Transition metal-catalysed couplings between arenes and strained or reactive rings: combination of C–H activation and ring scission

Abstract

Organic transformations that involve direct functionalization of C-H bonds represent an attractive synthetic strategy that maximizes atom- and step-economy. With the generally high stability of C-H bonds, these processes have mostly required harsh reaction conditions, in combination with the necessity of activation of the C-H substrates and/or the coupling partners. As a class of activated coupling partners, strained or reactive rings exhibited high activity in the coupling with aryl and alkyl C-H bonds. Such a high reactivity of the rings allowed the facile construction of various new structural platforms via coupling with scission of the ring structures. The combination of C-H activation and scission of the rings allowed for applications of a broader scope of C-H bonds, including those less reactive alkyl ones. This synthetic diversity of these rings has been realized owing to the intrinsically different mechanisms of the interactions of transition metal catalysts and the strained/reactive rings.

Radical Reactions for the Synthesis of 3‐Substituted Chroman‐4‐ones

“…Cyclopropanols, a class of three‐membered cyclic compounds, are useful synthetic intermediates in organic synthesis. For example, a variety of transition‐metal‐catalyzed ring‐opening cross‐coupling reactions have been developed . In the past years, cyclopropanols have been reported as radical precursors through C–C bond cleavage giving β‐carbonyl alkyl radicals for the ring‐opening/cascade radical coupling strategy .…”

“…For example, a variety of transition-metal-catalyzed ring-opening cross-coupling reactions have been developed. [88][89][90] In the ation to give the corresponding oxygen-centered radical 70 either by Ag 2+ species or sulfate radical, which were in situ generated in the AgNO 3 /K 2 S 2 O 8 system. Then radical 70 was converted into a -keto alkyl radical 71 through rearrangement, which would trigger the following cascade addition/cyclization.…”

Effiziente Synthese von arylierten Furanen durch sequentielle Rhodium‐katalysierte Arylierung und Cycloisomerisierung von Cyclopropenen

“…Verglichen mit herkçmmlichen Olefinen bietet Cyclopropen die kleinste ungesättigte Ringeinheit und zeigt aus diesem Grund einzigartige sowie vielseitige Reaktivitäti nv erschiedenen Tr ansformationen. [7,8] Hier beschreiben wir eine neue Synthese von arylierten Furanen unter Verwendung eines Rhodiumkatalysators fürdie Kupplung von N-Phenoxyacetamiden mit Cyclopropenylestern unter milden und Additiv-freien Bedingungen (Schema 2c). [7,8] Hier beschreiben wir eine neue Synthese von arylierten Furanen unter Verwendung eines Rhodiumkatalysators fürdie Kupplung von N-Phenoxyacetamiden mit Cyclopropenylestern unter milden und Additiv-freien Bedingungen (Schema 2c).…”

Combination of Cp*RhIII‐Catalyzed C−H Activation and a Wagner–Meerwein‐Type Rearrangement

“…[1] Specifically,C p*Rh III -catalyzed CÀHa ctivation/coupling reactions have been widely explored and enabled the development of methods for the synthesis of various structurally diverse organic molecules. [3][4][5] Both b-elimination and protonation of the resulting CÀRh bond have been well studied in Cp*Rh III -catalyzed CÀHa ctivation, giving ring-opened and protonated products,r espectively (Scheme 1a;C p* = h-C 5 Me 5 ). [3][4][5] Both b-elimination and protonation of the resulting CÀRh bond have been well studied in Cp*Rh III -catalyzed CÀHa ctivation, giving ring-opened and protonated products,r espectively (Scheme 1a;C p* = h-C 5 Me 5 ).…”