Beschreibung:
<jats:p><jats:bold>A New and Simple Method for the Synthesis of Spirocyclic la‐Quinolines</jats:bold></jats:p><jats:p>The reaction of anilines with (+)‐(<jats:italic>R</jats:italic>)‐pulegone in toluene at temperatures between 125 and 150° with 4‐toluenesulfonic acid or I<jats:sub>2</jats:sub> as catalysts leads to diastereoisomeric mixtures of spiro[cyclohexane‐1,2′(1′<jats:italic>H</jats:italic>)‐quinoline] derivatives (see <jats:bold>1–4</jats:bold>, <jats:italic>Scheme 1; Table</jats:italic>). The diastereoisomers are separated by column chromatography, and the structure of the single isomers is determined by NMR‐spectroscopic methods. A reaction mechanism proceeding <jats:italic>via</jats:italic> several 6π‐electrocyclic rearrangements and H‐shifts is proposed for the formation of 1<jats:italic>H</jats:italic>‐quinolines <jats:bold>1–4</jats:bold> (<jats:italic>Scheme 2</jats:italic>). This mechanism is in accordance with the results of the reaction of 2‐isopropenylaniline with 3‐methylcyclohexanone which leads to a stereoisomeric mixture of 3,4′‐dimethylspiro[cyclohexane‐1,2′(1<jats:italic>H</jats:italic>)‐quinolines] (<jats:italic>Scheme 3</jats:italic>).</jats:p>