Organic Photoredox Catalysts for Visible Light-Driven Polymer and Small Molecule Synthesis
INTRODUCTION
Photoredox catalysis has become a powerful synthetic method, which can form Covalent bond under mild reaction conditions through light irradiation. Recently, researchers have developed organic photo redox catalysts for phenoxazine (P485533) and dihydrophenazine (P485532) through calculation and design, enabling them to exhibit photophysical and electrochemical properties related to photo redox catalysis. Specifically, they absorb visible light and have high molar absorptivity, redox reversibility, charge transfer excited state, long triplet state excited state lifetime and high triplet quantum yield.
Phenoxazine and dihydrophenazine derived compounds have been demonstrated in the application of photo redox catalyzed Atom transfer radical polymerization (ATRP) to control polymer formation and small molecule conversion (such as trifluoromethylation and double photo redox/nickel catalyzed C-N and C-S cross coupling). Through joint research and development with internationally renowned enterprises, Aladdin now provides organic photo oxidation reduction catalysts for benzoxazine and dihydrophenazine.
Figure 1. Phenoxazine (P485533) and dihydrophenazine (P485532) organic photoredox catalysts.
ADVANTAGES
• It can replace precious metal complexes, reduce the overall cost of catalyst use, and is sustainable in use.
• In a highly reduced excited state
• It shows properties that are important for photo redox catalysis: visible light absorption, high molar absorptivity, redox reversibility, charge transfer Excited state, long triplet Excited state lifetime and high triplet quantum yield
APPLICATIONS
Atom transfer radical polymerization (ATRP)
Atom transfer radical polymerization (ATRP) is an example of a reversible-deactivation radical polymerization. Like its counterpart, ATRA, or atom transfer radical addition, ATRP is a means of forming a carbon-carbon bond with a transition metal catalyst. Polymerization from this method is called atom transfer radical addition polymerization (ATRAP). As the name implies, the atom transfer step is crucial in the reaction responsible for uniform polymer chain growth. ATRP (or transition metal-mediated living radical polymerization) was independently discovered in 1995.
Trifluoromethylation
Trifluoromethylation in organic chemistry describes any organic reaction that introduces a trifluoromethyl group in an organic compound. Trifluoromethylated compounds are of some importance in pharmaceutical industry and agrochemicals. Several notable pharmaceutical compounds have a trifluoromethyl group incorporated: fluoxetine, mefloquine, Leflunomide, nulitamide, dutasteride, bicalutamide, aprepitant, celecoxib, fipronil, fluazinam, penthiopyrad, picoxystrobin, fluridone, norflurazon, sorafenib and triflurazin. A relevant agrochemical is trifluralin. The development of synthetic methods for adding trifluoromethyl groups to chemical compounds is actively pursued in academic research.
Dual photoredox/nickel C-N coupling
Dual photoredox/nickel C-S coupling
References
1. Du Y, Pearson RM, Lim C, Sartor SM, Ryan MD, Yang H, Damrauer NH, Miyake GM. 2017. Strongly Reducing, Visible-Light Organic Photoredox Catalysts as Sustainable Alternatives to Precious Metals. Chem. Eur. J.. 23(46):10962-10968. https://doi.org/10.1002/chem.201702926
2. Theriot JC, Lim C, Yang H, Ryan MD, Musgrave CB, Miyake GM. 2016. Organocatalyzed atom transfer radical polymerization driven by visible light. Science. 352(6289):1082-1086. https://doi.org/10.1126/science.aaf3935
3. Pearson RM, Lim C, McCarthy BG, Musgrave CB, Miyake GM. 2016. Organocatalyzed Atom Transfer Radical Polymerization Using N-Aryl Phenoxazines as Photoredox Catalysts. J. Am. Chem. Soc.. 138(35):11399-11407. https://doi.org/10.1021/jacs.6b08068
4. Lim C, Ryan MD, McCarthy BG, Theriot JC, Sartor SM, Damrauer NH, Musgrave CB, Miyake GM. 2017. Intramolecular Charge Transfer and Ion Pairing in N,N-Diaryl Dihydrophenazine Photoredox Catalysts for Efficient Organocatalyzed Atom Transfer Radical Polymerization. J. Am. Chem. Soc.. 139(1):348-355. https://doi.org/10.1021/jacs.6b11022