Hydraulic property variations with depth in a loess mudstone landslide.

In areas where loess is distributed, landslides represent a significant geohazard with severe implications. Among these events, loess-mudstone landslides are particularly prevalent, posing substantial risks to the safety and property of local residents, and moisture plays a pivotal role as a key factor in causing these disasters. In this study, the hydraulic properties of the soils along the longitudinal section of an ongoing loess-mudstone landslide are investigated through the variation of soil water characteristic curves, which are subsequently fitted by utilizing van Genuchten model. Moreover, a comprehensive experimental investigation was conducted on the loess, mudstone, and loess-mudstone mixtures to facilitate analysis, including X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) observation, particle size distribution (PSD) analysis, along with fundamental geotechnical tests for parameter determination. It is found that mudstone and loess have distinct SWCC distribution. The SWCC of loess at various depths exhibits a similar distribution pattern due to the occurrence of landslide. The SWCC distribution of loess-mudstone mixture displays a transitional trend between the SWCC of mudstone and that of loess, and the water retention capacity increases as the mudstone content increases. The experimental findings have demonstrated notable agreement between each other and exhibited a satisfactory level of concurrence with the observed phenomena in geological surveys.

High-Performance Aluminum Fuels Induced by Monolayer Self-Assembly of Nano-Sized Energetic Fluoride Vesicles on the Surface.

Surface modification is frequently used to solve the problems of low combustion properties and agglomeration for aluminum-based fuels. However, due to the intrinsic incompatibility between the aluminum powder and the organic modifiers, the surface coating is usually uneven and disordered, which significantly deteriorates the uniformity and performances of the Al-based fuels. Herein, a new approach of monolayer nano-vesicular self-assembly is proposed to prepare high-performance Al fuels. Triblock copolymer G-F-G is produced by glycidyl azide polymer (GAP) and 2,2'-(2,2,3,3,4,5,5-Octafluorohexane-1,6-diyl) bis (oxirane) (fluoride) ring-open addition reaction. By utilizing G-F-G vesicular self-assembly in a special solvent, the nano-sized vesicles are firmly adhered to the surface of Al powder through the long-range attraction between the fluorine segments and Al. Meanwhile, the electrostatic repulsion between vesicles ensures an extremely thin coating thickness (≈15 nm), maintaining the monolayer coating structure. Nice ignition, combustion, anti-agglomeration, and water-proof properties of Al@G-F-G(DMF) are achieved, which are superior among the existing Al-based fuels. The derived Al-based fuel has excellent comprehensive properties, which can not only inspire the development of new-generation energetic materials but also provide facile but exquisite strategies for exquisite surface nanostructure construction via ordered self-assembly for many other applications.

Research progress of prodrugs for the treatment of cerebral ischemia.

It is well-known that pharmacotherapy plays a pivotal role in the treatment and prevention of cerebral ischemia. Nevertheless, existing drugs, including numerous natural products, encounter various challenges when applied in cerebral ischemia treatment. These challenges comprise poor brain absorption due to low blood-brain barrier (BBB) permeability, limited water solubility, inadequate bioavailability, poor stability, and rapid metabolism. To address these issues, researchers have turned to prodrug strategies, aiming to mitigate or eliminate the adverse properties of parent drug molecules. In vivo metabolism or enzymatic reactions convert prodrugs into active parent drugs, thereby augmenting BBB permeability, improving bioavailability and stability, and reducing toxicity to normal tissues, ultimately aiming to enhance treatment efficacy and safety. This comprehensive review delves into multiple effective prodrug strategies, providing a detailed description of representative prodrugs developed over the past two decades. It underscores the potential of prodrug approaches to improve the therapeutic outcomes of currently available drugs for cerebral ischemia. The publication of this review serves to enrich current research progress on prodrug strategies for the treatment and prevention of cerebral ischemia. Furthermore, it seeks to offer valuable insights for pharmaceutical chemists in this field, offer guidance for the development of drugs for cerebral ischemia, and provide patients with safer and more effective drug treatment options.

Facial emotion recognition function and white matter microstructural alterations in drug-naive, comorbidity-free autism.

