Transition metal catalysis has been instrumental for the synthesis of molecules that are used by society, particularly for active pharmaceutical ingredients and other medicinally relevant compounds. Among reactions that use these catalysts, cross coupling methods that use palladium catalysts have been significantly transformative for many areas of science. Despite concerns about the toxicity and sustainability of palladium- based catalysts, these reactions are commonplace in the pharmaceutical industry ? both in medicinal and process chemistry ? which is likely a consequence of their robustness, predictability and scalability. Although many types of cross coupling methods are available, the Suzuki reaction that couples organoboron nucleophiles with halide and pseudohalide electrophiles is the most commonly used. This fact can be attributed to the beneficial characteristics that organoboron compounds have over nucleophiles used in other cross coupling reactions. The ubiquity of Suzuki cross coupling in organic chemistry has made methods for the synthesis of organoboron compounds particularly valuable. Of these methods, only the Miyaura borylation has been directly combined with Suzuki cross coupling in a one-pot transformation that uses a single Pd catalyst. This proposal targets the connection of two classes of cobalt-catalyzed reactions: borylation ? specifically arene C?H borylation and alkene/alkyne hydroboration ? and Suzuki cross coupling. First, the mechanism of a terpyridine cobalt-catalyzed Suzuki cross coupling will be investigated, which will inform catalyst design strategies that aim to address current limitations of the methodology. The resulting improved protocol for cobalt-catalyzed Suzuki cross coupling will then be merged with cobalt-catalyzed borylation reactions. The net result of this combination will be a single cobalt catalyst for the direct arylation and alkylation of unsaturated hydrocarbon substrates. Particular emphasis will be placed on the advantages that the proposed research has over existing approaches.
This proposal describes new cobalt-catalyzed methods for carbon-carbon bond formation. A single cobalt catalyst is proposed to promote borylation ? specifically arene C?H borylation and alkene/alkyne hydroboration ? and subsequent Suzuki cross coupling in a one-pot transformation. This sequence of reactions enables the direct arylation and alkylation of unsaturated hydrocarbon substrates.
