Wittig-Horner Reaction of Dimethyl Phthalide-3-phosphonates with Ketones: Synthesis of 3-Ylidenephthalides and Their Conversion to 2,2-Disubstituted Indan-1,3-diones Including Spirocyclic Compounds

The Wittig-Horner reaction of dimethyl phthalide-3-phosphonates with various ketones was investigated under the conditions: lithium bis(trimethylsilyl)amide (LHMDS) or sodium hydride in tetrahydrofuran, and cesium carbonate in isopropyl alcohol. The sequential treatment of the 3-ylidenephthalides with diisobutylaluminium hydride (DIBAL-H) and pyridinium dichromate (PDC) afforded 2,2-disubstituted indan-1,3-dione derivatives in modest to high overall yields.