- Rhodium-catalyzed C(sp2)-H addition of arylboronic acids to alkynes using a boron-based, convertible ortho-directing group
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Temporary modification of a boronyl group with pyrazoryl-aniline allowed insertion of arylpropiolates and diphenylacet-ylenes into the o-C-H bond of arylboronic acids in the presence of rhodium catalysts, giving 3,3-diarylacrylates and triarylethene conta
- Yamamoto, Takeshi,Ishibashi, Aoi,Suginome, Michinori
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- trans-Selective hydrocyanation of ynoates, ynones and ynoic acids catalyzed by nucleophilic phosphines
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trans-Selective hydrocyanation of ynoates and ynones in the presence of TMSCN and an alcohol additive are catalyzed by nucleophilic phosphines. The trisubstituted E-olefin products of anti-addition of hydrogen cyanide to the alkyne are produced with high regio- and stereoselectivity. The alcohol additive reacts with TMSCN to produce hydrogen cyanide in situ. Ynoic acids undergo the phosphine catalyzed hydrocyanation in the presence of TMSCN under aprotic conditions only. In these reactions, TMSCN reacts with the acid to generate hydrogen cyanide and the silyl ester which, unlike the acid, undergoes phosphine catalyzed hydrocyanation and gives the stereo-defined E-2-cyano-acrylic acids after work up.
- Meyer, Maximilian,Peri?, Milica,Sch?mberg, Fritz,Vilotijevi?, Ivan
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supporting information
(2021/10/04)
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- Organocatalytic trans Phosphinoboration of Internal Alkynes
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We report the first trans phosphinoboration of internal alkynes. With an organophosphine catalyst, alkynoate esters and the phosphinoboronate Ph2P-Bpin are efficiently converted into the corresponding trans-α-phosphino-β-boryl acrylate products in moderate to good yield with high regio- and Z-selectivity. This reaction operates under mild conditions and demonstrates good atom economy, requiring only a modest excess of the phosphinoboronate. X-ray crystallography experiments allowed structural assignment of the unprecedented and densely functionalized (Z)-α-phosphino-β-boryl acrylate products.
- Fritzemeier, Russell G.,Nekvinda, Jan,Rosenblum, Carol Ann,Santos, Webster L.,Slebodnick, Carla,Vogels, Christopher M.,Westcott, Stephen A.
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supporting information
p. 14358 - 14362
(2020/07/04)
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- Copper-catalyzed enantioselective conjugate reduction of α,β-unsaturated esters with chiral phenol–carbene ligands
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A chiral phenol–NHC ligand enabled the copper-catalyzed enantioselective conjugate reduction of α,β-unsaturated esters. The phenol moiety of the chiral NHC ligand played a critical role in producing the enantiomerically enriched products. The catalyst worked well for various (Z)-isomer substrates. Opposite enantiomers were obtained from (Z)- and (E)-isomers, with a higher enantiomeric excess from the (Z)-isomer.
- Mimura, Shohei,Mizushima, Sho,Sawamura, Masaya,Shimizu, Yohei
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supporting information
p. 537 - 543
(2020/05/14)
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- Efficient Access to Chiral β-Borylated Carboxylic Esters via Rh-Catalyzed Hydrogenation
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Rh/bisphosphine?thiourea ligand (ZhaoPhos)-catalyzed asymmetric hydrogenation of (Z)-β-substituted-β-boryl-α,β-unsaturated esters was successfully developed, furnishing a variety of chiral β-borylated carboxylic esters with high yields and excellent enantioselectivities (up to 99% yield and >99% ee). The gram-scale asymmetric hydrogenation was performed efficiently in the presence of only 0.05 mol% (S/C=2 000) catalyst loading with full conversion, 99% yield and 99% ee. Moreover, the hydrogenation product was easily converted to other versatile synthetic intermediates, such as methyl (S)-3-hydroxy-3-phenylpropanoate and methyl (S)-3-(furan-2-yl)-3-phenylpropanoate. (Figure presented.).
- Liu, Gang,Li, Anqi,Qin, Xueyuan,Han, Zhengyu,Dong, Xiu-Qin,Zhang, Xumu
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supporting information
p. 2844 - 2848
(2019/04/26)
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- Synthesis of Chiral β-Borylated Carboxylic Esters via Nickel-Catalyzed Asymmetric Hydrogenation
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The highly efficient Ni-catalyzed asymmetric hydrogenation of β-boronic ester substituted-α,β-unsaturated carboxylic esters was successfully developed using (S,S)-Ph-BPE as the ligand. A series of chiral β-borylated carboxylic esters were obtained with high yields (94%-99% yields) and excellent enantioselectivities (89%-99% ee). The gram-scale asymmetric hydrogenation with a low catalyst loading (0.25 mol %) and synthetic transformation of hydrogenation product demonstrated the great synthetic utility of this methodology.
