A silver(I)-catalyzed intramolecular addition reaction of silyl enol ethers to alkynes was developed. Alkynyl silyl enol ethers were treated in a one-pot reaction with AgNTf _2, directly followed by addition of N-iodosuccinimide (NIS) in ClCH _2CH _2Cl, which provided exclusively the E-alkenyl iodide derivatives in good yields. Although the silver-catalyzed cycloisomerization of bicycloalkanone proved to be difficult, iodo-demetalation makes it possible to obtain alkenyl iodide derivative. The X-ray crystal structure of tricyclic alkenyl iodide showed an E-configured exo double bond, thus, providing evidence for the iodo-demetalation of intermediate C with the NIS reagent. In light of this result, we considered the possibility that a similar silver-catalyzed pathway could account for activated alkynes. The reaction allows the diastereoselective synthesis of a variety of spiro compounds.
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