Intramolecular Aromatic Substitutions with Electrophilic -Radicals

Intramolecular Aromatic Substitutions with Electrophilic C-Radicals... 

Compared to the intramolecular aromatic alkylation with nucleophilic radicals, the analogous process with electrophilic radicals is far less common. Citterio carefully studied the Mn(OAc)3-mediated intramolecular homolytic aromatic substitution of various dialkyl malonates [71, 73]. He showed that the reaction is well suited for the formation of 5- (see 45), 6- (see 46) and 7-membered benzanellated rings (see 47). For cyclizations forming a 6-membered ring, high yields were obtained in the alkylation of electron-rich as well as electron-poor arenes. However, the formation of the 7-membered ring occurred only with electron-rich arenes. Cerium(IV) ammo-... 

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-... 

With Mn(OAc)3, generated by oxidation of Mn(OAc)2 as mediator, a tandem reaction consisting of an intermolecular radical addition followed by an intramolecular electrophilic aromatic substitution can be accomplished [Eq. (21b)] [225b]. Further Mn(III)-mediated additions of 1,3-dicarbonyl compound to olefins are shown in Table 11 (numbers 8b,c, and 9a). Mediated by in situ generated Mn(III), methyl dibromoacetate, trichloro-bromomethane, perfluoroctyl iodide, dimethyl bromomalonate, and active methylene compounds have been added via radicals to olefins [225d]. 

---