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Abstract The choice of vertical mixing scheme in ocean models plays an important role in modeling the surface and subsurface circulation and the vertical structure. This work performs a comparative study between K‐profile parametrization (KPP) and k‐ϵ mixing schemes for a regional domain in the Bay of Bengal (BoB) using the Modular Ocean Model version 5 (MOM5). It is observed that sea surface temperature (SST) and the mixed layer depth (MLD) show significant improvement with the k‐ϵ mixing scheme. Energetic analysis shows that changes in the viscous dissipation and turbulent buoyancy flux are the primary reason for improvement with k‐ϵ. The overestimation of viscous dissipation in the KPP scheme is corrected by k‐ϵ, resulting in a deeper mixed layer closer to observations. The tendency of buoyancy flux to retain stability in the water column also results in a better representation of SST in k‐ϵ. Overall, we conclude that the k‐ϵ mixing scheme works better for the BoB region.

The variability of predicted variables at daily to seasonal scales in coupled models is primarily governed by surface boundary conditions between the ocean and atmosphere, namely, sea surface temperature (SST), turbulent heat, and momentum fluxes. Although efforts have been made to achieve good accuracy in surface fluxes and SST in observation and reanalysis products, less attention has been paid toward achieving improved accuracy in coupled model simulations. Improper diurnal phase and amplitude in intra-daily SST and precipitation are well-known problems in most global coupled general circulation models, including the Climate Forecast System v2 (CFSv2) model. The present study attempts to improve the representation of ocean-atmosphere surface boundary conditions in CFSv2, primarily used for India's operational forecasts at different temporal/spatial scales. In this direction, the diurnal warm layer and cool skin temperature correction scheme are implemented along with the surface flux parameterization scheme following Coupled Ocean-Atmosphere Response Experiment (COARE) v 3.0. The coupled model re-forecasts with a revised flux scheme showed better characteristics in various ocean-atmosphere parameters and processes at diurnal and seasonal time scales. At the diurnal scale, the phase and amplitude of intra-daily SST and mixed layer depth variabilities are improved over most tropical oceans. Improved diurnal SSTs helped in enhancing the diurnal range of precipitation by triggering stronger intra-daily convection. The corrected diurnal ocean-atmospheric boundary state translated into a reduction in seasonal mean dry bias over Indian landmass and the wet bias over tropical oceans. Better simulation of non-linearity associated with El Niño–Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), ENSO-Indian Summer Monsoon Rainfall (ISMR), and IOD-ISMR relation is among the most critical improvements achieved by revising the turbulent flux parameterization. The revised flux scheme showed enhanced prediction skills for tropical SST indices and ISMR.

We conduct experiments on the convective dynamics of a rotating fluid in a novel configuration, which comprises of a cylindrical annulus with peripheral spot heating at the bottom on the outer edge and uniform cooling on the inner edge. This system naturally provides an additional vertical gradient on the outer edge of the annulus, along with a radial gradient, thereby mimicking the thermal gradient patterns encountered in a real atmosphere. Localized heating is carried out at the bottom using a thin annular metal strip of thickness, h=5 mm. Water is used as the working fluid. Once the system reaches a statistically steady state, localized temperature measurements are carried out at various radial locations along the vertical fluid height. We measure time series of the temperature at several locations and visualize the flow structures over a range of Taylor number Ta (spanning 6.5 × 108- 2.7 × 109) and Rayleigh number Ra (spanning 2.2 × 108- 6.2 × 108). Temperature time series data at different heights, z, near the outer edge, along with two point correlations of temperature data indicate that, in the presence of rotation, columnar convective plumes (CCP) exist above the heating zone that aid in the vertical transport of heat. Qualitative flow field and temperature measurements in the bulk fluid also indicate the existence of baroclinic waves, which aid in the horizontal transport of cold and hot fluids between the annuli. The two point temperature correlations show that these waves break into eddies as the value of Ta increases. Overall, it is speculated that heat transport in this new configuration is governed by the co-existence and interplay of convective plumes and baroclinic waves/eddies, which closely simulates the dynamics of geophysical motions. It is found that the heat transport near the outer edge and in the fluid bulk is a strong function of Ra and Ta. For the highest value of Ra=6.2 × 108, the radial heat transport was most effective at Ta=0. However, at lower values of Ra, the radial heat transport in the outer and bulk regions was highest at Ta=1.5 × 109. These results indicate that an optimum value of Ra and Ta exists at which the convection driven radial heat transport is most energetic through the interaction of CCP and baroclinic waves/eddies.

