Which of the following compounds is the appropriate starting material for the reaction sequence given below? (i) Ph ₃ P , then n -BuLi (ii) Cyclohexanone (iii) CH ₂ I ₂, Zn - Cu

Step-by-step solution

The first step of the reaction sequence uses Ph ₃ P followed by n -BuLi, which are the standard reagents for preparing a Wittig reagent (phosphonium ylide). The formation of a phosphonium salt requires an alkyl halide to react with Ph ₃ P . Among the given choices, only bromocyclohexane is an alkyl halide. Bromocyclohexane reacts with Ph ₃ P to form cyclohexyltriphenylphosphonium bromide, which is then deprotonated by n -BuLi to generate the ylide. The ylide reacts with cyclohexanone in the second step to form cycl