Ketenimines reaction with amines

In the reaction of /h/f-difluoro ketones with amines, a,/I-unsaturated / -amino ketones are formed, either by inline formation and imine enaminc tautomerization or via elimination of hydrogen fluoride and subsequent substitution of the other fluorine.22 Geminal sp2-bonded difluoridcs arc converted into ketenimines.12-49,89,90... 

The presence of two hydrogen atoms at the nitrogen in the amines permits subsequent prototropic isomerization with the formation of ketenimines. By way of contrast, reactions with primary phosphines lead to halogen-substitution products with retention of the bond and P-H bonds. The reaction of ketenimines with water in the presence of a catalytic amount of HCl proceeds smoothly and leads to a high yield of the corresponding amide. 

Along with the substituent effect on the reactivity of singlet phenylnitrenes, the influence of substituents on the reactions of ketenimines with nucleophiles was also studied in detail. As in the case of unsubstituted ketenimine 51, its simple derivatives could be trapped by nucleophiles in solution. The primary products, corresponding IH-azepines, undergo subsequent isomerization to final products. Reaction of ketenimines with primary and secondary amines is the most studied of the reactions with nucleophiles. Rate constants of this reaction with DEA (Table 11.4) were measured for a series of substituted ketenimines using TRIR spectroscopy, as well as conventional LFP techniques. ... 

Ketenimines, formed as intermediates in the reactions of aromatic amines with a dimer of hexafluoropropene (34), cyclize in an interesting process that yields perfluoroalkyl derivatives of various heterocyclic systems (Eq. 33).119... 

Reactions of fluoroalkylketenimines which have been reported following these newly available synthetic approaches include hydrolysis and related additions of amines and alcohols, all of which occur at the olefinic bond. In contrast, the apparently similar addition of secondary phosphines occurs at the carbon-nitrogen double bond. These ketenimines appear to enter into cycloaddition reactions very readily with acetylenes they give quinolines, with nitrones they give oxindoles or oxadiazolidines (see p. 107), i > i and with isocyanides they yield iminoindolenines. These reactions are summarized in Scheme 54. 

Scheme 11,26 Reaction of ketenimine with primary and secondary amines...

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