An Ylide-Based Synthesis of 4-Phenylisocoumarin

Corey s procedures for the conversion of ketones into epoxides using sulfonium or oxosulfonium ylides have found widespread use in organic synthesis. An attempt to apply the method to methyl 2-benzoylbenzoate, however, gave 4-phenylisocoumarin in 52% yield when dimethyloxosulfonium methylide was used. 

It was found during this study that it was important to use only one equivalent of the methylide for preparation of the isocoumarin. When two equivalents were used, none of the isocoumarin was formed but, instead, a stable ylide was obtained in 96% yield. 

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