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.