Non‐C₂‐Symmetric, Chirally Economical, and Readily Tunable Linked‐binols: Design and Application in a Direct Catalytic Asymmetric Mannich‐Type Reaction

An achiral unit is shown to be better than a chiral unit in promoting an asymmetric reaction. Non-C2-symmetric linked-binols 1 with one chiral 1,1′-bi-2-naphthol unit and one flexible achiral unit are employed as ligands in direct catalytic asymmetric Mannich-type reactions (see scheme; TON=turnover number). With as little as 0.01 mol % of ligand 1 a and 0.04 mol % of Et2Zn, the reaction proceeded smoothly to give the product in 98 % ee.