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Organocatalysis was established to be a wide-applicable approach from its inception and rediscovery in the year 2000, where proline was used as a catalyst in aldol condensation and soon after the successful emergence of iminium catalysed reactions in organic synthesis. Development of new potential catalytic systems is always an important as well as an uphill task for scientists and researchers. The fundamental organic synthesis majorly deals with metal based catalysts, whereas there is a constant surge of developing metal free reaction condition to make the reactions environmental friendly. For the synthesis of complex organic molecules, reduction and oxidation reactions are always needed and there are plenty of catalysts available for these reactions. Organocatalysts are also developed and applied for these two elementary reactions. This review focuses on some of the latest developments and applications of organocatalysts in oxidation and reduction reactions in fundamental organic synthesis.

Immuno-positron emission tomography (immuno-PET) is a rapidly growing imaging technique in which antibodies are radiolabeled to monitor their in vivo behavior in real time. However, effecting the c...

The environmental pollution and hazards have become the prime topic of concern in the twenty-first-century world and a warning to existing mankind. The researchers and chemists are also putting their way forward to combat the alarming situation across the world. In this context, reactions that are being carried out in water have attracted attention from the past decade. The conventional organic synthesis relies profoundly on organic solvents for a huge number of reactions, mainly for dissolving the compounds and assisting chemical reactions, because a number of reagents and catalysts are either unsuited or immiscible in water. In spite of the constraints, substantial efforts have been dedicated to overcome the problems because water not only reduces the environmental hazards of organic synthesis but also may benefit chemical reactions by delivering unforeseen selectivities and reactivities. The development of water-compatible/water-stable catalysts has emerged as a troubleshooter, eliciting a quantum leap in organic synthesis in water. Use of water has simplified the workup procedure too, as organic compounds are typically insoluble in water, extraction with suitable organic solvents can separate the compounds from catalysts, and the catalysts can also be separated and reused by centrifugation and filtration. This review deals with advances in catalytic methods under aqueous medium over the past few years.

Conventionally, the organic reactions are accomplished by conductive heating with an external heat source like an oil bath. On the contrary, since its inception, the application of microwave irradiation is growing as a suitable alternate heating method in organic synthesis. Microwave heating considerably reduces the reaction time without promoting any side reactions. The fundamental synthetic organic chemistry majorly deals with transition-metal-catalyzed C–C and C–heteroatom bond formation reactions. It is one of the most important methods in contemporary chemistry resulting in a tremendous increment in the applications of these reactions during the last few years. This field has been acknowledged with a number of Nobel Prizes during the last decade (2001, 2005 and 2010). A considerable effort has been done on the continuous development of new ligands and catalysts as well as an increased understanding of the mechanisms for the improvement of the reaction condition. This review focuses on some of the latest developments in the area of cross-coupling reactions aided by microwave irradiation.

Immuno-positron emission tomography (immuno-PET) is a rapidly growing imaging technique in which antibodies are radiolabeled to monitor their in vivo behavior in real time. However, effecting the controlled conjugation of a chelate-bearing radioactive atom to a bulky antibody without affecting its immunoreactivity at a specific site is always challenging. The in vivo stability of the radiolabeled chelate is also a key issue for successful tumor imaging. To address these points, a facile ultra-stable radiolabeling platform is developed by using the propylene cross-bridged chelator (PCB-TE2A-alkyne), which can be instantly functionalized with various groups via the click reaction, thus enabling specific conjugation with antibodies as per choice. The PCB-TE2A-tetrazine derivative is selected to demonstrate the proposed strategy. The antibody trastuzumab is functionalized with the

18F is the most widely used radionuclide for PET imaging. However, peptides and antibodies cannot be radiolabeled with fluorine-18 without the extra attachment of an auxiliary group, and these biomolecules are typically radiolabeled indirectly through two reaction steps. The Al–18F complex has recently been developed as a new radiolabeling technique; however, the harsh conditions required for Al–18F complexation have restricted its widespread application for heat-sensitive biomolecules. Here we report fully optimized Al–18F radiofluorination enabling successful radiolabeling under mild conditions. Six different macrocyclic chelators with different backbones (NOTA, DOTA, and NODA) and pendant arms were tested for efficient radiolabeling using the Al–18F complex. We also optimized the radiolabeling conditions to achieve radiofluorination at a lower temperature by changing the radioactive fluorine source, labeling buffer, and organic solvent. By employing a NODA backbone chelator bearing two acetate pendant arms and one benzyl-NCS moiety, >60% Al–18F complexation was achieved at 30 °C in ammonium acetate buffer (pH 5.5). An antibody conjugated with the NODA chelator was also successfully radiolabeled with 18F at 30 °C using Al–18F complexation without loss of immunoreactivity.

