A simple synthesis of spiro-C6-annulated hydrocyclopenta[g]indole derivatives

A series of new spiro-C6-annulated hydrogenated cyclopenta[g]indoles (5) was prepared by applying Madelung method to the appropriate 4-(N-acetylamino)-1-spiroindanes (9), synthesised via acid-catalysed intramolecular rearrangement of 1-acetyl-3,4-dihydrospiro[quinoline-2,1′-cycloalkanes] (8).