Individuals with autism spectrum disorder have deficits in facial emotion recognition and white matter microstructural alterations. Nonetheless, most previous studies were confounded by different variables, such as psychiatric comorbidities and psychotropic medications used by ASD participants. Also, it remains unclear how exactly FER deficits are related to white matter microstructural alterations in ASD. Accordingly, we aimed to investigate the FER functions, white matter microstructure, and their relationship in drug-naive and comorbidity-free ASD individuals. 59 ASD individuals and 59 typically developed individuals were included, where 46 ASD and 50 TD individuals completed FER tasks. Covariance analysis showed scores were lower in both basic and complex FER tasks in the ASD group. Tract-Based Spatial Statistics showed FA values in widespread white matter fibers were lower in the ASD group than in the TD group, including forceps major and forceps minor of the corpus callosum, anterior thalamic radiation, corticospinal tract, cingulum, inferior frontal-occipital fasciculus, inferior longitudinal fasciculus, superior longitudinal fasciculus. Moreover, in the TD group but not the ASD group, the performance in the complex FER task was negatively correlated with the FA value in some white matter fibers, including forceps major of the corpus callosum, ATR, CT, cingulum, IFOF, ILF, SLF. Our study suggests children with ASD may experience deficits in facial emotion recognition and exhibit alterations in white matter microstructure. More importantly, our study indicates that white matter microstructural alterations may be involved in FER deficits in children with ASD.

Long-term prognosis of patients with gallbladder carcinoma after curative-intent resection based on changes in the ratio of carbohydrate antigen 19-9 to total bilirubin (CA19-9/TB): a multicenter retrospective cohort study.

BACKGROUND: The prognostic value of carbohydrate antigen 19-9 (CA19-9) is known to be affected by elevated bilirubin levels in patients with gallbladder carcinoma (GBC). The clinical significance of changes in the ratio of CA19-9 levels to total bilirubin (TB) levels in patients with GBC after curative-intent resection remains unknown. The aim of this study was to determine the prognostic value of changes in preoperative and postoperative CA19-9/TB ratio in these patients. METHODS: Prospectively colleced data on consecutive patients who underwent curative-intent resection for GBC between January 2015 and December 2020 stored in a multicenter database from 10 hospitals were analysed in this retrospective cohort study. Based on the adjusted CA19-9 defined as the ratio of CA19-9 to TB, and using 2×103 U/µmol as the upper normal value, patients were divided into a normal group (with normal preoperative and postoperative adjusted CA19-9), a normalization group (with abnormal preoperative but normal postoperative adjusted CA19-9), and a non-normalization group (with abnormal postoperative adjusted CA19-9). The primary outcomes were overall survival (OS) and recurrence-free survival (RFS). The log-rank test was used to compare OS and RFS among the groups. The Cox regression model was used to determine factors independently associated with OS and RFS. RESULTS: The normal group (n=179 patients) and the normalization group (n=73 patients) had better OS and RFS than the non-normalization group (n=65 patients) (the 3-year OS rates 72.0%, 58.4% and 24.2%, respectively; the RFS rates 54.5%, 25.5% and 11.8%, respectively; both P<0.001). There were no significant differences between the normal and the normalization groups in OS and RFS (OS, P=0.255; RFS, P=0.130). Cox regression analysis confirmed that the non-normalization group was independently associated with worse OS and RFS. Subgroup analysis revealed that the non-normalization group of patients who received adjuvant therapy had significantly improved OS and RFS as compared to those who did not receive adjuvant therapy (OS, P=0.025; RFS, P=0.003). CONCLUSIONS: Patients with GBC who underwent curative-intent surgical resection with postoperative abnormal levels of adjusted CA19-9 (the CA19-9/TB ratio) were associated with poorer long-term survival outcomes. Adjuvant therapy after surgery improved the long-term outcomes of these patients.

Hypermethylation of the glutathione peroxidase 4 gene promoter is associated with the occurrence of immune tolerance phase in chronic hepatitis B.

BACKGROUND: Hepatitis B virus (HBV) infection is a public health problem that seriously threatens human health. This study aimed to investigate the clinical significance of glutathione peroxidase 4(GPX4) in the occurrence and development of chronic hepatitis B (CHB). METHODS: A total of 169 participants including 137 patients with CHB and 32 healthy controls (HCs) were recruited. We detected the expression of GPX4 and stimulator of interferon genes (STING) in peripheral blood mononuclear cells (PBMCs) by real-time quantitative polymerase chain reaction (RT-qPCR). The methylation level of GPX4 gene promoter in PBMCs was detected by TaqMan probe-based quantitative methylation-specific PCR (MethyLight). Enzyme-linked immunosorbent assay (ELISA) was performed to detect the serum levels of GPX4, IFN-ß, oxidative stress (OS) related molecules, and pro-inflammatory cytokines. RESULTS: The expression levels of GPX4 in PBMCs and serum of CHB patients were lower than those of HCs, but the methylation levels of GPX4 promoter were higher than those of HCs, especially in patients at the immune tolerance phase. STING mRNA expression levels in PBMCs and serum IFN-ß levels of patients at the immune activation phase and reactivation phase of CHB were higher than those at other clinical phases of CHB and HCs. GPX4 mRNA expression level and methylation level in PBMCs from patients with CHB had a certain correlation with STING and IFN-ß expression levels. In addition, the methylation level of the GPX4 promoter in PBMCs from patients with CHB was correlated with molecules associated with OS and inflammation. CONCLUSIONS: GPX4 may play an important role in the pathogenesis and immune tolerance of CHB, which may provide new ideas for the functional cure of CHB.

