Remarkably Stable Chiral Zirconium Complexes for Asymmetric Mannich-Type Reactions

Abstract

Isolable, air-stable, storable, and highly selective chiral zirconium catalysts for asymmetric Mannich-type reactions have been developed. The reactions of imines with silicon enolates proceeded smoothly using 1-10 mol % of the powdered zirconium catalyst to afford the corresponding adducts in high yields with high stereoselectivities. The catalyst could be recovered and reused without significant loss of activity. On the other hand, zirconium single crystals for X-ray analysis were obtained, and the crystals also showed high performance in the asymmetric Mannich-type reactions. Although NMR analyses of these zirconium catalysts showed different structures in dichloromethane, the formation of the same key intermediate from the different catalysts was indicated.

Synthesis of Titanatranes Containing Bis(aryloxo)‐(alkoxo)amines and their Use in Catalysis for Ethylene Polymerization

“…As shown in Figure 2 (center, right), complete overlapping of the Ph group on one side was seen when we rotated the solid state structures, however, overlapping of the Ph rings in the other side was not observed (which probably makes the CH 2 and other signals to appear separately for each ligand moieties in the 1 H NMR spectrum). The observation is somewhat related to a recent report by Kobayashi et al [16] in the formation of BINOLate zirconium complexes containing two ligand moieties during attempted crystallization of the (BINOLate) 2 Zr(Nbenzylimidazole) 2 . Although we could not isolate the desired complex, the fact observed here should be important for designing the efficient catalyst with this approach.…”

Characterization of Dimeric and Tetrameric μ‐Hydroxide Ytterbium(III) Binaphtholate Complexes

“…[3,6,20] At this time, the catalytic activity and/or relevance of the hydroxide-bridged compounds to reactions catalyzed by M 3 A C H T U N G T R E N N U N G (THF) n A C H T U N G T R E N N U N G (BINOLate) 3 Yb [M = Li and K] is unclear. On the basis of recent reports using the tetrameric clusters Zr 4 A C H T U N G T R E N N U N G (BINOLate) 6 A C H T U N G T R E N N U N G (m 3 -OH) 4 [25] and Ti 4 A C H T U N G T R E N N U N G (BINOLate) 6 A C H T U N G T R E N N U N G (m 3 -OH) 4 [26,27] as stable and effective catalyst in organic reactions, one should remain mindful of the potential formation and influence of hydroxide-bridged oligomers in asymmetric reactions when water is used as an additive with M 3 A C H T U N G T R E N N U N G (THF) n A C H T U N G T R E N N U N G (BINOLate) 3 Ln catalyst.…”

“…The hydroxide Yb À O À Yb angles in 4 range from 102.68(2) to 105.58(3), resulting in a distortion of the cubic core. The core structure of 4 is reminiscent of the structures of catalytically active Zr 4 A C H T U N G T R E N N U N G (BINOLate) 6 A C H T U N G T R E N N U N G (m 3 -OH) 4 [25] and Ti 4 A C H T U N G T R E N N U N G (BINOLate) 6 A C H T U N G T R E N N U N G (m 3 -OH) 4 . [26,27] While we cannot explain the factors that give rise to the structural differences in 3 and 4, we note that the Brønsted basicities of the binaphtholate moiety are dependent on the alkali metal (ROLi < RONa < ROK).…”

Synthesis and structure of an air-stable organoantimony complex and its use as a catalyst for direct diastereoselective Mannich reactions in water

“…Kobayashi et al reported that FeCl 2 together with a (R)-3.3 0 -I 2 BINOL complex is effective for the Mannich reaction of imines with silyl enolates [6]. Similar reactions were performed by using a novel chiral zirconium catalyst for the production of b-amino ester derivatives [7,8]. List and co-workers reported that the proline-catalyzed asymmetric Mannich reactions (with different ketones) displayed high enantioselectivity but accompanied by some aldol products [9,10].…”