A Convenient Synthesis of 3,3-Dimethylcyclohexanone

Abstract

An interest in the boll weevil sex attractants¹ prompted an investigation into alternative syntheses of the starting material, 3,3-dimethylcyclohexanone (1). Despite its relatively simple structure, the available synthetic approaches to this comnound are often indirect and usually involve expensive or exotic reagents and starting materials. For example, 3,3-dimethyl-cyclohexanone (1) may be obtained from conjugate addition of lithium dimethylcuprate,² methylmagnesium iodide,³ or trimethyl-aluminum⁴ to 3-methyl-2-cyclohexen-l-one. Similarly, reaction of lithium dimethylcuprate with 3-t-butylthio-2-cyclohexen-l-one also yields ketone 1.⁵ Other preparations have involved hydrogenations of 5,5-dimethyl-2-cyclohexen-l-one⁶ and 5,5-dimethyl-3-chloro-2-cyclohexen-l-one⁷ and pyrolysis of β,β-dimethylpimelic anhydride.⁸ Ketone 1 was also obtained, albeit as a minor product, in the dichlorotris (triphenylphosphine) ruthenium catalyzed transfer hydrogenation of 5,5-dimethyl-l,3-cyclohexanedione.⁹