Irradiation-Induced Heck Reaction of Unactivated Alkyl Halides at Room Temperature

• Published in: Journal of the American Chemical Society Vol. 139; no. 50; pp. 18307 - 18312
• Main Authors: Wang, Guang-Zu, Shang, Rui, Cheng, Wan-Min, Fu, Yao
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 20.12.2017; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Multidisciplinary; Physical Sciences; Science & Technology; CATALYSIS; CROSS-COUPLING REACTIONS; PD; COMPLEXES; ARYL; SUBSTITUTION-REACTIONS; BROMIDES
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.7b10009

The palladium-catalyzed Mizoroki–Heck reaction is arguably one of the most significant carbon–carbon bond-construction reactions to be discovered in the last 50 years, with a tremendous number of applications in the production of chemicals. This Nobel-Prize-winning transformation has yet to overcome the obstacle of its general application in a range of alkyl electrophiles, especially tertiary alkyl halides that possess eliminable β-hydrogen atoms. Whereas most palladium-catalyzed cross-coupling reactions utilize the ground-state reactivity of palladium complexes under thermal conditions and generally apply a single ligand system, we report that the palladium-catalyzed Heck reaction proceeds smoothly at room temperature with a variety of tertiary, secondary, and primary alkyl bromides upon irradiation with blue light-emitting diodes in the presence of a dual phosphine ligand system. We rationalize that this unprecedented transformation is achieved by utilizing the photoexcited-state reactivity of the palladium complex to enhance oxidative addition and suppress undesired β-hydride elimination.