1: acetylenecarboxylic acid With lithium hydride in tetrahydrofuran T=20°C; Metallation; 18 h; 2: chloroformic acid ethyl ester in tetrahydrofuran T=-10 - 20°C; Acylation; 3: sodium 2,4,6-trimethylphenoxide in tetrahydrofuran T=20 - 45°C; Substitution;

in ethanol

in toluene 2 h; Heating;

1: 49 percent / toluene / 2 h / Heating 2: 36 percent / benzene / 70 h / 20 °C / Irradiation View Scheme