28017-80-3Relevant academic research and scientific papers
Diastereoselective synthesis of α,β-unsaturated systems
Castelani, Priscila,Comasseto, Jo?o V.
, p. 2319 - 2326 (2007/10/03)
Functionalized Z-vinylic tellurides were used in substitution reactions with lower order cyanocuprates leading to α,β-unsaturated ketones and esters in good yields. In the case of acyclic tellurides, the product was obtained in high diastereoselectivity. The control of the stereoselectivity was achieved by simple change of the reaction temperature.
Superoxide Anion Radical (O2)-radical Mediated Base-Catalyzed Autoxidation of Enones
Frimer, Aryeh A.,Gilinsky-Sharon, Pessia,Aljadeff, Gladis,Gottlieb, Hugo E.,Hameiri-Buch, Judith,et al.
, p. 4853 - 4866 (2007/10/02)
Seventeen variously substituted cyclohex-2-en-1-ones were prepared and reacted with superoxide anion radical (O2-radical generated from KO2/18-crown-6) in inert nonpolar aprotic media at room temperature.The 4,4,6,6-tetrasubstituted cyclohexenones (1b,1c, and 1d) proved to be totally inert,while those cyclohexenones possessing available acidic α'- or γ-hydrogens underwent O2-radical mediated base-catalysed autoxidation (BCA) generating various products depending on the nature and location of the substituents.Thus, 4,4- and 5,5-disubstituted substrates(2b, 2c, 2e, 2f and 3b, 3d, 3f-3i, respectively) gave 2-hydroxycyclohexa-2,5-dien-1-ones (7) as the major product (>80percent yield) upon aqueous acid workup while the corresponding 2-methoxy analogues 8 are obtained when the reaction is quenched with CH3I. 2,3-Epoxycyclohexanones 13 and oxidative cleavage products 11 and 12 are formed in the case of the 6,6-disubstituted systems (4a-4c); these oxidation products are accompanied by dimers 14 when the substituent on 4 is CH3 or H.Epoxide 23 is the primary isolable product in the 3,4,4-trialkyl system (5d).As expected for BCA processes, similar results were observed when these reactions were mediated by KOH (at room temperature) or KOC(CH3)3 (at -40 deg C).In the case of 6,6-diphenylcyclohex-2-en-1-one (4c), however, tert-butoxide-mediated BCA at -40 deg C yielded cyclopentene hydroxy acid 15 in addition to epoxide 13.The saturated analogue of 4c, 18, yielded primarily the corresponding saturated hydroxy acid 19, as well as several other oxidation products (20-22) depending on the reaction conditions.The mechanism of these transformations is rationalized in terms of base-induced reactions and rearrangements of the initially formed keto hydroperoxides.
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
Piers, Edward,Cheng, Kin Fai,Nagakura, Isao
, p. 1256 - 1263 (2007/10/02)
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).
