26447-63-2Relevant 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
supporting information, 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.).
Controllable, Sequential, and Stereoselective C-H Allylic Alkylation of Alkenes
Qin, Ling,Sharique, Mohammed,Tambar, Uttam K.
, p. 17305 - 17313 (2019/11/03)
The direct conversion of C-H bonds into new C-C bonds represents a powerful approach to generate complex molecules from simple starting materials. However, a general and controllable method for the sequential conversion of a methyl group into a fully substituted carbon center remains a challenge. We report a new method for the selective and sequential replacement of three C-H bonds at the allylic position of propylene and other simple terminal alkenes with different carbon groups derived from Grignard reagents. A copper catalyst and electron-rich biaryl phosphine ligand facilitate the formation of allylic alkylation products in high branch selectivity. We also present conditions for the generation of enantioenriched allylic alkylation products in the presence of catalytic copper and a chiral phosphine ligand. With this approach, diverse and complex products with substituted carbon centers can be generated from simple and abundant feedstock chemicals.
Oxygenation of Simple Olefins through Selective Allylic C?C Bond Cleavage: A Direct Approach to Cinnamyl Aldehydes
Liu, Jianzhong,Wen, Xiaojin,Qin, Chong,Li, Xinyao,Luo, Xiao,Sun, Ao,Zhu, Bencong,Song, Song,Jiao, Ning
supporting information, p. 11940 - 11944 (2017/09/20)
A novel metal-free allylic C?C σ-bond cleavage of simple olefins to give valuable cinnamyl aldehydes is reported. 1,2-Aryl or alkyl migration through allylic C?C bond cleavage occurs in this transformation, which is assisted by an alkyl azide reagent. This method enables O-atom incorporation into simple unfunctionalized olefins to construct cinnamyl aldehydes. The reaction features simple hydrocarbon substrates, metal-free conditions, and high regio- and stereoselectivity.
Catalytic, oxidant-free, direct olefination of alcohols using Wittig reagents
Khaskin,Milstein
supporting information, p. 9002 - 9005 (2015/05/27)
Reported here is the catalytic, acceptorless coupling of alcohols with in situ generated, non-stabilized phosphonium ylides to form olefins as major products. The reaction uses low catalyst loadings and does not require added oxidants. Hydrogenation of the product is minimized and the reaction leads to Z (aliphatic) or E (benzylic) stereospecificity.
Selective formation of non-conjugated olefins by samarium(II)-mediated elimination/isomerization of allylic benzoates
Schaefer, Sara L.,Roberts, Connor L.,Volz, Erasmus O.,Grasso, Monika R.,O'Neil, Gregory W.
, p. 6125 - 6128 (2013/10/22)
Aromatic allylic benzoates can be selectively transformed to the corresponding benzoate eliminated olefin by the action of samarium diiodide. Depending on the substrate and the elimination conditions, high selectivity for the non-conjugated alkene product
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).
Fluorination of secondary and primary alcohols by thermal decomposition of electrochemically generated alkoxy triphenylphosphonium tetrafluoroborates
Maeda, Hatsuo,Koide, Takashi,Matsumoto, Sayaka,Ohmori, Hidenobu
, p. 1480 - 1483 (2007/10/03)
Replacement of hydroxyl groups in secondary and primary alcohols (1) with a fluorine atom arising from tetrafluoroborate anion has been performed by the electrochemical formation of alkoxy triphenylphosphonium tetrafluoroborates (2) from 1, followed by their thermal decomposition. The procedure is quite simple, involving: (1) constant-current electrolysis of a mixture of 1, Ph3P, and Ph3PH·BF4 in CH2Cl2 in an undivided cell; (2) refluxing a tetrahydrofuran or dioxane solution of the residue afforded by evaporation of the solvent in vacuo after the electrolysis. Cyclic secondary alcohols such as 3β-hydroxy steroids and 2-adamantanol are transformed into the corresponding fluorides in satisfactory yields when the geometry of the leaving group in 2 is suitable for the substitution or an elimination process for 2 to give an alkene is stereochemically forbidden. The fluorination of steroidal alcohols and 4-phenyl-1-cyclohexanol proceeded with complete inversion, demonstrating that a fluorine atom from the tetrafluoroborate anion attacks from the side opposite to the phosphonium moiety in 2 via an SN2 mechanism rather than an SN1 mechanism. The fluorination of acyclic secondary and primary alcohols was performed by the present method in reasonable yields, although the reaction for the latter required more forcing conditions, such as refluxing in dioxane.
