The Zuo Lab at the School of Physical Science and Technology recently published details of their breakthrough method in the journal Angewandte Chemie-International Edition, titled “Photocatalytic C–C Bond Cleavage and Amination of Cycloalkanols by Cerium(III) Chloride Complex”. Dr. Guo Jingjing and Dr. Hu Anhua are co-first authors and Professor Zuo was the corresponding author.
Over the last 60 years, tremendous progress has been made in the area of organic synthesis, which has become the most transformative power in drug discovery. Although it’s said that nowadays, given enough time and resources, any desired molecule can be synthesized, to achieve that goal in a more efficient and economical pathway is still an unmet need in the pharmaceutical industry. The direct functionalization strategy of ubiquitous C–H and C–C bonds has been proven to be a promising solution to this challenge, and therefore has attracted significant research efforts. Due to the inertness of those bonds, precious transition metals and harsh conditions normally have to be employed to achieve effective transformations. Developing more sustainable catalysis system and affordable catalysts to cleavage and functionalize C–H and C–C bonds has become the research focus of the Zuo lab.
Over the last five years, photoredox catalysis has made tremendous progress towards selective C–H bond functionalizations. Nevertheless, regarding more challenging C–C bonds, breakthroughs have only been made recently with restricted substrates scope. Taking advantage of the luminescence properties of Ce(III) compounds and the highly oxidizing nature of Ce(IV) species, the Zuo lab has developed a general Ce(III) chloride-based photo catalyst system for the selective C–C bond cleavage/amination of unstrained cycloalkanols. A broad array of alcohols, including complex terpenols and sterols, have been demonstrated to undergo selective C–C bond scission/amination under very mild conditions. This method represents the first photocatalytic C–C bond cleavage and functionalization of secondary cycloalkanols. This operationally simple photoredox reaction utilizes easily accessible ingredients: commercial blue LEDs, the catalytic combination of CeCl3(an inexpensive, commonly used Lewis acid) and TBACl (a commonly used phase transfer catalyst).
This Ce(III) chloride-based photo catalyst represents a novel scaffold for photoredox catalysis. With its unique metal-centered photoexcitation and the broad oxidation-reduction potential scope, they are confident that more transformations taking advantage of this scaffold can be realized. The ease of simply mixing bench chemicals in situ, with no need for tedious synthesis of luminescent transition-metal complexes, will certainly be embraced by more practitioners of organic chemistry in the future development of additional photoredox reactions.
Figure 1 C–C bond cleavage and amination via Ce(III) photo catalyst
Figure 2 Dr. Guo JingJing (right) and Dr. Hu Anhua (left) in lab