Helix‐sense‐selective polymerization of diphenyl‐2‐pyridylmethyl methacrylate with chiral anionic initiators

Abstract

Polymerization of diphenyl-2-pyridylmethyl methacrylate was carried out with the complexes of organolithium compounds with 22 chiral ligands. Helix-sense-selectivity of the polymerization was largely affected by a slight structural difference of chiral ligands. ( + )-(S)-2-( 1-Pyrrolidinylmethy1)pyrrolidine was the most effective ligand in producing a one-handed helical polymer with narrow molecular weight distribution.

Carbon Anionic Chiral Initiators for Asymmetric Anionic Polymerization of Achiral Isocyanates

“…However, very limited optically active initiators with a chiral center have been exploited. They are mainly nitrogen anionic or oxygen anionic species, whereas carbon anionic chiral initiators are rarely reported.…”

Asymmetric Polymerization

“…More than 20 other chiral tertiary diamine ligands have been examined for the helixsense -selective polymerization of 127 to give helical polymers exhibiting unsatisfactory optical rotations within the range of [ α ] 365 − 1170 ° to +1012 ° [177,182 -184] . On the other hand, PMP was found to be the most effective ligand in helix -sense -selective polymerization of 127 , giving the highly isotactic polymers with narrow molecular weight distributions and high optical rotations, as shown in Table 13.1 [182,185] . The pronounced effect of PMP could be explained in terms of the tight and close ligand coordination to a Li cation due to the smaller substituent on the nitrogen atom in PMP (i.e., hydrogen) [182] .…”

“…On the other hand, PMP was found to be the most effective ligand in helix -sense -selective polymerization of 127 , giving the highly isotactic polymers with narrow molecular weight distributions and high optical rotations, as shown in Table 13.1 [182,185] . The pronounced effect of PMP could be explained in terms of the tight and close ligand coordination to a Li cation due to the smaller substituent on the nitrogen atom in PMP (i.e., hydrogen) [182] . The PMP ligand promoted helix -sense -selective polymerization of other monomers containing pyridyl, pyrimidyl, and piperidinyl groups such as 128 [186] , 129 [187] , 130 [188] , 131 [189,190] , 132 [191] , 133 [192] , 134 [193] , 135 [194] , and 136 [195] .…”

Optically active and highly threodiisotactic poly(triphenylmethyl crotonate) with conformational chirality

“…6). Okamoto and his co-workers have reported that optically active poly( D2PyMA) undergoes racemization by the helixhelix transition [16,17]. Using these values, one obtains the activation enthalpy for the helix sense reversal (AH*) as 28.4 kcal/mol from where R represents the gas constant.…”