Unprecedented Double aza‐Michael Addition within a Sapphyrin Core

Abstract

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 sp(3) carbon atoms derived from a substituted acetylene.

Synthesis, Characterization, and Electrochemistry of Open‐Chain Pentapyrroles and Sapphyrins with Highly Electron‐Withdrawing meso‐Tetraaryl Substituents

“…[1] This macrocycle is an early member of the group of "expanded porphyrins" [2][3][4][5][6][7][8][9][10][11] and was first discovered in the early 1960s as ab yproduct in the synthesis of corroles. [12] Since then, sapphyrins have remained at opic of high interest, [13][14][15][16] in part because of their potential applicationsi nt he area of photodynamic therapy and their structurals imilarity to the well-known porphyrin and corrole macrocycles, [10,11,[17][18][19][20][21] and in part because of their unique properties as ar eceptor of neutraland anionic substrates. [22][23][24][25][26][27][28][29] Al arge number of studies have characterizedd ifferent sapphyrind erivatives, including b-alkylateds apphyrins, [30][31][32][33] coremodified sapphyrins with heteroatoms (O, S, or Se), [34][35][36][37][38][39][40][41][42][43]…”

“…This macrocycle is an early member of the group of “expanded porphyrins” and was first discovered in the early 1960s as a byproduct in the synthesis of corroles . Since then, sapphyrins have remained a topic of high interest, in part because of their potential applications in the area of photodynamic therapy and their structural similarity to the well‐known porphyrin and corrole macrocycles, and in part because of their unique properties as a receptor of neutral and anionic substrates …”