Photochemical reductive deamination of alpha-amino aryl alkyl ketones

Photochemical reductive deamination of alpha-amino aryl alkyl ketones under photosensitizer-free conditions is presented. This protocol features high efficiency and selectivity. A plausible reaction pathway is proposed based on ultraviolet-visible absorption investigation, control experiments and deuterium-labelling studies. Mechanistic study reveals that the alpha-hydrogen atom of the ketone product originated from water.

Asymmetric Formal [3+2] Cycloaddition Reactions of 3-Isothiocyanato Oxindoles: An Update

3-Isothiocyanato oxindoles are a class of important building blocks which have been widely used in the synthesis of structurally diverse enantio-enriched spirooxindoles. In this short review, it is attempted to cover the recent synthetic aspects of 3-isothiocyanato oxindoles participated cascade cyclizations in the last few years (i.e., from 2017 to 2022), with an emphasis on formal [3+2] cycloaddition reactions.

[Equol and its enantiomers inhibited urethane-induced lung cancer in mice]

OBJECTIVE

To investigate the effects and mechanisms of equol and its enantiomers on urethane-induced lung cancer in mice.

METHODS

A total of 120 5-week-old male C57BL/6 mice were randomly divided into 8 groups: lung cancer tumor control group (CG), genistein control group (GCG), low dose racemic equol group (LEG), high dose racemic equol group (HEG), low dose R-equol group (LRE), high dose R-equol group (HRE), low dose S-equol group (LSE) and high dose S-equol group (HSE). Urethane was injected subcutaneously twice a week for 4 weeks to induce lung cancer and then the mice were fed for 4 months. The body weight and food intake of each group were measured and recorded weekly. After the mice were sacrificed, the blood, livers and lungs of the mice were collected. The incidence of lung cancer in each group was recorded. The concentration of serum superoxide dismutase (SOD), malondialdehyde (MDA) and 8-hydroxydeoxygunosine (8-OHdG) were detected by the corresponding kits. Western blotting was used to detect the expression of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) in the livers. Between-group differences in body weight and food intake of the mice were compared using repeated measures ANOVA, and ANOVA for the differences between non-repeated measurements, with post hoc analysis using Tukey's method if there were between-group differences. Comparisons of categorical data were performed by chi-square test, and if there were differences between the groups, the Bonferroni method was used for pairwise comparison.

RESULTS

A total of 49 in the 120 mice developed lung cancer. The overall incidence of lung cancer was 40.8%. Compared with the control group, the incidence of lung cancers in each experimental group was lower, and the difference was statistically significant. The incidence of lung cancer in the high-dose experimental group was significantly lower than that in the low-dose experimental group. However, the incidence of lung cancer was similar in the three equol groups and the genistein group at the same dose. Compared with the control group, the high-dose experimental group had higher serum SOD concentration, lower MDA and 8-OHdG concentrations, and the differences were statistically significant. Western blotting analysis showed that the expression levels of Nrf2 protein in the experimental groups were higher than those in the control group except the low-dose racemic equol group, and the Nrf2 protein expression level in the high-dose equol groups was higher than that in the low-dose equol groups.

CONCLUSION

Racemic equol and its enantiomers mayinhibit lung carcinogenesis through antioxidant effects.

Manganese-Pincer-Catalyzed Nitrile Hydration, α-Deuteration, and α-Deuterated Amide Formation via Metal Ligand Cooperation

A simple and efficient system for the hydration and α-deuteration of nitriles to form amides, α-deuterated nitriles, and α-deuterated amides catalyzed by a single pincer complex of the earth-abundant manganese capable of metal–ligand cooperation is reported. The reaction is selective and tolerates a wide range of functional groups, giving the corresponding amides in moderate to good yields. Changing the solvent from tert-butanol to toluene and using D₂O results in formation of α-deuterated nitriles in high selectivity. Moreover, α-deuterated amides can be obtained in one step directly from nitriles and D₂O in THF. Preliminary mechanistic studies suggest the transformations contributing toward activation of the nitriles via a metal–ligand cooperative pathway, generating the manganese ketimido and enamido pincer complexes as the key intermediates for further transformations.

