Highly Regioselective Fluorination and Iodination of Alkynyl Enolates
摘要:
A simple yet efficient approach to various functionalized quaternary alpha-alkynyl alpha-fluoro esters and gamma-iodoallenoates from readily available allenoates through an alkynyl enolate intermediate generated by LDA is presented. Reaction of this alkynyl enolate with NFSI gives the alpha-product (alpha-alkynyl-alpha-fluoro ester), whereas the reaction of the silyl ether of alkynyl enolate with I-2 gives solely the gamma-product (iodoallenoate).
Ferric Chloride Hexahydrate-Catalyzed Highly Regio- and Stereoselective Conjugate Addition Reaction of 2,3-Allenoates with Grignard Reagents: An Efficient Synthesis of β,γ-Alkenoates
作者:Guobi Chai、Zhan Lu、Chunling Fu、Shengming Ma
DOI:10.1002/adsc.200900091
日期:2009.8
Ferricchloride hexahydrate was shown to be an efficient catalyst for the conjugate addition of 2,3-allenoates with alkyl-, aryl-, or vinyl-Grignard reagents to synthesize polysubstituted β,γ-unsaturated alkenoates with high regio- and stereoselectivity. The in situ formed magnesium dienolate may readily react with different electrophilic reagents under different reaction conditions with or without
CuCl-catalyzed stereoselective conjugate addition of Grignard reagents to 2,3-allenoates
作者:Jian He、Zhan Lu、Guobi Chai、Chunling Fu、Shengming Ma
DOI:10.1016/j.tet.2012.01.027
日期:2012.3
CuCl was found to be an efficient catalyst for the conjugateaddition of 2,3-allenoates with Grignardreagents to synthesize poly-substituted β,γ-unsaturated alkenoates with high stereoselectivity in good to excellent yields. Primary, secondary, and tertiary alkyl, vinyl or phenyl Grignardreagents may all be used.
Studies on the Intermolecular Hydroarylation of N-Ts- or N-Ac-Protected Indoles and 2,3-Allenoates
作者:Zhao Fang、Chunling Fu、Shengming Ma
DOI:10.1002/ejoc.201001661
日期:2011.3
An operationally simple, TFA-promoted regioselective hydroarylation reaction of 2,3-allenoates with N-Ts- or N-Ac-indoles to afford 4-indolyl-4-arylbut-2-enoates is described. A series of substrates was tested, and the E/Z selectivity was found to depend on the reaction temperature and time. A mechanism involving the formation of E and Z allylic carbocations generated in situ from the reaction of 2
Michael Addition of Allenoates to Electron-Deficient Olefins: Facile Synthesis of 2-Alkynyl-Substituted Glutaric Acid Derivatives
作者:Le-Ping Liu、Bo Xu、Gerald B. Hammond
DOI:10.1021/ol801411b
日期:2008.9.1
A Michaeladdition of allenoates to electron-deficientolefins was mediated efficiently by a catalytic amount of commercial tetra-n-butylammonium fluoride (TBAF) under mild conditions. And 2-alkynyl substituted glutaric acid derivatives, which may be potential building blocks in organic synthesis, were obtained in good to excellent yields from these reactions. The mechanism for the Michael addition
Highly Efficient and Tunable Synthesis of Dioxabicyclo[4.2.1] Ketals and Tetrahydropyrans via Gold-Catalyzed Cycloisomerization of 2-Alkynyl-1,5-diols
作者:Le-Ping Liu、Gerald B. Hammond
DOI:10.1021/ol902215n
日期:2009.11.5
A highly efficient gold(I) chloride catalyzed cycloisomerization of 2-alkynyl-1,5-diol (1) to dioxabicyclo[4.2.1] ketal (2) and its further transformation to tetrahydropyran (3) are reported. The diol is readily obtained by the reduction of 2-alkynyl-substituted glutarates, isolated from the Michael addition of allenoates to methyl acrylate. These reactions proceeded smoothly under very mild conditions