Chiral Alcohols & Ligands

Among the numerous catalysts, chiral alcohols and ligands stand out for their versatility. Alfa Chemistry Catalysts is committed to providing new development possibilities for chiral alcohols and ligands, allowing you to achieve research breakthroughs faster.

Chiral Alcohol

Chiral alcohol compounds are widely used in the fields of organic synthesis, material science, medicine, agricultural chemistry and fine chemicals.

• Research applications

(1) Huang Yong et al. investigated the application of chiral alcohols in asymmetric catalysis of these cycloadditions. They demonstrate a simple family of chiral alcohols that use hydrogen bonding to catalyze an important family of cycloadditions of dienes to various aldehydes. Moreover, the reaction is highly enantioselective, yielding only one dihydropyran product per dihydropyran A form of mirror image. This type of catalysis mimics the action of enzymes and antibodies, unlike traditional metal-based catalysts used in organic chemistry.

Figure 1. Hetero Diels-Alder (HDA) reaction scheme in the presence of chiral alcohols [1]

(2) There is growing interest in developing catalytic asymmetric C-C bond formation processes, of which the Henry reaction is important because of the diverse chemical properties of nitro groups. The Henry reaction relies on the simultaneous activation of aldehydes and nitroalkanes. Claudio et al. reported that a highly enantioselective direct Henry reaction can be triggered by a combination of a simple Zn(II) salt, an amine base, and a chiral amino alcohol ligand, and the reaction scheme is shown in the figure below.

Figure 2. Henry reaction of aldehydes promoted by nitromethane (2) and zinc triflate, iPr2EtN, and chiral aminoalcohol ligands (4-10). [2]

Chiral Ligand

Chiral ligands for asymmetric hydrogen transfer feature various combinations of nitrogen, oxygen, phosphorus, sulfur and even arsenic as donor atoms. They can be bidentate, tridentate and tetradentate.

Figure 3. Selected ligands providing ee>90% during acetophenone reduction. [3]

• Research applications

Chiral ligands play an important role in asymmetric synthesis, such as Reduction of C=O, Reduction of C–C multiple bond, Reduction of C=N and other reactions. For example, the phenyl alkyl ketone PhCOAlkyl is the substrate of choice for evaluating new catalysts in transfer hydrogenation. For a given catalytic system, the rate and selectivity are sensitive to the steric crowding of the substrate as well as to the electronic properties of the benzene ring substituents.

Figure 4. Ee values (%) obtained in the asymmetric transfer hydrogenation of aryl and dialkyl ketones. [3]

References

1. Yong Huang. (2003). "Single enantiomers from a chiral-alcohol catalyst," Nature 424: 146.
2. Claudio Palomo. (2005). "Enantioselective Henry Reactions under Dual Lewis Acid/Amine Catalysis Using Chiral Amino Alcohol Ligands," Angewandte Chemie International Eddition 44(25): 3881-3884.
3. Serafino Gladiali. (2006). "Asymmetric transfer hydrogenation: chiral ligands and applications," Chemical Society Reviews 35: 226-236.