Optically Active Poly(Triphenylmethyl Methacrylate)

Poly[1-methyl-1-(tripehnylmethoxycarbonyl)ethylene]

Submitted by: Y. Okamoto1a and H. Yuki1b Checked by: M. Doherty and T. E. Hogen-Esch 2

1. Procedure

A. Monomer Synthesis Method 1 (Notes 1 and 2)3

Methacrylic acid (200 g, 2.32 mol; Note 3) is placed in a 3-L three-necked flask equipped with a stirrer and a dropping funnel, and cooled in an ice bath. Then, aqueous 28% ammonium hydroxide (141 g, 2.32 mol) is added in the course of ca 30 min. To this solution, 395 g (2.32 mol) of silver nitrate dissolved in 100 mL of water is added with stirring, and the reaction is continued for 2 h. The precipitated silver methacrylate is separated by filtration, washed with cold water, and dried under reduced pressure. The yield is 377 g (84%). This is used for the next step without further purification (Note 4). Silver methacrylate (155 g, 0.80 mol) and dry ether (600 mL) are placed in a 3-L three-necked flask equipped with a reflux condenser, a stirrer, and a dropping funnel, and 187 g (0.67 mol) of triphenylmethyl chloride (Note 5) dissolved in 200 mL of dry ether is added dropwise with stirring at room temperature. After heating the mixture to reflux for 3 h, silver chloride is spearated by filtration. The concentration of the filtrate gives a crude product; 197 g (82%) which is recrystallized from ether and from to give the pure monomer. The yield is 134 g (61%); m.p. 102-103o. The monomer is stored in a refrigerator and recrystallized from hexane just before use.

1 2 Macromolecular Syntheses, Collective Volume 2 Monomer Synthesis Method 24

Triphenylmethyl chloride (50.0 g, 0.179 mol) is dissolved in 400 mL of dry toluene in a 2-L three- necked flask equipped with a reflux condenser, a stirrer, and a three-way stopcock. To the solution, methacrylic acid (16.4 g, 0.189 mol) and triethylamine (42.8 g, 0.423 mol; Note 6) is added with a hypodermic syringe with stirring at room tempearature. After heating the reaction system to 80o with stirring for 3 h, triethylamine hydrochloride is separated by filtration. The concentration of the filtrate gives a crude product; 36.1 g (61%). The crude product is purified in the same manner as described in Method 1 to give the pure monomer.

B. Catalyst5

N,N'-Dipehnylethylenediamine (0.50 g, 2.4 mmol; Note 7) is placed in a 30 mL glass ampule connected to a three-way stopcock through a ground glass joint under dry nitrogen (Note 8) and dissolved in 5 mL of dry toluene (Note 9). To this solution, 2.4 mL of butyllithium (1.0 M) in heptane are added with a syringe. The lithium salt of the amine is produced rapidly as a precipitate. A chiral ligand (-)-(2R, 3R)-dimethoxy-1,4-bis(dimethylamino)butane (0.57 g, 2.8 mmol; Note 10) is added to produce the homogeneous chiral catalyst immediately before use (Note 11).

C. Polymerization5

A 300 mL glass ampule with a ground joint is dried by flaming with a gas burner under vacuum (10-2 - 10-3 torr). In this vessel, 10 g (30.5 mmol) of triphenylmethyl methacrylate which is recrystallized from hexane before use is placed under an atmosphere of nitrogen and the vessel is evacuated to dry the monomer. After filling the vessel with dry nitrogen, it is fitted with a three- way stopcock. Then, 200 mL of dry toluene is added with a syringe. The monomer solution thus obtained is cooled to -78o in a dry-ice-methanol bath and 6.7 mL (1.52 mmol as lithium salt) of the above chiral catalyst solution is added with a syringe. The stopcock is closed and the reaction is continued at -78o. After 2 h, a small amount of methanol is added to terminate the reaction (Note 12), and the polymer is precipitated in methanol (2 L). The resulting polymer is separated with a centrifuge as rapidly as possible to avoid the methanolysis of ester groups and dried at 60o for 25 o several hours. A quantitative yield of polymer is obtained [á]D -300 to -330 ( c 2 g/dL). Th