Efficient hydroalkoxylation of alkenes to generate octane-boosting ethers using recyclable metal triflates and highly active metal triflate/Brønsted acid-assisted catalysts

gem-Disubstituted alkenes are directly and readily etherified with alcohols using Al(OTf)3 and Zr(OTf)4 as recyclable Lewis acid catalysts. In contrast, primary or secondary alkene analogues were inert under these conditions, enabling excellent chemoselectivity. Lanthanide triflates are inactive as catalysts for such reactions, as is phosphoric acid. But a combination of these two otherwise inactive entities led to an ‘assisted acidity’ scenario that saw significant unmatched catalyst activity. All catalysts of this study are recyclable a number of times without loss of activity.

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► Etherification of alkenes using metal triflates and binary catalyst systems.
► Assisted acidity binary lanthanide metal triflates/H3PO4 are remarkably active.
► Lanthanide metal triflates are inactive as catalysts without the added H3PO4.
► Catalyst recycling of metal triflates and binary lanthanide triflate/H3PO4 systems.
► Assisted acidity catalysts (La(OTf)3/H3PO4) outperform HOTf and all others tested.