126079-18-3Relevant articles and documents
Well-Designed Phosphine-Urea Ligand for Highly Diastereo- and Enantioselective 1,3-Dipolar Cycloaddition of Methacrylonitrile: A Combined Experimental and Theoretical Study
Xiong, Yang,Du, Zhuanzhuan,Chen, Haohua,Yang, Zhao,Tan, Qiuyuan,Zhang, Changhui,Zhu, Lei,Lan, Yu,Zhang, Min
supporting information, p. 961 - 971 (2019/01/14)
A novel chiral phosphine-urea bifunctional ligand has been developed for Cu-catalyzed asymmetric 1,3-dipolar cycloaddition of iminoesters with methacrylonitrile, a long-standing challenging substrate in asymmetric catalysis. Distortion-interaction energy analysis based on density functional theory (DFT) calculations reveals that the distortion energy plays an important role in the observed enantioselectivity, which can be attributed to the steric effect between the phosphine ligand and the dipole reactant. DFT calculations also indicate that nucleophilic addition is the enantioselectivity-determining step and hydrogen bonding between the urea moiety and methacrylonitrile assists in control of the diastereo- and enantioselectivity. By a combination of metal catalysis and organocatalysis, excellent diastereo- and enantioselectivities (up to 99:1 diastereomeric ratio, 99% enantiomeric excess) as well as good yields are achieved. A wide range of substitution patterns of both iminoester and acrylonitrile is tolerated by this catalyst system, providing access to a series of highly substituted chiral cyanopyrrolidines with up to two quaternary stereogenic centers. The synthetic utility is demonstrated by enantioselective synthesis of antitumor agent ETP69 with a pivotal nitrile pharmacophore and an all-carbon quaternary stereogenic center.
Multilayer graphene functionalized through thermal 1,3-dipolar cycloadditions with imino esters: A versatile platform for supported ligands in catalysis
Ferrándiz-Saperas, Marcos,Ghisolfi, Alessio,Cazorla-Amorós, Diego,Nájera, Carmen,Sansano, José M.
supporting information, p. 7462 - 7465 (2019/07/04)
Multilayer graphene (MLG), obtained by mild sonication of graphite in NMP or pyridine, was fully characterized via atomic force microscopy (AFM), transmission electron microscopy (TEM), Raman spectroscopy and X-ray photoemission spectroscopy (XPS). Then, it was functionalized via 1,3-dipolar cycloaddition with azomethine ylides generated by thermal 1,2-prototropy of various imino esters. The resulting MLG, containing substituted proline-based amine functions, was characterized by XPS and it showed high nitrogen loading, ranging from 0.6 to 4.2 at% depending on the imino ester used. Among these functionalized MLGs a probe sample was subjected to ester hydrolysis and used as a heterogeneous N,O-chelating ligand to coordinate iridium atomic centers. This supported complex was also characterized by XPS and its catalytic activity was tested in the hydrogen transfer reduction of acetophenone, obtaining up to 85% yield. Furthermore, this catalyst could be recycled up to four times.
Cycloaddition reactions of glycine imine anions to phenylazocarboxylic esters - A new access to 1,3,5-trisubstituted 1,2,4-triazoles
Lasch, Roman,Heinrich, Markus R.
, p. 4282 - 4295 (2015/06/08)
Phenylazocarboxylic tert-butyl esters have recently been shown to be highly versatile building blocks due to their ability to undergo nucleophilic aromatic substitutions under mild conditions, particularly well with [18F]fluoride, and to act as precursors for aryl radicals. In this article, we now report first examples for cycloaddition reactions to phenylazocarboxylates. In a one-pot reaction with readily accessible glycine imines, a variety of highly substituted 1,2,4-triazoles could be obtained.
