1: With n-butyllithium in tetrahydrofuran; hexane T=-70°C; Metallation; 0.5 h; 2: With tri-isopropoxy-borane in tetrahydrofuran; hexane T=-70 - 20°C; Substitution; 3: With sulfuric acid in water T=0°C; Hydrolysis; 0.5 h;

1.1: Zn-Cu; POCl3 / diethyl ether / 4 h / 20 °C / Heating 2.1: Zn; AcOH / 2.5 h / 20 - 120 °C 3.1: 82.5 percent / p-TsOH / benzene / 20 h / 120 °C 4.1: BuLi / hexane; tetrahydrofuran / 0.5 h / -70 °C 4.2: B(OiPr)3 / tetrahydrofuran; hexane / -70 - 20 °C 4.3: 83 percent / H2SO4 / H2O / 0.5 h / 0 °C View Scheme

1.1: 82.5 percent / p-TsOH / benzene / 20 h / 120 °C 2.1: BuLi / hexane; tetrahydrofuran / 0.5 h / -70 °C 2.2: B(OiPr)3 / tetrahydrofuran; hexane / -70 - 20 °C 2.3: 83 percent / H2SO4 / H2O / 0.5 h / 0 °C View Scheme

1.1: Zn; AcOH / 2.5 h / 20 - 120 °C 2.1: 82.5 percent / p-TsOH / benzene / 20 h / 120 °C 3.1: BuLi / hexane; tetrahydrofuran / 0.5 h / -70 °C 3.2: B(OiPr)3 / tetrahydrofuran; hexane / -70 - 20 °C 3.3: 83 percent / H2SO4 / H2O / 0.5 h / 0 °C View Scheme

hydrogenchloride in methanol T=20°C; Ring cleavage;