1617-18-1Relevant articles and documents
Free-radical addition of 2-(perfluoroalkyl)ethanethiols to alkenes, alkadienes, cycloalkenes, alkynes and vinyl monomers
Brace, Neal O.
, p. 217 - 241 (1993)
The free-radical addition of 2-(perfluoroalkyl)ethanethiols (RFCH2CH2SH) to alkenes, cycloalkenes, alkadienes and alkynes has been studied to determine: (1) the mode of reaction, i.e. the stereochemistry, regiochemistry and any skeletal changes: (2) the relative reactivity towards unsaturates of differing structures and classes as affected by the presence of the RF group; and (3) the influence of the reaction conditions on the rate of addition or selectivity for different products.Adducts from 2-(F-hexyl)ethanethiol (1) and alkenes have been obtained in high yield,but containing small amounts of regio isomers.For example compound 1 with 1-heptene gave 1-heptane (3, 96percent yield) as well as 2-heptane (4, O.61percent) and 3-heptane (5, 2.22percent). 1,6-Hexadiene and 1,7-octadiene gave chiefly linear adducts, i.e.RFCH2CH2S(CH2)nCH=CH2 (7, n=4; or 12, n=6, respectively) and RFCH2CH2S(CH2)nSCH2CH2RF (8, n=6; or 14, n=8, respectively).A small amount (2-3percent) of cis- and trans-1-methyl-cyclohexane (13) isomers were present in 12.Compound 1 with 1,6-heptadiene gave 7--1-heptene (9), the bis adduct, 1,7-bis-heptane (11) and the cyclic adducts, cis- and trans-1-methal-2-methylcyclopentane (10).The relative amounts of cyclic isomers depended on the reactant ratio.Compound 1 added readily with free-radical initiation to vinyl monomers such as styrene and vinyl acetate, and to phenyl acetylene, propargyl acetate and ethyl propynoate.These new addition products are useful as models for further study.
A Convenient Route to β,γ-Unsaturated Esters without Formation of the α,β-Isomers. Palladium-Catalyzed Alkoxycarbonylation of Allylic Halides under Alcohol-Potassium Carbonate Tow-Phase Conditions
Kiji, Jitsuo,Okano, Tamon,Higashimae, Yukiko,Fukui, Yasuyuki
, p. 1029 - 1031 (1996)
Palladium-catalyzed, atmospheric pressure carbonylation of allylic halides under alcohol-potassium carbonate (liquid-solid) two-phase conditions affords β,γ-unsaturated esters without formation of the α,β-isomers. Phosphine-free palladium compounds such a
Merging Halogen-Atom Transfer (XAT) and Cobalt Catalysis to Override E2-Selectivity in the Elimination of Alkyl Halides: A Mild Route towardcontra-Thermodynamic Olefins
Zhao, Huaibo,McMillan, Alastair J.,Constantin, Timothée,Mykura, Rory C.,Juliá, Fabio,Leonori, Daniele
supporting information, p. 14806 - 14813 (2021/09/18)
We report here a mechanistically distinct tactic to carry E2-type eliminations on alkyl halides. This strategy exploits the interplay of α-aminoalkyl radical-mediated halogen-atom transfer (XAT) with desaturative cobalt catalysis. The methodology is high-yielding, tolerates many functionalities, and was used to access industrially relevant materials. In contrast to thermal E2 eliminations where unsymmetrical substrates give regioisomeric mixtures, this approach enables, by fine-tuning of the electronic and steric properties of the cobalt catalyst, to obtain high olefin positional selectivity. This unprecedented mechanistic feature has allowed access tocontra-thermodynamic olefins, elusive by E2 eliminations.
Reduction of Activated Alkenes by PIII/PV Redox Cycling Catalysis
Longwitz, Lars,Werner, Thomas
supporting information, p. 2760 - 2763 (2020/02/05)
The carbon–carbon double bond of unsaturated carbonyl compounds was readily reduced by using a phosphetane oxide catalyst in the presence of a simple organosilane as the terminal reductant and water as the hydrogen source. Quantitative hydrogenation was observed when 1.0 mol % of a methyl-substituted phosphetane oxide was employed as the catalyst. The procedure is highly selective towards activated double bonds, tolerating a variety of functional groups that are usually prone to reduction. In total, 25 alkenes and two alkynes were hydrogenated to the corresponding alkanes in excellent yields of up to 99 %. Notably, less active poly(methylhydrosiloxane) could also be utilized as the terminal reductant. Mechanistic investigations revealed the phosphane as the catalyst resting state and a protonation/deprotonation sequence as the crucial step in the catalytic cycle.
Regio- and chemoselective rearrangement of terminal epoxides into methyl alkyl and aryl ketones
Tian, Yingying,Jürgens, Eva,Kunz, Doris
supporting information, p. 11340 - 11343 (2018/10/31)
The development of the highly active pincer-type rhodium catalyst 2 for the nucleophilic Meinwald rearrangement of functionalised terminal epoxides into methyl ketones under mild conditions is presented. An excellent regio- and chemoselectivity is obtained for the first time for aryl oxiranes.
