γ-Selective Allylation of (<i>E</i>)-Alkenylzinc Iodides Prepared by Reductive Coupling of Arylacetylenes with Alkyl Iodides
作者:Fedor E. Zhurkin、Xile Hu
DOI:10.1021/acs.joc.6b01306
日期:2016.7.1
allylic alkenylation using organozinc reagents are reported. (E)-Alkenylzinc iodides were prepared by Fe-catalyzed reductive coupling of terminal arylalkynes with alkyliodides. In the presence of a copper catalyst, these reagents reacted with allylic bromides derived from Morita–Baylis–Hillman alcohols to give 1,4-dienes in high yields. The reactions are highly γ-selective (generally γ/α > 49:1) and tolerate
Treatment of Baylis–Hillman adducts 1 with bromo(dimethyl)sulfonium bromide, Br(Me2)S+Br−, in MeCN was found to stereoselectively afford (Z)- and (E)-allyl bromides 2. The reaction is rapid at room temperature, high-yielding, and highly stereoselective.
A simple and facile stereoselective synthesis of (Z)- and (E)-allyl halides catalyzed by silica supported sodium hydrogen sulfate: factors influencing the yields and stereochemistry of allyl halides
A simple, mild and efficient stereoselective synthesis of (Z)- and (E)-allyl bromides and iodides has been developed by treatment of the Baylis–Hillman adducts with lithium bromide and iodide, respectively, in methylene chloride catalyzed by silica supported sodium hydrogensulfate at room temperature. The role of various solvents, different reacting metallic halides, nature of the adducts and activity
Asymmetric chemo- and regiospecific addition of organozinc reagents to Baylis–Hillman derived allylic electrophiles
作者:Christoph Börner、Paul J. Goldsmith、Simon Woodward、Josep Gimeno、Serafino Gladiali、Daniela Ramazzotti
DOI:10.1039/b006943o
日期:——
The copper-catalysed SN2â² addition of
ZnR2 to allylic
(Z)-ArCHC(CH2X)(CO2Et) (X = Br, Cl,
OSO2Me) fashions only
ArCH(R)C(CH2)(CO2Et); use of a chiral ligand
gives up to 64% ee for this demanding reaction.
Stable organozinc compounds derived from alkyl-3-alkyl-2-(bromomethyl)-proenoates have been prepared. NMR 13C, 1H and IR stidies show only one Z stereoisomer (no methylenic form) with a strong chelation between zinc and the carbonyl oxygen of the ester and solvated by only one solvent molecule. Hydrolysis can be achieved by two concurrent mechanisms with or without transposition.