Consecutive chemo- and regio-selective decarboxylative C H arylation, followed by carbonylative C C coupling of aryl halide with isocyanide/alcohol was applied for the first time in one-step synthesis of carbonyl dibenzofurans with nanodomain cuprous oxide under aerobic condition. As a proof of concept, several novel dibenzofurans were synthesized from 2-(3-iodophenoxy)benzoic acid in good yield. The tandem protocol eliminates the use of excess catalysts, hazardous organic solvents, heavy metals like palladium or rhodium, ligands, oxidants, or external additives. More importantly, the cubic Cu(I) nanocatalyst can be recovered and recycled for three consecutive reactions without any significant loss of catalytic activity or any change in its morphology. Use of water as solvent and reusable catalyst makes the reaction environment friendly.

Nanodomain Pd(0) mediated regio- and stereo-selective synthesis of (Z)-3-methyleneisoindoline-1-ones and furo[3,2-h]quinolines in water was achieved in high yield. The novel one-pot domino-Sonogashira-cyclization protocol is environment friendly as it eliminates the use of ligands, copper, organic solvents or ionic liquids and homogeneous catalysts. More importantly, the nanocatalyst can be recovered in high yield and recycled for five consecutive reactions without any significant loss of reactivity.

An environmentally benign one-pot procedure has been developed for the syntheses of triazole-fused tetracyclic glycosides in aqueous medium. The two step one-pot synthesis involves Sonogashira reaction between azido-alkynes and aryl halides followed by intramolecular 1,3-dipolar cyclization using cubic cuprous oxide nanoparticles as reusable catalyst, under aerobic condition. The method excludes the use of any surfactants or additional ligands as stabilizing agents. The catalyst could be used up to three recycles without any loss of catalytic activity. The method has a broad perspective for the synthesis of medium size ring systems.

An environmentally benign chemical process for the C–C coupling of aryl halides with isocyanides in aqueous medium has been developed using cubic copper (I) oxide nanoparticles as reusable catalyst. The use of nano-catalyst eliminates the use of any stabilizing ligands or additives as well as the use of organic solvents. The catalyst exhibited comparable efficiency up to three recycles and was found to be very effective for the synthesis of varied amides leading to biologically significant scaffold.

A microwave assisted green protocol for the syntheses of triazole fused benzoxazines, benzoxazepines, quinoxalines, and benzothiazines was investigated using basic alumina as solid support. The one-pot reaction was carried out using Cu(phen)(PPh3)Br as a catalyst. The protocol did not require the use of any additional ligands, base or the use of expensive and toxic palladiums.

A convenient route for the synthesis of triazole fused benzoxazepines or benzodiazepines in aqueous micellar medium has been described. The two step one-pot synthesis involves Sonogashira reaction of prop-2-ynyl 2-azidobenzoates and aryl iodides followed by intramolecular azide–alkyne cyclization using Pd(CH 3 CN) 2 Cl 2 as catalyst and ethanedial,1,2-bis(2-methyl-2-phenylhydrazone) as ligand, under atmospheric condition. The method excludes the use of copper salts as catalyst as well as hazardous organic solvents.

A microwave assisted green protocol for the synthesis of 1,4-disubstituted triazolyl N-carboxamides was explored using basic alumina as solid support. The method allows domino Ullmann-type reaction, Click reaction and formation of ester or amide linkages in a single reaction vessel using Cu(phen)(PPh3)Br and CMPA as catalyst and basic alumina as solid support in high yield. The protocol did not require addition of any external ligands or base. The method was also found to be equally good for the synthesis of bis triazole adducts.

An environmentally benign and operationally simple methodology was developed for the synthesis of 3-benzyl-3-(indol-3-yl)-2-phenyl-2,3-dihydroisoindolinones via multicomponent one-pot reaction involving 2-iodo- N -phenylbenzamides, terminal alkyne, and substituted indoles in aqueous micellar medium. It involves copper-mediated domino Sonogashira-5-exo-dig-cyclization followed by regioselective nucleophilic addition of indoles, all in one-pot, using CuI as catalyst and 2,2′-(1 E ,1′ E )-(1 R ,2 R )-cyclohexane-1,2-diylbis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)diphenol as ligand under aerobic condition.

