Palladium‐Catalyzed Decarboxylative Heck‐Type Coupling of Activated Aliphatic Carboxylic Acids Enabled by Visible Light

Abstract The palladium‐catalyzed coupling reaction of N ‐hydroxyphthalimide esters and styrenes to deliver exclusively ( E )‐substituted olefins under irradiation with visible light is reported. This method tolerates N ‐hydroxyphthalimide esters derived from primary, secondary, tertiary as well as benzylic carboxylic acids. Notably, Pd(PPh 3 ) 4 is employed as an inexpensive palladium source and no addition of base or classical photocatalyst is required. Mechanistic studies suggest a light‐mediated single‐electron reduction of the activated acid by a photoexcited palladium(0) species to access alkyl radicals through decarboxylation.