36634-72-7Relevant academic research and scientific papers
cis-Selective Transfer Semihydrogenation of Alkynes by Merging Visible-Light Catalysis with Cobalt Catalysis
Ding, Hai-Xin,Guo, Wen-Jie,He, Yong-Qin,Song, Xian-Rong,Tian, Wan-Fa,Xiao, Qiang,Ye, Jing
supporting information, (2020/02/05)
Herein, the first example of visible-light-driven, cobalt-catalyzed transfer semihydrogenation of alkynes to alkenes is reported. It is carried out by using Ir[dF(CF3)ppy]2(dtbbpy)]PF6 as photosensitizer, CoBr2/n-Bu3P as proton-reducing catalyst, and i-Pr2NEt/AcOH as the hydrogen source. Under the established catalytic system, the semihydrogenation proceeds with Z as the major selectivity and with inhibition of over-reduction. Under mild reaction conditions, both internal and terminal alkynes, as well as reducible functional groups such as halogen, cyano, and ester, are tolerated. Preliminary mechanistic studies revealed the dual role of the photosensitizer in initiating the reaction via a single-electron transfer process and controlling the stereoselectivity via an energy transfer process. (Figure presented.).
Method for catalytically reducing alkynes into olefins through visible light induction
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Paragraph 0043-0046, (2020/03/09)
The invention discloses a method for catalytically reducing alkynes into olefins through visible light induction. The method can avoid generation of over-reduced alkane products and the highest yieldis 99%. The method comprises the following steps: by taking an alkyne as a raw material, adding a photosensitizer and a cobalt catalyst, then adding a phosphine ligand or bipyridine ligand, an electronic sacrificial reagent, acetic acid and an organic solvent under inert gas protection, and irradiating with blue light at room temperature for 7-14 hours; and after the reaction is finished, spin-drying an obtained reaction solution, and carrying out silica gel column chromatography separation to obtain an olefin product; wherein the organic solvent is 1, 4-dioxane or tetrahydrofuran, and the alkyne is an aliphatic alkyne or an aromatic alkyne. Reduction of alkyne is realized through a hydrogen transfer strategy, use of dangerous hydrogen is avoided, generation of overreduction products is avoided, reaction conditions are mild, the reaction yield is high, and the method has a good application prospect.
Determining the excited-state substituent constants of furyl and thienyl groups
Qu, Junyan,Cao, Chao-Tun,Cao, Chenzhong
supporting information, (2018/04/24)
Six series of styrene derivatives XCH═CHArY (total of 65) containing the styrene parent molecular skeleton were synthesized (here, Y is OMe, Me, H, F, Cl, CF3, CN, and NO2, and X is 2-furyl, 3-furyl, 2′-methyl-2-furyl, 2-thienyl, 3-thienyl, and 2′-methyl-2-theniyl). Their ultraviolet absorption spectra were measured in anhydrous ethanol, and their wavelength of absorption maximum λmax was recorded. For the wavenumber νmax (cm?1, νmax?=?1/λmax) of the obtained λmax, a quantitative correlation analysis was performed, and 6 excited-state substituent constants σexcc(p) of groups X were obtained by means of curve-fitting method. Taking the νmax values of total 90 compounds of styrene derivatives as a data set (including 25 compounds from reference and 65 compounds of this work), a quantitative correlation analysis was performed, and the reliability of the obtained σexcc(p) was verified. In addition, 12 samples of disubstituted Schiff bases (XCH═NArY) involving the above groups X were synthesized, and their νmax values were recorded. Using these 12 νmax together with the 14 νmax values of Schiff bases taken from reference (total of 26 compounds), it was further verified that the σexcc(p) values are reliable by means of quantitative correlation method.
C-H Alkenylation of Heteroarenes: Mechanism, Rate, and Selectivity Changes Enabled by Thioether Ligands
Gorsline, Bradley J.,Wang, Long,Ren, Peng,Carrow, Brad P.
supporting information, p. 9605 - 9614 (2017/07/24)
Thioether ancillary ligands have been identified that can greatly accelerate the C-H alkenylation of O-, S-, and N-heteroarenes. Kinetic data suggest thioether-Pd-catalyzed reactions can be as much as 800× faster than classic ligandless systems. Furthermore, mechanistic studies revealed C-H bond cleavage as the turnover-limiting step, and that rate acceleration upon thioether coordination is correlated to a change from a neutral to a cationic pathway for this key step. The formation of a cationic, low-coordinate catalytic intermediate in these reactions may also account for unusual catalyst-controlled site selectivity wherein C-H alkenylation of five-atom heteroarenes can occur under electronic control with thioether ligands even when this necessarily involves reaction at a more hindered C-H bond. The thioether effect also enables short reaction times under mild conditions for many O-, S-, and N-heteroarenes (55 examples), including examples of late-stage drug derivatization.
