Various enolic compounds such as acetyl acetone, ethyl- and methyl-acetoacetate condense with 2-hydroxy-2, 2′-biindan-1,1′,3,3′-tetrone 1 in acid medium to produce adducts, which preferentially remain in the hemi-ketal form as confirmed by X-ray diffraction studies. 1 is also found to undergo acid catalysed dimerisation to furnish a cage like adduct fabricated by ketal and hemi-ketal linkages.
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Data sets were collected with a Nonius KappaCCD diffractometer. Programs used: data collection COLLECT (Nonius B.V., 1998), data reduction Denzo-SMN (OtwinowskiZ., MinorW., Methods in Enzymology, 1997, 276, 307–326), absorption correction Denzo (Z. Otwinowski, D. Borek, W. Majewski, W. Minor, Acta Cryst. 2003, A59, 228-234), structure solution SHELXS-97 (G.M. Sheldrick, Acta Cryst. 1990, A46, 467-473), structure refinement SHELXL-97 (G.M. Sheldrick, Universität Göttingen, 1997), graphics SCHAKAL (E. Keller, 1997). CCDC 261134, CCDC 261135 and CCDC 261136 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request.cif.
