LongLarf

Thermal and electrochemical degradation reactions of a common lithium ion battery electrolyte (ethylene carbonate/diethyl carbonate + LiPF₆) were investigated by using isotope labeling studies. Reaction pathways are postulated as well as a fragmentation mechanism assumption for oligomeric compounds depicted.

Abstract

The decomposition of state‐of‐the‐art lithium ion battery (LIB) electrolytes leads to a highly complex mixture during battery cell operation. Furthermore, thermal strain by e.g., fast charging can initiate the degradation and generate various compounds. The correlation of electrolyte decomposition products and LIB performance fading over life‐time is mainly unknown. The thermal and electrochemical degradation in electrolytes comprising 1 m LiPF₆ dissolved in ¹³C₃‐labeled ethylene carbonate (EC) and unlabeled diethyl carbonate is investigated and the corresponding reaction pathways are postulated. Furthermore, a fragmentation mechanism assumption for oligomeric compounds is depicted. Soluble decomposition products classes are examined and evaluated with liquid chromatography‐high resolution mass spectrometry. This study proposes a formation scheme for oligo phosphates as well as contradictory findings regarding phosphate‐carbonates, disproving monoglycolate methyl/ethyl carbonate as the central reactive species.

Organic halides are important building blocks in synthesis, but their use in (photo)redox chemistry is limited by their low reduction potentials. Halogen-atom transfer remains the most reliable approach to exploit these substrates in radical processes despite its requirement for hazardous reagents and initiators such as tributyltin hydride. In this study, we demonstrate that α-aminoalkyl radicals, easily accessible from simple amines, promote the homolytic activation of carbon-halogen bonds with a reactivity profile mirroring that of classical tin radicals. This strategy conveniently engages alkyl and aryl halides in a wide range of redox transformations to construct sp³-sp³, sp³-sp², and sp²-sp² carbon-carbon bonds under mild conditions with high chemoselectivity.

Biopolymers : The selective catalytic synthesis of limonene‐derived monofunctional cyclic carbonates and their subsequent functionalisation via thiol–ene addition and amine ring‐opening is reported. The selective catalytic route to monofunctional limonene carbonates gives straightforward access to monomers for novel bio‐based polymers.

Abstract

The selective catalytic synthesis of limonene‐derived monofunctional cyclic carbonates and their subsequent functionalisation via thiol–ene addition and amine ring‐opening is reported. A phosphotungstate polyoxometalate catalyst used for limonene epoxidation in the 1,2‐position is shown to also be active in cyclic carbonate synthesis, allowing a two‐step, one‐pot synthesis without intermittent epoxide isolation. When used in conjunction with a classical halide catalyst, the polyoxometalate increased the rate of carbonation in a synergistic double‐activation of both substrates. The cis isomer is shown to be responsible for incomplete conversion and by‐product formation in commercial mixtures of 1,2‐limomene oxide. Carbonation of 8,9‐limonene epoxide furnished the 8,9‐limonene carbonate for the first time. Both cyclic carbonates underwent thiol–ene addition reactions to yield linked di‐monocarbonates, which can be used in linear non‐isocyanate polyurethanes synthesis, as shown by their facile ring‐opening with N ‐hexylamine. Thus, the selective catalytic route to monofunctional limonene carbonates gives straightforward access to monomers for novel bio‐based polymers.

Musks odorants are ubiquitous in fine perfumery as well as hygiene products, and are divided into four main families, the nitromusks, the macrocyclic musks, the polycyclic aromatic musks and the alicyclic musks, following their order of appearance on the perfumery market. This article presents the scientific and industrial adventures of the discovery of the polycyclic musks, which mobilized the aromachemistry corporations during the second half of the 20th century in a relentless competition. Research and development strategies are exposed, reactivity, analytical, mechanistic and structure‐activity relationships aspects are discussed as well as some biographical elements of the main scientific actors, and some fine perfumery examples are given as illustrations of their use.

