1: 99 percent / NaH / tetrahydrofuran; paraffin / 1.) 0 deg C, 10 min; 0 to 25 deg C, 10 min, 2.) reflux, 2 h 2: 85 percent / p-TsOH, molecular sieves 4 Angstroem / toluene / 4 h / Heating 3: 48 percent / n-BuLi / tetrahydrofuran; hexane / 1.) 0 deg C, 10 min, 2.) reflux, 3 h View Scheme

<b>Multi-step reaction with 2 steps<br /> </b>1: 77 percent / LDA / hexane; tetrahydrofuran / 1.) -78 to 0 deg C, 45 min; 25 deg C, 3 h, 2.) -78 deg C, 5 min; -78 to 0 deg C<br />2: 98 percent / Br₂ / CH₂Cl₂; CCl₄ / 3 h / 25 &deg;C<br /> <br /> &nbsp;

<b>Multi-step reaction with 2 steps<br /> </b>1: 77 percent / LDA / hexane; tetrahydrofuran / 1.) -78 to 0 deg C, 45 min; 25 deg C, 3 h, 2.) -78 deg C, 5 min; -78 to 0 deg C<br />2: 98 percent / Br₂ / CH₂Cl₂; CCl₄ / 3 h / 25 &deg;C<br /> <br /> &nbsp;

<b>Multi-step reaction with 3 steps<br /> </b>2: 77 percent / LDA / hexane; tetrahydrofuran / 1.) -78 to 0 deg C, 45 min; 25 deg C, 3 h, 2.) -78 deg C, 5 min; -78 to 0 deg C<br />3: 98 percent / Br₂ / CH₂Cl₂; CCl₄ / 3 h / 25 &deg;C<br /> <br /> &nbsp;