Regio- and Stereoselective Lithiation of Terminal Oxazolinylaziridines: The Aziridine <i>N</i>-Substituent and the Oxazolinyl Group Effect
作者:Renzo Luisi、Vito Capriati、Peppino Di Cunto、Saverio Florio、Rosmara Mansueto
DOI:10.1021/ol071264u
日期:2007.8.1
The regioselective lithiation of terminal oxazolinylaziridines has been investigated. The steric hindrance of the nitrogen substituent in 1-trityl-2-oxazolinylaziridine 3a, combined with the coordinating ability of the oxazolinyl group, causes beta-lithiation, whereas a completely regioselective alpha-lithiation is observed with the much less sterically demanding 1-benzyl-2-oxazolinylaziridine 3c and a competition between alpha- and beta-lithiation occurs with 1-cumyl-2-oxazolinylaziridine 3b in which the N-substituent has a steric hindrance in between the trityl and the benzyl groups. The application of the lithiation-trapping sequence for the preparation of enantioenriched 2,3-cis-disubstituted oxazolinylaziridines and aziridino-gamma-lactones is also reported.