- Han, Zhengyu,Liu, Gang,Zhang, Xianghe,Li, Anqi,Dong, Xiu-Qin,Zhang, Xumu
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supporting information
p. 3923 - 3926
(2019/06/14)
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- Oxidative Alkoxycarbonylation of Alkynes by Means of Aryl α-Diimine Palladium(II) Complexes as Catalysts
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The straightforward in situ synthesized bis(2,6-diisopropyl)acenaphthenequinonediimine palladium triflate catalyst was generally employed for both the mono-alkoxycarbonylation of terminal alkynes, and the bis-alkoxycarbonylation of 1,2-disubstituted alkynes by using mild reaction conditions [carbon monoxide pressure (PCO)=4 bar, temperature=20 °C]. Utilizing low catalyst loading (down to 0.5 mol%), a variety of propiolic esters were synthesized with good to excellent isolated yields. Most importantly the system was very efficient not only with methanol but also with a range of different alcohols, starting from the less hindered benzyl alcohol to the most hindered ones, such as isopropyl alcohol and tert-butyl alcohol. In addition, aromatic and aliphatic 1,2-disubstituted alkynes were converted into maleic acid derivatives, together with an acid-catalyzed isomerization reaction, showing modest to good selectivity and excellent combined yields. In particular 3-hexyne showed a satisfactory degree of selectivity for the maleic diesters of methanol and benzyl alcohol, obtaining the corresponding products with good isolated yields. (Figure presented.).
- Beltrani, Michela,Carfagna, Carla,Milani, Barbara,Mancuso, Raffaella,Gabriele, Bartolo,Fini, Francesco
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p. 3244 - 3253
(2016/10/21)
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- A Simple and Efficient Esterification Method
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A convenient and practical esterification was realized and this reaction proceeded without a dehydrating reagent or water removal equipment. The synthesis of esters by reaction of carboxylic acids with various alcohols such as methyl, ethyl, isopropyl, isobutyl, allyl, benzyl, propargyl and decanyl alcohols were achieved with a catalytic amount of CBr4 under refluxing reaction condition.
- Ming-Yi, Chen,Lee, Adam Shih-Yuan
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p. 103 - 108
(2007/10/03)
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- Palladium-catalyzed carbonylation of terminal acetylenes: A new method for synthesis of acetylenecarboxylates
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Acetylenecarboxylates were easily prepared via palladium bromide-catalyzed carbonylation of terminal acetylenes in fair to good yields.
- Li,Jiang,Chen
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p. 199 - 202
(2007/10/03)
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- Enantioselective Catalytic Epoxidation of Cinnamate Esters
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A broad study of the (salen)Mn(III)-catalyzed asymmetric epoxidation of cis-cinnamate esters reveals that the steric properties of the ester group have a profound influence on enantioselectivity in the epoxidation reaction, with bulkier esters affording highest ee's.The sensitivity of the reaction selectivity to the steric properties of the cis-alkene are consistent with a "skewed" side-on approach of olefin to the metal -oxo.The electronic properties of the substrate arene ring substituents do not correlate with epoxidation ee, but instead with the cis/trans partitioning of product formation.Evidence is provided for a non-polar inter mediate in a stepwise oxygen-atom-transfer mechanism.The presence of pyridine N-oxide derivatives has a significant effect on catalysts rates and total turnovers, but negligible influence on the stereoselectivity of epoxidation.A mechanistic basis for the role of these additives is proposed.The synthetic applicability of the cinnamate epoxidation methodology is illustrated in the highly enantioslective synthesis of diltiazem.
- Jacobsen, Eric N.,Deng, Li,Furukawa, Yoshiro,Martinez, Luis E.
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p. 4323 - 4334
(2007/10/02)
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- Preparation of Arylpropiolate Esters from Trichlorocyclopropenium Cation and Elaboration of the Esters to Unsymmetrical 1,4-Pentadiyn-3-ones and Unsymmetrical Tellurapyranones
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The addition of aromatic compounds including thiophene, naphthalene derivatives, and some benzene derivatives to trichlorocyclopropenium cation gave nearly quantitative yields of 1-aryl-2,3,3-trichlorocyclopropenes.Alcoholysis of the cyclopropene derivatives gave either arylpropiolate esters or arylpropiolate orthoesters (in the presence of added amine base).The arylpropiolates can be converted to unsymmetrical 1,4-pentadiyn-3-ones by two different approaches.The first approach involved reduction of the arylpropiolate esters with diisobutylaluminum hydride to give the corresponding propargyl alcohol.Pyridinium chlorochromate or manganese dioxide oxidation of the alcohol gave the propargyl aldehydes.Addition of a lithium acetylenide gave a 1,4-pentadiyn-3-ol, which could then be oxidized to the 1,4-pentadiyn-3-one with 10percent chromic acid or manganese dioxide.The second pathway used a Lewis acid mediated coupling of a propargylic acid chloride with a (trimethylsilyl)acetylene to give the 1,4-pentadiyn-3-ones directly.The coupling of 2-thiophenepropiolic acid chloride gave the product of HCl addition to the expected 1,4-diynone.The regiochemistry of addition was determined to be chloride addition to the thiophene-bearing triple bond on the basis of 1H NMR studies.The diynones were converted to unsymmetrical 2,6-disubstituted tellura-4H-pyran-4-ones with disodium telluride anion.
- Wadsworth, Donald H.,Geer, Susan M.,Detty, Michael R.
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p. 3662 - 3668
(2007/10/02)
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- FACILE SYNTHESIS OF ACETYLENECARBOXYLATES BY THE OXIDATIVE CARBONYLATION OF TERMINAL ACETYLENES CATALYSED BY PdCl2 UNDER MILD CONDITIONS
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Terminal acetylenes were converted to acetylenecarboxylates in high yields under athmospheric pressure of carbon monoxide at room temperature using a catalytic amount of PdCl2 and a stoichiometric amount of CuCl2.
- Tsuji, Jiro,Takahashi, Mitsuo,Takahashi, Takashi
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p. 849 - 850
(2007/10/02)
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