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The preparation of highly active manganese and its applications in organic synthesis
Abstract
The preparation of highly active manganese, Rieke manganese (Mn*), by the direct reduction of a manganese salt is described. The Rieke manganese can be easily prepared by reduction of anhydrous manganese halides using lithium in the presence of a catalytic amount of naphthalene in THF at room temperature. Primary, secondary and tertiary alkylmanganese bromides can be generated from the direct oxidative addition of highly active manganese to alkyl bromides. These organomanganese reagents have been found to undergo cross-coupling reaction with acid chlorides to give the corresponding ketones in good yields. In addition, preparation and subsequent cross-coupling reaction of arylmanganese bromides is also performed. The direct formation of 3-thienylmanganese bromides can be readily accomplished under mild conditions from the direct oxidative addition of highly active manganese to thienyl bromides. Interestingly, the reaction of 3,4-dibromothiophene with highly active manganese affords a mono-organometallic intermediate, which upon subsequent treatment with an electrophile provides unsymmetrical disubstituted thiophenes. A facile synthetic route for the direct formation of non-functionalized and functionalized benzylic manganese halides from highly active manganese and benzylic halides was developed. The resulting benzylic manganese halides react readily with a variety of different electrophiles to give the corresponding cross-coupled products in good to excellent yields under mild conditions. For the first time, a new synthetic route to organomanganese tosylates and mesylates has been developed. This can be easily accomplished via the direct oxidative addition of highly active manganese to the corresponding tosylates and mesylates, respectively. The subsequent cross-coupling reaction with several electrophiles was found to proceed in the absence of any transition metal catalyst. Finally, the reductive coupling of carbonyl compounds and imines was achieved by the reaction of highly active manganese. The corresponding coupling products, 1,2-diols and vicinal diamines, were obtained in good isolated yields. Significantly, some functional groups can be tolerated under the conditions used.
Subject Area
Organic chemistry
Recommended Citation
Kim, Seung-Hoi, "The preparation of highly active manganese and its applications in organic synthesis" (1998). ETD collection for University of Nebraska-Lincoln. AAI9917841.
https://digitalcommons.unl.edu/dissertations/AAI9917841