Cyclohexanecarbonitriles: assigning configurations at quaternary centers from (13)C NMR CN chemical shifts.
(13)C NMR chemical shifts of the nitrile carbon in cyclohexanecarbonitriles directly correlate with the configuration of the quaternary, nitrile-bearing stereocenter. Comparing (13)C NMR chemical shifts for over 200 cyclohexanecarbonitriles reveals that equatorially oriented nitriles resonate 3.3 ppm downfield, on average, from their axial counterparts. Pairs of axial/equatorial diastereomers varying only at the nitrile-bearing carbon consistently exhibit downfield shifts of delta 0.4-7.2 for the equatorial nitrile carbon, even in angularly substituted decalins and hydrindanes.
Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282-1530, USA. flemingf@duq.edu
Fraser F
FF
Fleming
Guoqing
G
Wei
D003510:Cyclohexanes / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D009570:Nitriles / Q000737:chemistry*; D013237:Stereoisomerism
D003510:Cyclohexanes; D009570:Nitriles