Abstract
β-Alkoxyalkenyllithiums show potential versatility as precursors of various novel compounds in synthetic organic chemistry. We have described several applications using β-alkoxyalkenyllithiums. One is an α-sulfenyl or α-selenenyl formylation of aldehydes and ketones, which was based on the Wittig-type olefination using β-alkoxyalkenyllithiums. The process is simple and comprises two steps : electrophilic addition of the β-alkoxyalkenyllithium with aldehydes and ketones and hydrolysis of the allylic alcohols. The tandem formylation gave several kinds of photo-sensitive hepta-2, 4, 6-trienals, photo-reactions of which underwent the new tandem cyclization to afford 2-oxa- or 2-aza-bicyclo [3.3.0] octa-3, 7-dienes. On the other hand, β-perfluoroalkyl-β-alkoxy-alkenyllithiums afforded α, β-unsaturated perfluoroalkyl ketones, which are novel precursors in the preparation of fluorine-containing bioactive compounds. Another application is a Lewis acid-promoted C-C bond formation reaction of 2-sulfenyl- or 2-selenenyl-2-allylic alcohols or their acetals with soft nucleophiles, which provided many kinds of products in good to high yields. Furthermore, we have found new allylic cations generated from 2, 3-bis (chalcogene) -substituted allylic alcohols.
