Palladium Nanoparticles in Water: A Reusable Catalytic System for the Cycloetherification or Benzannulation of α-Allenols
作者:Benito Alcaide、Pedro Almendros、Ana M. González、Amparo Luna、Sagrario Martínez-Ramírez
DOI:10.1002/adsc.201501132
日期:2016.6.16
A convenient ligand‐free catalyticsystem has been developed for the chemoselective cyclization reaction of various α‐allenol derivatives by palladiumnanoparticles (PdNPs) in an aqueous reaction medium.
A novel regioselective metal-catalyzed spirocyclization of alpha-allenols-cross coupling (Heck, Sonogashira, and Suzuki) reaction sequence, leading to potentially bioactive spirocyclic lactam derivatives has been developed. Precursors for the tandem spirocyclization-coupling reaction, alpha-allenols 2 a-d were obtained starting from alpha-oxolactams 1 a-c via indium-mediated Barbier-type carbonyl-allenylation
An Alternative to Precious Metals: Hg(ClO<sub>4</sub>)<sub>2</sub>·3H<sub>2</sub>O as a Cheap and Water-Tolerant Catalyst for the Cycloisomerization of Allenols
Hg(ClO4)(2)center dot 3H(2)O, a cheap, water-tolerant, and stable salt, catalyzes the cydoisomerization reaction or alpha-allenols to 2,5-dihydrofurans in an efficient and selective manner. The reaction is general and can be applied to differently functionalized substrates, including alkyl-substituted, aryl-substituted, enantiopure, and tertiary allenols. In addition, density functional theory (DFT) calculations were performed to obtain insight into various aspects of the controlled reactivity of a-allenols under mercury catalysis. They suggest a dual activation of the allenol by the Hg complex that drives the reaction to the chemoselective formation of 2,5-dihydrofurans.
Efficient Entry to Diversely Functionalized Spirocyclic Oxindoles from Isatins through Carbonyl-Addition/Cyclization Reaction Sequences
A novel approach to diversely functionalized spirocyclic oxindoles has been developed by using different metal-mediated carbonyl-addition/cyclization reaction sequences. Spirocyclization precursors, 2-indolinonetethered homoallylic alcohols, (buta-1,3-dien-2-yl)methanols, and alpha-allenols have been obtained by regioselective addition of stabilized organoindium reagents to isatins in aqueous environment. Ruthenium-, silver-, and palladium-catalyzed reactions of the above unsaturated alcohol derivatives provided oxaspiro oxindoles.
Gallium-Catalyzed Domino Arylation/Oxycyclization of Allenes with Phenols
作者:Benito Alcaide、Pedro Almendros、Fernando Herrera、Amparo Luna、M. Elena de Orbe、M. Rosario Torres
DOI:10.1021/acs.joc.5b00106
日期:2015.4.17
The synthesis of dihydrobenzofuran-appended oxindoles has been accomplished taking advantage of an unprecedented reaction between allenols and phenols under metal catalysis.