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  • Title: Chiral amine/chiral acid as an excellent organocatalytic system for the enantioselective tandem oxa-Michael-aldol reaction.
    Author: Luo SP, Li ZB, Wang LP, Guo Y, Xia AB, Xu DQ.
    Journal: Org Biomol Chem; 2009 Nov 07; 7(21):4539-46. PubMed ID: 19830307.
    Abstract:
    The asymmetric tandem oxa-Michael-aldol reaction of salicylic aldehyde derivatives with alpha,beta-unsaturated aldehydes catalyzed by a chiral amine/chiral acid organocatalytic system was investigated. The organocatalytic system of (S)-diphenylpyrrolinol trimethylsilyl ether with chiral shift reagent (S)-Mosher acid presented a synergistic effect in the improvement of reaction performance and offered an efficient steric effect in the transformation. The tandem oxa-Michael-aldol reaction proceeded with high yields (up to 90%) and with excellent ee values (up to 99%) to give the corresponding chromene derivatives. The structure of the chiral ammonium salt formed in situ and the corresponding mechanism were also studied by (1)H NMR.
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