Synthesis of indolines and tetrahydroquinolines from ortho -(alk-2-enyl)anilines

Intramolecular cyclization of o -alkenylanilines was studied. Heating of o -(cyclopent-2-en-1-yl) arylammonium chlorides at 200–220 °C yields cyclopenta[ b ]indolines as the main reaction products. Cyclization of 4-methyl-2-(pent-3-en-2-yl)aniline under the same conditions gave a mixture of indolines and tetrahydroquinolines. An alk-1-enylarylamine containing a vinylic double bond does not form cyclization products on the nitrogen atom.