7476-66-6Relevant articles and documents
A π–Cu(II)?π Complex as an Extremely Active Catalyst for Enantioselective α-Halogenation of N-Acyl-3,5-dimethylpyrazoles
Nishimura, Kazuki,Wang, Yanzhao,Ogura, Yoshihiro,Kumagai, Jun,Ishihara, Kazuaki
, p. 1012 - 1017 (2022/01/19)
Novel chiral π–copper(II)?π complex catalyzed enantioselective α-chlorination and -bromination of N-acyl-3,5-dimethylpyrazoles are described. The π–copper(II)?π complexation of Cu(OTf)2 with 3-(2-naphthyl)-l-alanine-derived amides greatly increases the Lewis acidity and triggers the in situ generation of enolate species without an external base, which has a suppressing effect for α-chlorination and -bromination due to undesired halogen bonding. This strategy provides facile access to α-halogenated compounds in high yield with excellent enantioselectivity. X-ray crystallographic and ESR analyses of the catalyst complexes suggest that the release of two counteranions (2TfO–) from the copper(II) center might be crucial for the efficient activation of N-acyl-3,5-dimethylpyrazoles.
Enantioselective α-Chlorination Reactions of in Situ Generated C1 Ammonium Enolates under Base-Free Conditions
Stockhammer, Lotte,Weinzierl, David,B?gl, Thomas,Waser, Mario
, p. 6143 - 6147 (2021/08/18)
The asymmetric α-chlorination of activated aryl acetic acid esters can be carried out with high levels of enantioselectivities utilizing commercially available isothiourea catalysts under base-free conditions. The reaction, which proceeds via the in situ formation of chiral C1 ammonium enolates, is best carried out under cryogenic conditions combined with a direct trapping of the activated α-chlorinated ester derivative to prevent epimerization, thus allowing for enantioselectivities of up to e.r. 99:1.
[3 + 2] Cycloaddition of α-Aryl-α-diazoacetates with Terminal Alkynes via the Cooperative Catalysis of Palladium and Acid
Guo, Hongyu,Zhang, Sheng,Yu, Xiaoqiang,Feng, Xiujuan,Yamamoto, Yoshinori,Bao, Ming
, p. 10789 - 10795 (2021/09/08)
Palladium and acid cooperative catalysis is presented as a strategy for the [3 + 2] cycloaddition of acceptor/donor-type diazo compounds with terminal alkynes. The [3 + 2] cycloaddition of α-aryl-α-diazoacetates with terminal alkynes proceeded smoothly to produce 2,3,5-trisubstituted furans with high yields. This synthesis method provided a direct and efficient pathway to prepare furan ring-containing organosilane and organoboron reagents. Synthetically valuable functional groups such as chloro and bromo atoms, methoxycarbonyl, and carbonyl remained intact during the [3 + 2] cycloaddition reaction.
