High-Yielding, Scalable Synthesis of 5,15-Dioxaporphyrin

5,15-Dioxaporphyrin (DOP) is a stable 20π antiaromatic molecule with potential for investigating properties arising from antiaromaticity. However, low yields in large-scale synthesis combined with tedious workup procedures have impeded further development of DOP chemistry. Here, we established a high-yielding, scalable synthesis by modifying the concentrations, oxime reagents, reaction time, and solvents. In addition to the reasonable substrate scope, this improved method also enabled the first synthesis of a palladium complex of DOP.