Application of electron spin resonance spectroscopy to problems of structure and conformation. XXVIII. Aliphatic semidiones. XXVI. 1,4-Semidiones in C5-C7 carbocyclic systems

Abstract

Cyclic 1,4-semidiones (radical anions of A2-1,4-diones) have been prepared in the cyclopentane, cyclohexane, and cycloheptane systems and detected by esr spectroscopy. Conformational preference and mobility have been detected in the 1,4-semidiones derived from A8x9-1,5-diketohydrindan and 1,6-diketodecalin systems. Examples of valence isomerization are reported in the preparation of 1,4-semidiones from eucarvone, A3-2-acetoxycaren-5-one, 2.3-benzocyclohept-4-enone, and pentacyclo[6.2.2.027.04.'0.0j.9]dodecane-3,6-dione.

Photoaddition of Aliphatic Ethers to 4-Methyl-1,2,4-triazoline-3,5-dione: Application to the Synthesis of Functionalized Crown Ethers and Mechanism

“…[11] In the conditions described in this paper the anion-radical was obtained by reduction with tert-butoxide in DMSO and identified by comparison with the literature data. [28] It is worth noting that the same spectrum was obtained with KOH in DMSO, i.e. the anion-radical of MTAD may be obtained by electron transfer in the presence of a nucleophile and is stabilised in highly polar solvents such as DMSO.…”

Application of electron spin resonance spectroscopy to studies of valence isomerization. III. Aliphatic semidiones. XXVII. Radical anions derived from bicyclo[4.n.0]alk-3-ene-2,5-diones

“…Synthesis. Diones of structure 9 and 13 were synthesized by addition of diphenylsulfonium ylides to the benzoquinone-cyclopentadiene Diels-Alder adduct12 followed by pyrolysis (Scheme II). The semidiones were synthesized ei-Scheme II RTa 27a R,-R7 = H; aH = 5.48 (H-3,4), 3.01 (H-1,6), 1.65 (H-7a), 0.75 (H-7s) G b R,-R6 = H, R7a = H, R7s = CH3; = 5.50'(H-3,4), 3.12 (H-1.6) , 1.45 (H-7a)G c R,-R6 = H, R7s = H, R7a = CH3; aH = 5.54 (H-3,4), 3.01 (H-1.6) , 0.88 (H-7s), 0.88 (CH3)G d R,-R6 = CH3, R7 = H; <zH = 5.20 (CH3, C-3,4), 0.25 (CH3, C-1.6) , 1.95 (H-7a), 0.87 (H-7s) G e R,,R3 = r-Bu, R4-R7 = ; = 4.90 (H-4), 2.40 (H-6), 1.40 (H-7a), 0.90 (H-7s), 0.20 (6 or 9 hydrogens) G f R,,R4,R6 = H, R3,R7 = CH3; aH = 4.95 (CH3, C-3), 4.68 (H-4), 3.45, 3.15 (H-1,6), 0.82 (CH3-7a) G g R, = D, R4,R6 = H, R3,R7 = CH3; a d = 0.52 (D-l); (CH3, C-3), 4.68 (H-4), 3.15 (H-6), 0.82 (CH3-7a) G h R,,R6 = D, R2 = R3 = R7s = H, R7a = CH3; a D = 0.48 (D-l,6); a H = 5.54 (H-3,4), 0.88 (H-7s; CH3, anti-C-7) G i R,-R6 = H, R7 = CH3; a H = 5.4 (H-3,4), 3.2 (H-1,6), 0.83 (CH3, añti-C-7)G j R3-R4 = benzo, R,,R6,R?…”

“…Treatment of eucarvone (7), for example, with sodium amide followed by the addition of methyl iodide affords the bicyclic ketone We have demonstrated the occurrence of valence isomerization in the processes summarized in Scheme I. [8][9] The spontaneous formation of semidiones from hydroxy ketones in basic solution is well known10 as well as the ability of basic DMSO solutions to reduce by one electron a variety of unsaturated ketones. 11 From the results summarized in Scheme I, it is not possible to state at what oxidation stage (enolate anion, radical anion, dienolate dianion) valence isomerization occurred.…”

“…Thus the syn-7-methyl dione (9) is much more easily reduced than the anti-1methyl dione (10). We thus turned our attention to the effect of time and the extent of reduction on the esr signals observed from 9 and 13. The anti-7-methyl dione in DMF gave during electrolysis a strong esr signal of the anti-semidione free of the syn isomer.…”

“…Journal of the American Chemical Society / 96:23 / November Scheme VI 12 (anti) 9 (syn) t* X Esr Spectra of Bicyclo[4.2.0]octa-2,5-semidiones. Figure 2 gives the esr spectra of bicyclo[4.2.0]octa-2,5-semidione (37a) and the syn,anti-7,8-dimethyl (37b) derivative in DMSO solution.…”