cas 481-21-0, 5α-Cholestane | Articles data

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Windaus
p. 133,136
(1917)
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Striebel,Tamm
p. 1094,1097
(1954)
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ASTEROSAPONIN P1 FROM THE STARFISH PATIRIA PECTINIFERA
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.
Kicha, A. A.,Kalinovsky, A. I.,Levina, E. V.,Stonik, V. A.,Elyakov, G. B.
p. 3893 - 3896
(1983)
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Defunctionalization of sp3 C–Heteroatom and sp3 C–C Bonds Enabled by Photoexcited Triplet Ketone Catalysts
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.
An, Juzeng,Gu, Yiting,Martin, Ruben,Wakeling, Matthew,Yin, Hongfei
p. 1031 - 1036
(2022/01/19)

Light-Promoted Transfer of an Iridium Hydride in Alkyl Ether Cleavage
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.
Fast, Caleb D.,Schley, Nathan D.
supporting information
p. 3291 - 3297
(2021/10/12)

Selectivity and Mechanism of Iridium-Catalyzed Cyclohexyl Methyl Ether Cleavage
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.
Fast, Caleb D.,Jones, Caleb A. H.,Schley, Nathan D.
p. 6450 - 6456
(2020/07/13)

Method for hydrogenolysis of halides
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.
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Paragraph 0232; 0257-0259

(2021/01/11)

Dehalogenative Deuteration of Unactivated Alkyl Halides Using D2O as the Deuterium Source
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.
Xia, Aiyou,Xie, Xin,Hu, Xiaoping,Xu, Wei,Liu, Yuanhong
p. 13841 - 13857
(2019/10/17)

Novel electrochemical deoxygenation reaction using diphenylphosphinates
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.
Lam, Kevin,Marko, Istvan E.
p. 406 - 409
(2011/04/18)

Hydropyrolysis over a platinum catalyst as a preparative technique for the compound-specific carbon isotope ratio measurement of C27 steroids
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.
Meredith, Will,Gomes, Rachel L.,Cooper, Mick,Snape, Colin E.,Sephton, Mark A.
experimental part
p. 501 - 505
(2011/10/13)

One-pot reductive cleavage of exo-olefin to methylene with a mild ozonolysis-Clemmensen reduction sequence
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.
Xu, Shu,Toyama, Takayuki,Nakamura, Jun,Arimoto, Hirokazu
scheme or table
p. 4534 - 4537
(2010/10/02)

Action of lithium ethylenediamine on 1,4-diketone
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.
Ghosh, Pranab,Chakraborty, Prasanta
experimental part
p. 1125 - 1128
(2011/06/19)

Organic electrosynthesis using toluates as simple and versatile radical precursors
The electrolysis of toluate esters leads smoothly to the formation of the radical of the alkyl fragment. This property has been used to develop a new electrochemical deoxygenation reaction. The Royal Society of Chemistry.
Lam, Kevin,Marko, Istvan E.
experimental part
p. 95 - 97
(2009/03/11)

Toluates: unexpectedly versatile reagents
The mechanism of the monoelectronic reduction of aromatic esters has been investigated. The unexpected synthetic utility of the toluate moiety in the deoxygenation of alcohols and the allylation of ketones is also reported. Finally, the use of aromatic esters as robust, though easily removable, protecting groups is depicted.
Lam, Kevin,Markó, István E.
experimental part
p. 10930 - 10940
(2010/02/28)

Using toluates as simple and versatile radical precursors
(Chemical Equation Presented) The viability of the toluate moiety as a radical precursor has been examined by studying deoxygenation and cyclization reactions.
Lam, Kevin,Marko, Istvan E.
scheme or table
p. 2773 - 2776
(2009/05/30)

Safe, facile radical-based reduction and hydrosilylation reactions in a microreactor using tris(trimethylsilyl)silane
A highly efficient system for tris(trimethylsilyl)silane (TTMSS) mediated deoxygenation, dehalogenation and hydrosilylation reactions is described in a microstructured device; this convenient platform enables the scale up of radical-based processes. The Royal Society of Chemistry.
Odedra, Arjan,Geyer, Karolin,Gustafsson, Tomas,Gilmour, Ryan,Seeberger, Peter H.
scheme or table
p. 3025 - 3027
(2009/02/04)

