Gold(I)-Catalyzed Divergence in the Preparation of Bicyclic Enol Esters: From Exclusively [3C+2C]-Cycloaddition Reactions to Exclusive Formation of Vinylcyclopropanes

Gold(I)-Catalyzed Reactions of exo-Glycals with Propargyl Esters toward C-1 Alkenyl Spirocyclopropyl Carbohydrates

An atom-economic and diazo-free strategy for the construction of novel pseudo anomeric C-1 alkenyl spirocyclopropyl sugars is described. Leveraging the 1,2-migration pathway of propargyl esters under gold(I) catalysis, easily available exo-glycals undergo β-selective alkenylcarbenoid insertion in moderate to excellent yields. Preferential activation of propargyl moieties and concerted [2 + 1] insertion are both favored through ligand choice and electron enrichment of esters. Stereocontrol using conformational bias and rearrangement are also demonstrated.

Gold-Catalyzed Addition of Propargyl Acetates to Olefins via O-Acyl Migration/Cyclopropanation Sequence: Insight into the Diastereoselective Formation of the Alkene

This article discloses a study on the well-known addition of propargyl acetates to olefins via an O-acyl migration/cyclopropanation sequence. Herein, we show that the stereochemical outcome of the olefin is strongly dependent on the gold catalyst and reaction parameters (concentration, temperature, and alkene partner equivalents); the E- and Z-isomers can be selectively formed by the judicious choice of reaction conditions.

Metal-free catalytic hydrocarboxylation of hexafluorobut-2-yne

An efficient method for stereoselective synthesis of trifluorinated enol esters catalyzed by base was introduced.

Gold-Catalyzed Synthesis of Small Rings

Three- and four-membered rings, widespread motifs in nature and medicinal chemistry, have fascinated chemists ever since their discovery. However, due to energetic considerations, small rings are often difficult to assemble. In this regard, homogeneous gold catalysis has emerged as a powerful tool to construct these highly strained carbocycles. This review aims to provide a comprehensive summary of all the major advances and discoveries made in the gold-catalyzed synthesis of cyclopropanes, cyclopropenes, cyclobutanes, cyclobutenes, and their corresponding heterocyclic or heterosubstituted analogs.

Enantioselective Synthesis of Dihydropyran-Fused Indoles through [4+2] Cycloaddition between Allenoates and 3-Olefinic Oxindoles

A highly enantioselective [4+2] annulation with respect to allenoates and 3-olefinic oxindoles catalyzed by Lewis base was reported, which proved to be an efficient way to synthesize chiral dihydropyran-fused indoles. The cycloaddition products were generally obtained in high yields (up to 98%) with very good enantioselectivities (up to 94% enantiomeric excess).