Highly organic phase soluble polyisobutylene-bound cobalt phthalocyanines as recyclable catalysts for nitroarene reduction

Abstract

A cobalt phthalocyanine (CoMPc) containing covalently linked polyisobutylene (PIB) groups as phase anchors that is both highly soluble in nonpolar organic solvents and phase selectively soluble in a liquid/liquid separation step is shown to be an effective recyclable homogeneous catalyst for nitroarene reduction in a semi-thermomorphic system. Electron-donating and electron-withdrawing substituents in the nitroarene are tolerated in this aniline synthesis and the catalyst is recyclable up to 10 cycles with little leaching and no detectable loss in reactivity after 10 cycles.

Recyclable Polyisobutylene‐Bound HMPA as an Organocatalyst in Recyclable Poly(α‐olefin) Solvents

“…Our prior work has also shown that PIB‐bound species are even more phase selectively soluble in PAOs than heptane in liquid/liquid separations involving polar organic phases [5,6] . This prior work has also shown that terminally functionalized PIB‐bound catalysts or reagents in the same solvents as their low molecular weight analogs have equivalent reactivity [5,9–14,16–20] . However, when PIB is used in an alkane, reactivities are less predictable because alkanes have not historically been studied as solvents for reactions of polar catalysts.…”

“…Our prior work has shown that vinyl-terminated PIB is broadly useful as a precursor for formation of recyclable ligands, catalysts, and reagents that can be easily separated from products. [8][9][10][11][12][13][14] Such separations are effective because terminally functionalized PIB oligomers have excellent phase selective solubility in nonpolar alkanes versus polar solvents like acetonitrile (MeCN), MeOH and water. They are also highly soluble in poly(α-olefin)s (PAOs) like PAO 432 , the fully saturated trimer formed from trimerization of 1-decene.…”

“…[5,6] This prior work has also shown that terminally functionalized PIB-bound catalysts or reagents in the same solvents as their low molecular weight analogs have equivalent reactivity. [5,[9][10][11][12][13][14][16][17][18][19][20] However, when PIB is used in an alkane, reactivities are less predictable because alkanes have not historically been studied as solvents for reactions of polar catalysts. Indeed, prior studies have shown that switching from a solvent like THF or CH 2 Cl 2 to an alkane like heptane or its recyclable analog PAO can lead to higher, different, equivalent or no reactivity for a recyclable PIB-bound catalyst in a pure alkane because of the minimal ability of alkanes to solvate reactants, transition states, or products.…”

Recyclable soluble polyisobutylene-bound oxidizing agents

“…Several groups have shown that this alkene-terminated polyisobutylene (PIB) can be modified and used as a polymer support for precious catalysts such as Hoveyda-Grubbs catalysts, 1 polyoxometalates, 2 photoredox catalysts, 3,4 and cross-coupling catalysts. 5 This highly soluble support makes otherwise insoluble catalysts soluble, 6 and allows catalytic reactions using PIB supported catalysts to be conducted under homogeneous conditions. These supports also facilitate the isolation and recovery of catalysts by simple phase separation in liquid/liquid biphasic separations after a reaction using heptane and a polar solvent since it is heptane soluble while most polar products are not heptane soluble.…”

Block copolymers derived from polyisobutylene oligomers

“…These materials’ phase selective solubility in alkane solvents like heptane and poly(α‐olefin)s (PAOs) makes these oligomeric hydrocarbon derivatives excellent phase anchors for immobilization of ligands and catalysts . Such functional polyisobutylene derivatives are also useful in that they make otherwise insoluble materials like phthallocyanines, inorganic clusters, and nanoparticles soluble in alkane solvents and in polyolefins . Here, we explore chemistry to modify the properties of PIB exploring possible routes to block copolymers using the functional groups of commercially available alkene‐terminated PIB oligomers as handles to couple polar monomers to these preexisting PIB oligomers.…”