Sulfuric Acid → 2-methyl-2,3,5,6,7,8-hexahydro-1H-cyclopenta[b]naphthalen-1-one

Participants

Reaction Conditions

Reaction Steps

According to the procedure of Bhattacharya et.al (Synth. Commun 1996., 26, 1775-1784.) a mixture of 1-(5,6,7,8-tetrahydro-naphthalen-2-yl)-propan-1-one (37.6 g), hexamethylenetetramine (44.9 g) and acetic anhydride (38.8 mL) is heated with stirring at 80° C. for 23 hours. The mixture is allowed to cool, and added slowly to a stirred mixture of ethyl acetate (200 mL) and aqueous sodium hydroxide (200 mL, 2M). The organic layer is separated, washed with aqueous HCl, brine, and dried (Na2SO4). The solvent is removed to give a brown oil. This is added cautiously to concentrated sulfuric acid (120 mL) and the resulting mixture is heated at 55° C. for 5 hours followed by room temperature for 18 hours. The reaction is diluted with water and extracted with dichloromethane. After drying (Na2SO4) the solvent is removed to give an oil. The product is purified by chromatography (silica, ethyl acetate/hexane) to give a geometrical mixture of isomers containing 2-Methyl-1,2,6,7,8,9-hexahydro-cyclopenta[.a.]naphthalen-3-one and the title compound.

Provenance & Evidence