The condensation of 2-phenylethylhydrazine (I) with propargyl bromide (II) by means of K2CO3 in aqueous acetonitrile gives the target hydrazine.

The condensation of fully Boc-protected 2-phenylethylhydrazine (I) with propargyl bromide (II) by means of NaH gives the protected disubstituted hydrazine (III), which is finally deprotected with 4N HCl in dioxane to afford the target hydrazine.