Ireland-Claisen rearrangement of secondary allyl acetate revisited: inevitable C-silylation circumvented by one-pot application of excessive LDA/TMSCl and TBAF

Yield lowering C-silylation was found to be inevitable in all the six tested examples of stoichiometric LDA/TMSCl promoted Ireland-Claisen rearrangement of secondary allyl acetates. In order to circumvent this problem, a higher yielding protocol was devised after the isolated by-products were found to be excellent substrates for further rearrangement. Thus, excessive LDA/TMSCl was applied to achieve complete 3,3′-sigmatropic shift of the substrates, and the resulting mixtures of normal and α-silylated γ,δ-unsaturated carboxylic acids was then desilylated by one-pot application of TBAF.