15045-43-9Relevant academic research and scientific papers
Straightforward synthesis of rubidium bis(trimethylsilyl)amide and complexes of the alkali metal bis(trimethylsilyl)amides with weakly coordinating 2,2,5,5-tetramethyltetrahydrofuran
Krieck, Sven,Schüler, Philipp,G?rls, Helmar,Westerhausen, Matthias
, p. 12562 - 12569 (2018)
Rubidium bis(trimethylsilyl)amide (rubidium hexamethyldisilazanide, Rb(hmds)) is accessible on a large scale with excellent yields via a magnetite-catalyzed metalation of hexamethyldisilazane (H(hmds)) in liquid ammonia. Recrystallization of solvent-free alkali metal hexamethyldisilazanides [A(hmds)]n of sodium to cesium from solutions containing 2,2,5,5-tetramethyltetrahydrofuran (Me4THF, thf?) yields the dinuclear complexes [(thf?)A(hmds)]2, which show a rather asymmetric coordination behavior of the bulky ether ligand with strongly bent A-A-O moieties for the heavier K, Rb, and Cs congeners, whereas in the Na complex, the ether ligand is clamped between the trimethylsilyl groups. In hydrocarbon solutions, dissociation of these compounds is observed leading to the liberation of this bulky and weakly binding cyclic ether.
Solvation effects on stereochemistry of reduction of 3,3,5-trimethylcyclohexanone with lithium aluminum tri-t-butoxyhydride
Haubenstock,Hong
, p. 2445 - 2447 (1978)
Specific solvation effects on stereoselectivity in the reduction of a cyclohexanone by lithium aluminum tri-t-butoxyhydride have been studied by adding measured quantities of diethyl ether, tetrahydrofuran (THF) and methyl-substituted tetrahydrofurans to benzene solvent, and various amounts of THF to diethyl ether solvent. A steric hindrance effect in the case of bulky addends was observed, and a significant increase in stereoselectivity for less bulky addends was found. The results have been explained in terms of complexing, or steric hindrance to complexing, of the lithium cation.
PREPARATION OF TMTHF
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Page/Page column 5; 6, (2018/03/09)
The invention relates to a process for the preparation of 2,2,5,5- tetramethyltetrahydrofuran (TMTHF) comprising contacting a TMTHF precursor with a solid catalyst, wherein the TMTHF precursor is 2,5-dimethylhexane-2,5-dioland/or 2,5-dimethyl-4- hexen-2-ol,and wherein the solid catalyst is a beta zeolite. It also relates to the use of a beta zeolite catalyst for this process. It also relates to the use of the TMTHF produced by the process of the invention as solvent.
2,2,5,5-Tetramethyltetrahydrofuran (TMTHF): A non-polar, non-peroxide forming ether replacement for hazardous hydrocarbon solvents
Byrne, Fergal,Forier, Bart,Bossaert, Greet,Hoebers, Charly,Farmer, Thomas J.,Clark, James H.,Hunt, Andrew J.
supporting information, p. 3671 - 3678 (2017/08/15)
An inherently non-peroxide forming ether solvent, 2,2,5,5-tetramethyltetrahydrofuran (2,2,5,5-tetramethyloxolane), has been synthesized from readily available and potentially renewable feedstocks, and its solvation properties have been tested. Unlike traditional ethers, its absence of a proton at the alpha-position to the oxygen of the ether eliminates the potential to form hazardous peroxides. Additionally, this unusual structure leads to lower basicity compared with many traditional ethers, due to the concealment of the ethereal oxygen by four bulky methyl groups at the alpha-position. As such, this molecule exhibits similar solvent properties to common hydrocarbon solvents, particularly toluene. Its solvent properties have been proved by testing its performance in Fischer esterification, amidation and Grignard reactions. TMTHF's differences from traditional ethers is further demonstrated by its ability to produce high molecular weight radical-initiated polymers for use as pressure-sensitive adhesives.
