Synthesis and characterization of asymmetric substituted dicarbamates

Several new asymmetric substituted dicarbamates were synthesized with a convenient route. Firstly, tolylene-2, 4-diisocyanate dimmer was obtained from monomer with tributylphosphine as catalyst. Then, the dimmer reacted with alcohol (R1OH) to prepare carbamate substituted uretidione. Finally, uretidione ring was opened and the released isocyanate reacted with another alcohol (R2OH, R1 ≠ R2).