An efficient enantioselective synthesis of the ABC tricyclic core of the anticancer drug Taxol is reported. The key step of this synthesis is a cascade metathesis reaction, which leads in one operation to the required tricycle if appropriate fine-tuning of the dienyne precursor is performed.
Impregnated palladium on magnetite as a water compatible catalyst for the cycloisomerization of alkynoic acid derivatives
作者:Beatriz Saavedra、Juana M. Pérez、María J. Rodríguez-Álvarez、Joaquín García-Álvarez、Diego J. Ramón
DOI:10.1039/c8gc00229k
日期:——
This work describes the catalytic activity of palladium(II) species in the cycloisomerization of alkynoicacids and their derivatives in aqueous media as well as in Deep Eutectic Solvents (DESs), with one of the lowest metal catalyst loadings reported so far in the literature. Different substrates such as terminal and internal alkynes or alkynyl sulfonylimides were studied, obtaining selectivity either
Au<sub>2</sub>O<sub>3</sub> as a Stable and Efficient Catalyst for the Selective Cycloisomerization of γ-Acetylenic Carboxylic Acids to γ-Alkylidene-γ-Butyrolactones
The high potential of commercially available Au2O3 as a catalyst in the cyclization of alkynes bearing carboxylic acids to the corresponding γ-alkylidene-γ-butyrolactones through a general, efficient and easy procedure is presented. The reaction shows a high degree of chemo-, regio-, and stereoselectivity. The 5-exo mode of cyclization and anti auration are a general trend for the Au2O3 catalyst.
Cascade Metathesis Reactions for the Synthesis of Taxane and Isotaxane Derivatives
作者:Cong Ma、Aurélien Letort、Rémi Aouzal、Antonia Wilkes、Gourhari Maiti、Louis J. Farrugia、Louis Ricard、Joëlle Prunet
DOI:10.1002/chem.201600592
日期:2016.5.10
Tricyclic isotaxane and taxane derivatives have been synthesized by a very efficient cascade ring-closing dienyne metathesis (RCDEYM) reaction, which formed the A and B rings in one operation. When the alkyne is present at C13 (with no neighboring gem-dimethyl group), the RCEDYM reaction leads to 14,15-isotaxanes 16 a,b and 18 b with the gem-dimethyl group on the A ring. If the alkyne is at the C11
Northern–Southern Route to Synthetic Bacteriochlorins
作者:Yizhou Liu、Jonathan S. Lindsey
DOI:10.1021/acs.joc.6b02334
日期:2016.12.2
was prepared in five steps from an α-halopyrrole and a 2,2-dimethylpent-4-ynoic acid. The first three steps follow Jacobi’s synthesis of dihydrodipyrrins: Pd-mediated coupling to form a lactone–pyrrole, Petasis reagent treatment for methenylation, and Paal–Knorr type ring closure to form the 1,2,2-trimethyl-substituted dihydrodipyrrin. Subsequent steps entail conversion of the 1-methyl group to the