Chemoselective reduction of 1,4,6-cholestatrien-3-one and 1,4,6-androstatriene-3,17-dione by various hydride reagents
The chemoselectivity of rigid cyclic α,β-unsaturated carbonyl group on the reducing agents was influenced by the ring size and steric factor. Cholesterol (cholest-5-en-3β-ol) and dehydroepiandrosterone (DHEA) were oxidized with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone to form 1,4,6-cholestatrien-3-one and 1,4,6-androstatriene-3,17-dione. They were reduced with NaBH4, lithium tri-sec-butylborohydride (l-Selectride), LiAlH4, 9-borabicyclo[3.3.1]nonane (9-BBN), lithium triethylborohydride (Super-hydride), and BH3·(CH3)2S in various conditions, respectively. Reduction of 1,4,6-cholestatrien-3-one and 1,4,6-androstatriene-3,17-dione by NaBH4 (4 equiv.) produced 4,6-cholestadien-3β-ol and 4,6-androstadiene-3β,17β-diol, respectively. Reduction by l-Selectride (12 equiv.) afforded 4,6-cholestadien-3α-ol and 4,6-androstadiene-3α,17β-diol, chemoselectively. Reaction with Super-hydride (12 equiv.) produced 4,6-cholestadien-3-one and 3-oxo-4,6-androstadien-17β-ol. Reduction of 1,4,6-cholestatrien-3-one by 9-BBN (14 equiv.) produced 1,4,6-cholestatrien-3α-ol, but 1,4,6-androstatriene-3,17-dione was not reacted with 9-BBN in the reaction conditions. Reaction of LiAlH4 (6 equiv.) formed 4,6-cholestadien-3β-ol and 3-oxo-1,4,6-androstatrien-17β-ol. Reduction of 1,4,6-cholestatrien-3-one by BH3·(CH3)2S (11 equiv.) gave cholestane as major compound and unlike reactivity of cholesterol, 1,4,6-androstatriene-3,17-dione by 8 equiv. of BH3·(CH3)2S formed 3-oxo-1,4,6-androstatrien-17β-ol. LiAlH4 and BH3·(CH3)2S showed relatively low chemoselectivity.
Kim, Eunjeong,Ma, Eunsook
p. 360 - 367
(2008/02/04)

On the use of (TMS)3CH as novel tin-free radical reducing agent
(TMS)3CH is an efficient free radical reducing agent. Debromination, deiodation, dechlorination as well as decarboxylation of Barton and Kim esters can proceed smoothly using this tin-free reducing agent. Rate constants for hydrogen atom abstraction from TMS3CH by primary radicals were also determined.
Perchyonok, V. Tamara
p. 5163 - 5165
(2007/10/03)

Radical deoxygenation of alcohols and intermolecular carbon-carbon bond formation with surfactant-type radical chain carriers in water
An efficient and mild method is developed for radical deoxygenation of alcohols and formation of carbon-carbon bonds in water without adding additives such as surfactants. The reaction was applied to synthesis of 2′,3′-didehydro-2′,3′-dideoxynucleosides that are potent anti-HIV agents. The reaction afforded environmentally benign reaction conditions.
Cho, Dae Hyan,Jang, Doo Ok
p. 1799 - 1802
(2007/10/03)

One-pot synthesis of recyclable palladium catalysts for hydrogenations and carbon-carbon coupling reactions
Palladium nanoparticles were generated from tetrakis(triphenylphophine) palladium in a mixture of tetra(ethylene glycol) and tetramethoxysilane (or titanium(IV) isopropoxide), then encapsulated in silica matrix (or titania matrix) by the treatment with water. The resulting heterogeneous material showed high catalytic activity in the hydrogenations of various alkene and alkynes and in the carbon-carbon cross-coupling reactions such as the Suzuki-Miyaura, the Sonogashira, the Heck-Mizoroki, and the Stille reactions.
Kim, Namdu,Kwon, Min Serk,Park, Cheon Min,Park, Jaiwook
p. 7057 - 7059
(2007/10/03)

