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

Abstract

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.

Gold catalysis in organic synthesis: efficient intramolecular cyclization of γ-acetylenic carboxylic acids to 5-exo-alkylidene-butyrolactones

“…Gold(I) was chosen for its easy handling ability and its lower sensitivity to moisture. The use of toluene, dichloromethane, or 1,2-dichloroethane led to the formation of the desired lactone in lower isolated yields (Table 1, entries [6][7][8]. The versatility of AuCl was then evaluated for other functionalized acid derivatives ( Table 2).…”

“…Various internal nucleophiles such as alkenyl, 2 sulfur-, 3 oxygen- 4 and nitrogen- 5 containing functions have been used in this regard. As part of our ongoing studies on metal-catalyzed atomeconomical reactions, 6 we have been interested in the use of gold for simple and highly efficient transformations. We have found that Au I catalyst promotes a highly efficient cycloisomerization of bis-homopropargylic diols under very mild conditions and in very short time.…”

Cycloisomerization of Acetylenic Acids to γ-Alkylidene Lactones using a Palladium(II) Catalyst Supported on Amino-Functionalized Siliceous Mesocellular Foam

“…Generally, this selectivity can be controlled by the choice of metal catalyst, as well as by careful design of the reaction conditions. Over the past years, numerous protocols based on transition-metals such as Rh, 6,7 Hg, [8][9][10][11] Ru, 12 Ag, [13][14][15] Au, [16][17][18][19] Cu 20,21 and Pd 6,14,[22][23][24][25][26][27][28] have been explored to allow for the synthesis of γ-alkylidene lactones. Unfortunately, most of these protocols require high catalyst loadings, prolonged reaction times, and/or elevated temperatures.…”

Water-Soluble Gold(I) and Gold(III) Complexes with SulfonatedN-Heterocyclic Carbene Ligands: Synthesis, Characterization, and Application in the Catalytic Cycloisomerization of γ-Alkynoic Acids into Enol-Lactones

“…12 It is worth mentioning that this catalytic transformation provides an easy and atom-economical entry to enol-lactones, an important class of functionalized heterocycles useful as synthetic intermediates. Although a large number of catalysts able to convert γ-alkynoic acids into enol-lactones are already known, 13,14 most of the reported procedures require water-free reaction conditions. In fact, only a few examples, involving Pd-, 15 Pt-, 16 and Cu-based systems, 17 active in aqueous environments have been described to date in the literature.…”