Robby Vroemans

Publication date: June 2022

Source: Trends in Chemistry, Volume 4, Issue 6

Author(s): Jianbin Li, Chia-Yu Huang, Chao-Jun Li

Journal of Porphyrins and Phthalocyanines, Volume 26, Issue 04, Page 348-354, April 2022.
The innovation of new synthetic strategies to assemble functional materials is of the utmost importance. Herein, a light harvesting [3]rotaxane 7 was designed and synthesized by threading alkyne-functionalized dibenzyl ammonium 5 into dibenzo-24-crown-8 ether macrocycles of Zn porphyrin 4 followed by stoppering the resulting [3]pseudorotaxane 8 with four azide-functionalized boron-dipyrrin (BODIPY) 6 moieties through the copper(I)-catalyzed Huisgen alkyne-azide 1,3-dipolar cycloaddition (CuAAC “click” reaction). The photophysical properties of the resulting [3]rotaxane were investigated by UV-Vis absorption and fluorescence spectroscopy. The absorption spectrum of 7 demonstrated that both Zn porphyrin and BODIPY moieties of 7 retain their spectroscopic properties thus indicating negligible interaction between them in the ground state. In addition, fluorescence studies of the resulting [3]rotaxane 7 showed that the selective excitation of BODIPY moieties of 7 resulted in an efficient photo-induced energy transfer from the four peripheral BODIPY to the central Zn porphyrin thus imitating the natural photosynthesis processes.

A class of facilely tunable, [2.2]paracyclophane-derived chiral arene ligands has been developed, by which a ruthenium(II)-catalyzed asymmetric C−H activation of N-methoxybenzamides with alkynes was achieved, affording a series of axially chiral isoquinolones in up to 99 % yield with up to 96 % ee. This work opens up a new avenue to achieve asymmetric C−H activation by using a chiral arene ligand as stereocontroller.

Abstract

Development of chiral ligands is the most fundamental task in metal-catalyzed asymmetric synthesis. In the last 60 years, various kinds of ligands have been sophisticatedly developed. However, it remains a long-standing challenge to develop practically useful chiral η⁶-arene ligands, thereby seriously hampering the asymmetric synthesis promoted by arene-metal catalysts. Herein, we report the design and synthesis of a class of readily tunable, C ₂-symmetric chiral arene ligands derived from [2.2]paracyclophane. Its ruthenium(II) complexes have been prepared and successfully applied in the enantioselective C−H activation to afford a series of axially chiral isoquinolones (up to 99 % yield and 96 % ee). This study not only lays chemists’ longstanding doubts about whether it is possible to use chiral arene ligands to stereocontrol ruthenium(II)-catalyzed asymmetric C−H activation, but also opens up a new avenue to achieve asymmetric C−H activation.

Nature, Published online: 19 April 2022; doi:10.1038/d41586-022-01087-2

Influential panel’s recommendation makes the ice giant a likely destination for a flagship space mission.

We herein reported the synthesis of organophosphorus(V) compounds through the coupling of readily available starting materials in the presence of recyclable g-CN as photocatalyst. These reactions showed wide functional group tolerance and were performed at rt under visible-light irradiation. The catalyst could be easily separated and reused, thus implying the great potential of use in industry for larger-scale synthesis.

Abstract

The development of metal-free chemical process with recyclable heterogeneous catalyst under ambient conditions is highly desired in industrial production, especially for pharmaceutical purpose. We herein reported the efficient synthesis of pharmaceutically relevant organophosphorus(V) compounds through the coupling of readily available starting materials in the presence of insoluble carbon nitride (g-CN) as recyclable photocatalyst. These reactions showed wide functional group tolerance and were performed at room temperatures under visible-light irradiation. The heterogeneous g-CN photocatalyst could be easily separated from the crude reaction mixture and reused for several cycles without decreasing the reaction efficiency, thus implying the great potential of use in industrial manufacture for larger-scale synthesis.

Synthesis
DOI: 10.1055/s-0040-1719905

Nitro compounds are vital raw chemicals that are widely used in academic laboratories and industries for the preparation of various drugs, agrochemicals, and materials. Thus, nitrating reactions are of great importance for chemists and are even taught in schools as one of the fundamental transformations in organic synthesis. Since the discovery of the first nitrating reactions in the 19th century, progress in this field has been constant. Yet, for many years the classical electrophilic nitration approach using a mixture of strong mineral acids dominated the field. However, in recent decades, the attention of researchers has focused on new reactivity and new reagents that can provide access to nitro compounds in a practical and straightforward way under mild reaction conditions. Organic nitrating reagents have played a special role in this field since they have enhanced reactivity. They also allow nitration to be carried out in an ecofriendly and sustainable manner. This review examines the development and application of organic nitrating reagents.1 Introduction2 Organic Nitrating Reagents2.1 Alkyl Nitrites2.2 Nitroalkanes2.3 Alkyl Nitrates2.4 N-Nitroamides2.5 N-Nitropyrazole2.6 N-Nitropyridinium Salts3 Organic Nitrating Reagents Generated In Situ3.1 Acyl Nitrates3.2 Trimethylsilyl Nitrate3.3 Nitro Onium Salts4 Organic Nitronium Salts5 Organic Nitrates and Nitrites5.1 Ammonium Nitrates5.2 Heteroarylium Nitrates5.3 Other Organic Nitrates5.4 Organic Nitrites6 Conclusion and Outlook
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Nature, Published online: 12 April 2022; doi:10.1038/d41586-022-01025-2

A satellite will scour the Milky Way for exoplanets orbiting stars just like the Sun.

