ChemPubSoc Europe Early View Journal Articles

Chemistry - A European Journal

Carbon Monoxide Coupling Reactions: A New Concept for the Formation of Hexahydroxybenzene

Published: 18 September 2020

Author(s): Uwe Rosenthal

Abstract For linear and cyclic coupling reactions of CO, among other products, the formation of the hexapotassium salt of hexahydroxybenzene is of particular interesting. The interaction of metallic potassium and CO offers, via the assumed K[OC≡CO]K as the result of several carbon monoxide coupling reactions, the formation of C6(OK)6 among other products. To date, only speculations exist about the reaction pathway for these products, which were first described by Liebig in 1834. A novel...

Chemistry - A European Journal

Controlling Regioselectivity in Palladium‐Catalyzed C−H Activation/Aryl–Aryl Coupling of 4‐Phenylamino[2.2]paracyclophane

Published: 18 September 2020

Author(s): Christoph Zippel, Eduard Spuling, Zahid Hassan, Mika Polamo, Martin Nieger, Stefan Bräse

Abstract Selective activation/functionalization of C−H bonds has emerged as an atom‐ and step‐economical process at the forefront of modern synthetic chemistry. This work reports palladium‐catalyzed exclusively para‐selective C−H activation/aryl–aryl bond formation with a preference over N‐arylation under the Buchwald–Hartwig amination reaction of 4‐phenylamino[2.2]paracyclophane. This innovative synthetic strategy allows a facile preparation of [2.2]paracyclophane derivatives featuring...

Chemistry - A European Journal

Controlling Regioselectivity in Palladium‐Catalyzed C−H Activation/Aryl–Aryl Coupling of 4‐Phenylamino[2.2]paracyclophane

Published: 18 September 2020

Author(s): Christoph Zippel, Eduard Spuling, Zahid Hassan, Mika Polamo, Martin Nieger, Stefan Bräse

Chemistry - A European Journal

Semihydrogenation of Alkynes Catalyzed by a Pyridone Borane Complex: Frustrated Lewis Pair Reactivity and Boron–Ligand Cooperation in Concert

Published: 18 September 2020

Author(s): Felix Wech, Max Hasenbeck, Urs Gellrich

Abstract The metal‐free cis selective hydrogenation of alkynes catalyzed by a boroxypyridine is reported. A variety of internal alkynes are hydrogenated at 80 °C under 5 bar H2 with good yields and stereoselectivity. Furthermore, the catalyst described herein enables the first metal‐free semihydrogenation of terminal alkynes. Mechanistic investigations, substantiated by DFT computations, reveal that the mode of action by which the boroxypyridine activates H2 is reminiscent of the reactivity of...

Chemistry - A European Journal

Synthesis and Characterization of the Tetrakis(pentafluoroethyl)aluminate

Published: 18 September 2020

Author(s): Natalia Tiessen, Beate Neumann, Hans‐Georg Stammler, Berthold Hoge

ChemBioChem

Bifunctional Reagents for Formylglycine Conjugation: Pitfalls and Breakthroughs

Published: 18 September 2020

Author(s): Nils Janson, Tobias Krüger, Lennard Karsten, Mareile Boschanski, Thomas Dierks, Kristian M. Müller, Norbert Sewald

Abstract Formylglycine‐generating enzymes specifically oxidize cysteine within the consensus sequence CxPxR to Cα‐formylglycine (FGly). This noncanonical electrophilic amino acid can subsequently be addressed selectively by bioorthogonal hydrazino‐iso‐Pictet‐Spengler (HIPS) or Knoevenagel ligation to attach payloads like fluorophores or drugs to proteins to obtain a defined payload‐to‐protein ratio. However, the disadvantages of these conjugation techniques include the need for a large excess...

ChemBioChem

Selenoimidazolium Salts as Supramolecular Reagents for Protein Alkylation

Published: 18 September 2020

Author(s): David Lim, Xiaojin Wen, Florian P. Seebeck

Abstract Se‐benzyl selenoimidazolium salts are characterized by remarkable alkyl‐transfer potential under physiological conditions. Structure‐activity relationship studies show that selective monoalkylation of primary amines depends on supramolecular interactions between the selenoimidazole leaving group and the target nucleophile. We demonstrate that these reagents can be used for site‐selective and nearly quantitative modification of the model protein lysozyme on Lys13, bypassing the higher...

ChemBioChem

Enantioselective Cascade Biocatalysis for Deracemization of Racemic β‐Amino Alcohols to Enantiopure (S)‐β‐Amino Alcohols by Employing Cyclohexylamine Oxidase and ω‐Transaminase

Published: 18 September 2020

Author(s): Jian‐Dong Zhang, Ya‐Wen Chang, Rui Dong, Xiao‐Xiao Yang, Li‐Li Gao, Jing Li, Shuang‐Ping Huang, Xing‐Mei Guo, Chao‐Feng Zhang, Hong‐Hong Chang

Abstract Optically active β‐amino alcohols are very useful chiral intermediates frequently used in the preparation of pharmaceutically active substances. Here, a novel cyclohexylamine oxidase (ArCHAO) was identified from the genome sequence of Arthrobacter sp. TYUT010‐15 with the R‐stereoselective deamination activity of β‐amino alcohol. ArCHAO was cloned and successfully expressed in E. coli BL21, purified and characterized. Substrate‐specific analysis revealed that ArCHAO has high activity...

ChemCatChem

Active Learning A Neural Network Model for Gold Clusters & Bulk From Sparse First Principles Training Data

Published: 18 September 2020

Author(s): Troy D. Loeffler, Sukriti Manna, Tarak K. Patra, Henry Chan, Badri Narayanan, Subramanian Sankaranarayanan

ChemCatChem

Influence of Aryl Substituents on the Alignment of Ligands in the Dirhodium Tetrakis(1,2,2‐Triarylcyclopropane‐ carboxylate) Catalysts

Published: 18 September 2020

Author(s): Zhi Ren, Djamaladdin G. Musaev, Huw M. L. Davies

Abstract Computational studies revealed that dirhodium tetrakis(1,2,2‐triarylcyclopropanecarboxylate) (Rh2(TPCP)4) catalysts adopt distinctive high symmetry orientations, which are dependent on the nature of the aryl substitution pattern. The parent catalyst, Rh2(TPCP)4, and those with a p‐substituent at the C1 aryl, such as Rh2(p‐BrTPCP)4 and Rh2(p‐PhTPCP)4, adopt a C2‐symmetric structure. Rh2(3,5‐di(p‐tBuC6H4)TPCP)4, 3,5‐disubstituted at the C1 aryl, adopts a D2‐symmetric structure, whereas...