Efficient Intramolecular Cyclizations of Phenoxyethynyl Diols into Multisubstituted α,β-Unsaturated Lactones
摘要:
AgOTf-catalyzed intramolecular cyclization of phenoxyethynyl diols proceeded under mild conditions to afford the multisubstituted alpha,beta-unsaturated-gamma-lactones in 55-98% yields. This method was also applicable to the synthesis of alpha,beta-unsaturated-delta-lactones. A similar cyclization proceeded when AgOTf was replaced with a stoichiometric amount of N-bromosuccinimide to furnish the a-bromo-substituted alpha,beta-unsaturated lactones.
Palladium-catalyzed Cycloaddition of Alkynyl Aryl Ethers to Allenes to Form a 2,3-Bismethylidene-2,3-dihydro-4<i>H</i>-1-benzopyran Framework
作者:Yasunori Minami、Mayuko Kanda、Tamejiro Hiyama
DOI:10.1246/cl.130894
日期:2014.2.5
Palladium-catalyzed cycloaddition of alkynyl aryl ethers to allenes proceeds through o-C–H activation to give 2,3-dihydro-4H-1-benzopyran derivatives containing 2,3-exo-double bonds. These benzopyr...
and reduces the activation energy. Many types of carbon nucleophiles such as silyl ketene acetals, silyl ketene imines, a silyl cyanide, an alkynyl stannane, and an allylic stannane were applicable to the present reaction system to give highly functionalized metalated enol ethers (β-alkoxyalkenylindiums). The prepared β-alkoxyalkenylindiums were transformed to various functionalized tetrasubstituted
Gold Catalysis: Switching the Pathway of the Furan-Yne Cyclization
作者:A. Stephen K. Hashmi、Matthias Rudolph、Jürgen Huck、Wolfgang Frey、Jan W. Bats、Melissa Hamzić
DOI:10.1002/anie.200900887
日期:2009.7.27
Changing tracks: By the use of alkynyl ethers as directing elements, the furan‐yne cyclization enters a new reaction pathway. Instead of phenols, tetracycles containingtwoheteroatoms and two new stereocenters are formed (see scheme).
Total synthesis of dimeric <i>Securinega</i> alkaloids (−)-flueggenines D and I
作者:Sangbin Jeon、Jinwoo Lee、Sangbin Park、Sunkyu Han
DOI:10.1039/d0sc03057k
日期:——
describe the total synthesis of (−)-flueggenines D and I. This features the first total synthesis of dimeric Securinega alkaloids with a C(α)–C(δ′) connectivity between two monomeric units. The key dimerization was enabled by a sequence that involves Stille reaction and conjugate reduction. The high chemofidelity of the Stille reaction enabled us to assemble two structurally complex fragments that could
Alkynyl aryl ethers react with internal alkynes through selective ortho C-H activation by a palladium(0) catalyst to give substituted 2-methylidene-2H-chromenes. The alkynoxy group acts as a directing group to promote ortho C-H functionalization. Deuterium-labeling experiments indicated that the arylpalladium hydride complex is a key intermediate via oxidative addition. Various functional groups tolerate