Ammonium formate/palladium on carbon: A versatile system for catalytic hydrogen transfer reductions of carbon-carbon double bonds
Various carbon-carbon double bonds in olefins and α,β -unsaturated ketones were effectively reduced to the corresponding alkanes and saturated ketones, using ammonium formate as a hydrogen transfer agent in the presence of Pd/C as catalyst in refluxing methanol.
Paryzek, Zdzislaw,Koenig, Hanna,Tabaczka, Bartlomiej
p. 2023 - 2026
(2007/10/03)

Deoxygenation of tertiary and secondary alcohols ROH by thiol-catalysed radical-chain redox decomposition of derivatives ROCH2X to give RH and XCHO
Compounds of the type ROCH2X, in which the substituent X is an electron-donating alkoxy, aryl or amido group, undergo thiol-catalysed radical-chain decomposition to give RH and XCHO. This reaction has been applied for the deoxygenation of representative tertiary and secondary alcohols ROH under metal-free conditions that require no stoichiometric co-reactant. Of the derivatives investigated, methoxymethyl (MOM) ethers and 1-alkoxymethyl-pyrrolidin-2-ones (PYRM ethers) proved to be the most generally successful and typical conditions for the redox decomposition to give RH involve heating under reflux in octane solvent in the presence of a peroxide initiator and tri-tert-butoxysilanethiol [(ButO)3SiSH] as a protic polarity-reversal catalyst. Conversions to RH were negligible in the absence of thiol. Several different types of tertiary alcohol, including steroidal and carbohydrate examples, were deoxygenated as their MOM and PYRM ethers to give very good isolated yields of RH. Although the MOM and PYRM ethers derived from many types of secondary alcohol also afforded good yields of RH, the MOM ether of diacetone D-glucose gave the 3-deoxy sugar in poor yield and the yield from the corresponding PYRM ether was still only moderate.
Dang, Hai-Shan,Roberts, Brian P.
p. 1161 - 1170
(2007/10/03)

A tin hydride designed to facilitate removal of tin species from products of stannane-mediated radical reactions
The stannane 1, which is simple to prepare, behaves like the conventional reagents Bu3SnH and Ph3SnH in standard free radical reactions, but with the special characteristic that the tin-containing byproducts are easily and very largely removed by mild hydrolysis (LiOH-water-THF or TsOH-water-THF), which converts them into base-soluble (aqueous NaHCO3) materials. The performance of stannane 1 was evaluated for a range of radical reactions involving halides, selenides, Barton-McCombie deoxygenation, and enyne cyclization. In several cases the effectiveness of the workup procedure in removing tin species was monitored by 1H NMR.
Clive, Derrick L. J.,Wang, Jian
p. 1192 - 1198
(2007/10/03)

Formation of silanethiols by reaction of silanes with carbonyl sulfide: Implications for radical-chain reduction of thiocarbonyl compounds by silanes
Carbonyl sulfide reacts with organosilanes at 60-85°C, in the presence of a radical initiator, to give the corresponding silanethiols. Triphenylsilane is confirmed as an excellent replacement for tributyltin hydride in the Barton-McCombie deoxygenation of alcohols via thier xanthates under mild conditions. Reduction of xanthates by silanes can produce COS as a by-product, leading to the in situ formation of silanethiol that will then act as a protic polarity-reversal catalyst for the reduction.
Cai, Yudong,Roberts, Brian P.
p. 763 - 766
(2007/10/03)

Radical deoxygenation of alcohols via their trifluoroacetate derivatives with diphenylsilane
Trifluoroacetate derivatives of alcohols can be used as precursors for the radical deoxygenation of alcohols with diphenylsilane. The reaction afforded high isolated yields of the deoxygenated products and neutral reaction conditions.
Jang, Doo Ok,Kim, Joonggon,Cho, Dae Hyan,Chung, Chan-Moon
p. 1073 - 1075
(2007/10/03)

Deoxygenative Functionalization of Hydroxy Groups via Xanthates with Tetraphenyldisilane
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Togo, Hideo,Matsubayashi, Sou,Yamazaki, Osamu,Yokoyama, Masataka
p. 2816 - 2819
(2007/10/03)

