Methyl iodide → 1,3-Cyclopentanedione, 2,2-dimethyl-

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The published procedure was followed. (Agosta, W. C.; Smith, A. B. J. Org. Chem. 1970, 35, 3856) A mixture of 2-methyl-1,3-cyclopentanedione (10.025 g, 89.4 mmol, Aldrich), methyl iodide (6.0 mL, 96.4 mmol, Aldrich), and KOH (5.097 g, 90.8 mmol) in H2O (25 mL)/dioxane (75 mL) was heated at reflux. After 5 h, a solution of KOH (2 g) and MeI (2.4 mL) in H2O (5 mL)/dioxane (15 mL) was added and after another 3 h at reflux the solution was allowed to stir at room temperature overnight. In the morning, the reaction was continued by addition of a solution of KOH (2 g) and MeI (2.4 mL) in H2O (5 mL)/dioxane (15 mL) and heating at reflux. After 4 h, the mixture was allowed to cool to room temperature and was extracted with ether (1×100 mL, 3×75 mL). The combined ether extracts were evaporated, the residue combined with HCl (50 mL 10%), and the resulting mixture was placed in a 120° C. oil bath until boiling was observed (ca. 15 min.). The mixture was then allowed to cool to room temperature, was neutralized by addition of NaHCO3 solution (150 mL, saturated) and the resulting mixture then extracted with CH2Cl2 (4×75 mL). The combined CH2Cl2 solution was dried (MgSO4), filtered and evaporated to leave a brown oil (10.474 g, 83 mmol, 93%) which was used directly in the next step.

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