in tetrahydrofuran; hexane T=0 - 20°C; 2 h;

1: Methyltriphenylphosphonium bromide With sodium amide in tetrahydrofuran 1 h; Heating; 2: (2E,4Z)-2,4-heptadienal in tetrahydrofuran T=-10 - 0°C; Wittig reaction; 1 h; Further stages.;

manganese(IV) oxide in Petroleum ether 1 h;

1: alumina / benzene / 5 h / Heating; other β-allenic methyl and ethyl esters 2: LiAlH4 / diethyl ether / 1.5 h / -40 °C 3: 87 percent / MnO2 / petroleum ether / 1 h View Scheme

1: 67 percent / propionic acid / 130 - 150 °C 2: alumina / benzene / 5 h / Heating; other β-allenic methyl and ethyl esters 3: LiAlH4 / diethyl ether / 1.5 h / -40 °C 4: 87 percent / MnO2 / petroleum ether / 1 h View Scheme

1: LiAlH4 / diethyl ether / 1.5 h / -40 °C 2: 87 percent / MnO2 / petroleum ether / 1 h View Scheme

cobalt(II) 2,4-pentanedionate; lithium bromide in tetrahydrofuran; 1-methyl-pyrrolidin-2-one T=-30 - 0°C; 0.5 h;

1: With manganese(IV) oxide; benzoic acid in dichloromethane T=20°C; 72 h; 2: With lithium aluminium tetrahydride in diethyl ether T=0°C; 1 h; 3: With manganese(IV) oxide in dichloromethane T=20°C; 78 h; Title compound not separated from byproducts;

1: 1.) NaH / 1.) THF, 30 min, 2.) THF, 2 h 2: 1.) (COCl)2, DMSO, 2.) Et3N / 1.) CH2Cl2, -78 deg C, 2 h, 2.) 2.) CH2Cl2, from -78 deg C to RT, 75 min 3: 78 percent / LiBH4 / tetrahydrofuran / 0.5 h / 20 °C 4: 86 percent / LiCl, MsCl, s-collidine / dimethylformamide / 2 h / 0 - 20 °C 5: 79 percent / tetrahydrofuran / 12 h / Ambient temperature 6: 91 percent / tetra-n-butylammonium fluoride / tetrahydrofuran / 3 h / 20 °C 7: 73 percent / TPAP, NMO, 4 Angstroem sieves / CH2Cl2 / 3 h View Scheme

1: 79 percent / tetrahydrofuran / 12 h / Ambient temperature 2: 91 percent / tetra-n-butylammonium fluoride / tetrahydrofuran / 3 h / 20 °C 3: 73 percent / TPAP, NMO, 4 Angstroem sieves / CH2Cl2 / 3 h View Scheme