Enantiomer‐selective radical cyclopolymerization of rac‐2,4‐pentanediyl dimethacrylate using a ruthenium‐mediated chiral atom transfer radical polymerization initiating system

Abstract

The enantiomer‐selective radical polymerization of rac‐2,4‐pentanediyl dimethacrylate, an equimolar mixture of (2S,4S)‐2,4‐pentanediyl dimethacrylate (SS‐1) and (2R,4R)‐2,4‐pentanediyl dimethacrylate (RR‐1), was carried out with a chiral atom transfer radical polymerization initiating system consisting of methyl 2‐bromoisobutyrate (3), dichlorotris(triphenylphosphine)ruthenium [RuCl2(PPh3)3], and a chiral additive in anisole at 60 °C. When (S)‐1,1′‐bi‐2‐naphthol (a‐3) was used as the chiral additive, the recovered monomer was enriched in SS‐1, and the enantiomeric excess was 16.9% at a 22.6% monomer conversion. The specific rotation ([α]435, c 0.3, CHCl3) of the resulting polymer was +40.3° at a 22.6% monomer conversion. For the copolymerization of SS‐1 and RR‐1 with 3/RuCl2(PPh3)3/a‐3 in anisole at 60 °C, the monomer reactivity ratio for RR‐1 (rR) was determined to be 4.94, and that for SS‐1 (rS) was 0.27. For the homopolymerizations of SS‐1 and RR‐1 with 3/RuCl2(PPh3)3/a‐3 in anisole at 60 °C, the polymerization rate of RR‐1 was considerably faster than that of SS‐1, and the rate constants for the homopolymerizations were determined to be kSS = 2.0 × 10−3 h−1 and kRR = 8.2 × 10−3 h−1, respectively. With the values of kSS, kRR, rR, and rS, the relative ratio kSS/kRR/kSR/kRS was determined to be 1.2:4.9:4.5:1, which indicated that both the growing end of SS‐1 and that of RR‐1 preferentially reacted with RR‐1. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4563–4569, 2004

Chiral (–)‐DIOP Ruthenium Complexes for Asymmetric Radical Addition and Living Radical Polymerization Reactions

“…[17] Although the proposed mechanism for stereochemical induction to the Ru 2 Cl 4 -[(-)-DIOP] 3 -catalyzed asymmetric radical addition reaction [6] may suggest a possible stereospecific radical polymerization, no tacticity control was reported by other chiral metal catalysts [18][19][20] or chiral radical mediators [21] during the living radical polymerization reactions. At present, stereochemical control during the radical polymerizations should rely on other methods with added Lewis acids or with polar solvents, in which these additives or solvents interact with the polar substituents in the monomer and the growing radical species to induce the steric induction.…”

Comprehensive 2D NMR analysis: Acrylonitrile/ethyl methacrylate copolymers synthesized by ATRP at ambient temperature

“…The formation of polymers with targeted molecular weight along with narrow molecular weight distribution has attracted the attention of many researchers9–16 as well as industries. Since 1995, ATRP has emerged as an effective and versatile technique for the controlled polymerization of wide range of monomers 17–28. Generally, ATRP is carried out at relatively elevated temperatures to obtain effective solubility of the catalyst, especially the deactivating species.…”

Atom transfer radical copolymerizationof acrylonitrile/n‐butyl acrylate: Microstructure determination by two‐dimensional nuclearmagnetic resonance spectroscopy

“…It has been successfully used for the synthesis of a plethora of well‐defined polymeric materials. Many copolymer systems based on methacrylates,12–17 acrylates,18–22 and styrene23, 24 have been synthesized with ATRP. Several research groups have performed the homopolymerization25–29 and block30 copolymerization of acrylonitrile and n ‐butyl acrylate under ATRP conditions.…”