Migratory insertion

Résumé

In organometallic chemistry, a migratory insertion is a type of reaction wherein two ligands on a metal complex combine. It is a subset of reactions that very closely resembles the insertion reactions, and both are differentiated by the mechanism that leads to the resulting stereochemistry of the products. However, often the two are used interchangeably because the mechanism is sometimes unknown. Therefore, migratory insertion reactions or insertion reactions, for short, are defined not by the mechanism but by the overall regiochemistry wherein one chemical entity interposes itself into an existing bond of typically a second chemical entity e.g.: :{\color{red}\ce A} + {\color{blue}\ce{B-C}} \longrightarrow {\color{blue}\ce{B{-}}}{\color{red}\ce A}{\color{blue}\ce{-C}} Overview Ligand#Classification of ligands as L and X In the migratory insertion, a ligand that is viewed as an anion (X) ligand in and a ligand that is viewed as neutral couple, generating a

Source officielle

https://en.wikipedia.org/wiki/Migratory_insertion

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Transient Heat Transfer Experiments in a Linear Cascade via an Insertion Mechanism Using the Liquid Crystal Technique

Albin Bölcs

1995

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Transition-metal catalyzed C-H functionalizations have impacted and changed synthetic approaches towards the construction of relevant complex molecules, comprising natural products, active pharmaceutical ingredients, and organic materials. This thesis describes the development of Rh(III)-catalyzed reactions via directed C-H functionalization and non-directed C-H functionalization. In this respect, acylated sulfonamides and N-sulfonyl ketimines were successfully employed as suitable directing groups, enabling directed C-H bond activation in the presence of a rhodium(III) catalyst. Subsequent migratory insertion of internal alkynes delivered a rich array of versatile benzosultams and chiral spirocyclic sultams, both of which are relevant structures in medicinal chemistry. Notably, the use of rhodium(III) complexes equipped with a suitable atropchiral cyclopentadienyl ligand enables enantioselective and high yielding access to the challenging spirocyclic sultam scaffolds. Complementary to the directed C-H bond functionalizations, application of CpRh(III) complexes in non-directed C-H functionalization reactions have been disclosed. Specific applications of this challenging strategy include the synthesis of highly valuable polyarenes from completely unbiased arenes via double C-H activation, and subsequent addition of internal alkynes. This method provides a convenient handle to access highly substituted and highly soluble acenes, possessing valuable electronic and photo physical properties. Furthermore, non-directed C-H functionalization of electron-rich heterocycles was also developed. In this context, a CpRh(III) catalyst enables a C2-selective activation of heteroarenes. Upon addition across an alkyne, a transmetalation to Cu(II) allows reductive C-O bond formation to deliver tetrasubstituted enol esters in a trans-selective fashion. A three-component coupling of heteroarenes, alkynes, and carboxylic acids was successfully demonstrated.

EPFL2016

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High-pressure NMR spectroscopy: An in situ tool to study tin-catalyzed synthesis of organic carbonates from carbon dioxide and alcohols. Part 2 [1]

Andrew Francis Dalebrook, Gabor Laurenczy

Dialkoxide diorganotin(IV) complexes are known to readily react with carbon dioxide under pressure and they are considered as suitable catalyst precursor models for the direct synthesis of organic carbonates. To gain a better understanding of CO2 insertion processes with Sn-OR bonds, the reactivity of n-Bu2Sn(OCH(CH3)(2))(2) (2) was investigated using high-pressure NMR (HP-NMR) spectroscopy. In deuterated solvents (isopropanol-d(8) and toluene-d(8)) under 50 bar of CO2 pressure at 80 degrees C, Sn-119{H-1} NMR experiments revealed the exclusive formation of an unprecedented tetraorganodistannoxane species, characterized as the bis[diisopropycarbonatotetrabutyldistannoxane] complex, {n-Bu2Sn(OC(O)OCH(CH3)(2))(2)O}(2) {7}(2). The formation of hemicarbonato ligands resulting from CO2 insertion was also confirmed by FT-IR and C-13 NMR spectroscopies. To the best of our knowledge, spectroscopic detection of the distannoxane species 7 is unprecedented. (C) 2015 Elsevier B.V. All rights reserved.

Elsevier2015

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