Helical Poly(quinoxaline‐2,3‐diyl)s Bearing 1,2,3‐Triazole Pendants: Synthesis by CuAAC and Use as Reusable Abnormal NHC Ligands in Gold Catalysis

Abstract

Poly(quinoxaline‐2,3‐diyl)s (PQXs) bearing 1,2,3‐triazole pendants were synthesized by living copolymerization of achiral 1,2‐diisocyanobenzenes or by post‐polymerization functionalization of PQXs bearing alkyne pendants through copper‐catalyzed azide–alkyne cycloaddition. Thus prepared PQXs bearing 1,2,3‐triazole pendants were treated with MeI, Ag2O, and AuCl successively, giving polymer‐supported gold complexes bearing 1,2,3‐triazolylidenes as abnormal N‐heterocyclic carbene (aNHC) ligands. The polymer‐based aNHC ligand served as a catalyst for the reaction of styrene with a propargylic ester to form a cyclopropane derivative. The catalyst could be reused at least eight times without loss of activity.

Screw sense and screw sensibility: communicating information by conformational switching in helical oligomers

“…Thus PQXs decorated with triarylphosphines catalyse atroposelective Suzuki-Miyaura couplings, 61 those with oxazaborolidines catalyse enantioselective C-C bond cleavage, 66 and those with N-heterocyclic carbenes catalyse enantioselective cyclopropanation of olefins. 67 Helical poly(acetylene)s adorned with axially chiral 2,2 0bis(methoxymethoxy)biphenyls display helical chirality. Maeda and co-workers discovered that the screw-sense can be quantitatively induced by treatment with chiral secondary alcohols.…”

“…Thus PQXs decorated with triarylphosphines catalyse atroposelective Suzuki–Miyaura couplings, 61 those with oxazaborolidines catalyse enantioselective C–C bond cleavage, 66 and those with N-heterocyclic carbenes catalyse enantioselective cyclopropanation of olefins. 67 …”

Azide-Alkyne Click Chemistry over a Heterogeneous Copper-Based Single-Atom Catalyst

“…The three-component reactions prototypically occur in the presence of homogeneous catalysts based on copper. Over the last two decades, catalytic systems featuring the use of a wide variety of ancillary ligands, including phosphines, N-heterocyclic carbenes, bipyridines, and acyclic diaminocarbenes, have been successfully reported. − Due to their uniform and well-defined active sites, these homogeneous catalysts show remarkable selectivity and a high turnover frequency. However, they also suffer from practical issues such as rapid catalyst deactivation and product contamination with metal residues, that challenge the recovery and reuse of the homogeneous catalyst .…”

Chiral Self‐Sorting of Diformylated N‐Hetero‐ortho‐phenylene Hexamers by Macrocyclization with Aromatic Diamines

“…Artificial helical oligomers and polymers have been offered useful chiral space which can be applied to chiral catalysts, [1][2][3] chiral stationary phases in chromatography, [4][5][6] and circularly polarized luminescence. [7][8][9][10][11][12][13][14][15] Especially among them, dynamic helical molecules are expected to be stimuli responsible materials due to interconvertible right-and left-handed helical conformations.…”