Seco-cholestane derivatives and methods of making the same
The present invention is directed to novel seco-cholestane derivatives, as well as to pharmaceutical compositions thereof, and methods of making the same. More particularly, the invention relates to C5- and C8-substituted seco-cholestane derivatives. The compounds of the invention can exhibit CDC25 phosphatase inhibition properties and anti-cancer activity.
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(2008/06/13)

Synthetic utility of 1,1,2,2-tetraaryIdisilanes: Radical reduction of alkyl phenyl chalcogenides
Reactivity of tetraaryldisilanes as radical reducing agents of alkyl phenyl chalcogenides initiated by Et3B or AIBN was studied. Here, the reactivity of alkyl sulfide was poor; however, various alkyl phenyl selenides and tellurides were reduced to the corresponding hydrocarbons in good yields with 1,1,2,2-tetraphenyldisilane. The Royal Society of Chemistry 1999.
Yamazaki, Osamu,Togo, Hidco,Yokoyama, Masataka
p. 2891 - 2896
(2007/10/03)

Tetraaryldisilanes as a novel strategic radical reagent
Reactivity of 1,1,2,2-tetraaryldisilanes as a radical reagent in ethanol was studied in reduction of alkyl bromides, addition to olefins and alkylation onto heteroaromatic bases with alkyl bromides. The present organodisilanes showed moderate to good reactivities for these three types of radical reactions. Among some disilanes prepared, 1,1,2,2-tetraphenyldisilane is the most useful in view of its reactivity and ease of preparation.
Yamazaki, Osamu,Togo, Hideo,Malsubayashi, Sou,Yokoyama, Masataka
p. 3735 - 3747
(2007/10/03)

Diphenylphosphine oxide: An alternative to organotin hydrides in the radical deoxygenation of alcohols
Various S-methyl dithiocarbonates of tertiary and secondary alcohols are effectively deoxygenated in high isolated yields by treatment with diphenylphosphine oxide and various radical initiators in boiling dioxane. Deoxygenation of S-methyl dithiocarbonate of primary alcohols can be accomplished similarly in boiling xylenes.
Jang, Doo Ok,Cho, Dae Hyan,Kim, Joonggon
p. 3559 - 3565
(2007/10/03)

1,1,2,2-tetraphenyldisilane as a diversified radical reagent
Reactivity of 1,1,2,2-tetraphenyldisilane as a radical reagent in ethanol was studied in reduction of alkyl bromides, addition to olefin and alkylation onto heteroaromatic bases with alkyl bromides. The present organodisilane showed moderate to good reactivities for these three types of radical reactions.
Yamazaki, Osamu,Togo, Hideo,Matsubayashi, Sou,Yokoyama, Masataka
p. 1921 - 1924
(2007/10/03)

Radical deoxygenation of alcohols via their S-methyl dithiocarbonate derivatives with di-n-butylphosphine oxide as hydrogen atom donor
Various S-methyl dithiocarbonates of tertiary and secondary alcohols are readily deoxygenated in high isolated yields by radical deoxygenation with di-n-butylphosphine oxide and various radical initiators in boiling dioxane. Primary alcohols react similarly in boiling xylenes.
Jang, Doo Ok,Cho, Dae Hyan,Barton, Derek H. R.
p. 39 - 40
(2007/10/03)

Sialic acid derivatives
Sialic acid derivatives represented by the general formula (I): STR1 wherein R1 is a steroidal compound residue; R2 is H or alkyl; R3 is alkyl; STR2 wherein each of R6 and R7 is H, alkyl or the like and I is an integer of 0 to 6; or the like; X is O or S; R4 is H or acyl; and R5 is R14 O-- (R14 is H or acyl) or R15 NH--(R15 is acyl or the like); their salts, hydrates or solvates are provided. Sialic acid derivatives of the present invention are expected to be effective medicines for the prevention and therapy of senile dementia including Alzheimer's disease and the like, because they increase ChAT activity in cholinergic neurons.
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(2008/06/13)

