Diels-Alder reactions of pyrrolo[3,4-b]porphyrins
Abstract
In the presence of excess dimethylacetylene dicarboxylate (DMAD), nickel(II) pyrrolo[3,4-b]porphyrins undergo both Diels-Alder cycloaddition and Michael addition in toluene to give two bis-adducts, identified as compounds 4 and 5; the reaction can be accelerated by the addition of Lewis or Brønsted-Lowry acids. Refluxing the reaction mixture in 1,2,4-trichlorobenzene (220°C) leads to a nickel(II) monobenzoporphyrin 2 as the main product. The structure of compound 4 was confirmed by X-ray crystallography. © 2005 Elsevier Ltd. All rights reserved.
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