Room Temperature Reaction Research Articles

TBAT-Catalyzed Deoxygenative Reduction of Tertiary Amides to Amines.

A simple, mild, metal-free catalytic protocol is developed to convert amides to amines. This protocol uses a stable tetrabutylammonium difluorotriphenylsilicate in combination with silanes that generates a highly reactive hydrosilicate species, which enables the reduction of a broad range of amides to amines in moderate to good yields. The attractive features of this protocol include operational simplicity, safety, short reaction times, room temperature reaction, broad substrate scope, and amenable to scale up.

Synthesis and Structures of Ruthena‐octahydrotetraborane Complexes

AbstractThe reactivity of κ2‐N,S‐chelated ruthenium borate complexes, [Ru(PPh3)(κ2‐N,S‐(NC7H4S2)Ru{κ3‐H,S,S′‐H2B (NC7H4S2)2}] (1 a) and [Ru(PPh3)(κ2‐N,S‐(NC5H4S){κ3‐H,S,S′‐H2B(NC5H4S)2}] (1 b) with monoboranes have been explored. The prolonged room temperature reaction of [Ru(PPh3){κ2‐N,S‐(NC7H4S2)}{κ3‐H,S,S′‐H2B(NC7H4S2)2}], 1 a with an excess of [BH3 ⋅ THF] led to the formation of hydrogen‐rich complex, arachno‐[PPh3(κ2‐B3H8)Ru{κ3‐H,S,S′‐H2B(NC7H4S2)2] (2). In a similar fashion, the isomeric ruthenatetraborane complexes of [Ru(PPh3)(κ2‐N,S‐(B3H8){κ3‐H,S,S′‐H2B(NC5H4S)2}], 4 and 5 were isolated from the room temperature reaction of 1 b with [BH3 ⋅ THF]. In complex 2, the borate ligand, [H2B(NC5H4S)2] and the PPh3 occupy the endo and exo sites of the butterfly‐shaped RuB3 core, respectively. In contrast, the borate unit [H2B(NC5H4S)2] in 4 sits on the exo position of the butterfly core, while the phosphine ligand occupies the endo site. Multinuclear spectroscopic analyses were done to characterize all new complexes and the structures were further confirmed by single‐crystal X‐ray diffraction analysis. Density functional theory (DFT) calculations were performed to probe into the bonding modes of these complexes.

Humic acid-catalyzed efficient synthesis of α-aminonitriles in water using potassium hexacyanoferrate (II) as a cyanide source

A highly efficient, one-pot, three-component Strecker reaction for the synthesis of α-aminonitriles from carbonyl compounds, amines, and potassium hexacyanoferrate (II) (K4[Fe(CN)6]) in the presence of a catalytic amount of humic acid catalyst in water at room temperature has been developed. Advantages of this methodology are use of inexpensive, commercially available, environmentally friendly and reusable organocatalyst, environmentally benign and inexpensive cyanide source, simple experimental and work-up procedure, high yields, room temperature reaction, water as a green solvent and scaled-up synthesis.

Mechanochemical Organic Synthesis - Powerful Tool in Greener Chemistry

Organic chemical reactions are usually promoted by heating of reactants in various organic solvents. Amongst emerging synthetic methods mechanochemistry is recognized as being promissing in the reduction of the environmental impact by conducting chemical reactions in solid state. Energy required to promote transformation is obtained by mechanical force commonly by vibrational ball milling. Greener aspects of the mechanochemistry are in the reduction of solvent use, shorter reaction times, room temperature and better reactions yields in comparison to classical thermal solution conditions. This mini-review gives selected examples of eco-sustainable mechanochemical organic reactions.

