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

1,1-Dimethyl-3-(phenyldio)-propane 4 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 7. These were cyclised without purification upon acidic conditions to give the cyclopentannulation products 9. A similar result was obtained with the corresponding orthoester reagent 6. This cyclopentannulation sequence is applicable to a wide variety of enones except for those bearing substituents near the reacting centre. (C) 2002 Published by Elsevier Science Ltd.