Catalyst-Controlled C-H Allylation and Annulation of 2-Aryl Quinazolinones with 2-Methylidene Cyclic Carbonate.

The site-selective modification of quinazolinone as a privileged bicyclic N-heterocycle is an attractive topic in medicinal chemistry and material science. We herein report the ruthenium(II)-catalyzed C-H allylation of 2-aryl quinazolinones with 2-methylidene cyclic carbonate. In addition, tandem C-H allylation and annulation are achieved under rhodium(III) catalysis, resulting in the formation of tetracyclic quinazolinones including a tertiary carbon center. Post-transformations of the synthesized products demonstrate the potential of the developed methodology. A series of mechanistic investigations were also performed.

The machine learning and geostatistical approach for assessment of arsenic contamination levels using physicochemical properties of water.

Arsenic contamination in groundwater due to natural or anthropogenic sources is responsible for carcinogenic and non-carcinogenic risks to humans and the ecosystem. The physicochemical properties of groundwater in the study area were determined in the laboratory using the samples collected across the Varanasi region of Uttar Pradesh, India. This paper analyses the physicochemical properties of water using machine learning, descriptive statistics, geostatistical and spatial analysis. Pearson correlation was used for feature selection and highly correlated features were selected for model creation. Hydrochemical facies of the study area were analyzed and the hyperparameters of machine learning models, i.e., multilayer perceptron, random forest (RF), naïve Bayes, and decision tree were optimized before training and testing the groundwater samples as high (1) or low (0) arsenic contamination levels based on the WHO 10 µg/L guideline value. The overall performance of the models was compared based on accuracy, sensitivity, and specificity value. Among all models, the RF algorithm outclasses other classifiers, as it has a high accuracy of 92.30%, a sensitivity of 100%, and a specificity of 75%. The accuracy result was compared to prior research, and the machine learning model may be used to continually monitor the amount of arsenic pollution in groundwater.

Rh(III)-Catalyzed C8-Spiroannulation of 1-Aminonaphthalenes with Maleimides.

The rhodium(III)-catalyzed C8-spiroannulation of 1-aminonaphthalenes with maleimides is described herein. Initially formed C8-alkenylated 1-aminonaphthalenes can intercept nucleophilic 1-amino groups through the intramolecular aza-Michael reaction, resulting in the formation of spirofused tetracyclic frameworks. This protocol displayed a wide substrate scope and a broad functional group compatibility. The synthetic utility of this process is demonstrated by the gram-scale synthesis, late-stage modification, and synthetic transformations.

Synthesis of 2-Formyl Carbazoles via Tandem Reaction of Indolyl Nitrones with 2-Methylidene Cyclic Carbonate.

The synthesis of functionalized carbazoles as privileged nitrogen heterocycles has emerged as a central topic in drug discovery and material science. We herein disclose the rhodium(III)-catalyzed cross-coupling reaction between indolyl nitrones and 2-methylidene cyclic carbonate as an allylating surrogate, resulting in the formation of C2-formylated carbazoles via tandem C-H allylation, [3 + 2] cycloaddition, aromatization, and benzylic oxidation. The synthetic utility of this protocol is highlighted by a variety of post-transformations of C2-formylated carbazoles.

Visible-light driven electron-donor-acceptor (EDA) complex-initiated synthesis of thio-functionalized pyridines.

A visible/solar-light-induced electron-donor-acceptor (EDA)-aggregated/mediated radical cyclization between (E)-2-(1,3-diarylallylidene)malononitriles and thiophenols leads to poly-functionalized pyridines. The two reacting partners form an EDA complex that absorbs light and triggers the single-electron transfer (SET) to generate a thiol radical, which undergoes addition/cyclization with dicyanodiene through the formation of C-S and C-N bonds.

Visible/solar-light-driven thiyl-radical-triggered synthesis of multi-substituted pyridines.

A light-triggered synthesis of thio-functionalized pyridines is demonstrated using γ-ketodinitriles, thiols, and eosin Y as the photocatalyst. The reaction proceeds via the selective attack on one of the cyano groups by an in situ generated thiyl radical. The reaction also proceeds with nearly equal efficiency using direct sunlight. Large-scale synthesis and a few useful synthetic transformations of the substituted pyridines are also performed.

Visible-Light-Mediated Solvent-Switched Photosensitizer-Free Synthesis of Polyfunctionalized Quinolines and Pyridines.

A solvent (2,2,2-trifluoroethanol (TFE) vs ethyl alcohol (EtOH)) switched synthesis of quinolines and pyridines is illustrated from (E)-2-(1,3-diphenylallylidene)malononitriles via a Pd(II)-catalyzed photochemical process. The active catalyst [L2Pd(0)] generated serves as an exogenous photosensitizer. The process offers predominantly Z-alkenylated quinolines and pyridines in TFE and EtOH, respectively. Furthermore, large-scale synthesis and a few interesting post-synthetic modifications have been demonstrated.