Regioselective Derivatization of Silylated [20]Silafulleranes

Silafulleranes with endohedral Cl- ions are a unique, scarcely explored class of structurally well-defined silicon clusters and host-guest complexes. Herein, we report regioselective derivatization reactions on the siladodecahedrane [nBu4N][Cl@Si20(SiCl3)12Cl8] ([nBu4N][1]), which has its cluster surface decorated with 12 SiCl3 and 8 Cl substituents in perfect Th symmetry. The room-temperature reaction of [nBu4N][1] with excess iBu2AlH in ortho-difluorobenzene (oDFB) furnishes perhydrogenated [nBu4N][Cl@Si20(SiH3)12H8] ([nBu4N][2]) in 50% yield; the non-pyrophoric [2]- is the largest structurally authenticated (by X-ray diffraction) hydridosilane known to date. A simple switch from pure oDFB to an oDFB/Et2O solvent mixture suppresses core hydrogenation and results in the formation of [nBu4N][Cl@Si20(SiH3)12Cl8] ([nBu4N][3]). In addition to the exhaustive Cl/H exchange at all 44 Si-Cl bonds of [1]- and the regioselective 36-fold silyl group hydrogenation, we achieved the simultaneous introduction of Me substituents at all 8 SiCl vertices along with the conversion of all 12 SiCl3 to SiH3 groups by treating [nBu4N][1] with Me2AlH/Me3Al in oDFB ([nBu4N][Cl@Si20(SiH3)12Me8], [nBu4N][4]; 73%). Quantum-chemical free-energy calculations find an SN2-Si-type hydrogenation of the exohedral SiCl3 moieties in [1]- (trigonal-bipyramidal intermediate) slightly preferred over metathesis-like SNi-Si substitutions (four-membered transition state). Cage hydrogenation likely occurs via SNi-Si processes. The experimentally demonstrated influence of an Et2O co-solvent, which drastically increases the respective reaction barriers, is attributed to the increased stability of the resulting iBu2AlH-OEt2 adduct and its higher steric bulk compared to free iBu2AlH.

Ternary CuZnPd Nanoalloys Achieving the Synergy of an Electronic Interaction and Bifunctional Catalysis for Efficient Ethanol Electrooxidation

Rationally constructing nanoalloys achieving the synergy of multiple interactions among different constituents could substantially enhance the electrocatalytic performance of an active metal for a given chemical reaction. In this context, we design and synthesize well-controlled ternary CuZnPd alloy nanoparticles, in which the Cu atoms modify the electronic configuration of Pd atoms through the ligand effect or the lattice strain effect, while the Zn atoms clean their neighboring Pd sites through a bifunctional mechanism, and the synergy of these two benefits endows the ternary CuZnPd alloy nanoparticles with exceptional electrocatalysis for a room-temperature ethanol oxidation reaction (EOR). In specific, at an appropriate 1/1/1 molar ratio for Cu/Zn/Pd, the as-prepared ternary CuZnPd alloy nanoparticles exhibit both the highest specific activity and mass activity of 17.3 mA cm–2 and 11.8 A mg–1, respectively, which outperform those of their CuPd, ZnPd alloy counterparts and the commercial Pd/C catalyst, as well as the majority of recently reported Pd-based catalysts. Density functional theory calculations verify that the key CO* and CH3CHO* intermediates generated during the EOR have the lowest adsorption energy on the ternary CuZnPd alloy nanoparticles, which is responsible for their boosted EOR electrocatalysis.

Room-Temperature, Copper-Free, and Amine-Free Sonogashira Reaction in a Green Solvent: Synthesis of Tetraalkynylated Anthracenes and In Vitro Assessment of Their Cytotoxic Potentials.

The multifold Sonogashira coupling of a class of aryl halides with arylacetylene in the presence of an equivalent of Cs2CO3 has been accomplished using a combination of Pd(CH3CN)2Cl2 (0.5 mol %) and cataCXium A (1 mol %) under copper-free and amine-free conditions in a readily available green solvent at room temperature. The protocol was used to transform several aryl halides and alkynes to the corresponding coupled products in good to excellent yields. The rate-determining step is likely to involve the oxidative addition of Ar-X. The green protocol provides access to various valuable polycyclic aromatic hydrocarbons (PAHs) with exciting photophysical properties. Among them, six tetraalkynylated anthracenes have been tested for their anticancer properties on the human triple-negative breast cancer (TNBC) cell line MDA-MB-231 and human dermal fibroblasts (HDFs). The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed to find out the IC50 concentration and lethal dose. The compounds being intrinsically fluorescent, their cellular localization was checked by live cell fluorescence imaging. 4',6-Diamidino-2-phenylindole (DAPI) and propidium iodide (PI) staining was performed to check apoptosis and necrosis, respectively. All of these studies have shown that anthracene and its derivatives can induce cell death via DNA damage and apoptosis.

