| Popis: |
Asymmetric inclusion polymerization of the prochiral monomers (E)- and (Z)-2-methyl-1,3-pentadiene (3a and 3b), in apocholic acid (2) canals was performed under various conditions to find out the factors controlling the asymmetric induction during the polymerization. Ozonolysis of the resulting polymers and subsequent transformation of the resulting 2-methyl-4-oxovaleric acid (4) into its 2,4-dinitrophenylhydrazone revealed the predominant formation of the (R)-absolute configuration. The optical yield was high in the initial stage of the polymerization and decreased gradually as the polymerization proceeds. To obtain a high optical yield the polymerization was performed at low temperature applying a 1:1 mole ratio monomer/apocholic acid, and an irradiation dose < 1 Mrad. The optical yield amounted to 36% at maximum, which is the highest value obtained so far in the asymmetric polymerization of 1,3-pentadiene derivatives using canal complexes or other known methods. |
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