9 research outputs found
Rhodium-Catalyzed Carbonylation of 3-Acyloxy-1,4-enynes for the Synthesis of Cyclopentenones
Functionalized cyclopentenones were synthesized by a Rh-catalyzed carbonylation of 3-acyloxy-1,4-enynes, derived from alkynes and α,β-unsaturated aldehydes. The reaction involved a Saucy–Marbet 1,3-acyloxy migration of propargyl esters and a [4 + 1] cycloaddition of the resulting acyloxy substituted vinylallene with CO
Rhodium-Catalyzed Stereoselective Intramolecular [5 + 2] Cycloaddition of 3‑Acyloxy 1,4-Enyne and Alkene
The
first rhodium-catalyzed intramolecular [5 + 2] cycloaddition
of 3-acyloxy 1,4-enyne and alkene was developed. The cycloaddition
is highly diastereoselective in most cases. Various <i>cis</i>-fused bicyclo[5.3.0]Âdecadienes were prepared stereoselectively.
The chirality in the propargylic ester starting materials could be
transferred to the bicyclic products with high efficiency. Electron-deficient
phosphine ligand greatly facilitated the cycloaddition. Up to three
new stereogenic centers could be generated. The resulting diene in
the products could be hydrolyzed to enones, which allowed the introduction
of more functional groups to the seven-membered ring
Rhodium-Catalyzed Intra- and Intermolecular [5 + 2] Cycloaddition of 3-Acyloxy-1,4-enyne and Alkyne with Concomitant 1,2-Acyloxy Migration
A new type of rhodium-catalyzed [5 + 2] cycloaddition
was developed
for the synthesis of seven-membered rings with diverse functionalities.
The ring formation was accompanied by a 1,2-acyloxy migration event.
The five- and two-carbon components of the cycloaddition are 3-acyloxy-1,4-enynes
(ACEs) and alkynes, respectively. Cationic rhodiumÂ(I) catalysts worked
most efficiently for the intramolecular cycloaddition, while only
neutral rhodiumÂ(I) complexes could facilitate the intermolecular reaction.
In both cases, electron-poor phosphite or phosphine ligands often
improved the efficiency of the cycloadditions. The scope of ACEs and
alkynes was investigated in both the intra- and intermolecular reactions.
The resulting seven-membered-ring products have three double bonds
that could be selectively functionalized