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.

A sequential construction of C-C, C-O, C═N, and C═O bonds from alkenes leading to the direct synthesis of isoxazolines in the presence of tert-butyl nitrite, quinoline, and the Sc(OTf) catalyst in DCE at 80 °C has been accomplished. An unprecedented three consecutive C-H functionalizations of two styrenes are involved in this isoxazoline synthesis. In this radical-mediated reaction, one-half of the aryl alkene is converted into an intermediate 2-nitroketone, which serves as a 1,3-dipolarophile and undergoes cycloaddition with the other half of the unreacted aromatic terminal alkene. The use of an alkyne in lieu of an alkene leads to the formation of isoxazole under identical reaction conditions.

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.

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.

An electrochemical amidation of benzoyl hydrazine/ carbazate and primary/secondary amine as coupling partners via concomitant cleavage and formation of C(sp 2 )−N bonds has been achieved. This methodology proceeds under metal-free and exogenous oxidant-free conditions producing N 2 and H 2 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 largescale, and synthesis of bezafibrate, a hyperlipidemic drug.