A high yielding novel methodology was developed for the regio- and stereo-selective syntheses of (Z)-3-methyleneisoindoline-1-ones from substituted 2-phenylethynyl benzamides, generated in situ from 2-(phenylcarbamoyl)phenyl-1-H-imidazole-1-sulfonates and corresponding alkyne by Cu-free Sonogashira cross-coupling–5-exo-dig-cyclization in aqueous medium under sonication. The compound could easily be purified by recrystallization from EtOAc without column chromatography.

An environmentally benign, high yielding, and operationally simple protocol has been developed for the regioselective synthesis of furo[3,2- h ]quinolines in aqueous micellar medium involving Cu-free domino Sonogashira reaction followed by 5- endo -dig-cyclization of substituted 8-hydroxyquinolines and terminal alkyne by using Pd(C 6 H 5 CN)Cl 2 as catalyst and 2-pyridinecarboxaldehyde methylphenyl hydrazone as ligand under aerobic condition.

Nanodomain Pd(0) mediated regio- and stereo-selective synthesis of (Z)-3-methyleneisoindoline-1-ones and furo[3,2-h]quinolines in water was achieved in high yield. The novel one-pot domino-Sonogashira-cyclization protocol is environment friendly as it eliminates the use of ligands, copper, organic solvents or ionic liquids and homogeneous catalysts. More importantly, the nanocatalyst can be recovered in high yield and recycled for five consecutive reactions without any significant loss of reactivity.

An environmentally benign one-pot procedure has been developed for the syntheses of triazole-fused tetracyclic glycosides in aqueous medium. The two step one-pot synthesis involves Sonogashira reaction between azido-alkynes and aryl halides followed by intramolecular 1,3-dipolar cyclization using cubic cuprous oxide nanoparticles as reusable catalyst, under aerobic condition. The method excludes the use of any surfactants or additional ligands as stabilizing agents. The catalyst could be used up to three recycles without any loss of catalytic activity. The method has a broad perspective for the synthesis of medium size ring systems.

This environmentally benign reaction proceeds via a domino Sonogashira-5-exo-dig-cyclization followed by regioselective addition of compounds (III) or (VI).

The solid support plays a dual role as it eliminates the use of an organic solvent as well as a Pd-catalyst.

A convenient route for the synthesis of triazole fused benzoxazepines or benzodiazepines in aqueous micellar medium has been described. The two step one-pot synthesis involves Sonogashira reaction of prop-2-ynyl 2-azidobenzoates and aryl iodides followed by intramolecular azide–alkyne cyclization using Pd(CH 3 CN) 2 Cl 2 as catalyst and ethanedial,1,2-bis(2-methyl-2-phenylhydrazone) as ligand, under atmospheric condition. The method excludes the use of copper salts as catalyst as well as hazardous organic solvents.

The synthesis of the title compounds involves in situ formation of organic azides, 1,3-dipolar cycloaddition of the latter with terminal alkynes and amide or ester bond formation.

An environmentally benign and operationally simple methodology was developed for the synthesis of 3-benzyl-3-(indol-3-yl)-2-phenyl-2,3-dihydroisoindolinones via multicomponent one-pot reaction involving 2-iodo- N -phenylbenzamides, terminal alkyne, and substituted indoles in aqueous micellar medium. It involves copper-mediated domino Sonogashira-5-exo-dig-cyclization followed by regioselective nucleophilic addition of indoles, all in one-pot, using CuI as catalyst and 2,2′-(1 E ,1′ E )-(1 R ,2 R )-cyclohexane-1,2-diylbis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)diphenol as ligand under aerobic condition.

Furoquinolines are prepared from hydroxyquinolines and alkynes via a copper-free Sonogashira coupling/cycloisomerization sequence in aqueous micellar medium under aerobic conditions.

A novel method for the synthesis of the title species through copper-free domino Sonogashira cross-coupling/5-exo-dig-cyclization reaction of sulfonates (I) with terminal alkynes (II) is developed.

An environmentally benign one-pot protocol has been developed for the syntheses of 3-alkyl/aryl-3-(pyrrole/indole-2/3-yl)-2-phenyl-2,3-dihydro-isoindolinones via a multi-component one-pot reaction involving 2-iodo-N-phenylbenzamides, terminal alkyne and substituted indoles/pyrroles in aqueous medium using cubic cuprous oxide nanoparticles as catalyst. It involves domino Sonogashira-5-exo-dig-cyclization followed by regioselective nucleophilic addition of indoles or pyrroles, in aqueous medium without using any surfactants or additional ligands.