LongLarf

Nature, Published online: 22 January 2020; doi:10.1038/d41586-019-03949-8

Signalling from the sympathetic nervous system of mice when subjected to stress leads to the depletion of a stem-cell population in their hair follicles. This discovery sheds light on why stress turns hair prematurely grey.

Abstract

Direct electrochemical oxidative functionalization of caffeine under metal‐free and external‐oxidant‐free conditions was achieved. Nucleophiles such as various substituted pyrazoles, alcohols, and sodium trifluoromethanesulfonate can be utilized with high diastereoselectivity for the dearomatizative functionalization of caffeine. In addition, selective C2 functionalization of caffeine has also been realized with the modification of solvent and reaction time. A gram‐scale experiment demonstrates the potential application in the derivatization of caffeine.

Publication date: 13 February 2020

Source: Chem, Volume 6, Issue 2

Author(s): Kalipada Jana, Anup Bhunia, Armido Studer

Metal ionic liquids: Here we propose for the first time the utilization of metal ionic liquids (MILs) for the chemical fixation CO₂ at mild conditions, where MIL plays as both reaction media and catalyst. This strategy is efficient, facile, environmentally benign, involves no additional catalyst and the MIL can be easily recycled after reaction.

Abstract

CO₂ cycloaddition is an important reaction for chemical fixation of CO₂. It is desirable to design facile and green route for the efficient CO₂ cycloaddition reaction, especially at ambient conditions. Here we propose a novel route for CO₂ cycloaddition by utilizing metal ionic liquid (MIL) as both reaction media and catalyst. Outstandingly, propylene oxide can be completely converted to propylene carbonate with more than 99.0 % yield and more than 99 % selectivity at room temperature and atmospheric pressure. This strategy is efficient, facile, environmentally benign, which involves no additional catalyst and can easily recycle the MIL after reaction. It has potential for the practical procedure of gas separation and CO₂ utilization in industrial waste gas.

An alkoxycarbonylation reaction protocol for the synthesis of 3‐arylpropionate esters starting from sec‐benzylic ethers and demonstration of a comparable reaction behavior to established olefin, alcohol, or aryl halide systems.

Herein, we report the palladium‐catalyzed synthesis of 3‐arylpropionate esters starting from secondary benzylic ethers. With this investigation it could be shown that ethers are suitable starting materials in addition to the established carbonylation reactions of olefins, alcohols, or aryl halides.

Nature Catalysis, Published online: 20 January 2020; doi:10.1038/s41929-019-0385-5

Advances in enzyme performance and capabilities are making them increasingly attractive to synthetic chemists. In this Review Chen and Arnold outline the ways that enzymes have been engineered to achieve reactivities well beyond their original functions.

Nature Catalysis, Published online: 20 January 2020; doi:10.1038/s41929-019-0415-3

Forming carbon–carbon bonds at the expense of two C–H bonds is difficult, but attractive, as it reduces the number of chemical steps during synthesis by avoiding prefunctionalization. Here such a method is reported, involving an interrupted Pummerer reaction and a photoredox-catalysed coupling.

Nature Chemistry, Published online: 20 January 2020; doi:10.1038/s41557-019-0407-6

Meroterpenoids are mixed terpenoid–polyketide natural products that exhibit a range of biological activities. A hybrid synthetic strategy that combines biocatalytic and radical-based methods has now been developed and it enables eight different oxidized meroterpenoids to be made in just 7–12 steps from commercially available materials.

Nature, Published online: 15 January 2020; doi:10.1038/d41586-020-00101-9

Global study highlights long hours, poor job security and mental-health struggles.

Bismuth catalysis has traditionally relied on the Lewis acidic properties of the element in a fixed oxidation state. In this paper, we report a series of bismuth complexes that can undergo oxidative addition, reductive elimination, and transmetallation in a manner akin to transition metals. Rational ligand optimization featuring a sulfoximine moiety produced an active catalyst for the fluorination of aryl boronic esters through a bismuth (III)/bismuth (V) redox cycle. Crystallographic characterization of the different bismuth species involved, together with a mechanistic investigation of the carbon-fluorine bond-forming event, identified the crucial features that were combined to implement the full catalytic cycle.

