Asymmetric Polymerization of 1-(3-Pyridyl)dibenzosuberyl Methacrylate and Chiral Recognition by the Obtained Optically Active Polymer Having Single-Handed Helical Conformation

Abstract

ABSTRACT:1-(3-Pyridyl)dibenzosuberyl methacrylate was synthesized and polymerized using the complexes of N,N' -diphenylethylenediamine mono lithium amide with ( + )-1-(2-pyrrolidinylmethyl)pyrrolidine, ( + )-2,3-dimethoxy-l ,4-bis( dimethylamino )butane, and ( -)-sparteine in toluene at -78°C. The polymers obtained by the helix-sense-selective anionic polymerization were highly isotactic and exhibited large dextrorotation based on single-handed helical conformation. Free-radical polymerization in toluene with (iso-PrOCOO)z at 40°C and with oc,oc'-azobisisobutyronitrile at 60°C gave nearly perfectly isotactic polymers. The optically active polymer exhibited chiral recognition ability toward trans-stilbene oxide and Troger's base as revealed by chiral adsorption experiments. KEY WORDSSeveral bulky methacrylates with triarymethyl ester groups including triphenylmethyl 1 • 2 and diphenyl-2-pyridylmethyl3·4 esters (TrMA and D2PyMA) are known to give single-handed helical, optically active polymers with highly isotactic main-chain configuration by asymmetric anionic polymerization (helix-sense-selective polymerization). The optically active polymers are valuable as chiral stationary phases for high-performance liquid chromatography (HPLC) and some of them are already commercialized. 6 Among the bulky methacrylates, 1-phenyldibenzosuberyl and 1-(2-pyridyl)dibenzosuberyl methacrylates (PDBSMA and 2PyDBSMA) having 1-aryldibenzosuberyl backbone in ester group are especially intriguing because they exhibit higher durability against solvolysis and higher isotactic specificity even in free-radical polymerization compared with TrMA and D2PyMA, respectively, which are their analogues having a diphenylmethyl group instead of a dibenzosuberyl group. 7 -10 Higher durability against solvolysis is an important property of a monomer because the solvolysis of ester linkages in the helical polymethacrylates leads to a loss of the helical conformation and chiral recognition ability.In this work, we synthesized 1-(3-pyridyl)dibenzosu- beryl methacrylate (3PyDBSMA), a new monomer containing 1-aryldibenzosubery moiety, and examined its durability against solvolysis and polymerization behavior in asymmetric anionic and free-radical catalyses. Diphenyl-3-pyridylmethyl methacrylate (D3PyMA), the parent monomer of 3PyDBSMA with the triarymethyltype side group, has been synthesized and its properties and polymerization behavior have already been reported.11 EXPERIMENT ALMaterials 3-Bromopyridine (Tokyo Chemical Industry) was dried on CaH 2 and distilled under reduced pressure immediately before use. Dibenzosuberone (Aldrich) was used as obtained. Ether and tetrahydrofuran (THF) were distilled over Na wire and stored under nitrogen in the dark. Purification of the other materials including those for anionic polymerization has been shown in the literature. 2 Synthesis of 3PyDBSMA3PyDBSMA was prepared by the method applied for the synthesis of 2PyDBSMA 8 with modifications. 3-Bromopyridine (30 g, 0.190 mol) was added dropwise to a solution of but...

Helix-Sense-Selective Radical Polymerization of N-(Triphenylmethyl)methacrylamides and Properties of the Polymers

“…12 The reaction was monitored by 1 H NMR spectroscopy at 35 C. TrMAM (0.16 g, 0.5 mmol) was dissolved in CDCl 3 (0.5 mL) and the solution was placed in a water bath at 35 C. CD 3 OD (0.5 mL) was added to the solution in the NMR tube, which was immediately placed in the NMR instrument (400 MHz) at 35 C.…”

Helix-Sense-Selective and Enantiomer-Selective Polymerization of a Chiral Methacrylate by Anionic and Free-Radical Mechanisms

“…The method of experiments has been described in our recent paper. 13 Higher durability of ester linkage is an important property of a monomer because solvolysis of helical polymethacrylates leads to a loss of the conformation and chiral recognition ability. A pseudo first-order rate constant (k) of 0.025 h -1 and a half-life period (t 112 ) of 1637min were found for (±)-IDPDMA while k=0.466 h -1 and t 1 2 = 89.0 min have been reported for PDBSMA, indicating that the ester linkage of ( ± )-IDPDMA is more durable than that of PDBSMA.…”

Polymerization of optically active 2-fluorophenyl-4-fluorophenyl-2-pyridylmethyl methacrylate with anionic and radical initiators: Stereospecificity and helix-sense selection

“…Side-chain chirality may have a significant contribution to the spectra shown in Figure 1(C) and (D). Chiral recognition ability of the (ϩ)-and (Ϫ)-polymers obtained by using PMP-DPEDA-Li was examined by chiral adsorption experiment in the same manner as applied for other polymethacrylates, including the single-handed poly(rac2F4F2PyMA) 7 (Table II). Whereas the polymers obtained in the present work failed in resolving Tröger's base, they exhibited better recognition toward trans-stilbene oxide compared with the (Ϫ)-poly(rac-2F4F2PyMA).…”