54725-18-7Relevant articles and documents
One-Shot Radical Cross Coupling Between Benzyl Alcohols and Alkenyl Halides Using Ni/Ti/Mn System
Suga, Takuya,Takahashi, Yuuki,Ukaji, Yutaka
, p. 5622 - 5626 (2020/10/22)
A “one-shot” cross coupling between benzyl alcohols and alkenyl halides has been established. A combination of low-valent Ti-mediated C?OH homolysis and the prominent chemistry of Ni-based radical catalysis afforded the desired cross-coupled product with good efficiency. The reaction proceeded regardless of the electronic property of benzyl alcohols, and Ar?B bond remained intact throughout the reaction. Alkenyl bromides with various substitution patterns were applicable to this reaction. Attempts for utilizing sterically demanding tri-substituted alkenes indicated that the steric hinderance mainly inhibited the radical-trapping by Ni species. This reaction can be a simple and efficient strategy for synthesizing densely substituted allylbenzene derivatives. (Figure presented.).
Replacing C6F5 groups with Cl and H atoms in frustrated Lewis pairs: H2 additions and catalytic hydrogenations
Chernichenko,Kótai,Nieger,Heikkinen,Pápai,Repo
supporting information, p. 2263 - 2269 (2017/02/26)
2-(Dialkylamino)phenylboranes containing the BXZ group, where X, Z = C6F5, Cl, and H, were prepared in a few synthetic steps and demonstrated the cleavage of H2 under mild conditions. Depending on the nature of the dialkylamino group, X, and Z, the stability of the produced zwitterionic H2 adducts varies from isolated solids indefinitely stable in an inert atmosphere to those quickly equilibrating with the initial aminoborane and H2. Using a combined experimental/computational approach on a series of isostructural aminoboranes (dialkylamino = 2,2,6,6-tetramethylpiperid-1-yl), it was demonstrated that the electronegativity and the steric effect of the substituents generally follow the trend C6F5 ～ Cl ? H. This observation is useful for designing new FLPs for practical applications. As an example, we demonstrated the hydrogenation of alkynes to cis-alkenes under mild conditions that was catalyzed by a chloro-analogue of the C6F5-substituted aminoborane developed previously. The presence of a BHCl group in the aminochloroboranes or in their H2 adducts features facile redistribution of the H and Cl atoms and the formation of polychloro and polyhydrido species.
A frustrated-Lewis-pair approach to catalytic reduction of alkynes to cis-alkenes
Chernichenko, Konstantin,Madarasz, Adam,Papai, Imre,Nieger, Martin,Leskelae, Markku,Repo, Timo
, p. 718 - 723 (2013/08/23)
Frustrated Lewis pairs are compounds containing both Lewis acidic and Lewis basic moieties, where the formation of an adduct is prevented by steric hindrance. They are therefore highly reactive, and have been shown to be capable of heterolysis of molecular hydrogen, a property that has led to their use in hydrogenation reactions of polarized multiple bonds. Here, we describe a general approach to the hydrogenation of alkynes to cis-alkenes under mild conditions using the unique ansa-aminohydroborane as a catalyst. Our approach combines several reactions as the elementary steps of the catalytic cycle: hydroboration (substrate binding), heterolytic hydrogen splitting (typical frustrated-Lewis-pair reactivity) and facile intramolecular protodeborylation (product release). The mechanism is verified by experimental and computational studies.
An efficient nickel-catalyzed alkenylation of functionalized benzylic halides with alkenylaluminum reagents
Biradar, Deepak B.,Gau, Han-Mou
experimental part, p. 4243 - 4248 (2012/07/03)
Highly efficient and simple coupling reactions of benzylic bromides or chlorides with alkenylaluminum reagents catalyzed by NiCl2(PPh 3)2 are reported. The coupling reactions proceed effectively at room temperature employing low loading of catalyst, 0.5 mol% for benzylic bromides having either electron-donating or -withdrawing substituents on the aromatic ring, affording coupling products in excellent yields of up to 94% in short reaction times. The coupling reactions of benzylic chloride require 5 mol% of the catalyst and a longer reaction time of 2 h.
