Direct Oxidative Cyanation of Alcohol to Nitrile over CoO_x/MnO₂ with Aqueous Ammonia

Abstract

Highly direct oxidative cyanation of alcohols provides a promising synthesis route for the cyanide-free synthesis of organic nitriles. It is challenging to explore a noble metal-free catalyst for direct conversion of alcohol to nitrile under ammonia conditions because it is a three-step consecutive reaction. In the present work, the CoO x /MnO2 catalyst was developed for direct oxidative cyanation of benzyl alcohol to benzonitrile with a yield of 86% and a selectivity of 91% with aqueous ammonia. The selectivity to benzonitrile and benzamide can be tuned via water accelerating the transformation of benzonitrile to benzamide. In addition, the kinetic studies reveal that the first step of the oxidation of benzyl alcohol is the rate-determining step for the consecutive reactions. It is found that Mn species are the main active sites while Co species are the co-catalyst for the titled reaction. Moreover, the starting substrates employed in the present catalytic system can be expanded to aliphatic, benzylic, allylic, and heterocyclic alcohols, which demonstrates a sustainable strategy for the direct synthesis of nitrile from alcohol while avoiding the use of the conventional toxic cyanide.

Tridoped Mesoporous Carbon as a Metal-Free Catalyst for Ammoxidation of (Hetero)Aromatic Alcohols to Nitriles

“…To further elucidate the reaction, the reaction kinetics is investigated according our previous method. – Each step in the continuous reaction is determined to be the first-order reaction (Figure S1). The reaction rate constant ( k 1 ) for conversion of benzyl alcohol to benzaldehyde is 0.1603 h –1 , while the reaction rate constant ( k 2 ) for conversion of benzaldehyde to benzonitrile is 3.4757 h –1 .…”

“…This means that benzaldehyde is much easier to be converted than that of benzyl alcohol, which contributes to the fact that benzaldehyde cannot be detected under the standard reaction condition. In addition, oxidation of benzyl alcohol to benzaldehyde is kinetically considered the rate-limiting step throughout the continuous reaction, which is consistent with our previous study of bimetal-based catalyst . Based on the above, we can conclude that several means should be considered to be taken to improve the reaction efficiency over a metal- or nonmetal-based catalytic system: (1) the conversion of benzyl alcohol should be improved to enhance the reaction activity since the conversion of benzyl alcohol is the rate-limiting reaction step and (2) the reaction rate of benzonitrile to benzamide should be decreased to improve the reaction selectivity to benzonitrile.…”

Enzyme-mimicking single atoms enable selectivity control in visible-light-driven oxidation/ammoxidation to afford bio-based nitriles

“…For a better understanding of the optimized photocatalyst Fe/CNS performance, representative results in the preparation of benzonitrile from benzyl alcohol over the past years are listed in Table 2. [43][44][45][46][47][48][49][50][51][52][53][54][55] Typically, the reaction was often driven by additional heat (50-135 °C), and some of the reported conversion processes were mediated by homogeneous catalysts (Table 2, entries 1-3) or precious metals (entries 7 and 8), which led to the difficulty in separating the catalyst from the product and increased the overall cost of the catalytic system. It is worth noting that our developed photocatalytic system using sunlight as the driving force could achieve satisfactory catalytic activity (up to 91% yield) at room temperature, which is comparable or even superior to traditional thermal catalysts (entries 1-14).…”

Aerobic epoxidation of β-ionone in water under mild conditions using aldehydes as catalyst precursors

“…4 g , h Developing metal-free and halogen-free reactions is the trend from both sustainable chemistry and industrial viewpoints. 5 In 2016, we reported that selenium-containing compounds could catalyse the reaction. 6 Selenium is an essential element for human beings and can be metabolized by the body.…”