2026 Theses Doctoral

Expansion of Blue-Light Methodologies for the Formation of Reactive Radical Intermediates

Ramos, Mariah C.

Photochemistry has allowed for the advancement of many facets of organic synthesis as the reactive radical intermediates formed have applications spanning into chemical biology, therapeutics, polymers, and many more. While elegant work in blue-light mediated photoredox and metallaphotoredox has further advanced applications, high-energy paradigms still possess several drawbacks including light penetration, scalability, and functional group tolerance. Thus, harnessing blue-light for selective and efficient transformations capable of circumventing these issues is desirable.

Herein, we first utilize blue-light for the metallaphotoredox mediated desulfurative arylation of cysteine for introduction of unnatural amino acids. Upon excitation of an iridium photocatalyst, the activated cysteine can fragment to reveal a carbon-centered radical to enter a nickel-mediated cross-coupling. Next, high-energy light can be used to transform heavily prevalent pyridines to lesser explored 1,2-diazepines through a skeletal expansion upon excitation of pyridinium ylides. This work showed a diverse scope of products with late-stage compatibility as well as expanded upon established work to furnish a catalytic method. Lastly, blue-light is used for the selective β-alkylation of organosilanes through the use of an iridium photocatalyst and bromine radicals.