Fig. 1. Kinetic traces for the cycloadditions between 2-furoic acid 1a and maleimide 2a (1 : 1 ratio at 0.5 M) in water (top), with the addition of 1 equiv. NaOH (bottom); see ESI† for details; cf. Tables 2 and 3: reactions run at 1 : 1.5 ratio 1 : 2 and 1 M concentration.