Electronic and steric effects in arylphosphoramidates and phosphorimidates as monitored by carbon‐13 nuclear magnetic resonance

Abstract

Abstract13C NMR chemical shifts and 13C31P couplings are reported for ten arylphosphoramidates and five arylphoshorimidates. The para‐carbon chemical shifts in the phosphoramidates are interpreted in terms of substantial nitrogen lone pair delocalization into the aromatic ring, a phenomenon which is subject to steric inhibition of resonance. By contrast, in the phosphorimidates the electron release into the phenyl ring is not attenuated by steric congestion. Conformational changes about the arylN bond in all compounds have been monitored by vicinal 31PNC13C couplings.