After the solvents screening, we explored the effect of temperature on the microdroplet reaction in the range of 25-50 °C (Table , Entries 15-16, and Table ). The experimental results demonstrated the synthesis of vicinal diamine 2a was slightly improved on enhancing the temperature for the microdroplet ring opening reaction. A moderate temperature of 40 °C was considered considering high yield and low energy consumption. Standard reaction conditions: 0.005 mol L -1 imidazoline derivative 1a and 2.3 equiv. H2SO4 were added in 1 mL different solvents; microdroplets were sprayed at 15 μL min -1 by N2 under 101.5 psi at different temperature and were collected in a 25 mL glass beaker for 10 min. a 10% MeCN-DCM was used as the solvent for good dissolvement.