Asymmetric polymerization of triphenylmethyl methacrylate by C₂‐chiral catalysts

Abstract

Asymmetric polymerization of triphenylmethyl methacrylate (TrMA) was investigated with optically active anionic catalysts in toluene at −78°C. The catalysts were prepared in various combinations of organolithium compounds with C2‐chiral tertiary diamines (1–6). Tetramethyl‐ethylenediamine derivative bearing an axially dissymmetric biphenyl moiety (1) and the binaphthyl analogue (4) were found to provide efficient catalysts for the preparation of highly isotactic poly(TrMA)s of very large optical rotations whose signs depended on the configurations of the diamines. Especially, the catalysts consisting of 1 gave nearly pure one‐handed helical polymers soluble in tetrahydrofuran (THF) in excellent yields, regardless of the kind of the lithium compounds used. The BuLi‐1 catalyst caused the metallation of toluene used as the solvent, and hence the resulting polymer had a benzyl moiety as an initiator fragment. The polymerization was also discussed with respect to the mole ratio of 1 to BuLi. Circular dichroism (CD) spectra of the (−)‐ and (+)‐polymers, which were obtained with the BuLi‐(R)‐1 and ‐(S)‐1 catalysts, respectively, were virtually complete mirror images of each other. High performance liquid chromatography (HPLC) using the THF–soluble, optically active poly(TrMA) as chiral adsorbent realized the complete resolution of racemic compounds.

Photoinduced Chirality in Thin Films of Achiral Polymer Liquid Crystals Containing Azobenzene Chromophores

“…29 The CD bands at lower wavelength (235 and 215 nm) are due to the electronic absorption of the ester groups of the polymethacrylate. 30,31 Chirality was induced not only for the azobenzene chromophore but also for the nonphotoactive mesogens, which reveals that the cooperative motion effect exists in photoinduced chirality process as well. A relatively low content of the azobenzene chromophore can induce chirality of the nonphotoactive cyanobiphenyl mesogens.…”

Asymmetric Polymerization

“…The large positive optical rotation ([a]60365 -(-770°) of the poly(CHDPMA) obtained with (+)-PMP-DPE-DA-Li changed to a negative value ([a]eo365 ~-480°) in chloroform at 60 °C through a helix-helix transition of the main chain.139 Because the right-and left-handed helices of the poly(CHDPMA) are considered to be diastereomeric taking into account the chiral centers in the vicinity of chain ends as already discussed for poly(D2PyMA), the helix-helix transition may be interpreted as the change from a less stable helix preferentially produced in polymerization at -78 °C into more stable one at 60 °C. complexes of n-BuLi and chiral biphenyl and binaphtyl derivatives [(S)-30a, (S,S)-31]; however, optically active product was not obtained. 104 In addition, we carried out oligomerization of methyl methacrylate with 1-naphthylmagnesium bromide, isolated isotactic oligomers (pentamer and octamer) immediately after termination reaction, and estimated the specific rotation of the optically pure antipodes of the oligomers by HPLC optical resolution with UV and polarimetric detections;142 the values of rotation were [a]25365 26°for the pentamer and 23°for the octamer. On the basis of these and so far described results, we believe that methyl, tert-butyl, and benzyl ester groups are too small to form and maintain helical conformation of a polymethacrylate.…”

“…159 Optically active polyisocyanates are obo R 101 tainable by anionic polymerization of isocyanates with an optically active side group with NaCN. This was done by Goodman and Chen with (+)-2-phenylpropyl isocyanate ( 102 ( 104),-6°(105)] ;this was attributed to a preferred helical conformation. Green and co-workers also reported on polymerization of optically active isocyanate monomers.162 '166 They prepared an optically active polymer from monomer 106 whose configurational chirality arises only from the difference between hydrogen and deuterium.…”

New Chiral Catalyst, t-Butyllithium Complexed with Axially Chiral Diamine, for Asymmetric Polymerizations of Triphenylmethyl Methacrylate and Its 2-Pyridyl Derivative

“…The resulting benzyllithium (BzLi) complexes were found to be excellent catalysts for the polymerization of TrMA. 9 In addition, we examined the asymmetric carbonyl addition of organolithium compounds to aldehydes with the chiral assistance of 1. 11 In the course of the study, it was noticed that n-BuLi complexed with 1 in toluene at -40°C reacted with benzaldehyde to give optically active l-phenyl-1-pentanol in a high yield, while a related complex prepared at room temperature afforded a benzylated ' Determined from GPC charts of the poly(MMA)s derived from the polymers.…”

“…9 Poly(D2PyMA) 9 was isolated after completion of the polymerization. The molecular weight of the THF-soluble part in polymer 9 was lower than that of the insoluble one, but the two were not different in high isotacticity.…”