolones (Knorr synthesis). When the reaction is carried out thermally, P-aminoacrylates 99 are the primary products, which cyclize to give 4-quinolones (Konrad-Limpach synthesis) ... 

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