1: c-H2SO4 2: DIBAL / diethyl ether 3: benzene / Ambient temperature View Scheme

1: (COCl)2; DMF / CH2Cl2 / 1.5 h / 20 °C 2: -78 °C View Scheme

sulfuric acid

1: 5-(2,6,6-trimethyl-cyclohex-1-enyl)-3-methyl-1-phenyl-sulphonyl-penta-2,4-diene With potassium tert-butylate in tetrahydrofuran T=-20°C; 0.5 h; 2: (E)-4-bromo-3-methyl-2-butenoic acid in tetrahydrofuran T=-20 - 60°C; Julia olefination; 4 h;