The role of single-boron of N-doped graphene for effective nitrogen reduction

Room-temperature electrocatalytic nitrogen reduction reaction (NRR) is of paramount significance for the fertilizer industry and fundamental catalysis science. However, many NRR catalysts were based on the use of metals. Herein, we focus on exploring boron-based, metal-free, efficient catalysts for NRR by density functional theory calculations with van der Waals corrections (DFT+D3). Our results show that the NRR performance of the boron active site can be improved by tuning the N-coordination environment in a graphene sheet, and the B-N-C structures show excellent stability. By considering the correlation between the Bader charges of the boron dopant over N-decorated graphene and their NRR activities, the rational design principle of a boron-based catalyst for NRR is developed. The boron-site with one pyridinic nitrogen in a double-vacancy structure is found to be a highly active center, with low reaction energy (0.53 eV) and kinetic barrier (0.84 eV) through the distal mechanism. We also found that the charge loss of boron considerably hampers hydrogen adsorption, which in turn promotes the NRR efficiency by hindering the competing hydrogen evolution. This work offers new insights into developing low-cost, highly effective boron-based materials as promising electrocatalysts for green ammonia synthesis.

Sustainable synthesis of SiS2 for solid-state electrolytes by cascaded metathesis

Sulfide-based electrolytes containing silicon offer high ionic conductivity and are employed in emerging solid-state batteries that are promising for electric vehicles due to their improved energy density and safety. However, their deployment is constrained by the high cost and low availability of the SiS2 precursor. Here we introduce a green, solution-based synthesis of SiS2 through coupled metathesis reactions. First, the key Li2S precursor is synthesized from the room-temperature reaction between abundant Na2S and LiCl in ethanol. Next, the Li2S is recovered from solution and combined with SiCl4 in ethyl acetate to form a SiS2 solution and regenerate LiCl. The synthesized Li2S and SiS2 are characterized and then combined to form a glassy solid electrolyte with a conductivity of 0.11 mS cm-1 at 30 °C, validating the utility of metathesis-derived metal sulfides to solid electrolyte synthesis. In this cascaded metathesis scheme the expensive components, LiCl and solvents, are recovered and recycled in a circular economy. The cascaded metathesis process can in principle be used to synthesize nearly any metal sulfide of interest to a wide range of applications including energy conversion/storage, catalysis, electronics, and optics.

Electrospray Mass Spectrometry to Study Combinatorial iClick Reactions and Multiplexed Kinetics of [Ru(N3)(N∧N)(terpy)]PF6 with Alkynes of Different Steric and Electronic Demand.

In a combinatorial approach, a family of ruthenium(II) azido complexes [Ru(N3)(N∧N)(terpy)]PF6 with terpy = 2,2':6',2″-terpyridine and N∧N as a bidentate chelator derived from 2,2'-biypridine and its 4,4'-disubstituted derivatives, 2,2'-bipyrimidine, and 1,10-phenanthroline were reacted with different internal and terminal alkynes to give access to a total of 7 × 7 = 49 triazolato complexes in a room-temperature catalyst-free iClick reaction. The reactants were mixed in a repurposed high-performance liquid chromatography (HPLC) autosampler, and the reaction progress was monitored by direct injection into an electrospray mass spectrometer. The ratio of the peak intensities of [Ru(N3)(N∧N)(terpy)]+ and [Ru(triazolato)(N∧N)(terpy)]+ was converted to a colored heat map for facile visual inspection of the conversion ratio. By automated multiple injections of the reaction mixture in fixed time intervals and plotting peak intensities over reaction time, pseudo-first-order rate constants were easily determined. Finally, nonoverlapping isotope patterns of the azido starting materials and triazolato products enabled multiplexed parallel determination of rate constants for four different ruthenium(II) azido complexes from a single sample vial, thereby reducing experiment time by 75%.

