The first example of the copper-catalyzed cyclization of 4-(phenylamino)-2H-chromen-2-ones employing the N-methyl moiety of DMF as the source of the methine (CH) group has been developed, providing an efficient synthetic pathway to access novel functionalized 6H-chromeno[4,3-b]quinolin-6-ones in moderate to good yields.

•Catalyst-free protocol.•Air as the terminal oxidant.•Simple purification.•Gram synthesis.•One-pot synthesis amides.Cross-dehydrogenative coupling (CDC) reactions of aldehydes with N-hydroxyimidates such as N-hydroxysuccinimide (NHSI), N-hydroxyphthalimide (NHPI) under catalyst-free conditions is described. Moreover, the desired products can be obtained simply by recrystallization from ethanol. This method is also applicable to the synthesis of amides in excellent yields. A radical mechanism of the type shown in Scheme 4 is proposed based upon the inhibition of the reaction in the presence of TEMPO.Download high-res image (112KB)Download full-size image

An Fe(NO3)3·9H2O-catalyzed cross-dehydrogenative coupling reaction between N-hydroxyphthalimide (NHPI) or N-hydroxysuccinimide (NHSI) and aldehydes or alcohols in air is described. This transformation represents an efficient approach to the preparation of N-hydroxyimide ester derivatives in moderate to excellent yields, and has a wide substrate scope.

A copper nitrate-catalyzed cross-dehydrogenative coupling reaction between N-hydroxyphthalimide (NHPI) and ethers/alkanes has been described. The reaction is accomplished smoothly by using simple and green molecular oxygen as the oxidant, providing an alternative for the efficient synthesis of N-alkoxyphthalimides. In addition, it was found that when tert-butyl ethers were used as substrates, unexpected N-hydroxyimide ester derivatives were obtained in moderate to excellent yields. To further understand this unusual transformation, control experiments were performed and a plausible mechanism was proposed.

Tranexamic acid 1, a synthetic antifibrinolytic drug with the treatment being considered highly cost-effective in many countries, has been included in the WHO list of essential medicines. In this paper, we designed the synthesis of 1 via a novel seven-step route from the readily available starting material dimethyl terephthalate, performing with 99.6% purity in 59.2% overall yield. During the process, we successfully developed a direct and efficient method for the preparation of key intermediate methyl 4-(acetamidomethyl)benzoate by one-pot hydrogenation and acylation in acetic anhydride using Ni/Al2O3 as a catalyst. More importantly, it should be a straightforward and practical way to circumvent the usage of toxic reagents (CrO3, Cl2), solvent (CCl4), and expensive catalyst (PtO2), etc., that plagued the previous methodologies.

An efficient method to access 5-aminotetrazoles starting from readily accessible 1,3-disubtituted selenoureas has been discovered. This is the first example of the synthesis of 5-aminotetrazoles involving the use of diacetoxyiodobenzene (DIB). The reaction is in line with the requirements of green chemistry by virtue of mild conditions, environmental benign, short reaction time, and good selectivity.

A rapid and efficient synthesis of α-keto esters from β-ketonitriles using phenyliodine(III) diacetate is reported. This protocol gave α-keto esters in good yields. This is the first time to report the application of hypervalent iodine(III) reagents in the synthesis of α-keto esters. A plausible reaction mechanism is proposed.

A simple and efficient methodology permitting the halogenation of 2-methylquinolines into 2-(chloromethyl)quinolines or 2-(bromomethyl)quinolines in the tetrabutylammonium iodide and 1,2-dichloroethane (1,2-dibromoethane) system has been developed for the first time. The halogenation can be rapidly completed with good to excellent yields and high selectivity under microwave irradiation.