Empowerment-Led Guided Self-Help Intervention for Symptom Burden in Breast Cancer Women Treated With Ovarian Function Suppression: A Randomized Trial Protocol.

Background: Ovarian function suppression (OFS) treatment causes breast cancer patients' estrogens to fall rapidly to postmenopausal levels, and the 5-year treatment duration and 28-day treatment cycles place a heavy physical and psychological symptom burden on them, which in turn directly or indirectly affects the survival benefit. Managing symptom burden early in treatment is critical, but OFS-related studies have yet to be seen. Self-management is essential for patients' symptom burden. However, self-help management is hampered by patients' lack of knowledge, skills, motivation, etc. Guided self-help intervention (GSH) provides a feasible approach. Empowerment theory is a promising theoretical framework to guide self-management. Methods: A prospective two-arm parallel randomized controlled single-blind clinical trial will be conducted to investigate the effect of symptom burden GSH based on empowerment theory in breast cancer patients in the early stages of OFS treatment. A block randomization method is used to allocate 144 patients to either the control or intervention group. The program is conducted according to the OFS return-to-hospital treatment cycle. The intervention group will receive a total of two rounds and five sessions of empowering GSH, lasting at least 15 weeks in total; the control group will receive only usual nursing care. Symptom burden and related metrics will be assessed at baseline and 1, 3, and 6 months after OFS treatment, and changes between and within groups will be explored. This paper adhered to the SPIRIT and CONSORT guidelines. Conclusion: These results will help to validate the GSH in symptom burden management for breast cancer patients in OFS treatment early stages. It enriches its symptom burden management research and may provide implications for the whole cycle of OFS treatment patients.

People can reliably detect action changes and goal changes during naturalistic perception.

As a part of ongoing perception, the human cognitive system segments others' activities into discrete episodes (event segmentation). Although prior research has shown that this process is likely related to changes in an actor's actions and goals, it has not yet been determined whether untrained observers can reliably identify action and goal changes as naturalistic activities unfold, or whether the changes they identify are tied to visual features of the activity (e.g., the beginnings and ends of object interactions). This study addressed these questions by examining untrained participants' identification of action changes, goal changes, and event boundaries while watching videos of everyday activities that were presented in both first-person and third-person perspectives. We found that untrained observers can identify goal changes and action changes consistently, and these changes are not explained by visual change and the onsets or offsets of contact with objects. Moreover, the action and goal changes identified by untrained observers were associated with event boundaries, even after accounting for objective visual features of the videos. These findings suggest that people can identify action and goal changes consistently and with high agreement, that they do so by using sensory information flexibly, and that the action and goal changes they identify may contribute to event segmentation.

Adsorption of Zn(II) from aqueous solution and separation of zinc isotopes by displacement chromatography using chelating adsorbent.

The removal of zinc ions (Zn(II)) in water and the separation of zinc isotopes were fully investigated in this study. Imidodiacetic acid (IDA) type adsorbent (named PSGI) based on polystyrene spheres (PS) was synthesized by simultaneous irradiation grafting. By adsorption method, the removal of Zn(II) from water by the chelating adsorbent was studied in batch experiments. Under optimized condition, PSGI showed the removal efficiency of more than 98 % for Zn(II) and the adsorption capacity of 70.1 mg/g. Langmuir isothermal and pseudo-second-order kinetic model fitted the experimental results better, indicating that the adsorption is dominated by chemical adsorption. The spent adsorbent (PSGI-Zn) was used for further zinc isotope separation by displacement chromatography using EDTA-NH4 solution as eluent. Due to the mass effect of isotopes, 70Zn was found to preferentially fractionated into the front-end effluents with the highest front enrichment values of 70Zn/64Zn. By extending the migration distance to 20 m, we obtained the best isotope enrichment with the front maximum enrichment values as 1.0949, 1.0739 and separation coefficient values as 1.977 × 10-3, 8.33 × 10-3 corresponding to the isotope pairs 66Zn/64Zn, 68Zn/64Zn.

