Gold-catalyzed Cyclization Reactions Research Articles

ChemInform Abstract: An Efficient Synthesis of Polysubstituted Naphthalene Derivatives by Gold‐Catalyzed Cyclization of 1‐Arylalka‐2,3‐dienyl Acetates.

An efficient synthetic strategy to generate differently polysubstituted naphthalenes and iodonaphthalenes through a gold-catalyzed cyclization reaction of 1-arylalka-2,3-dienyl acetates was described. Due to the substituent loading capability of both the aromatic ring and the allene moiety, different substituents may be introduced to the different locations of the naphthalenes. A possible mechanism of the reaction involving the formation of alkenyl and naphthyl Au species was proposed on the basis of the mechanistic study. Iodination of the gold species afforded iodonaphthalenes, which are useful building blocks to introduce molecular complexity and diversity by coupling reactions.

Stereoselective synthesis of tetracyclic indolines via gold-catalyzed cascade cyclization reactions

A reliable synthetic route to fused polycyclic indolines is documented by the development of a stereoselective gold catalyzed cascade cyclization of indole propargylic alcohols.

Gold-Catalyzed Tandem Cyclizations of 1,6-Diynes Triggered by Internal N- and O-Nucleophiles

Investigations on gold-catalyzed tandem cyclization reactions of 1,6-diynes, tethered to nucleophilic functionalities such as amine, carboxylic acid, amide, and sulfonamide, are reported. The ability of such substrates to undergo tandem cyclization, triggered by internal nucleophiles, has been examined. Depending on the substrate, the catalytic system, and reaction conditions, different regioisomers of monocyclic and bridged bicyclic products were obtained.

Synthesis of pyrroloazepinones: platinum- and gold-catalyzed cyclization reactions of alkynes

The synthesis of potentially bioactive pyrroloazepinones based on the catalytic intramolecular cyclization of alkyne-substituted 1 H-pyrrole-2-carboxylic acid amides has been developed. In the presence of either H 2PtCl 6·6H 2O at 120 °C or AuCl 3 at room temperature pyrrolo[3,2- c]azepin-4-ones are formed.

Gold-Catalyzed Cyclizations of 1,6-Diynes

New gold-catalyzed cyclization reactions of 1,6-diynes (2,2-dipropargylmalonates) are reported. Symmetrically (Me, Et) and unsymmetrically disubstituted (Me, Et, Ph) 1,6-diynes provided stereoselectively the Z-cyclopentylidene derivatives in 31-60% and 49-83% yield, respectively. High regioselectivity (97:3) was obtained for the cyclization of Me/Ph-substituted 1,6-diynes. A monosubstituted terminal diyne afforded a cyclopentene derivative (2-acetyl-3-alkylcyclopent-2-ene-1,1-dicarboxylate, 43%), while the diterminal 1,6-diyne (2,2-di(prop-2-ynyl)malonate) produced a cyclohexenone derivative (3-methyl-5-oxocyclohex-3-ene-1,1-dicarboxylate, 61%). Plausible reaction mechanisms are proposed for the formation of the products.

Gold-Catalyzed Cyclization Reaction of Alkynyl O-tert-Butylcarbamates

Gold-catalyzed cyclization of alkynyl O-tert-butylcarbamates having N-benzyloxy group provided the 6-endo cyclized products selectively. Cascade reaction of O-tert-butylcarbamates having an enyne moiety was also examined.

Gold-Catalyzed Highly Efficient Access to 3(2H)-Furanones from 2-Oxo-3-butynoates and Related Compounds

[reaction: see text] The gold-catalyzed cyclization reactions of 2-oxo-3-butynoic esters or disubstituted-1,2-diones with a variety of nucleophiles are described, which offer an efficient and straightforward route to substituted 3(2H)-furanones under mild reaction conditions. The Au(III) catalysts are also highly effective in the hydration of these activated alkynes.

Room Temperature Au(I)-Catalyzed exo-Selective Cycloisomerization of Acetylenic Acids: An Entry to Functionalized γ-Lactones

A highly efficient gold-catalyzed cyclization reaction of various functionalized acetylenic acids is described. The cyclizations are conducted in the presence of Au(I) catalyst in acetonitrile at room temperature in a short reaction time. The reaction conditions are compatible with several functional groups, such as ester, alkene, alkyne, chloro, and free or protected alcohol, and lead to original gamma-lactones in good to excellent yields.