4588-18-5Relevant academic research and scientific papers
Enantioselectivity of chiral zirconocenes as catalysts in alkene hydro-, carbo- and cycloalumination reactions
Parfenova, Lyudmila V.,Berestova, Tatyana V.,Tyumkina, Tatyana V.,Kovyazin, Pavel V.,Khalilov, Leonard M.,Whitby, Richard J.,Dzhemilev, Usein M.
experimental part, p. 299 - 310 (2010/06/14)
The enantioselectivity of chiral Zr catalysts L1L2ZrCl2 [L1 = L2 = 1-neomenthylindenyl (Ind*), 1; L1 = Cp, L2 = Ind* 2; L1 = Cp, L2 = 1-neomenthylindenyl-4,5,6,7-tetrahydroindenyl (Cp*) 3] in the hydro-, carbo- and cycloalumination of alkenes by organoaluminium compounds (OAC) (AlMe3, AlEt3, HAlBu2i) has been studied. It was found that OAC exhibit the most effect on the reaction chemo- and enantioselectivity. The reaction chemo- and enantioselectivity depend on the catalyst structure and reaction conditions (solvent type, catalyst concentration, temperature) as well. It is shown that the lack of asymmetric induction in the reaction of α-methylstyrene hydroalumination by HAlBu2i, catalyzed with complexes 1 or 3, is the result of the formation of Zr hydride complexes of different structures as reaction intermediates. MTPA was used as a derivatization reagent for the enantiomeric excess estimation and absolute configuration assignment of β-chiral alcohols obtained after the oxidation and hydrolysis of the reaction products. The applicability of MTPA for the assignment of the absolute configuration of the stereogenic centre in β-ethyl substituted primary alcohols and β-alkyl-1,4-butanediols is shown.
SILVER-CATALYZED REDUCTIVE DEHALOGENATION OF 1,1-DIBROMOCYCLOPROPANES
Shimizu, Nobujiro,Watanabe, Kenji,Tsuno, Yuho
, p. 1877 - 1878 (2007/10/02)
1,1-Dibromocyclopropanes underwent rapid reduction to the corresponding monobromides in high yields on treating with LiAlH4 - 1 molpercent silver perchlorate in THF, presumably via a silver-catalyzed radical chain mechanism.
R3Cu2M Species: Convenient cuprates for the conversion of 1-alkynes into 1-alkenes
Westmijze, H.,Kleijn, H.,Meijer, J.,Vermeer, P.
, p. 98 - 102 (2007/10/02)
The paper describes reactions of 1-alkynes, R1-CC-H, with new cuprate species of the type R3Cu2M .Under suitably chosen conditions a smooth transfer of R (Me or Et) from the cuprates to the 1-alkynes (R1 = Ph or n-C6H13) could be realized.The resulting stereospecifically generated adducts 1C=CH)xCu2R3-x>Mg (Cl or Br) were stable under the conditions of the reactions, provided that a sufficient amount of lithium bromide was present.In the absence of lithium bromide substantial decomposition of the adducts into RR1C=CH-CH=CRR1 took place.During the reaction of PhCCH with Me3Cu2Li the addition reaction was accompanied by deprotonation, which could be proved by using PhCCD as starting alkyne.Deprotonation in PhC-CH as side-reaction also occured with Me3Cu2MgBr.The latter complex was prepared from MeMgBr and CuBr.The number of R groups which are transferrable from R3Cu2M to R1-CCH with an acceptable rate appeared to depend on the nature of R, viz. one R group in the case of Me3Cu2M and all three R groups in the case of Et3Cu2M.