Compensation of the tool influence function changes under neighborhood effect in atmospheric pressure plasma processing.

Nowadays, computer controlled optical surfacing (CCOS) is greatly developed in the fabrication of ultra-precision optical surfaces. As one of the deterministic CCOS techniques, atmospheric pressure plasma processing (APPP) can achieve the efficient removal based on the chemical reaction. In this process, the temperature rising issue caused by plasma heating is of great importance for accelerating the etching rate, but also increases the difficulty of deterministic removal control, because the tool influence function (TIF) in APPP is no longer time-invariant. In the existing research, the time-variant TIF model can describe the TIF changes to a certain degree, which is considered in the dwell time calculation. However, there inevitably exists the strong neighborhood effect, which indicates that the TIFs of different dwell points are thermally interacted. Thus, the existing time-variant TIF model is no longer accurate for predicting TIF changes, and not suitable for application to further compensation. To solve this, the compensation of TIF changes under neighborhood effect is proposed in this paper. First, the mechanism of TIF changes caused by neighborhood effect is explained in depth. Then, the theoretical analysis is implemented and the compensation method is systematically discussed, encompassing the tool path optimization, model of TIF changes and dwell time calculation. Further, the proposed method is demonstrated and verified by a series of simulations. Finally, the experimental validation is carried out, which proves the capability of achieving high-precision removal and high convergence rate.

F-box protein 43 promoter methylation as a novel biomarker for hepatitis B virus-associated hepatocellular carcinoma.

Background: Hepatocellular carcinoma (HCC) has a high prevalence and poor prognosis worldwide. Therefore, it is urgent to find effective and timely diagnostic markers. The objective of this study was to evaluate the diagnostic value of F-box protein 43 promoter methylation in peripheral blood mononuclear cells (PBMCs) for HCC. Method: A total of 247 participants were included in this study, comprising individuals with 123 hepatitis B virus-associated HCC, 79 chronic hepatitis B, and 45 healthy controls. F-box protein 43 methylation and mRNA levels in PBMCs were detected by MethyLight and quantitative real-time PCR. Result: F-box protein 43 promoter methylation levels were significantly lower in HCC PBMCs than the chronic hepatitis B (P < 0.001) and healthy control PBMCs (P < 0.001). Relative mRNA expression levels of F-box protein 43 in HCC PBMCs were significantly higher than those in chronic hepatitis B (P < 0.001) and healthy control PBMCs (P < 0.001). Receiver operating characteristic analysis of F-box protein 43 promoter methylation levels yielded an area under curve (AUC) of 0.793 with 76.42% sensitivity and 68.35% specificity when differentiating HCC from chronic hepatitis. These values for the F-box protein 43 promoter methylation level were superior to those of the alpha-fetoprotein serum (AFP) level (AUC: 0.780, sensitivity: 47.97%, and specificity: 96.20%), with increments in values for the combination of F-box protein 43 promoter methylation AFP levels (AUC: 0.888, sensitivity: 76.42%, and specificity: 86.08%). Conclusion: Hypomethylation of the F-box protein 43 promoter in PBMCs is a promising biochemical marker for HBV-associated HCC.

Metabolic plasticity sustains the robustness of Caenorhabditis elegans embryogenesis.

Embryogenesis is highly dependent on maternally loaded materials, particularly those used for energy production. Different environmental conditions and genetic backgrounds shape embryogenesis. The robustness of embryogenesis in response to extrinsic and intrinsic changes remains incompletely understood. By analyzing the levels of two major nutrients, glycogen and neutral lipids, we discovered stage-dependent usage of these two nutrients along with mitochondrial morphology changes during Caenorhabditis elegans embryogenesis. ATGL, the rate-limiting lipase in cellular lipolysis, is expressed and required in the hypodermis to regulate mitochondrial function and support embryogenesis. The embryonic lethality of atgl-1 mutants can be suppressed by reducing sinh-1/age-1-akt signaling, likely through modulating glucose metabolism to maintain sustainable glucose consumption. The embryonic lethality of atgl-1(xd314) is also affected by parental nutrition. Parental glucose and oleic acid supplements promote glycogen storage in atgl-1(xd314) embryos to compensate for the impaired lipolysis. The rescue by parental vitamin B12 supplement is likely through enhancing mitochondrial function in atgl-1 mutants. These findings reveal that metabolic plasticity contributes to the robustness of C. elegans embryogenesis.

