On the Inherent Instability of α-Amino α‘-Fluoro Ketones. Evidence for Their Transformation to Reactive Oxyvinyliminium Ion Intermediates

<UFIGR ID="ol006931xn00001">α-Amino α‘-fluoro ketones are shown to be inherently unstable intermediates. Evidence is presented that they undergo enolization toward the amino group followed by expulsion of fluoride ion, forming a proposed oxyvinyliminium ion (amino-substituted oxyallyl cation). In protic, nucleophilic media the proposed intermediate is trapped by solvent. In the presence of a reactive diene, [4 + 3] cycloadducts have been isolated. Prior observations concerning fluorinated amino ketones are discussed in light of these findings.