Electrophilic reactions samarium iodide

A-Benzyl PRT groups. An obvious solution to the conformation problem discussed above is the use of or/Z/u-halobenzyl PRT groups instead of the benzoyl derivatives [117]. Ito [121] and Undheim [122] have demonstrated the synthetic potential of this approach. Under classical tin hydride conditions, excellent yields for the alkylation of amines have been obtained as shown in Scheme 33 (Eq. 33.1) [122]. Starting from a chiral 1,3-oxazolidine, a novel approach for the functionalization of aminoalcohols has been reported [123]. When samarium iodide was used for such reactions, the formation of an organosamarium intermediate at the a-N position was achieved. This corresponds to the metallation of an amine under non-basic conditions. Subsequent reaction of the organosamarium species with electrophiles such as ketones [121, 124, 125[ (Eq. 33.2) and isocyanides [121, 124[ has been reported. 

Organoytterbium chemistry has been developed in the last 20 years, although the development rate is much slower than the other lanthanides like samarium or cerium. Dianionic complexes that are produced from the reaction of ytterbium with diaryl ketones react with various kinds of electrophiles including carbon-heteroatom unsaturated bonds.35 Phenylytterbium iodide, a Grignard-type reagent, is known to have reactivity toward carbon dioxide,36 aldehydes, ketones,37,37 and carboxylic acid derivatives38,3811 to form the corresponding adducts respectively. 

The samarium enolate radicals were also trapped intermolecularly, with formation of new carbon-carbon bonds, by quenching the reactions with suitable electrophiles The occurrence of these tandem rearrangements was possible because the samarium(II) iodide acted as a clean one-electron reductant and also generated the metal enolates. 

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