An Anionic 3 + 2 Cyclization-Elimination Route to Cyclopentenes

Article abstract of DOI:10.1021/jo00268a028

The formation and reactions of <1-(phenylsulfonyl)-2-(diisopropylcarbamoyl)allyl>lithium (10) are reported.When 10 is allowed to react with olefins bearing an electron-withdrawing group the 4-substituted cyclopent-1-enecarboxamides 11-19 are produced in 22-89percent yields.Methyl-substituted analogues of 10, the allyllithium reagents 23 and 25, react in a similar manner to produce cyclopentenes that have methyl groups in the 2 or 5 positions.The corresponding <2-(dimethylcarbamoyl)allyl>lithium and <2-(phenylcarbamoyl)allyl>lithium reagents also react with electron-deficient olefins to produce the substituted cyclopentenes 28 and 30, which can be hydrolyzed readily to the carboxylic acid 42.The formation of the cyclopentenes occurs in a stepwise fashion by an initial highly regioselective addition to the electron-deficient olefin by the allyllithium reagent followed by a 5-Endo-Trig cyclization and elimination of benzenesulfinate.The allyllithium 10 undergoes polydeuteration on reaction with methanol-O-d and acetone-d6, alkylation with methyl iodide, and addition-dehydratation on reaction with benzaldehyde.