18403-22-0Relevant articles and documents
Hafnium Triflate as a Highly Potent Catalyst for Regio- and Chemoselective Deprotection of Silyl Ethers
Zheng, Xiu-An,Kong, Rui,Huang, Hua-Shan,Wei, Jing-Ying,Chen, Ji-Zong,Gong, Shan-Shan,Sun, Qi
, p. 944 - 953 (2019/02/10)
As a Group IVB transition metal Lewis acid, hafnium triflate [Hf(OTf) 4 ] exhibited exceptionally high potency in desilylations. Since the amounts of Hf(OTf) 4 required for the deprotection of 1°, 2°, 3° alkyl and aryl tert -butyldimethylsilyl (TBS) ethers are significantly different, ranging from 0.05 mol% to 3 mol%, regioselective deprotection of TBS could be easily implemented. Moreover, chemoselective cleavage of different silyl ethers or removal of TBS in the presence of most hydroxyl protecting groups was also accomplished. NMR analyses of silyl products from TBS deprotection indicated that Hf(OTf) 4 -catalyzed desilylation may proceed via different mechanisms, depending on the solvent used.
Hafnium trifluoromethanesulfonate catalyzed silyl ether protecting group removing method
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Paragraph 0009; 0013; 0014, (2019/01/21)
The invention provides a hafnium trifluoromethanesulfonate catalyzed silyl ether protecting group removing method. Various silyl ether protecting groups of nearly 50 kinds of substrates can be efficiently removed in 0.5-16 hours at room temperature by taking 0.02mol%-0.3mol% hafnium trifluoromethanesulfonate as a catalyst, a silyl ether protected hydroxyl compound as a substrate and conventional AR methanol as a solvent. 42 kinds of silyl ether protecting group removing products can be obtained at high yield by performing conventional slica column chromatography purification on a crude product. By regulating the use amount of the catalyst, the Hf(OTf)4 catalyst can realize regioselective removal of 1-degree, 2-degree and 3-degree alkyl TBS and aryl TBS protective groups. Moreover, in a proper equivalent scope, the Hf(OTf)4 catalyst can also realize 1) chemoselective removal of different kinds of silica-based protective groups; and 2) chemoselective removal of 1-degree TBS protective groups under the condition of not affecting a majority of common hydroxyl protective groups.
Regioselective ring opening of exo- and endo-3,4-benzylidene acetals of arabinopyranoside derivatives with Lewis acids and reducing agents
Rujirawanich, Janjira,Kongkathip, Boonsong,Kongkathip, Ngampong
experimental part, p. 927 - 932 (2011/06/20)
Dioxolane type 3,4-benzylidene acetals of benzyl β-l-arabinose either as a mixture or pure exo- and endo-isomers cleavaged with BF3· OEt2/Et3SiH in dichloromethane or acetonitrile regioselectively, provided the 4-O-benzyl-
