Ning Jiao

Recent advances in transition-metal catalyzed reactions using molecular oxygen as the oxidant

For green and sustainable chemistry, molecular oxygen is considered as an ideal oxidant due to its natural, inexpensive, and environmentally friendly characteristics, and therefore offers attractive academic and industrial prospects. This critical review introduces the recent advances over the past 5 years in transition-metal catalyzed reactions using molecular oxygen as the oxidant. This review highlights the scope and limitations, as well as the mechanisms of these oxidation reactions (184 references).

Dioxygen Activation under Ambient Conditions: Cu-Catalyzed Oxidative Amidation−Diketonization of Terminal Alkynes Leading to α-Ketoamides

A novel Cu-catalyzed oxidative amidation-diketonization reaction of terminal alkynes leading to alpha-ketoamides has been developed. This chemistry offers a valuable mechanistic insight into this novel Cu catalysis via a radical process. O(2) not only participates as the ideal oxidant but also undergoes dioxygen activation under ambient conditions in this transformation.

Indoles from Simple Anilines and Alkynes: Palladium-Catalyzed CH Activation Using Dioxygen as the Oxidant†

Pd doles it out: A palladium-catalyzed approach to indoles using the title reaction was achieved (see scheme). The oxidant used in this catalytic cycle was O(2). Both N-nonsubstituted and N-alkyl monosubstituted anilines can be successfully transformed into the corresponding indoles by this method.

Direct Transformation of N,N-Dimethylformamide to −CN: Pd-Catalyzed Cyanation of Heteroarenes via C–H Functionalization

This paper describes the direct cyanation of indoles and benzofurans employing N,N-dimethylformamide (DMF) as both reagent and solvent. Isotopic labeling experiments indicated that both the N and the C of the cyano group derived from DMF. This transformation offers an alternative method for preparing aryl nitriles, though it is currently limited in scope to indoles and benzofurans.

Copper-Catalyzed Aerobic Oxidative Dehydrogenative Coupling of Anilines Leading to Aromatic Azo Compounds using Dioxygen as an Oxidant†

Aromatic azo compounds are ubiquitous motifs and are widely used in industry as organic dyes, indicators, pigments, food additives, radical reaction initiators, and therapeutic agents. Despite numerous efforts towards the synthesis of azo derivatives, big challenges still remain because: 1) the catalytic procedures that have been reported to afford high yields have been less widely explored; 2) stoichiometric and environmentally unfriendly oxidants, such as manganese salts, lead salts, mercury salts, or ferrates were previously employed for their preparation form aromatic amines; 3) unsymmetric aromatic azo compounds are not easy to prepare. Usually, two step syntheses are used, proceeding from anilines via diazonium salt or nitrosobenzene intermediates, using stoichiometric amounts of nitrite salts or other oxidants, to produce unsymmetric aromatic azo compounds, with inorganic salts as the by-products [Eq. (1)].

N,N‐Dimethylformamide: A Multipurpose Building Block

Often used as a common solvent for chemical reations and utilized widely in industry as a reagent, N,N-dimethylformamide (DMF) has played an important role in organic synthesis for a long time. Numerous highly useful articles and reviews discussing its utilizations have been published. With a focus on the performance of DMF as a multipurpose precursor for various units in numerous reactions, this Minireview summarizes recent developments in the employment of DMF in the fields of formylation, aminocarbonylation, amination, amidation, and cyanation, as well as its reaction with arynes.

Copper-Catalyzed C–H Azidation of Anilines under Mild Conditions

A novel and efficient copper-catalyzed azidation reaction of anilines via C-H activation has been developed. This method, in which the primary amine acts as a directing group by coordinating to the metal center, provides ortho azidation products regioselectively under mild conditions. This effective route for the synthesis of aryl azides is of great significance in view of the versatile reactivity of the azide products.

Cu-catalyzed oxidative amidation of propiolic acids under air via decarboxylative coupling.

A Cu-catalyzed aerobic oxidative amidation of propiolic acids via decarboxylation under air has been developed. Only carbon dioxide is produced as byproduct in this approach. The use of air as oxidant makes this method more useful and easy to handle.

Utilization of Natural Sunlight and Air in the Aerobic Oxidation of Benzyl Halides

A novel, efficient oxidation of α-aryl halogen derivatives to the corresponding α-aryl carbonyl compounds at room temperature has been disclosed. Natural sunlight and air are successfully utilized in this approach through the combination of photocatalysis and organocatalysis. A plausible mechanism was proposed on the basis of the mechanistic studies.

Cu-Catalyzed Esterification Reaction via Aerobic Oxygenation and C–C Bond Cleavage: An Approach to α-Ketoesters

The Cu-catalyzed novel aerobic oxidative esterification reaction of 1,3-diones for the synthesis of α-ketoesters has been developed. This method combines C-C σ-bond cleavage, dioxygen activation and oxidative C-H bond functionalization, as well as provides a practical, neutral, and mild synthetic approach to α-ketoesters which are important units in many biologically active compounds and useful precursors in a variety of functional group transformations. A plausible radical process is proposed on the basis of mechanistic studies.