Axially Chiral Cyclic Phosphoric Acid Enabled Enantioselective Sequential Additions.

Area of Science:

• Organic Chemistry
• Asymmetric Catalysis
• Medicinal Chemistry

Background:

• Axially chiral cyclic phosphoric acids are valuable catalysts in asymmetric synthesis.
• Nitrogen-containing heterocycles are important scaffolds in pharmaceuticals.
• Developing efficient methods for constructing complex heterocyclic compounds is crucial.

Purpose of the Study:

• To develop an enantioselective sequential addition reaction for synthesizing novel nitrogen-containing heterocycles.
• To utilize a newly developed axially chiral cyclic phosphoric acid catalyst, (R)-CYC-9-CPA.
• To explore the scope and functional group tolerance of the developed methodology.

Main Methods:

• Enantioselective sequential addition of 2-aryl-3H-indol-3-ones, aldehydes, and diethyl 2-aminomalonate.
• Catalysis using the axially chiral cyclic phosphoric acid, (R)-CYC-9-CPA.
• Oxidation of the resulting dihydro-imidazo[1,5-a]indolone derivatives to the corresponding imidazo[1,5-a]indolones.

Main Results:

• Successful synthesis of 2,3-dihydro-1H-imidazo[1,5-a]indol-9(9aH)-one derivatives with good yields and excellent enantioselectivity (ee values).
• Demonstrated wide functional group tolerance for the substrates.
• Achieved facile oxidation to the corresponding 1H-imidazo[1,5-a]indol-9(9aH)-ones.

Conclusions:

• The developed method provides an efficient and enantioselective route to valuable nitrogen-containing heterocyclic compounds.
• The newly developed (R)-CYC-9-CPA catalyst is highly effective in promoting the reaction.
• This methodology offers a versatile platform for accessing diverse heterocyclic structures with potential applications in drug discovery.