1: cyclobutyl alcohol With n-butyllithium in tetrahydrofuran; hexanes T=0 - 10°C; 2 h; 2: ethylene glycol cyclic sulfate in tetrahydrofuran; hexanes T=15 - 20°C; 3 h; 3: With sulfuric acid; water in tetrahydrofuran; hexanes 18 h;

(i) Mg, (ii) (heating); Multistep reaction;