A new catalytic asymmetric tandem α‐alkenyl addition/proton shift reaction of silyl enol ethers with ketimines was serendipitously discovered in the presence of chiral N,N′‐dioxide/ZnII complexes. The proton shift preferentially proceeded instead of a silyl shift after α‐alkenyl addition of silyl enol ether to the ketimine. A wide range of β‐amino silyl enol ethers were synthesized in high yields with
Mannich reactions of aldehydes with ketimines is exemplified by isatin‐derived ketimines and cyclic trifluoromethyl ketimines. Primary amine catalysts exhibit either unusual stereoselectivity or reactivity, which is not observable with secondary amine catalysts. Moreover, reversal of diastereofacial selectivity between primary and secondary amine catalysts is disclosed. These new reactions provide
Catalytic Asymmetric Construction of Vicinal Tetrasubstituted Stereocenters by the Mannich Reaction of Linear α-Substituted Monothiomalonates with Isatin <i>N</i>-Boc Ketimines
A highly diastereo- and enantioselective method for the construction of vicinaltetrasubstitutedstereocenters through the first catalytic asymmetric Mannich reaction of linear α-substituted MTMs with isatin N-Boc ketimines has been developed. This protocol provides atom-economic synthesis of less accessible 3-aminooxindoles bearing vicinaltetrasubstitutedstereocenters. Notably, it also constitutes
A highly enantioselective aza-Friedel–Crafts reaction of 1H-indoles with isatin-derived N-Cbz-ketimines catalyzed by quinine-derived phase-transfercatalysts was developed. A series of chiral 3-aminobisindole compounds containing a tetrasubstituted stereocenter were constructed by this protocol in high yields (82–91%) and moderate to excellent enantioselectivities (46–94% ee).
A highly stereoselective Mannichreaction of α-aminoacid derived azlactones with isatin-derived ketimines enabled by a chiral bifunctional squaramide organocatalyst is reported, affording α,β-diamino acid derivatives bearing vicinal quaternary stereocenters in moderate to good yields (40-95%), moderate to excellent diastereoselectivities (3:1 → 20:1), and good to excellent enantioselectivities (66-97%)