= Solution
The nonnucleophilic magnesium <amide> metalates the triazole carbon \b[between the two ring nitrogen atoms], conventionally C5 of 1-propyl-1,2,4-triazole. That <proton> is more readily removed because the resulting heteroaryl anion is stabilized by the neighboring nitrogen atoms; the reagent therefore acts as a base rather than adding a tetramethylpiperidinyl group.
The heteroaryl organomagnesium intermediate attacks the allylic bromide, forming a new C–C bond. The product is \b[5-(cyclohex-2-en-1-yl)-1-propyl-1,2,4-triazole]. Ordinary allylic substitution and an $S_\mathrm N2'$ description give the same unlabelled cyclohexenyl connectivity for this unsubstituted allylic ring, so the structural assignment does not distinguish those trajectories.
The <molecular formula> checks the assignment: N-propyltriazole is $\mathrm{C_5H_9N_3}$; replacing a ring H by $\mathrm{C_6H_9}$ gives \b[$\mathrm{C_{11}H_{17}N_3}$], as printed.
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