Old complex, new tricks: Ni(COD)(DQ) (COD=1,5‐cyclooctadiene, DQ=duroquinone) is a remarkably stable Ni⁰‐‐olefin complex first described in the 1960s. Its ability to serve as a precatalyst for a variety of nickel‐catalyzed reactions is demonstrated.

Abstract

We report that Ni(COD)(DQ) (COD=1,5‐cyclooctadiene, DQ=duroquinone), an air‐stable 18‐electron complex originally described by Schrauzer in 1962, is a competent precatalyst for a variety of nickel‐catalyzed synthetic methods from the literature. Due to its apparent stability, use of Ni(COD)(DQ) as a precatalyst allows reactions to be conveniently performed without use of an inert‐atmosphere glovebox, as demonstrated across several case studies.

An operationally simple, metal‐free, and site‐selective aromatic C−H alkylation under photoredox catalysis that utilizes equimolar quantities of coupling partners is reported. Experimental and computational studies suggest a unique mechanism, involving cyclopropanation of arene cation radicals and subsequent oxidative ring opening, that allows this transformation to be compatible with a range of aromatic substrates.

Abstract

Expanding the toolbox of C−H functionalization reactions applicable to the late‐stage modification of complex molecules is of interest in medicinal chemistry, wherein the preparation of structural variants of known pharmacophores is a key strategy for drug development. One manifold for the functionalization of aromatic molecules utilizes diazo compounds and a transition‐metal catalyst to generate a metallocarbene species, which is capable of direct insertion into an aromatic C−H bond. However, these high‐energy intermediates can often require directing groups or a large excess of substrate to achieve efficient and selective reactivity. Herein, we report that arene cation radicals generated by organic photoredox catalysis engage in formal C−H functionalization reactions with diazoacetate derivatives, furnishing sp²–sp³ coupled products with moderate‐to‐good regioselectivity. In contrast to previous methods utilizing metallocarbene intermediates, this transformation does not proceed via a carbene intermediate, nor does it require the presence of a transition‐metal catalyst.

Same but different: A new generation of saturated benzene mimetics, 2‐oxabicyclo[2.1.1]hexanes, was developed. These compounds were designed as analogues of bicyclo[1.1.1]pentane with an improved water solubility. Crystallographic analysis of the compounds revealed that they occupy a novel chemical space but resemble meta‐disubstituted benzenes at the same time.

Abstract

A new generation of saturated benzene mimetics, 2‐oxabicyclo[2.1.1]hexanes, was developed. These compounds were designed as analogues of bicyclo[1.1.1]pentane with an improved water solubility. Crystallographic analysis of 2‐oxabicyclo[2.1.1]hexanes revealed that they occupy a novel chemical space, but, at the same time, resemble the motif of meta‐disubstituted benzenes.

Publication date: 3 April 2020

Source: Tetrahedron, Volume 76, Issue 14

Author(s): Nina K. Ratmanova, Ivan A. Andreev, Alexandre V. Leontiev, Daria Momotova, Anton M. Novoselov, Olga A. Ivanova, Igor V. Trushkov

Precise synthesis : The new “built‐in‐base” ligand Neolephos was designed and applied in the Pd‐catalyzed monocarbonylation of 1,3‐diynes. The precise synthesis of conjugated enynes was achieved in good‐to‐high yield with excellent chemo‐ and stereoselectivity. The presented methodology can be used for simple diversification of natural products and pharmaceuticals.

Abstract

For the first time, the monoalkoxycarbonylation of easily available 1,3‐diynes to give synthetically useful conjugated enynes has been realized. Key to success was the design and utilization of the new ligand 2,2′‐bis(tert ‐butyl(pyridin‐2‐yl)phosphanyl)‐1,1′‐binaphthalene (Neolephos), which permits the palladium‐catalyzed selective carbonylation under mild conditions, providing a general preparation of functionalized 1,3‐enynes in good‐to‐high yields with excellent chemoselectivities. Synthetic applications that showcase the possibilities of this novel methodology include an efficient one‐pot synthesis of 4‐aryl‐4H ‐pyrans as well as the rapid construction of various heterocyclic, bicyclic, and polycyclic compounds.

