1: 5-trimethylsilyl-4-pentynyl-1-bromide With magnesium in diethyl ether T=20°C; 2: 4-hydroxybutyraldehyde tert-butyldimethylsilyl ether in diethyl ether T=20°C; Grignard reaction;

1: 94 percent / (COCl)2; DMSO; triethylamine / tetrahydrofuran / -78 °C 2: 78 percent / tetrahydrofuran / -40 °C 3: 49 percent / tetrabutylammonium fluoride / tetrahydrofuran / 20 °C View Scheme

1: 94 percent / (COCl)2; DMSO; triethylamine / tetrahydrofuran / -78 °C 2: 78 percent / tetrahydrofuran / -40 °C 3: 49 percent / tetrabutylammonium fluoride / tetrahydrofuran / 20 °C 4: 73 percent / pyridinium chlorochromate / CH2Cl2 / 20 °C View Scheme

1: 94 percent / (COCl)2; DMSO; triethylamine / tetrahydrofuran / -78 °C 2: 78 percent / tetrahydrofuran / -40 °C 3: 49 percent / tetrabutylammonium fluoride / tetrahydrofuran / 20 °C 4: 88 percent / imidazole / CH2Cl2 / 20 °C View Scheme

oxalyl dichloride; dimethyl sulfoxide; triethylamine in tetrahydrofuran T=-78°C; Swern oxidation;