Ethyl 4-hydroxybenzoate is treated with a large excess of $\mathrm{CH}{}_3\mathrm{MgBr}$ in dry ether: (i) $\mathrm{CH}{}_3\mathrm{MgBr}$ (excess), dry ether; (ii) $\mathrm{H}{}_3\mathrm{O}{}^{+}$. The final product is

The phenolic OH consumes one equivalent of Grignard (giving methane and the phenoxide). The ester then adds two equivalents to give the tertiary alkoxide; the ketone stage is too reactive to stop. Acidic work-up gives the diol 4-(2-hydroxypropan-2-yl)phenol.