1,7-Dithia and 1-oxa-7-thiaspiro[5.5]undecanes. Excellent systems for the study of stereoelectronic effects (anomeric and <i>exo</i>-anomeric effects) in the monothio and the dithioacetal functions

Abstract

1,7-Dithiaspiro[5.5]undecane (2), 1-oxa-7-thiaspiro[5.5]undecane (4), and the tricyclic systems 3, 5, and 6 have been prepared by the acid cyclization of the appropriate ketone dithiol or hydroxy ketone thiol precursors.The configuration and the conformation of the products obtained was determined by 13 C nmr analysis and equilibration studies. The experimental results can be rationalized by taking into account the anomeric and the exo-anomeric effects and the usual steric interactions.