Cu(II)/Photoredox-Catalyzed Aminoacylation of Vinyl Bromides

A novel C-C coupling reaction of vinyl bromides with carboxamides has been developed through Cu(OAc)2/photocatalysis. This process features regioselective carboxamido carbon-vinylation under mild reaction conditions. Mechanistic studies suggest that the formation of an acyl-Cu(I) intermediate plays a crucial role with regard to enabling this transformation.

Construction of Dual Active-Site NH2-MIL-125(Ti) for Efficient Selective Oxidation of Cyclohexylamine to Cyclohexanone Oxime

In this work, dual active-site Ti-incorporated metal-organic frameworks (MIL-125 and NH2-MIL-125) were synthesized by a simple solvothermal process and applied to prepare cyclohexanone oxime from cyclohexylamine oxidation. A low-temperature thermal calcination strategy was used for the modulation of surface properties while maintaining the crystal structure and morphology. The results demonstrated that novel bifunctional NH2-MIL-125@250 °C obtained from thermal calcination possessed a large surface area with both oxygen vacancies and surface hydroxyl-active sites, promoting the adsorption and activation of cyclohexylamine and oxygen molecules, respectively. Under the optimum conditions, the cyclohexylamine conversion was 44.3%, and the selectivity to cyclohexanone oxime was 83.0%. By comparison, the stability of MIL-125 and NH2-MIL-125 was investigated separately in cyclic tests, and the crystal structure and catalytic properties of NH2-MIL-125 have been shown to be more stable than those of MIL-125. Combined with density functional theory, it was further shown that NH2-MIL-125 displayed a higher adsorption and activation ability toward cyclohexylamine and oxygen than MIL-125 and had a more stable metal-organic ligand structure. Finally, a plausible reaction pathway for selective cyclohexylamine oxidation to cyclohexanone oxime was proposed. This work can give new insights into designing novel dual active-site catalysts for the efficient catalytic transformation of organic primary amines to corresponding oximes.

Aryl Borane as a Catalyst for Dehydrative Amide Synthesis

Tris(pentafluorophenyl)borane B(C6F5)3·H2O is reported as a catalyst for dehydrative amidation of carboxylic acids and amines. This protocol is applicable across a wide range of >35 substrates, including aromatic and aliphatic amines and acids, resulting in amides in ≤92% yields. The scalability of the reaction up to 10 mmol, along with the synthesis of drugs such as ibuprofen amide, moclobemide, and phenacetin, demonstrates the industrial potential of our protocol.

Female-age-dependent changes in the lipid fingerprint of the mammalian oocytes

STUDY QUESTION

Can oocyte functionality be assessed by observing changes in their intracytoplasmic lipid droplets (LDs) profiles?

SUMMARY ANSWER

Lipid profile changes can reliably be detected in human oocytes; lipid changes are linked with maternal age and impaired developmental competence in a mouse model.

WHAT IS KNOWN ALREADY

In all cellular components, lipid damage is the earliest manifestation of oxidative stress (OS), which leads to a cascade of negative consequences for organelles and DNA. Lipid damage is marked by the accumulation of LDs. We hypothesized that impaired oocyte functionality resulting from aging and associated OS could be assessed by changes in LDs profile, hereafter called lipid fingerprint (LF).

STUDY DESIGN, SIZE, DURATION

To investigate if it is possible to detect differences in oocyte LF, we subjected human GV-stage oocytes to spectroscopic examinations. For this, a total of 48 oocytes derived from 26 young healthy women (under 33 years of age) with no history of infertility, enrolled in an oocyte donation program, were analyzed. Furthermore, 30 GV human oocytes from 12 women were analyzed by transmission electron microscopy (TEM). To evaluate the effect of oocytes' lipid profile changes on embryo development, a total of 52 C57BL/6 wild-type mice and 125 Gnpat+/- mice were also used.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Human oocytes were assessed by label-free cell imaging via coherent anti-Stokes Raman spectroscopy (CARS). Further confirmation of LF changes was conducted using spontaneous Raman followed by Fourier transform infrared (FTIR) spectroscopies and TEM. Additionally, to evaluate whether LF changes are associated with developmental competence, mouse oocytes and blastocysts were evaluated using TEM and the lipid dyes BODIPY and Nile Red. Mouse embryonic exosomes were evaluated using flow cytometry, FTIR and FT-Raman spectroscopies.

