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Oxidative Biaryl Coupling of Thiophenes and Thiazoles with Arylboronic Acids through Palladium Catalysis: Otherwise Difficult C4-Selective C[BOND]H Arylation Enabled by Boronic Acids

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  • This work was financially supported by a Grant-in-Aid for Scientific Research from MEXT and JSPS (Japan). We thank Dr. Yasutomo Segawa for his help in the X-ray crystal-structure analysis. S.K. thanks the International Research Training Group Münster/Nagoya for support. K.U. thanks JSPS for a predoctoral fellowship.

Abstract

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It adds up to 4! Thiophenes and thiazoles can be arylated in the 4- rather than the expected 5-position in a new C[BOND]H functionalization reaction (see scheme; TEMPO: 2,2,6,6-tetramethylpiperidine-N-oxyl). The boronic acid proved to be the key to achieving the otherwise difficult C4 selectivity. The method was applied to a concise synthesis of a key pharmacological structure with potential for treatment of Alzheimer's disease.

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