Figure 2: Accelerating enolate chemistry with anion–π interactions.

(a) Michael addition of macrocycle 5 to acceptor 7. (b) Comparison of the initial velocity of the formation of Michael adduct 8 (filled circles) with control 9 (from 1, empty circles) implies that anion–π interactions stabilize the anionic transition state 10 by ΔΔG=11.0 kJ mol⁻¹, whereas the reactive enolate intermediate 6 is stabilized by ΔΔG=4.7 kJ mol⁻¹ (see Fig. 1). Conditions: 50 mM 1/5, 50 mM 7, 5 mM DBU, CD₃CN/CDCl₃ 1:1, room temperature; linear curve fit, experiments were performed at least three times. (c) 1,4-Addition of macrocycle 5 to nitroolefin 11 with transition-state stabilization from comparison with malonate 1 (R=H).