Introduction to 9-Azabicyclo[3.3.1]nonan-3-one N-Oxyl

Basic Information

common name: 9-Azabicyclo[3.3.1]nonan-3-one N-oxyl (Keto-ABNO)

English name: Norpseudopelleterine-N-oxyl

CAS No.: 7123-92-4

Molecular formula: C8H12NO2

Molecular weight: 154.19

EINECS No.: 205-516-1

9-Azabicyclo[3.3.1]nonan-3-one N-oxyl (commonly abbreviated as Keto-ABNO or 3-oxo ABNO; CAS No. 7123-92-4) is an important nitroxyl radical compound. Thanks to its unique molecular structure and excellent catalytic performance, this compound has demonstrated broad application value in organic synthesis, pharmaceutical R&D, and materials science.

1. Key Advantages

Low steric hindrance and high reactivity: 9-Azabicyclo[3.3.1]nonan-3-one N-oxyl is a nitroxyl radical with relatively low steric hindrance. Compared with the classic TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl), this compound exhibits higher reactivity. Its low steric hindrance allows it to react with inert aliphatic alcohols even at room temperature.

Efficient catalytic oxidation performance: As a stable nitroxyl radical, Keto-ABNO is a highly efficient oxidant that can be widely used in catalytic oxidation of alcohols, with higher catalytic activity and capability than TEMPO. Its catalytic efficiency is so high that the catalyst loading can be reduced to 1 mol% without affecting the reaction rate.

Stable radical characteristics: The compound is a stable organic radical reagent and can serve as a persistent organic radical for catalytic aerobic oxidation, protein modification, and other reactions. Its unique molecular structure makes it play an irreplaceable role in many organic reactions.

2. Main Applications

Organic synthesis: selective catalytic oxidation of alcohols

The core application of 9-Azabicyclo[3.3.1]nonan-3-one N-oxyl is as a selective oxidation catalyst for alcohols. It can efficiently catalyze the oxidation of alcohols to the corresponding carbonyl compounds (aldehydes or ketones). With copper salts as co-catalysts, this catalytic system exhibits chemoselectivity and reactivity that conventional oxidants do not possess.

Catalytic synthesis of imines

Using 9-azabicyclo[3.3.1]nonane-N-oxyl radical as the catalyst and air as the oxidant, imines can be prepared by oxidative coupling of alcohols and amines under atmospheric pressure at 70–110 °C. This method is simple and safe to operate, uses clean oxygen as the oxidant to reduce environmental costs, and avoids heavy metal contamination by not using transition metal catalysts.

Preparation of sodium pyruvate

In the synthesis of sodium pyruvate, ethyl pyruvate can be prepared by catalytic oxidation using air as the oxidant, 9-azabicyclo[3.3.1]nonane-N-oxyl radical as the catalyst, and sodium nitrite as the co-catalyst, followed by hydrolysis and neutralization to give sodium pyruvate. Under optimal conditions, the yield of ethyl pyruvate can reach 92%, and the yield of sodium pyruvate can reach 93%.

Pharmaceutical R&D and biomedical research

This compound also has important application value in the pharmaceutical field. Its unique molecular structure gives it good activity against oxidative stress. In biomedical research, it is used in studies of radical-mediated processes and oxidative stress. Moreover, as a stable nitroxyl radical, it is often used as a spin label for structural studies of biological macromolecules. In addition, its molecular skeleton—the 9-azabicyclo[3.3.1]nonane structure—is the core structure of various bioactive compounds, including the antiemetic drug granisetron.

9-Azabicyclo[3.3.1]nonan-3-one N-oxyl (Keto-ABNO) has become a highly regarded efficient oxidation catalyst in organic synthesis, owing to its low steric hindrance, high reactivity, and excellent catalytic efficiency. Whether in the selective oxidation of alcohols, catalytic synthesis of imines, or pharmaceutical R&D and biomedical research, this compound shows broad application prospects. With the growing demand for green chemistry and sustainable catalysis, the application value of Keto-ABNO as an efficient and environmentally friendly organic catalyst will continue to be explored and expanded.