Intramolecular Formation of Aryl-Alkyl Bonds

Aryl—alkyl bonds are photochemically formed also in an intramolecular fashion, in most cases through a photostimulated ArSpNl reaction, starting from aryl hahdes bearing a nucleophihc moiety in ortho position to the halogen [4-6], 

The function of electron donor in the initial PET step could be fulfilled by a suitable additive. Thus, l-allyloxy-2-iodobenzene (21), upon photolysis in the presence of l,3-dimethyl-2-phenylbenzimidazoline (DMPBI) as donor in DMF, gave 

A further alternative involved the homolytic cleavage of an aliphatic C(sp )— halide bond, for example in a-chloroacetamides, rather than an aryl C(sp )—halide bond. The radical thus formed was exploited for the synthesis of a potential precursor to vinblastine-type dimeric indole alkaloids such as 20-de-ethylcatharanthine through a radical cyclization step onto an indole skeleton [70]. 

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