Chemistry of CS2 and CS3 Bridged Decaborane Analogues: Regular Coordination Versus Cluster Expansion.

In an effort to synthesize metallaheteroborane clusters of higher nuclearity, the reactivity of metallaheteroboranes, nido-[(Cp*M)2B6S2H4(CS3)] (Cp* = C5Me5) (1: M = Co; 2: M = Rh) with various metal carbonyls have been investigated. Photolysis of nido-1 and nido-2 with group 6 metal carbonyls, M'(CO)5.THF (M' = Mo or W) were performed that led to the formation of a series of adducts [(Cp*M)2B6S2H4(CS3){M'(CO)5}] (3: M = Co, M' = Mo; 4: M = Co, M' = W; 5: M = Rh, M' = Mo; 6: M = Rh, M' = W) instead of cluster expansion reactions. In these adducts, the S atom of C=S group of di(thioboralane)thione {B2CS3} moiety is coordinated to M'(CO)5 (M = Mo or W) in η1-fashion. On the other hand, thermolysis of nido-1 with Ru3(CO)12 yielded one fused metallaheteroborane cluster [{Ru(CO)3}3S{Ru(CO)}{Ru(CO)2}Co2B6SH4(CH2S2){Ru(CO)3}2S], 7. This 20-vertex-fused cluster is composed of two tetrahedral {Ru3S} and {Ru2B2}, a flat butterfly {Ru3S} and one octadecahedron {Co2RuB7S} core with one missing vertex, coordinated to {Ru2SCH2S2} through two boron and one ruthenium atom. On the other hand, the room temperature reaction of nido-2 with Co2(CO)8 produced one 19-vertex fused metallaheteroborane cluster [(Cp*Rh)2B6H4S4{Co(CO)}2{Co(CO)2}2(μ-CO)S{Co(CO)3}2], 8. Cluster 8 contains one nido-decaborane {Rh2B6S2}, one butterfly {Co2S2} and one bicapped square pyramidal {Co6S} unit that exhibits an intercluster fusion with two sulfur atoms in common. Clusters 3-6 have been characterized by multinuclear NMR and IR spectroscopy, mass spectrometry and structurally determined by XRD analyses. Furthermore, the DFT calculations have been carried out to gain insight into electronic, structural and bonding patterns of the synthesized clusters.

Silver-mediated Room Temperature Reactions for the Synthesis of N-α-Ketoacyl Sulfoximines and N-α,β-Unsaturated Acyl Sulfoximines.

Here, we report a silver-mediated coupling of acetylenes with sulfoximines to synthesize N-α-ketoacyl sulfoximines and N-α,β-unsaturated acyl sulfoximines. The reactions are performed under an open atmosphere using the oxidant K2S2O8 and the ligand 2,2-bipyridyl. However, the fate of the product formation is controlled by the type of substrate used. The coupling between aryl acetylenes and sulfoximines afforded the N-α-ketoacylsulfoximines, while the alkyl acetylenes provided the N-α,β-unsaturated acyl sulfoximines. Controlled experiments reveal the differential reactivity patterns of substrates. The labeling 18O experiments showed that water is the source of the incoming oxygen atom for the keto group of N-α-ketoacyl sulfoximines and N-α,β-unsaturated acyl sulfoximines.

Room Temperature Fluoranthene Synthesis through Cationic Rh(I)/H8-BINAP-Catalyzed [2 + 2 + 2] Cycloaddition: Unexpected Acceleration due to Noncovalent Interactions

