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  • Title: Asymmetric synthesis of aziridine 2-phosphonates from enantiopure sulfinimines (N-sulfinyl imines). Synthesis of alpha-amino phosphonates.
    Author: Davis FA, Wu Y, Yan H, McCoull W, Prasad KR.
    Journal: J Org Chem; 2003 Mar 21; 68(6):2410-9. PubMed ID: 12636410.
    Abstract:
    An aza-Darzens reaction, involving the addition of chloromethylphosphonate anions to enantiopure sulfinimines, has been developed for the asymmetric synthesis of aziridine 2-phosphonates. Best results involve cyclization of the syn and anti diastereomerically pure alpha-chloro-beta-amino phosphonates to cis- and trans-N-sulfinyl aziridine 2-phosphonates, respectively, with n-BuLi. A transition-state hypothesis is proposed wherein the chloromethylphosphonate anion adds to the C-N bond on the side that is opposite the bulky p-tolyl sulfinyl group. The N-sulfinyl group is easily removed by treatment with MeMgBr or TFA/MeOH, which affords the NH-aziridines in good yield. Using transfer hydrogenation conditions, the NH-aziridines were regioselectively opened to the corresponding enantiopure alpha-amino phosphonates without N-activation and in excellent yield.
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