Ab initio calculations of the NMR spectra of [1.1.1]propellane and bicyclo[1.1.1]pentane

Abstract

New high-level ab initio values of all the NMR shielding and spin–spin coupling constants in [1.1.1]propellane and bicyclo[1.1.1]pentane are obtained and compared with previous theoretical results and available experimental data. Electron correlation effects are taken into account and large basis sets suitable for NMR studies are applied. The results for the shielding constants depend primarily on the basis set, while the spin–spin coupling constants, in particular for the carbon–carbon coupling, are very sensitive to electron correlation effects. The computed NMR parameters agree well with the known experimental values, with the exception of the bridgehead–bridgehead carbon coupling constant in [1.1.1]propellane. Our best estimates of this constant differ from the experimental value for a substituted [1.1.1]propellane, and possible explanations of this discrepancy are discussed.