Dynamic Helical Chirality of an Intramolecularly Hydrogen-Bonded Bisoxazoline
- 4 December 2002
- journal article
- research article
- Published by American Chemical Society (ACS) in The Journal of Organic Chemistry
- Vol. 68 (1) , 22-26
- https://doi.org/10.1021/jo026496f
Abstract
The synthesis and conformational properties of 2,6-bis-[2-((4S)-4-methyl-4,5-dihydro-1,3-oxazol-2-yl)phenyl]carbam oylpyridines, 2, have been described. Bisoxazoline 2a was prepared in five steps from 2-nitrobenzoyl chloride in an overall yield of 71%. In contrast to related structures such as 1, bisoxazoline 2a exhibits a highly biased P-type helical conformation in solution and in the solid state. In the crystal lattice, 2a further assembles into a left-handed helical superstructure aligned along the crystallographic c axis. The barrier to helical interconversion, as measured by line-shape analysis of the temperature-dependent 1H NMR spectra of thiobenzyl derivative 2b, was determined to be quite low (ΔG⧧ = 12.3 kcal/mol), indicating the presence of a highly dynamic helical chirality.This publication has 29 references indexed in Scilit:
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