1: mono-methyl malonate potassium salt With magnesium chloride in tetrahydrofuran T=50°C; 4 h; 2: 4-Pentynoic acid With 1,1'-carbonyldiimidazole in tetrahydrofuran T=5 - 20°C; 1 h;

n-butyllithium; sodium hydride in tetrahydrofuran; hexane; toluene 1.) 0 deg C, 15 min, 2.) -78 deg, 15 min;

1: DCC, 4-(N,N-dimethylamino)pyridine / CH2Cl2 / 24 h / Ambient temperature 2: Heating View Scheme

Heating; Yield given;