Zeolite y nanosheet assembled palladium catalysts with high catalytic activity and selectivity in the vinylation of thiophenes
Fu, Wenqian,Feng, Yu,Fang, Zhongxue,Chen, Qun,Tang, Ting,Yu, Quanyong,Tang, Tiandi
supporting information, p. 3115 - 3118 (2016/02/23)
Zeolite Y nanosheets with a micro-meso-macroporous structure were synthesized, and applied in the assembly of a Pd catalyst (Pd/NS-Y) for direct vinylation of thiophenes with high activity and selectivity, as compared to Pd(OAc)2, Pd(NO3)2, and Pd(PPh3)4 catalysts. This feature should be assigned to the highly dispersed Pdδ+ (δ 2+.
Aerobic dehydrogenative Heck reactions of heterocycles with styrenes: A negative effect of metallic Co-oxidants
Vasseur, Alexandre,Harakat, Dominique,Muzart, Jacques,Le Bras, Jean
, p. 59 - 67 (2013/03/13)
The aerobic dehydrogenative Heck reaction (DHR) of heterocycles with styrenes was found to be more efficient in the absence of metallic cooxidants. According to a study of the isotope effect, the C-H cleavage was the rate-determining step of the catalytic
Dehydrogenative heck reaction of furans and thiophenes with styrenes under mild conditions and influence of the oxidizing agent on the reaction rate
Vasseur, Alexandre,Muzart, Jacques,Le Bras, Jean
, p. 12556 - 12560 (2011/12/04)
CiH vs. CiBr in Heck: The direct dehydrogenative coupling of furans and thiophenes with styrenes occurs under mild conditions (see scheme). This method allows the coupling of brominated substrates through CiH bond activation. In addition, DMSO and benzoquinone had a positive effect on the reaction rate.
Vinyl tris(trimethylsilyl)silanes: substrates for Hiyama coupling
Wang, Zhizhong,Pitteloud, Jean-Philippe,Montes, Lucresia,Rapp, Magdalena,Derane, Djenny,Wnuk, Stanislaw F.
, p. 5322 - 5327 (2008/09/21)
The oxidative treatment of vinyl tris(trimethylsilyl)silanes with hydrogen peroxide in aqueous sodium hydroxide in tetrahydrofuran generates reactive silanol or siloxane species that undergo Pd-catalyzed cross-couplings with aryl, heterocyclic, and alkenyl halides in the presence of Pd(PPh3)4 and tetrabutylammonium fluoride. Hydrogen peroxide and base are necessary for the coupling to occur while activation of the silanes with fluoride is not required. The conjugated and unconjugated tris(trimethylsilyl)silanes serve as good cross-coupling substrates. The (E)-silanes undergo coupling with retention of stereochemistry while coupling of (Z)-silanes occurred with lower stereoselectivity to produce an E/Z mixture of products.
Solvent-free Wittig olefination with stabilized phosphoranes - Scope and limitations
Thiemann, Thies,Watanabe, Masataka,Tanaka, Yasuko,Mataka, Shuntaro
, p. 578 - 584 (2007/10/03)
Neat mixtures of arene/hetarenecarbaldehydes, alkanals as well as alkenals with alkyl (triphenylphosphoranylidene)acetates react exothermally to furnish the corresponding alkenes. In certain cases, heating has to be provided externally. Reaction times are short and yields are generally very high. Neat mixtures of ketones and alkyl (triphenylphosphoranylidene)acetates react preferentially under microwave irradiation. The better stabilized phosphoranes do not react in the solid state with aldehydes or ketones under conventional heating, but necessitate microwave irradiation, although not all of the phosphoranes have been found to be stable under microwave irradiation at 500 W (2450 MHz).
Efficient Syntheses of 2-Functionalized Thiophenes, Cyclopent[b]thiophenes, and Polysubstituted Benzo[b]thiophenes from 2-(Benzotriazol-1-ylmethyl)thiophenes
Katritzky, Alan R.,Serdyuk, Larisa,Xie, Linghong,Ghiviriga, Ion
, p. 6215 - 6221 (2007/10/03)
Diverse 2-(functionalized-alkyl)- and 2-alkenylthiophenes 2a,b, 4a,b, and 6a-d are prepared via the side chain elaboration of 2-(benzotriazol-1-ylmethyl)thiophenes 3a,b, themselves readily available from the condensation of 1-(hydroxymethyl)benzotriazole with thiophenes 1a,b. Treatment of 2-(benzotriazol-1-ylmethyl)thiophenes 3b and 5g,j with styrenes in the presence of zinc bromide results in formal [3 + 2] cycloaddition to give in good yields substituted cyclopent[b]thiophenes 16a/17a, 16b/17b, and 18. Lithiation and 1,4-addition to a variety of α,β-unsaturated ketones and aldehydes, and subsequent acid-catalyzed intramolecular cyclization followed by debenzotri-azolylation-dehydration converts 3 and 5 to a range of polysubstituted benzo[b]thiophenes 19a-d and 25a-e in moderate to excellent yields. NOE difference spectroscopy and NMR 1H-13C long-range correlation support structures of types 19 and 25 and exclude those of type 26, thus confirming the cyclization pathway.
