Catalytic Asymmetric Synthesis of Both Syn- and Anti-β-Amino Alcohols

Air-stable, storable, and highly efficient chiral zirconium catalysts for enantioselective Mannich-type, aza Diels–Alder, aldol, and hetero Diels–Alder reactions

“…Not only ketene silyl acetal 2a derived from methyl isobutyrate but also the ketene silyl acetals from S-ethyl ethanethioate (2b) or ␣-oxygenated esters (2c, 2d) worked well, and the reactions proceeded with high enantioselectivities. In the reactions of 2c and 2d, whereas the syn-adduct was obtained by using ␣-tert-butyldimethylsilyloxy enolate 2c, the anti-adduct was produced by using ␣-BnO enolate 2d, both in high diastereo-and enantioselectivities (19). These yields and selectivities were almost comparable with those obtained by using a chiral zirconium catalyst prepared in situ in dichloromethane under an argon atmosphere (Table 3, in parentheses).…”

Dimethyl [(2R,3R,5S)‐5‐phenylmorpholine‐2,3‐diyl]diacetate as a Designer Substrate in the Syntheses of Important Heterocyclic Scaffolds

“…[26] The existing routes for the preparation of this structural unit include the derivitization of amino acids, [27] asymmetric hydrogenation of an enaminoketone, [28] the Sharpless aminohydroxylation reaction [29] , Lewis acid promoted coupling reactions of oxazines with nucleophiles, [30] catalytic Mannich type reactions of aalkoxy enolates to imines, [31] and opening of epoxides with amine nucleophiles. [32] However, most of these approaches give different syn and anti ratios and enantioselectivity.…”

Catalytic Enantioselective Mannich Reactions

“…Moreover, the catalyst was recovered and reused. The Zr-catalyzed Mannich reactions were applied to the synthesis of optically active b-amino alcohols; thus, catalytic diastereo-and enantioselective Mannich reactions of a-alkoxy enolates with imines (Scheme 6.2) 7 and of propionate enolates with imines (Scheme 6.3) 8 have been developed. The O-substituents of ketene silyl acetals and solvents also influenced the yield and selectivity.…”