Cerium and bismuth catalysis hand in hand—Synthesis of a eight-membered ring lactam library

Cerium-catalyzed C–C coupling of 1,3-dicarbonyl compounds with styrene derivatives and oxygen yielded compounds with a 1,4-dicarbonyl moiety after base induced Kornblum–DeLaMare fragmentation. Further conversion of these 1,4-diketones with primary amines in a bismuth-catalyzed reaction gave eight-membered ring lactams, which are a new and promising molecular scaffold for medicinal chemistry. Further derivatization was achieved by saponification of esters to their corresponding carboxylic acids and followed by amidation with primary amines with a coupling reagent. We furthermore investigated the synthesis of cogeners with an additional O, S, or N atom in the eight-membered ring, thus extending the diversity of our scaffold.

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