Heterocycle Synthesis Using Homopropargylic Ethers as Latent Electrophiles

Significance

The completely diastereoselective formation of oxygen-containing heterocycles with pendant ketone functionality is described. The use of the combined metal system PPh₃AuCl/AgSbF₆ is found to be more reactive than a NaAuCl₄ catalyst. The silver’s role in the former system is to abstract the chloride ion, generating a more electrophilic Au center. Interestingly, the reaction is conducted in water-saturated dichloromethane where the water hydrates the alkyne, generating the ketone seen in the final product. The reaction shows good functional-group compatibility, with esters, alkoxy and hydroxy groups showing no ­inhibition or erosion of yield and selectivity.