MAIN RESULTS AND THE ROLE OF CHANCE

Here we demonstrated progressive changes in the LF of oocytes associated with the woman's age consisting of increased LDs size, area, and number. LF variations in oocytes were detectable also within individual donors. This finding makes LF assessment a promising tool to grade oocytes of the same patient, based on their quality. We next demonstrated age-associated changes in oocytes reflected by lipid peroxidation and composition changes; the accumulation of carotenoids; and alterations of structural properties of lipid bilayers. Finally, using a mouse model, we showed that LF changes in oocytes are negatively associated with the secretion of embryonic exosomes prior to implantation. Deficient exosome secretion disrupts communication between the embryo and the uterus and thus may explain recurrent implantation failures in advanced-age patients.

LIMITATIONS, REASONS FOR CAUTION

Due to differences in lipid content between different species' oocytes, the developmental impact of lipid oxidation and consequent LF changes may differ across mammalian oocytes.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings open the possibility to develop an innovative tool for oocyte assessment and highlight likely functional connections between oocyte LDs and embryonic exosome secretion. By recognizing the role of oocyte LF in shaping the embryo's ability to implant, our original work points to future directions of research relevant to developmental biology and reproductive medicine.

STUDY FUNDING/COMPETING INTEREST(S)

This research was funded by National Science Centre of Poland, Grants: 2021/41/B/NZ3/03507 and 2019/35/B/NZ4/03547 (to G.E.P.); 2022/44/C/NZ4/00076 (to M.F.H.) and 2019/35/N/NZ3/03213 (to Ł.G.). M.F.H. is a National Agency for Academic Exchange (NAWA) fellow (GA ULM/2019/1/00097/U/00001). K.F. is a Diamond Grant fellow (Ministry of Education and Science GA 0175/DIA/2019/28). The open-access publication of this article was funded by the Priority Research Area BioS under the program "Excellence Initiative - Research University" at the Jagiellonian University in Krakow. The authors declare no competing interest.

TRIAL REGISTRATION NUMBER

N/A.

Copper-Nitroxyl-Catalyzed α-Oxygenation of Cyclic Secondary Amines Including Application to Late-Stage Functionalization

Cyclic secondary amines are prominent subunits in pharmaceutical compounds. Methods for direct functionalization of N-unprotected/unsubstituted piperidines and related heterocycles have limited precedent despite their potential to impact medicinal chemistry and organic synthesis. Herein, we report a Cu/nitroxyl co-catalyzed method for direct conversion of cyclic secondary amines to the corresponding lactams via aerobic dehydrogenation and oxidative coupling with water. The mild reaction conditions tolerate diverse functional groups, enabling application to molecules that cover broad chemical space. The method is showcased in selective functionalization of building blocks and complex molecules, including late-stage functionalization of bromodomain inhibitors.

The untold story of starch as a catalyst for organic reactions

Starch is one of the members of the polysaccharide family. This biopolymer has shown many potential applications in different fields such as catalytic reactions, water treatment, packaging, and food industries. In recent years, using starch as a catalyst has attracted much attention. From a catalytic point of view, starch can be used in organic chemistry reactions as a catalyst or catalyst support. Reports show that as a catalyst, simple starch can promote many heterocyclic compound reactions. On the other hand, functionalized starch is not only capable of advancing the synthesis of heterocycles but also is a good candidate catalyst for other reactions including oxidation and coupling reactions. This review tries to provide a fair survey of published organic reactions which include using starch as a catalyst or a part of the main catalyst. Therefore, the other types of starch applications are not the subject of this review.

