Paragraph: Treatment of compound O with KMnO_ 4 / H^ + gave P ,...

Paragraph: Treatment of compound $\mathbf{O}$ with $\mathrm{KMnO}_{4} / \mathrm{H}^{+}$gave $\mathbf{P}$, which on heating with ammonia gave $\mathbf{Q}$. The compound $\mathbf{Q}$ on treatment with $\mathrm{Br}_{2} / \mathrm{NaOH}$ produced $\mathbf{R}$. On strong heating, $\mathbf{Q}$ gave $\mathbf{S}$, which on further treatment with ethyl $2-$bromopropanoate in the presence of $\mathrm{KOH}$ followed by acidification, gave a compound $\mathbf{T}$.

Question: The compound $\mathbf{R}$ is