Dimedone → 3,6,6-trimethyl-6,7-dihydro-1H-indol-4(5H)-one

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Reaction Steps

To a solution of anti-pyruvic aldehyde-1-oxime (10 g, 1 eq) and 5,5-dimethyl-1,3-cyclohexanedione (16.1 g, 1 eq) in HOAc—H2O (7:3, 200 mL) was added zinc powder (14.95 g, 2 eq) slowly with cooling by a water bath at room temperature. The mixture then was refluxed overnight, concentrated to dryness, partitioned between brine (300 mL) and dichloromethane (300 mL). The pH was adjusted to ca. 6 with saturated aqueous NaHCO3, then the mixture was extracted with dichloromethane (3×200 mL). The organic layers were combined, dried over Na2SO4, filtered, concentrated. The crude product was purified by flash chromatography eluting with 5% ethyl acetate in dichloromethane. The combined organic fractions were concentrated, triturated in ether-hexane (2:1) for 1 hour, then filtered, washed with hexane to give the pure title compound (9 g, 45% yield) as a solid. LCMS m/z: (M+H)=178.1.

Provenance & Evidence