In the title compound, C24H23FN2O3, the cyclohexene ring adopts a screw-boat conformation. The fluorobenzene ring attached to the cyclohexene ring and the phenyl ring attached to the indazole moiety are inclined to one another by 57.77 (13)°. In the crystal, molecules are linked by O—H...N and C—H...O hydrogen bonds, forming chains with C(5) and C(10) graph-set motifs. There are also C—H...π interactions present. The isopropoxycarbonyl group undergoes considerable thermal motion.

In the title compound, C17H19NO8 [systematic name = dimethyl 4-hydroxy-4-methyl-2-(3-nitrophenyl)-6-oxocyclohexane-1,3-dicarboxylate], the cyclohexanone ring exhibits a chair conformation. The methoxycarbonyl groups are oriented in opposite directions with respect to the cyclohexanone ring. In the crystal, O—H...O hydrogen bonds links the molecules into chains running parallel to the a axis. These chains are connected by weak C—H...O hydrogen bonds, forming sheets parallel to the ab plane.

Described herein is a tandem reaction involving a copper chloride‐catalyzed cross‐coupling and an allene‐mediated cyclization of substituted ethynylimidazo[2,1‐b]thiazoles with aromatic N‐tosylhydrazones, producing naphtho[1′,2′4,5]imidazo [2,1‐b]thiazoles in very good yields. This protocol offers the advantages of one‐pot conversion from stable and readily available substrates as well as good functional group compatibility to prepare polycyclic N‐fused heteroaromatic systems. Moreover, the new compounds exhibited promising antitubercular activity. [ABSTRACT FROM AUTHOR]

A novel gold (I)‐catalyzed synthetic strategy has been achieved for an efficient construction of indenylidene derivatives from substituted 1,6‐diynes. This reaction describes the unique reactivity of gold catalysis in facilitating the intramolecular [3,3]‐sigmatropic rearrangement, 5‐exo dig cyclization followed by 1,5‐migration of acryl group, resulting in the formation of substituted indenylidenes. Various substituted indenylidenes were successfully synthesized with up to 92 % yields. In this protocol, two new C−C bonds were sequentially formed atom economically in one pot. [ABSTRACT FROM AUTHOR]

Rational design of unnatural amino acid building blocks capable of stabilizing predictable secondary structures similar to protein fragments is pivotal for foldamer chemistry/catalysis. Here, we introduce novel β‐amino acid building blocks: [1S,2R,4R]exoCDA and [1S,2S,4R]endoCDA, derived from the abundantly available R(+)‐camphor, which is traditionally known for its medicinal value. Further, we demonstrate that the homooligomers of exoCDA adopt 6‐strand conformation, which switches to a robust 10/12‐helix simply by inserting flexible β‐hGly spacer at alternate positions (1 : 1 β‐hGly/exoCDA heterooligomers), as evident by DFT‐calculations, solution‐state NMR spectroscopy and X‐ray crystallography. To the best of our knowledge, this is the first example of crystalline‐state structure of left‐handed 10/12‐mixed helix, that is free from the conventional approach of employing β‐amino acids of either alternate chirality or alternate β2/β3 substitutions, to access the 10/12‐helix. The results also show that the homooligomers of heterochiral exoCDA don′t adopt helical fold, instead exhibit banana‐shaped strands, whereas the homodimers of the other diastereomer endoCDA, nucleate 8‐membered turns. Furthermore, the homo‐exoCDA and hetero‐[β‐hGly‐exoCDA] oligomers are found to exhibit self‐association properties with distinct morphological features. Overall, the results offer new possibilties of constructing discrete stable secondary and tertiary structures based on CDAs, which can accommodate flexible residues with desired side‐chain substitutions. [ABSTRACT FROM AUTHOR]

Herein, we demonstrated a visible light mediated tandem oxidation–organo catalyzed C−S bond functionalization protocol for the cleavage of aromatic C−S bond. The investigation encompassed the functionalization of C−S bonds within sulfones, sulfoxides, and aliphatic sulfide derivatives. However, the process of functionalizing the C−S bond in aromatic sulfides remains uncertain. The presented protocol demonstrates the C−S bond functionalization on benzo[b]benzo[4,5]thieno[2,3‐d]thiophene derivative and amines including primary and secondary amines as well. A radical mediated mechanism was proposed for the tandem oxidation–organocatalyzed C−S bond functionalization protocol. [ABSTRACT FROM AUTHOR]

