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A light-mediated synthesis of thio-functionalized pyridines has been achieved using γ-ketodinitriles and thiophenols under green LED irradiation or direct sunlight.

Discussion of the recent reports on dual metallo-photocatalytic strategies using graphitic carbon nitride materials in organic syntheses.

N-Iodosuccinimide catalyzed, visible-light-induced oxidative decarboxylative cross-coupling between cinnamic acids and NH-sulfoximines leading to α-keto-N-acyl sulfoximines is presented.

A Cu(OTf)2-mediated regioselective dearomative aryl-hydroxylation across the C(sp2)N bond of 2-aryl quinoxalines and bis-N-arylation of (benz)imidazoles were developed using aryl boronic acids.

An inimitable illustration of the green-light-induced synthesis of thio-functionalized pyrroles has been established using β-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.

Syntheses of β-keto sulfones have been reported using g-C3N4 as a recyclable photocatalyst along with green chemistry metrics and eco-scale evaluation.

A Cu(I)-mediated cascade cyclization/annulation of unprotected o-alkynylanilines with maleimides in one pot is developed. The protocol offers sequential formation of one C-N and two C-C bonds to deliver fused benzo[a]carbazoles having free NH skeletons. The annulated products display fluorescence emission in the range of 485-502 nm with a large Stokes shift and fluorescence lifetime of ∼17 ns. The annulated 3aa displays AEE behavior in the ethanol/hexane system and possesses marigold-flower-like morphology at the aggregated state. Cell viability assays enumerate biocompatible AEEgens, while their high intracellular fluorescence depicts cell imaging applicability.

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.

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.

An electrochemical amidation of benzoyl hydrazine/carbazate and primary/secondary amine as coupling partners via concomitant cleavage and formation of C(sp

An inimitable illustration of a green-light-induced, regioselective difunctionalization of terminal alkynes has been disclosed using sodium arylsulfinates and carboxylic acids in the presence of eosin Y as the photocatalyst. The present methodology is further demonstrated by employing NH4SCN as an S-centered nucleophile instead of carboxylic acid. The mechanistic investigation reveals a radical-induced iodosulfonylation followed by a base-mediated nucleophilic substitution. The mechanism is supported by various studies, viz., radical-trapping experiment, fluorescence quenching, and CV studies. In this protocol, (Z)-β-substituted vinylsulfones are obtained, exclusively covering a broad range of alkynes and nucleophiles, which are often unaddressed. The present strategy can tolerate structurally discrete substrates with steric bulk and different electronic properties, which provides a straightforward and practical pathway for the synthesis of highly functionalized (Z)-β-substituted vinylsulfones. Herein, C-O and C-S bonds are assembled simultaneously with the concomitant introduction of important functional groups, viz., ester, thiocyanate, and sulfone.

An intermolecular radical based distal selectivity in appended alkyl chains has been developed. The selectivity is maximum when the distal carbon is γ to the appended group and decreases by moving from γ to δ to e positions. In –COO- linked alkyl chains, the same distal γ-selectivity is observed irrespective of its origin, either from the alkyl carboxy acid or alkyl alcohol. The appended groups include esters, N-H protected amines, phthaloyl, sulfones, sulfinimide, nitrile, phosphite, phosphate and borate esters. In borate esters, boron serves as a traceless directing group, which is hitherto unprecedented for any remote Csp3-H functionalization. The selectivity order follows the trend: 3o benzylic > 2o benzylic > 3o tertiary > α to keto > distal methylene (γ > δ > e). Computations predicted the radical stability (thermodynamic factors) and the kinetic barriers as the factors responsible for such trends. Remarkably, this strategy eludes any designer catalysts, and the selectivity is due to the intrinsic substrate reactivity.

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.

A visible-light-induced synthesis of N-hydroxybenzimidoyl cyanides from aromatic terminal alkenes is achieved by using Eosin Y as an organic photoredox catalyst. The process goes via a radical pathway with successive incorporation of two nitrogen atoms, one each from tert-butyl nitrite and ammonium acetate. The final product is achieved by the concomitant installation of an oxime and a nitrile group. DFT calculation supports a biradical pathway and all the proposed steps. A few useful synthetic transformations of N-hydroxybenzimidoyl cyanide are also illustrated.

