Pincer-ligated catalysts for borylation of alkynes

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The Chemical Catalysis Program supports the efforts of Professor Oleg V. Ozerov of Texas A&M University Main Campus to explore the potential of a new reaction recently discovered in the investigator's laboratory: dehydrogenative borylation of terminal alkynes (DHBTA). DHBTA is catalyzed by select iridium pincer complexes and converts terminal alkynes directly into alkynylboronates under mild conditions and with excellent selectivity. Alkynylboronates are very attractive building blocks in organic chemistry that can be used as either sources of the alkynyl group in coupling reactions or as alkynes in various addition and cycloaddition reactions. The latter set of reactions leads to the formation of new compounds with otherwise difficult to access carbon-boron bonds that can be used for further elaboration into more complex molecules. This research combines efforts in the design of new pincer ligands and their metal complexes, exploration of the mechanism and scope of DHBTA, and demonstration of the utility of alkynylboronates in alkyne-alkyne coupling to enynes and in Pauson-Khand synthesis of borylated cyclopentenones. Prof. Ozerov and his research group broaden the impact of their research activities via collaborations with researchers at primarily undergraduate institutions and outside of the US, through involvement of undergraduate students in research at Texas A&M, as well as through outreach to local high schools. The molecular assembly of high-value organic chemicals in the chemical and pharmaceutical industries often relies on catalysis by transition metal compounds. This research represents a new approach to using well-defined, molecular transition metal complexes to catalyze the formation of compounds with carbon-boron bonds. Organic compounds containing carbon-boron bonds are extremely versatile as building blocks in the synthesis of complex organic structures. This project provides new fundamental knowledge about the design and operation of successful transition metal catalysts on the molecular level, explores select uses of the newly accessible building blocks in synthesis, and provides training to a diverse array of students in state-of-the-art chemistry of transition metals and, most importantly, in the art of critical thinking and solving scientific problems.