Bicyclo octene oxidation

Cyclo-octene oxide is known to give largely bicyclo[3,3,0]octan-2-ol on cyclization with lithium diethylamide, but this transannular reaetion may be avoided by using bases such as KOBu -DMSO, which give predominantly cyclo-oct-2-enol ... 

Cylindramide (90) is a cytotoxic compound isolated from Halichondria cylindrata (7.10 s % wet wt.), but very likely of bacterial origin [148]. The structure was deduced from spectroscopic analysis, the relative stereochemistry (only) of the bicyclo[3.3.0]octene unit by NOESY techniques, and the absolute stereochemistry of the amino acid of the tetramic acid ring (25,35) from the recovery of erythtro-L-(3-hydroxyomithine from oxidative degradation of 90. It showed cytotoxicity to B16 melanoma cells (IC50 0.8 (ig/ml). 

Muller and co-workers have demonstrated the potential of coupling several spontaneous chemical steps to biocatalysis in a one-pot domino reaction to form bicyclo[2.2.2]octenes.13 A tyrosinase from mushrooms was immobilized on glass beads with the phenol substrate in a mixture of chloroform and a dienophile under air. Tyrosinase can transform a wide variety of phenols to the corresponding catechol, and the presence of air resulted in spontaneous oxidation to the ortho-quinone (Scheme 21.3). The presence of a dienophile then resulted in a Diels-Alder cycloaddition to form the bicyclo[2.2.2]octene product. Significant yields were achieved with a broad range of phenols and dienophiles. 

The stable radical cation of terthiophene end-capped by bicyclo [2.2.2] octene units has been generated by one-electron oxidation, and its crystal structure determined <2006JA14470>. Dimerization of several one-end-blocked l,3-dithienylbenzo[f]thiophenes by chemical oxidation has been reported <2007TL779>. 

Ally lie oxidation. Cyclohexene is oxidized to cyclohex-2-enyl acetate in 75% yield by the reagent at 70° when catalyzed by potassium bromide (ca. 8 hr.). The reaction is slow in the absence of a catalyst. Norbomene is unreactive, but bicyclo[3.2. l]octene-2 is oxidized rapidly to about an equal mixture of endo- and < xo-bicyclo[3.2.1]oct-3-ene-2-yl acetates. Acyclic olefins or cyclic olefins prone to allylic rearrangement give a complex mixture of allylic acetates. 

Oxidative decarboxylation. Having occasion to prepare a quantity of 1-carbo-ethoxy-A -bicyclo[2.2.2]-octene (8), Grob and co-workers prepared the anhydride (6) by the neat synthesis formulated and investigated the oxidative decarboxylation with lead dioxide according to Doering (see Lead dioxide). Even with the active lead dioxide of Kuhn and Hammer, the reaction proceeded poorly and the yield of (8) was only 30-37%. The Swiss workers then found that the yield can be more... 

Other a,co-disubstituted oligothiophenes such as 31 [24], 32 [103], 33 [104], 34 [105], 35 [106] and 36 [98] were characterized by cyclic voltammetry (Scheme 9.23). In 35, bulky bicyclo[2.2.2]octene substituents were introduced to prevent dimerization. Indeed, all oligomers derived from 35 (n = 0, 1, 2, 4) show stable radical cations and dications. In the case of the hexamer derived from 35 with n = 4, the two first one-electron reversible oxidation waves are nearly coalesced ( ox 0. 19, = 0.28 V vs FC/FC+)... 

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