A highly selective Bi(OTf)3 mediated fragmentation-contraction of δ-ortholactones. A facile route to functionalized γ-lactones

Add time:07/22/2019    Source:sciencedirect.com

A very selective method for the formation of γ-lactones from pyranyl ortholactones has been developed which occurs via a fragmentation-acetate migration-ring contraction process. The reaction is very functional group tolerant, providing functionalized γ-lactones as a single isomeric product following the ring contraction. Mechanistic studies indicate the reaction is mediated by triflic acid liberated from Bi(OTf)3 in a slow and controlled manner providing excellent chemo and regioselectivity. We propose the triflic acid acts as both a proton and a nucleophile source with triflate anion mediating the fragmentation process.

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