An efficient and environmentally friendly process for the synthesis of 3,4‐dihydropyrimidones via the Biginelli‐type condensation reaction using poly(ethylene glycol)‐bound sulfonic acid as catalyst irradiated by microwave has been developed. The functionalized poly(ethylene glycol) acted simultaneously as catalyst and as solvent in the condensation. The workup was easy, and the products were obtained in good to excellent yields and high purities.
Direct synthesis of 1,2,4-triazolidines have been readily achieved by the visible-light-promoted reaction of N-aryl glycines and azobenzenes under mild conditions.
The straightforward visible-light-induced synthesis of stilbene compounds via the cross-coupling of nitroalkenes and diazonium tetrafluoroborates under transition-metal-free conditions is described. The protocol uses green LEDs as light sources and eosin Y as an organophotoredox catalyst. Broad substrate scope and exclusive selectivity for the (E)-configuration of stilbenes are observed. This protocol proceeds via a radical pathway, with nitroalkenes serving as the radical acceptor, and the nitro group is cleaved during the process.
Ni(acac)2 and PMHS were found to be an excellent catalytic system for the chemoselective transfer hydrogenation of nitro-compounds to primary amines. Under mild conditions a series of nitro-compounds containing a variety of sensitive functional groups including aldehydes, esters, cyano, and nitrine were reduced to their corresponding amines in good to excellent yields with no byproduct.