Multi-Color Luminescence Transition of Upconversion Nanocrystals via Crystal Phase Control with SiO2 for High Temperature Thermal Labels

Upconversion nanocrystals (UCNs)-embedded microarchitectures with luminescence color transition capability and enhanced luminescence intensity under extreme conditions are suitable for developing a robust labeling system in a high-temperature thermal industrial process. However, most UCNs based labeling systems are limited by the loss of luminescence owing to the destruction of the crystalline phase or by a predetermined luminescence color without color transition capability. Herein, an unusual crystal phase transition of UCNs to a hexagonal apatite phase in the presence of SiO2 nanoparticles is reported with the enhancements of 130-fold green luminescence and 52-fold luminance as compared to that of the SiO2-free counterpart. By rationally combining this strategy with an additive color mixing method using a mask-less flow lithography technique, single to multiple luminescence color transition, scalable labeling systems with hidden letters-, and multi-luminescence colored microparticles are demonstrated for a UCNs luminescence color change-based high temperature labeling system

The Immediate and Sustained Positive Effects of Meditation on Resilience Are Mediated by Changes in the Resting Brain

While recent studies have explored the maintenance of the effect of meditation on stress resilience, the underlying neural mechanisms have not yet been investigated. The present study conducted a highly controlled residential study of a 4-day meditation intervention to investigate the brain functional changes and long-term effects of meditation on mindfulness and resilience. Thirty participants in meditation practice and 17 participants in a relaxation retreat (control group) underwent magnetic resonance imaging scans at baseline and post-intervention and completed the Cognitive and Affective Mindfulness Scale (CAMS) and Resilience Quotient Test (RQT) at baseline, post-intervention, and the 3-month follow-up. All participants showed increased CAMS and RQT scores post-intervention, but only the meditation group sustained the enhancement after 3 months. Resting-state functional connectivity (rsFC) between the left rostral anterior cingulate cortex (rACC) and the dorsomedial prefrontal cortex (dmPFC), precuneus, and angular gyrus was significantly increased post-intervention in the meditation group compared with the relaxation group. The changes in rACC-dmPFC rsFC mediated the relationship between the changes in the CAMS and RQT scores and correlated with the changes in the RQT score both immediately and at 3 months post-intervention. Our findings suggest that increased rACC-dmPFC rsFC via meditation causes an immediate enhancement in resilience that is sustained. Since resilience is known to be associated with the preventative effect of various psychiatric disorders, the improvement in stress-related neural mechanisms may be beneficial to individuals at high clinical risk

Rh(III) and Ru(II)-catalyzed site-selective C-H alkynylation of quinolones

C2- and C5-alkynylated quinolone scaffolds are core structures of numerous biologically active molecules. Utilizing TIPS-EBX as an alkynylating agent, we have developed an efficient and site-selective C5 alkynylation of 4-quinolones that is directed by the weakly coordinating carbonyl group. In addition, Ru(II) catalyzed C2-selective alkynylation was successfully realized via N-pyrimidyl group-directed cross-couplings to access valuable C2-alkynylated 4-quinolones. This strategy provides direct access to the C2 or C5 alkynylated 4-quinolones. Furthermore, the reaction was applied to isoquinolones for C3-selective alkynylation. © 2015 American Chemical Society145441sciescopu

RhI-catalyzed site-selective decarbonylative alkenylation and arylation of quinolones under chelation assistance

An efficient catalytic system for the C-2 selective C-H functionalization of 4-quinolones was developed by using a decarbonylative coupling strategy. The installation of an N-pyrimidyl group on the quinolone nitrogen atom redirected the coordination between the catalyst and the carbonyl group to promote direct C-H functionalization at the 2-position of 4-quinolones. In addition, the present protocol was successfully applied to the C-3 selective installation of a variety of aryl and vinyl groups on an isoquinolone scaffold. The C-2 selective alkenylation and arylation reactions of 4-quinolones were achieved by using a RhI-catalyzed decarbonylative coupling strategy to afford valuable C-2 functionalized 4-quinolones. The present method was compatible with a broad scope of substrates and applied to the C-3 selective functionalization of an isoquinolone scaffold. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim1671sciescopu

Site-Selective C-H Bond Functionalization of Chromones and Coumarins

Chromones and coumarins are privileged scaffolds that are widely distributed in natural products, synthetic building blocks, pharmaceutical agents, and functional materials. Chromones and coumarins have chemically distinct C-H bonds that can be converted into valuable functional groups for the purpose of constructing compounds with diverse pharmacological profiles. Recent advances in the development of methods and an understanding of the innate electronic properties of chromones and coumarins have led to approaches that provide high levels of site-selectivity. This focus review highlights recent innovative strategies for the efficient modification of these structural frameworks through site-selective C-H bond functionalizations ⓒ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinhei

