New catalytic activity of polymer supported quaternary onium salts regioselective addition reaction of oxiranes with active esters catalyzed by insoluble polystyrene bound quaternary ammonium and phosphonium salts
Nishikubo, T.; IIzawa, T.; Shimojo, M.; Kato, T.; Shiina, A.
Journal of Organic Chemistry 55(8): 2536-2542
ISSN/ISBN: 0022-3263 DOI: 10.1021/jo00295a055
A new regioselective addiction reaction of oxiranes 15-17 with active esters 18 and 19 was carried out to give the adducts 20a-f using quaternary onium salts on cross-linked polystyrene beads. The catalytic activity of the polystyrene beads was evaluated from rates of the reaction and yields of reaction products. In this reaction, the beads containing pendant benzyltripropyl- or benzyltributylphosphonium chlorides showed the highest catalytic activity among the polymeric catalysts. The beads containing pendant quaternary phosphonium salts also had higher catalytic activity than the beads containing pendant quaternary ammonium salts and the corresponding low molecular weight benzyltrialkylphosphonium salts. Furthermore, it was found from detailed kinetic studies that the rate of addition reaction of oxirane with active ester using polymer-supported quaternary onium salt as a catalyst was proportional to the initial catalyst concentration [C]0 and the oxirane concentration [O], and was not dependent on the active ester concentration as follows: d[P]/dt = k2[C]0[O], where [P] is the product concentration, and k2 is the second-order rate constant. Given these kinetic results, the reaction mechanism of oxirane with active ester catalyzed by the polymer-supported quaternary onium salts is also assumed.