Catalytic isomerization of allyl functionalities in water by hexaaquaruthenium(II) tosylate

• A Ru(II) coordination compound that catalytically unmasks allyl ethers and esters.
• The deprotection chemistry takes place in 100% water.
• Catalysis requires no additives or exclusion of air and takes place in water.
• Deprotection on a variety of substrates makes it a useful reagent in synthesis.
• Reaction is an olefin isomerization to a vinyl ether that undergoes hydrolysis.

The water-soluble coordination compound hexaaquaruthenium(II) p-toluene sulfonate (1) catalyzes olefin isomerization that makes it a useful catalyst in unmasking allyl ether and ester protecting groups in water. Allyl ethers of alcohols and acetic acid allyl ester are readily converted to the corresponding alcohols and acid in a catalytic fashion with compound 1 in water (50 °C). A mechanistic investigation on ethylene glycol monoallyl ether reveals the intermediate vinyl ether resulting from olefn isomerization (ΔH‡ = 19.0 (±0.4) kcal/mol). This is followed by hydrolysis to the final ethylene glycol that is promoted by 1. This “one-pot” reaction provides a new useful coordination compound as a deprotection reagent in synthetic organic chemistry.

Catalytic unmasking reaction. Benign aerobic conditions. Absence of additives or cosolvent.Figure optionsDownload as PowerPoint slide