@Article{IPB-1453, author = {Welsch, S. J. and Kalinski, C. and Umkehrer, M. and Ross, G. and Kolb, J. and Burdack, C. and Wessjohann, L. A.}, title = {{Palladium and copper catalyzed cyclizations of hydrazine derived Ugi products: facile synthesis of substituted indazolones and hydroxytriazafluorendiones}}, year = {2012}, pages = {2298-2301}, journal = {Tetrahedron Lett.}, doi = {10.1016/j.tetlet.2012.02.095}, volume = {53}, abstract = {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 α-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.} }