Castelló Moncayo, Luis Miguel, Nájera, Carmen, Sansano, Jose M., Larrañaga Agirre, Olatz, Cózar Ruano, Abel de, Cossío Mora, Fernando Pedro
Efficient Diastereo- and Enantioselective Synthesis of exo-Nitroprolinates by 1,3-Dipolar Cycloadditions Catalyzed by Chiral Phosphoramidite⋅Silver(I) Complexes
Advanced Synthesis & Catalysis. 2014, 356(18): 3861-3870. doi:10.1002/adsc.201400563
URI: http://hdl.handle.net/10045/43220
DOI: 10.1002/adsc.201400563
ISSN: 1615-4169 (Print)
Abstract: 
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 α-amino acid-derived imino esters and nitroalkenes affording with high dr the exo-cycloadducts 4,5-trans-2,5-cis-4-nitroprolinates 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.
Keywords:Asymmetric synthesis, Azomethine ylides, Dipolar cycloaddition, Phosphoramidites, Silver
Wiley-VCH Verlag GmbH & Co. KGaA
info:eu-repo/semantics/article