The fluoranthene skeleton is a structure often found in natural products and fluorescent materials, and thus developing an operationally simple method for diversity-oriented fluoranthene synthesis is an important research topic in organic synthesis. However, existing synthetic methods require harsh reaction conditions or limited substrate applicability or both. Here, we report the room temperature synthesis of substituted fluoranthenes and azafluoranthenes through the cationic Rh(I)/H8-BINAP complex-catalyzed [2 + 2 + 2] cycloaddition using 1,8-dialkynylnaphthalenes. DFT calculations reveal that the H8-BINAP ligand stabilizes the intermediates, allowing the room temperature reaction. Among the substrates examined, 1,8-bis(phenylethynyl)naphthalene and diarylacetylenes show high reactivity, contrary to the reactivity predicted by their steric bulkiness. Theoretical and experimental mechanistic studies have demonstrated that the noncovalent interactions of the phenyl groups on both the substrates and the ligand accelerate the present sterically demanding reactions by stabilizing the transition states rather than inducing steric repulsions.

Atomic Fe/Zn anchored N, S co-doped nano-porous carbon for boosting oxygen reduction reaction

Dual-single-atom catalysts are well-known due to their excellent catalytic performance of oxygen reduction reaction (ORR) and the tunable coordination environment of the active sites. However, it is still challengable to finely modulate the electronic states of the metal atoms and facilely fabricate a catalyst with dual-single atoms homogeneously dispersed on conductive skeletons with good mass transport. Herein, atomic FeNx/ZnNx sites anchored N, S co-doped nano-porous carbon plates/nanotubes material (Fe0.10ZnNSC) is rationally prepared via a facile room-temperature reaction and high-temperature pyrolysis. The as-prepared Fe0.10ZnNSC catalyst exhibits a positive onset potential of 0.956 V, an impressive half-wave potential of 0.875 V, excellent long-term durability, and a high methanol resistance, outperforming the benchmark Pt/C. The outstanding ORR performance of Fe0.10ZnNSC is due to its unique nanoarchitecture: a large specific surface area (1092.8 cm2 g−1) and well-developed nanopore structure ensure the high accessibility of active sites; the high conductivity of the carbon matrix guarantees a strong ability to transport electrons to the active sites; and the optimized electronic states of FeNx and ZnNx sites possess good oxygen intermediate adsorption/desorption capacity. This strategy can be extended to design and fabricate other non-precious dual-single-atom ORR catalysts.

An Environmentally Friendly and Cost-Effective Route to LiNi0.5Mn1.5O4 Crystals: Structure, Morphology Evolution, and Electrochemical Properties

A green and economical process based on the room-temperature solid-state reactions is developed to synthesize LiNi0.5Mn1.5O4, and the effects of sintering temperature and lithium excess on the structure, morphology and performance are investigated in detail. The measurements reveal that the performance of the LiNi0.5Mn1.5O4 is highly dependent on the crystal morphology and integrity which are significantly influenced by the sintering temperature, and the results demonstrate that well-crystallized octahedral-like crystals with superior electrochemical performance can be readily synthesized by the new developed route at a moderate sintering temperature of 800 °C with a small lithium excess of 3%.

Hierarchical BiOCl flowerlike microspheres via a room-temperature solid-state chemical reaction as a new anode for rechargeable magnesium-ion batteries.

Rechargeable magnesium-ion batteries (MIBs) have received much attention in recent years, but their development remains limited due to a lack of anode materials with high capacity and fast diffusion kinetics. Herein, for the first time, hierarchical BiOX (X = Cl, Br, I) flowerlike microspheres composed of interleaved nanosheets are constructed via a simple room-temperature solid-state chemical reaction as the anode for MIBs. Among them, BiOCl flowerlike microspheres deliver good cycling stability (110 mA h g-1 after 100 cycles) and a superior rate capacity (134 mA h g-1 at 500 mA g-1). This is attributed to their unique flowerlike microsphere structure that not only accommodates a volume change to maintain their structural integrity but also shortens the ion-transport path to improve the diffusion rate. Importantly, ex situ tests were carried out to clarify the phase and structure evolution of the BiOCl flowerlike microspheres during cycling. The results show that BiOCl is first transformed to Bi and then alloyed to Mg3Bi2 in the discharging process, and Mg3Bi2 is turned back to Bi in the charging process. Besides, the initial microsphere structure is essentially maintained during the discharging/charging process, indicating the better stability of the structure. The current study demonstrates that the structural design of flowerlike microspheres is an effective strategy to develop promising anode materials for MIBs.

