Superoxide anion radical (O sub 2 sup sm bullet minus ) mediated base-catalyzed autoxidation of enones
- Bar-Ilan Univ., Ramat Gan (Israel)
Seventeen variously substituted cyclohex-2-en-1-ones were prepared and reacted with superoxide anion radical (O{sub 2}{sup {sm bullet}{minus}}, generated from KO{sub 2}/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 {alpha}{prime}- or {gamma}-hydrogens underwent O{sub 2}{sup {sm bullet}{minus}}-mediated base-catalyzed 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 (> 80% yield) upon aqueous acid workup, while the corresponding 2-methoxy analogues 8 are obtained when the reaction is quenched with CH{sub 3}I. 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 CH{sub 3} 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(CH{sub 3}){sub 3} (at -40{degree}C). In the case of 6,6-diphenylcyclohex-2-en-1-one (4c), however, tert-butoxide-mediated BCA at -40{degree}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.
- OSTI ID:
- 7071035
- Journal Information:
- Journal of Organic Chemistry; (USA), Journal Name: Journal of Organic Chemistry; (USA) Vol. 54:20; ISSN JOCEA; ISSN 0022-3263
- Country of Publication:
- United States
- Language:
- English
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400201* -- Chemical & Physicochemical Properties
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Basic Studies
59 BASIC BIOLOGICAL SCIENCES
ANIONS
CHARGED PARTICLES
CHEMICAL REACTIONS
DATA
DATA ANALYSIS
EPOXIDES
EXPERIMENTAL DATA
INFORMATION
IONS
MEASURING INSTRUMENTS
MEASURING METHODS
MEDIUM TEMPERATURE
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
OXIDATION
RADICALS
SUPEROXIDE RADICALS