Allyl Ethers and Allyloxycarbonyl Derivatives

SPh (a) IPhaPhRbCI (0.05 aqulv) DABCO(1.5 Aqutv) MeOH-HjO (10 1), raflux. 1 h 

Allyl ethers of phenols can be deprotected in a single step by trapping the jc-allyl palladium intermediates with either reducing agents or soft nucleophiles. 

ZnCl2 (0.24 mmol) [PhsPjiPd (0.02 mmol) BusSnH (0.36 mmol) 

For the synthesis of Olivomycin A. the Roush group used a crotyl ether to protect a phenolic hydroxyl group. In the final lap of the synthesis deprotection of the phenolic crotyl ether in 226.1 was achieved with Pd(0) and tributylstan-nane [ heme 4.226]. No harm befeU the sensitive cyclopentylidene acetal and chloroacetate groups. 

Recent methods for the cleavage of allyl ethers that have that have yet to be tested on the anvil of complex target synthesis include (a) diborane generated in sUu by reaction of sodium borohydride with iodine in THF at 0 (cyano, ester, nitro, acetonide and tetrahydropyranyl groups survive) (b) cerium(ni) chloride and sodium iodide in refluxing acetonitrile (benzyl. THP and Boc groups survive) (c) iodotrimethylsilane in acetonitrile at room temperature/ and (d) DDO in wet dichloromethane (secondary allyl ethers, benzyl, acetate and TBS groups survive).  

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