A NEW METHOD FOR CONSTRUCTION OF CYCLIC ENONES VIA PHOSPHONATE ANIONS

The reaction of 2,2-disubstituted 1,3-cyclohexanediones (1) with dimethyl methylphosphonate anion in the presence of trimethylsilyl chloride produces 3-substituted 2-cyclohexenones (2) in moderate to very good yields. This new overall reaction is accounted for by (1) attack of the phosphonate anion on a carbonyl group, (2) retro-aldol cleavage, (3) reorganization of the-acidic proton, and (4) an intramolecular Wadsworth-Emmonds condensation. The new rearrangement is applied to a short synthesis of (+/-)-alpha-acoradiene. The synthesis of 3-substituted 2-cyclopentenones (10) is accomplished via two-step processes.