Halides reductive coupling with aromatic

Low-valent nickel complexes of bpy are also efficient electrocatalysts in the reductive coupling reaction of aromatic halides.207 Detailed investigations are in agreement with a reaction mechanism involving the oxidative addition (Equation (40)) of the organic halide to a zero valent complex.208-210 Starting from [Nin(bpy)2(X)2]0 with excess bpy, or from [Nin(bpy)3]2 +, results in the [Ni°(bpy)2]° complex (Equations (37) and (38)). However, the reactive complex is the... 

Reduction of sulfur compounds 4-38 Coupling of aromatic acyl halides, with decarbonylation... 

Reductive coupling, in aprotic solvents, of aromatic hydrocarbons with CO2 has long been known. Reduction of naphthalene in DMF in the presence of COo leads to 1,4-dicarboxy-1,4-dihydronaphthalene ( 50%) [246]. Under similar conditions, phenanthrene gives fra725-9,10-dicarboxy-9,10-dihydrophenanthrene ( 30%) [246]. Carboxylation of aromatic halides can be achieved in aprotic solvents either by using transition metal catalysts or by direct reduction using sacrificial anodes in undivided cells (cf. Chapter 8). 

Intramolecular reductive coupling between the isoquinolinium systems (107) and an attached aromatic halide [Eq. (67)] [308], gives products similar to those obtained by the intramolecular coupling of aromatic halides with other aryl groups (Sec. V.B). 

Addition to cyclic iminium salts has been utilized in alkaloid synthesis. A zinc-promoted reductive coupling reaction of iminium salts and alkyl halides has been reported by Shono et al. (Scheme 8). Evidence delineating the mechanistic course (organozinc addition or electron transfer reaction) of the addition has not been established. In contrast to organolithium or Grignard additions, aromatic halogen and alkoxycarbonyl substituents are compatible with this methodology. The intramolecular version of this reaction has been employed for the synthesis of tricyclic amines (53 equation 9). 

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