- Role of Organic Fluoride Salts in Stabilizing Niobium Oxo-Clusters Catalyzing Epoxidation
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We present here that easily available organic salts can stabilize/modify niobium (Nb) oxo-clusters. The as-synthesized Nb oxo-clusters have been characterized by various methods. These Nb oxo-clusters were catalytically active for the epoxidation of allylic alcohols and olefins with H2O2 as an oxidant. Notably, Nb-OC@TBAF-0.5 appeared as highly dispersed nanosized particles and showed the highest catalytic activity, which can be attributed to the following reasons on the basis of characterization. First, the strong coordination of fluorine ions with Nb sites and the steric protection with bulky organic cations led to high stabilization and dispersion of the oxo-clusters in the course of the reaction. Second, a hydrogen-bond interaction between the coordinated fluorine atom and the -OH group of allylic alcohol favored the epoxidation reaction. Third, the electron density of Nb sites decreased due to the strong electron-withdrawing ability of F- adjacent to Nb sites, thus promoting the electrophilic oxygen transfer to the CC bond.
- Dai, Sheng,Ding, Bingjie,Gong, Xueqing,Hou, Zhenshan,Li, Difan,Tang, Xuan,Xu, Beibei,Yao, Yefeng,Zhang, Tong,Zheng, Anna,Zhou, Qingqing
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p. 8190 - 8203
(2021/07/26)
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- An azophenol-based chromogenic anion sensor
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(equation presented) A new chromogenic azophenol-thiourea based anion sensor, 2, has been developed. This system allows for the selective colorimetric detection of F-, H2PO4-, and AcO-. Selectivity trends turned out to be dependent upon guest basicity and conformational complementarity between 2 and the guest.
- Lee, Dong Hoon,Lee, Kwan Hee,Hong, Jong-In
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- Cephalosporin derivatives
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A cephalosporin compound represented by the general formula: STR1 This compound exhibits a high antimicrobial activity.
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- 2,3-Dialkoxypropyl glyceryl ether and its preparation process as well as cosmetic composition containing same
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Disclosed herein is a novel 2,3-dialkoxypropyl glyceryl ether and the preparation process for it. The above diglycerin dialkyl ether is readily prepared with high yield and purity by reacting its corresponding glycidyl ether with a protected glycerin to form a 1,3-dioxolan compound, followed by etherifying the thus formed 1,3-dioxolan compound into a dialkyl ether dioxolan compound, and then hydrolyzing the resultant dialkyl ether dioxolan compound. This diglycerin dialkyl ether is useful as an emulsifier, cleaner etc., and is preferably used as a component of cosmetic compositions. A cosmetic composition comprising the above 2,3-dialkoxypropyl glyceryl ether is also disclosed.
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