Introducing N-Sulfinylamines into Visible-Light-Induced Carbene Chemistry for the Synthesis of Diverse Amides and α-Iminoesters

A rare example of visible-light-mediated diverse reactivity of N-sulfinylamines with different types of carbene precursors has been disclosed. Acylsilanes and aryldiazoacetates have been utilized as nucleophilic and electrophilic carbene precursors into the N═S═O linchpin, to achieve valuable amides and α-iminoesters, respectively. Interestingly, diazocarbonyls can also participate in the amidation reaction with N-sulfinylamines via in situ generated ketenes. This operationally simple modular method offers a mild, transition-metal-free, and coupling-reagent-free protocol to fabricate structurally diverse amides and a promptly accessible technique to achieve α-iminoesters, where visible light remains as a key promoter.

Dual Role of TiO(acac)2 as a Reagent and an Activator/Catalyst: A Study on the Solvent Dependent Product Formation

The dual operation of a chemical species in synthetic chemistry is an intriguing and relatively unexplored phenomenon. The application of such a species is expected to reduce the use of multiple reaction partners and catalysts/activators. Herein, we report a simple and easy-to-use protocol for the twin application of TiO(acac)2 , as a reagent and an activator to synthesize β-enamino ketones with amines in acetonitrile. The same early transition metal precursor when employed in N,N-dimethylformamide with the amines, resulted in the formation of the substituted amides. Both reactions were explored with various substrates to check the viability of the present protocol. Moreover, experimental studies were conducted to understand the mechanism of both reactions.

A facile synthesis of phthalimides from o-phthalaldehyde and amines via tandem cyclocondensation and α-C-H oxidation by an electrochemical oxygen reduction reaction

Electrochemical synthesis of phthalimides from o-phthalaldehyde and amines via tandem cyclocondensation and α-C-H oxygenation of isoindolinone was achieved. The α-C-H oxidation proceeded with molecular oxygen via an oxygen reduction reaction (ORR) on the cathode under electrochemical conditions. The synthetic utility of this protocol was successfully demonstrated by employing gram-scale synthesis and obtaining bioactive molecules such as thalidomide and 2-(2,6-diisopropylphenyl)-5-hydroxyisoindoline-1,3-dione. Mechanistic studies and control experiments indicate that molecular oxygen provides oxygen atoms for the reaction.

Photoinduced Nitroarenes as Versatile Anaerobic Oxidants for Accessing Carbonyl and Imine Derivatives

Herein, we report a protocol for the anaerobic oxidation of alcohols, amines, aldehydes, and imines promoted by photoexcited nitroarenes. Mechanistic studies support the idea that photoexcited nitroarenes undergo double hydrogen atom transfer (HAT) steps with alcohols and amines to provide the respective ketone and imine products. In the presence of aldehydes and imines, successive HAT and oxygen atom transfer (OAT) events occur to yield carboxylic acids and amides, respectively. This transformation is amenable to a continuous-photoflow setup, which led to reduced reaction times.

Transannular Functionalization of Multiple C(sp3)-H Bonds of Tropane via an Alkene-Bridged Palladium(I) Dimer

This communication describes the Pd-catalyzed C(sp3)-H functionalization of a tropane derivative to generate products with functionalization at two (β/γ) or three (β/γ/β) different sites on the alicyclic amine core. These reactions proceed via an initial dehydrogenation to generate an alkene product that can react further to form a Pd(I) alkene-bridged dimer. Functionalization of this dimer affords β/γ/β-functionalized allylic arylation and allylic acetoxylation products.

Ru(II)-catalyzed oxidative coupling of sulfoxonium ylides with amines: efficient synthesis of α-ketoamides and indolo[2,1-a]isoquinolines

The first use of sulfoxonium ylides for the synthesis of α-ketoamides is described via a Ru(II)-catalyzed amidation reaction with amines. The same Ru(II)-catalyzed reaction of sulfoxonium ylides with 2-phenylindoles provided indolo[2,1-a]isoquinolines instead of α-ketoamides.

