Phosphorus Pentoxide in Organic Synthesis XXXII: A New Synthesis of Quipazine and Its N‐Methyl Derivatives

Abstract

2-(4-Methyl·l·piperazinyl)quinolines I were prepared by heating acetanilides and N. N-dialkylformamides with a mixture of P 20S and N-methylpiperazine at 250°. Quipazine was obtained by von Braun degradation of la to N-cyano-N' -(2-quinolyl)piperazine (2) and hydrolysis in sulfuric acid. Phosphorpentoxid in der organischen Synthese, 32. Mitt.: Eine neue Synthese des Quipazins und seines N-Methyl-Derivates 2-(4-Methyl-l-piperazinyl)-chinoline wurden durch Erhitzen von Acetaniliden und N,N-Dialkyl-formamiden mit einer Mischung von P 20S und N-Methyl-piperazin bei 250° dargestellt. Quipazine wurde durch von Braun-Abbau von la zu N-Cyan-N'-(2-chinolyl)-piperazin (2) erhalten, von Hydrolyse in Schwefelsäure gefolgt. Quipazine and similar compounds are usually synthesized from the corresponding 2-haloquinolines 2 -s l.~I\ ~N~N NH '-.! 2-(4-Methyl-l-piperazinyl)quinolines were now synthesized in 10-39 % yield by heating acetanilides in a mixture ofN.N-dialkylformamide. P 2 0 S and N-methylpiperazine at 250°. Quipazine itself cannot be synthesized in this way starting from a piperazine/P 2 0 S mixture. In this case both N-atoms in the piperazine ring will react. N.N'bis(2-quinolyI)piperazine and N-formyl-N'-quinolylpiperazine were detected 15). It was