Copper-Catalyzed [3 + 2] Annulation of O-Acyl Oximes with p-Hydroquinones for the Synthesis of 5-Hydroxyindoles.

A copper-catalyzed [3 + 2] annulation of O-acyl oximes with 2-electron-withdrawing group substituted p-hydroquinones for the efficient synthesis of polysubstituted 5-hydroxyindoles is developed. Further intramolecular cyclization leads to the concise and rapid construction of several kinds of 3,4- and 4,5-fused polycyclic indoles.

Copper-Catalyzed [3 + 2] Annulation of O-Acyl Oximes with 4-Sulfonamidophenols for the Synthesis of 5-Sulfonamidoindoles and 2-Amido-5-sulfonamidobenzofuran-3(2H)-ones.

A copper-catalyzed [3 + 2] annulation of O-acyl oximes with 4-sulfonamidophenols is developed. The advantage of this method lies in the concurrent double activation of two substrates to form nucleophilic enamines and electrophilic quinone monoimines. The substituent on the α-carbon of O-acyl oxime determines two different reaction pathways, thereby leading to the selective generation of 5-sulfonamidoindoles and 2-amido-5-sulfonamidobenzofuran-3(2H)-ones.