N-chloro-succinimide; sodium methylate; dimethylaluminum chloride 1) hexane, CH2Cl2, -78 deg C, 4 h; 2) THF, rt, 16 h; Yield given. Multistep reaction. Yields of byproduct given;

sodium hydride in tetrahydrofuran Carbonylation; 1 h;

triethylamine in toluene T=20°C; Carbonylation; cyclization; 1 h;

triethylamine in tetrahydrofuran Carbonylation; cyclization; 1 h;