Cyclopentannulation of enones with organocuprate reagents containing an acetal or an orthoester function

1,1-Dimethyl-3-(phenylthio)-propane was deprotonated with t-BuLi, then converted to the corresponding organocuprate reagent which, in the presence of HMPA and TMSCl, was added to a variety of enones to give the corresponding silylenol ethers . These were cyclised without purification upon acidic conditions to give the cyclopentannulation products . A similar result was obtained with the corresponding orthoester reagent . This cyclopentannulation sequence is applicable to a wide variety of enones except for those bearing substituents near the reacting centre.