Neue Anwendungen für polyfunktionalisierte Organometallverbindungen in der organischen Synthese

Abstract

In der zweiten Hälfte dieses Jahrhunderts wurde viel Forschungsarbeit in die Herstellung polarer Organometallreagentien investiert. Die hohe Reaktivität dieser Reagentien schloss die Gegenwart funktioneller Gruppen aus, und gute Chemo‐ und Stereoselektivitäten waren oft nur durch Transmetallierung zu erreichen. Die Synthese immer komplexerer Zielverbindungen und der Wunsch, ohne umständliche Schutzgruppenstrategien auszukommen, führten dazu, funktionalisierte Organometallreagentien in Retroynthesen zu verwenden. In den letzten 15 Jahren wurde die Herstellung organischer Derivate zahlreicher Metalle und Halbmetalle wie Li, Mg, B, Zn und Sn untersucht. Dieser Aufsatz fasst die wichtigsten Herstellungsmethoden und Anwendungen metallorganischer Reagentien in der organischen Synthese zusammen, wobei der Schwerpunkt auf Organozinkverbindungen liegt.

Reactivity of C1 Surface Species Formed in Methane Activation on Zn‐Modified H‐ZSM‐5 Zeolite

“…With the use of different probe molecules, the reactivity of the zinc methyl species on Zn/H-ZSM-5 catalyst was, therefore, investigated by solid-state 13 C MAS NMR spectroscopy. Typical results are summarized in Scheme 1, which indicates that the chemical nature of the zinc methyl species on the Zn/H-ZSM-5 catalyst is similar to that of organozinc compounds [48][49][50] in organometallic chemistry.…”

“…We propose that the high reactivity of the zinc methyl species in the presence of proton donors on zeolite Zn/H-ZSM-5 (Scheme 1 a-d) can be understood on the basis of the similar chemistry of organozinc compounds. [48][49][50] For example, Coates [51] et al showed that organometallic reagents are readily converted into hydrocarbons in the presence of water. Bruce [52] et al, Noltes and Boersma, [53] and Coates and Ridley [54] demonstrated that organozinc compounds can be transformed into organozinc alkoxide RZnOR' and hydrocarbons by alcoholysis.…”

“…The reactivity of the zinc methyl species on the working catalyst has been investigated in this contribution and, further correlated with that of organozinc compounds in organometallic chemistry. [48][49][50] This information may, therefore, shed new light on the understanding and further development of methane co-conversion process on zinc-containing zeolites.…”

“…Being highly reactive due to the polarized carbonÀmetal (C dÀ ÀM d + ) bonds, organolithium, organomagnesium (Grignard), and organozinc compounds have been extensively used as very important organometallic reagents in organic synthesis. [48][49][50] For example, cross-coupling reactions of organozinc compounds with a variety of electrophiles offer novel strategies for chemo-, regio-, and stereoselective C À C bond formation. [75] More importantly, the formation and further transformation of organometallic species through CÀH bond activation are often crucial steps for atom-economic approaches in natural product and drug synthesis.…”

“…As revealed by the 13 C MAS NMR investigations, zinc methyl species possess similar reactivity as that of organozinc compounds. [48][49][50] For example, zinc methyl species on zeolite Zn/H-ZSM-5 readily react with hydrogen donors to produce methane (Scheme 1 a-d). The reactions of dimethyl-or diethylzinc with various compounds containing reactive hydrogen were investigated by Coates et al, [54] and followed by other groups.…”