Research article:

Titanium-Oxide Host Clusters with Exchangeable Guests

Guanyun Zhang, Wenyun Li, Caiyun Liu, Jiong Jia, Chen-Ho Tung , and Yifeng Wang*
J. Am. Chem. Soc., DOI: 10.1021/jacs.7b10565

[Abstract] A novel family of water-soluble, polyoxocationic titanium-oxide host–guest clusters are reported herein. They exhibit an unprecedented hexagonal prismatic core structure for hosting univalent cationic guests like K+, Rb+, Cs+ and H3O+. Guest exchange has been studied using 133Cs NMR, showing the flexible pore of a host permits passage of a comparatively larger cation and giving an equilibrium constant of ca. 13 for displacing Rb+ by Cs+. Attractive ion-dipole interaction, depending on host–guest size complementarity, plays a dominant role for the preferential encapsulation of larger alkali-metal cationic guests. [View details......]

ACS Catal. Research Article
Iodine/Visible Light Photocatalysis for Activation of Alkynes for Electrophilic Cyclization Reactions
Yuliang Liu, Bin Wang, Xiaofeng Qiao, Chen-Ho Tung , and Yifeng Wang*
ACS Catal., 2017, 7, pp 4093–4099

[Abstract] Photocatalytic organic synthesis needs photocatalysts to initiate the reactions and to control the reaction paths. Available photocatalytic systems rely on electron transfer or energy transfer between the photoexcited catalysts and the substrates. We explore a concept based on the photopromoted catalyst coupling to the substrate and the phototriggered catalyst regeneration by elimination from the catalytic cycle. A catalytic amount of elementary I2 is applied as both a visible light photocatalyst and a π Lewis acid, enabling the direct activation of alkyne C≡C bonds for electrophilic cyclization reactions, one of the most important reactions of alkynes. Visible light is crucial for both the iodocyclization of the propargyl amide and the deiodination of the intermediate. Singlet oxygen is found to play a key role in the regeneration of I2. This system shows good functional group compatibility for the generation of substituted oxazole aldehydes and indole aldehydes. Hence, this study provides a readily accessible alternative catalytic system for the construction of heterocycle aldehyde derivatives by sunlight photocatalysis. [View more......]

Published in Inorganic Chemistry, 2016 Mar 05.

The article reports that weak adsorbents (universal in solutions) can substaintially affect the catalytic reactions of strong adsorbents in catalysis.

 

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Address: School of chemistry, Shandong univerisity, Jinan, China