Fig. 1. Equilibrium between cyclized and uncyclized isomers for 3i. The compound crystallizes as the cyclized species, which was characterized by single crystal X-ray diffraction and an ORTEP diagram (thermal ellipsoids = 50%) is shown. Hydrogens in calculated positions, a second chemically equivalent molecule in the asymmetric unit, and CH2Cl2 of crystallization are omitted. The rate constants in DMSO-d6 were found by fitting the concentrations of both isomers versus an internal standard of ferrocene as functions of time by 1H NMR spectroscopy (see the ESI†).
