New evidence on the regiochemistry of the tert-butyldiphenylsilylcupration of allene using the silylcuprate or silylcopper reagent

The regiochemistry in the tert-butyldiphenylsilylcupration of the allene depends on the temperature and also on the nature of the electrophile. Thus, the intermediate generated by addition of the silylcuprate at −78°C reacted with electrophiles to give allylsilanes, except with oxo compounds which afforded vinylsilanes. On the other hand, the silylcopper reagent was added at −40°C leading, in all cases, to the corresponding allylsilanes. When enones were used as electrophile the vinylsilanes were the 1,2-addition products and the allylsilanes those from 1,4-addition. These functionalized vinyl or allyl tert-butyldiphenylsilanes are interesting synthons for the preparation of conjugated tert-butyldiphenylsilyltrienes and functionalized exocyclic alkylidenecyclopentenes.