Manganese(III)-based dioxapropellane synthesis using tricarbonyl compounds

The manganese(III)-induced oxidative cyclization of 3-(2-oxoethyl)piperidine-2,4-diones was conducted in the presence of 1,1-diarylethenes at reflux temperature to produce 3-aza-7,12-dioxatricyclo[4.3.3.01,6]dodec-8-en-2-ones, simply called azadioxa[4.3.3]propellanes, in excellent yields. A similar oxidation of 2-(2-oxoethyl)cycloalkane-1,3-diones gave the corresponding [4.3.3]-, [5.3.3]-, and [6.3.3]-propellanes. The oxidation of 3-oxopropyl-substituted cycloalkane-1,3-diones also afforded the corresponding propellanes along with the 3-oxopropyl-substituted bicyclic intermediates. The bicyclic intermediates were definitely converted into the corresponding propellanes in the presence of a Lewis acid. The structure determination and the reaction pathway were also described.