The First Synthesis of 2,2′:5′,2-Terthiazole

2,2':5',2 ''-Terthiazole, a previously unknown terthiazole isomer, was prepared by copper-mediated oxidative coupling of 2-lithiothiazole. The yield was improved in the presence of equimolar 2,2'-bithiazole. The 5,5 ''-positions were cleanly lithiated by lithium diisopropylamide, which demonstrates its potential in the extension of pi-systems.