Question #44478

Consider the following multistep synthesis starting from Compound \textbf{X} (Methyl 7-((tetrahydro-2H-pyran-2-yl)oxy)hept-4-ynoate):

$\text{Compound \textbf{X}} \xrightarrow[2. \text{ Cat. } p\text{-TsOH, MeOH, } 25^\circ\text{C}]{1. \text{ Na, NH}_3(l), -78^\circ\text{C}} \textbf{Y}$

$\textbf{Y} \xrightarrow{PBr_3, \text{ pyridine, } 0^\circ\text{C}} \textbf{Z}$

$\textbf{Z} \xrightarrow[2. \text{ Excess } D_2O]{1. \text{ Rieke Mg, THF, } -78^\circ\text{C, high dilution}} \textbf{Major Product (P)}$

Identify the major product \textbf{P}.