Intramolecular Pd(0)-catalyzed reactions of (2-iodoanilino)-aldehydes: a joint experimental-computational study.

An extensive joint experimental-computational density functional theory (DFT) study has been carried out to gain insight into the factors that control the chemoselectivity (i.e., acylation vs α-arylation reaction) of palladium-catalyzed cyclizations of (2-iodoanilino)-aldehydes. To this end, the nature of the tethers joining the aniline nitrogen and the aldehyde moiety, different palladium precatalysts and reaction conditions (base and temperature), as well as different additives (mono- and bidendate ligands) has been explored. The adequate selection of these variables allows for the control of the selectivity of the process. Thus, (2-iodoanilino)-aldehydes generally lead to the formation of nucleophilic addition derived products when Cs(2)CO(3)/Et(3)N is used as base. In contrast, the use of stronger bases like K(t)OBu (in the presence of PhOH) mainly forms α-arylation reaction products. The different reaction pathways leading to the experimentally observed reaction products have been studied by means of computational tools.