Copper-Catalyzed C-O and C-S Cross-Coupling Routes to Benzoxazoles and -thiazoles

Significance

CuI-catalyzed intramolecular C-O and C-S coupling reactions of ortho-haloanilides into benzoxazoles and benzothiazoles, respectively, are described. Several N,N′-, N,O-, and O,O′-chelating ligands were tested. 1,10-Phenan­throline showed the best functional group tolerence and gave generally excellent yields. The reaction was successfully carried out for a variety of R¹-substituted derivatives and especially good yields are observed for R¹ = strong electron-withdrawing aryl, 2-alkyl, 2-benzyl, and unsaturated ­systems. Limitations are observed for starting ­materials bearing additional carbonyl and amino acid containing R¹ groups. Furthermore, excellent yields of benzothiazoles with R¹ = Ph and R¹ = 4-MeOC₆H₄ were obtained.