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The aldol condensation product of 1H-indan-1-one, (2E)-2-(2,3-dihydro-1H-inden-1-ylidene)-2,3-dihydro-1H-inden-1-one, subjected to Huang–Minlon reduction conditions was shown, via 1D and 2DNMRanalysis, to be amixture of (1S,1aR,6aR)-2’,3’,6,6a-tetrahydro-spiro[cycloprop[a]indene-1(1aH),1’-[1H]indene] and its 1R,1aS,6aS enantiomerand not 2,3,1’,3’-tetrahydro-[1,2’]-biindenylidene as originally expected. The full NMR assignment, the coupling constants in the proton NMR, and the couplings in the HMBC and NOESY of the title compound are summarized in the Table.