C‐C‐Fragmentierung: Herkunft und jüngste Anwendungen

Abstract

Sechzig Jahre sind vergangen, seit Eschenmoser und Frey den Archetyp der C‐C‐Fragmentierung beschrieben. Rasch folgten neue Fragmentierungen und mehrere Varianten des Originals. Viele dieser Variationen, einschließlich der Beckmann‐, Grob‐, Wharton‐, Marshall‐ und der Eschenmoser‐Tanabe‐Fragmentierungen, sowie weiteren, wurden im Laufe der Jahre in Übersichten besprochen, eine genaue Untersuchung des Ursprungs von Fragmentierungen steht aber noch aus. Vor kurzem tauchten neue nützliche Methoden auf, insbesondere Fragmentierungen, die zu Alkinen und Allenen führen, und solche Reaktionen wurden auf eine Reihe an komplexen Leitmotiven und Naturstoffe angewendet. Dieser Aufsatz verfolgt die Entwicklung der Fragmentierungen und bietet eine Zusammenfassung der Methoden, Anwendungen und neue Einblicke in heterolytische C‐C‐Fragmentierungen der letzten zwanzig Jahre.

Photocatalytic Aerobic Oxidative Ring Expansion of Cyclic Ketones to Macrolactones by Cerium and Cyanoanthracene Catalysis

“…[6] Nevertheless,t he thermodynamically demanding C À Cb ond fragmentation step has typically required the use of forcing conditions. [7] Preeminently,the recent advancement in catalytic cleavage and functionalization of CÀCb onds, through transition metal catalysis [8] as well as photoredox catalysis, [9] have demonstrated vast potential to expand synthetic capacity of ring expansions. The b-scission of alkoxy radicals, [10] one of the wellestablished reaction pathways that traditionally relies on the use of various radical precursors,h as recently been incorporated into catalytic activations for effective CÀCb ond cleavage under mild and practical conditions.…”

Photocatalytic Aerobic Oxidative Ring Expansion of Cyclic Ketones to Macrolactones by Cerium and Cyanoanthracene Catalysis

“…[6] Nevertheless,t he thermodynamically demanding C À Cb ond fragmentation step has typically required the use of forcing conditions. [7] Preeminently,the recent advancement in catalytic cleavage and functionalization of CÀCb onds, through transition metal catalysis [8] as well as photoredox catalysis, [9] have demonstrated vast potential to expand synthetic capacity of ring expansions.…”

“…[6] Nevertheless,t he thermodynamically demanding C À Cb ond fragmentation step has typically required the use of forcing conditions. [7] Preeminently,the recent advancement in catalytic cleavage and functionalization of CÀCb onds, through transition metal catalysis [8] as well as photoredox catalysis, [9] have demonstrated vast potential to expand synthetic capacity of ring expansions. The b-scission of alkoxy radicals, [10] one of the wellestablished reaction pathways that traditionally relies on the use of various radical precursors,h as recently been incorporated into catalytic activations for effective CÀCb ond cleavage under mild and practical conditions.…”

Radical‐Promoted C−C Bond Cleavage: A Deconstructive Approach for Selective Functionalization

“…Historically, heterolytic fragmentations were the pioneering approaches to cleaving C(sp 3 )−C(sp 3 ) bonds . This chemistry was started in the 1950s by Eschenmoser, [6] and later followed by Grob .…”