Dimedone → 6,6-Dimethyl-1,5,6,7-tetrahydro-4H-indol-4-one

Participants

Reaction Conditions

Reaction Steps

A solution of 5,5-dimethyl-1,3-cyclohexandione (30 g, 0.21 mol), aminoacetaldehyde dimethyl acetal (35 mL, 0.32 mol) and p-toluenesulphonic acid hydrate (1.5 g, 8 mmol) in toluene (250 mL) were heated at reflux for 4 h using Dean-Stark apparatus to remove the water. The toluene was evaporated and the residue dissolved in 3N HCl (250 mL). The solution was heated at 60° C. for 6 h. After this time the mixture was cooled to room temperature and extracted with DCM (6×). The combined organic layers were dried (MgSO4), evaporated and the residue chromatographed on silica gel, eluting with isohexane: EtOAc (4:1→1:1). The fractions containing the desired product were combined, evaporated and the residue triturated with ether. The title compound (1.8 g, 5%) was isolated as a cream solid. mp 177-178° C. 1H NMR (360 MHz, d6-DMSO) 8 1.02 (6H,s), 2.19 (2H,s), 2.63 (2H,s), 6.23 (1H,t, J=3.9 Hz), 6.71 (1H,t, J=3.9 Hz). MS (ES+) 164 (M+1).

Provenance & Evidence