Cyclotrimerization of alkynes catalyzed by a self-supported cyclic tri-nuclear nickel(0) complex with α-diimine ligands

Abstract

The cyclic tri-nickel(0) complex [{Ni(μ-LMe-2,4)}3] (LMe-2,4 = [(2,4-Me2C6H3)NC(Me)]2) self-supported by the α-diimines catalyzes cyclotrimerization of alkynes to form substituted benzenes.

Unified Electrochemical Synthetic Strategy for [2 + 2 + 2] Cyclotrimerizations: Construction of 1,3,5- and 1,2,4-Trisubstituted Benzenes from Ni(I)-Mediated Reduction of Alkynes

“…The cyclotrimerization of terminal alkynes is one of the most widely used transformations for the construction of substituted benzene rings. − Since its initial discovery in 1948 by Reppe involving Ni and phosphine, many key metal-based catalysts or complexes have been developed for cyclotrimerization (Scheme A). − Recent advances in this field have reported various regioselective processes by elaborating different metal catalytic complexes with various ligands such as cobalt, nickel, germanium, iron, chromium, rhodium, titanium, niobium, tantalum, and ruthenium. − The majority of these innovative methods provided the 1,2,4-trisubstituted benzenes, whereas the 1,3,5- regioisomers were obtained by using mono- or bimetallic catalysts, and at times with additives. , In addition to metal-catalyzed reactions, radical cyclizations involving terminal alkynes and silyl radicals to construct the 1,2,4-regioisomers are also known (Scheme B) . Recently, Lei reported the electrochemical variant of Rovis’ photocatalytic Co-catalyzed [2 + 2 + 2] cycloaddition reaction, wherein cyclotrimerization of alkynes to 1,2,4-substituted arenes was accomplished with a phosphine ligand and an amine additive (Scheme C).…”

Naphthaldehyde-based Schiff base dyes: aggregation-induced emission and high-contrast reversible mechanochromic luminescence

“…S4 (ESI†). The absorption band at λ = 319 nm represents the electronic transition of the Schiff base unit, 19 and the absorption peak at λ = 396 nm is tentatively assigned to the electron–electron transition from the Schiff base to the amide–pyridine ring, which is greatly affected by the polarity of the solvent. 20 Meanwhile, the wide absorption wavelength range from 419 nm to 475 nm is due to the formation of intramolecular hydrogen bonds.…”

A phenoxy-bridged trinuclear Ni(ii) complex: synthesis, structural elucidation and molecular docking with viral proteins

“…8 Mixed-ligand trinuclear coordination complexes supported by phenolate-bridged ligands have also been reported. 9 Trinuclear compounds could have linear or non-linear arrangement of the metal centres. Non-linear trinuclear structures could be equilateral or bent.…”