Catalytic Hydration of Alkynes and Its Application in Synthesis

ABSTRACT The catalytic addition of water to alkynes (hydration) generates valuable carbonyl compounds from unsaturated hydrocarbon precursors. Traditional mercury(II) catalysts hydrate terminal alkynes with Markovnikov selectivity to methyl ketones. Much research has been devoted to finding catalysts based on less toxic metals, the most promising being gold(I), gold(III), platinum(II), and palladium(II). Catalytic anti-Markovnikov hydration of terminal alkynes to aldehydes has been realized in an efficient manner with ruthenium(II) complex catalysts. The present review article lists known hydration catalysts and discusses applications of catalytic hydration to different classes of substrates, with an emphasis on functional group tolerance and regioselectivity. 1 Introduction 2 Timeline 3 Alkyne Hydration Catalysts 3.1 Brønsted Acid and Base Catalysts 3.2 Mercury Catalysts 3.3 Non-Mercurial Catalysts for Alkyne Hydration 3.4 Anti-Markovnikov Hydration of Terminal Alkynes 3.5 Enzymatic Hydration of Alkynes 4 Mechanisms of Catalytic Alkyne Hydration 4.1 Brønsted Acid Catalyzed Hydration 4.2 Mercury-Catalyzed Hydration 4.3 Other-Metal-Catalyzed Markovnikov Hydrations 4.4 Mechanism of Ruthenium-Catalyzed Anti-Markovnikov Hydration 5 Substrate Spectrum and Selectivity of Catalytic Alkyne Hydration­ 5.1 Markovnikov Hydration Catalysis 5.2 Anti-Markovnikov Hydration Catalysts 6 Reactions Related to Catalytic Alkyne Hydration 7 Conclusions and Outlook