LongLarf

Nature Communications, Published online: 14 May 2021; doi:10.1038/s41467-021-23101-3

Nature, Published online: 12 May 2021; doi:10.1038/d41586-021-01205-6

Nature, Published online: 12 May 2021; doi:10.1038/d41586-021-01273-8

Publication date: 2 July 2021

Source: Tetrahedron, Volume 91

Author(s): Yunyu Xiang, Ganfei Zeng, Xiaoyan Sang, Xiaofang Li, Qiuping Ding, Yiyuan Peng

Nature Catalysis, Published online: 29 April 2021; doi:10.1038/s41929-021-00603-3

Publication date: 18 June 2021

Source: Tetrahedron, Volume 90

Author(s): Michael Hoffelner, Werner Seebacher, Usama Hassan, Andreas Leitner, Robert Weis, Robert Saf

A rhodium(III)-catalyzed dealkenylative arylation of alkenes and 1,3-dienes with arylboronic compounds has been developed to provide an unconventional access to bi(hetero)aryls with excellent chemo-selectivity.

Abstract

The C−C bond formation reaction represents a fundamental and important transformation in synthetic chemistry, and exploring new types of C−C bond formation reactions is recognized as appealing, yet challenging. Herein, we disclose the first example of rhodium-catalyzed dealkenylative arylation of alkenes with arylboronic compounds, thereby providing an unconventional access to bi(hetero)aryls with excellent chemoselectivity. In this method, C(aryl)−C(alkenyl) and C(alkenyl)−C(alkenyl) bonds in various alkenes and 1,3-dienes can be cleaved via a hydrometalation and followed by β-carbon elimination pathway for Suzuki–Miyaura reactions. Furthermore, a series of novel organic fluorescent molecules with excellent photophysical properties has been efficiently constructed with this protocol.

Nature, Published online: 28 April 2021; doi:10.1038/s41586-021-03401-w

Synthesis
DOI: 10.1055/a-1394-7511

The formation of the C=N bond in recent studies on heterocyclic compounds via the aza-Wittig reaction is reviewed. Furthermore, two different strategies for the formation of heterocyclic compounds, including intermolecular and intramolecular aza-Wittig reactions are described. The primary aim of this review is to provide up-to-date information on the application of the aza-Wittig reaction in the synthesis of a wide range of N-containing heterocyclic compounds in the chemical literature since 2010.1 Introduction2 Mechanism of the Staudinger and Aza-Wittig Reactions3 Intramolecular Aza-Wittig Reaction4 Intermolecular Aza-Wittig Reaction5 Conclusion
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Article in Thieme eJournals:
Table of contents  |  Abstract  |  Full text

Building blocks: This critical review discusses recent developments on the value addition of biomass-derived levulinic acid (LA), focusing on the reactivity patterns of the functionalities present in LA. The effect of catalysts, reagents, and reaction conditions on the selectivity and yield of various crucial derivatives of LA have been exemplified. This work will enkindle ideas in designing novel preparative routes and expanding the derivative chemistry of LA.

Abstract

Levulinic acid (LA) is one of the most prominent biomass-derived chemical building blocks that can be transformed into specialty chemicals like fuels, solvents, monomers for polymers, plasticizers, surfactants, agrochemicals, and pharmaceuticals. Over the past three decades, an enormous amount of research data have been acquired on the preparation and downstream value addition of LA, and these works have been reviewed. However, considering the astonishing number of publications appearing every year on LA derivatives, the periodical review of recent works focusing on unique aspects of chemistry must be undertaken to critically evaluate the achievements to date, reassess the challenges, and recognize new opportunities. This review discusses the chemical-catalytic synthesis of various derivatives of LA by focusing on its functionalities and reactivity patterns. Recent literature on some crucial derivatives such as γ-valerolactone, 4,4’-diphenolic acid, and ethyl levulinate have been tabulated and discussed. The synthetic interconversion between various derivatives, mechanistic insights, critical analysis of the reaction parameters toward selective preparation of various derivatives, and their potential commercial applications have been elaborated using predominantly heterogeneous catalysts. A critical assessment of the relative advantages and shortcomings of the existing synthetic strategies for various derivatives of LA has been presented to enkindle fresh ideas.

Abstract

α-Aminoalkylboronic acids display a distinct role in medicinal chemistry, and their utility has been demonstrated by the successful commercialization of three drugs: bortezomib, ixazomib, and vaborbactam. Just as α-aminoalkylboronic acids are a bioisostere of α-amino acids, β-aminoalkylboronates are a bona fide bioisostere of β-amino acids, thus they also hold promising potential in drug discovery. Moreover, β-aminoalkylboronates are versatile synthetic intermediates that are amenable to many of the established C−B bond derivatization reactions of chiral optically enriched alkylboronates, leading to the stereocontrolled preparation of valued classes of products such as β-amino alcohols, 1,2-diamines, and hemiboronic acid heterocycles. In addition, β-aminoalkylboronates were shown to act as catalysts in certain organic reactions. This review presents an overview of the strengths and limitations of current preparative methods to access β-aminoalkylboronic acid derivatives stereoselectively with various substitution patterns. Strategically, several disconnections can be exploited to establish both functional groups. Some of the key methods include the classical Matteson asymmetric homologation chemistry, transition metal-catalyzed aminoboration of alkenes and formal hydroboration of enamine derivatives, nucleophilic additions of boryl-substituted carbanions onto N-functionalized imines, borylative ring openings of aziridines, and functionalization of alpha-boryl aldehydes.

Abstract

Reduction of phosphine oxides into the corresponding phosphines using PhSiH₃ as a reducing agent and Ph₃C⁺[B(C₆F₅)₄]⁻ as an initiator is described. The process is highly efficient, reducing a broad range of secondary and tertiary alkyl and arylphosphines, bearing various functional groups in generally good yields. The reaction is believed to proceed through the generation of a silyl cation, which reaction with the phosphine oxide provides a phosphonium salt, further reduced by the silane to afford the desired phosphine along with siloxanes.

The “larger” analog of protonated sulfuric acid, [H₃SO₄]⁺, the silylated oxosulfonium ion, [(Me₃Si)₃SO₄]⁺, was obtained in the reaction of silylated sulfuric acid with a [Me₃Si]⁺ transfer reagent such as [Me₃Si−H−SiMe₃]⁺[wca]⁻, when a weakly coordinating anion ([wca]⁻) is used as counterion.

Abstract

The chemistry of silylated sulfuric acid, O₂S(OSiMe₃)₂ (T₂SO₄, T=Me₃Si; also known as bis(trimethylsilyl) sulfate), has been studied in detail with the aim of synthesizing the formal autosilylation products of silylated sulfuric acid, [T₃SO₄]⁺ and [TSO₄]⁻, in analogy to the known protonated species, [H₃SO₄]⁺ and [HSO₄]⁻. The synthesis of the [TSO₄]⁻ ion only succeeds when a base, such as OPMe₃ that forms a weakly coordinating cation upon silylation, is reacted with T₂SO₄, resulting in the formation of [Me₃POT]⁺[TSO₄]⁻. [T₃SO₄]⁺ salts could be isolated starting from T₂SO₄ in the reaction with [T−H−T]⁺[B(C₆F₅)₄]⁻ or T⁺[CHB₁₁Br₆H₅]⁻ when a weakly coordinating anion is used as counterion. All silylated compounds could be crystallized and structurally characterized.