Radikalische Carbonylierungen – gestern und heute

Abstract

t Schema 1. Mogliche Intermediate bei Carbonylierungen rnit CO. aber mit radikalischen Carbonylierungen aus? Wurde das Potential der modernen Radikalchemie fur diesen Reaktionstyp ausgeschopft ? Diese einfachen Fragen veranlanten uns Ende der achtziger Jahre, mit eigenen Studien auf diesem damals weitgehend unerforschten Gebiet zu beginnen. Die ersten Arbeiten iiber radikalische Carbonylierungen gehen auf Coffman und Mitarbeiter zuruck, die 1952 eine Peroxid-initiierte Copolymerisation von Ethylen und CO be~chrieben[~]. Leider wurden solche Reaktionen wenig beachtet, da sie drastische Reaktionsbedingungen erfordern (CO-Druck > 1000 atm) und kinetische

Pd/Light‐Accelerated Atom‐Transfer Carbonylation of Alkyl Iodides: Applications in Multicomponent Coupling Processes Leading to Functionalized Carboxylic Acid Derivatives

“…[16a] In contrast, in the absence of a Pd catalyst, amide 16 was obtained as the sole carbonylated product. [9b] Because the carbonylation of an acyl radical is rarely observed in radical-carbonylation reactions, [29] the intervention of an acylcarbamoylpalladium complex, which has been well-established by Yamamoto and co-workers for a Pd-catalyzed double-carbonylation reaction, [30] is strongly suggested to account for the formation of compound 17. We believe that the Pd I I species may be a persistent radical [31] that may exist in equilibrium with a PdI dimer under the photoirradiation conditions.…”

Transition‐Metal‐Free Alkoxycarbonylation of Aryl Halides

“…These results usually involve a xenon photolytic system or AIBN/tin hydride mediated radicalchain reaction employing alkyl iodides as substrates. [24][25][26][27][28][29][30] To the best of our knowledge, there is no example of employing a transition-metal-free process in alkoxycarbonylation of aryl halides. Herein, we disclose a protocol for accessing tert-butyl benzoates through the transition-metal-free alkoxycarbonylation of aryl halides.Our experiment was initiated by treating 4-iodotoluene (1 a) with KOtBu in the presence of a high pressure CO (Table 1).…”

Transition‐Metal‐Free Alkoxycarbonylation of Aryl Halides

“…Generally, low-valent-metal catalysts such as palladium(0) are required to activate the CÀX bond, whereas the strong binding ability of CO towards low-valent metals deactivate the catalyst, which present a challenge in this transformation. [24][25][26][27][28][29][30] To the best of our knowledge, there is no example of employing a transition-metal-free process in alkoxycarbonylation of aryl halides. The key challenge of this idea is to determine how to activate CÀX without the help of transition-metal catalysts.…”

“…The key challenge of this idea is to determine how to activate CÀX without the help of transition-metal catalysts. [24][25][26][27][28][29][30] To the best of our knowledge, there is no example of employing a transition-metal-free process in alkoxycarbonylation of aryl halides. Recently, transition-metal-free coupling reactions of aryl halides with arenes and alkenes have been developed, and the combination of MOtBu and bidentate nitrogen ligands was employed to initiate the aryl radical by single-electron transfer (SET).…”