Abstract An acid‐mediated intramolecular Friedel−Crafts intramolecular alkene alkylation of the ortho ‐alkyl group in the N ‐arylamino moiety of various N ‐(1‐allylcycloalkyl)‐ N ‐arylamines resulting in alkyl‐substituted 3′,4′‐dihydro‐1′ H ‐spiro[cycloalkane‐1,2′‐quinolines] is described. The mechanistic details of this intramolecular Friedel−Crafts alkylation by an alkene moiety can be explained by an intramolecular alkylation with ipso substitution of alkyl groups and their 1,2‐rearrangement. The scope and limitations of this reaction were determined. As a conclusive proof of the proposed mechanism, previously unknown interesting by‐products, dispiro[quino[6,7‐ f ]quinoline‐3,1′:9,1′′‐bis(cycloalkanes), were isolated and characterized. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)