Methyl Acrylate → 6'-Isobutoxyspiro[cyclohexane-1,2'-indene]-1',4(3'H)-dione

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To a mixture of 6-isobutoxy-2,3-dihydro-1H-inden-1-one (Intermediate 4, 17.4 g, 85 mmol) and methyl acrylate (16.9 mL, 187 mmol) in 2-Me THF (84 mL) cooled to 0° C. was added potassium tert-butoxide (11.8 g, 102 mmol) in portions over 3 min. After stirring at r.t. for 2.5 h more potassium tert-butoxide (2.95 g, 25.5 mmol) was added at 0° C. After stirring at r.t. for 2.5 h were water (126 mL) and potassium hydroxide (4.77 g, 85 mmol) added and the mixture was heated at reflux overnight. The mixture was allowed to cool to r.t. and brine was added. The layers were separated and the aqueous layer was re-extracted with EtOAc twice. The combined organic layers were dried over Na2SO4, filtered and evaporated to yield the title compound (13.7 g, 56% yield). 1H NMR (400 MHz, CDCl3) δ ppm 1.04 (m, 8 H) 1.86 (m, 2 H) 2.11 (dt, 1 H) 2.21 (m, 2 H) 2.47 (m, 3 H) 2.70 (m, 2 H) 3.15 (s, 2 H) 3.76 (m, 3 H) 7.20 (m, 1 H) 7.25 (m, 1 H) 7.38 (d, 1 H); MS (ES+) m/z 287 [M+H]+.

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