Bifunctional N-Heterocyclic Carbene Catalyzed [3+4] Annulation of Enals and Aurones
作者:Zhi-Qin Liang、Zhong-Hua Gao、Wen-Qiang Jia、Song Ye
DOI:10.1002/chem.201405828
日期:2015.1.26
Bifunctional N‐heterocyclic carbenes with a free hydroxy group are demonstrated as efficient catalysts for the [3+4] annulation of enals with aurones to give the corresponding benzofuran‐fused ε‐lactones in good yields with good diastereoselectivities and excellent enantioselectivities. Control experiments reveal that the [3+4] cycloadducts are kinetically favored and could be transformed to the thermodynamically
A regioselective approach for construction of 5-membered and 6-membered flavonoid is established by Pd catalyzed carbonylative cyclization of 2-iodophenol with terminal alkynes using different amine bases under mild reaction condition. The catalytic experiments found that piperazine preferentially accelerate 6-endo cyclization, and triethylamine mediated Pd catalyzed 5-exo cyclization. Under optimized
Palladium-Catalyzed Diastereo- and Enantioselective [3 + 2] Cycloaddition of Vinylcyclopropanes with Azadienes: Efficient Access to Chiral Spirocycles
作者:Kai Liu、Jianfeng Yang、Xiaoxun Li
DOI:10.1021/acs.orglett.0c04062
日期:2021.2.5
azadienes (BDAs) have been widely used as four-atom synthons in transition-metal-mediated cycloaddition reactions, while the exploitation of their reactivity as a two-atom unit to construct spirocycles is still underdeveloped. Herein, we reported the first palladium(0)-catalyzed diastereo- and enantioselective [3 + 2] annulation of vinylcyclopropanes (VCPs) and BDAs. This transformation is featured with
Rhodium-Catalyzed Annulation of α-Imino Carbenes with α,β-Unsaturated Ketones: Construction of Multisubstituted 2,3-Dihydropyrrole/pyrrole Rings
作者:Xueji Ma、Li Liu、Jiaying Wang、Xianglin Xi、Xuemei Xie、Hangxiang Wang
DOI:10.1021/acs.joc.8b01835
日期:2018.12.7
An efficient annulation of α-imino rhodium carbenes with α,β-unsaturatedketones has been developed to generate multisubstituted 2,3-dihydropyrrole derivatives. Using the optimized catalyst, this approach is compatible with both cyclic and normal linear α,β-unsaturatedketones. Further detosylation in the presence of base could produce multisubstituted pyrroles. The new method has the potential to
Highly enantioselective 1, 3-dipolar cycloaddition of 2-arylidene-benzofuran- 3(2H)-ones with imino esters catalyzed by thiourea−quaternary ammonium salts has been developed. This reaction provides efficient construction of a range of chiral spiro[benzofuran-2,3′-pyrrolidine] in high yields (up to 99%) and with good enantioselectivities (up to 99% ee) under mild conditions.