Annulative Coupling of Sulfoxonium Ylides with Aldehydes and Naphthols or Coumarins: Easy Access to Fused Dihydrofurans.

We present a novel, metal- and additive-free method for the robust synthesis of dihydrofuran-fused naphthalenes and coumarins. This approach utilizes the annulative coupling of sulfoxonium ylides with aldehydes, naphthols, or coumarins at ambient temperature. The method exhibits broad substrate compatibility, accommodating various functional groups on sulfoxonium ylides and naphthol or coumarin derivatives and resulting in good to high yields of the desired products.

Annulative coupling of sulfoxonium ylides with 2-amino(thio)phenols: easy access to 2-acyl benzox(thio)azoles.

A novel method for synthesizing 2-acyl benzothiazoles and benzoxazole derivatives has been developed the annulative coupling of sulfoxonium ylides with 2-aminobenzenethiol and 2-aminophenol derivatives, respectively. This metal-free, one-pot protocol employs elemental sulfur as a mediator to efficiently construct C-N, C-S, or C-O bonds and demonstrates a broad range of functional group compatibility. The potential utility of this approach is further demonstrated through large-scale reactions and the synthesis of some bioactive compounds.

Mn(I)-Catalyzed Site-Selective C-H Activation: Unlocking Access to 3-Arylated Succinimides from 2-Arylpyridines and Maleimides.

An efficient and cost-effective Mn(I)-catalyzed site-selective C-H activation of 2-arylpyridines with maleimides has been described. This approach facilitates the synthesis of 3-arylated succinimide derivatives with high site selectivity, chemoselectivity, catalytic efficiency, and outstanding tolerance to numerous functional groups. The practicality of this approach is further evidenced by its successful application in large-scale reactions and the conversion of the synthesized succinimide derivatives into other valuable compounds.

I-Promoted Chemoselective Annulative Coupling of 2-Aminobenzamides with Sulfoxonium Ylides: Easy Access to Quinazolinones.

A flexible and metal-free synthetic approach for synthesizing 2-benzoyl quinazolinones and 2-aryl quinazolinones via molecular iodine-mediated annulative coupling of sulfoxonium ylides with 2-aminobenzamides has been disclosed. The method demonstrates remarkable chemoselectivity and efficiency, leading to high yields of 2-benzoyl quinazolinones and 2-aryl quinazolinones under optimized conditions. The broad substrate scope, scalability, and practical utility were highlighted through diverse applications, including gram-scale reactions and the synthesis of biologically significant compounds such as tryptanthrin and the chemo/biosensor derivative.

Annulative coupling of α-substituted acrylic acids and sulfoxonium ylides: easy access to bioactive γ-butyrolactones.

We present a straightforward, catalyst- and additive-free method for synthesizing keto γ-butyrolactones using readily available β-keto sulfoxonium ylides and acrylic acids. This robust approach demonstrates exceptional compatibility with various functional groups on β-keto sulfoxonium ylides and α-substituted acrylic acids, resulting in good to high yields of the anticipated products. Moreover, the practicality of this approach was validated through large-scale reactions and the successful conversion of some synthesized derivatives into bioactive natural products, including L-factor, muricatacin, and cytosporanone A.

I-Mediated Site-Selective C-H Functionalization: Access to -Amino-Substituted Unsymmetrical Benzils and Quinoxalines from Sulfoxonium Ylides.

An I-mediated approach for selective C-H functionalization of unprotected aniline derivatives for synthesizing benzils and quinoxaline derivatives from sulfoxonium ylides has been described. Aniline derivatives and sulfoxonium ylides ornamented with different functional groups showed good compatibility. They afforded the corresponding products with moderate to high yields via a mild and simple procedure.

Straightforward access to α-carbonyloxy esters and β-keto thioethers from aryldiazoacetates.

A metal- and additive-free approach has been described for synthesizing α-carbonyloxy esters and β-keto thioethers from readily available aryldiazoacetates with carboxylic acids and thiol derivatives, respectively. α-Carbonyloxy esters and β-keto thioether derivatives were synthesized in good to high yields from aryldiazoacetates, carboxylic acids, and thiol derivatives decorated with various functional groups. Finally, the potential of the new approach is demonstrated through its application in gram-scale reactions and the synthesis of a few bioactive molecules.

Proline-catalyzed synthesis of α-substituted ()-α,β-unsaturated aldehydes from epoxides.

A novel, simple and metal-free tandem approach for synthesizing α-substituted ()-α,β-unsaturated aldehyde derivatives through acid-catalyzed epoxide rearrangement and organocatalyzed aldol condensation processes has been described. This transformation has a broad substrate scope under mild conditions, including epoxides and aldehydes containing diverse functional groups, resulting in moderate to high yields of the desired products. Eventually, large-scale reactions and the synthesis of some bioactive molecules are used to demonstrate the potential applicability of the developed method.

