C–H Activation with Photoredox Catalysis

Spin-Forbidden Excitation Enables Infrared Photoredox Catalysis

10.26434/chemrxiv.12124215.v1 ◽

2020 ◽

Author(s):

Tomislav Rovis ◽

Benjamin D. Ravetz ◽

Nicholas E. S. Tay ◽

Candice Joe ◽

Melda Sezen-Edmonds ◽

...

Keyword(s):

Excited State ◽

Ground State ◽

Intersystem Crossing ◽

Photoredox Catalysis ◽

Infrared Irradiation ◽

Triplet Excitation ◽

New Family ◽

Ir Light

We describe a new family of catalysts that undergo direct ground state singlet to excited state triplet excitation with IR light, leading to photoredox catalysis without the energy waste associated with intersystem crossing. The finding allows a mole scale reaction in batch using infrared irradiation.

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Generation of Phosphoranyl Radicals via Photoredox Catalysis Enables Voltage–Independent Activation of Strong C–O Bonds

10.26434/chemrxiv.6349253 ◽

2018 ◽

Author(s):

Erin Stache ◽

Alyssa B. Ertel ◽

Tomislav Rovis ◽

Abigail G. Doyle

Keyword(s):

Carboxylic Acids ◽

Functional Groups ◽

Single Step ◽

Direct Access ◽

Photoredox Catalysis ◽

Acyl Radical ◽

Synthetic Strategy ◽

Acyl Radicals ◽

Benzyl Radicals ◽

Aliphatic Carboxylic Acids

Alcohols and carboxylic acids are ubiquitous functional groups found in organic molecules that could serve as radical precursors, but C–O bonds remain difficult to activate. We report a synthetic strategy for direct access to both alkyl and acyl radicals from these ubiquitous functional groups via photoredox catalysis. This method exploits the unique reactivity of phosphoranyl radicals, generated from a polar/SET crossover between a phosphine radical cation and an oxygen centered nucleophile. We first show the desired reactivity in the reduction of benzylic alcohols to the corresponding benzyl radicals with terminal H-atom trapping to afford the deoxygenated product. Using the same method, we demonstrate access to synthetically versatile acyl radicals which enables the reduction of aromatic and aliphatic carboxylic acids to the corresponding aldehydes with exceptional chemoselectivity. This protocol also transforms carboxylic acids to heterocycles and cyclic ketones via intramolecular acyl radical cyclizations to forge new C–O, C–N and C–C bonds in a single step.

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Regioselective C3-H Trifluoromethylation of 2H-Indazole Under Transition-Metal-Free Photoredox Catalysis

10.26434/chemrxiv.7796603.v1 ◽

2019 ◽

Cited By ~ 1

Author(s):

Arumugavel Murugan ◽

Venkata Nagarjuna Babu ◽

Nagaraj Sabarinathan ◽

Sharada Duddu. S

Keyword(s):

Transition Metal ◽

Visible Light ◽

Practical Approach ◽

Hypervalent Iodine ◽

Radical Mechanism ◽

Photoredox Catalysis ◽

Metal Free

Here we report a visible-light-promoted metal-free regioselective C3-H trifluoromehtylation reaction that proceeds via radical mechanism and which supported by control experiments. The combination of photoredox catalysis and hypervalent iodine reagent provides a practical approach for the present trifluoromethylation reaction and synthesis of a library of trifluoromethylated indazoles.

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