Selective photocatalytic functionalization of diamondoids and iron-catalyzed hydrogen atom transfer of aldehydes

Organic chemistry is defined as the study of carbon-containing molecules, including information about their structures and properties as well as chemical reactions to install different groups. Frequently, in organic molecules, carbon can be found bound to hydrogen, oxygen, nitrogen, and halogen (F, Cl, Br, I) atoms. Among these types of bonds, modification of carbonhydrogen (C–H) bonds is particularly difficult due to their high bond strengths, but is attractive to the field, with applications in medicine and materials.

Diamondoids are a class of caged compounds with strong C–H bonds. The smallest diamondoids, adamantane and diamantane, have applications in medicine and materials. An additional challenge for these types of molecules is not only the strength of their C–H bonds, but also the number of unique positions that can be modified. Adamantane has two unique positions whereas diamantane has three unique positions. As such, determining a method that would allow the selective modification of one position versus another is attractive, but difficult. Adamantane is the most featured diamondoid due to its commercial availability, and fewer reactions can be found with higher diamondoids. Of the methods that do exist with higher diamondoids, most result in mixtures of products, with selected examples summarized in Chapter 1. In Chapter 2, our group reported a method to use an organic catalyst to preferentially modify one position to form C–C and C–N bonds.

Amides, esters, and ketones are all functional groups that have significant utility in biological, medicinal, and materials applications. Classical methods to prepare these functional groups from aldehydes require three steps, each with the potential of requiring extensive purification. In Chapter 4, I describe novel methods by which aldehydes are converted to these functional groups through modification of the slightly weaker C–H bond with an inexpensive iron catalyst and lower energy light. This approach decreases the number of synthetic and purification steps needed to prepare these groups. Literature examples demonstrate multiple methods of activating this particular C–H using a variety of different reagents and catalysts, some of which are expensive. Selected examples are described in Chapter 3.

In summary, our group’s research focuses on the ability to modify less reactive C–H bonds in underreported higher diamondoids and aldehydes under visible light conditions. These molecules and their products exhibit potential applications in medicine and materials. These projects expand on existing literature in two ways. The first project provides methods to preferentially modify organic molecules with multiple distinct positions. The second project provides a new and shorter synthesis to prepare amides, esters, and ketones with an inexpensive iron catalyst and lower energy light.