38454-63-6Relevant academic research and scientific papers
Titanocene(III)-Catalyzed Precision Deuteration of Epoxides
Gans?uer, Andreas,H?thker, Sebastian,Henriques, Dina Schwarz G.,Klare, Sven,Mika, Regine,Rojo-Wiechel, Elena,Schacht, Jonathan H.,Schmickler, Niklas
supporting information, (2021/12/24)
We describe a titanocene(III)-catalyzed deuterosilylation of epoxides that provides β-deuterated anti-Markovnikov alcohols with excellent D-incorporation, in high yield, and often excellent diastereoselectivity after desilylation. The key to the success of the reaction is a novel activation method of Cp2TiCl2 and (tBuC5H4)2TiCl2 with BnMgBr and PhSiD3 to provide [(RC5H4)2Ti(III)D] without isotope scrambling. It was developed after discovering an off-cycle scrambling with the previously described method. Our precision deuteration can be applied to the synthesis of drug precursors and highlights the power of combining radical chemistry with organometallic catalysis.
Iron Catalyzed Isomerization of α-Alkyl Styrenes to Access Trisubstituted Alkenes
Xu, Songgen,Liu, Guixia,Huang, Zheng
, p. 585 - 589 (2021/02/01)
Stereoselective isomerization of α-alkyl styrenes is accomplished using a new iron catalyst supported by phosphine-pyridine-oxazoline (PPO) ligand. The protocol provides an atom-efficient and operationally simple approach to trisubstituted alkenes in high
Method for stereoselective synthesis of (E)-trisubstituted olefin
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Paragraph 0043-0048, (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.
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.
Cobalt-Catalyzed Migrational Isomerization of Styrenes
Zhao, Jiajin,Cheng, Biao,Chen, Chenhui,Lu, Zhan
supporting information, p. 837 - 841 (2020/01/31)
An efficient cobalt-catalyzed migrational isomerization of styrenes was developed using the thiazoline iminopyridine (TIP) ligand. This reaction is operationally simple and atom-economical using readily available starting materials to access trisubstituted alkenes. Even when using a 0.1 mol % catalyst loading, the reaction could be conducted in neat and completed in 1 h with excellent conversion and high E stereoselectivity.
Regioselective Diboron-Mediated Semireduction of Terminal Allenes
Gates, Ashley M.,Santos, Webster L.
, p. 4619 - 4624 (2019/12/11)
A method for the regioselective reduction of the terminal double bond of 1,1-disubstituted allenes has been developed. In the presence of a palladium catalyst, tetrahydroxydiboron and stoichiometric water, allene semireduction proceeds in high yield to afford Z-alkenes selectively.
Copper-Catalyzed Oxidative Cleavage of Electron-Rich Olefins in Water at Room Temperature
Lippincott, Daniel J.,Trejo-Soto, Pedro J.,Gallou, Fabrice,Lipshutz, Bruce H.
supporting information, p. 5094 - 5097 (2018/09/13)
A copper-catalyzed oxidative cleavage of electron-rich olefins into their corresponding carbonyl derivatives is described as an alternative to ozonolysis. The scope includes various precursors to aryl ketone derivatives, as well as oxidations of enol ethers bearing atypical alkyl and dialkyl substitution, the first of their kind among such metal catalyzed alkene cleavage reactions. The use of an inexpensive copper salt, room temperature conditions, an aerobic atmosphere, and water as the global reaction medium highlight the green features of this new method. Associated mechanistic investigations are also presented.
Enantioselective Oxy-Heck–Matsuda Arylations: Expeditious Synthesis of Dihydrobenzofuran Systems and Total Synthesis of the Neolignan (?)-Conocarpan
Silva, Allan R.,Polo, Ellen C.,Martins, Nelson C.,Correia, Carlos Roque D.
, p. 346 - 365 (2018/01/26)
This work discloses the first examples of an effective enantioselective oxy-Heck–Matsuda reaction using a variety of styrenic olefins to generate chiral dihydrobenzofurans. The reaction proceeds in moderate to good yields, with high trans diastereoselectivity (up to 20:1) in enantioselectivities up to 90:10 using the N,N-ligand pyrimidine-bisoxazoline (PyriBox). The oxy-Heck–Matsuda reactions were carried out under mild conditions and rather low catalyst loadings. The feasibility and practicality of the process is demonstrated by a concise total synthesis of the neolignan (?)-conocarpan. X-ray diffraction of an advanced brominated intermediate in the route to (?)-conocarpan has allowed the unequivocal assignment of the absolute stereochemistry of the oxy-Heck–Matsuda aryldihydrobenzofuran products. A rationale for the mechanism operating in these enantioselective oxy-Heck–Matsuda reactions is also presented. (Figure presented.).
Al(OTf)3: An efficient lewis acid additive for domino addition-elimination of Grignard reagents to activated ketones
Pieterse, Tanya,Visser, Melanie,Marais, Charlene,Bezuidenhoudt, Barend C. B.
supporting information, p. 1541 - 1546 (2016/06/14)
It has been demonstrated that aluminium triflate in either stoichiometric or catalytic quantities facilitates the addition-elimination of Grignard reagents to electron-rich ketones, such as methoxy substituted acetophenones, propiophenone and chromanone in a one-pot process, and that it has an enhancing effect on the addition of these reagents to the ketones. It has also been found that the reactions are highly stereoselective towards one regioisomer of the alkene in the case of oxygenated aryl-alkyl substituted substrates, but not when the elimination originates from a double benzylic alcohol intermediate.
Trifluoromethylation of aromatic alkenes by visible-light-driven photoredox catalysis: Direct conversion of alkenes to 3-trifluoromethyl-1-propenyl and 1,3-bis(trifluoromethyl)-1-propenyl derivatives
Asano, Masashi,Tomita, Ren,Koike, Takashi,Akita, Munetaka
supporting information, p. 83 - 88 (2015/11/10)
Photoredox-catalyzed trifluoromethylation of alkenes using Umemoto's reagent as a CF3 source under visible light irradiation has been developed. A Ru photocatalyst, [Ru(bpy)3](PF6)2 (bpy = 2,2′-bipyridine), is useful for the present trifluoromethylation and preferable formation of 3-trifluoromethyl-1-propenyl derivatives is observed. Use of an excess amount of Umemoto's reagent readily induces double trifluoromethylation of electron-rich alkenes, resulting in 1,3-bis(trifluoromethyl)-1-propenyl skeleton.