Neutrophil-lymphocyte ratio and hypersensitive C-reaction protein are associated with miscarriage during the second trimester of pregnancy

This study investigated whether biomarkers in the second trimester of pregnancy, including the white blood cell (WBC) count, neutrophil-lymphocyte ratio (NLR), hypersensitive C-reactive protein (hs-CRP) concentration, and procalcitonin (PCT) concentration, were associated with miscarriage during the second trimester of pregnancy. Sixty-two asymptomatic patients in their second trimester of pregnancy were included in the control group (group A). Among 67 patients diagnosed with late threatened miscarriage, 46 patients with ongoing pregnancy were included in group B and 21 patients with subsequent miscarriage were included in group C. The serum of these patients was collected and the biomarkers were analyzed. A paired-samples t-test was used for the comparison between the groups before and after the miscarriage. Statistical significance was set at p<0.05. Receiver operating characteristic curve (ROC) analysis was performed to evaluate the predictive value of different biomarkers for miscarriage during the second trimester of pregnancy. WBC count, neutrophil percentage, and hs-CRP levels were significantly higher in group C than in groups A and B (p<0.05). Lymphocyte percentage and albumin levels decreased significantly from group A to group C (p<0.05). In contrast, NLR increased significantly from group A to group C (p<0.05). There was a significant decrease in the WBC count, neutrophil percentage, hemoglobin concentration, and post-miscarriage NLR among the cases with miscarriage (p<0.05). The area under the curve of WBC count, NLR, hs-CRP, and the combination of these three factors for the prediction of late miscarriage varied from 78.0% to 82.6%. The combination of these three factors had the highest specificity of 91.1%, while hs-CRP had the highest sensitivity of 88.9%. WBC count, NLR, and hs-CRP levels are strongly associated with miscarriage during the second trimester of pregnancy, indicating that they are potential predictive biomarkers.

Sterics and Hydrogen Bonding Control Stereochemistry and Self-Sorting in BINOL-Based Assemblies

Here we demonstrate how the hydrogen-bonding ability of a BINOL-based dialdehyde subcomponent dictated the stereochemical outcome of its subsequent self-assembly into one diastereomeric helicate form when bearing free hydroxy groups, and another in the case of its methylated congener. The presence of methyl groups also altered the self-sorting behavior when mixed with another, short linear dialdehyde subcomponent, switching the outcome of the system from narcissistic to integrative self-sorting. In all cases, the axial chirality of the BINOL building block also dictated helicate metal center handedness during stereospecific self-assembly. A new family of stereochemically pure heteroleptic helicates were thus prepared using the new knowledge gained. We also found that switching from Fe^II to Zn^II, or the incorporation of a longer linear ligand, favored heteroleptic structure formation.

Homogeneous Reforming of Aqueous Ethylene Glycol to Glycolic Acid and Pure Hydrogen Catalyzed by Pincer-Ruthenium Complexes Capable of Metal-Ligand Cooperation

Glycolic acid is a useful and important α-hydroxy acid that has broad applications. Herein, the homogeneous ruthenium catalyzed reforming of aqueous ethylene glycol to generate glycolic acid as well as pure hydrogen gas, without concomitant CO₂ emission, is reported. This approach provides a clean and sustainable direction to glycolic acid and hydrogen, based on inexpensive, readily available, and renewable ethylene glycol using 0.5 mol % of catalyst. In-depth mechanistic experimental and computational studies highlight key aspects of the PNNH-ligand framework involved in this transformation.

Metal–organic cages for molecular separations

Separation technology is central to industries as diverse as petroleum, pharmaceuticals, mining and life sciences. Metal-organic cages, a class of molecular containers formed via coordination-driven self-assembly, show great promise as separation agents. Precise control of the shape, size and functionalization of cage cavities enables them to selectively bind and distinguish a wide scope of physicochemically similar substances in solution. Extensive research has, thus, been performed involving separations of high-value targets using coordination cages, ranging from gases and liquids to compounds dissolved in solution. Enantiopure capsules also show great potential for the separation of chiral molecules. The use of crystalline cages as absorbents, or the incorporation of cages into polymer membranes, could increase the selectivity and efficiency of separation processes. This Review covers recent progress in using metal-organic cages to achieve separations, with discussion of the many methods of using them in this context. Challenges and potential future developments are also discussed.

A Reversible Liquid-to-Liquid Organic Hydrogen Carrier System Based on Ethylene Glycol and Ethanol

Liquid organic hydrogen carriers (LOHCs) are powerful systems for the efficient unloading and loading molecular hydrogen. Herein, a liquid-to-liquid organic hydrogen carrier system based on reversible dehydrogenative coupling of ethylene glycol (EG) with ethanol catalysed by ruthenium pincer complexes is reported. Noticeable advantages of the current LOHC system is that both reactants (hydrogen-rich components) and the produced esters (hydrogen-lean components) are liquids at room temperature, and the dehydrogenation process can be performed under solvent and base-free conditions. Moreover, the hydrogenation reaction proceeds under low hydrogen pressure (5 bar), and the LOHC system has a relatively high theoretical gravimetric hydrogen storage capacity (HSC>5.0 wt %), presenting an attractive hydrogen storage system.