Synlett
DOI: 10.1055/s-0039-1690782

An unexpected four-step reaction sequence was discovered in the course of investigation of the interaction between 3-(furan-2-yl)allylamines and bromomaleic anhydride. This conversion begins with the initial N-acylation of the allylamines by the anhydride, followed by intramolecular Diels–Alder reaction, which is accompanied by a dehydrohalogenation, and ends with the formation of partially unsaturated furo[2,3-f]isoindoles followed by transposition of aromaticity from the furan moiety to the neighboring cyclohexane ring. The reaction between 3-(furan-3-yl)allylamines and bromomaleic anhydride does not stop at a furo[2,3-f]isoindole formation step, but proceeds further with the cleavage of the furan ring in a 100% atom-efficient fashion to provide polysubstituted isoindoline-4-carboxylic acids.
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© Georg Thieme Verlag Stuttgart · New York

Article in Thieme eJournals:
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Nature Catalysis, Published online: 13 January 2020; doi:10.1038/s41929-019-0406-4

The organocatalysed addition of aldehydes to nitroolefins is an extremely well-studied reaction that almost exclusively provides the syn-configured products. Here a general method to reverse the diastereoselectivity is reported, whereby a tripeptide catalyst consistently provides the anti product with high selectivity.

Nature Catalysis, Published online: 06 January 2020; doi:10.1038/s41929-019-0410-8

Genetic incorporation of unnatural amino acids into proteins broadens the possibilities of enzyme design. This Perspective discusses the exciting opportunities for biocatalysis offered by this method — such as new-to-nature catalytic activities — and potential benefits over classical enzyme engineering.

Synlett
DOI: 10.1055/s-0039-1690773

Photoacids are molecules that become more acidic upon absorption of light. They are widely utilized in a variety of fields, such as organic synthesis, molecular switching agents, and photodynamic therapy. Currently, the activity of most photoacids is induced by UV light, which limits their applications by the synthetic community. In this ­Synpacts article, we highlight our recent development of visible-light-­induced photoacids and their application in glycosylation reactions.1 Introduction2 Visible-Light-Induced Photoacids3 Synthesis of 2-Deoxyglycosides by Visible-Light-Induced Photoacid Catalysis4 Conclusion
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© Georg Thieme Verlag Stuttgart · New York

Article in Thieme eJournals:
Table of contents  |  Abstract  |  Full text

A straightforward and quantitative strategy for the preparation of valuable AgOCF₃ at room temperature is reported, along with AgOCF₃ performance in trifluoromethoxylations or as reservoir for O=CF₂. This enabled the direct, practical and safe synthesis of valuable N‐alkyl/aryl and N−CF₃ carbamoyl fluorides from secondary amines and isothiocyanides, respectively.

Abstract

The development of innovative fluorination strategies is greatly dependent also on the availability, safety and practicability of available fluorinating reagents. We herein show a straightforward and quantitative strategy for the preparation of valuable AgOCF₃ at room temperature and showcase its performance in trifluoromethoxylations or as reservoir for O=CF₂. This enabled the direct, practical and safe synthesis of valuable N‐alkyl/aryl and N−CF₃ carbamoyl fluorides from secondary amines and isothiocyanides, respectively. Our mechanistic data indicate that AgOCF₃ does not liberate O=CF₂ until it is activated by a nucleophilic co‐reagent, reinforcing the stability of the salt under our new preparation strategy.

The enantio‐ and diastereoselective, copper‐catalyzed three‐component coupling of imines, 1,3‐enynes, and diborons delivers complex, chiral homopropargyl amines; useful building blocks on the way to biologically‐ and medicinally‐relevant compounds. In particular, functionalized homopropargyl amines bearing up to three contiguous stereocenters can be prepared in a single step.

Abstract

An efficient, enantio‐ and diastereoselective, copper‐catalyzed coupling of imines, 1,3‐enynes, and diborons is reported. The process shows broad substrate scope and delivers complex, chiral homopropargyl amines; useful building blocks on the way to biologically‐relevant compounds. In particular, functionalized homopropargyl amines bearing up to three contiguous stereocenters can be prepared in a single step.