1: [dimethyl(phenyl)silyl]acetylene With n-butyllithium in tetrahydrofuran; hexane T=0°C; 0.25 h; 2: N,O-dimethylacetohydroxamic acid in tetrahydrofuran; hexane T=-78 - 20°C; 2.5 h; Further stages.;

aluminium trichloride in dichloromethane T=-20°C;

1: 70 percent / MeLi / diethyl ether; tetrahydrofuran / 0.25 h / 0 °C 2: 81 percent / TsOH / methanol / 12 h 3: 78 percent / CrO3; aq. H2SO4 / acetone / -20 - 22 °C View Scheme

1: 81 percent / TsOH / methanol / 12 h 2: 78 percent / CrO3; aq. H2SO4 / acetone / -20 - 22 °C View Scheme