Efficient Diastereo- and Enantioselective Synthesis of exo-Nitroprolinates by 1,3-Dipolar Cycloadditions Catalyzed by Chiral PhosphoramiditeSilver(I) Complexes

Chiral complexes formed by privileged phosphoramidites and silver triflate or silver benzoate are excellent catalysts for the general 1,3-dipolar cycloaddition between azomethine ylides generated from alpha -amino acid-derived imino esters and nitroalkenes affording with high dr the exo-cycloadducts...

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Bibliographic Details
Published in:Advanced synthesis & catalysis 2014-12, Vol.356 (18), p.3861-3870
Main Authors: Castello, Luis M, Najera, Carmen, Sansano, Jose M, Larranaga, Olatz, deCozar, Abel, Cossio, Fernando P
Format: Article
Language:English
Subjects:
Benzoates
Catalysis
Cycloaddition
Esters
Inhibitors
Mathematical analysis
Silver
Synthesis
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Summary:Chiral complexes formed by privileged phosphoramidites and silver triflate or silver benzoate are excellent catalysts for the general 1,3-dipolar cycloaddition between azomethine ylides generated from alpha -amino acid-derived imino esters and nitroalkenes affording with high dr the exo-cycloadducts 4,5-trans-2,5-cis-4-nitroprolinat es in high ee at room temperature. In general, better results are obtained using silver rather than copper(II) complexes. In many cases the exo-cycloadducts can be obtained in enantiomerically pure form just after simple recrystallization. The mechanism and the justification of the experimentally observed stereodiscrimination of the process are supported by DFT calculations. These enantiomerically enriched exo-nitroprolinates can be used as reagents for the synthesis of nitropiperidines, by ester reduction and ring expansion, which are inhibitors of farnesyltransferase.
ISSN:1615-4150
1615-4169
DOI:10.1002/adsc.201400563