Efforts Towards Control of Regioselectivity in the Gold(I) Catalyzed Hydration of Internal Alkynes. Effects of Solvent, Temperature and Substrate on Regioselectivity

Internal alkyne hydration using gold(I) catalysts often shows <5:1 regioselectivity. To explore factors that control selectivity, [(IPr)Au](+) paired with the weakly coordinating anion [IMP-H] was employed in additive free hydration reactions. Solvent influences the anti-Markovnikov selectivity of alkylarylacetylene hydration. Although temperature does not impact selectivity, [(IPr)Au(NCMe)][IMP-H] (C1) is an effective precatalyst for alkyl/alkyl and alkyl/aryl acetylenes at ambient temperature. Overall kinetic behavior of C1 resembles that of other Au hydrofunctionalization reactions of [(IPr)Au](+), where nucleophilic attack and/or proton transfer are turnover limiting. Prospects for improving regioselectivity are discussed.

Automated summary

This study investigates the factors that control the selectivity of internal alkyne hydration using gold(I) catalysts and finds that the choice of solvent influences the selectivity. At ambient temperature, using [(IPr)Au(NCMe)][IMP-H] (C1) as a precatalyst is effective for the hydration of alkyl/alkyl and alkyl/aryl acetylenes.