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[摘要]：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 expts., the sulfur(VI) transfer in the conversion of 1 (I) to 2 (II) is found to be intramol., while the sulfur(VI) transfer in the conversion of 3 (III) to 4 (IV) and the sulfur(II) transfer in the conversion of 5 (V) to 6 (VI) are found to be intermol. 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. |
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