Hydrogenative Depolymerization of Nylons

The widespread crisis of plastic pollution demands discovery of new and sustainable approaches to degrade robust plastics such as nylons. Using a green and sustainable approach based on hydrogenation, in the presence of a ruthenium pincer catalyst at 150 °C and 70 bar H₂, we report here the first example of hydrogenative depolymerization of conventional, widely used nylons and polyamides, in general. Under the same catalytic conditions, we also demonstrate the hydrogenation of a polyurethane to produce diol, diamine, and methanol. Additionally, we demonstrate an example where monomers (and oligomers) obtained from the hydrogenation process can be dehydrogenated back to a poly(oligo)amide of approximately similar molecular weight, thus completing a closed loop cycle for recycling of polyamides. Based on the experimental and density functional theory studies, we propose a catalytic cycle for the process that is facilitated by metal–ligand cooperativity. Overall, this unprecedented transformation, albeit at the proof of concept level, offers a new approach toward a cleaner route to recycling nylons.

Synthesis of oxalamides by acceptorless dehydrogenative coupling of ethylene glycol and amines and the reverse hydrogenation catalyzed by ruthenium

A sustainable, new synthesis of oxalamides, by acceptorless dehydrogenative coupling of ethylene glycol with amines, generating H₂, homogeneously catalyzed by a ruthenium pincer complex, is presented. The reverse hydrogenation reaction is also accomplished using the same catalyst. A plausible reaction mechanism is proposed based on stoichiometric reactions, NMR studies, X-ray crystallography as well as observation of plausible intermediates.

Ruthenium catalyzed acceptorless dehydrogenative coupling of ethylene glycol and amines to oxalamides is reported. The reverse hydrogenation reaction is also accomplished.

A Thioxanthone Sensitizer with a Chiral Phosphoric Acid Binding Site: Properties and Applications in Visible Light-Mediated Cycloadditions

A chiral phosphoric acid with a 2,2’‐binaphthol core was prepared that displays two thioxanthone moieties at the 3,3’‐position as light‐harvesting antennas. Despite its relatively low triplet energy, the phosphoric acid was found to be an efficient catalyst for the enantioselective intermolecular [2+2] photocycloaddition of β‐carboxyl‐substituted cyclic enones (e.r. up to 93:7). Binding of the carboxylic acid to the sensitizer is suggested by NMR studies and by DFT calculations to occur by means of two hydrogen bonds. The binding event not only enables an enantioface differentiation but also modulates the triplet energy of the substrates.

Recent Advances in Enantioselective Photochemical Reactions of Stabilized Diazo Compounds

Diazo compounds have proven to be a useful class of carbenes or metal carbenoids sources under thermal, photochemical, or metal-catalyzed conditions, which can subsequently undergo a wide range of synthetically important transformations. Recently, asymmetric photocatalysis has provoked increasing research interests, and great advances have been made in this discipline towards the synthesis of optically enriched compounds. In this context, the past two decades have been the most productive period in the developments of enantioselective photochemical reactions of diazo compounds due to a better understanding of the reactivities of diazo compounds and the emergence of new catalytic modes, as well as easier access to and treatment of stabilized diazo compounds. This review highlights these impressive achievements according to the reaction type, and the general mechanisms and stereochemical inductions are briefly discussed as well.

Ethylene Glycol as an Efficient and Reversible Liquid Organic Hydrogen Carrier

Hydrogen has long been regarded as an ideal alternative clean energy vector to overcome the drawbacks of fossil technology. However, the direct utilization of hydrogen is challenging, due to low volumetric energy density of hydrogen gas and potential safety issues. Herein, we report an efficient and reversible liquid to liquid organic hydrogen carrier system based on inexpensive, readily available and renewable ethylene glycol. This hydrogen storage system enables the efficient and reversible loading and discharge of hydrogen using a ruthenium pincer complex, with a theoretical hydrogen storage capacity of 6.5 wt%.

Visible-Light-Induced Organic Photochemical Reactions through Energy-Transfer Pathways

Visible-light photocatalysis is a rapidly developing and powerful strategy to initiate organic transformations, as it closely adheres to the tenants of green and sustainable chemistry. Generally, most visible-light-induced photochemical reactions occur through single-electron transfer (SET) pathways. Recently, visible-light-induced energy-transfer (EnT) reactions have received considerable attentions from the synthetic community as this strategy provides a distinct reaction pathway, and remarkable achievements have been made in this field. In this Review, we highlight the most recent advances in visible-light-induced EnT reactions.

