1: hex-1-yne With n-butyllithium in tetrahydrofuran; hexane T=-78°C; 0.5 h; 2: 3-triisopropyl-α,β-acetylenic aldehyde in tetrahydrofuran; hexane T=-78 - 20°C;

1.1: PCC; molecular sieves 4 Angstroem; celite / CH2Cl2 / 20 °C 2.1: triphenylphosphine / CH2Cl2 / 5 h / 20 °C 2.2: 786 mg / CH2Cl2 / 2 h View Scheme