Synthesis of Oxazolidinones and Derivatives through Three-Component Fixation of Carbon Dioxide
作者:Congmin Mei、Yibo Zhao、Qianwei Chen、Changsheng Cao、Guangsheng Pang、Yanhui Shi
DOI:10.1002/cctc.201800142
日期:2018.7.19
three‐component fixation of atmospheric CO2 with readily available 1,2‐dichloroethane and aromatic amine toward oxazolidinones catalyzed by in situ NHC was developed. The reaction occurred in good to excellent yields with good generality and wide functional group tolerance, including challenging steric hindered substituted‐dichloroethane (e.g. 1,2‐dichloropropane and 2,3‐dichlorobutane). The catalytic system
Influence of the catalyst structure in the cycloaddition of isocyanates to oxiranes promoted by tetraarylstibonium cations
作者:Mengxi Yang、Nilanjana Pati、Guillaume Bélanger-Chabot、Masato Hirai、François P. Gabbaï
DOI:10.1039/c8dt00702k
日期:——
been evaluated as catalysts for the cycloaddition of oxiranes and isocyanates under mild conditions. While all stibonium cations favor the 3,4-oxazolidinone products, the reactivities of 5+ and 6+ are hindered by the ancillary amino donor which quenches the Lewis acidity of the antimony center. A comparison of the other stibonium cations shows that 4+ is the most selective catalyst.
The reaction of primary aromatic amines with alkylene carbonates for the selective synthesis of bis-N-(2-hydroxy)alkylanilines: the catalytic effect of phosphonium-based ionic liquids
At T ≥ 140 °C, different primary aromatic amines (pX–C6H4NH2; X = H, OCH3, CH3, Cl) react with both ethylene- and propylene-carbonates to yield a chemoselective N-alkylation process: bis-N-(2-hydroxyalkyl)anilines [pX–C6H4N(CH2CH(R)OH)2; R = H, CH3] are the major products and the competitive formation of carbamates is substantially ruled out. At 140 °C, under solventless conditions, the model reaction of aniline with ethylene carbonate goes to completion by simply mixing stoichiometric amounts of the reagents. However, a class of phosphonium ionic liquids (PILs) such as tetraalkylphosphonium halides and tosylates turn out to be active organocatalysts for both aniline and other primary aromatic amines. A kinetic analysis monitored by 13C NMR spectroscopy, shows that bromide exchanged PILs are the most efficient systems, able to impart a more than 8-fold acceleration to the reaction. The reactions of propylene carbonate take place at a higher temperature than those of ethylene carbonate, and only in the presence of PIL catalysts. A mechanism based on the Lewis acidity of tetraalkylphosphonium cations and the nucleophilicity of halide anions has been proposed to account for both the reaction chemoselectivity and the function of the catalysts.
Mechanistic Studies of Tetraphenylstibonium Iodide-Catalyzed Cycloaddition of Oxiranes with Heterocumulenes
作者:Masahiro Fujiwara、Akio Baba、Haruo Matsuda
DOI:10.1246/bcsj.63.1069
日期:1990.4
In the selective α-cleavage cycloaddition of oxiranes with heterocumulenescatalyzed by tetraphenylstibonium iodide, the direction of oxirane fission at first stage is not significant, while the difference of reaction behaviors of two antimony alkoxide intermediates (Ph4SbOCH2CH(R1)I and Ph4SbOCH(R1)CH2I), insertion of heterocumulenes and cyclization to original oxiranes, is responsible for the unusual