Experimental evidence for intramolecular ipso substitution of alkyl groups

An acid-mediated intramolecular Friedel-Crafts intramolecular alkene alkylation of the ortho-alkyl group in the N-aryl-amino 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.