Alkynylsilanes as convenient precursors for the stereoselective synthesis of (E)-disubstituted alkenes
Zhao, Hong,Cai, Mingzhong
, p. 608 - 610 (2007/10/03)
Hydromagnesiation of alkynylsilanes 1 gives (Z)-α-silylvinyl Grignard reagents 2, which are reacted with alkyl iodides or aryl iodides in the presence of Cul or Pd(PPh3)4 catalysts to afford (Z)-1,2-disubstituted vinylsilanes 3 in good yields. Intermediates 3 can undergo a desilylation reaction to give (E)-disubstituted alkenes 4 in high yields.
Cobalt-catalyzed alkenylation of zinc organometallics
Avedissian, Hovsep,Berillon, Laurent,Cahiez, Gerard,Knochel, Paul
, p. 6163 - 6166 (2007/10/03)
Organozinc halides and diorganozincs undergo cross-coupling reactions with either E- or Z-alkenyl iodides in the presence of catalytic amounts of Co(acac)2 or Co(acac)3 in THF:NMP at 55°C leading to polyfunctional alkenes with retent
5-exo-trig Versus 6-endo-trig cyclization of Alk-5-enoyl radicals: The role of one-carbon ring expansion
Chatgilialoglu, Chryssostomos,Ferreri, Carla,Lucarini, Marco,Venturini, Alessandro,Zavitsas, Andreas A.
, p. 376 - 387 (2007/10/03)
Alk-5-enoyl radicals were made to cyclize in exo and endo modes to give the corresponding cycloketone radicals, which are related through one-carbon ring expansion. Relative kinetic data were determined for the ring closure of the 2-methylhept-5-enoyl radical generated by the reaction of the corresponding phenyl-seleno ester with Bu3SnH over the temperature range 233-323 K. The conversion to absolute rates provided Arrhenius expressions for the 5-exo-trig and 6-endo-trig cyclizations. Ab initio and semiempirical (AM1) calculations were performed on the hex-5-enoyl and hept-5-enoyl radicals, respectively, and the outcomes aided in the rationalization of the preexponential factors and activation energies. Both 1,5- and 1,6-ring closure occur via in a lower energy 'chairlike' transition state. The observed high regioselectivity is due to favorable entropic and enthalpic factors associated with the formation of the smaller ring. The stereoselectivity was higher in the 1,6-ring closure (70:30) than in the 1,5-ring closure (55:45), the trans isomer being predominant in both. For the one-carbon ring expansion studies, the radicals of interest were obtained by deoxygenation of suitable alcohols via the O-phenyl thiocarbonates with (TMS)3-SiH. The one-carbon ring expansion in the cyclopentanone series for the secondary alkyl radicals was studied over the temperature range 343-413 K by means of free-radical clock methodology and yielded the Arrhenius expression. The rate constant was 4.2 x 103 s-1 at room temperature and the reverse reaction (ring contraction) was found to be at least 10 times slower. Since the intermediacy of acyl radicals can be excluded, the reaction must occur via 3-membered cyclic intermediate radicals (or transition states).
HIGHLY SELECTIVE SYNTHESIS OF ALLYLATED ARENES AND DIARYLMETHANES VIA PALLADIUM-CATALYZED CROSS COUPLING INVOLVING BENZYLIC DERIVATIVES
Negishi, Ei-ichi,Matsushita, Hajime,Okukado, Nobuhisa
, p. 2715 - 2718 (2007/10/02)
The Pd-catalyzed cross coupling of either benzylzincs with alkenyl halides or alkenylalanes with benzyl halides provides highly selective and expeditious routes to allylated arenes.
THE PALLADIUM-CATALYSED CROSS-COUPLING REACTION OF 1-ALKENYLBORANES WITH ALLYLIC OR BENZYLIC BROMIDES. CONVENIENT SYNTHESIS OF 1,4-ALKADIENES AND ALLYLBENZENES FROM ALKYNES VIA HYDROBORATION
Miyaura, Norio,Yano, Takashi,Suzuki, Akira
, p. 2865 - 2868 (2007/10/02)
The reaction of allylic or benzylic bromides with 1-alkenyldisiamylboranes readily available from 1-alkynes in the presence of sodium hydroxyde and catalytic amounts of tetrakis-(triphenylphosphine)palladium to give corresponding 1,4-alkadienes or allylbe
