AgI-Catalysed C–H Activation of (Arene)Cr(CO)3 Complexes

Abstract

AgI salts are extensively used as additives in transition metal-catalysed C–H functionalisation reactions. These additives are employed primarily as oxidants, as halide abstractors, or to promote decarboxylation, but often have additional, unexpected consequences on reactivity and regioselectivity. This thesis explores the role AgI salts play in C–H activation, particularly of electron deficient arenes. The introduction details reported examples of biaryl formation via C–H functionalisation which employ AgI additives, with the effects of these additives being explored. The first experimental chapter details a mechanistic investigation into the Pd-catalysed direct arylation reaction between iodoarenes and (fluoroarene)Cr(CO)3 complexes. Experimental evidence that a AgI carboxylate ligated by PPh3 is performing C–H activation in this system is described. Deuteration studies on other electron-deficient arenes suggest that this effect may be somewhat general. The thesis then details a one-pot direct arylation-cyclisation reaction which enables the construction of medium-sized rings from two separate molecules in one synthetic step. The methodology uses the activating properties of binding to Cr(CO)3 to enable both C–H activation and nucleophilic aromatic substitution to occur in high yields. Rings with between 6 and 10 members can be formed. Finally, a Pd/Ag co-catalysed direct arylation reaction between bromoarenes and (fluoroarene)Cr(CO)3 compounds is described. This uses the insight gained in the mechanistic studies to develop the first direct arylation reaction using haloarenes to incorporate catalytic quantities of AgI salts.

Date of Award	1 Aug 2018
Original language	English
Awarding Institution	The University of Manchester
Supervisor	David Leigh (Supervisor) & Igor Larrosa (Supervisor)