Anionic Rearrangement of 7-Norbornadienol: A 1,3-Sigmatropic Shift
Document Type
Article
Publication Date
3-1-1976
Description
The major factors influencing rearrangement of 7-acetoxynorbornadiene to tropyl derivatives have been elucidated. 7-Acetoxynorbornadiene undergoes saponification to 7-norbornadienol which, in turn, via base catalysis, rearranges rapidly to the tropyl skeleton. Lack of deuterium incorporation in the product when the rearrangement was run in CH3OD seemed to eliminate a “free” carbanion as a mechanistic possibility. Rearrangement of 7-deuterio-7-norbomadienol exclusively to 7-deuteriotropyl oxide clearly demonstrated that the bridge carbon, C-7, migrated intact with its deuterium and oxygen to the final tropyl skeleton. The rearrangement has been rationalized in terms of a 1,3-sigmatropic shift with inversion to a norcaradiene intermediate which in turn undergoes a symmetry-allowed disrotatory ring opening to product. The formation of tropyl products has been rationalized in terms of the proposed mechanism. The relationship of a very low enthalpy of activation (for rearrangement) and a rate acceleration due to oxide formation of 7-norbornadienol is discussed in terms of rearrangement via a 1,3-sigmatropic shift.
Citation Information
Franzus, Boris; Scheinbaum, Monte L.; Waters, Deborah L.; and Bowlin, Harold B.. 1976. Anionic Rearrangement of 7-Norbornadienol: A 1,3-Sigmatropic Shift. Journal of the American Chemical Society. Vol.98(5). 1241-1247. https://doi.org/10.1021/ja00421a031 ISSN: 0002-7863