Cyclization of alkanediols in high-temperature liquid water with high-pressure carbon dioxide
Yamaguchi, Aritomo,Hiyoshi, Norihito,Sato, Osamu,Shirai, Masayuki
experimental part, p. 302 - 305 (2012/07/28)
Dehydration of 1,4-butanediol (1,4-BDO) to tetrahydrofuran (THF), 2R,5R-hexanediol (2R,5R-HDO) to 2,5-dimethyltetrahydrofuran (2,5-DMTHF), and 2,5-dimethyl-2,5-hexanediol (2,5-DM-2,5-HDO) to 2,2,5,5- tetramethyltetrahydrofuran (2,2,5,5-TMTHF) proceeded in high-temperature liquid water at 523 K. The formation rates of cyclic ethers were enhanced by high-pressure carbon dioxide (16.2 MPa). The order of dehydration rates in high-temperature water with carbon dioxide was 2,5-DM-2,5-HDO > 2R,5R-HDO > 1,4-BDO (tertiary > secondary > primary alcohols), which was the same order as the stability of corresponding carbocation species.
Some properties of cyclic phosphoramidites and their phosphites: Phosphitylation, ester exchange, and hydrolysis
Watanabe, Yutaka,Maehara, Shin-Ich
, p. 799 - 810 (2007/10/03)
Phosphorylation of diols using sterically bulky cyclic phosphoramidites was performed in a good selectivity. Their phosphite derivatives underwent tetrazole-catalyzed hydrolysis and transesterification. The reaction was shown to proceed via a phosphorane intermediate by NMR analysis.
Reactions of Some Cyclic Ethers in Superacids
Baig, Mirza Azam,Banthorpe, Derek V.,Carr, Graham,Whittaker, David
, p. 1981 - 1986 (2007/10/02)
The reactions of some epoxides and tetrahydrofuran derivatives in superacidic media have been studied.The tetrahydrofurans decompose only at 0 deg C or above, yielding, in some cases, unsaturated carbocations which react to give carbocyclic products, though many yield only tar.Cyclohexene oxides decompose more readily; unsubstituted, they slowly form an allylic ion; with one carbon at the epoxide link substituted they yield the ketone, and with both carbons substituted they give the ring-contracted aldehyde.Limonene 1,2-oxide behaves in a similar manner, though yielding small amounts of the ring-contracted protonated aldehyde (10).Reaction of geraniol 2,3-oxide is initially similar but the intermediate is intercepted intramolecularly to yield the hydroxy-iridoid ethers, 3,3,6β-trimethyl-cis-perhydrocyclopentafuran and 3,3,6α-trimethyl-cis-perhydrocyclopentafuran.Protonation of cyclohexene oxide or norbornene oxide yields onium salts, stable at -70 deg C, which show the addition to be either unsymmetrical (i.e. edge protonation) or to take place in two different positions.
Cyclodehydration of Non-aromatic Diols on Al(III)-Montmorillonite Clay: Reactivity and Mechanism
Kotkar, Dilip,Mahajan, Satish W.,Mandal, Arun K.,Ghosh, Pushpito K.
, p. 1749 - 1752 (2007/10/02)
Al(III)-Montmorillonite-catalysed reactions of non-aromatic diols and butane-1,4-dithiol into the corresponding heterocyclic compounds are described.Experiments with S-(+)-pentane-1,4-diol indicate a mechanism involving competitive protonation of the primary and secondary hydroxy groups, followed by SN2 displacement of water to form the cyclic product.A comparison of the relative catalytic efficiencies of Al(III)-montmorillonite and the corresponding alumina pillared clay suggests that the performance of the former is superior in the above acid-catalysed reactions.
STUDIES ON THE CHEMISTRY OF DIOLS AND CYCLIC ETHERS-52. MECHANISM AND STEREOCHEMISTRY OF DEHYDRATION OF OXOLANES TO DIENES
Molnar, Arpad,Bartok, Mihaly
, p. 131 - 142 (2007/10/02)
On γ-Al2O3, BPO4 and NaX zeolite, the dehydration of (+/-)-2,2,3,4,5,5-hexamethyloxolane (2) in the vapour phase leads to the formation of 2,3,4,5-tetramethyl-1,5-hexadiene (8) in a slow process, while meso-2,2,3,4,5,5-hexamethyloxolane (3) is converted to 2,3,4,5-tetramethyl-2,4-hexadiene (7) with high selectivity in a fast reaction.These differences in reaction rate and selectivity indicate that the dehydration of 2 takes place by an E2 mechanism.In contrast, the steric strain in 3 results in ring opening by an E1 mechanism.These conclusions are supported by the nonselective transformations of 2,2,5,5-tetramethyloxolane (1) and 2,2,6,6-tetramethyloxane (4), and the dehydration of 1, 2 and 3 in the presence of formic acid in the liquid phase.The experimental observation prove that both the reactivity and the reaction directions in the dehydration of stereoisomeric oxolanes are determined by steric factors.
