Recent advances of mesoionic N-heterocyclic olefins

Abstract

This article highlights the recent advances in the field of mesoionic N-heterocyclic olefins (mNHOs).

Asymmetric Formal Coupling of β-Ketoesters with Quinones Promoted by a Chiral Bifunctional N-Heterocyclic Olefin

“…N -Heterocyclic olefins (NHOs) possess electron-rich and highly polarized exocyclic olefinic double bonds due to the donating property of nitrogen atoms and the effective charge dispersion ability of imidazole rings . These features enabled NHO to not only be used as a ligand but also serve as an organocatalyst to promote a set of organic transformations.…”

Head‐to‐Tail Dimerization of N‐Heterocyclic Diazoolefins

“…This elongation is expected for compounds that classify as 'N-heterocyclic olefins'. [13] The imidazole rings in 1 and 2 are nearly planar, but the central C 2 N 4 rings display a boat conformation. Such a deviation from planarity was predicted theoretically for the parent quinoidal tetrazine H 2 C=(C 2 N 4 )=CH 2 .…”

Copper Complexes with Diazoolefin Ligands and their Photochemical Conversion into Alkenylidene Complexes

“…Utilization of the ionic complex [Cu(CH 3 CN) 4 ](BF 4 ) instead of [Cu(COD)Cl] 2 gave the homoleptic complex 3 in 94 % yield. A CuCl adduct analogous to complex 2 was obtained from the reaction of the triazole-based diazoolefin 4 [13] and [Cu(COD)Cl] 2 .…”

“…The diamagnetic Cu I complexes 2, 3, and 5 were analyzed by NMR-, UV/Vis-, and IR spectroscopy, as well as by single-crystal X-ray diffraction. The metalated Catoms in these complexes give rise to 13 C NMR resonances between 35 and 39 ppm. These values are in line with what has been observed for other diazoolefin complexes.…”