1: ethyl 8-hydroxy-1,4-dioxaspiro[4.5]dec-7-ene-7-carboxylate With N,N,N',N',N'',N''-hexamethylphosphoric triamide; tert.-butyl lithium; sodium hydride in tetrahydrofuran; pentane T=-78°C; 0.166667 h; 2: methyl iodide in tetrahydrofuran; pentane T=-78 - 25°C; 5 h; 3: With potassium hydroxide in ethanol 8 h; Heating;

1: 1.) NaH / 1.) ether, reflux, 2 h, 2.) ether, RT, overnight 2: 1.) copper(I) iodide, LiBr / 1.) ether, 0 deg C, 15 min, 2.) ether, -10 deg C, 12 h View Scheme