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.