ISSN:
0899-0042
Keywords:
polyphenylacetylene
;
rhodium catalyst
;
chiral discrimination
;
circular dichroism
;
induced circular dichroism
;
absolute configuration
;
helix
;
acid-base
;
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Five phenylacetylenes bearing an amino group such as 4-amino (1), 3-amino (2), 4-N,N-dimethylamino (3), 4-aminomethyl (4), and 4-N,N-diisopropylamino-methyl (5) group on the phenyl group, 4-pyridylacetylene (6), and 2-pyridylacetylene (7) were synthesized and polymerized with [Rh(nbd)Cl]2 (nbd: norbornadiene). Monomer 5 showed the highest polymerizability and afforded quantitatively a fibrous polymer, whereas the other monomers showed lower reactivity and the resulting polymers were powdery. Although most polymers were not soluble in common organic solvents such as tetrahydrofuran (THF), chloroform, acetonitrile, and dimethyl sulfoxide, some polymers were soluble in the presence of carboxylic acids. Among the polyphenylacetylene derivatives, only poly-5 having a stable, highly cis-transoidal stereoregular structure exhibited an induced circular dichroism (ICD) in the UV-visible region, probably due to a prevailing one-handed helical conformation upon complexation with optically active carboxylic and α-hydroxy acids such as mandelic acid, lactic acid, and 2-phenylbutyric acid in THF, the sign of which reflected the absolute configuration of the acids. Therefore, poly-5 can be used as a novel probe for determining the chirality of acids. The α-hydroxy acids of the same configuration gave the same sign in induced Cotton effect in THF. However, carboxylic acids used in the present study showed the opposite signs to those of the α-hydroxy acids when their absolute configurations were same. The magnitude of the ICDs seems to depend on the bulkiness of the α-hydroxy acids. On the contrary, other poly(phenylacetylenes) bearing an amino group and poly(pyridylacetylenes) did not show any ICD in the presence of optically active acids, probably because of either low basicity for the acid-base complexation or low stereoregularity of the polymers. Chirality 9:593-600, 1997. © 1997 Wiley-Liss, Inc.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
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