Synthesis of Chiral N-Sulfonyl and N-Phosphinoyl -Halo Aldimine Precursors

-Halogenated aldimines have emerged as an important class of synthetic intermediates. The stability and reactivity of -halo aldimines can vary greatly depending on the nitrogen protecting group. A general synthesis of stable, chiral -halo-N-sulfonyl and N-phosphinoyl aldimine precursors is presented (4296% yield). The corresponding -halo aldimines can be isolated upon treatment with a mild base. Enantioenriched -chloro aldehydes can be employed to afford aldimine precursors with no erosion of optical purity. Both the enantioenriched aldimine precursor and the isolated aldimine can react with an alkynyllithium nucleophile to give trans--chloroamine products with excellent dr. Ring closure affords the enantioenriched trans-aziridine, demonstrating the potential for this approach in complex molecule synthesis.