In recent years, transition‐metal‐catalyzed C−H activation has become a key strategy in the field of organic synthesis. Rhodium complexes are widely used as catalysts in a variety of C−H ...functionalization reactions because of their high reactivity and selectivity. The availability of a number of rhodium complexes in various oxidation states enables diverse reaction patterns to be obtained. Regioselectivity, an important issue in C−H activation chemistry, can be accomplished by using a directing group to assist the reaction. However, to obtain the target functionalized compounds, it is also necessary to use a directing group that can be easily removed. A wide range of directed C−H functionalization reactions catalyzed by rhodium complexes have been reported to date. In this Review, we discuss Rh‐catalyzed C−H functionalization reactions that are aided by the use of a removable directing group such as phenol, amine, aldehyde, ketones, ester, acid, sulfonic acid, and N‐heteroaromatic derivatives.
Directors cut: The beneficial use of removable directing groups in the Rh‐catalzyed C−H functionalization of organic compounds is discussed in this Review. Various key strategies that are currently used in selective organic synthesis are highlighted.
During the past decades, synthetic organic chemistry discovered that directing group assisted C–H activation is a key tool for the expedient and siteselective construction of C–C bonds. Among the ...various directing group strategies, bidentate directing groups are now recognized as one of the most efficient devices for the selective functionalization of certain positions due to fact that its metal center permits fine, tunable, and reversible coordination. The family of bidentate directing groups permit various types of assistance to be achieved, such as N,N-dentate, N,O-dentate, and N,S-dentate auxiliaries, which are categorized based on the coordination site. In this review, we broadly discuss various C–H bond functionalization reactions for the formation of C–C bonds with the aid of bidentate directing groups.
In this current study, our main focus is on modeling the specific charged compact star SAX J 1808.4-3658 (M = 0.88
M
⊙
, R = 8.9 km) within the framework of
f
(
R
,
T
)
modified gravity theory using ...the metric potentials proposed by Tolman–Kuchowicz (Tolman in Phys Rev 55:364, 1939; Kuchowicz in Acta Phys Pol 33:541, 1968) and the interior spacetime is matched to the exterior Reissner–Nordström line element at the surface of the star. Tolman–Kuchowicz metric potentials provide a singularity-free solution which satisfies the stability criteria. Here we have used the simplified phenomenological MIT bag model equation of state (EoS) to solve the Einstein–Maxwell field equations where the density profile (
ρ
) is related to the radial pressure (
p
r
) as
p
r
(
r
)
=
(
ρ
-
4
B
g
)
/
3
. Furthermore, to derive the values of the unknown constants
a
,
b
,
B
,
C
and the bag constant
B
g
, we match our interior spacetime to the exterior Reissner–Nordström line element at the surface of stellar system. In addition, to check the physical validity and stability of our suggested model we evaluate some important properties, such as effective energy density, effective pressures, radial and transverse sound velocities, relativistic adiabatic index, all energy conditions, compactness factor and surface redshift. It is depicted from our current study that all our derived results lie within the physically accepted regime which shows the viability of our present model in the context of
f
(
R
,
T
)
modified gravity.
The transition towards a modern cleaner energy pathway has been receiving global attention recently. Although nuclear energy has emerged as an alternative cleaner energy source and is receiving ...immense policy attention, however, the role of nuclear energy in the environmental degradation mitigation remains inconclusive in the extant literature. Therefore, this study examines the dynamic linkages between gross domestic product, foreign direct investment inflows, nuclear energy consumption, trade openness, and CO
2
emissions for India within the environmental Kuznets curve framework over the period 1978–2019 through various robust econometric models that takes into consideration the presence of structural break in the data. The present study confirms the existence of an “inverted N shape” environmental Kuznets curve, a phenomenon rarely observed in environmental Kuznets curve literature for India. Besides, the predicted turnaround points of environmental Kuznets curve highlight that India has already reached the positive peak approximately by the year 2015. The empirical findings also confirm the existence of a J-shaped relationship between foreign direct investment inflows and CO
2
emissions, which indicates that India is in the transient phase moving from pollution halo towards pollution heaven with progressive foreign direct investment development. Trade openness is also found to have a beneficial effect on environmental quality implying the trade policy of India encourages green trade activities to safeguard the environment. The empirical results also reveal the beneficial effect of nuclear energy consumption on air quality, thereby suggesting an accelerated adoption of nuclear energy in the Indian energy mix. The results also highlight that nuclear energy adoption in this booming phase can facilitate a “tunnelling effect” for sustainable economic growth for India. Hence, these findings may provide key policy recommendations regarding energy transition and environmentally sustainable economic growth.
•An overview of the strategic evolution in C-H activation chemistry is provided.•The chronological evolution of directed C-H functionalization is discussed.•The history of built-in and removable ...directing groups is outlined.•Distal C-H functionalization with a working hypothesis is presented.
