Iridium(I)-Catalyzed Intramolecular Cycloisomerization of Enynes: Scope and Mechanistic Course

NOTICE: This is the peer reviewed version of the following article: David F. Fernández, Catarina A. B. Rodrigues, Martín Calvelo, Moisés Gulías, José L. Mascareñas and Fernando López (2018), Iridium(I)-Catalyzed Intramolecular Cycloisomerization of Enynes: Scope and Mechanistic Course. ACS Catalysis, 2018, 8 (8), 7397–7402 [DOI: 10.1021/acscatal.8b02139]. This article may be used for non-commercial purposes in accordance with American Chemical Society Terms and Conditions for self-archivingWe report an Ir(I)-catalyzed cycloisomerization methodology that provides access to carbocyclic systems bearing exo-alkene moieties from alkynyl-equipped acyclic precursors. The method relies on the C–H activation of olefinic and (hetero)aromatic C(sp2)–H bonds, followed by an exocyclization to a tethered alkyne, and provides interesting cyclic diene products that are amenable of further elaboration. Importantly, DFT calculations suggests that, in contrast to related hydrocarbonations of alkenes in which either migratory insertions or C–C reductive eliminations have been suggested to be rate-determining, in our reactions, the energetic barrier of these steps is lower than that of the previous C–H activationThis work received financial support from the Spanish MINECO (Nos. SAF2016-76689-R, CTQ2016-77047-P, and CTQ2017-84767-P, as well as an FPI fellowship to D.F.F.), the Xunta de Galicia (Nos. ED431C 2017/19 and 2015-CP082, as well as Centro Singular de Investigación de Galicia accreditation 2016-2019 ED431G/09 and predoctoral fellowship to M.C.), the ERDF, ERC (Adv. Grant No. 340055) and the Orfeo-Cinqa network (No. CTQ2016-81797-REDC). Dr. Rebeca García-Fandiño is acknowledged for helpful suggestions on DFT studiesS

Iridium(I)-Catalyzed Intramolecular Cycloisomerization of Enynes: Scope and Mechanistic Course

We report an Ir(I)-catalyzed cycloisomerization methodology that provides access to carbocyclic systems bearing exo-alkene moieties from alkynyl-equipped acyclic precursors. The method relies on the C-H activation of olefinic and (hetero)aromatic C(sp)-H bonds, followed by an exocyclization to a tethered alkyne, and provides interesting cyclic diene products that are amenable of further elaboration. Importantly, DFT calculations suggests that, in contrast to related hydrocarbonations of alkenes in which either migratory insertions or C-C reductive eliminations have been suggested to be rate-determining, in our reactions, the energetic barrier of these steps is lower than that of the previous C-H activation.This work received financial support from the Spanish MINECO (Nos. SAF2016-76689-R, CTQ2016-77047-P, and CTQ2017-84767-P, as well as an FPI fellowship to D.F.F.), the Xunta de Galicia (Nos. ED431C 2017/19 and 2015-CP082, as well as Centro Singular de Investigación de Galicia accreditation 2016-2019 ED431G/09 and predoctoral fellowship to M.C.), the ERDF, ERC (Adv. Grant No. 340055) and the Orfeo-Cinqa network (No. CTQ2016-81797-REDC). Dr. Rebeca Garciá -Fandiño is acknowledged for helpful suggestions on DFT studies.Peer Reviewe