Reactions of Ketenes and Ketenimines

The thriving chemistry of ketenimines has been reviewed and an overview of the development of silyl ketene imines and their recent applications in catalytic, enantioselective 

Asymmetric synthesis of trans- -lactams from disubstituted ketenes and N-tosyl arylimines has been catalysed by (R)-BINAPHANE with up to 98% ee and (ir 90 10. However, the Staudinger cycloaddition method can be unsuitable if the reactants (ketones -I- imines) bear electron-withdrawing substituents as 0-lactams undergo base-induced isomerization to the azacyclobutene followed by electrocyclic ring opening to the corresponding a, 0-unsaturated alkenamide.  

A short review of the first 100 years of ketene chemistry covers haloketenes, Wolff (g) rearrangements, stereoselective nucleophilic attack, dimerization, cycloadditions, ketene-Claisen and -Cope reactions, bisketenes, and free radical processes.12  

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The [2-1-2] cycloaddition reactions of ketenes and ketenimines with sulfur dioxide are discussed in chapter 4, Sections 4.1 and 4.3, respectively. 

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