Water → 2-Cyclohexene 1,3-cyclopentanedione

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To a suspension of 1,3-cyclopentandedione (4.00 g, 0.040 mmol) in water (30 ml) were added LiOH.H2O (1.88 g, 0.045 moll) and 3-bromocyclohexene (7.18 g, 0.045 mmol). The solution was stirred overnight, the pH raised to 12-14 (LiOH.H2O) and stirred for 2 h. The solution was washed with Et2O (4×40 ml), acidified to pH 1-2 and resulting solids isolated by filtration, washed and dried to give 2-cyclohexene-1,3-cyclopentanedione. [δH (CD3OD) 5.69 (1H, m), 5.44 (1H, m), 3.20 (1H, m), 2.47 (4H, s), 2.15-1.19 ˜(6H, m). m/z ESI, 70V) 179 (MH+)]. The product was dissolved in EtOH (50 ml) and reduced under an atmosphere of H2 at RT with Pd/C (200 mg). After 5 h the reaction was filtered and the solvent removed to give the title compound as a white solid (890 mg 12%). δH (CD3OD) 2.44 (4H, 2), 2.39 (1H, m), 1.85-1.70 (5H, m), 1.50-1.45 (2H, m), 1.35-1.15 (3H, m). m/z (ESI, 70V) 181 (MH+).

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