Übergangsmetallvermittelte Spaltung von C‐C‐Einfachbindungen

Abstract

Schema 1. Beispiele fürfrühere Synthesen A) mit CC -Bindungsspaltung ohne Übergangsmetalle, B) mit übergangsmetallvermittelter Spaltung von CC -Einfachbindungen unter Bildung eines reaktiven metallorganischen Intermediats (Zwei-Elektronen-Reaktivität) und C) mit übergangsmetallvermittelter Spaltung von CC -Einfachbindungen unter Bildung eines reaktiven radikalischen Intermediats (Ein-Elektronen-Reaktivität). Cp = Cyclopentadienyl, DMPU = Dimethylpropylenharnstoff, Piv = Pivaloyl, TBS = tert-Butyldimethylsilyl, TIPS = Triisopropylsilyl.

Photoinduced C−O Bond Formation through C−C Bond Cleavage of Alcohols by Suppressing Alcohol Oxidation

“…On the other hand, methods for cleaving C−C single bonds, which could open up new chemical possibilities, are still in the early stages of development. Existing catalytic transformations of C−C single bonds have typically been limited to substrates with directing groups or strained rings [2c,e,4a–t] . According to previous reports, the combination of NHPI with Co and Mn catalysts can catalyze the oxidation of cycloalkanes, including non‐strained cycloalkanes, to produce ketones under heating conditions, followed by oxidative cleavage to form dicarboxylic acids [4u,v] .…”

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.…”