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
With the aid of a class of newly discovered Trost-type bisphosphine ligands bearing a chiral cycloalkane framework, the Pd-catalyzed decarboxylative dearomative asymmetric allylic alkylation (AAA) of benzofurans was achieved with high efficiency [0.2-1.0 mol% Pd2(dba)3/L], good generality and high enantioselectivity (> 30 examples, 82-99% yield and 90-96% ee). Moreover, a diversity-oriented synthesis
Azonanes were prepared by a palladium-catalyzed (5 + 4) cycloaddition between activated vinylcyclopropanes and 1-azadienes. During this process, the vinylcyclopropane partner displayed an unusual reactivity and behaved as an all-carbon 1,5-dipole. A N,N-bidentate ligand was required to inhibit the formation of thermodynamic (3 + 2) cycloadducts.
Highly Regio‐, Diastereo‐, and Enantioselective Synthesis of Tetrahydroazepines and Benzo[
<i>b</i>
]oxepines through Palladium‐Catalyzed [4+3] Cycloaddition Reactions
作者:Barry M. Trost、Zhijun Zuo
DOI:10.1002/anie.201911537
日期:2020.1.13
A novel Pd0 -catalyzed asymmetric [4+3] annulation reaction of two readily accessible starting materials has been developed for building seven-membered heterocyclic architectures. The potential [3+2] side pathway could be suppressed though fine tuning of the conditions. A broad scope of cycloaddition donors and acceptors participated in the transformation with excellent chemo-, regio-, diastereo-,