Additive-modulated switchable reaction pathway in the addition of alkynes with organosilanes catalyzed by supported Pd nanoparticles: Hydrosilylation: versus semihydrogenation
Duan, Yanan,Ji, Guijie,Zhang, Shaochun,Chen, Xiufang,Yang, Yong
, p. 1039 - 1050 (2018/03/05)
We herein report supported Pd nanoparticles on N,O-doped hierarchical porous carbon as a single operation catalyst-enabled additive-modulated reaction pathway for alkynes addition with organosilanes between hydrosilyation and semihydrogenation. In the case of alkynes hydrosilylation, a simple iodide ion as an additive has a promotion effect on the activity and regio- and stereoselectivity, where iodide can coordinate with Pd NPs via strong δ donation to increase the electron density of the Pd atom, resulting in an increased ability for the oxidative addition of hydrosilane as the rate-determining step to make the reaction proceed efficiently to afford vinylsilanes in high yields with excellent regio- and stereoselectivity. For the catalytic transfer semihydrogenation of alkynes, water was introduced to mix with organosilane to form a silanol together with the generation of hydrogen atoms on the Pd NPs surface or the liberation of H2 gas as a reducing agent, whereby the quantitative reduction of alkynes was achieved with exclusive selectivity to alkenes. In both cases, the catalyst could be recycled several times without a significant loss in activity or selectivity. A broad range of alkyl and aryl alkynes with various functional groups are compatible with the reaction conditions. The role the additive exerted in each reaction was extensively investigated through control experiments as well as the kinetic isotopic effect along with spectroscopic characterization. In addition, the respective mechanism operating in both reactions was proposed.
Stereospecific Hydrogenolysis of Lactones: Application to the Total Syntheses of (R)-ar-Himachalene and (R)-Curcumene
Spielmann, Kim,De Figueiredo, Renata Marcia,Campagne, Jean-Marc
, p. 4737 - 4743 (2017/05/12)
A straightforward strategy for the syntheses of curcumene and ar-himachalene is reported. Synthetic highlights include a catalytic and asymmetric vinylogous Mukaiyama reaction and a stereospecific hydrogenolysis of a tertiary benzylic center using Pd/C or Ni/Raney catalysts. Notably, using Ni/Raney, the stereoselectivity outcome (inversion vs retention) of the hydrogenolysis depends on the tertiary benzylic alcohol substitution.
Method for synthesizing 3-crotonate
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Paragraph 0026, (2017/08/29)
The invention discloses a method for synthesizing 3-crotonate. The method comprises 1, adding 400-600 parts by weight of toluene, 120-150 parts by weight of triethylamine and 110-120 parts by weight of alcohol into a reactor at the room temperature, uniformly mixing the materials through electric stirring, heating the mixture to a temperature of 40-60 DEG C, slowly adding 100 parts by weight of crotonyl chloride into the mixture, carrying out a reaction process over night, and carrying out gas chromatographic detection, 2, after the reaction, cooling the reaction liquid, washing the reaction liquid twice through water, drying the reaction liquid through anhydrous magnesium sulfate, carrying out filtration, and carrying out rotary evaporateion to remove the methylbenzene solvent so that a 3-crotonate crude product is obtained, and 3, treating the 3-crotonate crude product to obtain a 3-crotonate product. The method has a high product yield, produces few side products, has short reaction time, is environmentally friendly and has a high catalyst utilization rate.
A Common Synthetic Protocol for the Cyclic and Acyclic Core of Migrastatin, Isomigrastatin, and Dorrigocin via a Chiral β-Hydroxy-γ-butyrolactone Intermediate
Gade, Narendar Reddy,Iqbal, Javed
, p. 6558 - 6564 (2016/02/18)
A facile synthetic route has been developed for the synthesis of the cyclic and acyclic cores of migrastatin, isomigrastatin, and dorrigocin. The common synthetic route goes via a β-hydroxy-γ-butyrolactone intermediate that is obtained by a PdII-catalysed asymmetric allylic intramolecular cyclization of 3-hydroxy-2-methylhex-5-enoic acid following a protocol developed by White and coworkers. The synthesis of a key intermediate chiral β-hydroxy-γ-butyrolactone (A) by PdII-catalysed stereoselective allylic C-H oxidation is reported. A common synthetic route to transform this intermediate into key building blocks for the synthesis of migrastatin family members has been developed.
Total regio- and diastereocontrol in the aldol reactions of dienolborinates
Ramachandran, P. Veeraraghavan,Nicponski, Daniel,Kim, Bomi
supporting information, p. 1398 - 1401 (2013/05/09)
It is reported that appropriate dienolborinates can provide access to both diastereomers of 2-(hydroxymethyl)but-3-enoates through exclusive α-regiocontrol in a non-vinylogous pathway. Contrary to previous reports in which dialkylchloroboranes failed to enolize propanoates, acidity-enhanced but-3-enoates readily undergo enolization, offering unprecedented control over the formation of these valuable synthons. The first example of an aldol reaction in the presence of a phosphine-borane adduct is also reported.
