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Chemoselective and Regioselective Oxidative Couplings of Aromatic Heterocycles

Chemoselective and Regioselective Oxidative Couplings of Aromatic Heterocycles. Brenton DeBoef, Department of Chemistry, University of Rhode Island, Kingston, RI 02881. Summary. Classification of Non-Directed Oxidative Coupling Reactions.

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Chemoselective and Regioselective Oxidative Couplings of Aromatic Heterocycles

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  1. Chemoselective and Regioselective Oxidative Couplings of Aromatic Heterocycles Brenton DeBoef, Department of Chemistry, University of Rhode Island, Kingston, RI 02881 Summary Classification of Non-Directed Oxidative Coupling Reactions Class I (low pH) Class III (buffered) Class IV (high pH) Oxidative coupling is a powerful method by which two unfunctionalized substrates can be directly coupled to form a new C-C bond. We have hypothesized that the variety of reaction conditions that exist for the oxidative formation of biaryl C-C bonds from unfunctionalized arenes may be classified according to their relative pH. A systematic study involving benzofuran substrates has validated this hypothesis. The resulting rubric can be applied to predict the best conditions for the oxidative coupling of a given substrate. The data suggests that high pH reactions proceed via a proton abstraction mechanism, while those at low pH proceed via electrophilic palladation. Oxidative Coupling as an Efficient Method for Synthesizing Biaryls Class I : DeBoef, et.al. Org. Lett., 2007, 9, 3137–3139. Class II: Fagnouet al. J. Org. Chem., 2008, 73 , 5022–5028. (Incompatible with intermolecular reaction) Class III: DeBoef, et.al. Org. Lett., 2007, 9, 3137–3139. Fagnouet al. Science 2007, 316, 1172-1175. Fagnouet al.J. Am. Chem. Soc.2007, 129, 12072–12073. Class IV: DeBoef, et al.Tetrahedron Lett., 2008, 49, 4050-4053. Mechanistic Insight Need for Milder Conditions Acknowledgements This work was supported by the National Science Foundation (CAREER 0847222), the Petroleum Research Fund (47019-G1) and a Pilot/Feasibility Grant from the Rhode Island INBRE Program (NIH-NCRR P20RR016457).

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