Structural Effects on Oxygen 17 NMR (Nuclear Magnetic Resonance) Shifts of Cyclic Phosphine Oxides

摘要

The oxygen NMR chemical shifts of a variety of cyclic phosphine oxides were recorded at natural abundance. The shifts proved to be extremely sensitive to structural effects such as ring size and the presence of gamma-interactions. Values were found to cover a 70 ppm range. The most unusual effect was discovered with phosphine oxide groups in the 7-position of the norbornene framework. When the oxygen was anti to the double bond, exceptionally strong deshielding (by as much as 60 ppm) occurred relative to the isomer with syn oxygen. O NMR clearly has value as a structural diagnostic technique with phosphine oxides.