Metal-Salens As Catalysts In Electroreductive Cyclization and Electrohydrocyclization: Computational and Experimental Studies

The use of chiral Ni(II)-salen derivatives was examined in mediated electrohydrocyclization (EHC) reactions. Cyclic voltammetry established the existence of a catalytic current. Bulk electrolysis revealed a slight change in the diastereoselectivity of the cyclizations. Density functional theory (DFT) computational studies showed that Ni(II)-salen and Zn(II)-salen were the best metal-salens for electron transfer, while Co(II)-salen and Cu(II)-salen would likely be ineffective for this purpose. Electron transfer was both considerably more thermodynamically and kinetically (whether through an inner or outer sphere pathway) favorable with Ni(II)salen and Zn(II)-salen. Computational data also suggests Ni(II)-salen to be preferred for promoting inner sphere electron transfer, due in part to the ligand-centered reduction of Ni(II)-salen, and thus for affecting stereoselectivity in mediated EHC reactions. © 2013 The Electrochemical Society. [DOI: 10.1149/2.015307jes] All rights reserved.