35 research outputs found
Mechanistic study of homoleptic trisamidolanthanide-catalyzed aldehyde and ketone hydroboration. Chemically non-innocent ligand participation
No full textCarbonyl bond hydroboration is a valuable synthetic route to functionalized alcohols but relies on sometimes unselective and sluggish reagents. While rapid and selective aldehyde and ketone hydroboration mediated by trisamidolanthanide catalysts is known, the origin of the selectivity is not well-understood and is the subject of this contribution. Here the aldehyde and ketone HBpin hydroboration reaction mechanisms catalyzed by La[N(SiMe3)(2)](3) are investigated both experimentally and theoretically. The results support initial carbonyl oxygen coordination to the acidic La center, followed by intramolecular ligand-assisted hydroboration of the carbonyl moiety by bound HBpin. Interestingly, ketone hydroboration has a higher energetic barrier than that of aldehydes due to the increased steric encumbrance and decreased electrophilicity. Utilizing NMR spectroscopy and X-ray diffraction, a bidentate acylamino lanthanide complex associated with the aldehyde hydroboration is isolated and characterized, consistent with the relative reaction rates. Furthermore, an aminomonoboronate-lanthanide complex produced when the La catalyst is exposed to excess HBpin is isolated and characterized by X-ray diffraction, illuminating unusual aminomonoboronate coordination. These results shed new light on the origin of the catalytic activity patterns, reveal a unique ligand-assisted hydroboration pathway, and uncover previously unknown catalyst deactivation pathways
Chemodivergent Organolanthanide-Catalyzed C–H α‑Mono-Borylation of Pyridines
No full textChemodivergent
synthetic methodologies enable the efficient introduction
of structural diversity into high-value organic products via simple
chemical alterations. In this regard, C–H activation and functionalization
of pyridinoid azines are important transformations in the synthesis
of many natural products, pharmaceuticals, and functional materials.
Reflecting on azinyl nitrogen lone-pair steric repulsion, its tendency
to irreversibly coordinate metal ion catalysts, and the electron deficiency
of pyridine, C–H functionalization at the important α-position
remains challenging. Thus, developing earth-abundant catalysts for
α-selective azine mono-functionalization is an attractive target
for chemical synthesis. Here, the selective organolanthanide-catalyzed
α-mono-borylation of a diverse series of 18 pyridines is reported
using Cp*2LuCH(TMS)2 (Cp* = η5-C5Me5) (TMS = SiMe3) and affording
valuable precursors for subsequent functionalization. Experimental
and theoretical mechanistic data reported here support the intermediacy
of a C–H-activated η2-lanthanide-azine complex,
followed by intermolecular α-mono-borylation via σ-bond
metathesis. Notably, varying the lanthanide identity and substrate
substituent electronic character promotes marked chemodivergence of
the catalytic selectivity: smaller/more electrophilic lanthanide3+ ions and electron-rich substrates favor selective α-C–H
functionalization, whereas larger/less electrophilic lanthanide3+ ions and electron-poor substrates favor selective B–N
bond-forming 1,2-dearomatization. Such lanthanide series catalytic
chemodivergence is, to our knowledge, unprecedented
Chemodivergent Organolanthanide Catalyzed C-H a-Mono-1 Borylation of Azines
No full textC-H activation and functionalization of pyridinoid azines is a key transformation forthe synthesis of many natural products, pharmaceuticals, and materials. Reflecting the azinyl nitrogen lone-pair steric repulsion, tendency to irreversibly bind to metal ion catalysts, and the electron-deficient nature of pyridine, C-H functionalization at the important a-position remains challenging. Thus, the development of earth abundant catalysts for the a-selective mono-functionalization of azines is a crucial hurdle for modern chemical synthesis. Here, the selective organolanthanide catalyzed a-mono-borylation of a diverse series of pyridines is reported, affording a valuable precursor for cross-coupling reactions. Experimental and theoretical mechanistic evidence support the formation of a C-H activated η2-lanthanide-azine complex, followed by intermolecular a-mono-borylation via σ-bond metathesis. Notably, varying the lanthanide identity and substrate electronics promotes chemodivergence of the catalytic selectivity: smaller/more electrophilic lanthanide3+ ions and electron-rich substrates favor selective a-C-H functionalization, whereas larger/less electrophilic lanthanide3+ 1 ions and electron poor substrates favor selective B-N bond-forming 1,2-dearomatization. Such organolanthanide series catalytic chemodivergence is, to our knowledge, unprecedented
Attachment and amae in Japanese romantic relationships
No full textThis is the post-print version for the Article. The official published version can be accessed from the link below - Copyright @ 2012 John Wiley & SonsAmae is a Japanese term that refers to an individual’s inappropriate behavior when he/she presumes indulgence from a significant other. The link between attachment style and amae has been debated, but few studies have examined this link empirically. This study examined the association of attachment style with amae behavior in Japanese dating couples over a two-week period. Results showed that for Japanese men, anxious attachment was positively associated with their amae behavior, and in turn, with their increased relationship quality. Conversely, avoidant attachment was negatively associated with their amae behavior, and in turn, with their decreased relationship quality.This research was supported by a Postdoctoral Fellowship grant awarded by the Japanese Society for the Promotion of Science to the author
Mechanisms of Psychological Distress following War in the Former Yugoslavia: The Role of Interpersonal Sensitivity
