Transition-Metal-Free Synthesis of Electron Rich 1,3-Dienes via Base Promoted Isomerization of Propargylic Ethers
作者:Chunxiang Liu、Guogang Deng、Xin Li、Yiren Xu、Kaili Yu、Wen Chen、Hongbin Zhang、Xiaodong Yang
DOI:10.1002/ejoc.201901743
日期:2020.1.31
An efficient and broadly applicable method for the construction of functionalized electron rich 1,3‐dienes through a base promoted isomerization reaction of propargylic ethers is presented. This process features easy handling reaction conditions, transition‐metal‐free isomerization, high isolated yields, and most of all, it could be used for late stage modification of natural products.
Some cationic η3-propargylpalladium complexes were prepared upon treatment of the corresponding η1-propargyl- or η1-allenylbis(triphenylphosphine)palladium(II) chloride with Ag[BF4] or Na[BPh4]. The effectiveness of the latter reagent suggests that a η1-propargyl- or η1-allenyl(chloro)palladium complex equilibrates with a cationic η3-propargylpalladium complex with the liberation of a Cl− ligand. A
γ-disubstituted propargylic tosylates was achieved by using metallic barium as the promoter. Various propargylated hydrazines (α-adducts) were exclusively synthesized from the corresponding propargylic tosylates and azobenzenes (diaryldiazenes). The thus-obtained propargylic hydrazines were further efficiently converted into propargylicamines by reductive N–N bond cleavage. Benzidine rearrangement of the propargylic
Highly Enantioselective and Regioselective Nickel-Catalyzed Coupling of Allenes, Aldehydes, and Silanes
作者:Sze-Sze Ng、Timothy F. Jamison
DOI:10.1021/ja0521831
日期:2005.5.25
three-component coupling reaction involving allenes, aldehydes, and organosilanes and transfers the axial chirality of the allene to a stereogenic center in the product with very high fidelity. An unexpected regioselectivity is observed; favored are allylic rather than homoallylic alcohol derivatives, corresponding to the unusual process of coupling two electrophilic atoms: the allene sp and aldehyde
Enantioselective and regioselective nickel-catalyzed multicomponent coupling of chiral allenes, aromatic aldehydes, and silanes
作者:Sze-Sze Ng、Timothy F. Jamison
DOI:10.1016/j.tet.2005.08.063
日期:2005.11
developed, nickel-catalyzed multicomponent coupling of chiral allenes, aromatic aldehydes, and silanes is described. The axial chirality of the allene is transferred completely to the product, a trisubstituted Z-allylic alcohol protected as a silyl ether. A very high preference for sp rather than sp2 coupling is observed, and differentially substituted allenes undergo highly site-selective coupling. These