A practically convenient synthesis of (E)-3-arylidene-4-diazopyrrolidine-2,5-diones from N-substituted maleimides via the Wittig reaction and the Regitz diazo transfer has been developed. In all 26 cases studied, only one chromatographic purification was required with no need for aqueous workup, which makes this protocol amenable to producing the emerging class of diazo compounds in parallel format.