Dimerization of 3-substituted 2-oxindoles has been developed under a mild electrochemical condition, avoiding toxic chemical oxidants and metal by-products. This methodology forms a C­(sp3)–C­(sp3) bond at the pseudobenzylic position of two partners of 2-oxindoles with a broad substrate scope. These dimeric structural motifs are important building blocks for the total synthesis of pyrroloindoline alkaloids. Furthermore, this work demonstrates in-depth mechanistic insights employing electrochemistry, which suggests a stepwise one proton transfer (PT) and two electron transfer (ET) processes. Most significantly, reaction rate acceleration has been demonstrated by exploiting the base-assisted proton-coupled electron transfer (PCET) pathway. Hence, this work brings a new dimension in the field of electro-organic synthesis with the help of nature’s favorite kinetic route, i.e., PCET, to lower the kinetic barrier.

We report an efficient direct alkynylations of 3-alkyl/aryl 2-oxindoles employing ethynyl-1,2-benziodoxol-3(1H)-one (EBX) to afford a wide variety of 3-alkynyl-3-alkyl/aryl 2-oxindole under transition-metal free condition. In addition to activated carbonyl compounds viz. 2-oxindole-3-alkylcarboxylates, this direct alkynylations protocol works efficiently on 3-alkyl/aryl 2-oxindols as well thereby widening the scope even further. Eventually, a Pd(0)-catalyzed asymmetric decarboxylative allylation of few products is shown to furnish synthetically viable enantioenriched 2-oxindoles with C-3 quaternary stereocenters.

Ternary carbide in metal matrix composites constitute a big challenge in the industry, and in this regard their surface treatment is one of the most important issues. Ternary carbide (CuxTiyCz, where x, y and z are integers) thin films are synthesized by magnetron sputtering and characterized with respect to the film depth. X-ray photoelectron spectroscopy (XPS) of Cu-2p and Ti-2p peaks shows the associated shake-up satellite peaks at a smaller film depth; the peak intensity is reduced at a higher depth. The relative intensity of Cu and Ti increases at a larger film depth. The optical band gap varies from 1.83 to 2.20 eV at different film depths.

Biomimetic total syntheses of either enantiomers of a number of ergot alkaloids, chanoclavine I (1b), chanoclavine I aldehyde (1c), pyroclavine (1e), festuclavine (1f), pibocin A (1g), 9-deacetoxyfumigaclavine C (1h), and fumigaclavine G (1i), have been achieved from seco-agroclavine (1a). The advanced intermediate for seco-agroclavine (1a) was synthesized via a key thiourea-catalyzed intramolecular nitronate addition onto α,β-unsaturated ester.

A general approach to bispyrroloindolines via a key thiourea-catalyzed addition of malonates to 3-sulfonyl-3′-indolyl-2-oxindoles is reported. The enantioselelective process is found to be highly effective (up to 94% ee), where a C–C bond formation leads to the synthesis of a number of 2-oxindoles with an all-carbon quaternary stereocenter.

An organocatalytic enantioselective aldol reaction using paraformaldehyde as C1-unit has been developed for the synthesis of 2-oxindoles sharing vicinal all-carbon quaternary stereocenters. The methodology is eventually employed in the formal total synthesis of (+)-folicanthine (1b).

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