Generation and Trapping of Highly Strained Reactive Intermediate: Ethyl 1,2-Cyclohexadienecarboxylate

Abstract

Highly strained reactive intermediates can initiate chemical reactions and afford unique products. Cyclic allenes are important examples of such intermediates. Within the cyclic allene family, 1,2-cyclohexadiene was intensively studied over the years. In this dissertation, the investigation of developing practical methodology to generate and trap 1-substituted-1,2-cyclohexadiene will be detailed. In Chapter 1, a brief history of strained reactive intermediates family is discussed, including benzynes and cycloalkynes, in addition to the development of 1,2-cyclohexadiene chemistry. The discovery of 1,2-cyclohexadiene, the study on its structure and properties and some known 1-substituted cyclohexa-1,2-dienes will be discussed. A brief introduction of existing methods to generate and trap 1-subsituted cyclohexa-1,2-diene is described at the beginning of Chapter 2. Investigation of practical generation and trapping of ethyl 1,2-cyclohexadienecarboxylate, including systematic optimization of reaction conditions and exploration of the reaction scopes, is then discussed. The attempt to investigate the mechanism of newly discovered [2+2] cycloaddition between ethyl 1,2-cyclohexadienecarboxylate and alkynes will also be included.