14. Understanding Heteroatom Effect on Ullmann Copper-Catalyzed Cross-Coupling of X-Arylation (X = NH, O, S) Mechanism

DIEGO ANDRADA; SILVIA M. SORIA CASTRO; DANIEL A. CAMINOS; JUAN E. ARGÜELLO; ALICIA B. PEÑÉÑORY

Catalysts

MDPI (Multidisciplinary Digital Publishing Institute)

Lugar: Basel; Año: 2017 vol. 7 p. 1 - 1

2073-4344

ensity Functional Theory (DFT) calculations have been carried out in order to unravelthe governing reaction mechanism in copper‐catalyzed cross‐coupling Ullmann type reactionsbetween iodobenzene (1, PhI) and aniline (2‐NH, PhNH2), phenol (2‐O, PhOH) and thiophenol(2‐S, PhSH) with phenanthroline (phen) as the ancillary ligand. Four different pathways for themechanism were considered namely Oxidative Addition?Reductive Elimination (OA‐RE), σ‐bondMetathesis (MET), Single Electron Transfer (SET), and Halogen Atom Transfer (HAT). Our resultssuggest that the OA‐RE route, involving CuIII intermediates, is the energetically most favorablepathway for all the systems considered. Interestingly, the rate‐determining step is the oxidativeaddition of the phenyl iodide to the metal center regardless of the nature of the heteroatom. Thecomputed energy barriers in OA increase in the order O < S < NH. Using the Activation Strain Model(ASM) of c