Multi-step reaction with 3 steps 1.1: 98 percent / n-butyllithium; chlorodiethylaluminum / hexane; tetrahydrofuran / 1 h / -20 °C2.1: n-butyllithium; i-Pr2NH / hexane; tetrahydrofuran / 5 h / -50 °C2.2: 85 percent / hexane; tetrahydrofuran / 2 h / -50 °C3.1: 1,8-diazabicyclo[5.4.0]undecene / dimethylsulfoxide / 3 h / 70 °C