Intramolecular cyclization of tethered phenyl ketones. Complementary stereochemical results arising from the indium-promoted ring closure of allyl bromides and the fluoride ion-induced desilylation of allylsilanes

Article abstract of DOI:10.1021/jo981683s

The intramolecular indium-promoted cyclization of 4'-substituted (Z)- and (E)-7-bromo-5-heptenophenones has been examined in aqueous tetrahydrofuran. In every instance, ring closure occurred to deliver the syn- 2-vinylcyclopentanol exclusively. The corresponding allylsilanes have been prepared as well, and the course of their fluoride ion-induced cyclization was also studied. In these systems, a kinetic bias for formation of the anti- 2-vinylcyclopentanol is observed, although not with the same exclusivity. Accordingly, complementarity in product diastereoselectivity can be realized in purposeful fashion. The data acquired in this investigation suggest that the indium-catalyzed reactions involve intramolecularly coordinated transition states where development of a cis 5/6-bicyclic framework is most energetically feasible. In contrast, the silanes appear to utilize open- chain antiperiplanar transition states. While the latter are not particularly sensitive to double-bond geometry, they are responsive to steric compression involving the aryl group.