20826-49-7Relevant academic research and scientific papers
Cobalt(II)-Catalyzed Stereoselective Olefin Isomerization: Facile Access to Acyclic Trisubstituted Alkenes
Zhang, Sheng,Bedi, Deepika,Cheng, Lu,Unruh, Daniel K.,Li, Guigen,Findlater, Michael
supporting information, p. 8910 - 8917 (2020/12/23)
Stereoselective synthesis of trisubstituted alkenes is a long-standing challenge in organic chemistry, due to the small energy differences between E and Z isomers of trisubstituted alkenes (compared with 1,2-disubstituted alkenes). Transition metal-catalyzed isomerization of 1,1-disubstituted alkenes can serve as an alternative approach to trisubstituted alkenes, but it remains underdeveloped owing to issues relating to reaction efficiency and stereoselectivity. Here we show that a novel cobalt catalyst can overcome these challenges to provide an efficient and stereoselective access to a broad range of trisubstituted alkenes. This protocol is compatible with both mono- and dienes and exhibits a good functional group tolerance and scalability. Moreover, it has proven to be a useful tool to construct organic luminophores and a deuterated trisubstituted alkene. A preliminary study of the mechanism suggests that a cobalt-hydride pathway is involved in the reaction. The high stereoselectivity of the reaction is attributed to both a π-πstacking effect and the steric hindrance between substrate and catalyst.
Method for stereoselective synthesis of (E)-trisubstituted olefin
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Paragraph 0043-0048; 0103-0105, (2020/04/02)
Belonging to the technical field of metal catalytic synthesis, the invention discloses a method for stereoselective synthesis of (E)-trisubstituted olefin. The method includes: taking 1, 1-disubstituted olefin as the raw material, and adopting a combination of CoX2 and PAO ligand as the catalyst; and in the presence of an activating reagent, carrying out reaction for 0.5min-48h at a temperature ranging from -30DEG C to 80DEG C to prepare (E)-trisubstituted olefin. Compared with the prior art, the method has the advantages of more economical, efficient and environment-friendly catalyst, good tolerance of the reaction functional group, mild reaction conditions, simple operation, no need for participation of additional reagents, and atom economy of 100%. In addition, the reaction has no needof any other toxic transition metal (like ruthenium, rhodium, palladium, etc.) salt, therefore the method has great practical application value in pharmaceutical and food chemical industry.
P-Chiral Monophosphorus Ligands for Asymmetric Copper-Catalyzed Allylic Alkylation
Xiong, Wenrui,Xu, Guangqing,Yu, Xinhong,Tang, Wenjun
, p. 4003 - 4013 (2019/06/24)
Asymmetric copper-catalyzed allylic alkylation between allyl bromides and alkyl Grignard reagents using a P-chiral monophosphorus ligand is described. A range of terminal olefins bearing tertiary or quaternary carbon centers were formed in good branched/linear selectivities and excellent enantioselectivities at copper loadings as low as 0.5 mol %.
Palladium-catalyzed double-bond migration of unsaturated hydrocarbons accelerated by tantalum chloride
Murai, Masahito,Nishimura, Kengo,Takai, Kazuhiko
supporting information, p. 2769 - 2772 (2019/03/23)
The operationally simple palladium-catalyzed double-bond migration without heteroatom-containing coordinating functional groups is described. Addition of TaCl5 as a second catalyst greatly enhanced the migration efficiency to provide β-alkylsty
Enantioselective Oxidative Rearrangements with Chiral Hypervalent Iodine Reagents
Brown, Michael,Kumar, Ravi,Rehbein, Julia,Wirth, Thomas
supporting information, p. 4030 - 4035 (2016/03/16)
A stereoselective hypervalent iodine-promoted oxidative rearrangement of 1,1-disubstituted alkenes has been developed. This practically simple protocol provides access to enantioenriched α-arylated ketones without the use of transition metals from readily
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.
Capture of in situ generated diazo compounds or copper carbenoids by triphenylphosphine: Selective synthesis of trans-alkenes and unsymmetric azines via reaction of aldehydes with ketone-derived N-tosylhydrazones
Sha, Qiang,Ling, Yifei,Wang, Wenyong,Wei, Yunyang
supporting information, p. 2145 - 2150 (2013/10/01)
Copper(II) acetylacetonate-catalyzed Wittig olefination reactions of aldehydes with ketone-derived N-tosylhydrazones are reported. A series of tosylhydrazones was investigated and our results showed that the carbon number of the alkyl chain influences the E-selecivity of the alkenes greatly. Alkenes could be obtained in moderate yields and excellent E-selectivity when the carbon numbers were up to two. Under metal-free conditions, triphenylphosphine was able to capture the in situ generated diazo compounds and the corresponding unsymmetrical azines were formed in good yields.
Short synthesis of chiral 4-substituted (S)-imidazolinium salts bearing sulfonates and their use in γ-selective reactions of allylic halides with grignard reagents
Latham, Christopher M.,Blake, Alexander J.,Lewis, William,Lawrence, Matthew,Woodward, Simon
supporting information; experimental part, p. 699 - 707 (2012/03/11)
A one-pot reaction of Boc-protected amino alcohols and 2-sulfobenzoic anhydride followed by the addition of a wide variety of primary amines has allowed rapid access to diverse libraries of amidosulfonates 1,2-C 6H4(SO3su
The design and synthesis of novel IBiox N-heterocyclic carbene ligands derived from substituted amino-indanols
Levy, Jean-No?l,Latham, Christopher M.,Roisin, Lo?c,Kandziora, Nadine,Fruscia, Paolo Di,White, Andrew J. P.,Woodward, Simon,Fuchter, Matthew J.
supporting information; experimental part, p. 512 - 515 (2012/02/04)
A synthetic route towards a number of novel IBiox N-heterocyclic carbene (NHC) ligands has been developed. The resulting ligands have restricted flexibility and high steric demand. Preliminary studies have shown these ligands to give high levels of asymmetric induction in the copper-free allylic alkylation of cinnamyl bromide.
Silicon-(thio)urea Lewis acid catalysis
Hrdina, Radim,Mueller, Christian E.,Wende, Raffael C.,Lippert, Katharina M.,Benassi, Mario,Spengler, Bernhard,Schreiner, Peter R.
supporting information; experimental part, p. 7624 - 7627 (2011/06/26)
We present a new class of catalysts based on the combination of N,N′-diaryl(thio)ureas and weak silicon Lewis acids (e.g., SiCl 4). Such silicon-(thio)urea catalysts effectively catalyze the stereospecific rearrangement of epoxides to quaternary carbaldehydes.
