481-21-0Relevant articles and documents
ASTEROSAPONIN P1 FROM THE STARFISH PATIRIA PECTINIFERA
Kicha, A. A.,Kalinovsky, A. I.,Levina, E. V.,Stonik, V. A.,Elyakov, G. B.
, p. 3893 - 3896 (1983)
A novel steroidal glycoside has been isolated from the starfish Patiria pectinifera and its structure was determined as 5'-O-sulfate 24-(α-3-O-methyl-L-arabinofuranosyl)-3β,6α,8β,15α,24ξ-pentaoxy-5α-cholestane.
Defunctionalization of sp3 C–Heteroatom and sp3 C–C Bonds Enabled by Photoexcited Triplet Ketone Catalysts
An, Juzeng,Gu, Yiting,Martin, Ruben,Wakeling, Matthew,Yin, Hongfei
, p. 1031 - 1036 (2022/01/19)
A general strategy for enabling a light-induced defunctionalization of sp3 C–heteroatom and sp3 C–C bonds with triplet ketone catalysts and bipyridine additives is disclosed. This protocol is characterized by its broad scope without recourse to transition metal catalysts or stoichiometric exogeneous reductants, thus offering a complementary technique for activating σ sp3 C–C(heteroatom) bonds. Preliminary mechanistic studies suggest that the presence of 2,2′-bipyridines improves the lifetime of ketyl radical intermediates.
Light-Promoted Transfer of an Iridium Hydride in Alkyl Ether Cleavage
Fast, Caleb D.,Schley, Nathan D.
supporting information, p. 3291 - 3297 (2021/10/12)
A catalytic, light-promoted hydrosilylative cleavage reaction of alkyl ethers is reported. Initial studies are consistent with a mechanism involving heterolytic silane activation followed by delivery of a photohydride equivalent to a silyloxonium ion generated in situ. The catalyst resting state is a mixture of Cp*Ir(ppy)H (ppy = 2-phenylpyridine-κC,N) and a related hydride-bridged dimer. Trends in selectivity in substrate reduction are consistent with nonradical mechanisms for C-O bond scission. Irradiation of Cp*Ir(ppy)H with blue light is found to increase the rate of hydride delivery to an oxonium ion in a stoichiometric test. A comparable rate enhancement is found in carbonyl hydrosilylation catalysis, which operates through a related mechanism also involving Cp*Ir(ppy)H as the resting state.
Method for hydrogenolysis of halides
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, (2021/01/11)
The invention discloses a method for hydrogenolysis of halides. The invention discloses a preparation method of a compound represented by a formula I. The preparation method comprises the following step: in a polar aprotic solvent, zinc, H2O and a compound represented by a formula II are subjected to a reaction as shown in the specification, wherein X is halogen; Y is -CHRR or R; hydrogenin H2O exists in the form of natural abundance or non-natural abundance. According to the preparation method, halide hydrogenolysis can be simply, conveniently and efficiently achieved through a simple and mild reaction system, and good functional group compatibility and substrate universality are achieved.
Selectivity and Mechanism of Iridium-Catalyzed Cyclohexyl Methyl Ether Cleavage
Fast, Caleb D.,Jones, Caleb A. H.,Schley, Nathan D.
, p. 6450 - 6456 (2020/07/13)
Cationic bis(phosphine)iridium complexes are found to catalyze the cleavage of cyclohexyl methyl ethers by triethylsilane. Selectivity for C-O cleavage is determined by the relative rates of SN2 demethylation versus SN1 demethoxylation, with the axial or equatorial disposition of the silyloxonium ion intermediate acting as an important contributing factor. Modulation of the electron-donor power of the supporting phosphine ligands enables a switch in selectivity from demethylation of equatorial methyl ethers to 2° demethoxylation. Applications of these accessible catalysts to the selective demethoxylation of the 3α-methoxy group of cholic acid derivatives is demonstrated, including a switch in observed selectivity controlled by 7α-substitution. The resting state of the catalyst has been characterized for two phosphine derivatives, demonstrating that the observed switch in C-O cleavage selectivity likely results from electronic factors rather than from a major perturbation of the catalyst structure.
Dehalogenative Deuteration of Unactivated Alkyl Halides Using D2O as the Deuterium Source
Xia, Aiyou,Xie, Xin,Hu, Xiaoping,Xu, Wei,Liu, Yuanhong
, p. 13841 - 13857 (2019/10/17)
The general dehalogenation of alkyl halides with zinc using D2O or H2O as a deuterium or hydrogen donor has been developed. The method provides an efficient and economic protocol for deuterium-labeled derivatives with a wide substrate scope under mild reaction conditions. Mechanistic studies indicated that a radical process is involved for the formation of organozinc intermediates. The facile hydrolysis of the organozinc intermediates provides the driving force for this transformation.
Novel electrochemical deoxygenation reaction using diphenylphosphinates
Lam, Kevin,Marko, Istvan E.
, p. 406 - 409 (2011/04/18)
The electrochemical reduction of diphenylphosphinate esters leads smoothly and in high yields to the corresponding deoxygenated products. In comparison with the previously developed methodologies, the electrolysis could be performed at lower temperature and with a higher current density, resulting in a shorter reaction time.
Hydropyrolysis over a platinum catalyst as a preparative technique for the compound-specific carbon isotope ratio measurement of C27 steroids
Meredith, Will,Gomes, Rachel L.,Cooper, Mick,Snape, Colin E.,Sephton, Mark A.
experimental part, p. 501 - 505 (2011/10/13)
Compound-specific stable carbon isotope analysis by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) is an important method for the determination of the 13C/12C ratios of biomolecules such as steroids, for a wide range of applications. However, steroids in their natural form exhibit poor chromatographic resolution, while derivatisation adds carbon thereby corrupting the stable isotopic composition. Hydropyrolysis with a sulphided molybdenum catalyst has been shown to defunctionalise the steroids, while leaving their carbon skeleton intact, allowing for the accurate measurement of carbon isotope ratios. The presence of double bonds in unsaturated steroids such as cholesterol resulted in significant rearrangement of the products, but replacing the original catalyst system with one of platinum results in higher conversions and far greater selectivity. The improved chromatographic performance of the products should allow GC/C/IRMS to be applied to more structurally complex steroid hormones and their metabolites.
One-pot reductive cleavage of exo-olefin to methylene with a mild ozonolysis-Clemmensen reduction sequence
Xu, Shu,Toyama, Takayuki,Nakamura, Jun,Arimoto, Hirokazu
scheme or table, p. 4534 - 4537 (2010/10/02)
A one-pot exo-olefin reductive cleavage was for the first time developed. The reaction could proceed under a mild condition avoiding the use of hazardous and expensive reagents. Meanwhile, a TMSCl-mediated Clemmensen reduction in alcoholic solvent was also examined.
Action of lithium ethylenediamine on 1,4-diketone
Ghosh, Pranab,Chakraborty, Prasanta
experimental part, p. 1125 - 1128 (2011/06/19)
Reactions of lithium ethylenediamine (Li/EDA) have been carried out on 1,4-diketones such as cholest-4(5)-en-3,6-dione (1) and hexane-2,5-dione (7). The resulting compounds have been characterized by optical rotation, IR, mass spectra and by comparison with authentic samples.
