The intermolecular hydro-oxycarbonylation of internal alkynes: current state of the art

Abstract

The intermolecular addition of carboxylic acids to alkynes is one of the most straightforward and atomeconomical methods currently available for the preparation of synthetically useful enol esters. However, the vast majority of works have focused on the use of terminal alkynes, substrates much more reactive than their corresponding internal counterparts. In fact, efficient and general protocols for hydro-oxycarbonylation of internal alkynes have only seen the light in recent years. In the present review article an overview of the progress made in the field is given. Catalytic reactions promoted by ruthenium, palladium, silver and gold complexes/salts, along with some specific metal-free protocols, are covered.

Catalytic Hydrofunctionalization Reactions of 1,3-Diynes

“…Addition of carboxylic acids to alkynes catalyzed by transition metals represents one of the most efficient ways to prepare synthetically useful enol esters [175][176][177][178]. Among the different catalytic systems reported to date, gold complexes have emerged in recent years as the most effective, as they can be successfully applied in the hydro-oxycarbonylation, not only of terminal alkynes, but also of the more challenging internal ones [179].…”

Metal-Catalyzed Synthesis and Transformations of β-Haloenol Esters

“…For example, alkenyl halides are widely used as substrates in transition metal-catalyzed cross-coupling reactions [1,2] and can be easily converted, through a metal-halogen exchange, into nucleophiles for 1,2additions to carbonyl compounds [3]. Enol esters are also relevant olefinic derivatives with multitude of applications in modern organic chemistry [4][5][6]. The introduction of a halogen atom on the C=C bond of the latter leads to functionalized molecules, i.e., α-and β-haloenol esters (Figure 1), in which the reactivities of the haloalkene and enol ester functionalities can be combined and potentially exploited in numerous synthetic ways.…”

Gold(I) Complexes with Ferrocenylphosphino Sulfonate Ligands: Synthesis and Application in the Catalytic Addition of Carboxylic Acids to Internal Alkynes in Water

“…However, the vast majority of studies have focused on the hydro-oxycarbonylation of terminal alkynes. Examples of the intermolecular addition of carboxylic acids to internal alkynes still remain scarce [18], and in most of the cases, only activated substrates, such as trifluoromethylated alkynes [19], acetylenic esters [20], ynol ethers [21], ynamides [22], or iodoalkynes [23], have been considered. For nonactivated internal alkynes, only a very limited number of gold-and cobalt-based catalysts have proven effective under mild conditions (temperatures below 100 • C) [24][25][26][27].…”