Cerium Photoredox-Catalyzed Ring Expansion of Cyclic Allylic Alcohols
Abstract
Medium-sized aliphatic rings are underrepresented in drug discovery despite their advantageous balance of rigidity and flexibility. Existing synthetic limitations hinder broader exploration of this valuable chemical space. This work presents a general and efficient method for the one- and two-carbon ring expansion of 5- and 6-membered allylic alcohols to larger cyclic ketones using cerium-based photoredox catalysis. Employing ligand-to-metal charge transfer (LMCT) activation, a dual catalytic system featuring Ce(OTf)3 and 9,10-diphenylanthracene (DPA) enables selective generation of alkoxyl radicals under mild conditions. A hydrogen atom transfer (HAT) catalyst, (TRIPS)2, is critical for productive C–C bond formation and radical termination. The method tolerates various nitrogen-protecting groups, vinyl substitutions, and ring systems, including bridged and fused frameworks, affording 7- and 8-membered ketones in moderate to excellent yields (38–98%). Notably, expansion to challenging [5.2.1] bicyclic and fused benzannulated scaffolds is demonstrated. This strategy offers a divergent and synthetically accessible route to sp3-rich, conformationally diverse drug-like scaffolds from simple precursors.
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BibTeX
@misc{obrien2026cerium,
title = {{Cerium Photoredox-Catalyzed Ring Expansion of Cyclic Allylic Alcohols}},
author = {Tegan E. O’Brien and Vamika Kaushal and Avery O. Morris and Louis Barriault},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15010888/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010888/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Cerium Photoredox-Catalyzed Ring Expansion of Cyclic Allylic Alcohols
AU - Tegan E. O’Brien
AU - Vamika Kaushal
AU - Avery O. Morris
AU - Louis Barriault
PY - 2026
DA - 2026/10/22
PB - ChemRxiv
DO - 10.26434/chemrxiv.15010888/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010888/v1
AB - Medium-sized aliphatic rings are underrepresented in drug discovery despite their advantageous balance of rigidity and flexibility. Existing synthetic limitations hinder broader exploration of this valuable chemical space. This work presents a general and efficient method for the one- and two-carbon ring expansion of 5- and 6-membered allylic alcohols to larger cyclic ketones using cerium-based photoredox catalysis. Employing ligand-to-metal charge transfer (LMCT) activation, a dual catalytic system featuring Ce(OTf)3 and 9,10-diphenylanthracene (DPA) enables selective generation of alkoxyl radicals under mild conditions. A hydrogen atom transfer (HAT) catalyst, (TRIPS)2, is critical for productive C–C bond formation and radical termination. The method tolerates various nitrogen-protecting groups, vinyl substitutions, and ring systems, including bridged and fused frameworks, affording 7- and 8-membered ketones in moderate to excellent yields (38–98%). Notably, expansion to challenging [5.2.1] bicyclic and fused benzannulated scaffolds is demonstrated. This strategy offers a divergent and synthetically accessible route to sp3-rich, conformationally diverse drug-like scaffolds from simple precursors.
ER -