Direct photolysis of 4-tert-alkyl-1,4-dihydropyridines under blue-light irradiation for the generation of tertiary alkyl radicals

Herein, we disclose a direct photolysis approach for the generation of tertiary alkyl radicals from 4-tert-alkyl-1,4-dihydropyridines (DHPs) under blue LED irradiation, as exemplified in a photochemical Giese reaction. Radical generation occurs under mild conditions, does not require the use of exogenous photocatalysts or oxidants, and the Giese reaction is compatible with a range of 4-tert-alkyl-DHPs and Michael acceptors (23 examples, up to 86% yield). Mechanistic investigations reveal that the presence of base is crucial for radical generation.

Automated summary

A direct photolysis approach for generating tertiary alkyl radicals from 4-tert-alkyl-1,4-dihydropyridines (DHPs) under blue LED irradiation was disclosed in this study, showcasing its compatibility with a variety of substrates in a photochemical Giese reaction. The presence of base was found to be crucial for radical generation, and the reaction proceeded smoothly under mild conditions without the need for exogenous photocatalysts or oxidants, achieving yields of up to 86% in 23 examples.