Identify the reagent R in the following reaction:

Step-by-step solution

The given reaction involves the introduction of a formyl group ( -CHO ) at the -position of cyclohexanone. This is a crossed Claisen condensation reaction. First, the base sodium ethoxide ( C ₂ H ₅ ONa ) abstracts an -hydrogen from cyclohexanone to generate a nucleophilic enolate ion. To introduce a formyl group, this enolate must react with a formate ester. When the enolate attacks ethyl formate ( HCOOC ₂ H ₅ ), it undergoes nucleophilic acyl substitution. The ethoxide ion acts as a leaving group, resulting in the