The endocyclic restriction test: The geometries of nucleophilic substitutions at sulfur(VI) and sulfur(II)

Article abstract of DOI:10.1021/jo8016428

(Chemical Equation Presented) The trajectories for nucleophilic substitutions at sulfur(VI) and sulfur(II) have been investigated by the endocyclic restriction test. On the basis of double-labeling experiments, the sulfur(VI) transfer in the conversion of 1 to 2 is found to be intramolecular, while the sulfur(VI) transfer in the conversion of 3 to 4 and the sulfur(II) transfer in the conversion of 5 to 6 are found to be intermolecular. These results are taken to be consistent with transition structures for these sulfur transfer reactions which require a large angle between the entering and leaving group, a geometry analogous to apical group positions in trigonal bipyramidal transition states.