Synthesis of BINAM‐Based Chiral Di‐1,2,3‐triazolylidene Complexes and Application of the Di‐NHC Rh^I Catalyst in Enantioselective Hydrosilylation

Abstract

Despite the prolific use of (di-)NHC complexes in homogeneous catalysis, there are relatively few reports on their successful application in asymmetric transformations. In this work the atropisomeric binaphthyl backbone was combined with readily obtainable 1,2,3-triazolylidenes to develop a strongly electron-donating C 2 -symmetric ligand. The ligand was efficiently synthesized in a three-step procedure in an overall yield of 91 % starting from commercially available[a] Van 'Scheme 1. Synthesis of the chiral ditriazolium salt 3.

Mesoionic and Related Less Heteroatom-Stabilized N-Heterocyclic Carbene Complexes: Synthesis, Catalysis, and Other Applications

“…44 The silver complex 2 also contains a ditriazolylidene ligand yet lacks chelating groups and therefore forms a dinuclear structure. 45 Related diand tris-triazolylidene ligands like the bi(naphthylamine)based ditriazolylidene silver complex 3 46 and complex 4 with a rigid triphenylbenzene core also form cationic silver complexes of type [Ag(trz) 2 ] + , with the latter ligand system forming a 2:3 ligand:metal assembly that shapes up into a macromolecular cylinder. 47 In recent years, also simpler triazolylidene silver complexes have been reported.…”

“…59 In contrast, the metal precursor [PdCl 2 (NCR) 2 ] favors the formation of the bis(triazolylidene) complexes [PdCl 2 (trz) 2 ], generally as mixtures of trans and cis isomers 12 and 13, respectively, with the trans isomer as the major species. 46,48,50,52,54,57,122 Since the dissymmetric triazolylidene in these complexes is oriented essentially orthogonally with respect to the palladium coordination plane, these complexes exist as mixtures of syn and anti conformers. 59 When the same palladium precursor [PdCl 2 (NCR) 2 ] is added in the presence of NaI or another halide additive, the dimeric species 14 with bridging halide ligands is obtained.…”

Crystal structure of 1-((R)-(2′-(dimethylamino)-[1,1′-binaphthalen]-2-yl))-3-((S)-2-hydroxy-1-phenylethyl)thiourea, C31H29N3OS

“…In recent decades, chiral thiourea organocatalysts have attracted much attention due to their powerful catalytic activity [4][5][6][7]. Meanwhile, C2 symmetric compounds represented by binaphthylamine is an important class of chiral ligands [8,9], resolving agents [10] and catalysts [11]. Thus, the thiourea catalysts based on the binaphthyl skeleton own an efficient catalytic effect in many asymmetric synthesizes [12][13][14].…”

Rh(I) Complexes in Catalysis: A Five-Year Trend

“…The series of novel ligands for Rh(I) catalyzed reactions includes a BINAM-based chiral di-1,2,3-triazolylidene, which was then deprotonated in the presence of a Rh(I) precursor to give the expected complex [53] (Figure 2). The aim of the study was to test the compound in the rhodium-catalyzed hydrosilylation reaction.…”