Efficient MnIII-mediated synthesis of functionalized trans-3,4-disubstituted-γ-butyrolactones

The MnIII-induced addition of malonic acid (instead of acetic acid) to cinnamic esters affords in one step functionalized trans-3,4-disubstituted-γ-butyrolactones in a greatly improved yield which can be further optimized by conducting the reaction in either acetic or formic acid, depending on the substrate.