1'-binaphthyl 2a was synthesized via acylation of (S)-2-methoxy-2'-pivaloyloxy-1
1'-binaphthyl using AlCl3 as a catalyst.In the presence of triethylamine
HCl was eliminated from 2a to create monomer (S)-6-acrylyl-2-methoxy-2'-pivaloyloxy-1
1'-binaphthyl 3.The monomer 3 was anionically polymerized using n-BuLi as an initiator in toluene.The absolute value of specific optical rotation []58925 of poly-3 is +96 and is about 8 times of that of starting monomer 3.The large increase in magnitude indicates that the optical activity of poly-2 is not solely attributed to the configurational chirality in the side pendant of binaphthyl and suggests that a higher chiral structure
most likely a secondary helical structure
has been formed.Poly-3 was confirmed to exist in the form of one-handed helical structure in solution by means of comparing the specific optical rotation and the CD spectra with that of 3 and the model compounds such as (S)-6-propionyl-2-methoxy-2'-pivaloyloxy-1
1'-binaphthyl 2b and (S)-6-heptanoyl-2-methoxy-2'-pivaloyloxy-1
1'-binaphthyl 2c.This conclusion was also confirmed by the fact that the g value of poly-3 is about 18 times of that of monomer 3.