Microwave-Enhanced Chemistry of Organotrifluoroborates

This dissertation contains a summary of the research efforts focused on the utiliza- tion of microwave technology in organoborate chemistry. More specifically, the cen- tral topic is focused on the chemistry of potassium organotrifluoroborate compounds that have recently attracted a lot of attention as useful reagents for diverse transfor- mations in organic synthesis such as, cross-coupling, homocoupling, as well as 1,2- and 1,4-addition reactions. The use of microwave radiation in these and other reac- tions is particularly appealing for improving and facilitating synthetic procedures by reducing reaction times, minimizing by-product formation, and increasing reaction yields. In this dissertation, we combine microwave technology and organotrifluorob- orate chemistry to develop novel methodologies in organic synthesis. As an example, we developed microwave-assisted hydrolysis of organotrifluoroborates under mild con- ditions using aluminum oxide as a fluorophile and water as a solvent. The procedure was then applied to a variety of organotrifluoroborates, demonstrating the general- ity of the approach. The advantage of this method is that it offers fast, clean, and environmentally friendly conversion of organotrifluoroborates to the corresponding boronic acids. We also investigated and improved the palladium-catalyzed Suzuki- Miyaura cross-coupling reaction of alkynyltrifluoroborates. Our method provides a copper-free alternative to the Sonagoshira coupling reaction with the benefit of very low catalyst loading and a short reaction time. Work on symmetrical biaryls, widely encountered in natural products and medicinal chemistry, led to the development of an efficient method for the synthesis of these compounds through homocoupling reactions of potassium organotrifluoroborates. Here, the use of microwave radiation and ligandless palladium catalysts provides a rapid and effective access to a variety of symmetrical biaryl compounds. Finally, we describe our efforts in surveying new applications of organoborates as alternatives to organoboranes compounds for C-C bond formation. The former are more stable than organoboranes and could display interesting chemical features under microwave activation.