Exploration of vinylcyclopropane radical cyclization-fragmentation, Indirect electroreductive cyclization and electrohydrocyclization using catalytic reduced nickel(II) salen, and, Mechanistic details of indirect electroreductive cyclization using catalytic reduced nickel(II) salen.

摘要

Chapter 1. Exploration of vinylcyclopropane radical cyclization-fragmentation. Monoradical vinylcyclopropane cyclization-fragmentation as a route towards carbocyclic eight-membered rings is presented. It was found that 6-exo-trig cyclization occurred as the predominant route instead of 7-endo-trig cyclization, due to entropic factors and positioning of a radical stabilizing electron withdrawing group. Changing position of the electron withdrawing group was not enough to entice 7-endo-trig cyclization.;Chapter 2. Indirect electroreductive cyclization and electrohydrocyclization using catalytic reduced nickel (II) salen. Efforts to achieve the electroreductive cyclization (ERC) and the electrohydrocyclization (EHC) reactions using catalytic nickel(II) salen are described. The transformations were achieved in yields ranging from 60 to 94%. The examples presented represent the first instances wherein a nickel salen complex has been used in this manner. Cyclic voltammetry was used to display the presence of a catalytic current.;Chapter 3. Mechanistic Details of Indirect Electroreductive Cyclization Using Catalytic Reduced Nickel(II) Salen. The mechanism of indirect electroreductive cyclization (ERC) reactions using catalytic nickel(II) salen was explored. Isolation of the intramolecular Michael addition product reflected the radical anion character of the reduced catalyst. Structural modification of the salen ligand resulted only in synthesis of the intramolecular Michael addition product and no ERC products. Attempted mediated ERC using nickel(II) cyclam resulted in no ERC products, indicating that when using nickel(II) salen the electron transfer occurred via an inner sphere electron transfer pathway.