- Ynamide Carbopalladation: A Flexible Route to Mono-, Bi- and Tricyclic Azacycles
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Bromoenynamides represent precursors to a diversity of azacycles by a cascade sequence of carbopalladation followed by cross-coupling/electrocyclization, or reduction processes. Full details of our investigations into intramolecular ynamide carbopalladation are disclosed, which include the first examples of carbopalladation/cross-coupling reactions using potassium organotrifluoroborate salts; and an understanding of factors influencing the success of these processes, including ring size, and the nature of the coupling partner. Additional mechanistic observations are reported, such as the isolation of triene intermediates for electrocyclization. A variety of hetero-Diels-Alder reactions using the product heterocycles are also described, which provide insight into Diels-Alder regioselectivity.
- Campbell, Craig D.,Greenaway, Rebecca L.,Holton, Oliver T.,Walker, P. Ross,Chapman, Helen A.,Russell, C. Adam,Carr, Greg,Thomson, Amber L.,Anderson, Edward A.
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supporting information
p. 12627 - 12639
(2015/09/01)
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- Stille coupling involving bulky groups feasible with gold cocatalyst
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Gold shuttle: Bulky groups, which will not (or only very sluggishly) undergo Stille coupling with stannanes and inexpensive ligands, can be efficiently coupled using bimetallic catalysis. A gold cocatalyst serves as an efficient shuttle to convey the bulky group from tin to palladium by reducing the steric crowding in the transition-states (see scheme). Copyright
- Delpozo, Juan,Carrasco, Desiree,Perez-Temprano, Monica H.,Garcia-Melchor, Max,Alvarez, Rosana,Casares, Juan A.,Espinet, Pablo
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supporting information
p. 2189 - 2193
(2013/04/10)
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- A novel mode of access to polyfunctional organotin compounds and their reactivity in Stille cross-coupling reaction
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Mono-, di-, tri- and tetra-functional organotin compounds were easily prepared in a sonicated Barbier reaction using ultrasound technology via coupling reaction of organo halides with tin halides (Bu3SnCl, Bu2SnCl2, BuSnCl
- Lamandé-Langle, Sandrine,Abarbri, Mohamed,Thibonnet, Jér?me,Duchêne, Alain
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p. 2368 - 2374
(2009/09/30)
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- H NMR evidence for the formation of vinyllead triacetates. The reactions of vinylmercury, vinyltin, and vinylboronic acids with lead tetraacetate
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Vinylmercury compounds, vinylboronic acids and vinylstannanes undergo rapid metal-lead exchange with lead tetraacetate in deuterochloroform to generate vinyllead triacetates, which have been characterised by their 1H-1H and 207Pb-1H coupling constants. In addition, a number of divinyl and mixed aryl-vinyllead dicarboxylates have been prepared via boron-lead exchange.
- Parkinson, Christopher J.,Stoermer, Martin J.
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p. 207 - 214
(2007/10/03)
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- Regioselective addition of stannylcyanocuprates to acetylenic ethers: A chemical and spectroscopic study
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The reactions of acetylenic ether 1 with higher order cuprates 2a, 2b and 2c were studied chemically and spectroscopically. Conditions were developed to efficiently and regioselectively prepare α- and β-stannylvinyl ethers. 1H and 13C NMR studies of these reactions suggest that in the presence of HMPA, higher order stannylcyanocuprate, (Bu3Sn)2Cu(CN)Li2, 2a, exists in equilibrium with Gilman cuprate, (Bu3Sn)2CuLi.
- Cabezas,Oehlschlager
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p. 432 - 442
(2007/10/02)
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- Stannyl-cupration of Acetylenes and the Reaction of the Intermediate Cuprates with Electrophiles as a Synthesis of Substituted Vinylstannanes
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Stannyl-cupration of acetylenes followed by electrophilic attack with a variety of electrophiles gives E-vinylstannanes.These can be used either to form acetylenes, thus achieving overall the addition of an ethynyl group, or to form carbon-carbon bonds in Stille reactions.
- Barbero, Asuncion,Cuadrado, Purificacion,Fleming, Ian,Gonzalez, Ana M.,Pulido, Francisco J.,Rubio, Rosa
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p. 1657 - 1662
(2007/10/02)
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- The Stannyl-Cupration of Acetylenes and the Reaction of the Intermediate Cuprates with Electrophiles as a Synthesis of Substituted Vinylstannanes
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Stannyl-cupration of acetylenes followed by electrophilic attack with a variety of electrophiles gives vinylstannanes.
- Barbero, Asuncion,Cuadrado, Purificacion,Fleming, Ian,Gonzalez, Ana M.,Pulido, Francisco J.
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p. 351 - 353
(2007/10/02)
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- Palladium- or Nickel-Catalyzed Reactions of Alkenylmetals with Unsaturated Organic Halides as a Selective Route to Arylated Alkenes and Conjugated Dienes: Scope, Limitations, and Mechanism
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Stereo- and regiodefined alkenylmetals containing Al, Zr, and Zn react with aryl and alkenyl iodides and bromides in the presence of catalytic amounts of Pd or Ni complexes containing phosphine ligands, such as PPh3, to give the corresponding cross-coupled products.Palladium catalysts permit nearly 100 percent stereospecificity in both alkenyl-aryl and alkenyl-alkenyl coupling reactions, whereas nickel catalysts lead to partial stereochemical scrambling in the alkenyl-alkenyl coupling.Although many other metals including Li, Mg, Cd, Hg, B, Si, Sn, Ti, and Ce were also used, the results were inferior to those obtained with Al, Zr, and Zn under the conditions used in the present study.The turnover numbers for the palladium-catalyzed reactions of PhI with (E)-1-octenylmetals containing Al, Zr, and Zn were 2,3, and > 2000 mmol of (E)-1-octenylbenzene (8) per mmol of Pd(PPh3)4 per hour at room temperature, respectively.The stoichiometric reaction of PhPd(PPh3)2I (6) with 1.2 equiv of (E)-1-octenylzinc chloride (7) in a 2:1 mixture of CD2Cl2 and THF was examined in detail.The reaction follows second-order konetics (k2 = 2.9 L/(mol.min) at 0 deg C) to give 8 without the buildup of any intermediate.The results are consistent with a slow formation of 9 via transmetalation followed by its rapid reductive elmination to give 8 and "Pd(PPhe3)2".Addition of PhI to the reaction mixture rapidly gives 6 in 98 percent yield, supporting the plausibility of the proposed oxidative addition step.These results are consistent with the proposed mechanism consisting of oxidative addition of Pd(0) complexes, rate-determining transmetalation involving Pd(II) complexes, and rapid decomposition of diorganopalladium(II) species to produce the coupling products in one or more subsequent steps.The rate-determining transmetalation step provides an explanation for the effect of metals in organometallic reagents used stoichiometrically.
- Negishi, Ei-ichi,Takahashi, Tamotsu,Baba, Shigeru,Horn, David E. Van,Okukado, Nobuhisa
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p. 2393 - 2401
(2007/10/02)
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