Amalgamation of Farmers' Bio-priming Knowledge in Integrated Nutrient Management for Sustainable Management of Red Cabbage Soil Under Middle Gangetic Plains, India.

Biotic stress management through bio-priming is a common practice among the farmers of the Indo-Gangetic Plains. However, this indigenous technology is less explored for the sustainable management of soil resources. Therefore, field-based experiments (2016-17 and 2017-18) were conducted in Varanasi to evaluate the combined effect of seedling bio-priming and fertilization on biochemical properties, microbiological properties, and fertility of red cabbage soil at harvest. Based on the farmers' fertilization practice, the recommended dose of fertilizers (RDF) of N:P2O5:K2O were applied @ 120:60:60 kg ha-1. Three compatible bio-agents, viz., Trichoderma harzianum, Pseudomonas fluorescens, and Bacillus subtilis were applied alone and in combination with 75% RDF. The effect of treatment combinations was also analyzed for carbon (C) mineralization by conducting an incubation experiment for 90 days. Bio-priming treatments recorded a higher richness of soil microflora and soil fertility than control and sole application of chemical fertilizers. Application of 75% RDF + T. harzianum + P. fluorescens resulted in highest urease and cellulase activities and soil organic C. Inclusion of dual-species bacterial consortium (P. fluorescens and B. subtilis) in integrated system resulted in highest dehydrogenase activity and available P. These priming agents also exhibited significantly higher CO2 fluxes and C mineralization in our incubation study. A microbial consortium of T. harzianum and B. subtilis increased the microbial biomass C and available K. Although application of triple-species consortium improved C mineralization in laboratory conditions, the positive effects lowered down in field conditions. As a bottom-up approach, customization of bio-priming technology among farmers will help in attaining the UN-Sustainable Development Goals.

Assessment of hydrologic impact on flow regime due to dam inception using IHA framework.

In the last century, thousands of dams and diversions have been built to regulate the streamflow, resulting in water impoundment in the upstream and frequent drought conditions in the downstream. It has pressured researchers to study flow regime change and its complication on the downstream biota. The present study planned to develop a framework for trend analyzing of river flow and detecting flow regime change after the inception of Isapur and Arunavati dams, situated on the upstream side of Penganga bridge. Mann-Kendall (MK) and Sen's slope estimator for trend analysis and Indicators of Hydrologic Alteration (IHA) for flow regime alteration analysis were utilized. A total 26 parameters showed negatively altered flow regime with a magnitude varying from - 5.56 to - 100%. Fourteen altered parameters were modified drastically (more than 50% decrease) with the highest modification in 30-day maximum (100%) post-single dam inception. a total of 13 parameters were negatively altered with alteration value - 9.09 to - 86.36% post-double dam inception, out of which, three parameters were severely altered, with the highest alteration in the month of June. The period (1983-1994) was more altered than 1995-2016. This shows that Isapur dam has higher impact on flow regime change than Arunavati dam. Information about alteration of hydrological parameters will be helpful to improve the water flow regulation at Isapur and Arunavati dams for restoring river ecology on the downstream side.

The Renaissance of Organo Nitriles in Organic Synthesis.

In the arena of functional group-oriented organic synthesis, nitrile or cyano functionality is of immense importance. The presence of nucleophilic N-atom, π-coordinating ability of the triple bond, and electrophilic C-center imparts unique and interesting reactivities. Owing to the ability of the nitrile to transform into various other functional groups or intermediates, the chemistry is very rich and diverse. In particular, the involvement of nitrile in numerous organic reactions such as inter- or intramolecular alkyne insertion, [2+2+2] cycloaddition with alkynes, [3+2] cycloaddition with azides, [4+2] cycloaddition with dienes allow the synthesis of many important carbo- and heterocycles. Furthermore, the nitrile serves as a directing group in many C-H bond functionalization reactions to introduce diverse functionalities and participate as a radical acceptor in radical cascade strategies to obtain a large variety of functional molecules. This review mainly focuses on the reactivity and diverse synthetic application of the nitrile including C-H bond functionalization, alkyne insertion, cycloaddition, and thermal or photochemical cascade strategy. The objective of the current review aims at bringing out the striking collection of various nitrile-triggered organic transformations.

Electrochemical Amidation: Benzoyl Hydrazine/Carbazate and Amine as Coupling Partners.

