Microporous polymeric networks containing a long-term stable auI catalyst for enyne cyclization

Abstract

Two microporous polymer networks having a confined AuI carbene catalyst were obtained and tested for the skeletal rearrangement of enynes. These catalysts were obtained from precursor porous organic polymers (POPs), a type of microporous polymer network, synthesized by the reaction of isatin or a mixture of isatin/trifluoroacetophenone (1:1) with triptycene (POP1 and POP2, respectively) through an electrophilic aromatic substitution, EAS, reaction promoted by trifluoromethanesulfonic acid. These precursors could be easily functionalized through the lactam moiety to form AuI carbene catalysts (POP1-AuCarbene and POP2-AuCarbene). The confined carbenes proved to be very active for the skeletal rearrangement of dimethyl 2-(3-methyl-2-butenyl)-2-propinylmalonate enyne. A large increase in the stability of the AuI catalysts was observed compared to those of most of the homogeneous catalysts described so far in the bibliography. This long-term stability was associated with the separation of AuI atoms, induced by their confinement in the microporous networks. In particular, POP2-AuCarbene exhibited outstanding long-term stability, maintaining catalytic activity even after several months.