In this review article, the latest developments of the four most common additive manufacturing methods for metallic materials are reviewed, including powder bed fusion, direct energy deposition, binder jetting, and sheet lamination. In addition to the process principles, the microstructures and mechanical properties of AM-fabricated parts are comprehensively compared and evaluated. Finally, several future research directions are suggested.

From methyl to nitrile: A mild ammoxidation method, which directly converts methyl arenes into aromatic nitriles, has been developed by using Pd(OAc)2 and N-hydroxyphthalimide (NHPI) as the catalysts, and tert-butyl nitrite as the nitrogen source and oxidant.

The hydroxylation of phenols into polyphenols, which are valuable chemicals and pharmaceutical products, is a challenging reaction. The search for green synthetic processes has led to considering microorganisms and pure hydroxylases as catalysts for phenol hydroxylation. Herein, we report the structural and functional characterization of the flavin adenine dinucleotide (FAD)‐dependent 4‐hydroxyphenylacetate 3‐monooxygenase from Escherichia coli, named HpaB. It is shown that this enzyme enjoys a relatively broad substrate specificity, which allows the conversion of a number of non‐natural phenolic compounds, such as tyrosol, hydroxymandelic acid, coumaric acid, hydroxybenzoic acid and its methyl ester, and phenol, into the corresponding catechols. The reaction can be performed by using a simple chemical assay based on formate as the electron donor and the organometallic complex [Rh(bpy)Cp*(H2O)]2+ (Cp*: 1,2,3,4,5‐pentamethylcyclopentadiene, bpy: 2,2′‐bipyridyl) as the catalyst for FAD reduction. The availability of a crystal structure of HpaB in complex with FAD at 1.8 Å resolution opens up the possibility of the rational tuning of the substrate specificity and activity of this interesting class of phenol hydroxylases.

Oxidative [1,2]-Brook rearrangements via hypervalent silicon intermediates induced by photoredox-catalyzed single-electron transfer have been achieved, permitting the formation of reactive radical species that can engage in alkylations and arylations.

Pd-catalyzed cross-coupling of halides with CF3-substituted diazo compounds or N-tosylhydrazones has been explored for the synthesis of CF3-substituted alkenes and 1,3-butadienes. Pd-carbene migratory insertion plays the key role in these transformations.

The transition‐metal‐free 2,2,2‐trifluoroethylation and gem‐difluorovinylation of arylboronic acids were developed. By employing different reaction conditions, these transformations provide both (2,2,2‐trifluoroethyl)arenes and gem‐difluorovinylarenes from arylboronic acids and 2,2,2‐trifluorodiazoethane. The operation is simple and scalable with good functional group tolerance.

Transition-metal-free synthesis of α-aryl esters and nitriles using arylboronic acids with α-aminoesters and α-aminoacetonitriles, respectively, as the starting materials has been developed. The reaction represents a rare case of converting C(sp(3))-N bonds into C(sp(3))-C(sp(2)) bonds. The reaction conditions are mild, demonstrate good functional-group tolerance, and can be scaled up.

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