In 2022,Iwamoto, Hiroaki; Ozawa, Yu; Hayashi, Yuta; Imamoto, Tsuneo; Ito, Hajime published an article in Journal of the American Chemical Society. The title of the article was 《Conformationally Fixed Chiral Bisphosphine Ligands by Steric Modulators on the Ligand Backbone: Selective Synthesis of Strained 1,2-Disubstituted Chiral cis-Cyclopropanes》.Reference of 1,3-Dimesityl-1H-imidazol-3-ium chloride The author mentioned the following in the article:
C1-sym. P-chirogenic bisphosphine ligands (R)-5,8-Si-Quinox-tBu3 (Silyl = SiMe3, SiEt3, SiMe2Ph) were developed. The bulky silyl modulators attached to the ligand backbone fix the phosphine substituents to form rigid chiral environments that can be used for substrate recognition. The ligand showed high performances for a Cu(I)-catalyzed asym. borylative cyclopropanation of bulky silyl-substituted allylic electrophiles to afford higher disfavored 1,2-cis-silyl-boryl-cyclopropanes than the other possible isomers, trans-cyclopropane and allylboronate (up to 97% yield; 98% ee; cis/trans = >99:1; cyclopropane/allylboronate = >99:1). Detailed computational studies suggested that the highly rigid phosphine conformation, which is virtually undisturbed by the steric interactions with the bulky silyl-substituted allyl electrophiles, is key to the high stereo- and product-selectivities. Also, the detailed computational anal. provided insight into the mechanism of the stereoretention or -inversion of the chiral alkylcopper(I) intermediate in the intramol. cyclization. In the experiment, the researchers used 1,3-Dimesityl-1H-imidazol-3-ium chloride(cas: 141556-45-8Reference of 1,3-Dimesityl-1H-imidazol-3-ium chloride)
1,3-Dimesityl-1H-imidazol-3-ium chloride(cas: 141556-45-8) is a ligand for arylation of aldehydes and for carbene catalyzed intermolecular arylation of C-H bonds. It is used as a phosphine-free ligand in various metal-catalyzed coupling reactions, often with advantageous results in difficult cases.Reference of 1,3-Dimesityl-1H-imidazol-3-ium chloride
Referemce:
Imidazole – Wikipedia,
Imidazole | C3H4N2 – PubChem