6230-62-2Relevant academic research and scientific papers
Catalyst-Controlled Chemodivergent Reactions of 2-Pyrrolyl-α-diazo-β-ketoesters and Enol Ethers: Synthesis of 1,2-Dihydrofuran Acetals and Highly Substituted Indoles
France, Stefan,Guerra Faura, Gabriel,Nguyen, Tena
supporting information, p. 10088 - 10104 (2021/07/31)
A catalyst-controlled, chemodivergent reaction of pyrrolyl-α-diazo-β-ketoesters with enol ethers is reported. While Cu(II) catalysts selectively promoted a [3 + 2] cycloaddition to provide pyrrolyl-substituted 2,3-dihydrofuran (DHF) acetals, dimeric Rh(II) catalysts afforded 6-hydroxyindole-7-carboxylates via an unreported [4 + 2] benzannulation. The choice of enol ether proved to be crucial in determining both regioselectivity and yield of the respective products (up to 91% yield for Cu(II) and 82% for Rh(II) catalysis). Furthermore, the DHF acetals were shown to serve as precursors to 7-hydroxyindole-6-carboxylates (isomeric to the indoles formed from Rh) and highly substituted furans in the presence of Lewis acids. Thus, from a common pyrrolyl-α-diazo-β-ketoester, up to three unique heterocyclic scaffolds can be achieved based on catalyst selection.
Interrogating Pd(II) Anion Metathesis Using a Bifunctional Chemical Probe: A Transmetalation Switch
Molloy, John J.,Seath, Ciaran P.,West, Matthew J.,McLaughlin, Calum,Fazakerley, Neal J.,Kennedy, Alan R.,Nelson, David J.,Watson, Allan J. B.
supporting information, p. 126 - 130 (2018/01/17)
Ligand metathesis of Pd(II) complexes is mechanistically essential for cross-coupling. We present a study of halide→OH anion metathesis of (Ar)PdII complexes using vinylBPin as a bifunctional chemical probe with Pd(II)-dependent cross-coupling pathways. We identify the variables that profoundly impact this event and allow control to be leveraged. This then allows control of cross-coupling pathways via promotion or inhibition of organoboron transmetalation, leading to either Suzuki-Miyaura or Mizoroki-Heck products. We show how this transmetalation switch can be used to synthetic gain in a cascade cross-coupling/Diels-Alder reaction, delivering borylated or non-borylated carbocycles, including steroid-like scaffolds.
A facile solid-phase synthesis of vinyl ethers using a selenium traceless linker
Liu, Xiao-Ling,Sheng, Shou-Ri,Wang, Qiu-Ying,Sun, Wu-Kang,Xin, Qin,Ao, Hong-Yu
, p. 118 - 120 (2007/10/03)
A simple, efficient and environmentally friendly procedure for the solid-phase synthesis of vinyl ethers in good yields and purities by reaction of polystyrene-supported 2-hydroxyalkyl selenide with primary or secondary organic halides and subsequent oxid
Convenient one-pot synthesis of vinyl ethers from phenyl 2-hydroxyalkyl selenides
Sheng, Shou-Ri,Luo, Hai-Rong,Sun, Wu-Kang,Liu, Xiao-Ling,Xin, Qin,Wang, Qiu-Ying
, p. 2839 - 2845 (2007/10/03)
Vinyl ethers were prepared with good yields in a one-pot, two-step transformation by O-alkylation reaction of phenyl 2-hydroxyalkyl selenides with primary or secondary organic halides followed by oxidation elimination with 30% hydrogen peroxide. Copyright
Ionic liquid-promoted, highly regioselective Heck arylation of electron-rich olefins by aryl halides
Mo, Jun,Xu, Lijin,Xiao, Jianliang
, p. 751 - 760 (2007/10/03)
Palladium-catalyzed regioselective Heck arylation of the electron-rich olefins, vinyl ethers 1a-d, enamides 1e-g, and allyltrimethylsilane 1h, has been accomplished in imidazolium ionic liquids with a wide range of aryl bromides and iodides instead of the commonly used, but commercially unavailable and expensive, aryl triflates. The reaction proceeded with high efficiency and remarkable regioselectivity without the need for costly or toxic halide scavengers, leading exclusively to substitution by aryl groups of diverse electronic and steric properties at the olefinic carbon α to the heteroatom of 1a-g and β to the heteroatom of 1h. In contrast, the arylation reaction in molecular solvents led to mixtures of regioisomers under similar conditions. Several lines of evidence point to the unique regiocontrol stemming from the ionic environment provided by the ionic liquid that alters the reaction pathway. The chemistry provides a simple, effective method for preparing branched, arylated olefins and contributes to the extension of Heck reaction to a wider range of substrates.
