Ligand- and Bronsted acid/base-switchable reaction pathways in gold(I)-catalyzed cycloisomerizations of allenoic acids

Gold-promoted cyclizations of 2,2-diaryl substituted gamma-allenoic acids were found to give three isomeric lactone products, each of which could be obtained selectively by exploiting Bronsted acid/base and ligand effects. Simple 5-exo-trig cyclization products were favored by strong donor ligands o...

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Published inOrganic & biomolecular chemistry Vol. 13; no. 13; pp. 3936 - 3949
Main Authors Handa, Sachin, Subramanium, Sri S., Ruch, Aaron A., Tanski, Joseph M., Slaughter, LeGrande M.
Format Journal Article
LanguageEnglish
Published CAMBRIDGE Royal Soc Chemistry 07.04.2015
Subjects
Chemistry
Chemistry, Organic
Physical Sciences
Science & Technology
RELAY CATALYSIS
INTRAMOLECULAR HYDROARYLATION
GOLD-CATALYZED CYCLOISOMERIZATION
INTERMOLECULAR HYDROARYLATION
SKELETAL REARRANGEMENT
TRIFLIC ACID
STEREOSELECTIVE IODOLACTONIZATION
HIGHLY EFFICIENT
CARBOXYLIC-ACIDS
CATIONIC GOLD
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Summary:Gold-promoted cyclizations of 2,2-diaryl substituted gamma-allenoic acids were found to give three isomeric lactone products, each of which could be obtained selectively by exploiting Bronsted acid/base and ligand effects. Simple 5-exo-trig cyclization products were favored by strong donor ligands or base additives, whereas weak donor ligands and a Bronsted acid additive gave isomeric enelactones resulting from double bond migration. Further optimization afforded a class of medicinally relevant bridged tricyclic lactones via a tandem hydroacyloxylation/hydroarylation process. Kinetic studies and control experiments indicated that the initial 5-exo-trig cyclization product serves as a branch point for further isomerization to the other lactone products via cooperative gold(I)/Bronsted acid catalysis.
Bibliography:National Science Foundation
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ISSN:1477-0520
1477-0539
DOI:10.1039/c4ob02640c