Cyclotrimetaphosphate-assisted ruthenium catalyst for the hydration of nitriles and oxidation of primary amines to amides under aerobic conditions in water

Amide bonds are ubiquitous and regarded as an essential constituent of many biologically active drug molecules and fine chemicals. We report a practical and operationally simple ruthenium-based catalytic system for the hydration of nitriles and aerobic oxidation of primary amines to the corresponding amides. Both reactions proceed without any external oxidant in water under aerobic conditions and exhibit a broad substrate scope. The mechanistic investigation was executed with the aid of control experiments and kinetic and spectroscopic studies of the reaction mixture.

Indication of Pd–C or Cu–C Intermediates in Bimetallic Nanoclusters During Pd/Au-PVP- or Cu/Au-PVP-Catalyzed Oxidations of endo-4-Oxatricyclo[5.2.1.02,6]-8-decene and Tetrahydro-γ-carbolines

Catalytic oxidation of tricyclic endo-norbornene-fused tetrahydrofuran with the bimetallic nanocluster Cu/Au-PVP in the presence of H2O2 or t-BuOOH as the oxidant leads to C–H bond oxidation adjacent to the ether function to give 4-oxa-tricyclo[5.2.1.0]-8,9-exo-epoxydecane, however, oxidation with Pd/Au-PVP takes place at the C=C double bond to give the same epoxide and the oxidative three-bond forming dimeric product, dodecahydro-1,4:6,9-dimethanodibenzofurano[2,3-b:7,8-b′]bisoxolane. Formation of the latter product suggests the involvement of a reactive Pd–C intermediate. Similarly, oxidative C–C bond-forming reactions are observed in cycloaddition reactions of N2-Boc-1,2,3,4-tetrahydro-γ-carbolines and 2,3-dihydroxybenzoic acid with Cu/Au-PVP (2–5 mol%) and H2O2 at 25 °C, providing two-bond-forming [4+2] cycloadducts. Under similar reaction conditions, Pd/Au-PVP did not produce the corresponding cycloadduct, indicating a need for complexation between Cu and the carboxylic acid group of 2,3-dihydroxybenzoic acid and the allylic amine function of the γ-carbolines during the cyclization reaction. The reported intermolecular coupling reactions using Pd/Au-PVP or Cu/Au-PVP nanocluster catalysts under oxidative conditions at 25 °C are unprecedented.

Transamidation of aromatic amines with formamides using cyclic dihydrogen tetrametaphosphate

Amide fragments are found to be one of the key constituents in a wide range of natural products and pharmacologically active compounds. Herein, we report a simple and efficient procedure for transamidation with a cyclic dihydrogen tetrametaphosphate. The protocol is simple, does not require any additives, and encompasses a broad substrate scope. To comprehend the mechanism of the present methodology, detailed spectroscopic and kinetic studies were undertaken.

Metal-free photoredox-catalyzed direct α-oxygenation of N,N-dibenzylanilines to imides under visible light

An efficient synthesis of imides using metal-free photoredox-catalyzed direct α-oxygenation of N,N'-disubstituted anilines in the presence of 9-mesityl-10-methylacridinium [Acr+-Mes]BF4 as a photoredox catalyst and molecular oxygen as a green oxidant under visible light was developed. This photochemical approach offered operational simplicity, high atom economy with a low E-factor, and functional group tolerance under mild reaction conditions. Control and quenching experiments confirmed the occurrence of a radical pathway and superoxide radical anion α-oxygenation reactions, and also provided strong evidence for the reductive quenching of [Acr+-Mes]BF4 based on a Stern-Volmer plot, which led to the proposed mechanism of this reaction.