Sialic acid derivatives
Sialic acid derivatives represented by the general formula (I): wherein R1 is a steroidal compound residue; R2 is H or alkyl; R3 is alkyl; STR1 wherein each of R6 and R7 is H, alkyl or the like and I is an integer of 0 to 6; or the like; X is O or S; R4 is H or acyl; and R5 is R14 O--(R14 is H or acyl) or R15 NH--(R15 is acyl or the like); their salts, hydrates or solvates are provided. Sialic acid derivatives of the present invention are expected to be effective medicines for the prevention and therapy of senile dementia including Alzheimer's disease and the like, because they increase ChAT activity in cholinergic neurons.
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(2008/06/13)

Radical reactions with alkyl and fluoroalkyl ((fluorous) tin hydride reagents in supercritical CO2
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Hadida, Sabine,Super, Michael S.,Beckman, Eric J.,Curran, Dennis P.
p. 7406 - 7407
(2007/10/03)

Antihypercholesterolemic compounds and related pharmaceutical compositions and methods of use
Novel antihypercholesterolemic agents are provided. An exemplary group of compounds has the structural formula (I) STR1 wherein R is a C-17 side chain, R1 is --OH, =O, or the like, and X and Y are N, N→O, CH, C--OH, C--OCH3 or C--Z. Methods of using the compound of formula (I) or other novel oxysterol analogs to treat hypercholesterolemia are provided, as are pharmaceutical compositions containing the compounds.
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(2008/06/13)

5,10-Dihydro-Silanthrene as a Reagent for the Barton-McCombie Reaction
The deoxygenation of secondary alcohols via thionoesters with the use of 5,10-dihydrosilanthrene as the radical reducing agent has been studied in detail.The ability of hydrogen donation of this silane has been measured using the one-carbon ring expansion of 1-(2-oxocyclopentyl)ethyl radical as a timing device.
Gimisis, T.,Ballestri, M.,Ferreri, C.,Chatgilialoglu, C.,Boukherroub, R.,Manuel, G.
p. 3897 - 3900
(2007/10/02)

A Comment on the Use of Triethylsilane as a Radical-Based Reducing Agent
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Chatgilialoglu, Chryssostomos,Ferreri, Carla,Lucarini, Marco
p. 249 - 251
(2007/10/02)

Xanthic anhydrides: A novel and convenient source of alkoxythiocarbonyl and alkyl radicals
Upon irradiation with visible light, xanthic anhydrides 14 undergo a chain reaction leading to xanthates 17 and involving β-scission of the intermediate alkoxythiocarbonyl radical.
Forbes, Judith,Zard, Samir Z.
p. 8257 - 8266
(2007/10/02)

The invention of radical reactions. Part XXXI. Diphenylsilane: A reagent for deoxygenation of alcohols via their thiocarbonyl derivatives, deamination via isonitriles, and dehalogenation of bromo- and iodo- compounds by radical chain chemistry
Various thionocarbonates and xanthates of alcohols and bis-xanthates of vic-diols are readily deoxygenated to the corresponding hydrocarbons or olefins, while bromides and iodides are dehalogenated with diphenylphenylsilane in good yield.
Barton, Derek H. R.,Jang, Doo Ok,Jaszberenyi, Joseph Cs.
p. 7193 - 7214
(2007/10/02)

The invention of radical reactions. Part XXIX. Radical mono- and dideoxygenations with silanes
Thionocarbonates and xanthates of primary and secondary alcohols, as well as bis-xanthates of vic-diols are readily deoxygenated to the corresponding hydrocarbons or olefins with phenylsilane, triphenylsilane, and triethylsilane in good yield.
Barton,Jang,Jaszberenyi Cs.
p. 2793 - 2804
(2007/10/02)

The Invention of Radical Reactions. 32. Radical Deoxygenations, Dehalogenations, and Deaminations with Dialkyl Phosphites and Hypophosphorous Acid as Hydrogen Sources
Reagents, containing a P-H bond, such as dimethyl phosphite, diethyl phosphite, hypophosphorous acid and various salts of hypophosphorous acid are effective radical reducing agents for organic halides, thionoesters, and isocyanides affording high yields of the corresponding hydrocarbons.Reduction of tertiary phenyl selenides and tertiary nitro compounds are not efficient under these conditions.Olefination of 1,2-diols is also accomplished via the corresponding thiocarbonyl derivatives using hypophosphorous acid and triethylamine in the presence of a suitable "sacrifical olefin" im moderate to good yields.
Barton, Derek H. R.,Jang, Doo Ok,Jaszberenyi, Joseph Cs.
p. 6838 - 6842
(2007/10/02)

