Use of MeNO2–LiClO4 in promoting a 1,2-shift in RSCI electrophilic addition to 3,3-dimethylbut-1-ene: reaction course and stereochemistry

In the Ad_E reaction of RSC1 with 3,3-dimethylbut-l-ene the system MeNO₂–LiClO₄ serves as an efficient promoter of a 1,2-shift which occurs either simultaneously with the electrophilic addition step (π-route) or as a rearrangement of the initially-formed 1,2-adducts (σ-route) and proceeds in a highly stereoselective fashion.