Epoxidation–alcoholysis of cyclic enol ethers catalyzed by Ti(O<sup>i</sup>Pr)<sub>4</sub>or Venturello's peroxophosphotungstate complex
作者:Pieter Levecque、David Gammon、Henok Hadgu Kinfe、Pierre Jacobs、Dirk De Vos、Bert Sels
DOI:10.1039/b705244h
日期:——
Venturello's peroxophosphotungstate compound and Ti(OiPr)4 were successfully used as catalysts for the epoxidationâalcoholysis of various dihydropyrans and dihydrofuran using H2O2 as the oxidant. Different alcohols can be used as solvents and nucleophiles, resulting in hydroxy ether products with varying alkoxy groups. The Venturello compound can also be used as catalyst in a biphasic conversion of dihydropyran, in which long chain alcohols or fatty acids are incorporated in the hydroxy ether products with high yield and (stereo)selectivity.
Tandem Epoxidation‐Alcoholysis or Epoxidation‐Hydrolysis of Glycals Catalyzed by Titanium(IV) Isopropoxide or Venturello’s Phosphotungstate Complex
作者:Pieter Levecque、David W. Gammon、Henok Hadgu Kinfe、Pierre Jacobs、Dirk De Vos、Bert Sels
DOI:10.1002/adsc.200800079
日期:2008.7.7
Venturello’sphosphotungstatecomplex and titanium(IV) isopropoxide [Ti(O-i-Pr)4] were successfully used as catalysts for the epoxidation-alcoholysis of glycals using hydrogen peroxide [H2O2]. Reaction substrates included a range of variously protected glycals and different alcohols were used as solvents. Ti(O-i-Pr)4 was only effective in methanol as solvent, but gave methyl glycosides in high yields
Venturello的磷钨酸盐络合物和异丙醇钛(IV)[Ti(O- i- Pr)4 ]已成功用作使用过氧化氢[H 2 O 2 ]的环氧乙烷缩合醇解的催化剂。反应底物包括各种受保护的糖基,不同的醇用作溶剂。钛(O- i- Pr)4仅在甲醇作为溶剂中有效,但以高收率和高选择性得到甲基糖苷。事实证明,Ventrollo复合物是一种用途广泛且高效的催化剂。除了在醇类溶剂中进行环氧化-醇解以外,它还显示了在双相条件下的活性,以允许长链醇的糖基化,并且在苄基化的葡糖的立体选择性二羟基化中非常有效。
Stereoselective template-directed C-glycosidation. Synthesis of bicyclic ketooxetanes via intramolecular cyclization reactions of (2-pyridylthio)glycosidic silyl enol ethers
作者:Donald Craig、V. Ranjit N. Munasinghe
DOI:10.1039/c39930000901
日期:——
Bicyclic ketooxetanes 5a, 5b and 8 are formed with excellent stereoselectivity on treatment of (2-pyridylthio)glycosidic silyl enol ethers 1a, 1b and 2 with silver(I) trifluoromethanesulfonate.
Metal-free Hydroalkoxylation-Formal [4+2] Cycloaddition Cascade for the Synthesis of Ketals
作者:Santosh J. Gharpure、Santosh K. Nanda、Padmaja、Yogesh G. Shelke
DOI:10.1002/chem.201701659
日期:2017.7.26
A transition metalfree, acid promoted cascade hydroalkoxylation–formal [4+2] cycloaddition of various alkynols with salicylaldehyde is demonstrated for the synthesis of tetrahydrofurano/pyrano‐chromenes and spiroketals. In general, alkynols underwent hydroalkoxylations in an endo‐dig manner when internal alkynes were used to furnish the heteroannular ketals, whereas terminal alkynes proceeded in an
Cyclization of Aryl Silanes with Unexpected Retention of Silicon
作者:Stephen Philip Fearnley、Michael W. Tidwell
DOI:10.1021/ol026494h
日期:2002.10.1
[formula: see text] IntramolecularFriedel-Craftscyclization of 2-O-benzyl ethers at a model pyranose acetal is activated by incorporation of a trimethylsilyl group, albeit via unexpected, presumably steric means.