Recyclable polyisobutylene-supported pyridyl N-oxide allylation catalysts

Polyisobutylene (PIB) is a useful soluble polymer support that facilitates catalyst recovery and recycling in liquid–liquid biphasic systems because the long polyisobutylene chain confers high phase selective solubility in the nonpolar phase of polar–nonpolar liquid–liquid biphasic systems on groups attached to the polymer’s terminus. This work shows that PIB-supports that are effective with metal catalysts can also facilitate synthesis and use of organocatalysts. This is demonstrated by the use of a PIB-supported pyridyl N-oxide to promote the allylation of several aromatic aldehydes with allyltrichlorosilane. These studies show that a PIB-supported pyridyl N-oxide is a very active recyclable catalyst that promotes the allylation of aromatic aldehydes in yields of up to 99% yield. These PIB-supported pyridyl N-oxide catalysts were recovered in the hexane phase of a hexane/90% EtOH–H2O solvent system and were successfully recycled through 5 cycles with little effect on catalyst efficiency.