Stereocontrolled formation of cis and trans ring junctions in hydrindane, decalin, and steroid systems by palladium-catalyzed regioselective and stereospecific hydrogenolysis of allylic formates
Both the cis and trans ring junctions can be generated selectively in hydrindane, decalin and steroid systems by the palladium-catalyzed regioselective and stereospecific decarboxylation-hydrogenolysis of allylic formates. The trans junctions were formed from 3β allylic formates of decalin and steroid and 5β allylic formates of hydrindane. The corresponding 3α and 5α formates generate the cis ring junction.
Mandai, Tadakatsu,Matsumoto, Takaji,Kawada, Mikio,Tsuji, Jiro
p. 5483 - 5493
(2007/10/02)

Ultrasound assisted zinc reactions in synthesis 2. A new Clemmensen-type reduction
A mild and efficient method is described for the reduction of carbonyls to methylene groups. Under ultrasonic irradiation, deoxygenation of 3-oxosteroids with zinc dust in acetic acid or acetic acid/water was achieved in 15 minutes. The observed selectivity at C-3 in the presence of 17- and 20-oxo groups is discussed.
Salvador,Sa E Melo,Campos Neves
p. 361 - 362
(2007/10/02)

Hypophosphorous acid and its salts: New reagents for radical chain deoxygenation, dehalogenation and deamination
Thionocarbonates and xanthates of alcohols, bromides, iodides and isonitriles can be transformed to the corresponding hydrocarbons with hypophosphorous acid or its salts in radical chain reactions.
Barton,Jang,Jaszberenyi
p. 5709 - 5712
(2007/10/02)

Radical deoxygenations and dehalogenations with dialkyl phosphites as hydrogen atom source
Thionocarbonates and xanthates of alcohols, and various halides and phenylselenides can be transformed to the corresponding hydrocarbons with alkyl phosphites and benzoyl peroxide in most cases in high-yielding radical reactions.
Barton,Jang,Jaszberenyi
p. 2311 - 2314
(2007/10/02)

Radical Chain Reduction of Alkyl Halides, Dialkyl Sulphides and O-Alkyl S-Methyl Dithiocarbonates to Alkanes by Trialkylsilanes
Saturated primary, secondary and tertiary alkyl halides RX (X = Cl, Br or I) are reduced to the corresponding alkanes RH in essentially quantitative yield by triethylsilane in refluxing hexane or cyclohexane in the presence of a suitable initiator and an alkanethiol catalyst.Reduction proceeds by a radical chain mechanism and the thiol acts as a polarity reversal catalyst which mediates hydrogen-atom transfer from the Si-H group of the silane to the alkyl radical R..Triphenylsilanethiol and perfluorohexanesulphenyl chloride are also effective catalysts; the latter is probably reduced in situ to the corresponding fluorinated thiol.Other silanes R3SiH (R = Prn, Pri or Ph) also bring about reduction.The silane-thiol couple therefore serves as a useful replacement for tributylstannane as a homolytic reducing agent for alkyl halides.Reduction of 6-bromohex-1-ene, to give a mixture of hex-1-ene and methylcyclopentane, is more sluggush than reduction of saturated halides and this is attributed to removal of the thiol catalyst by addition across the C=C bond.Ethyl 4-bromobutanoate is smoothly reduced to ethyl butanoate without interference from the ester function.Dialkyl sulphides are reduced to alkanes by triethylsilane in a radical chain reaction, but the effect of added thiol depends on the nature of the S-alkyl groups in the sulphide.The trialkylsilane-thiol couple can also successfully replace trialkylstannane as the reducing agent in the Barton-McCombie deoxygenation of primary and secondary alcohols via their S-methyl dithiocarbonate (xanthate) esters.Good yields of deoxy compounds are obtained from octan-1-ol, octan-2-ol, octadecan-1-ol, 5α-cholestan-3β-ol, cholesterol and 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose.
Cole, Stephen J.,Kirwan, J. Nicholas,Roberts, Brian P.,Willis, Colin R.
p. 103 - 112
(2007/10/02)

