Diels-Alder reactions of pyrrolo[3,4-b]porphyrins

Diels-Alder reactions of nickel(II) pyrrolo[3,4-b]porphyrins with DMAD give benzoporphyrin diesters; two new bis-DMAD adducts (4 and 5) are intermediates produced by [4+2] cycloaddition and Michael addition to the pyrroloporphyrin.