Pentacenequinone-stabilized silver nanoparticles: A reusable catalyst for the diels-alder [4 + 2] cycloaddition reactions
Silver nanoparticles (AgNPs) stabilized by aggregates of derivative 4 have been used as catalyst for the construction of synthetically and biologically important [4 + 2] cycloadducts at room temperature.
β- and γ-disubstituted olefins: Substrates for copper-catalyzed asymmetric allylic substitution
The copper-catalyzed asymmetric allylic alkylation has shown through many examples that it is a powerful means to generate stereogenic centers with mono β- and γ-substituted olefinic substrates. However, little has been reported about more substituted olefinic patterns, such as β-disubstituted allylic electrophiles. In this paper, we show that a simple procedure using easily accessible Grignard reagents and as low as 3 mol% of copper/ligand can promote high to nearly perfect enantioselectivities (up to >99% ee) with very good γ-selectivities on a wide panel of aliphatic or aromatic β-disubstituted substrates.
Ethynyl Ortho Esters as Precursors of Propargyl Cations. The Low-Temperature, Ionic Diels-Alder Addition of Ethyl Propiolate to 1,3-Dienes via Ethynyl Ortho Esters
3,3,3-Triethoxypropyne (triethyl orthopropiolate) was added to a series of 1,3-dienes at low temperature in the presence of trimethylsilyl triflate to yield the 4? + 2? products of the formal addition of ethyl propiolate to the 1,3-dienes.
Gassman, Paul G.,Chavan, Subhash P.
p. 3407 - 3410
(2007/10/02)
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