Base Catalysed Rearrangements involving Ylide Intermediates. Part 4. Sigmatropic Rearrangements of 4-Dimethylaminobutenes and Sigmatropic Rearrangements of 3-Dimethylaminohexa-1,5-dienes

Article abstract of DOI:10.1039/P19800001462

The <1,3> sighmatropic rearrangement (11) -> (12) of the 9-dimethylamino-9-(1-phenylallyl)fluorene is a stereoselective process (84:16) at 170 deg C.Analogous <1,3> rearrangements (16) -> (17) of the fluorene derivatives show that the reaction rate is increased by electron donating 9-substituents in the order O^- > NMe2 > OMe.Similar substituent effects are observed for the <3,3> Cope rearrangement (25) -> (26) of hexa-1,5-dienes. 4-Phenyl, 4,4-dimethyl, and 3-dimethylamino substituents are particularly effective in accelerating the rate of the rearrangement (25) -> (26).