Publications

147.Evolution of Pauson-Khand Reaction: Strategic Applications in Total Syntheses of Architecturally Complex Natural Products (2016–2020)

Sijia Chen†, Chongguo Jiang†, Nan Zheng, Zhen Yang* and Lili Shi*

Catalysts, 2020, 10 (10), 1199

Metal-mediated cyclizations are important transformations in a natural product total synthesis. The Pauson-Khand reaction, particularly powerful for establishing cyclopentenone-containing structures, is distinguished as one of the most attractive annulation processes routinely employed in synthesis campaigns. This review covers Co, Rh, and Pd catalyzed Pauson-Khand reaction and summarizes its strategic applications in total syntheses of structurally complex natural products in the last five years. Additionally, the hetero-Pauson-Khand reaction in the synthesis of heterocycles will also be discussed. Focusing on the panorama of organic synthesis, this review highlights the strategically developed Pauson-Khand reaction in fulfilling total synthetic tasks and its synthetic attractiveness is aimed to be illustrated.

146.Synthesis of 4-Desmethyl-Rippertenol and 7-Epi-Rippertenol via Photoinduced Cyclization of Dienones

Zi-Chun Zhang†, Dan-Dan Zhao†, Zhong-Chao Zhang, Xin-Yu Tan, Jian-Xian Gong*, Jun-Kai Fu* & Zhen Yang*

Chinese Chemical Society, 2020, 2(5), 2074–2083

The synthesis of cycloheptanoid-based fused polycyclic frameworks is a challenge for organic chemists due to unfavorable entropic factors and ring strains. Herein, a concise synthesis of 4-desmethyl-rippertenol and 7-epi-rippertenol bearing a unique, [6,6,5,7]-fused tetracyclic framework is reported. The route features a novel photoinduced intramolecular cyclization of α-cyclopropyl dienone followed by an unexpected thermal 1,5-hydrogen migration, which provides efficient access to the fused seven-membered ring system in a stereochemically well-defined manner. Further density functional theory (DFT) calculations disclose that the stereoselectivity of this photoinduced process is mainly attributed to transition state conformation and steric effects.

145.Asymmetric Total Synthesis of (−)-Spirochensilide A

Xin-Ting Liang, Jia-Hua Chen,* and Zhen Yang*

J. Am. Chem. Soc. 2020, 142(18), 8116–8121

An asymmetric total synthesis of (−)-spirochensilide A has been achieved for the first time. The synthesis features a semipinacol rearrangement reaction to stereoselectively construct the two-vicinal quaternary chiral centers at C8 and C10, a tungsten-mediated cyclopropene-based Pauson–Khand reaction to install the C13 quaternary chiral center, and a furan-based oxidative cyclization to stereoselectively form the spiroketal motif.

144.Photoredox‐Catalyzed Isomerization of Highly‐Substituted Allylic Alcohols via C‐H bond activation

Kai Guo, Zhongchao Zhang, Anding Li, Yuanhe Li, Jun Huang,* Zhen Yang,*

Angew. Chem. Int. Ed.2020, 59(28), 11660-11668

•C−H Activation | Hot Paper 

Photoredox‐catalyzed isomerization of γ‐carbonyl‐substituted allylic alcohols to their corresponding carbonyl compounds was achieved for the first time via C‐H bond activation . This catalytic redox‐neutral process provided a way for the synthesis of 1,4‐dicarbonyl compounds. Notably, allylic alcohols bearing tetrasubstituted olefins can also be transferred into their corresponding carbonyl compounds. The density functional theory calculations show that the carbonyl group at the γ‐position of allylic alcohols are beneficial to the formation of their corresponding allylic alcohol radicals with high vertical electron affinity, which contributes to the completion of the photoredox catalytic cycle.

143.Asymmetric Total Synthesis of (+)-Waihoensene

Yongzheng Qu, Zheyuan Wang, Zhongchao Zhang, Wendou Zhang, Jun Huang,* and Zhen Yang*

J. Am. Chem. Soc. 2020, 142(14), 6511-6515

• Highlighted in ChemistryViews, 07 Apr 2020

The asymmetric total synthesis of (+)-waihoensene, which has a cis-fused [6,5,5,5] tetracyclic core bearing an angular triquinane, a cis-fused six-membered ring, and four contiguous quaternary carbon atoms, was achieved through a sequence of chemical reactions in a stereochemically well-defined manner. The total synthesis features the following: (1) Cu-catalyzed asymmetric conjugated 1,4-addition; (2) diastereoselective Conia-ene type reaction; (3) diastereoselective intramolecular Pauson–Khand reaction; (4) Ni-catalyzed diastereoselective conjugated 1,4-addition; and (5) radical-initiated intramolecular hydrogen atom transfer (HAT). Control experiments and density functional theory calculations support the proposed HAT process.