3,3′-Anisyl-Substituted BINOL, H<sub>4</sub>BINOL, and H<sub>8</sub>BINOL Ligands: Asymmetric Synthesis of Diverse Propargylic Alcohols and Their Ring-Closing Metathesis to Chiral Cycloalkenes
作者:Yang Yue、Mark Turlington、Xiao-Qi Yu、Lin Pu
DOI:10.1021/jo9018446
日期:2009.11.20
aldehydes. It catalyzed the reactions of alkyl propiolates with 88−99% ee; the reactions of phenylacetylene with 81−87% ee; the reactions of 4-phenyl-1-butyne, an alkyl alkyne, with 77−89% ee; and the reactions of trimethylsilylacetylene with 92−97% ee. The optically active propargylic alcohols generated from this catalytic asymmetric alkyne addition were observed to undergo efficient ring-closing-metathesis
Addition of zinc homoenolates to acetylenic esters and amides: a formal [3 + 2] cycloaddition
作者:Michael T. Crimmins、Philippe G. Nantermet、B. Wesley Trotter、Isabelle M. Vallin、Paul S. Watson、Lynne A. McKerlie、Tracy L. Reinhold、Adrian Wai Hing Cheung、Katherine A. Stetson
DOI:10.1021/jo00057a013
日期:1993.2
The copper-catalyzed conjugate addition-cycloacylation reaction of zinc homoenolates with acetylenic esters or acetylenic amides is described. The zinc homoenolate is prepared from [(ethoxycyclopropyl)oxy]trimethylsilane and zinc chloride in ether. Addition of an acetylenic amide or ester provides 2-carboxamido-or 2-carboalkoxy-3-alkylcyclopent-2-en-1-ones in good to excellent yields. The reaction can be carried out in the presence of a variety of sensitive functional groups including epoxides, alpha,beta-unsaturated esters, acetals, silyl ethers, and furans.
[GRAPHICS]Additions of terminal alkynes to electrophiles are important transformations in organic chemistry. Generally, activated terminal alkynes react with epoxides in an S(N)2 fashion to form homopropargylic alcohols. We have developed a new synthetic method to form propargylic alcohols from epoxides and terminal alkynes via 1,2-shifts. This method involves cationic zirconium acetylides as both the activator of epoxides and nucleophiles. line to the mild conditions to pre-activate alkynes with silver nitrate, this synthetic method is useful for both electron-rich and electron-deficient alkynes with other acid- and base-sensitive functional groups.
Base-Catalyzed Highly Stereoselective Conversion of γ-Hydroxy-α,β-acetylenic Esters to γ-Acetoxy Dienoates
作者:Yang Yue、Xiao-Qi Yu、Lin Pu
DOI:10.1002/chem.200802355
日期:2009.5.11
A convenient route with high stereo control to γ‐acetoxy dienoates is provided by the reaction of methyl propiolate with aldehydes in the presence of ZnEt2 and N‐methylimidazole at room temperature, followed by the catalytic conversion of the resulting γ‐hydroxy‐α,β‐acetylenic esters with p‐N,N‐dimethylaminopyridine (DMAP) in acetic anhydride (see scheme).