Palladium and copper catalyzed cyclizations of hydrazine derived Ugi products: facile synthesis of substituted indazolones and hydroxytriazafluorendiones

Indazolones are medicinally relevant targets. Herein we disclose an improved synthesis to N'-(acetamido-2-yl)substituted indazolones with four points of diversity introduced by Ugi-[M]-amination and -amidation. The ring closure can be achieved by either conventional palladium catalysis or with a ligandless copper protocol. When alpha-unbranched isocyanides were employed the sole cyclization products of the copper catalyzed reactions are the hitherto undescribed 2-hydroxy-3H-3,4a,9a-triaza-fluorene-4,9-diones. (C) 2012 Elsevier Ltd. All rights reserved.