It takes two to tango: Squaramide–quaternary ammonium salt as an efficient binary organocatalyst for the atom‐economic conversion of a plethora of alkyl‐ and aryl‐substituted epoxides and isocyanates into oxazolidinones is described. A mechanism was proposed wherein the nucleophilic ring‐opening operation, and oxo‐ and carbamate‐anions stabilization occur cooperatively towards isocyanate fixation.

Squaramide–quaternary ammonium salt is illustrated as a simple, tunable, and competent metal‐free binary catalytic platform for the atom‐economic conversion of epoxides and isocyanates into oxazolidinones. Although, various metal catalysts have been employed for the title reaction, application of organocatalysis is scarce. At first, a rational survey of catalytic activity of several air‐stable and architecturally distinct squaramides was undertaken. Thereafter, the impact on catalytic capability of different parameters, such as temperature, catalyst loading, and nature of nucleophiles, was examined. This binary organocatalytic system for the oxazolidinone synthesis, composed of a squaramide entity along with a suitable halide anion, was applied to the challenging conversion of a plethora of alkyl‐ and aryl‐substituted epoxides– including disubstituted and enantioenriched ones– and isocyanates into the corresponding oxazolidinones in high‐to‐excellent yields. The time‐dependent formation of oxazolidinone from epoxide and isocyanate was monitored by FTIR‐ATR and ¹H NMR spectroscopy and the scalability of this process was also described. In light of ¹H NMR experiment, a hydrogen‐bonding/anion‐binding mechanism was proposed wherein the nucleophilic ring‐opening operation, and oxo‐ and carbamate‐anions stabilization occur cooperatively towards isocyanate fixation.

Core‐shell nanocatalysts are particularly attractive due to their versatility and stability. Here, we describe cobalt nanoparticles encapsulated within graphitic shells prepared via the pyrolysis of a cationic polymer ionic liquid (PIL) with a cobalt(II) chloride anion. The resulting material has a core‐shell structure that displays excellent activity and selectivity in the self‐dehydrogenation and hetero‐dehydrogenation of primary amines to their corresponding imines. Furthermore, the catalyst exhibits excellent activity in the synthesis of secondary imines from substrates with various reducible functional groups (C=C, C≡C and C≡N) and amino acid derivatives.

No beating about the bush: (Hetero)aromatic amines underwent decarboxylative N‐alkylation directly with carboxylic acids with a dual copper/acridine photocatalytic system. The directional character of the acridine photocatalysis facilitates the challenging decarboxylation of unactivated carboxylic acids in the presence of more readily oxidizable anilines, thus enabling the use of a wide range of structurally diverse amine and acid substrates (see scheme).

Abstract

The development of efficient and selective C−N bond‐forming reactions from abundant feedstock chemicals remains a central theme in organic chemistry owing to the key roles of amines in synthesis, drug discovery, and materials science. Herein, we present a dual catalytic system for the N‐alkylation of diverse aromatic carbocyclic and heterocyclic amines directly with carboxylic acids, by‐passing their preactivation as redox‐active esters. The reaction, which is enabled by visible‐light‐driven, acridine‐catalyzed decarboxylation, provides access to N‐alkylated secondary and tertiary anilines and N‐heterocycles. Additional examples, including double alkylation, the installation of metabolically robust deuterated methyl groups, and tandem ring formation, further demonstrate the potential of the direct decarboxylative alkylation (DDA) reaction.

Heterocycle cross‐couplings by sulfur: Addition of heteroaryl nucleophiles onto a simple, readily accessible alkyl sulfinyl(IV) chloride allows formation of a trigonal bipyramidal sulfurane intermediate. Reductive elimination provides bis‐heteroaryl products in a practical and efficient fashion.