Here we report a metal‐free direct C−H trifluoromethylation of the imidazothiazoles 7(a–ad) using sodium triflouromethanesulfinate (Langlois' reagent) and tert‐butyl hydroperoxide (TBHP) as an oxidant. The control studies show that the protocol follows the radical reaction pathway and provides excellent yields of trifluoromethylated products 9(a–ad) with broad substrate scope and regioselective operation. Moreover, the newly synthesized compounds exhibit promising antimycobacterial activity. [ABSTRACT FROM AUTHOR]

An innovative series of N‐substituted piperazine‐linked imidazothiazole derivatives 7(a–x) were synthesized, and their antitubercular effectiveness was evaluated. A three‐step reaction sequence involving the condensation of 1,3‐dichloroacetone and thiourea, coupling with substituted piperazines to give the intermediates 5(a–d) and cyclization with substituted α‐bromoacetophenones produced the desired imidazothiazole derivatives 7(a–x) in excellent yields. In vitro screening of new derivatives against Mycobacterium tuberculosis H37Rv resulted in 7k (minimum inhibitory concentration [MIC]: 0.78 μg/mL) and 7g and 7h (MIC: 1.56 μg/mL) as potent hit compounds. Further, the docking studies of the promising compounds 7k, 7g, and 7h revealed that the best molecular interactions are with the DprE1 in complex with sulfonyl PBTZ of M. tuberculosis as the target protein (PDB ID: 6G83). [ABSTRACT FROM AUTHOR]

A one‐pot synthesis of diversely substituted polycyclic fused 1,7‐naphthyridines has been achieved via a silver‐catalyzed domino reaction. In this protocol, ortho‐alkynyl quinolines/pyridines were reacted smoothly with substituted anthranilic acid/ anthranilamide and provided fused 1,7‐naphthyridines scaffolds in excellent yields and good functional group tolerance under mild conditions. This protocol is further applicable for gram scale synthesis. In this methodology, we proposed the mechanism with the help of control experiments. [ABSTRACT FROM AUTHOR]

Cascade aza‐Piancatelli reaction and [3+3]/[4+2] cycloaddition reactions are carried out using the ideality principles of pot, atom, and step economy (PASE) synthesis. The reaction resulted in generation of octahydro‐4H‐cyclopenta[b]pyridin‐6‐one scaffolds. Moreover, octahydro‐5,7a‐epoxycyclopenta[cd]isoindol‐4‐one frameworks of gracilamine alkaloid and a novel decahydro‐1H‐dicyclopenta[cd,hi]isoindol‐6‐one were also realized in good yields with excellent regio‐ and diastereo‐selectivities. [ABSTRACT FROM AUTHOR]

Silver‐catalyzed N‐aryl‐1H‐pyrazolyl substituted benzenesulfonamide derivatives were obtained regioselectively from ynamides and pyrazoles. In this intermolecular organic transformation, several substituted benzenesulfonamides were obtained in good to excellent yields by forming a new C−N bond under mild reaction conditions. [ABSTRACT FROM AUTHOR]

Environmentally amiable biogenic strategy for in‐situ one‐step synthesis of Pd‐NPs decorated on carbon nanotubes (CNTs) and its synthetic utility for C−H activation of benzamides to access isoquinolones has been reported for the first time. The phytochemicals present in Gliricidia sepium leaves extract was found to be serve as a reducing agent to reduce Pd (II) to Pd (0) and subsequently acts as a stabilizing agent. The formation of Pd@CNTs was confirmed by P‐XRD, FE‐SEM, EDX and ICP‐OES analysis technique with active Pd content 42.82 % w/w. In addition, DFT study of phytochemicals found in Gliricidia sepium leaves extract were conducted. The catalytic activity was showcased for the cost‐effective, step and atom economic synthesis of isoquinolones via C−H and N−H bond activation without the aid of external ligands. A series of isoquinolone derivatives were synthesized in good to excellent yields under air as a sole oxidant. In addition, catalyst recyclability and mechanistic experiments were deliberated. The Pd@CNTs unveiled superior catalytic activity and high durability towards hydrogen evolution reaction in acidic media. The Pd@CNTs attains the current density of 10 mA/cm2 at an over potential of 127 mV with a small Tafel slope of 41 mV/dec. [ABSTRACT FROM AUTHOR]