The controlled homogeneous organic solution polymerization of new hydrophilic cationic exo‐7‐oxanorbornenes via ROMP with RuCl₂(PCy₃)₂CHPh in a novel 2,2,2‐trifluoroethanol/methylenechloride solvent mixture

Abstract

The authors detail herein the synthesis and controlled polymerization of a series of new permanently cationic ammonium exo-7-oxanorbornene derivatives via ROMP, with the first generation Grubbs' catalyst RuCl 2 (PCy 3 ) 2 CHPh, in a novel solvent mixture composed of 1:1 vol/vol 2,2,2-trifluoroethanol (TFE)/methylene chloride. It is demonstrated that this cosolvent mixture is a convenient reaction medium facilitating the polymerization of hydrophilic substrates by hydrophobic initiators under homogeneous conditions. Homopolymerizations and copolymerizations proceed yielding materials with controlled molecular masses, and narrow molecular mass distributions. It is also demonstrated that this protocol is not limited to the use of TFE as a cosolvent and that additional halogenated alcohols, such as 2,2,2-trichloroethanol and 1,1,1,3,3,3-hexafluoroisopropanol are also effective cosolvents for the controlled polymerization of such cationic substrates. Finally, it is demonstrated that the TFE/methylene chloride mixture has no apparent detrimental effect on Grubbs' catalyst.

Glycosidase Inhibition by Multivalent Presentation of Heparan Sulfate Saccharides on Bottlebrush Polymers

“…The solvent polarity issue was then addressed by utilization of weakly coordinating polar 2,2,2-trifluoroethanol (TFE) as part of the cosolvent along with 1,2-dichloroethane (DCE) allowing for an increased ratio without lowering efficacy of the catalyst (Table 1 and Scheme 3). 85 …”

Ru‐Based Olefin Metathesis Catalysts Bearing pH‐Responsive N‐Heterocyclic Carbene (NHC) Ligands: Activity Control via Degree of Protonation

“…Whereas the neutral catalysts exhibited similar or even slightly higher activities in ROMP and ring closing metathesis (RCM) reactions as than their very active, commercially available counterparts 2 and 3 in organic solvents, the catalysts failed to perform ROMP of cationic exo-7-oxanorbornene 6 derivative in acidic protic media (Scheme 1). This is somewhat surprising since the same substrate has been polymerized with Ͼ 95 % conversion in our laboratories with other catalysts at lower loadings in alcoholic/organic [20] and acidic alcoholic/aqueous media, [21] frequently in time periods Ͻ 30 min. We now wish to report our experimental and computational investigation of the influence of the degree of protonation on the ROMP activity of catalysts 4 and 5.…”

Effect of the Halide Counterion in the ROMP of exo‐Benzyl‐[2‐(3,5‐dioxo‐10‐oxa‐4‐aza‐tricyclo[5.2.1.02,6]dec‐8‐en‐4‐yl)ethyl]dimethyl ammonium Bromide/Chloride

“…All chemicals were purchased from the Aldrich Chemical Company and used as received unless stated otherwise. exo ‐Benzyl‐[2‐(3,5‐dioxo‐10‐oxa‐4‐aza‐tricyclo[5.2.1.0 2,6 ]dec‐8‐en‐4‐yl)ethyl]dimethyl ammonium bromide ( MON ‐Bn‐Br), was prepared according to the procedure we recently described 23. The analogous monomer with the chloride counterion was prepared via the direct alkylation of exo ‐4‐(2‐dimethylaminoethyl)‐10‐oxa‐4‐aza‐tricyclo[5.2.1.0 2,6 ]dec‐8‐ene‐3,5‐dione with benzyl chloride according to the same general procedure.…”

“…The analogous monomer with the chloride counterion was prepared via the direct alkylation of exo ‐4‐(2‐dimethylaminoethyl)‐10‐oxa‐4‐aza‐tricyclo[5.2.1.0 2,6 ]dec‐8‐ene‐3,5‐dione with benzyl chloride according to the same general procedure. Polymerizations were conducted under an inert atmosphere with degassed solvents in a PlasLabs nitrogen filled glovebox according to a recently disclosed procedure 23. Polymerization conversions were determined by 1 H NMR spectroscopy via a direct ratio of the vinylic resonances associated with the monomer vs. those of the polymer.…”

“…Recently, we described the synthesis and controlled polymerization of a range of new permanently cationic exo ‐7‐oxanorbornene substrates using RuCl 2 (PCy 3 ) 2 CHPh in a novel 2,2,2‐trifluoroethanol/methylene chloride (TFE/CH 2 Cl 2 ) solvent mixture – other halogenated alcohols such as 2,2,2‐trichloroethanol and 1,1,1,3,3,3‐hexafluoroisopropanol were also shown to be effective as cosolvents with CH 2 Cl 2 23. This study was motivated by the desire to significantly simplify the direct preparation of such permanently cationic polymers via ROMP, i.e., was developed to negate the need for the synthesis of water soluble catalysts for polymerizations conducted under homogeneous aqueous conditions and/or circumventing the need for post‐polymerization modification.…”