Translocations, homolytic

Beckwith and Storey have developed a tandem translocation and homolytic aromatic substitution sequence en route to spiro-oxindoles [95CC977]. Treatment of the bromoaniline derivative 122 with tin hydride at 160 °C generated the aryl radical 123 which underwent a 1,5-hydrogen atom transfer to give intermediate 124. Intramolecular homolytic aromatic substitution and aromatization gave the spiro-oxindole 125. Intramolecular aryl radical cyclization on to a pyrrole nucleus has been used to prepare spirocyclic heterocycles [95TL6743]. 

The currently accepted chemical mechanism of action of EAL, shown in Figure 17 for the reaction of ( 5)-2-aminopropanol, follows the pattern of other coenzyme Bi2-dependent isomerases. The chemical mechanism begins by homolytic scission of the Co—C5 bond in adenosylcobalamin with the substrate bound at its site translocation of the ribosyl moiety of the 5 -deoxyadenosyl radical by torsion about the ALribosyl linkage to place the 5 -methylene radical in contact with Cl of the substrate, in analogy with DDH ° abstraction of C 1-hydrogen from the substrate by the 5 -deoxyadenosyl radical to form 5 -deoxyadenosine and the... 

S02-extrusion affords the electrophilic radical 49 (Scheme 10). Intramolecular homolytic substitution eventually gives tetrahydronaphthalene 50 (92%). Beckwith showed that the A-(o-bromophenyl)amide 51 can be transformed into the corresponding oxindole 54 (70%) at high temperatures using BusSnH via tandem radical translocation of the initially formed aryl radical 52 to form 53 with subsequent intramolecular homolytic substitution [77]. The nucleophilic a-aminomethyl radical 55 reacted in a tandem addition/homolytic aromatic substitution reaction via radical 56 to tetrahydroquinoline 57 [78]. Radical 55 can either be prepared by oxida-... 

Metabolism of arachidonic acid by COX-2, 15-LO, or oxidation by ROS all lead to the formation of 15(A)-hydroperoxyeicosatetraenoic acid (HPETE). 15(A)-HPETE undergoes homolytic decomposition to form HPNE (Blair, 2008). It is also important to note that 15-LO-derived 13(A)-hydroperoxy-9Z,1 lii-octadecadienoic acid (HPODE) from linoleic acid (LA) also undergoes decomposition to form HPNE (Blair, 2008). A formal loss of water (2-electron oxidation) converts HPNE to ONE, whereas a 2-electron reduction results in the formation of HNE (Blair, 2008). ONO is formed enzymatically from ONE through reduction by aldo-keto reductases (AKRs). ONE is highly reactive, and upon translocation to the nucleus it readily forms HedGuo adducts. ONE... 

Intramolecular Addition/Homolytic Substitution Reactions. o-Bromo-A-methylanilides are converted into oxindoles in good to excellent yields upon treatment with Tri-n-Butylstannane and DTBP (eq 25). The reaction involves the initial formation of an aryl radical, translocation of the radical, and subsequent intramolecular homolytic aromatic substitution. 

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