Oxidative dimerization of anilines with heterogeneous sulfonic acid catalysts

Abstract

Sulfonic acids selectively catalyze the oxidative dimerization of anilines to azobenzenes without any unnecessary organics.

Oxidative Dearomatization of Phenols and Polycyclic Aromatics with Hydrogen Peroxide Triggered by Heterogeneous Sulfonic Acids

“…In analogy with previous oxidation methods developed by our group, [31][32] the best results in present dearomatizations were observed using heterogeneous polymeric sulfonic acids derived from Aquivion. The latter is a commercial polymer characterized by a perfluorinated backbone featuring sidechains that are decorated by sulfonic functions.…”

“…We then tried to tune the reactivity of perfluorinated polymers with sulfonic acid functions by supporting them onto silica. In particular, two materials in which Aquivion and Nafion decorate silica nanoparticles [31][32] were tested (entries 8-9). Although the overall yield of 2 a was disappointing in both cases (10 % and 22 %, respectively), the desired quinone formed selectively.…”

“…Taken together, these results strongly suggest that the dearomatization process occur through a radical mechanism, in analogy with related oxidations triggered by heterogeneous sulfonic acid previously developed by our group. [30][31][32] Finally, we attempted the oxidation of 1,4-naphthalene diol (7 a) under our optimized conditions. The starting material was completely consumed in 4 hours, affording 4 a in 90 % yield.…”

“…An analogous approach enabled the development of a method for the synthesis of arylazo derivatives from the corresponding anilines (Scheme 1c). [32] Overall, these approaches showed the potential for the development of simple synthetic methods that are capable to trigger elaborate oxidations under mild conditions. Moreover, these reactions always employ hydrogen peroxide as oxidant.…”

“…This direct, double C−H functionalization is usually limited to a few transition‐metal based complexes. An analogous approach enabled the development of a method for the synthesis of arylazo derivatives from the corresponding anilines (Scheme 1c) [32] . Overall, these approaches showed the potential for the development of simple synthetic methods that are capable to trigger elaborate oxidations under mild conditions.…”