Metal-free synthesis of α-acyloxy ketones from carboxylic acids and sulfoxonium ylides.

A straightforward, catalyst- and additive-free approach has been described for synthesizing α-acyloxy ketones from β-ketosulfoxonium ylides and carboxylic acids. Moderate to high yields of α-acyloxy ketones were produced using sulfoxonium ylides and carboxylic acids adorned with various functional groups. Eventually, the applicability of this approach has been shown a large-scale reaction and transforming the synthesized α-acyloxy ketone derivatives into other valuable compounds.

Straightforward access to α-thiocyanoketones and thiazoles from sulfoxonium ylides.

Efficient, versatile, and metal-free strategies for synthesizing α-thiocyanoketones and thiazoles from β-ketosulfoxonium ylides and ammonium thiocyanate have been described. Due to its simplicity, benign reaction conditions, excellent chemoselectivity, and high yield, this method represents a unique approach for divergent synthesis. Finally, the potential value of the developed methods is demonstrated large-scale reactions and synthesis of Fanetizole, an anti-inflammatory drug.

Elemental Sulfur-Mediated Synthesis of Quinoxalines from Sulfoxonium Ylides.

A novel straightforward and catalyst-free approach for synthesizing quinoxaline derivatives from sulfoxonium ylides and -phenylenediamines mediated by elemental sulfur has been described. Due to the simple and mild reaction conditions, the sulfoxonium ylides and -phenylenediamines decorated with different functional groups furnished moderate to high yields of quinoxaline derivatives and were well tolerated. Finally, large-scale reactions, the synthesis of pyrazines, and some bioactive compounds are used to illustrate the potential utility of the developed approach.

Multicomponent Reaction of CS, Amines, and Sulfoxonium Ylides in Water: Straightforward Access to β-Keto Dithiocarbamates, Thiazolidine-2-thiones, and Thiazole-2-thiones.

Simple, versatile, and catalyst-free synthetic methods for β-keto dithiocarbamates, thiazolidine-2-thiones, and thiazole-2-thiones via the multicomponent reaction of CS, amines, and sulfoxonium ylides have been described. The β-keto sulfoxonium ylides furnished β-keto dithiocarbamates in the presence of CS and secondary amines, whereas primary amines afforded thiazolidine-2-thiones or thiazole-2-thiones after dehydration in an acidic environment. With simple procedures, the reaction has a wide substrate scope and excellent functional group tolerance.

Synthesis of α-Carbonyl-α'-amide Sulfoxonium Ylides from Isocyanates with Complete Atom Economy.

An efficient catalyst- and additive-free facile synthesis of α-carbonyl-α'-amide sulfoxonium ylides from isocyanates and β-ketosulfoxonium ylides with complete atom economy has been described. The β-ketosulfoxonium ylides and isocyanates adorned with various functional groups were well-tolerated and afforded moderate to high yields of the α-carbonyl-α'-amide sulfoxonium ylide derivatives. Finally, using large-scale reactions and converting the synthesized ylides into other valuable compounds, we demonstrated the practicality of this synthetic method.

Organocatalyzed epoxidation in the total synthesis of (-)--, (+)-- and (+)--disparlures.

A simple, flexible and efficient organocatalyzed synthetic approach for the synthesis of (-)--, (+)-- and (+)--disparlures has been described. The pivotal reaction sequence comprises organocatalyzed asymmetric Jørgensen epoxidation, Wittig olefination, migration of epoxide and Mitsunobu inversion reaction. Excellent enantiomeric purity (≥99%) was achieved during the synthesis of disparlure enantiomers by the Jørgensen epoxidation key step.

Catalyst- and additive-free syntheses of rhodanine and -alkyl dithiocarbamate derivatives from sulfoxonium ylides.

An efficient catalyst- and additive-free facile access to rhodanine and -alkyl dithiocarbamate derivatives multi-component reaction of amines, CS and α-ester sulfoxonium ylides in methanol has been described. The new synthetic methods offer excellent synthetic prospects for several functionalized rhodanines and -alkyl dithiocarbamates with simple operational procedures.

Metal-Free Syntheses of α-Ketothioamide and α-Ketoamide Derivatives from Sulfoxonium Ylides.

An efficient base, additive and metal-free synthetic methods for α-ketothioamide and α-ketoamide derivatives from readily available sulfoxonium ylides have been described. Sulfoxonium ylides with primary or secondary amines afforded α-ketothioamides in the presence of elemental sulfur, whereas α-ketoamides were produced when I and TBHP were present. The reaction proceeded well at room temperature and generated the corresponding molecules in good to excellent yields.