An electrochemical amidation of benzoyl hydrazine/carbazate and primary/secondary amine as coupling partners via concomitant cleavage and formation of C(sp2)-N bonds has been achieved. This methodology proceeds under metal-free and exogenous oxidant-free conditions producing N2 and H2 as byproducts. Mechanistic studies reveal the in situ generations of both acyl and N-centered radicals from benzoyl hydrazines and amines. The utility of this protocol is demonstrated through a large-scale, and synthesis of bezafibrate, a hyperlipidemic drug.

Pd(II)-Catalyzed Synthesis of Furo[2,3-b]pyridines from ß-Ketodinitriles and Alkynes via Cyclization and N-H/C Annulation.

A Pd(II)-catalyzed synthesis of furopyridines has been developed from ß-ketodinitriles and alkynes via an unusual N-H/C annulation. The participation of both the nitrile groups and the concurrent construction of furan and pyridine rings through the formation of C-C, C═C, C-O, C-N, and C═N bonds are the important features. The synthetic applicability is further demonstrated through a series of postsynthetic alterations.

Metal-catalyzed reactions of organic nitriles and boronic acids to access diverse functionality.

The nitrile or cyano (-CN) group is one of the most appreciated and effective functional groups in organic synthesis, having a polar unsaturated C-N triple bond. Despite sufficient stability and being intrinsically inert, the nitrile group can be easily transformed into many other functional groups, such as amines, carboxylic acids, ketones, etc. which makes it a vital group in organic synthesis. On the other hand, despite several boronic acids having a low level of genotoxicity, they have found wide applicability in the field of organic synthesis, especially in transition metal-catalyzed cross-coupling reactions. Recently, transition-metal-catalyzed cascade additions or addition/cyclization processes of boronic acids to the nitrile group open up exciting and useful strategies to prepare a variety of functional molecules through the formation of C-C, C-N and CO bonds. Boronic acids can be added to the cyano functionality through catalytic carbometallation or through a radical cascade process to provide newer pathways for the rapid construction of various important acyclic ketones or amides, carbamidines, carbocycles and N,O-heterocycles. The present review focuses on various transition-metal-catalyzed additions of boronic acids via carbometallation or radical cascade processes using the cyano group as an acceptor.

Visible-Light-Mediated Synthesis of Thio-Functionalized Pyrroles.

An inimitable illustration of the green-light-induced synthesis of thio-functionalized pyrroles has been established using ß-ketodinitriles and thiophenols as the reacting partners and eosin Y as the photocatalyst. Large-scale synthesis and some useful synthetic modifications of the thio-functionalized pyrroles are also demonstrated.

Cu(II)-Promoted Cascade Synthesis of Fused Imidazo-Pyridine-Carbonitriles.

A Cu(II)-promoted synthesis of an aza-fused N-heterocycle having a benz-imidazopyridine scaffold is developed via an addition-cyclization reaction followed by an Ullmann-type C-N coupling between o-iodoanilines and γ-ketodinitriles. This protocol features a broad substrate scope, giving products in 32-84% yields. The compounds show excellent photoluminescence properties having two absorption maxima in the region between 270-280 and 338-350 nm and emission maxima in the range of 502-533 nm. The HOMO-LUMO energy gap of 3.49-3.57 eV was determined using Gaussian 09 at the B3LYP/6-31G (d, p) basis set level. We also demonstrated a few postsynthetic modifications.

Optimizing nutrient use efficiency, productivity, energetics, and economics of red cabbage following mineral fertilization and biopriming with compatible rhizosphere microbes.

Conventional agricultural practices and rising energy crisis create a question about the sustainability of the present-day food production system. Nutrient exhaustive crops can have a severe impact on native soil fertility by causing nutrient mining. In this backdrop, we conducted a comprehensive assessment of bio-priming intervention in red cabbage production considering nutrient uptake, the annual change in soil fertility, nutrient use efficiency, energy budgeting, and economic benefits for its sustainable intensification, among resource-poor farmers of Middle Gangetic Plains. The compatible microbial agents used in the study include Trichoderma harzianum, Pseudomonas fluorescens, and Bacillus subtilis. Field assays (2016-2017 and 2017-2018) of the present study revealed supplementing 75% of recommended NPK fertilizer with dual inoculation of T. harzianum and P. fluorescens increased macronutrient uptake (N, P, and K), root length, heading percentage, head diameter, head weight, and the total weight of red cabbage along with a positive annual change in soil organic carbon. Maximum positive annual change in available N and available P was recorded under 75% RDF + P. fluorescens + B. subtilis and 75% RDF + T. harzianum + B. subtilis, respectively. Bio-primed plants were also higher in terms of growth and nutrient use efficiency (agronomic efficiency, physiological efficiency, apparent recovery efficiency, partial factor productivity). Energy output (26,370 and 26,630 MJ ha-1), energy balance (13,643 and 13,903 MJ ha-1), maximum gross return (US $ 16,030 and 13,877 ha-1), and net return (US $ 15,966 and 13,813 ha-1) were considerably higher in T. harzianum, and P. fluorescens treated plants. The results suggest the significance of the bio-priming approach under existing integrated nutrient management strategies and the role of dual inoculations in producing synergistic effects on plant growth and maintaining the soil, food, and energy nexus.