Abstract

Despite the tremendous utilities of metal‐mediated cross‐couplings in modern organic chemistry, coupling reactions involving nitrogenous heteroarenes remain a challenging undertaking – coordination of Lewis basic atoms into metal centers often necessitate elevated temperature, high catalyst loading, etc. Herein, we report a sulfur (IV) mediated cross‐coupling amendable for the efficient synthesis of heteroaromatic substrates. Addition of heteroaryl nucleophiles to a simple, readily‐accessible alkyl sulfinyl (IV) chloride allows formation of a trigonal bipyramidal sulfurane intermediate. Reductive elimination therefrom provides bis‐heteroaryl products in a practical and efficient fashion.

Bulk=Hulk : Superbulky alkaline earth metal amide complexes were found to be extremely active catalysts for alkene hydrogenation, clearly extending the substrate scope. Even various arenes, including benzene, can be reduced under relatively mild conditions.

Abstract

Two series of bulky alkaline earth (Ae) metal amide complexes have been prepared: Ae[N(TRIP)₂]₂ (1 ‐Ae) and Ae[N(TRIP)(DIPP)]₂ (2 ‐Ae) (Ae=Mg, Ca, Sr, Ba; TRIP=Sii Pr₃, DIPP=2,6‐diisopropylphenyl). While monomeric 1 ‐Ca was already known, the new complexes have been structurally characterized. Monomers 1 ‐Ae are highly linear while the monomers 2 ‐Ae are slightly bent. The bulkier amide complexes 1 ‐Ae are by far the most active catalysts in alkene hydrogenation with activities increasing from Mg to Ba. Catalyst 1 ‐Ba can reduce internal alkenes like cyclohexene or 3‐hexene and highly challenging substrates like 1‐Me‐cyclohexene or tetraphenylethylene. It is also active in arene hydrogenation reducing anthracene and naphthalene (even when substituted with an alkyl) as well as biphenyl. Benzene could be reduced to cyclohexane but full conversion was not reached. The first step in catalytic hydrogenation is formation of an (amide)AeH species, which can form larger aggregates. Increasing the bulk of the amide ligand decreases aggregate size but it is unclear what the true catalyst(s) is (are). DFT calculations suggest that amide bulk also has a noticeable influence on the thermodynamics for formation of the (amide)AeH species. Complex 1 ‐Ba is currently the most powerful Ae metal hydrogenation catalyst. Due to tremendously increased activities in comparison to those of previously reported catalysts, the substrate scope in hydrogenation catalysis could be extended to challenging multi‐substituted unactivated alkenes and even to arenes among which benzene.

Nature Catalysis, Published online: 10 February 2020; doi:10.1038/s41929-019-0420-6

Plasma will fix it: Plasma polymerization is used to immobilize a phosphonium salt organocatalyst (P_cat) in an amorphous hydrogenated carbon coating on unfunctionalized metal oxide supports. The resulting catalysts are employed in the synthesis of cyclic carbonates from epoxides and CO₂ in up to 99 % yield under mild conditions. Furthermore, the unprecedented recycling of a catalyst immobilized by a plasma technique is reported.

Abstract

The first plasma‐assisted immobilization of an organocatalyst, namely a bifunctional phosphonium salt in an amorphous hydrogenated carbon coating, is reported. This method makes the requirement for prefunctionalized supports redundant. The immobilized catalyst was characterized by solid‐state ¹³C and ³¹P NMR spectroscopy, SEM, and energy‐dispersive X‐ray spectroscopy. The immobilized catalyst (1 mol %) was employed in the synthesis of cyclic carbonates from epoxides and CO₂. Notably, the efficiency of the plasma‐treated catalyst on SiO₂ was higher than those of the SiO₂ support impregnated with the catalyst and even the homogeneous counterpart. After optimization of the reaction conditions, 13 terminal and four internal epoxides were converted with CO₂ to the respective cyclic carbonates in yields of up to 99 %. Furthermore, the possibility to recycle the immobilized catalyst was evaluated. Even though the catalyst could be reused, the yields gradually decreased from the third run. However, this is the first example of the recycling of a plasma‐immobilized catalyst, which opens new possibilities in the recovery and reuse of catalysts.