Herein, palladium(II)-catalyzed halogenation of 2-phenylquinazolines using N-halosuccinimides as halogen sources was described via C−H activation under mild reaction conditions. A series of halogen-substituted 2-arylquinazolines were synthesized through C−H functionalization.

Abstract

An efficient quinazoline-assisted ortho-halogenation of 2-arylquinazolines has been developed using N-halosuccinimides as halogen sources with Pd(II)-catalyzed C−H bond activation. No additional ligand and oxidant are required. This protocol is highly regioselective and applicable to a broad range of quinazoline substrates bearing different functional groups, giving yields of up to 98 %. The mechanism of the quinazoline ortho-halogenation was investigated by comprehensive experimentation.

Nature, Published online: 07 April 2022; doi:10.1038/d41586-022-01015-4

Three experts explain how to use design principles to better communicate scientific data.

Nature, Published online: 06 April 2022; doi:10.1038/d41586-022-00946-2

After controlling for importance, analysis finds that papers with funnier titles get more citations. But some researchers question these results.

Electron-rich aryl acetates derived from (renewable) phenolics were selectively reduced to the corresponding arenes using pinacolborane (HBpin) and a nickel-N-heterocyclic carbene (NHC) catalytic system in the green solvent dimethylcarbonate (DMC). The method is applicable to 4-propylguaiacyl acetate derived from pine wood.

Abstract

Acetate serves as a renewable and easily installed leaving group for selective deoxygenation of phenolics (ArOH). Ni-catalyzed hydrodeacetoxylation of aryl acetates (Ar−OAc) with HBpin in a green carbonate solvent selectively delivers the corresponding deoxygenated arenes (ArH). The method is also applicable to highly challenging guaiacyl and syringyl acetates, leaving −OMe groups intact without arene reduction. Renewable 4-propylguaiacol obtained from pine can also be transformed without significant loss in yield versus oil derived feedstock. The observed chemoselectivity for Ar−OAc versus ArO−Ac bond cleavage was rationalized based on mechanistic experiments and DFT calculations. ArOH side-product formation is attributed to direct competitive Ni-catalyzed reduction of the C=O bond. Hydrodeacyloxylation of a set of aryl alkanoates featured interesting chemoselectivity with a dramatic influence of the length and structure of the alkyl chain on catalysis.

Kenichi Fukui jointly shared the 1981 Nobel Prize in Chemistry with Roald Hoffmann “for their theories, developed independently, concerning the course of chemical reactions.” This paper takes the reader along the path taken by Fukui in the 1950s and early 1960s that led to his 1964 breakthrough publication of orbital symmetry control of the Diels-Alder reaction.

Abstract

In 1964, Kenichi Fukui published a chapter in a book honoring the career of Robert S. Mulliken. While most of that chapter is a review of Fukui's previously published research dealing with frontier molecular orbital theory and organic reactions, one section provided a frontier molecular orbital explanation of the mechanism of the Diels-Alder reaction. Fukui concluded that the “symmetry relation of wave functions of both dienes and dienophiles” control the course of this reaction. Thus, Fukui's paper was a precursor to Woodward and Hoffmann's 1965 papers that proposed orbital symmetry control of what would later be termed “pericyclic reactions.” Fukui published numerous papers in the 1950s and 1960s, many of which were expositions of his research in theoretical chemistry. Eight of those Fukui papers were direct precursors to his breakthrough 1964 publication. This paper presents the intellectual and scientific path that Fukui took from the early 1950s to 1964 to his award-winning publication.

Following in the footsteps of Robert S. Mulliken, one of the founders of molecular orbital theory, Kenichi Fukui developed frontier molecular orbital theory and applied it to the solution of many mechanistic problems, including the mechanism of the Diels-Alder reaction in 1964. This paper reviews Fukui's theoretical achievements up to and including his Nobel Prize achievement.

Abstract

In 1981, Kenichi Fukui shared the Nobel Prize in Chemistry with Roald Hoffmann “for their theories, developed independently, concerning the course of chemical reactions.” In 1964, Fukui used his frontier molecular orbital theory to reveal the mechanism of the Diels-Alder reaction, a prototypical pericyclic cycloaddition reaction. Fukui revealed this molecular orbital symmetry explanation a year before Woodward and Hoffmann's first publication on “the conservation of orbital symmetry.” As detailed in this paper, during the 1960s and early 1960s, Fukui was involved in several major programs in synthesis and polymer chemistry as well as aspects of theoretical chemistry quite distant from his contributions to the orbital symmetry research that preceded Woodward and Hoffmann. In this paper, a detailed examination of Fukui's pre-1965 research is discussed. This is Paper 4 – Part III of a trilogy that deals with Fukui's Nobel Prize research and is part of a 27-paper series on the history of the development of the Woodward-Hoffmann rules.