In the field of C–H bond functionalization chemistry, directed C–H bond activation strategies are highly appreciated due to the high efficiency and selectivity of such reactions towards a certain type of C–H bond. Considering extraordinarily rapid progress in directed C–H bond functionalization reactions, we summarize the strategic evolution of directed C–H bond activation chemistry in this review. We feel that this review would be of particular interest to scientists who are interested in progress made in the area of directed C–H bond functionalization, which could stimulate new areas of research regarding this significant topic.
The countermovement jump (CMJ) is commonly used to explore sex differences in neuromuscular function, but previous studies have only reported gross CMJ measures or have partly examined CMJ phase ...characteristics. The purpose of this study was to explore differences in CMJ phase characteristics between male and female athletes by comparing the force-, power-, velocity-, and displacement-time curves throughout the entire CMJ, in addition to gross measures. Fourteen men and fourteen women performed three CMJs on a force platform from which a range of kinetic and kinematic variables were calculated via forward dynamics. Jump height (JH), reactive strength index modified, relative peak concentric power, and eccentric and concentric displacement, velocity, and relative impulse were all greater for men (
= 0.58⁻1.79). Relative force-time curves were similar between sexes, but relative power-, velocity-, and displacement-time curves were greater for men at 90%⁻95% (immediately before and after peak power), 47%⁻54% (start of eccentric phase) and 85%⁻100% (latter half of concentric phase), and 65%⁻87% (bottom of countermovement and initial concentric phase) of normalized jump time, respectively. The CMJ distinguished between sexes, with men demonstrating greater JH through applying a larger concentric impulse and, thus, achieving greater velocity throughout most of the concentric phase, including take-off.
Considerable advances have been made in the area of C−H functionalization in the last few decades. A number of approaches including both directed and nondirected strategies have been developed thus ...far. Among the various C−H functionalizations, C−H borylation is of special interest due to the wide applications of organoboron compounds. In this regard, various transition‐metal‐catalyzed regioselective strategies have been developed. However, the major concern regarding metal‐catalyzed C−H borylation procedures is the requirement of a precious metal as well as the contamination by metal precursors in the desired products, which limit the application of this process in large‐scale synthesis. Therefore, recent trends have involved the use of transition‐metal‐free systems. We summarize recent developments in transition‐metal‐free regioselective C−H borylation. We believe that this Review will help to increase interest in this field and stimulate further progress.
Recent developments in strategies for transition‐metal‐free regioselective C−H borylation are summarized in this Review. Strategies developed to control the regioselectivity of the electrophilic borylation, such as approaches controlled by electronic effects, auxiliaries, and steric factors, are also discussed. EDG=electron donating group, DG=directing group, TM=transition metal.
Organoboron reagents are important synthetic intermediates and have wide applications in synthetic organic chemistry. The selective borylation strategies that are currently in use largely rely on the ...use of transition-metal catalysts. Hence, identifying much milder conditions for transition-metal-free borylation would be highly desirable. We herein present a unified strategy for the selective C–H borylation of electron-deficient benzaldehyde derivatives using a simple metal-free approach, utilizing an imine transient directing group. The strategy covers a wide spectrum of reactions and (i) even highly sterically hindered C–H bonds can be borylated smoothly, (ii) despite the presence of other potential directing groups, the reaction selectively occurs at the o-C–H bond of the benzaldehyde moiety, and (iii) natural products appended to benzaldehyde derivatives can also give the appropriate borylated products. Moreover, the efficacy of the protocol was confirmed by the fact that the reaction proceeds even in the presence of a series of external impurities.
Hybrid star within f(G) gravity Rej, Pramit
Chinese journal of physics (Taipei),
June 2024, 2024-06-00, Letnik:
89
Journal Article
Recenzirano
The purpose of this work is to investigate some interesting features of a static anisotropic relativistic stellar object composed of two different types of fluid distributions typically termed as ...quark matter (QM) and ordinary baryonic matter (OBM) together with Krori–Barua type (KB) ansatz in the regime of modified f(G) gravity, where G being the Gauss–Bonnet invariant term. In order to explain the correlation between pressure and matter density for the quark matter distribution within the compact object, we have taken into consideration the well-known MIT bag equation of state (EoS) whereas there is a simple linear correlation between pressure and matter density for ordinary baryonic matter. Furthermore, using graphical representations for varying parameters, the physical credibility of our obtained solutions has been intensively examined by regularity checking of the metric coefficients and matter variables, energy conditions, mass function, and causality conditions. For these analyses, we consider a particular compact stellar candidate 4U 1538-52. Finally, we found that the resulting outcome depicts the viability of the considered hybrid stellar model.
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•A detailed analysis of a Hybrid star in f(G) gravity has been performed•This model has been built using two different EoS and the Krori–Barua ansatz•We have examined every facet of its physical characteristics•The stability, viability, and astronomical prerequisites have all been established•In astrophysical context, this model may be more useful in making a contribution
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