The thriving chemistry of ketenimines

Abstract

Ketenimines are an important class of reactive species and useful synthetic intermediates. During the last two decades several practical and versatile approaches to ketenimines have been developed, leading to exhaustive investigations on ketenimine chemistry and the discovery of a variety of highly efficient reactions. Five types of reactions for ketenimines have been reported, including nucleophilic additions (ketenimines can be used as both electrophiles and nucleophiles), radical additions, cycloaddition reactions, electrocyclic ring closure reactions, and σ rearrangements. Furthermore, numerous complex organic compounds, particularly the biologically interesting heterocycles, have been constructed using these methodologies. The review of these accomplishments is presented here.

Copper(I)-Y Zeolite-Catalyzed Regio- and Stereoselective [2 + 2 + 2] Cyclotrimerization Cascade: An Atom- and Step-Economical Synthesis of Pyrimido[1,6-a]quinoline

“…7 Developing novel cascade reactions combining two 4 ring sizes, because of their high efficiency, diverse reactivity, bond-forming ability and selectivity. 10 Generally, it involves nucleophilic and radical addition to electrophilic carbon atoms and pericyclic reactions such as [2+2, 3+2, 4+2] cycloadditions, sigmatropic rearrangements and 6π-electrocyclic ring closure reactions. [11][12][13][14] …”

C-terminal peptide extension via gas-phase ion/ion reactions

“…The amino group of an amino ester (i.e., a tert-butyl (tBu) ester) is ‘activated’ by converting it to a ketenimine (ki, –C=C=N–) in the mass spectrometer. Ketenimines are reactive intermediates 18 with an electron-deficient central carbon that can react with various nucleophiles including carboxylic acids, 19 amines, 20,21 hydroxyls, 22 and thiols. 23 Woodward’s reagent K ( N -ethyl-3-phenylisoxazolium-3′-sulfonate, wrk ) 24,25 , a ketenimine-based reagent, has been used for the activation of carboxylic acids of peptides and proteins in solution, 19 although reactions with cysteine, histidine, and lysine side-chains have also been reported.…”

Silylketenimine – vielseitige Nucleophile für die katalytische asymmetrische Synthese

“…[6] In diesem Kurzaufsatz werden neue Fortschritte auf dem Gebiet der SKI-Chemie präsentiert, wobei der Schwerpunkt darauf gelegt wird, wie die einzigartige Struktur der SKIs signifikante Vorteile gegenüber den gebräuchlicheren Enoxysilanen bieten kann. [7] …”