Daqian Xu

Highly Efficient Oxidation of Secondary Alcohols to Ketones Catalyzed by Manganese Complexes of N4 Ligands with H2O2

The manganese complex Mn(S-PMB)(CF3SO3)2 was proven to be highly efficient in the catalytic oxidation of several benzylic and aliphatic secondary alcohols with H2O2 as the oxidant and acetic acid as the additive. A maximum turnover number of 4700 was achieved in the alcohol oxidation. In addition, the Hammett analysis unveiled the electrophilic nature of this manganese catalyst with N4 ligand.

Enantioselective Epoxidation of Olefins with H2O2 Catalyzed by Bioinspired Aminopyridine Manganese Complexes

A novel family of bioinspired manganese(II) complexes bearing chiral aminopyridine ligands that possessed additional aromatic groups and strong donating dimethylamino groups were synthesized and characterized. These manganese complexes exhibited efficient and improved activities in the asymmetric epoxidation of various olefins, such as styrene derivatives (up to 93% ee) with H2O2 as the oxidant, even with a catalytic amount of carboxylic acid as the additive.

Merging the ring opening of benzoxazoles with secondary amines and an iron-catalyzed oxidative cyclization towards the environmentally friendly synthesis of 2-aminobenzoxazoles

A facile and environmentally friendly method was developed through merging the ring opening of benzoxazoles with secondary amines and an iron-catalyzed oxidative cyclization towards the synthesis of 2-aminobenzoxazoles. In the oxidative cyclization step, with catalytic amounts of FeCl and aqueous H2O2 as a green oxidant, highly desirable 2-aminobenzoxazoles were isolated in excellent yields of up to 97%. A plausible radical process is proposed for the oxidative cyclization on the basis of mechanistic studies.

Direct halogenative dearomatization of 2-naphthols by NXS (X = Cl, Br) in water

A direct halogenative dearomatization of substituted 2-naphthols was achieved by NXS (X = Cl, Br) in environmentally friendly water at room temperature. The reaction exhibited broad substrate scope, convenient operation and high yields (up to 99%), thus providing a facile route to dearomatic products and complex polycyclic frameworks.

CuI/N4 ligand/TEMPO derivatives: A mild and highly efficient system for aerobic oxidation of primary alcohols

Abstract A new system consisting of a copper(I) complex generated in situ from a tetradentate nitrogen ligand and CuI in combination with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) derivatives was successfully developed. The system was suitable for efficient and selective aerobic oxidation of primary benzyl and allyl alcohols with a wide range of functional groups to the corresponding aldehydes at room temperature. The best result was obtained with N,N’ -dimethyl- N,N’ -bis(2-pyridylmethyl)ethane-1,2-diamine as the ligand and 4-OH-TEMPO as a cocatalyst in CH 3 CN. In addition, high-resolution mass spectrometry, ultraviolet-visible spectroscopy, and electrochemical experiments were used to provide evidence of intermediates.

Asymmetric Epoxidation of Olefins with H2O2 Catalyzed by a Bioinspired Aminopyridine N4 Iron Complex

An iron complex with a chiral aminopyridine N4 ligand bearing strong electron‐donating and bulky morpholine groups on the ligand is synthesized and characterized. The iron complex serves to efficiently catalyze the asymmetric epoxidation of various olefins by employing aqueous hydrogen peroxide as the green oxidant, providing the corresponding epoxides in good to excellent yields and enantioselectivities (up to 93 % yield and 99.9 % ee). Owing to the introduction of morpholine functional groups on the ligand, the Fe‐catalyzed reaction can proceed with a catalytic amount of the carboxylic acid partner (3 mol %).

Tetraethylammonium iodide catalyzed synthesis of diaryl ketones via the merger of cleavage of C–C double bonds and recombination of aromatic groups

An efficient method for synthesizing diaryl ketones via merging of oxidative cleavage of C–C double bonds and recombination of aromatic groups is developed with Et4NI (2.5 mol%) as the catalyst and NaIO4 as the oxidant. The control experiments provide valuable mechanistic insights into the formation of diaryl ketones, and suggest that NaIO4 serves as an epoxidation and nucleophilic deformylation reagent.

Efficient Aliphatic C−H Bond Oxidation Catalyzed by Manganese Complexes with Hydrogen Peroxide

A tetradentate nitrogen ligand containing a benzimidazole ring and an electron-rich pyridine ring was developed, the resulting manganese complex exhibited good activity in the C-H oxidation of simple alkanes. In particular, cyclic aliphatic alkanes were transformed into ketones in very good yields (up to 89 %) by using environmentally benign H2 O2 as the terminal oxidant. This protocol was also applied successfully in benzylic C-H oxidation, giving the corresponding ketones with very good selectivities. In addition, tertiary C-H bond oxidation of complex molecules by the manganese complex showed potential utility for assembling alcohols with good selectivity in late-stage chemical synthesis.