Phenylthio radical catalyzed rearrangement of acetoxyalkenyl epoxides to acetoxyalkenyl cyclopentanols
✍ Scribed by Viresh H. Rawal; Venkat Krishnamurthy
- Book ID
- 104225429
- Publisher
- Elsevier Science
- Year
- 1992
- Tongue
- French
- Weight
- 281 KB
- Volume
- 33
- Category
- Article
- ISSN
- 0040-4039
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✦ Synopsis
Exposure of cyclic aceto~alkenyl epoxides to a catalytic amount of PbS* initiates a tandem radical induced epoxide fragmentation-Ha abstraction-cyclization process that results in a net isomerization to bicyclic enolacetates.
We recently reported a route to cMused bicyclic carbocycles which utilized a tandem radicalmediated epoxide fragmentation-H l abstraction-cyclization process, typified by the example in Equation 1.l The final step in this tandem process is a typical radical cyclization, where the cyclized species abshacts a hydrogen from n-Bu$nH.
Consequently, this sequence suffers from the same drawbacks as other radical processes, in that the fiil radical site is reduced rather than functionalii.2 We were interested in developing a method for carrying out the tandem processes whereby the originally present oxygen unit can be retained in the product. 3 Such products would be useful not only because of the versatility of oxygenated subunits, which allow further synthetic elaboration, but also because this oxygenation pattern is present in some biologically active natural products that are of interest to us. We report here a useful extension of our original work which addresses this issue. We describe a general two-step process for converting epoxyketones into bicyclic compounds, with retention of the oxygen moiety.