Catalytic Deoxygenative Cyclopropanation of 1,2-Dicarbonyl or Monocarbonyl Compounds via Molybdenum Catalysis

The cyclopropanation of alkenes through the transition-metal-catalyzed decomposition of diazo compounds is a powerful and straightforward strategy to produce cyclopropanes. Nevertheless, the appeal of further application of this strategy is tempered by the potentially explosive nature of the diazo substrates. Therefore, it is highly desirable to develop sustainable and operationally safe surrogates for diazo compounds. In this Synpacts article, we discuss recent advances on the cyclopropane syntheses through the catalytic cyclopropanation of alkenes and metal carbenes generated in situ from nondiazo precursors as well as highlight our recent progress on the unprecedented molybdenum-catalyzed deoxygenative cyclopropanation reaction of 1,2-dicarbonyl or monocarbonyl compounds.

Photocatalyzed Dehydroxylative Amination of Phenols: A Ring-Expansion Approach for Medium-Sized Benzolactams

An efficient photopromoted dehydroxylative ring-expansion approach to eight-membered benzolactams that employ phthalocyanine iron(II) as the photosensitizer has been developed. This cascade reaction protocol, featuring a visible-light-promoted dehydroxylative amination and oxidative ring-expansion lactamization of 4-hydroxyphenols with N-alkyl-4-piperidinones, provides a green and reliable approach to a diverse array of valuable eight-membered benzolactams with high chemo- and regioselectivity.

A unique amphiphilic triblock copolymer, nontoxic to human blood and potential supramolecular drug delivery system for dexamethasone

The drug delivery system (DDS) often causes toxicity, triggering undesired cellular injuries. Thus, developing supramolecules used as DDS with tunable self-assembly and nontoxic behavior is highly desired. To address this, we aimed to develop a tunable amphiphilic ABA-type triblock copolymer that is nontoxic to human blood cells but also capable of self-assembling, binding and releasing the clinically used drug dexamethasone. We synthesized an ABA-type amphiphilic triblock copolymer (P2L) by incorporating tetra(aniline) TANI as a hydrophobic and redox active segment along with monomethoxy end-capped polyethylene glycol (mPEG2k; Mw = 2000 g mol-1) as biocompatible, flexible and hydrophilic part. Cell cytotoxicity was measured in whole human blood in vitro and lung cancer cells. Polymer-drug interactions were investigated by UV-Vis spectroscopy and computational analysis. Our synthesized copolymer P2L exhibited tuned self-assembly behavior with and without external stimuli and showed no toxicity in human blood samples. Computational analysis showed that P2L can encapsulate the clinically used drug dexamethasone and that drug uptake or release can also be triggered under oxidation or low pH conditions. In conclusion, copolymer P2L is nontoxic to human blood cells with the potential to carry and release anticancer/anti-inflammatory drug dexamethasone. These findings may open up further investigations into implantable drug delivery systems/devices with precise drug administration and controlled release at specific locations.

UV-Light-Induced N-Acylation of Amines with α-Diketones

Herein, we develop a mild method for N-acylation of primary and secondary amines with α-diketones induced by ultraviolet (UV) light. Forty-six examples with various functional groups are explored at room temperature with irradiation by three 26 W UV lamps (350-380 nm). The yield reaches 97%. The gram scale experiment product yield is 76%. Moreover, this system can be applied to the synthesis of several amino acid derivatives. Mechanistic studies show that benzoin is generated in situ from benzil under UV irradiation.

Molybdenum-Catalyzed Deoxygenative Cyclopropanation of 1,2-Dicarbonyl or Monocarbonyl Compounds

The transition-metal-catalyzed cyclopropanation of alkenes by the decomposition of diazo compounds is a powerful and straightforward strategy to produce cyclopropanes, but is tempered by the potentially explosive nature of diazo substrates. Herein we report the Mo-catalyzed regiospecific deoxygenative cyclopropanation of readily available and bench-stable 1,2-dicarbonyl compounds, in which one of the two carbonyl groups acts as a carbene equivalent upon deoxygenation and engages in the subsequent cyclopropanation process. The use of a commercially available Mo catalyst afforded an array of valuable cyclopropanes with exclusive regioselectivity in up to 90 % yield. The synthetic utility of this method was further demonstrated by gram-scale syntheses, late-stage functionalization, and the cyclopropanation of a simple monocarbonyl compound. Preliminary mechanistic studies suggest that phosphine (or silane) acts as both a mild reductant and a good oxygen acceptor that efficiently regenerates the catalytically active Mo catalyst through reduction of the Mo-oxo complexes.

