Transannular sulfur-nitrogen interactions in stereoisomeric 1,5-thiazocine derivatives: An ab initio MO study

摘要

The stereoisomers of 7-acetyl-benzo[b]naphtho[1,8-f,g]thiazocin-8(7H)-one 13-oxide (I) were studied by ab initio MO method at the HF/3-21G level of theory, and the results were compared with those obtained at the semiempirical MO (AMI) level of theory. Of the eight energy-minimum structures optimized by the semiempirical methods two were rather distorted in their molecular geometries. These two structures were annihilated at the ab initio level of theory. The relative order of stability obtained by the two methods was qualitatively the same. Quantitatively, however, the corresponding structures differed somewhat from each other both in their geometry data and relative energy values. Bader-type electron density analysis suggested that the transannular S...N interactions in some stereoisomers of 1,5-thiazocine derivative 1 may be regarded in the vicinity of 10% of a single bond.