Carbene insertion into transition metal–carbon bonds: a new tool for catalytic C–C bond formation

Abstract

In this perspective we highlight the applicability of migratory carbene insertion reactions into TM-C bonds as a new tool for catalytic C-C bond formation. In Section 1 we introduce the reaction, wherein we also discuss the applicability of transition metal carbene formation from reactive carbene precursors. In Section 2 we summarise the available mechanistic information about this elementary step derived from stoichiometric model reactions. In Section 3 we review the available catalytic examples, with a focus on new developments in palladium mediated cross-coupling reactions (thus expanding the substrate scope with carbene precursors) and carbene polymerisation (allowing the synthesis of highly functionalised stereoregular polymers that are difficult to prepare otherwise). Recent developments in these fields in combination with the close analogy of carbene insertion reactions with CO (and alkene) insertions open up new possibilities for the development of interesting new reactions based on carbene insertions.

Stereospecific Carbene Polymerization with Oxygenated Rh(diene) Species

“…[1] The commercial synthesis of these materials is mainly based on radical processes, for which stereocontrol is difficult to achieve. [3] These (co)polymers reveal interesting and unexpected material properties, such as thermotropic and lyotropic liquid crystallinity, gel formation, a broad thermal stability range, and a high storage modulus up to high temperatures. However, to the best of our knowledge there are no catalysts known that can polymerize 1,2-difunctionalized olefins such as fumarates or maleates in a stereocontrolled manner.…”

“…However, to the best of our knowledge there are no catalysts known that can polymerize 1,2-difunctionalized olefins such as fumarates or maleates in a stereocontrolled manner. Therefore, the synthesis of high molecular weight and stereoregular densely functionalized sp 3 -carbon chain (co)polymers containing a polar substituent at every carbon atom of the polymer backbone is currently restricted to the Rh-mediated carbene polymerization techniques recently developed in our group (C1 polymerization; Scheme 1). [3] These (co)polymers reveal interesting and unexpected material properties, such as thermotropic and lyotropic liquid crystallinity, gel formation, a broad thermal stability range, and a high storage modulus up to high temperatures.…”

A different route to functional polyolefins: olefin–carbene copolymerisation

“…C1 monomers) as 'functional-group carriers' in coordinationinsertion polymerisation has proven to be successful, especially if densely functionalised, highly stereoregular polymers are desired. [29][30][31][32][33][34][35][36][37][38][39][40][41][42] Highly stereospecific (co)polymerisation of diazoesters (N 2 CHCOOR) can be achieved in good yields and with high M w in a Rh catalysed process. 30,[43][44][45][46][47][48][49][50][51] This leads to the formation of syndiotactic polymers bearing an ester functionality at every single carbon atom of the polymer main chain.…”

Metal-Diazo Radicals of α-Carbonyl Diazomethanes

“…However, their extremely short lifetimes make their direct detection difficult and impede the development of radical chemistry. Carbenes, from nitrogen-releasing diazo compounds 2 , are the versatile active species in a broad range of reactions, including C-H functionalization 3 4 , carbon-carbon bond formation 5 6 , cyclopropanation 7 8 and polycarbene construction 9 10 11 . Usually, these reactions are carried out with metal catalysts, and the intermediates, generally considered to be metal-carbenes, have attracted much attention over the past decade 12 13 14 15 16 .…”