Achiral Diamine Research Articles

Optimization of catalyst enantioselectivity and activity using achiral and meso ligands.

The optimization of asymmetric catalysts for enantioselective synthesis has conventionally revolved around the synthesis and screening of enantiopure ligands. In contrast, we have optimized an asymmetric reaction by modification of a series of achiral ligands. Thus, employing (S)-3,3'-diphenyl BINOL [(S)-Ph(2)-BINOL] and a series of achiral diimine and diamine activators in the asymmetric addition of alkyl groups to benzaldehyde, we have observed enantiomeric excesses between 96% (R) and 75% (S) of 1-phenyl-1-propanol. Some of the ligands examined have low-energy chiral conformations that can contribute to the chiral environment of the catalyst. These include achiral diimine ligands with meso backbones that adopt chiral conformations, achiral diimine ligands with backbones that become axially chiral on coordination to metal centers, achiral diamine ligands that form stereocenters on coordination to metal centers, and achiral diamine ligands with pendant groups that have axially chiral conformations. Additionally, we have structurally characterized (Ph(2)-BINOLate)Zn(diimine) and (Ph(2)-BINOLate)Zn(diamine) complexes and studied their solution behavior.

Conformational Control in Proton Sources for Enantioselective Protonation of Samarium Enolate Derived From α-Methoxy-Substituted Ketones

High enantioselectivity is achieved in the asymmetric protonation of samarium enolate, regioselectively generated by SmI 2- mediated reduction of 2-methoxy-substituted cyclohexanones using achiral diamine- or pro-atropisomeric 2,2'-biphenol-derived chiral diols as proton sources by virtue of the conformational control.

ChemInform Abstract: The Crystal and Molecular Structures of Two 1:2 Complexes of 1,4‐Diazabicyclo(2.2.2)octane (DABCO) with 1‐(o‐Chlorophenyl)‐1‐phenyl‐2‐propyn‐1‐ol (CPPOH), and Those of Two 1:2 Complexes of N,N′ Dimethylpiperazine (DMP) with CPPOH

X-Ray crystal structure analysis of the title four complexes showed that crystals consist of CPPOH···achiral diamine···CPPOH units. In the first two crystals a DABCO molecule is bound by two (−)-CPPOH molecules (1) or by (+)- and (−)-CPPOH (2) to form 1:2 complex by strong intermolecular O–H···N hydrogen bonds [O–H···N=2.707(3) and 2.755(3) (1) and 2.704(4) and 2.747(4) A (2)]. The latter two crystals are respectively formed by (+)-CPPOH···DMP···(−)-CPPOH complex (3) [O–H···N=2.771(3) A] and (−)-CPPOH···DMP···(−)-CPPOH complex (4) [O–H···N=2.768(5) and 2.730(6) A].

The Crystal and Molecular Structures of Two 1:2 Complexes of 1,4-Diazabicyclo[2.2.2]octane (DABCO) with 1-(o-Chlorophenyl)1-phenyl-2-propyn-1-ol (CPPOH), and Those of Two 1:2 Complexes of N,N′-Dimethylpiperazine (DMP) with CPPOH

Abstract X-Ray crystal structure analysis of the title four complexes showed that crystals consist of CPPOH···achiral diamine···CPPOH units. In the first two crystals a DABCO molecule is bound by two (−)-CPPOH molecules (1) or by (+)- and (−)-CPPOH (2) to form 1:2 complex by strong intermolecular O–H···N hydrogen bonds [O–H···N=2.707(3) and 2.755(3) (1) and 2.704(4) and 2.747(4) Å (2)]. The latter two crystals are respectively formed by (+)-CPPOH···DMP···(−)-CPPOH complex (3) [O–H···N=2.771(3) Å] and (−)-CPPOH···DMP···(−)-CPPOH complex (4) [O–H···N=2.768(5) and 2.730(6) Å].