N-silyl oxyketene imines are underused yet highly versatile reagents for catalytic asymmetric synthe

Abstract

The reactions of acyl anion equivalents (d1 synthons) with carbonyl electrophiles allow for the construction of a wide range of molecules useful for the synthesis of biologically active compounds, natural products and chiral ligands. Despite their utility, significant challenges still exist for developing catalytic, enantioselective variants of these reactions. For example, the asymmetric benzoin process, arguably the most characteristic reaction of d1 synthetic equivalents, finds no general solution for reactions involving aliphatic acyl anions. In this Article, we introduce a new class of stable, isolable silyl ketene imines derived from protected cyanohydrins. These nucleophiles serve as acyl anion equivalents in Lewis base catalysed aldol addition reactions and allow for the preparation of cross-benzoin and glycolate-aldol products in high yield and with exceptional diastereo- and enantioselectivities. A new class of stable, isolable N-silyl oxyketene imines derived from protected cyanohydrins is introduced. Utilization of these nucleophiles in Lewis-base-catalysed aldol additions allows access to either cross-benzoin or glycolate aldol-type products in good yields and exceptional selectivities by simply altering the conditions of the reaction.

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Denmark, S., Wilson, T. N-silyl oxyketene imines are underused yet highly versatile reagents for catalytic asymmetric synthesis. Nature Chem 2, 937–943 (2010). https://doi.org/10.1038/nchem.857

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