Sodium borohydride → 6'-Bromo-4-hydroxyspiro[cyclohexane-1,2'-inden]-1'(3'H)-one

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Reaction Conditions

Reaction Steps

6′-Bromospiro[cyclohexane-1,2′-indene]-1′,4(3′H)-dione (Intermediate 5 Step 1, 6.1 g, 20.8 mmol) was dissolved in THF (220 mL) and cooled to −65° C. Sodium borohydride (0.354 g, 9.36 mmol) was added and the cooling bath was removed. The mixture was allowed to reach 0° C. (approx. 30 min). Water (10 mL) was added, and most of the organic solvent was removed by evaporation. The residue was partitioned between EtOAc (100 mL), and an aq. solution of NaCl (50 mL). The organic phase was dried (MgSO4) and evaporated to give a product which was combined with additional product obtained in a similar way starting from 14.6 g of 6′-bromospiro[cyclohexane-1,2′-indene]-1′,4(3′H)-dione. Purification was made by flash chromatography (120 g silica, gradient elution: CH2Cl2 to CH2Cl2/MeOH (90:10)) affording 13.6 g (66% yield) of the title compound. The obtained material consisted of an 80:20 mixture of isomer 1 and isomer 2. Analytical samples of the isomers were isolated by flash chromatography (heptane/EtOAc gradient) to yield:

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