- Hydrogen-Bonding Catalyzed Ring-Closing C?O/C?O Metathesis of Aliphatic Ethers over Ionic Liquid under Metal-Free Conditions
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O-heterocycles have wide applications, and their efficient and green synthesis is very interesting. Herein, we report hydrogen-bonding catalyzed ring-closing metathesis of aliphatic ethers to O-heterocycles over ionic liquid (IL) catalyst under metal- and solvent-free conditions. The IL 1-butylsulfonate-3-methylimidazolium trifluoromethanesulfonate ([SO3H-BMIm][OTf]) is discovered to show outstanding performance, better than the reported catalysts. An interface effect plays an important role in mediating the reaction rate due to the immiscibility between the products and the IL catalyst, and the products can be spontaneously separated. NMR analysis and DFT calculation suggest that a pair of cation and anion of [SO3H-BMIm][OTf] could form three strong H-bonds with an ether molecule, which catalyze the ether transformation via a cyclic oxonium intermediate. A series of O-heterocycles including tetrahydrofurans, tetrahydropyrans, morpholines and dioxane can be obtained from their corresponding ethers in excellent yields (e.g., >99 %). This work opens an efficient and metal-free way to produce O-heterocycles from aliphatic ethers.
- Wang, Huan,Zhao, Yanfei,Zhang, Fengtao,Wu, Yunyan,Li, Ruipeng,Xiang, Junfeng,Wang, Zhenpeng,Han, Buxing,Liu, Zhimin
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supporting information
p. 11850 - 11855
(2020/05/16)
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- Iron-Catalyzed Ring-Closing C?O/C?O Metathesis of Aliphatic Ethers
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Among all metathesis reactions known to date in organic chemistry, the metathesis of multiple bonds such as alkenes and alkynes has evolved into one of the most powerful methods to construct molecular complexity. In contrast, metathesis reactions involving single bonds are scarce and far less developed, particularly in the context of synthetically valuable ring-closing reactions. Herein, we report an iron-catalyzed ring-closing metathesis of aliphatic ethers for the synthesis of substituted tetrahydropyrans and tetrahydrofurans, as well as morpholines and polycyclic ethers. This transformation is enabled by a simple iron catalyst and likely proceeds via cyclic oxonium intermediates.
- Biberger, Tobias,Makai, Szabolcs,Lian, Zhong,Morandi, Bill
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supporting information
p. 6940 - 6944
(2018/05/14)
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- METHOD FOR DEPROTECTING ARYL OR ALKYL SULFONAMIDES OF PRIMARY OR SECONDARY AMINES
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The invention relates to a method for removing an alkyl sulfonyl or aryl sulfonyl protecting group from a primary or secondary amine by contacting an alkyl sulfonamide or an aryl sulfonamide with a Stage 0 or Stage I alkali metal-silica gel material in the presence of a solid proton source under conditions sufficient to form the corresponding amine. The invention also relates to a method for removing an alkyl sulfonyl or aryl sulfonyl protecting group from a primary or secondary amine by a) reacting an alkyl sulfonamide or an aryl sulfonamide with a Stage 0 or Stage I alkali metal-silica gel material, and b) subsequently reacting the reaction product from step a) with an electrophile or a proton source. Preferred Stage 0 or Stage I alkali metal-silica gel materials include Na, K2Na, and Na2K.
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Page/Page column 7
(2009/12/24)
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- Alkali metals in silica gel (M-SG): A new reagent for desulfonation of amines
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(Chemical Equation Presented) A novel method for the desulfonation of secondary amines is described. Alkali metals absorbed into nanostructured silica (M-SG) were found to be useful solid-state reagents for the desuffonation of a range of N,N-disubstituted sulfonamides. M-SG reagents are room-temperature- stable free-flowing powders that retain the chemical reactivity of the parent metal, decreasing the danger and associated cost of using reactive metals.
- Nandi, Partha,Redko, Mikhail Y.,Petersen, Kathryn,Dye, James L.,Lefenfeld, Michael,Vogt, Paul F.,Jackson, James E.
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supporting information; experimental part
p. 5441 - 5444
(2009/06/18)
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- Unsymmetrical 4,6-diamino-2-methyl-5-nitropyrimidine synthesis via 4,6-bis(tosylates)
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Chlorides have traditionally been used as leaving groups for the introduction of 4- and 6-heteroatomic substituents onto pyrimidines. Use of 4,6-dichloro-2-methyl-5-nitropyrimidine allows the sequential introduction of different 4- and 6-heteroatomic substituents onto this core; however, this reagent is highly hazardous to handle. We have found that the analogous 4,6-bis(tosylate) offers a less hazardous substance which undergoes the same nucleophilic aromatic substitution chemistry as the dichloride, including sequential introduction of different nucleophiles.
- Cain, Gary A.,Beck, James P.
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p. 439 - 446
(2007/10/03)
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