Organocatalyzed Protecting-Group-Free Total Synthesis of ()- and ()-Reboxetine, an Antidepressant Drug.

An efficient, simple, and concise organocatalyzed protecting-group-free synthetic approach to the stereoisomers of the antidepressant drug reboxetine and its implementation toward the asymmetric synthesis of ()-reboxetine and ()-reboxetine from commercially available -cinnamaldehyde are described. The synthesis features organocatalytic Jørgensen asymmetric epoxidation, epoxide migration, and Mitsunobu inversion as key steps.

Synthesis of rhein and diacerein: a chemoenzymatic approach using anthrol reductase of .

Herein, we report two methods for the synthesis of the osteoarthritis drug rhein and its prodrug diacerein using a chemoenzymatic approach. The strategy relies on the use of an NADPH-dependent anthrol reductase of (ARti-2), which mediates the regioselective and reductive deoxygenation of anthraquinones. The work further implies similar biosynthesis of rhein in fungi.

Lead Isotope Evidence for Enhanced Anthropogenic Particle Transport to the Himalayas during Summer Months.

The Indo-Gangetic Plain (IGP) is one of the most highly polluted regions of the world, yet the temporal pattern of transport of anthropogenic aerosols from this region to the Himalayas is poorly constrained. On the basis of the seasonal variation of planetary boundary layer heights, air mass back trajectory analysis, and year-long time-series data for Pb/Pb, Pb/Pb, Pb/Pb, and Nd/Nd from aerosols collected over a high-altitude station, we demonstrate that anthropogenic Pb transport to the glacierized catchment has a seasonal pattern. The Pb isotope data reveal that during winter, the thinned boundary layer traps up to 10 ± 7% more coal-derived Pb in the IGP.

Biomass-Derived Provenance Dominates Glacial Surface Organic Carbon in the Western Himalaya.

The origin, transport pathway, and spatial variability of total organic carbon (OC) in the western Himalayan glaciers are poorly understood compared to those of black carbon (BC) and dust, but it is critically important to evaluate the climatic role of OC in the region. By applying the distribution of OC activation energy; C activity; and radiogenic isotopes of Pb/Pb, Pb/Pb, and Pb/Pb in glacial debris and atmospheric particulate matter (PM size fraction), we demonstrate that 98.3 ± 1.

An efficient enantioselective approach to multifunctionalized γ-butyrolactone: concise synthesis of (+)-nephrosteranic acid.

A short, efficient and novel approach for multifunctionalized γ-butyrolactone paraconic acids and its application to the total synthesis of (+)-nephrosteranic acid from readily available PMB ()-glycidyl ether as a starting material are described. Key transformations include asymmetric Michael addition catalyzed by chiral diphenylprolinol silyl ether and stereoselective α-methylation.

Hetero-Polysaccharides Secreted from Exhibit Immunomodulatory Activity Against Peripheral Blood Mononuclear Cells and RAW 264.7 Macrophages.

Several species of microalgae have been known to produce exopolysaccharides (EPS) with potential immune activity. In the present investigation, ethyl acetate fraction of crude EPS secreted by was explored for immunomodulatory activity against peripheral blood mononuclear cells (PBMC) and RAW 264.7 macrophages.

Rv1273c, an ABC transporter of Mycobacterium tuberculosis promotes mycobacterial intracellular survival within macrophages via modulating the host cell immune response.

Mycobacterium proteins, especially cell wall associated proteins, interact with host macrophage to regulate the functions and cytokine production. So, identification and characterization of such proteins is essential for understanding tuberculosis pathogenesis. The role of the ABC transporter proteins in the pathophysiology and virulence of Mycobacterium tuberculosis is not clearly understood.

An AcOH-mediated metal free approach towards the synthesis of bis-carbolines and imidazopyridoindole derivatives and assessment of their photophysical properties.

An AcOH-mediated concise, atom-economical and environmentally sustainable tandem strategy has been formulated to access highly fluorescent (ΦF up to 40%) N-fused bis-carbolines, imidazopyrido[3,4-b]indoles and imidazo[1,5-a]pyridines via the formation of three C-N bonds in a single operation. The multicomponent character of the reaction, easy to execute reaction conditions, simple purification procedure and excellent light emitting properties of the product afforded thereof provide a huge scope.

Declining pre-monsoon dust loading over South Asia: Signature of a changing regional climate.

Desert dust over the Indian region during pre-monsoon season is known to strengthen monsoon circulation, by modulating rainfall through the elevated heat pump (EHP) mechanism. In this context, an insight into long term trends of dust loading over this region is of significant importance in understanding monsoon variability. In this study, using long term (2000 to 2015) aerosol measurements from multiple satellites, ground stations and model based reanalysis, we show that dust loading in the atmosphere has decreased by 10 to 20% during the pre-monsoon season with respect to start of this century.