No full textThis is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.This study was funded by a grant from the European Commission, contract number INCO-CT-2004-509176. AN was supported by a Clinical Early Career Research Fellowship (113295) and a Project Grant (104288
Catalyst Design to Address Nylon Plastics Recycling
No full textRational tailoring of catalytic systems offers highly desirable transformations targeting the growing environmental challenges associated with plastics pollution. For example, the identification of efficient catalysts to address alarming end-of-life Nylon pollution remains underexplored. Nylon-6 is a non-biodegradable high-performance engineering plastic with centuries of chemical persistence, resulting in millions of tons of waste accumulation. Here we report the rational manipulation of organolanthanide catalyst structure to achieve an exceptionally efficient, solventless, and scalable Nylon-6 depolymerization process, affording monomer ε-caprolactam in ≥99% yield. Specifically, catalyst Cp*₂LaCH(TMS)₂ (Cp* = η₅-C₅Me₅, TMS = SiMe₃) operates at catalyst loadings as low as 0.2 mol% and temperatures as low as 220 °C. For efficient deconstruction of more recalcitrant commodity Nylon-6 end-of-life articles such as fishing nets, car-pets, and clothing, the robust, thermally stable ansa-metallocene catalyst Me₂SiCp’’₂YCH(TMS)₂, (Cp’’ = η₅-C₅Me₄) effects >99% conversion of these items into ε-caprolactam. The collected product can be readily re-polymerized to afford pristine Nylon-6 with higher molecular masses and comparable structural regularity, providing a superior upcycling pathway for end-of-life Nylon plastics. Experimental mechanistic studies reveal intriguing and effective depolymerization pathways, such as catalytic intrachain “unzipping” enabled by the catalyst π-ancillary ligand steric constraints. Effective interchain “hopping” mechanisms, as well as chain-end deactivation are also demonstrated and supported by DFT analyses
Highlights: Multilingual Safety Resources, Pd-Catalyzed Cross-Coupling Reactions, Ethylene Glycol Purification, and More
No full textExposure and the reduction of fear of pain
No full textThis research investigated interoceptive exposure as a treatment option for disabling pain-related fear. Interoceptive exposure was conceptualised as an extension of the Fear Avoidance Model and a literature review highlighted three important areas: attention/hypervigilance to pain and its threat value, fear-avoidance and the acceptance of pain. A treatment manual was developed based on a literature review and an elaborated single case experimental design methodology was used to determine treatment efficacy.
Seven participants were recruited and four completed treatment which was designed as an ABC sequence: A, baseline; B, education; C interoceptive exposure. Follow up data were obtained at three months post-treatment. Data were obtained from psychometrically standardised assessments, daily measures of the treatment target, and sessional process measures. Participants completed a post-treatment Change Interview in an attempt to evaluate treatment causality in a non-biased way.
There was variation on the standard measures; all of the participants made significant changes on some but not all of the measures. Target measures showed both variation and stability. Process measures showed that all of the participants could engage in the treatment exercises. The participants rated the treatment as being fairly logical however there was differences in expectations about how successful the treatment would be. At the Change Interview, all of the participants described changes which they stated were important and unlikely to occur without therapy.
There is some evidence at different levels that this treatment may be effective. A combination of attention, fear-avoidance and acceptance of pain treatment approach has not been used before and this research indicates promising results for those suffering with chronic pain. However further research is necessary. The procedure could be refined; interoceptive exposure could be explored in more depth and pain and avoidance behaviour could be considered in relation to other goals
Erratum: A global experiment on motivating social distancing during the COVID-19 pandemic (Proceedings of the National Academy of Sciences of the United States of America (2022) 119 (e2111091119) DOI: 10.1073/pnas.2111091119)
No full textThe authors note that 3 coauthors (Chloe DePaola, Martine Jansen, and Neil Levy) have been removed from the author list as they do not meet the requirements for authorship. Additionally, there was a typo in the corresponding author’s name in the list of authors in the SI Appendix. The author’s name should appear as Thuy-vy Nguyen. The corrected author and affiliation list appear in Table S5 in the SI Appendix. The online version has been corrected
Coping and family functioning predict longitudinal psychological adaptation of siblings of childhood cancer patients
No full textOBJECTIVE: To assess associations of coping and family functioning with psychosocial adjustment in siblings of pediatric cancer patients at 1, 6, 12, and 24 months after diagnosis. METHODS: Eighty-three siblings (ages 7-19 years) participated. Effects on anxiety, quality of life, behavioral-emotional problems, and emotional reactions to the illness were investigated. Data-analysis was performed with multilevel mixed modeling. RESULTS: Psychosocial functioning was impaired at 1 month but ameliorated over time. Adjustment problems were associated with high family adaptation and cohesion, older age, and female gender. Lower anxiety, insecurity, loneliness, and illness involvement were related to siblings' ability to remain optimistic. Insecurity and illness involvement were positively related to reliance on the medical specialist and a tendency to seek information about the illness. CONCLUSIONS: Siblings of pediatric cancer patients are most affected by the illness in the first months. Children at risk may be identified according to sibling age and gender and according to long-term family adaptation processes and sibling coping abilities
