1.1: 78 percent / 1,2-dimethoxy-ethane / 60 h / 50 °C 2.1: tetrabutylammonium bromide; KOH / tetrahydrofuran / 0.5 h / 0 °C 2.2: 98 percent / tetrahydrofuran / 5 h / 20 °C 3.1: 90 percent / HCl / toluene / 1.5 h / 0 - 20 °C View Scheme

in ethylene glycol dimethyl ether T=50°C; 60 h;