Chiral Phosphoric Acid-Mg Catalysts

At the same time, Antilla et al. developed a vaulted biphenanthrol (VAPOL)-based magnesium phosphate 20b mediated asymmetric aza-Darzens reaction for the synthesis of chiral aziridine derivatives. The catalyst was prepared in an identical procedure to the previously described process with VAPOL-derived phosphate and magnesium fert-butoxide, and applied in the enantioselective aza-Darzens reaction of N-benzoyl imines 23 and ot-chloro-1,3-diketone 24. The process formed a series of substituted aziridines 25 bearing various substituents at the aromatic ring, with good 

Luo et al. exploited the enantioselective Friedel-Crafts reaction of phenols 35 with p,y-unsaturated ot-ketoesters 32 to form compounds 36. In their preliminary studies, they found that neither a phosphoric acid nor magnesium fluoride could catalyse the reaction. However, the combination of a phosphoric acid with magnesium fluoride (4 1 ratio) could efficiently catalyse the reaction in good yields (59-82%) and selectivity (79-99%), but using preformed sodium phosphate with magnesium fluoride resulted in no 

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