Direct synthesis of pyran-lactones related to naphthoquinoneantibiotics

Simple benzopyrans with a fused γ-lactone unit are prepared from an o-disubstituted arene by direct intramolecular alkoxycarbonylation/lactonization promoted by palladium diacetate; the process gives high yields and moderate stereoselectivity, favoring the $\text{cis}$ lactone over $\text{trans}$ by a factor of 5:1.