UC San Diego

Carbenes were thought to be un-isolable chemical species until the isolation of the first phosphinosilyl carbene in 1988 and the subsequent report of the first N-heterocyclic carbene (NHC) in 1991. Since then, carbenes with different electronic and steric properties have been synthesized and used in applications like metal catalysis, organocatalysis, medicine, and optical materials. The more carbenes are investigated, the more fortuitous and paradigm-challenging discoveries are made, advancing the collective knowledge of the structure and reactivity of main group elements. These discoveries are also relevant outside of main group research, often powering the development of more advanced or efficient technologies. As a result, carbene research is valuable. In this dissertation, an NHC’s electronic properties, and therefore its reactivity, was found to be closely dependent on its carbene angle, however, increasing carbene angle was correlated to more steric congestion around the carbene center, introducing a confounding factor that should be carefully considered by future researchers wishing to use saturated ring expanded NHCs. Additionally, this dissertation reports on the synthetic progress towards a novel carbene that aims to combine the excellent leaving group properties of Enders-type carbenes with the highly ambiphilic electronic properties of cyclic (alkyl) (amino) carbenes to create a new carbene organocatalyst. In the process of developing this novel carbene, a new framework for organic reductants was serendipitously discovered. Upon a one electron oxidation of the bipyrazolylidene framework, an air-persistent radical cation is generated.