Jianyong Mao

Iron chloride supported on pyridine-modified mesoporous silica: an efficient and reusable catalyst for the allylic oxidation of olefins with molecular oxygen

A novel heterogeneous catalyst with iron chloride immobilized on pyridine-modified mesoporous silica has been developed. The supported Fe(III)/SiO2 catalyst displayed excellent catalytic properties for the allylic oxidation of 3,5,5-trimethylcyclohex-3-en-1-one (β-IP, 1) to 3,5,5-trimethlycyclohex-2-ene-1,4-dione (KIP, 2) with molecular oxygen as the oxidant under mild conditions. It can also catalyze the oxidation of other olefins, such as α-pinene and cyclohexene and its derivatives efficiently and selectively. In addition, the supported catalyst can be easily recycled without significant loss of activity and selectivity, which is a green alternative for practical applications.

A cobalt Schiff base with ionic substituents on the ligand as an efficient catalyst for the oxidation of 4-methyl guaiacol to vanillin

A cobalt Schiff base catalyst with ionic substituents on the ligand, N,N′-ethylenebis(acetylacetoniminato)-cobalt(II) hexafluorophosphoric pyridinium (Co-[Salen-Py][PF6]2), was synthesized. It displayed an excellent catalytic performance for the oxidation of 4-methyl guaiacol to vanillin (conversion = 100%, selectivity = 90%). Tentative reaction mechanism research indicated that the electron-withdrawing pyridinium substituent on the ligand of Co(acacen) is responsible for the high selectivity of vanillin. Meanwhile, utilizing ethylene glycol and water as solvent, vanillin can be isolated by simple crystallization in the form of a sodium salt, and the mother liquid of the crystallization, with a large amount of NaOH (the mole ratio of NaOH/4-methyl guaiacol = 2.38/1), can be successfully recycled at least three times, thereby decreasing the mole ratio of base/substrate from 3.3 : 1 to 1.05 : 1 when the mother liquid of crystallization was recycled. This strategy provides a potentially greener alternative for the synthesis of vanillin in industry.

An environmentally benign catalytic oxidation of cholesteryl acetate with molecular oxygen by using N-hydroxyphthalimide

A green and effective method is reported for the oxidation of cholesteryl acetate to 7-keto-cholesteryl acetate with O2 in the presence of catalytic amounts of N-hydroxyphthalimide (NHPI) under mild conditions. It was found that Co(OAc)2 could cooperate with Mn(OAc)2 to enhance the catalytic ability of NHPI resulting in better yields. This economical and environmentally-friendly method provides a potentially new way for the synthesis of the intermediate product of vitamin D3 in industry, which eliminates the use of large amounts of bromine in present route and overcomes the drawbacks of the known oxidation methods.

Selective aerobic oxidation of alcohols by a mesoporous graphitic carbon nitride/N-hydroxyphthalimide system under visible-light illumination at room temperature

Abstract By combination of photocatalysis and organocatalysis, a metal-free system composed of mesoporous graphitic carbon nitride (mpg-C3N4) and N-hydroxyphthalimide (NHPI) offers an efficient and environmentally friendly method for the oxidation of alcohols at room temperature. As a wide-band gap semiconductor, mpg-C3N4 absorbs visible light and uses the energy to activate NHPI, resulting in high catalytic activity in the subsequent oxidation of alcohols. Interestingly, the main oxidation product of benzyl alcohol can be tuned from benzoic acid to benzaldehyde by increasing the ratio of mpg-C3N4 in the catalyst system. To further understand the reaction route, electron spin resonance and Fourier transform infrared measurements were carried out, confirming that active oxygen and phthalimide N-oxyl radicals formed in the mpg-C3N4/NHPI system. Based on these results, a catalytic mechanism for the mpg-C3N4/NHPI system was proposed. Moreover, this metal-free system also works well for the oxidation of various aromatic alcohols with good selectivity for aldehydes or ketones.