An expedient route to tricyanovinylindoles and indolylmaleimides from o-alkynylanilines utilising DMSO as a one-carbon synthon.

A Pd(ii)/Cu(ii) catalysed domino synthesis of tricyanovinylindoles has been achieved using DMSO as a one-carbon synthon. The reaction proceeds via the construction of 2-aryl-3-formyl indole followed by sequential addition of malononitrile and a CN resulting in two C-C, one C[double bond, length as m-dash]C and one C-N bonds in the final product. Furthermore, post-synthetic modification results in the unprecedented formation of 4-cyano-3-indolylmaleimides. Photophysical studies of selected compounds show emission in the visible range.

Safeguarding the fragile rice-wheat ecosystem of the Indo-Gangetic Plains through bio-priming and bioaugmentation interventions.

Managing agrochemicals for crop production always remains a classic challenge for us to maintain the doctrine of sustainability. Intensively cultivated rice-wheat production system without using the organics (organic amendments, manures, biofertilizers) has a tremendous impact on soil characteristics (physical, chemical, and biological), environmental quality (water, air), input use efficiency, ecosystem biodiversity, and nutritional security. Consequently, crop productivity is found to be either decreasing or stagnating. Rice-wheat cropping system is the major agroecosystem in India feeding millions of people, which is widely practiced in the Indo-Gangetic Plains (IGP). Microorganisms as key players in the soil system can restore the degraded ecosystems using a variety of mechanisms. Here, we propose how delivery systems (i.e., the introduction of microbes in seed, soil, and crop through bio-priming and/or bioaugmentation) can help us in eradicating food scarcity and maintaining sustainability without compromising the ecosystem services. Both bio-priming and bioaugmentation are efficient techniques to utilize bio-agents judiciously for successful crop production by enhancing phytohormones, nutrition status, and stress tolerance levels in plants (including mitigating of abiotic stresses and biocontrol of pests/pathogens). However, there are some differences in application methods, and the latter one also includes the aspects of bioremediation or soil detoxification. Overall, we have highlighted different perspectives on applying biological solutions in the IGP to sustain the dominant (rice-wheat) cropping sequence.

Visible-Light-Accelerated Pd-Catalyzed Cascade Addition/Cyclization of Arylboronic Acids to γ- and ß-Ketodinitriles for the Construction of 3-Cyanopyridines and 3-Cyanopyrrole Analogues.

The one-pot synthetic strategies for 2,4,6-triarylnicotinonitriles and 2,5-diaryl-1H-pyrrole-3-carbonitriles have been accomplished via a Pd-catalyzed coupling of arylboronic acid with 2-(3-oxo-1,3-diarylpropyl)malononitrile and 2-(2-oxo-2-arylethyl)malononitrile, respectively, under mild reaction conditions, followed by intramolecular cyclization of an intermediate formed after the regeneration of the catalyst under acidic reaction conditions. The cascade reactions proceed in 1,2-dichloroethane solvent under visible-light irradiation, and the active catalyst is generated in situ in the presence of catalytic amounts of Pd(OAc)2 and 2,2'-bipyridine. The active Pd catalyst undergoes photoexcitation by the virtue of metal-to-ligand charge transfer (MLCT), and subsequent redox trans-metalation occurs with arylboronic acid, thus obviating the necessity of any exogenous photosensitizer. The targeted products, composed of a new C-C, a C-N, a C═N, and two new C═C bonds, were isolated in good yields.

The potential of arbuscular mycorrhizal fungi in C cycling: a review.

Arbuscular mycorrhizal fungi (AMF) contribute predominantly to soil organic matter by creating a sink demand for plant C and distributing to below-ground hyphal biomass. The extra-radical hyphae along with glomalin-related soil protein significantly influence the soil carbon dynamics through their larger extent and turnover period need to discuss. The role of AMF is largely overlooked in terrestrial C cycling and climate change models despite their greater involvement in net primary productivity augmentation and further accumulation of this additional photosynthetic fixed C in the soil. However, this buffering mechanism against elevated CO2 condition to sequester extra C by AMF can be described only after considering their potential interaction with other microbes and associated mineral nutrients such as nitrogen cycling. In this article, we try to review the potential of AMF in C sequestration paving the way towards a better understanding of possible AMF mechanism by which C balance between biosphere and atmosphere can be moved forward in more positive direction.