The Kinetic Solvent Effect on 1,3-Dipolar Cycloaddition of 2,2,5,5-Tetramethyl-3-imidazoline-3-oxide-1-oxyl

The use of 2,2,5,5-tetramethyl-3-imidazoline-3-oxide-1-oxyl (1) as a controlling agent in Nitroxide Mediated Polymerization allows for activation of alkoxyamine homolysis by 1,3-dipolar cycloaddition of a vinyl monomer [Edeleva et al. Chem. Commun. 2019, 55, 190-193]. Polymerization can be carried out in a medium with different polarity and hydrogen bonding capacity which affects the rate of 1,3-dipolar cycloaddition reaction. In the present study, the solvent effect on the rate of this reaction was investigated by the electron paramagnetic resonance and density functional theory for the six different dipolarophiles, e.g. styrene, n-butyl acrylate, acrylonitrile, methyl vinyl ketone, maleic anhydride, and N-phenyl maleimide. The rate of 1,3 dipolar cycloaddition of non-polar styrene was found to be slightly dependent on solvent, while one order of magnitude decrease in rate coefficient is observed for other dipolarophiles when going from hexane to methanol.