Aromatische Spirane, 16. Mitt.: Darstellung von monound dianellierten 2,2′-Spirobiindan-1,1′-dionen

Summary The spiroketones19, 21, 24, 27, and31 were prepared by cyclisation of the dicarboxylic acids and their acid chlorides, resp., (18, 20, 22, 23, 25, 26, 28, and30) with polyphosphoric acid (PPA) or SnCl₄. The latter compounds were synthesized by alkylation of the appropriate -keto esters10, 11, 12, and13 with the benzyl chlorides14, 15, 16, and subsequent retro-Claisen-reaction. The spiro compounds21a and39 were obtained byPPA-cyclisation of the keto acids35 and38, which in turn were prepared by aldol-reaction of the ketoness-hydrindacen-1-on and9a with phthalaldehydic acid to the olefinic keto acids33 and36 followed by catalytic hydrogenation.