Synthesis and polymerization of racemic and optically active β‐substituted β‐propiolactones. II: β‐monosubstituted and β‐disubstituted monomers and polymers with different optical purities

Abstract

Abstract β‐(trichloromethyl)‐β‐propiolactone (CCl 3 ‐PL), β‐(trifluoromethyl,methyl)‐β‐propiolactone (CF 3 , Me‐PL) and β‐(trifluoromethyl,ethyl)‐β‐propiolactone (CF 3 ,Et‐PL) have been obtained by the reaction of ketene with chloral, 1,1,1‐trifluoroacetone and 1,1,1‐trifluorobutanone, respectively. Chiral catalysis lead to optically active monomers. The enantiomeric excess of the lactones has been measured by 1 H‐NMR spectroscopy, in the presence of 2,2,2‐trifluoro‐1‐(9‐anthryl)ethanol or an europium chiral shift reagent. Polymerizations have been carried out in bulk or in toluene, at 60°C or 80°C, using mainly organometallic initiators. The Polymers become insoluble and crystalline at enantiomeric excesses over 80% for CCl 3 ‐PL and 70% for CF 3 ,Me‐PL. Melting temperatures were recorded from 238 to 268°C for poly(CCl 3 ‐PL) and from 78 to 100°C for poly(CF 3 ,Me‐PL), depending upon the molecular weight and the enantiomeric excess. The 13 C‐NMR specroscopy of poly(CCL 3 ‐PL) indicates that the polymerization of the corresponding lactone leads to polymers of increasing degrees of isotacticity with the enantiomeric excess of the monomer.