1H and 13C chemical shift calculations for 12-oxa-pentacyclo[6.2.1.16,9.02,7.02,10]dodeca-4-eno systems using GIAO method at different levels of theory

We present a comparison between the theoretical and experimental 1H and 13C chemical shifts of molecules 1–5. In order to compute the chemical shifts, it was necessary to calculate the geometric parameters for the cited alcohols considering in any case the level of theory used in the chemical shift treatment. Thus, RHF ab initio and DFT with at least 6-31G(d) basis sets were used. The geometry parameters of alcohol 1 compare well with X-ray data. The theoretical chemical shifts were obtained using the GIAO method in association with RHF ab initio and DFT levels of theory with at least 6-31G(d) basis sets. Associations with RHF ab initio geometry and DFT levels of theory for the GIAO calculations were also tested. This data set indicates that there are problems of geometric character in the calculation of the brominated vinylic system. On the other hand, the calculations for the nortricyclenic cycloropane ring are in good agreement with experimental findings. q 2005 Elsevier B.V. All rights reserved.