Lithiated benzothiophenes and benzofurans require 2-silyl protection to avoid anion migration

2-Trimethylsilyl protection of benzothiophenes and benzofurans prevents anion migration to the 2-position when lithiated species are formed. These lithiated benzothiophenes and benzofurans provide superior results in additions to piperidones. Deprotection is conveniently achieved under acidic conditions. Direct C-7 metalation of benzothiophene is enabled by 2-triisopropylsilyl protection at C-2.