Fig. 1. Time-course of the reaction of 3 with KHMDS followed at −5 °C in THF by in situ infra-red spectroscopy. A: 3 in THF at −5 °C; B: (t = 18 min) KHMDS (2 equiv.) added; C: reaction mixture at −5 °C. D: (t = 108 min): reaction quenched by addition of MeOH.