Dichloromethane as an unusual methylene equivalent. A new entry of highly nucleophilic and selective titanium-methylene complexes for ester methylenation
Yan, Tu-Hsin,Chien, Ching-Ting,Tsai, Chia-Chung,Lin, Kuo-Wei,Wu, Yen-Hsien
, p. 4965 - 4967 (2007/10/03)
(Chemical Equation Presented) The successful application of CH 2Cl2-Mg-TiCl4-system mediated methylenation of various esters such as tert-butyl ester and 2,5-cyclohexadiene-1-carboxylate highlights the extraordinary reactivity, selectivity, and the nonbasic nature of this new methylene-carbenoid, which serves as a practical reagent applicable to large-scale synthesis.
Mono-, di-, tribromoethenyl alkyl ethers in cross-coupling reactions with grignard reagents catalyzed by palladium and nickel complexes
Glazunova,Lutsenko,Efimova,Trostyanskaya,Kazankova,Beletskaya
, p. 1104 - 1111 (2007/10/03)
Reaction of mono-, di-, and tribromoethenyl alkyl ethers with phenylmagnesium bromide and trialkylsilylmethylmagnesium chloride in the presence of catalytic quantities of nickel or palladium complexes afforded α and β-alkoxystyrenes and 2- or 3-alkoxyally
On the Nature of the "Copper Effect" in the Stille Cross-Coupling
Farina, Vittorio,Kapadia, Suresh,Krishnan, Bala,Wang, Chenjie,Liebeskind, Lanny S.
, p. 5905 - 5911 (2007/10/02)
The effect of added CuI on the kinetics of a typical Stille coupling was studied.With triphenylphosphine as Pd ligand, cocatalytic Cu(I) salts can yield a > 100-fold rate increase over the traditional Stille conditions, but little effect was displayed when CuI was used in conjunction with a soft ligand, such as triphenylarsine.NMR studies suggest that CuI is an excellent scavenger for free ligand and, since strong ligands in solution are known to inhibit the rate-limiting transmetalation, one effect of copper salts is readily explained.In addition, however, when working in highly dipolar solvents like NMP and in the absence of strong ligands, unsaturated stannanes react with CuI to yield presumably an organocopper species, which then transmetalates to Pd(II).An example of altered group transfer selectivity due to cocatalytic copper is given, and it is suggested that this strategy may be of some general value.
Palladium-Catalyzed Coupling Reactions of (α-Ethoxyvinyl)trimethylstannane with Vinyl and Aryl Triflates
Kwon, Hyok Boong,McKee, Blain H.,Stille, J. K.
, p. 3114 - 3118 (2007/10/02)
The palladium-catalyzed cross-coupling reaction of vinyl triflates and halides with (α-ethoxyvinyl)trimethylstannane gives high yields of 2-ethoxy 1,3-dienes, which can be hydrolyzed to the corresponding α,β-unsaturated ketones.Aryl triflates undergo an analogous coupling reaction, providing a facile method for replacing the hydroxyl group of a phenol by an acyl group.The use of (α-ethoxyvinyl)trimethylstannane in palladium-catalyzed carbonylative coupling gives rise to vinyl and aryl α-ethoxyvinyl ketones and indirectly to the corresponding α-diketones (which result from their hydrolysis) and glyoxylates (which result from their ozonolysis).
Organic Syntheses via Transition Metal Complexes, 36. - Monofunctional Tri(methylene)methane Chromium and Iron Complexes by Addition of Allenes to M=C Bonds of Carbene Complexes
Aumann, Rudolf,Trentmann, Beate
, p. 1977 - 1982 (2007/10/02)
The reaction of carbenechromium and -iron complexes 1a and 1b with monofunctional allenes H2C=C=CH-CH2Y 2 (Y = OH, CO2Et, CH2OH) leads to the formation of tri(methylene)methane complexes 3 in good yields with insertion of 2 into the M=C bond of 1.The stereochemistry of this key reaction is markedly influenced by the metal moiety.Thus, with the (octahedral) chromium complex 1a only one stereoisomer 3-A is obtained, but with the (trigonal-bipyramidal) iron complex 1b a mixture of diastereomers 3-A-C is formed.On the other hand, the iron complex 1a yields 3 as the only product, while the chromium complex 1b in addition to 3 also gives an enol ether 4 by a metathesis reaction. - Key Words: Tri(methylene)methane chromium and iron complexes / Allenes, insertion into M=C bonds of carbene complexes / Metathesis of allenes / 2- and 3-Methylenemetallacyclobutanes
