Oxidative biaryl coupling of thiophenes and thiazoles with arylboronic acids through palladium catalysis: Otherwise difficult C4-selective C-H arylation enabled by boronic acids

(Chemical Equation Presented) It adds up to 4! Thiophenes and thiazoles can be arylated in the 4- rather than the expected 5-position in a new C-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 Alzheimers disease.