Effect of Microwave Annealing on the Sensing Characteristics of HfO2 Thin Film for High Sensitive pH-EGFET Sensor.

Recently, certain challenges have persisted in PH sensor applications, especially when employing hafnium oxide (HfO2) thin films as sensing layers, where issues related to sensitivity, hysteresis, and long-term stability hamper performance. Microwave annealing (MWA) technology, as a promising solution for addressing these challenges, has gained significant attraction due to its unique advantages. In this article, the effects of microwave annealing (MWA) treatment on the sensing behaviors of Extended-Gate Field-Effect Transistors (EGFETs) utilizing HfO2 as a sensing film have been investigated for the first time. Various power levels of MWA treatment (1750 W/2100 W/2450 W) were selected to explore the optimal processing conditions. A thorough physical analysis was conducted to characterize the surface of the MWA-treated HfO2 sensing thin film using techniques such as X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Our findings reveal that MWA treatment effectively increased the surface sites (Ns) in the HfO2 sensing thin film, consequently leading to an increase in the pH sensitivity of EGFETs to 59.6 mV/pH, as well as a reduction in hysteresis and an enhancement in long-term stability. These results suggest that MWA offers a straightforward, energy-efficient method to enhance overall HfO2 sensing film performance in EGFETs, offering insights for HfO2 applications and broader microelectronics challenges.

Rapid and Controllable Preparation of Multifunctional Lignin-Based Eutectogels for the Design of High-Performance Flexible Sensors.

Currently, there is a limited amount of research on PEDOT:LS (poly(3,4-ethylenedioxythiophene):sulfonated lignin)-based hydrogels. While the addition of PEDOT:LS can enhance the conductivity of the gel, it unavoidably disrupts the gel network and negatively affects its mechanical properties. The preparation process and freezing resistance of the hydrogels also pose significant challenges for their practical applications. In this study, we have developed a novel self-catalytic system, PEDOT:LS-Fe3+, for the rapid fabrication of conductive hydrogels. These hydrogels are further transformed into eutectogels by immersing them in a deep eutectic solvent. Compared with conventional hydrogels, the eutectogels exhibit improved elongation, mechanical strength, and resistance to freezing. Specifically, the eutectogels containing 2 wt % PEDOT:LS as conductive fillers and catalysts demonstrate exceptional stretchability (∼460%), self-adhesion (∼14.6 kPa on paper), UV-blocking capability (∼99.9%), and ionic conductivity (∼1.2 mS cm-1) even at extremely low temperatures (-60 °C). Moreover, the eutectogels exhibit high stability and sensitivity in flexible sensing, successfully detecting various human motions. This study presents a novel approach for the rapid preparation of the hydrogels by utilizing lignin in the conductive PEDOT polymerization process and forming a self-catalytic system with metal ions. These advancements make the eutectogels a promising candidate material for flexible wearable electronics.

The roles of phospholipase C-ß related signals in the proliferation, metastasis and angiogenesis of malignant tumors, and the corresponding protective measures.

PLC-ß is widely distributed in eukaryotic cells and is the key enzyme in phosphatidylinositol signal transduction pathway. The cellular functions regulated by its four subtypes (PLC-ß1, PLC-ß2, PLC-ß3, PLC-ß4) play an important role in maintaining homeostasis of organism. PLC-ß and its related signals can promote or inhibit the occurrence and development of cancer by affecting the growth, differentiation and metastasis of cells, while targeted intervention of PLC-ß1-PI3K-AKT, PLC-ß2/CD133, CXCR2-NHERF1-PLC-ß3, Gαq-PLC-ß4-PKC-MAPK and so on can provide new strategies for the precise prevention and treatment of malignant tumors. This paper reviews the mechanism of PLC-ß in various tumor cells from four aspects: proliferation and differentiation, invasion and metastasis, angiogenesis and protective measures.

Hypomethylation of Tumor necrosis factor-like cytokine 1A(TL1A) and its decoy receptor 3 expressive level increase has diagnostic value in HBV-associated cirrhosis.

