Synthesis of γ-Acetoxy β-Keto Esters Through Regioselective Hydration of γ-Acetoxy-α,β-alkynoates

Enantioselective Fluorination of α-Branched β-Ynone Esters Using a Cinchona-Based Phase-Transfer Catalyst

Herein, we report the fluorination of α-branched β-ynone esters to afford their corresponding quaternary fluorinated products with good enantioselectivity (ee = 73-90%) using a cinchona-based phase-transfer catalyst. α-Branched β-ynone esters possess a highly acidic α-proton and form their corresponding enolate as a single isomer, which allows the enantioselective fluorination reaction to occur under standard cinchona-based phase-transfer catalyst conditions. Moreover, the obtained α-fluorinated product can be treated with [(SPhos)AuNTf₂] (1 mol %) to afford a fluorinated 3,5-diketo carboxylic acid.

Synthesis of 1,4,6-Tricarbonyl Compounds via Regioselective Gold(I)-Catalyzed Alkyne Hydration and Their Application in the Synthesis of α-Arylidene-butyrolactones

We report a direct, straightforward, and regioselective hydration of 1,4-enynes designed from Morita-Baylis-Hillman adducts. Under smooth conditions and short reaction times, gold-catalyzed hydration of internal alkynes provides synthetically useful ketones as single regioisomers in yields higher than 90%. The synthetic usefulness of this protocol was demonstrated by the conversion of selected ketones into biologically valuable α-alkylidene-γ-lactones upon reduction with sodium borohydride. In the course of the scope evaluation, we discovered that this methodology could also furnish α-arylidene-β,γ-butenolides.

[3,3]-Acyloxy Rearrangement-Triggered Regioselective Hydration of δ-Acetoxy-α,β-Alkynoates/Halo Alkynes

Herein, we report a simple, efficient, highly regioselective, and broad-scope hydration method that is facilitated by an unusual interception of an electrophilic intermediate by water generated via acetate group participation during [3,3]-acyloxy rearrangement. Various carboxylate-directing groups including acetate, acrylates, pivalates, benzoate or its derivatives, and those derived from bioactive natural products were successfully implemented to direct the regioselective hydration for various functionalized δ-acyloxy-β-ketoester synthesis. The reaction pathway was further confirmed by ¹⁸O labeling experiments, and to the best of our knowledge, this is the first report of hydration through an electrophilic intermediate generated during [3,3]-acyloxy rearrangement. Synthetic application includes the synthesis of a modifiable C5-carbon chain, five-, six-, and seven-membered heterocycles, and natural product diversification.

Cascade cyclization and acyl migration of propargylic esters with isocyanides: rapid access to substituted furans

A novel rearrangement of ester-activated propargylic acetate with isocyanide has been disclosed. This protocol enables a quick synthesis of polysubstituted furan derivatives.

Gold-catalysed reactions of diynes

In this critical review the reactivity patterns observed with different types of diyne substrates in gold catalysis are discussed. Apart from the many examples from homogeneous catalysis, the few examples from heterogeneous gold catalysis are also included. With a proper arrangement of the two alkynes unique and exciting reactivity patterns like 1,3-carbonyl transpositions, carbene transfer reactions, cascade annulations, macrocyclisations or the formation of gold vinylidene intermediates are observed. These reactions are of interest for organic synthesis, for pharmaceutical and medicinal chemistry and for material science.

Theoretical insight into the Au(i)-catalyzed hydration of halo-substituted propargyl acetate: dynamic water-assisted mechanism

Three possible hydration pathways, including 1,5-exo-dig cycloaddition, 1,6-endo-dig cycloaddition, and direct water attack, have been considered and investigated by using DFT method and the cluster-continuum solvent model.

Gold-catalyzed diastereoselective synthesis of 2,6-trans-disubstituted tetrahydropyran derivatives: application for the synthesis of the C1–C13 fragment of bistramide A and B

An efficient Au(iii)-catalyzed diastereoselective allylation leading to 2,6-trans-disubstituted tetrahydropyrans and application for the synthesis of the C1–C13 fragment of bistramide A and B is described.