| Research Abstract |
We have performed the syntheses of the new hepta-2,4,6-trienals using our original methodology, which was based on the Wittig type olefinations using β-alkoxyalkenyl lithiums. A simple process has been shown as follows. It contains two steps, a first is a electrophilic addition of the β-alkoxyalkenyl lithium with aldehydes and ketones, a second is a hydrolysis of the allylic alcohols. We have succeeded the α-sulfenyl-, α-selenenyl and α-cyano formylation of aldehydes and ketones. The tandem formylation gave the photo-sensitive 2,4,6-tris(phenylsulfenyl)-, 4-cyano-2,6-bis(phenylsulfenyl)- and 6-cyano-2,4-bis(phenyl-sulfenyl)hepta-2,4,6-trienals, respectively. Photo-reactions of these trienals underwent the new tandem cyclization to afford the 2-oxa- or 2-aza-bicyclo[3.3.0]octa-3,7-dienes. While, the β-perfluoroalkyl-β-alkoxyalkenyl lithiums with aldehydes and the successive hydrations afforded α,β-unsaturated perfluoroalkyl ketones, which were the novel precursors in the preparations of the fluorine-containing bioactive compounds. However, tandem perfluoroacylations gave the 4,6-bis(perfluoroalkyl)-2H-pyrans, not the 2,4-dienyl ketones. In summary, the several kinds of 2,4,6-heptatrienals we prepared here, are found to be highly-photo-sensitive to give the new bicyclic compounds. In particular, the preparation of the 2-cyanoheptatrienal lead to the direct formation of the oxabicyclic compounds, not the trienals.
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