Highly Selective, Efficient Deoxygenative Hydrogenation of Amides Catalyzed by a Manganese Pincer Complex via Metal-Ligand Cooperation

Deoxygenative hydrogenation of amides to amines homogeneously catalyzed by a complex of an Earth-abundant metal is presented. This manganese-catalyzed reaction features high efficiency and selectivity. A plausible reaction mechanism, involving metal–ligand cooperation of the manganese pincer complex, is proposed based on NMR studies and relevant stoichiometric reactions.

Iminium and enamine catalysis in enantioselective photochemical reactions

The rapidly growing area of iminium and enamine catalysis in enantioselective photochemistry is reviewed, with an emphasis on catalytic modes and reaction types.

Although enantioselective catalysis under thermal conditions has been well established over the last few decades, the enantioselective catalysis of photochemical reactions is still a challenging task resulting from the complex enantiotopic face differentiation in the photoexcited state. Recently, remarkable achievements have been reported by a synergistic combination of organocatalysis and photocatalysis, which have led to the expedient construction of a diverse range of enantioenriched molecules which are generally not easily accessible under thermal conditions. In this tutorial review, we summarize and highlight the most significant advances in iminium and enamine catalysis of enantioselective photochemical reactions, with an emphasis on catalytic modes and reaction types.

Recent Advances in the Synthesis of Cyclobutanes by Olefin [2 + 2] Photocycloaddition Reactions

The [2 + 2] photocycloaddition is undisputedly the most important and most frequently used photochemical reaction. In this review, it is attempted to cover all recent aspects of [2 + 2] photocycloaddition chemistry with an emphasis on synthetically relevant, regio-, and stereoselective reactions. The review aims to comprehensively discuss relevant work, which was done in the field in the last 20 years (i.e., from 1995 to 2015). Organization of the data follows a subdivision according to mechanism and substrate classes. Cu(I) and PET (photoinduced electron transfer) catalysis are treated separately in sections 2 and 4 , whereas the vast majority of photocycloaddition reactions which occur by direct excitation or sensitization are divided within section 3 into individual subsections according to the photochemically excited olefin.

Direct sp3 C–H acroleination of N-aryl-tetrahydroisoquinolines by merging photoredox catalysis with nucleophilic catalysis

Sequence catalysis merging photoredox catalysis (PC) and nucleophilic catalysis (NC) has been realized for the direct sp³ C–H acroleination of N-aryl-tetrahydroisoquinoline (THIQ), affording products in 50–91% yields.

Tetrakis(mu-2,3-dimethoxybenzoato)bis[(2,2'-bipyridine)(2,3-dimethoxybenzoato)lanthanum(III)]

The title compound, tetrakis(mu-2,3-dimethoxybenzoato)-kappa(4)O:O';kappa(6)O,O':O'-bis[(2,2'-bipyridine-N,N')(2,3-dimethoxybenzoato-O,O')lanthanum(III)], [La(2)(2,3-DMOBA)(6)(2,2'-bpy)(2)], where 2,3-DMOBA is 2,3-dimethoxybenzoate (C(9)H(9)O(4)) and 2,2'-bpy is 2,2'-bipyridine (C(10)H(8)N(2)), is a dimer with a centre of inversion between the La atoms bridged by four carboxylate ligands. The central La atom is ennea-coordinated and has a distorted monocapped square-antiprism geometry.

catena-Poly[europium-tri-mu-4-methyl-benzoato]

Each Eu3+ ion in the title compound, catena-poly[europium(III)-tri-mu-4-methylbenzoato-O:O,O';O:O,O';O,O':O'], [[Eu(C8H7O2)3]3]n, is coordinated by nine O atoms, and three Eu atoms form a trimeric unit. These trimeric units are linked by bridging-chelating carboxylates to form an infinite one-dimensional polymer chain.

Generation of monoclonal antibodies to bovine follicle-stimulating hormone and application in an enzyme immunoassay

Twenty monoclonal antibodies (MAbs) to bovine follicle-stimulating hormone (bFSH) were generated by using the hybridoma technique. Twelve of the MAbs have been shown to bind specifically to bFSH and seven of them were purified from the respective ascitic fluids with the methods of caprylic acid precipitation and hydroxylapatite column chromatography. The purity of the MAbs was in the range of 86-95%. Three of the purified MAbs have been coupled to horseradish peroxidase (HRP). By using a matrix cross-matching procedure, two MAbs reacted with discrete antigenic determinants are selected for a double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). The designed ELISA procedure could be performed within 60 min in a two-stage incubation and has a minimum sensitivity of 1ngFSH/ml. For serum samples, its mean intra- and inter-assay coefficients of variation were 3.4% and 7.3% respectively. The DAS-ELISA can be used to establish a complete FSH profile in the field of in vitro diagnosis.