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Ring-Forming and Ring-Cleaving Reactions of Oxabenzonorbornadiene Derivatives

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Title: Ring-Forming and Ring-Cleaving Reactions of Oxabenzonorbornadiene Derivatives
Author: Koh, Samuel
Department: Department of Chemistry
Program: Chemistry
Advisor: Tam, William
Abstract: A novel intramolecular ring-opening reaction of oxabenzonorbornadienes tethered with C1-aryl halides has been disseminated. Ring-opening of these compounds was investigated using palladium and nickel catalysts to form fused tetracyclic frameworks. Conditions under palladium catalysis were found to synthesize dehydrated naphthalene products in excellent yield and selectivity. On the other hand, nickel-catalyzed protocols allowed for the selective syntheses of both 1,2-dihydronaphthalen-1-ol and naphthalene products. Following this, a novel acid-catalyzed intramolecular ring-opening is described for C1-alcohol and acid tethered cyclopropanated oxabenzonorbornadienes. A general preference for the reaction to proceed through a ‘Type 3’ ring-opening over a ‘Type 2’ ring-opening was observed with alcohol tethers to form fused tricyclic frameworks containing a ring-expanded benzocycloheptene core. The final chapter discusses preliminary work on a nickel-catalyzed [2+2] cycloaddition between oxabenzonorbornadiene and alkynyl phosphonates. This procedure allows for the rapid synthesis of cyclobutenated phosphonate derivatives with excellent yields.
Date: 2020-08
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