An asymmetric 3‐component reaction between EthynylBenziodoXoles (EBXs), 2,2,2‐trifluorodiazoethane and nucleophiles catalyzed by a CuI‐BOX (Bisoxazoline) catalyst is described. This protocol gives ...access to chiral trifluoromethylated propargyl ethers and anilines, which are valuable building blocks in synthetic and medicinal chemistry. The reaction proceeds with high enantioselectivity and yield with different nucleophiles such as primary, secondary and tertiary alcohols, as well as both electron‐rich and electron‐poor anilines. Aryl‐, alkyl‐ and silyl‐substituted alkynes can be successfully introduced as electrophiles. In case of chiral substrates, high catalyst control was observed, leading to good diastereoselectivity.
The asymmetric synthesis of trifluoromethylated propargylic ethers and amines is described. The reaction proceeds with high enantioselectivity using a simple chiral CuI‐BOX system and tolerates a broad range of alcohol, aniline and alkyne substitution. With chiral alcohols, a high diastereoselectivity is observed, indicating good catalyst stereocontrol.
A metal-free dehydrogenative lactonization of 2-arylbenzoic acids at room temperature was developed. This work illustrates the first application of visible-light photoredox catalysis in the ...preparation of benzo-3,4-coumarins, an important structural motif in bioactive molecules. The combination of photocatalyst Acr+-Mes with (NH4)2S2O8 as a terminal oxidant provides an economical and environmentally benign entry to different substituted benzocoumarins. Preliminary mechanistic studies suggest that this reaction most likely occurs through a homolytic aromatic substitution pathway.
An operationally simple method is disclosed for the decarboxylative cyanation of aliphatic carboxylic acids at room temperature. Riboflavin tetraacetate, which is an inexpensive organic ...photocatalyst, promotes the oxidation of carboxylic acids upon visible-light activation. After decarboxylation, the generated radicals are trapped by TsCN, yielding the desired nitriles without any further additive, in a redox-neutral process. Importantly, this protocol can be adapted to flow conditions.
The gem-aminoalkynylation of fluorinated diazo compounds catalyzed by a simple Cu(I) salt is described. This three-component reaction allows the synthesis of propargylic amines with broad functional ...group tolerance. Both electron-rich and electron-poor anilines can be used as nucleophiles and alkyl-, aryl-, and silyl-substituted EthynylBenziodoXoles (EBX) as electrophiles.
We describe herein a transition‐metal‐free method for the decarboxylative generation of radicals from carboxylic acids and their 1,4‐addition to Michael acceptors. The Fukuzumi catalyst ...(9‐mesitylene‐10‐methylacridinium perchlorate, Acr‐MesClO4) enabled this transformation under visible‐light irradiation at room temperature with CO2 as the only byproduct. The scope and limitations of this protocol were examined by using a range of Michael acceptors (15 examples) and carboxylic acids (18 examples). The use of 3‐hydroxypivalic acid in this protocol allowed the straightforward formation of a diastereomerically pure δ‐lactone. Moreover, when a homoallylic acid was used, a radical cascade reaction took place with the formation of three C–C bonds.
The decarboxylative alkylation of carboxylic acids can be efficiently promoted by visible light under air at room temperature by using 9‐mesitylene‐10‐methylacridinium perchlorate (Acr‐MesClO4) as photocatalyst. A range of readily available starting materials are well tolerated in this transition‐metal‐free protocol.
Manipulation of magnetisation with ultrashort laser pulses is promising for information storage device applications. The dynamics of the magnetisation response depends on the energy transfer from the ...photons to the spins during the initial laser excitation. A material of special interest for magnetic storage are FePt nanoparticles, for which switching of the magnetisation with optical angular momentum was demonstrated recently. The mechanism remained unclear. Here we investigate experimentally and theoretically the all-optical switching of FePt nanoparticles. We show that the magnetisation switching is a stochastic process. We develop a complete multiscale model which allows us to optimize the number of laser shots needed to switch the magnetisation of high anisotropy FePt nanoparticles in our experiments. We conclude that only angular momentum induced optically by the inverse Faraday effect will provide switching with one single femtosecond laser pulse.
We describe herein a direct decarboxylative allylation of aliphatic carboxylic acids with allylsulfones using visible light and riboflavin tetraacetate (RFTA) as photocatalyst. The reaction proceeds ...at room temperature tolerating a wide range of functionalities, avoiding the use of external bases or additives. Mechanistic studies support that alkyl radicals are involved in the reaction and that a true photocatalytic cycle is operating. It is proposed that the carboxylic acid is deprotonated by RFTA·–, and the corresponding carboxylate acts as a reductive quencher of RFTA*, which after decarboxylation produces the alkyl radical. The methodology was adapted to prepare benzothiazoles substituted at C2, by reacting some carboxylic acids with 2‐(phenylsulfonyl)benzothiazole. The number of carboxylic acids suitable for this arylation was lower than for the allylation and this different reactivity was briefly commented.
The direct decarboxylative allylation of carboxylic acids with allylsulfones can be efficiently promoted at room temperature by visible light using inexpensive riboflavin tetraacetate as photocatalyst in the absence of base. Under similar conditions, some carboxylic acids can be successfully used in the decarboxylative homolytic aromatic substitution of 2‐(phenylsulfonyl)benzothiazole.
Magnetization manipulation is essential for basic research and applications. A fundamental question is, how fast can the magnetization be reversed in nanoscale magnetic storage media. When subject to ...an ultrafast laser pulse, the speed of the magnetization dynamics depends on the nature of the energy transfer pathway. The order of the spin system can be effectively influenced through spin-flip processes mediated by hot electrons. It has been predicted that as electrons drive spins into the regime close to almost total demagnetization, characterized by a loss of ferromagnetic correlations near criticality, a second slower demagnetization process takes place after the initial fast drop of magnetization. By studying FePt, we unravel the fundamental role of the electronic structure. As the ferromagnet Fe becomes more noble in the FePt compound, the electronic structure is changed and the density of states around the Fermi level is reduced, thereby driving the spin correlations into the limit of critical fluctuations. We demonstrate the impact of the electrons and the ferromagnetic interactions, which allows a general insight into the mechanisms of spin dynamics when the ferromagnetic state is highly excited, and identifies possible recording speed limits in heat-assisted magnetization reversal.
An asymmetric 3‐component reaction between EthynylBenziodoXoles (EBXs), 2,2,2‐trifluorodiazoethane and nucleophiles catalyzed by a CuI‐BOX (Bisoxazoline) catalyst is described. This protocol gives ...access to chiral trifluoromethylated propargyl ethers and anilines, which are valuable building blocks in synthetic and medicinal chemistry. The reaction proceeds with high enantioselectivity and yield with different nucleophiles such as primary, secondary and tertiary alcohols, as well as both electron‐rich and electron‐poor anilines. Aryl‐, alkyl‐ and silyl‐substituted alkynes can be successfully introduced as electrophiles. In case of chiral substrates, high catalyst control was observed, leading to good diastereoselectivity.
The asymmetric synthesis of trifluoromethylated propargylic ethers and amines is described. The reaction proceeds with high enantioselectivity using a simple chiral CuI‐BOX system and tolerates a broad range of alcohol, aniline and alkyne substitution. With chiral alcohols, a high diastereoselectivity is observed, indicating good catalyst stereocontrol.
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