Identify the major final product of the following reaction.

Step-by-step solution

The reaction involves methyl acetoacetate and diketene in the presence of a strong base (NaH) and heat. 1. Deprotonation: NaH abstracts the most acidic proton from the active methylene group of methyl acetoacetate to form an enolate ion: CH ₃ COCH ₂ COOCH ₃ NaH [ CH ₃ COCHCOOCH ₃]^- 2. Nucleophilic Attack: The enolate acts as a nucleophile and attacks the carbonyl carbon of diketene. This leads to the opening of the four-membered lactone ring, forming a poly- -carbonyl intermediate (an acetoacetyl derivative): CH ₃