Molecular Engineering of β-Substituted Oxoporphyrinogens for Hydrogen-Bond Donor Catalysis

Chahal, Mandeep K.; Payne, Daniel; Matsushita, Yoshitaka; Labuta, Jan; Ariga, Katsuhiko and Hill, Jonathan P. (2019). Molecular Engineering of β-Substituted Oxoporphyrinogens for Hydrogen-Bond Donor Catalysis. ChemRxiv

DOI: https://doi.org/10.26434/chemrxiv.9685481.v1

Abstract

A new class of bifunctional hydrogen-bond donor organocatalyst using oxoporphyrinogens with increased intramolecular hydrogen-bond donor distances is reported. Oxoporphyrinogens are highly non-planar rigid macrocycles containing a multiple hydrogen bond forming binding site. In this work we report the first example of non-planar OxPs as hydrogen-bond donor catalysts. The introduction of β-substituents is key to the catalytic activity and the catalysts are able to catalyze 1,4-conjugate additions and sulfa-Michael additions, as well as, Henry and aza-Henry reactions at low catalyst loadings (≤ 1 mol%) under mild conditions. Preliminary mechanistic studies have been carried out and a possible reaction mechanism has been proposed based on the bi-functional activation of both substrates through hydrogen-bonding interactions.