Design of Metal Artificial Enzymes and the Application to Fine Organic Synthesis

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Alkyl halides, especially iodides and bromides, are frequently utilized as precursors to generate various carbon-centered radicals in organic synthesis. The usefulness of these halo derivatives in radical reactions has been demonstrated in numerous synthetic examples and often reviewed in the chemical literature. There is, however, inevitable drawback to the use of such reactive alkyl halides for radical reactions, and this is mainly due to the troublesome intervention of internal and/or external nucleophiles (e.g., alkoxides, amines, cyanide, enolates, etc.). To overcome this intrinsic problem, we initiated the search for a reactive alkyl iodide equivalent which is stable for ordinary nucleophilic attack. Herein we wish to report that ο-(ο-iodophenyl)phenylthio derivatives are highly effective with various functional group compatibility for rapid generation of carbon radicals under mild conditions. This approach expands the scope of radical chemistry, since a variety of nucleophilic t … More hiolations (thioacetalization, conjugate addition, epoxide opening, etc.) using arythiol can be readily combined with the present radical generation process. In addition to ο-(ο-iodophenyl)phenylthio derivatives, ο-[(E)-2-Trimethylsilyl-2-iodovinyl]phenylthio derivatives have been also introduced as effective precursors for the generation of carbon centered radicals even in the presence of certain nucleophiles ; this provides useful information about the structural requirement for inducing an efficient anchimeric effect under mild conditions.The above mentioned chemistry led us to investigate the possibility of generating desired carbanion species by the utilization of such anchimeric effect. Taking both the versatility and the availability with the limitation of structural types into account, we focused on the combined use of ο-(ο-iodophenyl)phenylselenenyl or tellurenyl derivatives and commercially available alkyllithiums, expecting that various alkyllithium reagents could be efficiently prepared through the initial Li-halogen exchange and subsequent translocation of the resulting anion. The synthetic utility as well as the limitation were evaluated in the in situ trapping reaction with carbonyl compounds. Less