Abstract
Organic electrochemistry has become a useful and environmentally friendly alternative to traditional organic synthesis. Electrochemistry provides a tool with which electrons can be selectively introduced or removed from an organic molecule, allowing for the reversal of functional group polarity. This allows for the coupling of two electrophiles or two nucleophiles in ways that would otherwise be impossible to accomplish. The electrohydrocyclization (EHC) and elecroreductive cyclization (ERC) reactions to form carbocyclic rings have been used as the key step in the synthesis of several anti-cancer compounds and natural products. The direct, unmediated EHC was first discovered by Baizer in the 1960’s and then developed into the mediated EHC reaction by Miranda, Wade, and Little in the early 2000’s. Metal-salen compounds can serve as excellent electrochemical mediators in these reactions, resulting in a chemoselective process due to the reaction being run at a more positive potential than unmediated reactions. In addition, since only a catalytic amount of mediator is needed, the resultant chemical waste is greatly reduced, resulting in a more environmentally friendly reaction. This thesis develops upon the unmediated and mediated EHC reaction by exercising a new class of heterogeneous v electrocatalysts to mediate the EHC reaction while remaining in the solid phase. Specifically, this research developed two types of solid-supported catalysts. Two approaches were studied: anchoring the electrocatalyst to a solid-phase polymer (Merrifield resin) and encapsulation of Ni(salen) in porous zeolite Y. The primary benefit of a heterogeneous catalyst is the drastic improvement of reaction work-up and purification. Furthermore the heterogeneous catalysts can be washed and re-used. The EHC reaction was performed with several heterogeneous and homogeneous catalysts to allow for comparison. The cis/trans ratio results from each reaction did not show drastic differences between each catalyst. The EHC reaction with the heterogeneous catalyst resulted in higher yields over the homogeneous catalysts.