Chemistry Question from JEE Main 2024 · 1 February, Shift 1

Identify the reagents $A$, $B$ and $C$ used for the following conversion:

The starting material is a cyclohexane ring carrying a $-\text{CH}_2\text{COOCH}_3$ group at C-$1$, a $-\text{CH}_2\text{CHO}$ group at the adjacent C-$2$, and an $-\text{OH}$ group at C-$4$ — that is, methyl $2$-[$4$-hydroxy-$2$-($2$-oxoethyl)cyclohexyl]acetate. It is taken through three steps:

• $P_1$: the same ring, now carrying $-\text{CH}_2\text{CHO}$ at both C-$1$ and C-$2$, with the C-$4$ $-\text{OH}$ untouched.
• $P_2$: a bicyclic hydrindane — the two side chains have joined to close a five-membered ring fused to the cyclohexane — in which the new five-membered ring carries a $\text{C}=\text{C}$ bearing a $-\text{CHO}$ group; the ring $-\text{OH}$ is still present.
• $P_3$: the same bicyclic skeleton, with that $-\text{CHO}$ group replaced by $-\text{CH}_3$.