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, Accepted Articles

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.

142.Asymmetric Total Synthesis of (−)-Guignardones A and B

Zhiming Yan, Chunbo Zhao, Jianxian Gong,* and Zhen Yang*

Org. Lett. 2020, 22(4), 1644-1647

The asymmetric total synthesis of (−)-guignardones A (2) and B (1) has been accomplished. The highly oxidized 6-oxabicyclo[3.2.1]octane core was constructed from d-quinic acid via substitution/desulfurization reaction with thiophenol to forge the bridged ring scaffold, and a Pummerer rearrangement and 1,4-addition/elimination sequence was employed to install the β-carbonyl group at the congested C-1 position. A late-stage Knoevenagel condensation–6π-electrocyclization and directed hydrogenation formed (−)-guignardone B (1), which was subjected to dehydration to furnish (−)-guignardone A (2).

141.Protecting-Group-Free Total Syntheses of (±)-Norascyronones A and B

Tingting Cao, Lei Zhu, Yu Lan*, Jun Huang* and Zhen Yang*

Org. Lett. 2020, 22(7), 2517-2521

Protecting-group-free total syntheses of natural products norascyronone A and norascyronone B were accomplished in eight steps from the commercially available starting material 1-bromo-4-methoxy-2-methylbenzene. The key step was a Mn/Cu-mediated oxidative cascade annulation reaction that formed the tetracyclic core of the target molecules bearing vicinal bridge-head all-carbon quaternary chiral centers. Our investigation indicated that the C5 stereogenic center of norascyronone C plays a critical role in the proposed biomimetic oxidative reaction for B-ring formation.


140.Retro-metal-ene versus retro-Aldol: mechanistic insight into Rh-catalysed formal [3+2] cycloaddition

Song Liu, Tao Zhang, Lei Zhu, Kangbao Zhong, Jianxian Gong, Zhen Yang*, Ruopeng Bai*, Yu Lan*

Chem. Commun., 2018,54(96), 13551-13554

Theoretical calculations have been performed to investigate the mechanism and stereoselectivity of rhodium-catalysed intramolecular [3+2] cycloaddition for construction of a substituted hexahydropentalene complex. A new C–C bond cleavage mechanism, retro-Aldol-type, is proposed and verified for this Rh-catalysed [3+2] cycloaddition reaction.