Hydration of Aliphatic Nitriles Catalyzed by an Osmium Polyhydride: Evidence for an Alternative Mechanism

The hexahydride OsH₆(PⁱPr₃)₂ competently catalyzes the hydration of aliphatic nitriles to amides. The main metal species under the catalytic conditions are the trihydride osmium(IV) amidate derivatives OsH₃{κ²-N,O-[HNC(O)R]}(PⁱPr₃)₂, which have been isolated and fully characterized for R = ⁱPr and ^tBu. The rate of hydration is proportional to the concentrations of the catalyst precursor, nitrile, and water. When these experimental findings and density functional theory calculations are combined, the mechanism of catalysis has been established. Complexes OsH₃{κ²-N,O-[HNC(O)R]}(PⁱPr₃)₂ dissociate the carbonyl group of the chelate to afford κ¹-N-amidate derivatives, which coordinate the nitrile. The subsequent attack of an external water molecule to both the C(sp) atom of the nitrile and the N atom of the amidate affords the amide and regenerates the κ¹-N-amidate catalysts. The attack is concerted and takes place through a cyclic six-membered transition state, which involves C_nitrile···O–H···N_amidate interactions. Before the attack, the free carbonyl group of the κ¹-N-amidate ligand fixes the water molecule in the vicinity of the C(sp) atom of the nitrile.

The hexahydride complex OsH₆(PⁱPr₃)₂ competently catalyzes the hydration of aliphatic nitriles to amides. Isolation of the main metal species under the catalytic conditions, kinetics of hydration, and density functional theory calculations support an alternative mechanism to those previously reported.

N–C bond formation between two anilines coordinated to a ruthenium center in cis-form affording a 3,5-cyclohexadiene-1,2-diimine moiety

Four-electron oxidation of two anilines coordinated to a ruthenium(ii) center in a cis-form affords N1-phenylcyclohexa-3,5-diene-1,2-diimine through an N–C bond formation with N–H and C–H bond activation.

Aerobic oxidation of primary amines to amides catalyzed by an annulated mesoionic carbene (MIC) stabilized Ru complex

A Ru complex, stabilized by an annulated mesoionic carbene ligand, catalyzes the aerobic oxidation of a host of primary amines to amides in high yields and excellent selectivity. Kinetics, Hammett and DFT studies provide mechanistic insight.

N-Heterocyclic carbene (NHC) catalyzed amidation of aldehydes with amines via the tandem N-hydroxysuccinimide ester formation

A novel methodology for the construction of a wide variety of mono and di-substituted amides is developed, that utilizes readily available, non-hazardous, and cheaper starting reagents and simple imidazolium-based N-heterocyclic carbenes.

Aerobic oxidation of primary benzylic amines to amides and nitriles catalyzed by ruthenium carbonyl clusters carrying N,O-bidentate ligands

Four trinuclear ruthenium carbonyl clusters, (6-BrPyCHRO)₂Ru₃(CO)₈ (R = 4-OCH₃C₆H₄, 1a; R = 4-BrC₆H₄, 1b) and (2-OC₆H₄-HC[double bond, length as m-dash]N-C₆H₄R)₂Ru₃(CO)₈ (R = 4-OCH₃, 2a; R = 4-Br, 2b), were synthesized from the reactions of Ru₃(CO)₁₂ with the corresponding N,O-bidentate ligands (two pyridyl alcohols and two Schiff bases) respectively in a ratio of 1 : 2. Three new complexes 1b, 2a and 2b have been fully characterized by elemental analysis, FT-IR, NMR and X-ray crystallography. The catalytic activity of these ruthenium complexes for the aerobic oxidation of primary benzylic amines to amides and nitriles in the presence of t-BuOK was investigated, of which the Schiff base complex 2a was found to exhibit the highest activity.