Synthesis of PhTAD-substituted dihydropyrrole derivatives via stereospecific C–H amination

Stereospecific α-amination has been accomplished via addition of N-phenyltriazolinedione (PhTAD) to the allylic position of dihydropyrroles. The aim of this study is to evaluate new PhTAD derivatives of biologically active bicyclic dihydropyrroles. Ene reaction was accomplished via addition of PhTAD to the allylic position to react with syn and anti diastereomers for α-amination. The α-amination depends on the stereochemistry, proceeding faster with syn than anti diastereoisomers. Steric hindrance from sulfide substituent slows down the transformation. Although the results are in accordance with an ene reaction followed by 1,3-shift of the urazole moiety, deuteration at the allylic position by simply stirring the diastereoisomeric dihydropyrroles in MeOD revealed a [1,3-H] shift. The stereospecificity of the transformation is attributed to steric hindrance during the allylic transposition step.