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

Hypervalent iodine (HVI) chemistry is a rapidly growing subdomain of contemporary organic chemistry because of its enormous synthetic applications. The high nucleofugality of the phenyliodonio group (-I

Dyes are colored compounds that when applied to a material provides color with or without a change in its chemical structure. Substance bearing coloring capacity has widespread applications in textile, pharmaceutical, food, cosmetics, plastics, photographic, and paper industries, etc. The disposal of wastewater from dyes industries to nearby water bodies contaminates the water and foist harmful effects on human life as well as aquatic animals, thereby upsetting the environment. In particular, the textile wastewater can be regarded as the most polluting of all the industrial sectors as it consumes a large volume of water during the dyeing and finishing process in the industries. Based on the increased demand for textile products, textile effluents have a crucial role in causing severe pollution to environment. Besides this, the hazardous impact of untreated textiles is also of great concern. Owing to the growing awareness and environmental impact, the decolorization, and detoxification of the industrial dye effluents are essential before it is disposed to the nearby water bodies. Several methods have been introduced for the detoxification of textile dyes, namely, (1) physical; (2) chemical; and (3) biological. Among all the established process for the decolorization of the textile dyes, the biological approach has gained considerable attention because of its economic viability, eco-friendliness, and broad applicability to a variety of dyes. In this chapter, a brief description of the decolorization of textile dyes from wastewater treatment has been discussed. The chapter starts with a brief outline of dye pollution, classification of textile dyes, and their environmental impact, treatment option for dye effluents such as physio-chemical method, and biological method. The chapter primarily focuses on the decolorization of textile dyes by biological methods, which include (1) fungal; (2) bacterial; (3) aerobic and anaerobic; (4) algae; (5) enzymatic; and (6) biosorption. Detailed information regarding the decolorization of textile dyes by various biological methods is briefly disclosed.

A Cu(I)-mediated cascade cyclization/annulation of unprotected

A sustainable Mn(I)-catalyzed exclusive solvent-dependent functionalization of imidazopyridine with maleimide via an electrophilic metalation at the distal (in 2,2,2-trifluoroethanol (TFE)) and chelation assisted at the proximal (in tetrahydrofuran (THF)) has been developed. The strategy was successfully applied to the drug Zolimidine and a broad range of substrates, thereby reflecting the method’s versatility.

Bu4NI-catalyzed regioselective N2-methylation, N2-alkylation, and N2-arylation of tetrazoles have been achieved using tert-butyl hydroperoxide (TBHP) as the methyl source, alkyl diacyl peroxides as the primary alkyl source, alkyl peresters as the secondary and tertiary alkyl sources, and aryl diacyl peroxides as the arylating source. These reactions proceed without pre-functionalization of tetrazole and in the absence of any metal catalysts. Here, peroxides serve the dual role of oxidants as well as alkylating or arylating agents. Based on DFT calculations, it was found that spin density, transition-state barriers (kinetic control), and thermodynamic stability of the products (thermodynamic control) play essential roles in the observed regioselectivity during N-alkylation. This radical-mediated process is amenable to a broad range of substrates and provides products in moderate to good yields.

A TBHP mediated carbonylation–peroxidation of styrene, α-peroxidation of α-substituted unsymmetrical internal alkenes and concurrent peroxidation–carbonylation–cycloalkylation/cycloetherifiction of internal cyclic alkene (indene) have been developed.

In the presence of [Ir(dtbbpy)(ppy)2]PF6 photocatalyst and white LEDs, one-third of N-alkylated indoles undergo oxidative dearomatization and serves twice as the C2-electrophilic partner. The remaining two-third act as the C3-nucleophile, prompting two sequential electrophilic substitutions with the in situ generated C2-electrophile that leads to C2-quaternary indolinones at room temperature.

The upsurge interest in the development of efficient methodologies for the construction of nitrogen-containing frameworks via the use of expedient reagents have been creating a renaissance in contemporary organic chemistry. In this perspective, tertbutyl nitrite (TBN) is an emerging building block. Due to its unique structural features, it shows differential reactivity under different reaction conditions. These diverse reactivities have resulted in the construction of a diverse array of complex N-containing molecules. The primary objective of the present review is to bring the latest findings of TBN in terms of its applications in reactions (oxidation, diazotization, nitrosation, nitration, oximation, N-synthon, and miscellaneous reactions) into the limelight. For simplicity and brevity, reactions in each section are explained with the mechanism of formation and selected examples are given.

tert-Butyl nitrite (TBN) mediated synthesis of 3-aryl-1,2,4-oxadiazol-5(4H)-ones has been accomplished using terminal aryl alkenes via a biradical reaction intermediate. Three consecutive sp2 C–H bond functionalizations of styrenes afforded 3-phenyl-1,2,4-oxadiazol-5(4H)-ones via the formation of new C═N, C═O, C–O, and two C–N bonds. Both of the N atoms originate from TBN, while the carbonyl oxygen is from the water (moisture) the other oxygen from the N═O part of the TBN.

