Copper-Promoted Coupling of Vinyl Boronates and Alcohols: A Mild Synthesis of Allyl Vinyl Ethers

摘要

The vinyl ether is a deceptive functional group, as its simple structurenbelies the challenges inherent in its synthesis.1 Because direct O-alkylationnof enolates is not generally viable and vinylation of alcohols is limited tonspecial cases, several types of indirect methods have been developed,nincluding acid- or metal-catalyzed vinyl ether exchange;2 additionelimination on vinyl sulfoxides;3 haloetherification followed by basenelimination;4 selenenyl etherification/selenoxide elimination;5 catalyzednaddition of alcohols to alkynes;6 carbonyl alkenylation with phosphoniumnylides, silyl anions, sulfone anions, or Tebbe reagents;7 base- or metalcatalyzednisomerization;8 and modification of existing vinyl ethers.9nHowever, examination of the details of these processes reveals seriousnlimitations, such as the need for strong bases, strong acids, toxic metals,nor reactive electrophiles; limited substrate substitution; and lack of controlnover alkene stereochemistry.