Compound A is treated with a large excess of CH ₃ MgBr . The resulting product is then exposed to POCl ₃ in pyridine to give compound B (shown below) as one of the products. Which of the following compounds is A?

Step-by-step solution

Compound B has three exocyclic double bonds on a cyclohexane ring: one =CH₂ group and two =C(CH₃)₂ groups. These double bonds are formed by the dehydration of tertiary alcohols using POCl₃ in pyridine. The exocyclic =CH₂ group is formed from a cyclic tertiary alcohol containing a methyl group, which is produced by the nucleophilic addition of CH₃MgBr to a cyclic ketone. The exocyclic =C(CH₃)₂ groups are formed from -C(OH)(CH₃)₂ groups. These tertiary alcohols are produced by the reaction of CH₃MgBr with a methyl ke