A hollow NaBiF4:Tb nanoscintillator with ultra-weak afterglow for high-resolution X-ray imaging.

Compared with commercial bulk scintillators and halide perovskites, lanthanide-doped fluoride nanoscintillators (NSs) exhibit high photochemical stability, low bio-toxicity and tunable emissions. However, the widely employed hosts, such as NaGdF4, NaLuF4 and NaYF4, need many expensive rare earth salts and time-consuming reaction processes. In this work, lanthanide-doped NaBiF4 NSs were prepared by a facile rapid room-temperature reaction method. The obtained NSs present a hollow structure, strong scintillation intensity and ultra-weak afterglow. The scintillation intensity was enhanced by incorporating Gd3+ ions, but it was decreased after codoping with Ho3+ or Er3+ ions. By employing a NaBiF4:15Tb/10Gd NS integrated thin film as a nanoscintillator screen, a high spatial resolution of 12.5 lp mm-1 was achieved. Our results could promote the exploration of new kinds of NSs with low cost, high production and superior performances.

Stereodivergent Assembly of 2,6-cis- and -trans-Tetrahydropyrans via Base-Mediated Oxa-Michael Cyclization: The Key Role of the TMEDA Additive.

The stereodivergent synthesis of cis- and trans-2,6-disubstituted tetrahydropyrans (THPs) via sodium hexamethyldisilazide-promoted oxa-Michael cyclization of (E)-ζ-hydroxy α,β-unsaturated esters is presented. The cyclization affords the kinetically favored trans-THPs with high stereoselectivity (dr up to 93:7) at a low temperature (-78 °C), while the room-temperature reaction does not produce the thermodynamically preferred cis-THPs as major products and occurs with poor stereocontrol. The addition of tetramethylethylenediamine (TMEDA) significantly improves the stereochemical outcome of the room-temperature cyclization and allows attaining high cis-selectivity (dr up to 99:1). The remarkable effect of TMEDA indicates that the sodium cation plays an important role in controlling the stereoselectivity of the thermodynamically driven process, that is, complexation of the cation with the cyclization products results in diminished selectivity. DFT calculations support this conclusion, indicating a greater difference in Gibbs energies of sodium-free cis- and trans-enolates compared to the respective sodium chelate complexes. The synthetic utility of the method has been demonstrated by the formal syntheses of (+)-Neopeltolide and (-)-Diospongin B and the total synthesis of (-)-Diospongin A.

Potassiumtert‐Butoxide‐Mediated Synthesis of 2‐Aminoquinolines from Alkylnitriles and 2‐Aminobenzaldehyde Derivatives

AbstractKOtBu mediates the reaction between 2‐amino arylcarbaldehydes and benzyl/alkyl cyanides toward the expeditious formation of 2‐aminoquinolines under transition‐metal‐free conditions. The described transformation proceeds throughin‐situgenerated enimine intermediate from benzyl/alkyl cyanides under KOtBu‐mediated reaction conditions. The substituted 2‐aminoquinolines were realized in excellent yields at room temperature and shorter reaction time. The designed process exhibits operational simplicity and broad functional group tolerance in delivering the products of high significance.

Mild and Rapid Light-Driven Suzuki-Miyaura Reactions Catalyzed by AuPd Nanoparticles in Water at Room Temperature.

Organic reactions carried out in water under mild conditions are state-of-the-art in terms of environmentally benign chemical processes. In this direction, plasmonic catalysis can aid in accomplishing such tasks. In the present work, cyclodextrin-mediated AuPd bimetallic nanoparticles (NPs) were applied in room-temperature aqueous Suzuki-Miyaura reactions aiming at preparing biaryl products based on fluorene, isatin, benzimidazole and resorcinol, with yields of 77 % up to 95 %. AuPd NPs were revealed to be a physical mixture of Au and Pd particles circa 20 and 2 nm, respectively, through X-ray diffraction, dynamic light scattering, UV-Vis spectroscopy and transmission electron microscopy analyses.