Cobalt‐Catalyzed Coupling of Alkyl Iodides with Alkenes: Deprotonation of Hydridocobalt Enables Turnover

Abstract

Completing the cycle: Cobalt complexes I and II were found to catalyze intramolecular alkyl Heck‐type coupling reactions of alkyl iodides to alkenes upon irradiation with visible light in the presence of a tertiary amine base. The use of base is key to the catalytic turnover. The compatibility of the method with a broad range of functional groups opens opportunities for synthesis.

Visible light-induced transition metal-catalyzed transformations: beyond conventional photosensitizers

“…7 In their follow-up report, the authors reported the full scope and mechanistic details of their novel photoinduced intramolecular alkyl Heck reaction (Scheme 3). 8 Exo -trig cyclization of systems containing sensitive functionalities ( 8a–d ), such as amides, aldehydes, and heterocycles, reacted efficiently. Notably, substrates possessing usually reactive aryl-halides did not affect the outcome of the reaction ( 8d ).…”

Engaging unactivated alkyl, alkenyl and aryl iodides in visible-light-mediated free radical reactions

“…The groundstate neutral electron donors used by Murphy 14,15 and the alkyland stannyl-cobaloxime catalysts developed by Careirra 16 have successfully generated alkyl radicals from alkyl iodides. In addition, several new hydrogen atom donors have been introduced, such as N-heterocyclic carbene boranes 17 and water in the presence of Et 3 B 18 or Ti(III) salts 19 .…”

Discovery of Novel Synthetic Methodologies and Reagents during Natural Product Synthesis in the Post-Palytoxin Era

“…Because of the weak nature of the Co−Sn bond, Carreira and Weiss and coworkers 231 proposed that, when subjected to visible light, catalyst 212 and an alkyl iodide 214 would produce Ph 3 SnI and the cobalt−alkyl species 215. This alkyl−cobalt would then add to the olefin to produce adduct 216.…”

“…231 This novel cobalt-catalyzed intramolecular Heck-type coupling reaction of alkyl iodides and olefins was subsequently found to be broadly applicable and compatible with many functional groups such as amides, esters, and ethers (Scheme 51). 231 …”

“…The Ag(I) salts alone, Bu 4 NBH 4 , or commercially available Ag powder were also found to display no reactivity in the desired Cobalt-Catalyzed Heck-type Reaction a Applied as a General Methodology toward a Variety of Substrates b a Developed during the synthesis of daphmanidin E (210a). 230 b By Carreira and co-workers in 2011 231. …”