1.1: 67 percent / tetramethylguanidine / dimethylsulfoxide / 9 h / 25 °C 2.1: tetrahydrofuran / 10.5 h / 0 - 25 °C 2.2: 123 g / ice / tetrahydrofuran / 3 h / 25 °C 3.1: 56 percent / aq. HCl View Scheme

1.1: 67 percent / tetramethylguanidine / dimethylsulfoxide / 9 h / 25 °C 2.1: tetrahydrofuran / 10.5 h / 0 - 25 °C 2.2: 123 g / ice / tetrahydrofuran / 3 h / 25 °C 3.1: 48 percent / aq. NaOH View Scheme