| Cyclohexane derivatives were synthesized by the intramolecular cyclization of vinyl epoxides with carbanions. This method allowed for the stereoselective construction of three adjacent chiral centers, and provided functionalities for further elaboration to more complicated molecules. Treatment of methyl 2-alkyl-6,7-epoxy-8-nonenoates with base gave 1-alkyl-3-hydroxy-2-vinylcyclohexanecarboxylates which spontaneously lactonized. When cyclopentanone was reacted with 7-bromo-3,4-epoxy-1-heptene in the presence of excess base, and the alkylation and cyclization proceeded in one pot to give 7-hydroxy-6-vinyl-1-spiro (4.5) undecanone, with the carbonyl group trans to the vinyl group. However, if propionitrile was used instead of the ketone, the major compound contained the nitrile group cis to the vinyl group.;This alkylation-cyclization method was applied to the synthesis of a key intermediate for (... |
