1471-04-1Relevant articles and documents
Relative Thermodynamic Stabilities of Isomeric Alkyl Allyl and Alkyl (Z)-Propenyl Ethers
Taskinen, Esko
, p. 11389 - 11394 (1993)
The relative thermodynamic stabilities of ten allyl ethers (ROCH2CH=CH2) and the corresponding isomeric (Z)-propenyl ethers (where R is an alkyl group, or a methoxysubstituted alkyl group) have been determined by chemical equilibration in DMSO solution with t-BuOK as catalyst.From the variation of the equilibrium constant with temperature, the values of the thermodynamic parameters ΔG, ΔH and ΔS of isomerization at 298.15 K were evaluated.The propenyl ethers are highly favored at equilibrium, the values of both ΔG and ΔH for the allyl -> propenyl reaction being ca. -18 to 25 kJ mol-1.The favor of the propenyl ethers is increased by bulky alkyl substituents, and decreased by methoxysubstituted alkyl groups.In most cases the entropy contribution is negligible; however, for R=(MeO)2CH and R=(MeO)3C the values of ΔS are ca. -5 J K-1 mol1-.
Clean protocol for deoxygenation of epoxides to alkenes: Via catalytic hydrogenation using gold
Fiorio, Jhonatan L.,Rossi, Liane M.
, p. 312 - 318 (2021/01/29)
The epoxidation of olefin as a strategy to protect carbon-carbon double bonds is a well-known procedure in organic synthesis, however the reverse reaction, deprotection/deoxygenation of epoxides is much less developed, despite its potential utility for the synthesis of substituted olefins. Here, we disclose a clean protocol for the selective deprotection of epoxides, by combining commercially available organophosphorus ligands and gold nanoparticles (Au NP). Besides being successfully applied in the deoxygenation of epoxides, the discovered catalytic system also enables the selective reduction N-oxides and sulfoxides using molecular hydrogen as reductant. The Au NP catalyst combined with triethylphosphite P(OEt)3 is remarkably more reactive than solely Au NPs. The method is not only a complementary Au-catalyzed reductive reaction under mild conditions, but also an effective procedure for selective reductions of a wide range of valuable molecules that would be either synthetically inconvenient or even difficult to access by alternative synthetic protocols or by using classical transition metal catalysts. This journal is
Efficient synthesis of tert-butyl ethers under solvent-free conditions
Rai, Neithnadka Premsai,Arunachalam, Pirama Nayagam
, p. 2891 - 2896 (2008/02/13)
A simple and efficient synthesis of tert-butyl ethers from various alcohols and substituted phenols using tert-butyl bromide in the presence of basic lead carbonate as a catalyst. The catalyst is easily recovered via filtration and can be reused up to three times without appreciable loss of activity. Copyright Taylor & Francis Group, LLC.
Rhenium-Catalyzed Epoxide Deoxygenation: Scope and Limitations
Gable, Kevin P.,Brown, Eric C.
, p. 2243 - 2245 (2007/10/03)
Transfer of oxygen atoms from epoxides to triphenylphosphine is efficiently catalyzed by Tp′ReO3 [Tp′ = hydrido-tris-(3,5-dimethylpyrazolyl)borate] in benzene at 75-105 °C. The reaction tolerates a wide variety of functional groups including ketones (conjugated or non-conjugated to the new double bond), esters, nitriles, ethers, silyl ethers and phthalimides. Relative rates vary with substitution pattern and electronics; in general, monosubstituted and 2,2-disubstituted epoxides react fastest, and cis-2,3-disubstituted systems react faster than trans. Electron-withdrawing substituents promote the reaction.