Reaction of β-halo α,β-unsaturated ketons with cuprate reagents. Efficient syntheses of β,β-dialkyl ketones and β-alkyl α,β-unsaturated ketones. A synthesis of (Z)-jasmone

Article abstract of DOI:10.1139/v82-185

Treatment of the 3-halo-2-cyclohexen-1-ones 11-15 and 17 with an excess of lithium dimethylcuprate provided good to excellent yields of the corresponding 3,3-dimethylcyclohexanones 21-24.Similar reactions involving the β-bromo cyclopentenones 19 and 20 stopped at the monoaddition stage, producing the cyclopentenones 40 and 43.Reaction of the β-bromo cyclohexenones 12 and 15 with 1.1 equiv. of lithium dimethylcuprate did not effect clean conversion of these substrates into the corresponding 3-methyl-2-cyclohexen-1-ones.When a series of β-bromo enones 12, 14-19were allowed to react with the lithium (phenylthio)(alkyl)cuprates 44-47, the correspondig β-alkyl enones were, in general, produced cleanly and efficiently.However, reaction of 3-bromo-2-methyl-2-cyclopenten-1-one (19) with the cuprate reagent 44 gave mainly the β-phenylthio enone 49.This undesired result could be avoided by employing, in the place of 19, The β-iodo cyclopentenone 50, which reacted smoothly with 44 to give a high yield of 2,3-dimethyl-2-cyclopenten-1-one (40).Reaction of 3-bromo-2-cyclohexen-1-one (14) with 3 equiv. of the mixed vinylcuprate reagent 48 gave 3-(3-butenyl)-2-cyclohexen-1-one (32).Alkylation of 1,3-cyclopentanedione with (Z)-1-chloro-2-pentene afforded compound 51, which was converted into the β-bromo enone 52.Treatment of the latter substance with lithium dimethylcuprate provided (Z)-jasmone (53).