Unprecedented Double aza-Michael Addition within a Sapphyrin Core

• Published in: Chemistry : a European journal 2016-09, Vol.22 (40), p.14349-14355
• Main Authors: Figueira, Flávio, Marques, Igor, Farinha, Andreia S. F., Tomé, Augusto C., Cavaleiro, José A. S., Silva, Artur M. S., Sessler, Jonathan, Félix, Vítor, Tomé, João P. C.
• Format: Article
• Language: English
• Subjects: Acetylene; Acetylene - chemical synthesis; Acetylene - chemistry; Alkynes - chemical synthesis; Alkynes - chemistry; anions; Carbon; Chemistry; cycloaddition; Cycloaddition Reaction - methods; density functional calculations; Derivatives; Dimethyl; Formations; Heterocyclic compounds; Links; Magnetic Resonance Spectroscopy; Mathematical analysis; Michael addition; Models, Molecular; NMR; Nuclear magnetic resonance; porphyrinoids; Porphyrins - chemical synthesis; Porphyrins - chemistry; Pyrroles - chemical synthesis; Pyrroles - chemistry; Spectra
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201602313

A novel sapphyrin derivative was obtained from the reaction between a free‐base sapphyrin and dimethyl acetylenedicarboxylate (DMAD). The formation of the new compound involved a double aza‐Michael addition of two pyrrolic NH groups to a DMAD molecule, with the formation of a disubstituted ethano bridge. The NMR spectral data reveal a product with an unsymmetrical structure; DFT calculations provided support for a structure in which the ethano bridge links two adjacent pyrrole units. The present study provides a seemingly unprecedented example of an N,N′‐dinucleophile reacting with DMAD to form a heterocyclic compound in which the two N‐atoms are linked to the two sp3 carbon atoms derived from a substituted acetylene. Building a new bridge: A singular disubstituted ethano bridge on the sapphyrin scaffold is reported (see scheme), opening new synthetic routes in expanded porphyrin chemistry.