Manganese(III)-mediated transformations of phloroglucinols: a formal oxidative [4 + 2] cycloaddition leading to bicyclo[2.2.2]octadiones.

Manganese(III)-mediated oxidative transformations of dearomatized phloroglucinol (1,3,5-trihydroxybenzene) derivatives are reported. A number of cyclization modes have been observed, including polycyclization to afford bicyclo[2.2.2]octadiones via a formal oxidative radical [4 + 2] cycloaddition.