Radical mono- And dideoxygenations with the triethylsilane + benzoyl peroxide system
Thionocarbonates and xanthates of primary and secondary alcohols, as well as dixanthates of vicdiols can easily be deoxygenated to the corresponding hydrocarbons or olefins with triethylsilane and benzoyl peroxide in high-yielding radical reactions.
Barton, Derek H. R.,Jang, Doo Ok,Jaszberenyi, Joseph Cs
p. 7187 - 7190
(2007/10/02)

On the mechanism of deoxygenation of secondary alcohols by tin hydride reduction of methyl xanthates and other thiocarbonyl derivatives
The room temperature deoxygenation of xanthates and thionocarbonates using (n - Bu) 3Sn-H - Et3B - air has been studied, especially with 119Sn N.M.R. spectroscopy. The orignal conception of tin radical attack on thiocarbonyl is confirmed.
Barton,Jang,Jaszberenyi Cs.
p. 3991 - 3994
(2007/10/02)

Deoxygenation of alcohols by the reactions of their xanthate esters with triethylsilane: An alternative to tributyltin hydride in the Barton-McCombie reaction
O-Alkyl S-methyl dithiocarbonates derived from primary or secondary alcohols (ROH) react with trialkylsilanes in non-aromatic solvents to give the corresponding hydrocarbons RH in good yields; the reductions are promoted by thiols which act as polarity reversal catalysts.
Nicholas Kirwan,Roberts, Brian P.,Willis, Colin R.
p. 5093 - 5096
(2007/10/02)

An improved radical chain procedure for the deoxygenation of secondary and primary alcohols using diphenylsilane as hydrogen atom donor and triethylborane-air as initiator
Thiocarbonyl derivatives of secondary alcohols are readily reduced by diphenylsilane in a radical chain process at room temperature using triethylborane-air as an initiator. Primary alcohols react similarly at 80°. Comparison is made with the similar reactivity of tris(trimethylsilyl)silane.
Barton, Derek H. R.,Jang, Doo Ok,Jaszberenyi, Joseph Cs.
p. 4681 - 4684
(2007/10/02)

A NOVEL RADICAL CHAIN REACTION OF XANTHIC ANHYDRIDES. FURTHER OBSERVATIONS ON THE INTERMEDIACY OF ALKOXYTHIOCARBONYL RADICALS IN THE BARTON-McCOMBIE REACTION.
On irradiation with visible light, primary and secondary xanthic anhydrides undergo a radical chain reaction to give the corresponding xanthates with loss of carbon oxysulphide.
Forbes, J. E.,Zard, S. Z.
p. 4367 - 4370
(2007/10/02)

Synthesis of 15β-Hydroxy-24-oxocholesterol and 15β,29-Dihydroxy-7-oxofucosterol
3β-Acetoxyandrost-5-en-17-one has been converted into 15β-hydroxy-24-oxocholesterol.Reaction of (17E)-3-β-(dimethyl-t-butylsilyloxy)-15β,16β-epoxypregna-5,17(20)-diene with the magnesium cyanocuprate derivative of 3-(1,3-dioxolan-2-yl)-4-methylpentyl bromide gave (20R)-3β-(dimethyl-t-butylsilyloxy)-15β-hydroxy-24-oxocholesta-5,16-diene 24-ethylene acetal in 80percent yield, and this was converted into the target compound in high yield by catalytic hydrogenation followed by removal of the protecting groups.Reaction of 3β,15β-diacetoxycholest-5-en-24-one with the anion of diethyl cyanomethylphosphonate and reduction of the resulting nitrile with DIBAL-H, gave 15β,29-dihydroxyfucosterol.This was converted into the 3,29-diacetate 15-formate and oxidized with chromium trioxide-3,5-dimethylpyrazole.Removal of the acetate and formate groups with aqueous potassium carbonate afforded 15β,29-dihydroxy-7-oxofucosterol.
Liu, Dashan,Stuhmiller, Louise M.,McMorris, Trevor C.
p. 2161 - 2168
(2007/10/02)