Functionalization of polyisobutylene and polyisobutylene oligomers via the ritter reaction

Abstract

The Ritter reaction, that is, reaction of a carbocation with a nitrile, was carried out on polyisobutylene (PIB) using a variety of reaction conditions. End quenching of PIB carbocations with acrylonitrile under living polymerization conditions (methyl chloride (MeCl)/hexane 60/40 (v/v) solvent mixtures at 270 8C) resulted in either tert-chloride end groups or loss of chain-end fidelity via carbocation rearrangement, as evidenced by NMR spectroscopy. Exo-olefin functionalized PIB substrates were also reacted with nitriles under a variety of reaction conditions including various acid and solvent medium combinations. In all cases, the result was either no reaction or PIB that had undergone severe backbone degradation, as determined via NMR spectroscopy and gel permeation chromatography. Finally, the Ritter reaction was performed on a series of exo-olefin functionalized oligoisobutylenes using acrylonitrile as the nitrile and either 60/40 dichloromethane/hexane or excess acrylonitrile as the solvent. In 60/40 dichloromethane/hexane, significant carbocation rearrangement and/or degradation resulted in a variety of isomeric, acrylamide-functionalized oligomers. In excess acrylonitrile, the desired Ritter reaction was the only reaction observed, resulting in the smooth formation of the terminal acrylamide. The various N-oligoisobutylacrylamides thus obtained represent new hydrophobic monomers useful for the introduction of hydrophobic moieties into acrylamide-based water-soluble polymers.

Recent Applications of Ritter Reactions in Organic Syntheses

“…In 2018, Storey and his colleagues disclosed the reaction of acrylonitrile 14 with polyisobutylene (PIB) oligomers 15 through the classical Ritter reaction to yield acrylamide 16 in the presence of H 2 SO 4 (Scheme 5). [21] In 2019, Khusnutdinov and his co-workers provided the amides 19, 20, through the classical Ritter reaction of propionitrile 17 with norbornene cores 18 using FeCl 3 .6H 2 O as a catalyst. Similar conditions were applied for the preparation of amide 22 and isometric amide 22 through the reaction of propionitrile 17 with exo, exo-tetracyclo [6.2.1.13,6.02,7]dodeca-4,9-diene 21 or endo, trans, exo-pentacyclo [8.2.1.14,7.02,9.03,8] tetradeca-5,11-dienes 23, which the dual bonds are far apart in diene derivatives (Scheme 6).…”

“…In 2018, Storey and his colleagues disclosed the reaction of acrylonitrile 14 with polyisobutylene (PIB) oligomers 15 through the classical Ritter reaction to yield acrylamide 16 in the presence of H 2 SO 4 (Scheme 5). [21] …”

“…Through the addition of water to 6, amides 3 are prepared (Scheme 3). [21] In continuation of our previous work, [22] the recent application of the Ritter reaction in organic synthesis was reviewed through different reagents and conditions.…”

Harnessing Polyisobutylene by Rotaxanation with γ‐Cyclodextrin: Opportunities for Making Smart Molecular Necklaces

“…To overcome such bottlenecks, two synthesis routes are widely used: the making of amphiphilic block copolymers, amphiphilic micelles and vesicles and/or the telechelic modification of the polymer . Indeed, PIBs can be terminally and/or centrally functionalized exhibiting aromatic moieties such as central phenyl group and/or polar moieties such as hydroxyl groups with or without additional terminal phenyl groups, epoxides, carboxyl, bis(imidazole‐1‐carboxylate) esters, secondary or tertiary amine, amide, sulfonated, succinic anhydride, functionalized thymine, or glucopyranoside …”

“…[4] To overcome such bottlenecks, two synthesis routes are widely used: the making of amphiphilic block copolymers, amphiphilic micelles and vesicles [5][6][7][8][9] and/or the telechelic modification of the polymer. [10,11] Indeed, PIBs can be terminally and/or centrally functionalized exhibiting aromatic moieties such as central phenyl group [12][13][14][15][16][17] and/or polar moieties such as hydroxyl groups with [17,18] or without additional terminal phenyl groups, [12,13,18,19] epoxides, [15] carboxyl, [16] bis(imidazole-1-carboxylate) esters, [14] secondary or tertiary amine, [18][19][20] amide, [21] sulfonated, [22] succinic anhydride, [23] functionalized thymine, [18] or glucopyranoside. [13] Nonetheless, a third alternative can be considered by formation of a non-covalent inclusion complex between unmodified PIB and βand more efficiently with γ-cyclodextrin (γ-CD), that is, constituting pseudopolyrotaxanes (PPRs) (Figure 1).…”