89039-13-4Relevant academic research and scientific papers
Kinetic isotope effects in cycloreversion of rhenium (V) diolates
Gable, Kevin P.,Zhuravlev, Fedor A.
, p. 3970 - 3979 (2002)
Cycloreversion of 4-methoxystyrene from the corresponding Tp′Re(O)(diolato) complex (Tp′ = hydrido-tris-(3,5-dimethylpyrazolyl)borate) was measured competitively for various isotopomers at 103 °C. Primary (12C/13C) and secondary (1H/2H) kinetic isotope effects were determined. The primary KIEs were k12C/k13C = 1.041 ± 0.005 at the α position and 1.013 ± 0.006 at the β position. Secondary KIEs were kH/kD = 1.076 ± 0.005 at the α position and 1.017 ± 0.005 at the β position. Computational modeling (B3LYP/LACVP*+) located a transition state for concerted cycloreversion of styrene from TpRe(O)(OCH2-CHPh) exhibiting dramatically different C-O bond lengths. A Hammett study on cycloreversions of substituted styrenes from a series of Tp′Re(O)(diolato) showed dichotomous behavior for electron donors and electron-withdrawing groups as substituents: ρ = -0.65 for electron donors, but ρ = +1.13 for electron-withdrawing groups. The data are considered in light of various mechanistic proposals. While the extrusion of 4-methoxystyrene is concluded to be a highly asynchronous concerted reaction, the Hammett study reflects a likelihood that multiple reaction mechanisms are involved.
On the Origin of E/Z Selectivity in the Modified Julia Olefination - Importance of the Elimination Step
Robiette, Raphael,Pospisil, Jiri
supporting information, p. 836 - 840 (2013/03/29)
The mechanism and origin of high E selectivity in the modified Julia olefination of aromatic aldehydes have been explored by computational and experimental means. Reversibility of addition and hence selectivity of the formation of sulfinate 5 is very variable and depends on the nature of the sulfone substrate. However, in all cases, elimination occurs through a concerted antiperiplanar and synperiplanar mechanism for sulfinates anti-5 and syn-5, respectively. Both syn and anti diastereomeric pathways thus lead preferentially to the (E)-alkene. Copyright
α-Selective Ni-catalyzed hydroalumination of aryl- and alkyl-substituted terminal alkynes: Practical syntheses of internal vinyl aluminums, halides, or boronates
Gao, Fang,Hoveyda, Amir H.
supporting information; scheme or table, p. 10961 - 10963 (2010/09/17)
A method for Ni-catalyzed hydroalumination of terminal alkynes, leading to the formation of α-vinylaluminum isomers efficiently (>98% conv in 2-12 h) and with high selectivity (95% to >98% α), is described. Catalytic α-selective hydroalumination reactions proceed in the presence of a reagent (diisobutylaluminum hydride; dibal-H) and 3.0 mol % metal complex (Ni(dppp)Cl2) that are commercially available and inexpensive. Under the same conditions, but with Ni(PPh3)2Cl2, hydroalumination becomes highly β-selective, and, unlike uncatalyzed transformations with dibal-H, generates little or no alkynylaluminum byproducts. All hydrometalation reactions are reliable, operationally simple, and practical and afford an assortment of vinylaluminums that are otherwise not easily accessible. The derived α-vinyl halides and boronates can be synthesized through direct treatment with the appropriate electrophiles [e.g., Br 2 and methoxy(pinacolato)boron, respectively]. Ni-catalyzed hydroaluminations can be performed with as little as 0.1 mol % catalyst and on gram scale with equally high efficiency and selectivity.
THE ROLE OF ELECTRONIC FACTORS IN REAGENTS IN CONTROLLING THE STEREOCHEMISTRY OF ARYLSULFENYL CHLORIDES ADDITION
Bodrikov, I.V.,Borisov, A.V.,Smit, W.A.,Lutsenko, A.I.
, p. 4983 - 4986 (2007/10/02)
For a series of substituted arylsulfenyl chlorides the stereochemistry of AdE-reactions with a series of substituted Z- and E-β-deuterostyrenes has been elucidated.Non-stereospecific reaction was observed only for the pair 2,4-dinitrobenzenesul
