Direct Preparation of Rotaxane from Aminoalcohol: Selective<i>O</i>-Acylation of Aminoalcohol in the Presence of Trifluoromethanesulfonic Acid and Crown Ether
Selective O-acylation of aminoalcohols by a bulky acid anhydride in the presence of trifluoromethanesulfonic acid and dibenzo-24-crown-8 afforded [2]rotaxane in high yields. An acid halide could be used as an acylating reagent in the presence of silver trifluoromethanesulfonate.
Side chain polyrotaxanes were synthesized from radically polymerizable pseudorotaxane monomers (DB24C8·1) which were composed of secondary ammonium salts having (meth)acryl group at one end and bulky stopper at the other end (1a and 1b) and dibenzo-24-crown-8 (DB24C8). Both radical polymerization of DB24C8·1 and copolymerization of DB24C8·1a with styrene afforded corresponding polymers having rotaxane moieties in the side chains (2a, 2b, and 3).