The Asymmetric Aza-Claisen Rearrangement: Development of Widely Applicable Pentaphenylferrocenyl Palladacycle Catalysts
作者:Daniel F. Fischer、Assem Barakat、Zhuo-qun Xin、Matthias E. Weiss、René Peters
DOI:10.1002/chem.200900712
日期:2009.9.7
has a broader substrate tolerance than all previously known catalyst systems for asymmetric aza‐Claisen rearrangements. Our investigations also reveal that subtle changes can have a big impact on the activity. With the enhanced catalyst activity, the asymmetric aza‐Claisen rearrangement has a very broad scope: the methodology not only allows the formation of highly enantioenriched primary allylic amines
by ethyl (2E)-4-hydroxy-2-alkenoates. Ethyl 2-cycloalkylidene-2-phenylsulfinylacetates were found to be more susceptible to pyrolysis. The enoate esters (2) undergo migration of their carbon-carbon double bond and then [2,3]sigmatropic rearrangement to benzene-sulfenate esters, followed by thermolytic extrusion of a benzenesulfenic acid probably via ethyl (2E)-4-phenyl-sulfinyl-2-alkenoates to afford
Highly Selective Synthesis of <i>Z</i>-Unsaturated Esters by Using New Horner−Emmons Reagents, Ethyl (Diarylphosphono)acetates
作者:Kaori Ando
DOI:10.1021/jo970057c
日期:1997.4.1
New Horner-Emmons reagents, ethyl (diarylphosphono)acetates 1, were prepared from triethyl phosphonoacetate, PCl(5), and the corresponding phenols. The reaction of 1 with several kinds of aldehydes in the presence of Triton B or NaH in THF solvent revealed that these reagents are useful for the synthesis of Z-unsaturated esters. Among the reagents examined, ethyl(di-o-tolylphosphono)-, [bis(o-ethylphenyl)phosphono]-
Asymmetric addition of (triisopropylsilyl)acetylene to α,β,γ,δ-unsaturated carbonyl compounds took place in the presence of a cobalt/Duphos catalyst to give the 1,6-addition products in high yields with high regio- and enantioselectivity.
Stereoselective Synthesis of 2Z,4E-Configured Dienoates through Tethered Ring Closing Metathesis
作者:Bernd Schmidt、Stephan Audörsch、Oliver Kunz
DOI:10.1055/s-0035-1562536
日期:——
is described. The sequence involves Steglich esterification of the reactants, followed by a one-pot ringclosing metathesis–base induced elimination–alkylation reaction to furnish the products in high stereoselectivity. Trapping of the intermediate sodium carboxylates is accomplished efficiently using Meerwein’s salt Et3OBF4. A two-step sequence leading from racemic allylic alcohols and vinylacetic