Abstract

In this paper, the chemical properties, synthesis methods, and applications of 1.1'-Binaphthyl-2.2'-diphemyl phosphine (BINAP) in asymmetric catalytic reactions were reviewed.  as an important chiral ligand, shows excellent enantioselectivity in many reactions such as asymmetric hydrogenation, carbonyl reduction, and arylamine coupling. This paper also introduces two main synthesis methods of it and discusses its future development direction and application prospects.

Introduction

Chiral compounds are widely used in medicine, pesticides, spices, and other fields, so asymmetric synthesis has been one of the hot spots in chemistry research. 1.1'-Binaphthyl-2.2'-diphemyl phosphine as an important chiral ligand, has been widely studied and applied in asymmetric catalysis because of its unique structure and high enantioselectivity. In this paper, the chemical properties, synthetic methods, and applications of it in asymmetric catalytic reactions are reviewed.

Chemical properties

1.1'-Binaphthyl-2.2'-diphemyl phosphine is a white to pale yellow crystalline powder with the molecular formula C₄₄H₃₂P₂ and molecular weight 622.67. It has a high melting point and boiling point, respectively 280-285℃ and 724.3±55.0℃ (Predicted). It is soluble in organic solvents such as tetrahydrofuran, benzene, and dichloromethane, but its solubility in water is very low. In addition, it is air-sensitive and needs to be stored under inert gas protection.¹

Synthesis method

There are two main synthesis methods of 1.1'-binaphthyl-2.2'-diphemyl phosphine, one is through the condensation reaction of binaphthol and diphenylphosphine chloride, and the other is through the oxidative coupling reaction of binaphthol.

(1) Condensation reaction and diphenylphosphine chloride

The condensation reaction was carried out with binaphthol and diphenylphosphine chloride as raw materials under alkaline conditions. In the process of reaction, temperature, reaction time and solvent should be controlled to obtain high-purity 1.1'-binaphthyl-2.2'-diphemyl phosphine. The advantages of this method are that the raw material is easy to obtain and the reaction conditions are mild, but the purity of the product is greatly affected by the purity of the raw material and the reaction conditions.²

(2) Oxidative coupling reaction

The method takes 1.1'-binaphthyl-2.2'-diphemyl phosphine as raw material and performs an oxidative coupling reaction under the action of an oxidizing agent. The reaction process needs to add a catalyst and solvent and control the reaction temperature and time. The advantages of this method are simple reaction steps and high product purity, but it requires the use of expensive catalysts and solvents.

Application in asymmetric catalytic reactions

1.1'-Binaphthyl-2.2'-diphemyl phosphine, as an important chiral ligand, shows excellent enantioselectivity in asymmetric catalytic reactions. Some typical application examples are listed below:

(1) Asymmetric hydrogenation reaction

The complex formed by 1.1'-binaphthyl-2.2'-diphemyl phosphine with palladium is a common catalyst in asymmetric hydrogenation reactions. The catalyst can catalyze the asymmetric hydrogenation of many alkenes to obtain chiral alcohols with high enantioselectivity. For example, with palladium complexes can catalyze the asymmetric hydrogenation of styrene, and the yield of chiral phenyl ethanol can be as high as 99%.³

(2) carbonyl reduction reaction

1.1'-Binaphthyl-2.2'-diphemyl phosphine can also form complexes with metals such as rhodium to catalyze the asymmetric reduction of carbonyl groups. This reaction has important application value in the preparation of chiral alcohols, aldehydes, and other compounds. For example, With rhodium complexes can catalyze the asymmetric reduction of ketones, resulting in higher yield and enantioselectivity of chiral alcohols.⁴

(3) arylamine coupling reaction

1.1'-Binaphthyl-2.2'-diphemyl phosphine can also be used as a ligand for palladium-catalyzed arylamine coupling reactions. This reaction is one of the important methods to prepare biaryl compounds. The introduction of it can significantly improve the enantioselectivity of the reaction and obtain high-purity chiral biaryl compounds.⁵

Outlook

1.1'-Binaphthyl-2.2'-diphemyl phosphine, as an important chiral ligand, has a wide application prospect in asymmetric catalysis. In the future, with the continuous development of asymmetric synthesis technology, the application field of it will be further expanded. At the same time, the synthesis method of it also needs to be further studied and optimized to improve its yield and purity. In addition, combining it with other functional groups to form multifunctional ligands is also one of the future research directions.

Conclusion

In summary, 1.1'-Binaphthyl-2.2'-diphemyl phosphine as an important chiral ligand, shows excellent enantioselectivity in asymmetric catalytic reactions. Its unique structure and high enantioselectivity make it widely used in medicine, pesticides, spices, and other fields. With the continuous development of asymmetric synthesis technology, the application prospect of 1.1'-binaphthyl-2.2'-diphemyl phosphine will be more broad.

Refences

[1].Noyori, R.; Takaya, H., BINAP: an efficient chiral element for asymmetric catalysis. Accounts of Chemical Research 1990,23(10), 345-350.

[2].Akutagawa, S., Asymmetric synthesis by metal BINAP catalysts. Applied Catalysis A: General 1995,128(2), 171-207.

[3].Sandoval, C. A.; Ohkuma, T.; Mu?iz, K.; Noyori, R., Mechanism of asymmetric hydrogenation of ketones catalyzed by BINAP/1, 2-diamine? ruthenium (II) complexes. Journal of the American Chemical Society 2003,125(44), 13490-13503.

[4].Tanaka, K.; Otake, Y.; Wada, A.; Noguchi, K.; Hirano, M., Cationic Rh (I)/modified-BINAP-catalyzed reactions of carbonyl compounds with 1, 6-diynes leading to dienones and ortho-functionalized aryl ketones. Organic Letters 2007,9(11), 2203-2206.

[5].Wada, A.; Noguchi, K.; Hirano, M.; Tanaka, K., Enantioselective Synthesis of C 2-Symmetric Spirobipyridine Ligands through Cationic Rh (I)/Modified-BINAP-Catalyzed Double [2+ 2+ 2] Cycloaddition. Organic Letters 2007,9(7), 1295-1298.