For patients with cirrhosis, early diagnosis is the key to delaying the development of liver fibrosis and improving prognosis. This study aimed to investigate the clinical significance of TL1A, which is a susceptibility gene for hepatic fibrosis, and DR3 in the development of cirrhosis and fibrosis. We analyzed the expression of TL1A, DR3, and other inflammatory cytokines associated with liver fibrosis in serum and PBMCs in 200 patients.TL1A methylation level was lower in patients with HBV-associated LC than in the other groups. In addition, the mRNA level and serum of TL1A and DR3 expression levels were found to increase in the LC. Hypomethylation of the TL1A promoter is present in HBV-associated LC, and TL1A and DR3 are highly expressed in HBV-associated cirrhosis. These results indicate that TL1A and DR3 may play an important role in the pathogenesis of LC and TL1A methylation levels may serve as a noninvasive biomarker for early diagnosis and progression of LC.

Effects of tillage patterns and stover mulching on N2O production, nitrogen cycling genes and microbial dynamics in black soil.

Stover-covered no-tillage (NT) is of great significance to the rational utilization of stover resources and improvement of cultivated land quality, and also has a profound impact on ensuring groundwater, food and ecosystem security. However, the effects of tillage patterns and stover mulching on soil nitrogen turnover remain elusive. Based on the long-term conservation tillage field experiment in the mollisol area of Northeast China since 2007, the shotgun metagenomic sequencing of soils and microcosm incubation were combined with physical and chemical analyses, alkyne inhibition analysis to elucidate the regulatory mechanisms of NT and stover mulching on the farmland soil nitrogen emissions and microbial nitrogen cycling genes. Compared with conventional tillage (CT), NT stover mulching significantly reduced the emission of N2O instead of CO2, especially when 33% mulching was adopted, and correspondingly the nitrate nitrogen of NT33 was higher than that of other mulching amounts. The stover mulching was associated with higher total nitrogen, soil organic carbon and pH. The abundance of AOB (ammonia-oxidizing bacteria)-amoA (ammonia monooxygenase subunit A) was substantially increased by stover mulching, while the abundance of denitrification genes was reduced in most cases. Under alkyne inhibition, the tillage mode, treatment time, gas condition and interactions between them noticeably influenced the N2O emission and nitrogen transformation. In CT, NT0 (no mulching) and NT100 (full mulching), the relative contribution of AOB to N2O production was markedly higher than that of ammonia oxidizing archaea. Different tillage modes were associated with distinct microbial community composition, albeit NT100 was closer to CT than to NT0. Compared with CT, the co-occurrence network of microbial communities was more complex in NT0 and NT100. Our findings suggest that maintaining a low-quantity stover mulching could regulate soil nitrogen turnover toward proficiently enhancing soil health and regenerative agriculture, and coping with global climate change.

Cobalt-Catalyzed Hypervalent Iodine(III) Promoted Cascade Annulation Reaction of Anilines with Formamides for 2-Aminobenzoxazoles Synthesis.

Herein, we disclose a practical and simple procedure to synthesize 2-aminobenzoxaoles. Simple anilines and formamides were used as substrates. The C-H bond ortho to the amino group in the anilines was directly functionalized under cobalt-catalyzed conditions with high levels of functional group tolerance. Hypervalent iodine(III) was both an oxidant and a Lewis acid for this reaction. The mechanism study showed that this transformation may involve a radical process.

Computational Exploration of Dirhodium Complex-Catalyzed Selective Intermolecular Amination of Tertiary vs. Benzylic C-H Bonds.

The mechanism and origins of site-selectivity of Rh2(S-tfpttl)4-catalyzed C(sp3)-H bond aminations were studied using density functional theory (DFT) calculations. The synergistic combination of the dirhodium complex Rh2(S-tfpttl)4 with tert-butylphenol sulfamate TBPhsNH2 composes a pocket that can access both tertiary and benzylic C-H bonds. The nonactivated tertiary C-H bond was selectively aminated in the presence of an electronically activated benzylic C-H bond. Both singlet and triplet energy surfaces were investigated in this study. The computational results suggest that the triplet stepwise pathway is more favorable than the singlet concerted pathway. In the hydrogen atom abstraction by Rh-nitrene species, which is the rate- and site-selectivity-determining step, there is an attractive π-π stacking interaction between the phenyl group of the substrate and the phthalimido group of the ligand in the tertiary C-H activation transition structure. By contrast, such attractive interaction is absent in the benzylic C-H amination transition structure. Therefore, the DFT computational results clearly demonstrate how the synergistic combination of the dirhodium complex with sulfamate overrides the intrinsic preference for benzylic C-H amination to achieve the amination of the nonactivated tertiary C-H bond.