Regiodivergent Ring-Opening Cross-Coupling of Vinyl Aziridines with Phosphorus Nucleophiles: Access to Phosphorus-Containing Amino Acid Derivatives

Catalytic ring-opening phosphonation and phosphatation of vinyl aziridines have been developed in a regiodivergent fashion, giving linear and branched products. Generation of P-centered radicals enables S(N)2'-type ring-opening reactions of vinyl aziridines to afford delta-amino alkylphosphorus products at room temperature. On the other hand, in situ generated phosphate anions via the Ag-catalyzed aerobic oxidation of phosphonyl reactants underwent S(N)2 reaction to provide branched phosphorus-containing amine products. Furthermore, this divergent methodology serves as a powerful tool for the stereospecific synthesis of phosphorus-containing amino acid derivatives © 2018 American Chemical Societ

Rhodium-Catalyzed Direct C-H Phosphorylation of (Hetero)arenes Suitable for Late-Stage Functionalization

Efficient rhodium-catalyzed direct C-H phosphorylation of (hetero)arenes was developed. Various directing groups and a wide range of substrates, including heterocycles, can be utilized in this C-H phosphorylation process, allowing for the rapid installation of the phosphonate group into medicinally and biologically important privileged scaffolds. The efficient and straightforward method could serve as a new tool to streamline late-stage C-H functionalization for preparing aryl phosphonates, which are important structural motif in synthetic and medicinal chemistry (c) 2016 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim113141sciescopu

Visible-Light Excitation of Quinolinone-Containing Substrates Enables Divergent Radical Cyclizations

© 2019 American Chemical Society. Reported herein is the photochemical activity of quinolinone-containing substrates that directly reach an excited state upon light absorption to trigger radical-based bond-forming processes. The presented transformations allow divergent construction of valuable dihydro- or tetrahydrophenanthridin-6(5H)-ones through the generation of S- or P-centered radicals, subsequent radical addition, cyclization, and a hydrogen atom transfer/electron transfer sequence. This strategy demonstrates the potential generality of quinolinone-tethered substrates to directly participate in the photoexcitation for the development of useful synthetic method

Synthesis of heterocyclic-fused benzopyrans via the Pd(II)-catalyzed C–H alkenylation/C–O cyclization of flavones and coumarins

An efficient and practical method for effecting a tandem C-H alkenylation/C-O cyclization has been achieved via the C-H functionalization of flavone derivatives. The synthetic utility of the one-pot sequence was demonstrated by obtaining convenient access to coumarin-annelated benzopyrans. The reaction scope for the transformation was found to be fairly broad, affording good yields of a wide range of flavone-or coumarin-fused benzopyran motifs, which are privileged structures in many biologically active compounds.113131sciescopu

Mechanism of Rh-Catalyzed Oxidative Cyclizations: Closed versus Open Shell Pathways

A conceptual theory for analyzing and understanding oxidative addition reactions that form the cornerstone of many transition metal mediated catalytic cycles that activate C-C and C-H bonds, for example, was developed. The cleavage of the σ- or φ-bond in the organic substrate can be envisioned to follow a closed or an open shell formalism, which is matched by a corresponding electronic structure at the metal center of the catalyst. Whereas the assignment of one or the other mechanistic scenario appears formal and equivalent at first sight, they should be recognized as different classes of reactions, because they lead to different reaction optimization and control strategies.The closed-shell mechanism involves heterolytic bond cleavages, which give rise to highly localized charges to form at the transition state. In the open-shell pathway, bonds are broken homolytically avoiding localized charges to accumulate on molecular fragments at the transition states. As a result, functional groups with inductive effects may exert a substantial influence on the energies of the intermediate and transition states, whereas no such effect is expected if the mechanism proceeds through the open-shell mechanism. If these functional groups are placed in a way that opens an electronic communication pathway to the molecular sites where charges accumulate, for example, using hyperconjugation, electron donating groups may stabilize a positive charge at that site.An instructive example is discussed, where this stereoelectronic effect allowed for rendering the oxidative addition diastereoselective. No such control is possible, however, when the open-shell reaction pathway is followed, because the inductive effects of functional groups have little to no effect on the stabilities of radical-like substrate states that are encountered when the bonds are broken in a homolytic fashion. Whether the closed-shell or open-shell mechanism for oxidative addition is followed is determined by the ordering of the d-orbital dominated frontier orbitals. If the highest occupied molecular orbital (HOMO) is oriented in space in such a way that will give the organic substrate easy access to the valence electron pair, the closed-shell mechanism can be followed. If the shape and orientation of the HOMO is not appropriate, however, an alternative pathway involving singlet excited states of the metal that will invoke the matching radicaloid cleavage of the organic substrate will dominate the oxidative addition. This novel paradigm for formally analyzing and understanding oxidative additions provides a new way of systematically understanding and planning catalytic reactions, as demonstrated by the in silico design of room-temperature Pauson-Khand reactions. © 2016 American Chemical Society111