Compounds with Bridgehead Nitrogen 52 -NMR Spectra and Stereochemistry of the 2-Alkylperhydroimidazolopyridines
In contrast to perhydro-oxazolopyridine and perhydrothiazolopyridine, which adopt equilibria in CDCl3 solution at room temperature containing ca 70percent trans-fused conformers in equilibria with O- or S-inside cis-fused conformers, 2-alkylperhydroimidazolopyridines are found to adopt equilibria containing >98percent trans-fused conformers.Comparison of NMR parameters of 2-methylperhydroimidazolopyridine with those of the two isomers of 1,2-dimethylperhydroimidazolopyridine indicates an equilibrium for the former compound between the two trans-fused conformers, with ca 83percent of that conformation containing a transarrangement of nitrogen lone pairs of electrons.These observations are explained in terms of the generalized anomeric effect.KEY WORDS Perhydroimidazolopyridine Conformational equilibria 1H and 13C NMR
Banting, Lee,Crabb, Trevor A.
p. 696 - 706
(2007/10/02)
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