In the last few years, the photo-redox process via single-electron transfer (SET) has received substantial attention for the synthesis of targeted organic compounds due to its environmental friendliness and sustainability. Of late visible-light-mediated difunctionalization of alkenes has gained much attention because of its step economy, which allows the consecutive installation of two functional groups across the C=C bond in a single operation. The construction of N-containing compounds has always been important in organic synthesis. Molecules containing C-N bonds are found in many building blocks and are important precursors to other functional groups. Meanwhile, C-N bond formation via the addition of the C=C double bond is gaining prominence. Therefore, considering the influence and synthetic potential of the C-N bond, here we provide a summary of the state of the art on visible-light-driven difunctionalizations of alkene. We hope that the construction of the C-N bond via visible-light-mediated difunctionalization of alkenes will be useful for medicinal and synthetic organic chemists and will inspire further reaction development in this interesting area.

An intermolecular radical based distal selectivity in appended alkyl chains has been developed. The selectivity is maximum when the distal carbon is γ to the appended group and decreases by moving from γ → δ → ε positions. In –COO– linked alkyl chains, the same distal γ-selectivity is observed irrespective of its origin, either from the alkyl carboxy acid or alkyl alcohol. The appended groups include esters, N–H protected amines, phthaloyl, sulfone, sulfinimide, nitrile, phosphite, phosphate and borate esters. In borate esters, boron serves as a traceless directing group, which is hitherto unprecedented for any remote Csp3–H functionalization. The selectivity order follows the trend: 3° benzylic > 2° benzylic > 3° tertiary > α to keto > distal methylene (γ > δ > ε). Computations predicted the radical stability (thermodynamic factors) and the kinetic barriers as the factors responsible for such trends. Remarkably, this strategy eludes any designer catalysts, and the selectivity is due to the intrinsic substrate reactivity., An intermolecular amination at the distal methylene carbon has been realized in an appended alkyl chain with electron withdrawing groups. Traceless remote Csp3–H functionalization has been accomplished using borate esters.

An inimitable illustration of a green-light-induced, regioselective difunctionalization of terminal alkynes has been disclosed using sodium arylsulfinates and carboxylic acids in the presence of eosin Y as the photocatalyst. The present methodology is further demonstrated by employing NH

This personal account is mainly focused on the author's involvement in the field of transition metal-catalyzed peroxide based radical reactions. Over the past decades, radical chemistry has flourished and become crucial in contemporary synthetic organic chemistry. Owing to the presence of a single electron in one orbital, radicals are very unstable and react very fast. To carry out desired transformations and to control the side reactions the stabilizations of these radicals is essential. Fortunately, the implementation of a suitable transition metal and peroxide combination into the radical reactions have proved beneficial. Transition metals not only stabilizes the radicals but also protects them from being quenched by undesired homo-coupling or fragmentation. Transition metal-catalyzed radical-radical reactions provide an innovative way for the construction and derivatization of carbocycles and heterocycles. The objective of this review is to give an overview of the construction and derivatization of heterocycles through the lens of radical chemistry, mainly focusing on research work done by our group.

In last few decades, the transition metal-catalyzed C-H bond activation and alkyne annulation reactions have turned out to be effective methods for the construction of highly important heterocycles. In particular, the Ru(II) catalysts have been used for the oxidative coupling between an internal alkynes and readily available nitrogen directed compounds in a rapid and sustainable manner. The Ru(II) catalysts are very much beneficial due to their stability in both air and water, ease of preparation, inexpensive than those of Rh(III) and designer Co(III) catalysts usually used for alkyne annulation reactions, requirement of mild reaction conditions, and compatible with various oxidants. Owing to these advantages of Ru(II) catalysts herein, we attempt to highlight the recent development in C-H activation and annulation reactions, which lead to the formation of several important N-heterocycles.