Synthesis of a New Spirolactone: 7,10-Dimethoxy-1-oxaspiro[4,5]deca-6,9-diene-2,8-dione

The title compound was synthesized in 36 % yield by oxidative spiroannulation of the corresponding 2,4,5-trisubstituted phenol. Interestingly, this phenol was prepared in 57 % yield from another spirocompound, namely 7-methoxy-1-oxaspiro[4,5]deca-6,9-diene-2,8-dione. We have speculated that the formation of the phenol was due to a series of reactions involving a conjugate addition of methanol to the original spirolactone followed by aromatization and lactone hydrolysis.